Virology Part 2

Arenaviruses - Disease Mechanisms - Segmented, Neg Sense

Transmitted from persistently infected rodents (zoonoses) Induction of immune tolerance Viruses infect macrophages and release mediators of cell and vascular damage. Tissue destruction caused by T-cell immunopathology.

Picornaviruses (Characteristic 4)

Tropism (a) Receptor specificity (cell) (b) Organ and tissue specificity

Picornaviruses (Distribution of virus)

Ubiquitous: Poliovirus is nearly eradicated. Enteroviruses: Disease more common in summer. Rhinovirus: Disease more common in early autumn.

Influenza Virus - 1918 Pandemic - Immunity

Uncomplicated Influenza cases recover with the appearance of a robust IgM and IgG antibody response. That response can be quite long lived: Individuals who survived the 1918 Flu as children had detectable antibody titers against the virus at age 100 yrs. Antibody is only protective against reinfection with the same or closely related Flu strains, and the virus has a remarkable capacity to change antigenically through Antigenic Drift and Antigenic Shift.

Togavirus (Characteristics 4)

Use subgenomic mRNA for synthesis of structural polypeptides

Herpesviruses - Scaffolding

VP5 (UL19) with scaffolding proteins (UL26/26,5) -> Scaffold -> assembly around scaffolding proteins -> procapsid -> autoproteolytic cleavage of scaffolding protein -> mature capsid -> encapsidation -> DNA cleavage/packaging proteins.

HIV-1 - Vaccines - Retroviruses

Vaccine? Failure, ideas: Non-progressors Berlin - Replace immune system CCR5 deletion in T cells HGV Induce latent cells to make virus miRNA gene therapy of T-cells Genetic vaccine?

Retrovirus - cDNA Synthesis

Viral RNA genome is shorter and distant from proviral DNA genome. Proviral DNA: LTR: Duplicated U3, R, U5 U3: enhancer and promoter elements U5: Polyadenylation and transcription termination signals. Integrase: Short homology, staggered cuts, ligation, gap filling

Hepadnaviruses - Genome - Retro-like Viruses

Viral genome is a small circular, partly single-stranded DNA/RNA with overlapping reading frames Bound to 5' DNA CAP on 5' RNA/DNA Coding regions are organized into four overlapping reading frames that yield proteins

Hepadnaviruses - Genome - Retro-like Viruses

Viral genome is a small circular, ssDNA/RNA with overlapping reading frames

Poxviruses - New virion assembly and Maturation

Virion assembly is largely characterized by electron microscopy, in combination with assembly- inhibiting drugs and conditional lethal mutant viruses. Recently, also, newer imaging methods. (2) Crescents then engulf "viroplasm" (core proteins) forming Immature virions (spherical), which then develop a dense nucleoprotein mass ("nucleoid") via packaging of pre- processed genomes). (1) 'Crescents': First stage of development; within factories. Contain a border of 'spicules' (visible portion of an external scaffold). A single ER membrane (embellished with virus membrane proteins) flows from ER into the external scaffold. (3) Virus cuts itself, proteolytically, out of the external scaffold and assumes more of a "barrel" shape by EM. Now it is mature (infectious).

Polyomavirus - Components

Virion: VP1, 2, 3 DNA (Viral) Histones: H2A, H2B, H3, H4 Nucleosome: Histones ds DNA

Vaccinia Virus - Interaction - Pox Virus

Virus-host interaction: Poxviruses can defend themselves from host response.... - Poxviruses encode many proteins that are dedicated to host immune evasion. Essential for virus replication; shared by all poxviruses. Non-essential for replication in cell-culture; roles in virus-host interaction and neutralizing host defenses

Slow Virus Disease - Prion Disease

slow virus disease - progressive pathological process caused by a virus or a prion - remains clinically silent for months or years - ends in profound disability or death

Spongiform encephalopathies - Prion Disease

spongiform encephalopathies - fatal neurodegenerative disorders - characterized by dementia, motor dysfunction, and myoclonus

Parvoviruses - Examples - DNA viruses

§ Small, single-stranded DNA viruses; non-enveloped virus particles which package one strand of either minus strand or plus strand DNA § Linear genomic DNA with palindromic sequences at both termini § Some are capable of autonomous replication; others require a helper virus (e.g., adenovirus) § Responsible for a small number of human diseases, including: *Fifth disease - an erythematous illness of early school age children that causes a cutaneous rash and, in adults, joint pain and arthritis-like symptoms. *Transient aplastic crisis - a severe anemia due to an abrupt cessation of red blood cell production

Coronaviruses (Characteristic 4)

Viruses encode sequences for proteolytic enzymes in their genomic RNAs as well as a viral-specific RNA-dependent RNA polymerase

Influenza Therapeutics

Who should take antiviral drugs? It s very important that antiviral drugs be used early to treat flu in people who are very sick with flu (for example people who are in the hospital) and people who are sick with flu and have a greater chance of getting serious flu complications. Other people may also be treated with antiviral drugs by their doctor this season. Most healthy people with flu, however, do not need to be treated with antiviral drugs. What antiviral drugs are recommended this flu season? There are two antiviral drugs recommended by CDC this season. The brand names for these are Tamiflu® and Relenza® (The generic names for these drugs are oseltamivir and zanamivir). Tamiflu® is available as a pill or liquid and Relenza® is a powder that is inhaled. What are the benefits of antiviral drugs? When used for treatment, these drugs can make you feel better and shorten the time you are sick by 1 or 2 days. They can also prevent serious flu complications.

Influenza Virus - 1918 Pandemic - Host Factors

• 1918 H1N1 was likely a new, previously unknown virus and Herd Immunity was low. • Crowding as seen in Military posts and in the disrupted social and economic conditions of Western Europe during World War I promoted rapid spread. • Deaths due to secondary bacterial infections were commonly seen. Antibiotics were not yet available. • Cytokine Storm. Patient tissues examined retrospectively have characteristics of a severe inflammatory response typical of a cytokine storm.

Arenaviridae - Characteristics - Seg, neg sense

• Enveloped virus, round or pleomorphic, 50-300 nm in diameter • Single-stranded genome divided into 2 RNA segments: small (~3.4 kb) and large (~7.1 kb) • 2 genes on each segment, arranged in unique "ambisense" orientation, encoding 5 proteins • Inactivated by: - heating to 56oF - pH<5.5 or >8.5 - UV/gamma irradiation - detergents - Name derived from "arenosus" (Latin "sandy") describing appearance of virions on examination by electron microscopy

Influenza Virus - Factors that led to 1918 pandemic

• Studies in which 1918 Influenza HA and N genes are inserted into the background of a modern Influenza strain show that the 1918 HA renders the virus highly virulent. •The Viral RNA Polymerase also contains mutations which allow replication in the lungs causing primary Pneumonia. •The NS1 gene acts as an interferon antagonist and blocks the antiviral activities of Interferon •(Suppresses Innate Immune Response).

Prion Disease - Symptoms

• dementia is primary symptom •usually accompanied by motor dysfunction • symptoms appear in middle to late life and last from months to years prior to death • produce characteristic spongiform degeneration of brain and deposition of amyloid plaques • Share many characteristics with Alzheimer's disease

Prion Disease - New-Variant CJD

• transmitted from cattle that have bovine spongiform encephalopathy (BSE) or mad cow disease • cattle experimentally infected with BSE have tested positive for prion agent which was found in a variety of tissues - evidence suggests that human vCJD can be acquired by eating meat products such as brain and spinal cord tissue from infected cattle

Vaccinia Virus - Exocytosis @ Cell Surface - Poxviruses

Wrapped virions (WVs) inside the cell fuse w/ plasma membrane from the inside, to release extracellular virus (EV). The outermost membrane is lost during the exocytic exit process, leaving two membranes: The original MV membrane, and the inner wrapping membrane.

Negative-Strand RNA viruses (Characteristics)

a. Enveloped; ss RNA viruses; the genomic RNA is (-) strand polarity, so it does not serve as mRNA (unlike positive strand RNA viruses) b. Isolated virion RNA is not infectious The genomic RNA is present as an RNP (ribonucleoprotein) with helical symmetry within the virion particle c. Virions also contain a virus-encoded enzyme (RNA-dependent RNA polymerase), also called a transcriptase. d. Virion envelope (derived from host cell membrane) contains many copies of one or two (or rarely, three) viral polypeptides (glycoproteins) embedded in the membrane and protruding outside of the particle as spikes. e. These surface glycoproteins are responsible for viral interaction with cell surface receptors.

Negative-strand RNA viruses (Examples)

a. Non-segmented genomes: (1) Rhabdoviruses -> rabies, vesicular stomatitis virus (VSV) (2) Paramyxoviruses -> measles, mumps, parainfluenza, Sendai virus (3) Filoviruses -> Ebola, Marburg b. Segmented genomes: (1) Orthomyxoviruses -> influenza (2) Arenaviruses -> lymphocytic choriomeningitis virus (LCMV), Lassa fever virus. (3) Bunyaviruses -> LaCrosse virus, Uukuniemi, Bunyamwera virus, hantavirus Note: Because negative (-) strand RNA viruses come from a number of virus families, there are differences in details of replication but their overall replication strategies are similar.

Reoviruses (Rotaviruses) - Examples - Double-stranded RNA viruses

a. Reovirus (respiratory enteric orphan virus) b. Human rotavirus c. Colorado tick fever virus

Negative Strand Viruses (Rep Mechanism 1)

a. Specific adsorption of virus to cell. b. Penetration into cell sometimes occurs by fusion of virus membrane with cell (plasma) membrane. Also, some enveloped viruses have been shown to enter the cell by phagocytosis or receptor-mediated endocytosis, apparently without causing any fusion of the viral envelope with plasma membrane. c. After uncoating and release of nucleocapsids into cytoplasm, RNA synthesis begins using the RNA transcriptase enzyme carried within the virion particle.

Polyomaviruses, Papillomaviruses, and Adenoviruses - DNA VIruses - Transcription of Proteins

b. For the latter three viruses, the early to late switch occurs after viral DNA replication begins -> clear cut demarcation. 4. After synthesis of proteins from early mRNAs, viral proteins migrate back to the nucleus where viral DNA synthesis begins to occur. The switch to late gene expression then occurs. 5. Late mRNAs are synthesized in the nucleus, processed and/or spliced; then they are transported to the cytoplasm for translation. Most of the late mRNAs code for the virion structural proteins. 6. The newly-synthesized structural proteins are transported to the nucleus (or nuclear matrix) where assembly of virions takes place.

Reoviruses (Rotaviruses) - (Characteristic 2) - Double-stranded RNA viruses

b. Segmented genome containing 10-12 ds (double strand) RNA unique RNA segments (rotavirus has 11 ds RNA segments; reovirus has 10)

Reoviruses (Rotaviruses) - (Characteristic 3) - Double-stranded RNA viruses

c. Following binding to specific cellular receptors, virus particles are brought into cells by receptor-mediated endocytosis.

Reoviruses (Rotaviruses) - (Characteristic 4) - Double-stranded RNA viruses

d. In endosomal compartments of cell, virions are partially uncoated to produce sub-viral particles.

Picornaviruses (Replicative Cycle 1)

(1) Adsorption to surface of susceptible cells followed by conformational change of capsid structure; the virus then penetrates into the cell and is uncoated. (2)Viral RNA (released in the cell) associates with host ribosomes and begins protein synthesis. (3) Protein synthesis: like all eukaryotic mRNAs, picornavirus RNAs are monocistronic Þ 1 initiation site for protein synthesis per mRNA yielding one primary translation product. However, unlike most host mRNAs, ribosomes bind to picornavirus mRNAs at sites downstream from the 5' terminus to sequences called the internal ribosome entry site (IRES).

Coronaviruses (Examples)

(1) Human: human respiratory coronavirus (HCV-229E), SARS-CoV (2) Animal: infectious bronchitis virus (avian) transmissible gastroenteritis virus (swine), mouse hepatitis virus

Poxviruses - Late Transcripts

(1) Intermediate and late mRNAs are unusual in having a capped 5' poly(A) tract, ~35 nt in length. This is not genome-encoded: (2) Intermediate and late gene transcription appear to terminate randomly at no defined positions, leading to random mRNA 3' ends. Since transcription occurs from both strands of the genome, this can lead to double-stranded RNA hybrids within the cell. How might the cell react to that ?

Poxviruses - Genome Structure and Map.

(1) Inverted terminal repeat regions: 0.7 - 12 kb sequences at each end of the genome are identical but inverted with respect to one another. (2) The extreme ends of the genome are covalently cross-linked. Most of the genes located towards the center of the genome are essential for virus replication and are shared by all viruses. Most of the genes located towards the genome termini are non-essential for replication in cell-culture. - Large deletions can spontaneously occur in these near-terminal regions in cell culture. - The termini mainly encode proteins with roles in the LIVING ANIMAL: In virus-host interaction and neutralizing the host animal defenses

Negative Strand Viruses (Rep Mech 2)

(1) Synthesis of (+) mRNA from virion (-) strands (2) The virion (-) strands serve as template in an RNP form (with associated nucleocapsid proteins covering the RNA). (3) Naked RNA will not serve as template for the transcriptase activity.

Picornaviruses (Replicative Cycle 2)

(4) The primary product of protein synthesis is a giant polyprotein that represents nearly end-to-end translation of viral RNA. (5) This translation product is then proteolytically cleaved to yield mature capsid and non-capsid polypeptides (required for proteolytic cleavage and RNA synthesis). This cleavage is called protein processing and is required for virus growth.

Picornavirus (Replicative Cycle 4)

(6) Second phase of the replication cycle is RNA synthesis. These viruses encode a viral RNA-dependent RNA polymerase to carry out replication of their genomic RNAs. RNA replication occurs through a negative (-) strand RNA intermediate that is copied from genomic RNA in the cytoplasm, following virion uncoating and translation. This negative (-) strand intermediate serves as template for the synthesis of new positive (+) strand viral RNAs. Newly synthesized (+) strand RNAs can either: (1) serve as mRNA for more translation of viral proteins; or (2) associate with capsid proteins and be assembled into new virions.

Negative Strand Viruses (Rep Mech 4 - Orthomyxoviruses - Influenza)

(b) The complete genetic information of the virus is contained within eight, non-identical, single-strand segments of (-) strand RNA; template is RNP, not naked RNA. (i) From six of the segments, one mRNA is transcribed, i.e., each fragment yields 1 mRNA. (ii) Exception: From two of the segments (#7 and #8), two mRNAs are produced as a result of mRNA splicing. (iii) Transcription takes place in nucleus. Viral transcriptase "steals" 5' cap structures from newly-synthesized host mRNAs for each viral mRNA. (iv) After synthesis of mRNAs in nucleus, they are transported out into the cytoplasm of the infected cell to engage in virus-specific protein synthesis. (v) Assembly of nucleocapsids also takes place in the nucleus.

Negative-Strand Viruses (Rep Mech 9)

(h) Budding -> some viruses are very efficient at budding while others are very inefficient. (i) Budding itself does not always hurt the cell but still produces profound changes in the cell membrane. (ii) Inefficient type of budding leads to a large accumulation of viral RNPs in cytoplasm of these cells. (iii) Exception: Bunyaviruses do not appear to bud from the plasma membrane. Rather, they are produced by budding from smooth membrane vesicles associated with the Golgi apparatus in the cell cytoplasm.

Picornaviruses (Enterovirus Mechanisms)

- Enter oropharyngeal or intestinal mucosa - Secretory immunoglobulin A can prevent infection - Spread viremia to target tissues - Serum antibody blocks spread - Virus shed in feces - High asymptomatic infection rate.

Picornaviruses (Rhinovirus Mechanisms)

- Enter upper respiratory tract, where infection is usually limited. - Major factor in asthma exacerbations.

Hepadnaviruses - Hepatitis B viruses - Retro-like viruses

- Hepatitis B viruses, encode polymerase with RT activity - Replication begins in nucleus using RNA pol II, producing 5 mRNAs (containing polyA 3') and a full length pre-genome RNA from circularized viral DNA. - Package the RNA pre-gene template in cytoplasm and use viral gene transcriptase to generate the partially double stranded viral DNA genome. - Hepatitis B virus can cause cirrhosis and lead to hepatocellular carcinoma. - The X protein is a multifunctional oncogene that can initiate hepatocarcinogenesis.

Poxviruses - Attachment

- Occurs via four alternative virus membrane proteins, to glycosaminoglycans (chondroitin sulfate and heparan sulfate proteoglycan) which serve as general "receptors". Virus can induce the plasma membrane to form transient blebs ('filopodia'). Virions tend to attach to the filopodia and rapidly "surf" back along them to the cell body prior to cell entry. Perhaps this occurs via 'retrograde actin flow', where the actin filament is pushed back down the filopodium because actin is polymerized at the pointy-end, but the filament is not anchored.

Vaccinia Virus - Virus Release - Poxvirus

- Some of the externalized virions are found free in the extracellular space (released EV), while most remain adhered to the outside surface of the cell (cell-associated enveloped virus, CEV). - CEV are localized at the tips of motile, actin-containing microvilli ("actin tails") which may enhance the efficiency of their cell-cell spread. At some point membrane #2 (prior slides) may rupture but form a "shroud" or "Mexican hat" holding MV ready to fuse with neighboring cell - MV, CEV and released EV are all similarly infectious. - Externalized virions of some poxviruses (cowpox) become embedded in a protein matrix ('A- type inclusion body' protein), in which they are stable for dissemination in the environment.

Poxviruses - Virus Expression

- Three stages of Vaccinia virus transcription: (1) Early (2) Intermediate (which is post-replicative and therefore a type of late stage) (3) Late (classical late) - followed by the assembly of new virions ("Infectious Particle Formation"). - Replication of the DNA genome occurs 1.5 - 6 hr after infection. - A compete, single round of Vaccinia virus replication may take less than 12 hr.

Prion Diseases

- also called transmissible spongiform encephalopathies (TSEs) - fatal neurodegenerative disorders - prions (protein infectious particles) consist of abnormally folded proteins (PrPsc) which can induce normal forms of protein PrPc to abnormally fold

Negative Strand Viruses (Rep Mech 4 - Bunyaviruses and Arenaviruses)

1) The viral genome is contained within three non-identical RNA segments within virus particles. 2) The complete genetic information is contained within two non-identical RNA segments in virions. (i) For these viruses, transcription occurs in the cytoplasm of infected cells. (ii) mRNAs are capped at their 5' ends but do not appear to contain poly(A) tracts at the 3' ends. 5' cap structures on viral mRNAs are "stolen" from host cell mRNAs in the cytoplasm (i.e., not newly-synthesized) of infected cells. (iii) Novel protein coding strategies for these viruses: Genomic RNAs are "ambisense." This means that although the RNAs are functionally negative stranded in their polarities, they have positive-sense and negative-sense coding capacities.

Adenoviruses - Replication Features - DS DNA

1. Complex splicing patterns 2. The "earliest" RNAs expressed, E1A and E1B are activators of cellular and viral gene expression. 3. PolyA site usage changes with time. This is involved in switch from early to late proteins.

Retrovirus - Replication

1. Entry 2. Uncoating and reverse transcription 3. Nuclear translocation and integration of the cDNA 4. Transcripiton and RNA processing 5. Translationa nd Assembly 6. Budding and maturation.

HIV-1 - Replication - Retroviruses

1. Entry 2. Uncoating and reverse transcription 3. Nuclear translocation and integration of the cDNA 4. Transcription and RNA processing. 5. Translation and assembly. 6. Budding and maturation 7. HIV has nuclear import. 8. LTR is highly restricted.

Paramyxoviruses (Mech) - Neg Strand RNA

1. Enveloped, minus strand, non- segmented RNA 2. Upper respiratory tract diseases 3. Two systemic diseases; measles and mumps

Retrovirus - Genome

1. Genome is + sense RNA, 7-10 kb depending on retrovirus 2. Capped and polyadenylated. 3. Two copies of each gene 4. gag, pol, env - essential genes untranslated terminal sequences (UTR) at 5' and 3'. 5. UTR: Control elements for generating LTR, provirus and synthesis of viral genomes and mRNAS. 6. Integration - Provirus has long terminal repeat seqs (LTR), different from genome.

Picornaviruses (Characteristic 1)

1. Naked (non-enveloped), icosahedral virus with 4 non-identical capsid proteins -> protomers

Retrovirus - cDNA Synthesis Steps

1. Primer - A specific cellular tRNA bound near 5' end of virus RNA acts as a primer. 2. cDNA - U5 and R DNA made. 3. RNase H - part of RT enzyme - degrades RNA strand of RNA/DNA duplex. 4. First cDNA: Short minus strand DNA + primer jumps to other end - R sequences anneal and acts as a primer for copying rest of genome. 5. RNase H - Removes remainder to RNA genome except for PP site which primes plus sense DNA synthesis. 6. Second Jump - PBS ends of partially ds cDNA anneal and synthesis continues in both directions.

Rotavirus - (Mechanism 1) - DS RNA

1. Role of viral protein NSP4: - NSP4 is a non-structural protein involved in rotavirus morphogenesis - intra-peritoneal injection of recombinant NSP4 induced age-dependent diarrhea in mice - proposed that NSP4 acts as an enterotoxin by interacting with a cellular receptor on gut epithelial cells to stimulate a calcium- dependent signal transduction pathway; this results in increased plasma membrane chloride permeability and increased chloride secretion, thereby causing secretory diarrhea

Picornaviruses (Important Aspects)

1. Small RNA viruses. 2. Cause variety of human diseases, including poliomyelitis, common cold, and hepatitis. 3. Exhibit post-translational maturation of viral proteins.

Retrovirus - Gene Proccessing

1. Unspliced full length transcripts exported to cytoplasm and either translated into gag and gag-pol proteins or assembled with nucleocapsid proteins. 2. Some pol II transcripts are spliced to produce env mRNA and other viral genes specific to retroviruses. 3. Final maturation of capsids (cleavage - RT) occurs only following budding and release from infected cells. Stop codon suppression or ribosomal frameshifting - pol. Pol - polyprotein (protease and RT)

Retroviruses - Characteristics

1. Very lare and diversified family 3 groups based on pathogenesis: oncornaviruses: usually benign but sometimes cancer-inducing Lentivurses: Long incubation period, severe disease. Spumaviruses: Foamy appearance, bening dsDNA. 2 groups based on genes: Simple: Genes req for replication only Complex: Additional genes for host regulation 2. Most do not kill. 3. Use host functions to express their genes. RNA genome -> DNA -> integrated DNA copies function like cellular genes to produce more viral genomes. 4. Many oncornaviruses stimulate infected cell replication. Slow, infection apparent.

Negative Strand Viruses (Rep Mech 7 - Ebola, filovirus)

mRNA editing produces two mRNAs from a single genomic coding region, resulting in the synthesis of two viral glycoproteins, SGP and GP. (i) SGP -> secreted glycoprotein -- no membrane anchor; secreted from infected cell -- may interact with immune system and suppress the immune response to the virus; evidence for inhibition of human neutrophil activation -- SGP has not been detected in virion (ii) GP -> glycoprotein -- shares same N-terminal ~300 amino acid residues with SGP -- editing of mRNA during transcription produces a second mRNA with an extended C-terminal open reading frame (which contains a trans-membrane anchor sequence). -- surface glycoprotein in virions

Flavivirus (Characteristics 2)

11 kb single-stranded genomic RNA [(+) strand polarity] with 7mG cap structure at the 5' end but without a 3' poly(A) tract (Note: not all members of this group have a 5' cap structure on their genomic RNAs)

Togavirus (Characteristics 2)

11-12 kb single-stranded genomic RNA [(+) strand polarity] 7mG cap structure at 5' end and poly(A) tract at 3' end; contained within an icosahedral capsid

Human influenza - Pandemics

1889 - Russian influenza H2N2 1900 - Old HK influenza H3N8 1918 - Spanish influenza H1N1 1969 - Hong Kong Influenza H3N2 2009 - new H1N1

Orthomyxovirus - Influenza virus - Pandemic

1918 - 1919 - History's worst pandemic

Adenoviruses - VA RNA - DS DNA

2 short, highly-structured RNA molecules. Polymerase III transcripts Prevents cells from mounting an interferon response which would make neighboring cells resistant to infection (inhibit PKR)

Reoviruses (Rotaviruses) - Epidemiology - Double-stranded RNA viruses

2. Cause respiratory and enteric illnesses of humans and animals; human rotaviruses are estimated to cause > 500,000 childhood deaths annually (worldwide), most of which occur in developing countries.

Adenoviruses - Genes - DS DNA

3 kinetic classes: Immediate early, delayed early, late -> 50 proteins. E1A and E1B: Block Rb and p53, override (terminal) cell block in DNA synthesis. E1B: Inhibits apoptosis (early)

Reoviruses (Rotaviruses) - (Characteristic 1) - Double-stranded RNA viruses

3. Characteristics and features of virus life cycle: a. Naked (non-enveloped) icosahedral virions with double protein capsid shell

Adenoviruses - Genomes - DS DNA

36 kb linear ds DNA Early genes for host and viral transcription control, viral DNA repl. Late genes for virion structure.

Polyomavirus - SV40 Genome

4 functional regions: Control region Early transcription unit Late transcription unit Polyadenylation region

Negative Strand Viruses (Rep Mech 3 - Rhabdoviruses, Paramyxoviruses, Filoviruses)

4) Method of transcription: (a) The entire genetic information for the virus is contained within a single strand of negative-sense (-) RNA. The virion-associated transcriptase transcribes 5 to 7 individual mRNAs (using this RNP as template). (i) Like almost all eukaryotic mRNAs, these mRNAs have a 5' cap structure (7^m G^5'ppp^5'N^m) and a 3' poly(A) tract . (ii) Each of these mRNAs is translated by the cell protein synthesis machinery to yield one viral polypeptide. (iii) RNA synthesis and translation occur in the cytoplasm of the infected cell. (iv) Regulation of the amounts of new viral gene products occurs at the level of abundance of various mRNAs Þ transcriptional control

Orthomyxoviruses and Bunyaviruses - Pathogenesis - Segmented, Negative Strand RNA viruses.

4. Pandemics and pathogenesis: segmented, negative strand RNA viruses. a. Potential for reassortment of genome segments in cells co-infected with two different strains of the same virus (e.g., reassortment of segments of different strains of influenza leads to production of new isolates of influenza that cause pandemics in the population). b. Bunyavirus family includes the genus Hantavirus. Hantaviruses are associated with both severe and mild forms of hemorrhagic fever with renal syndrome (HFRS). In 1993, a novel hantavirus (later called Sin Nombre virus) was found associated with an outbreak of acute respiratory illness in southwestern U.S. (1) >50% mortality rate initially observed in patients infected with this hantavirus. (2) First report of acute hantavirus-associated illness in North America. (3) Hantavirus isolates from other parts of the world (e.g., Korea, China, Europe, Scandinavia) had not been previously associated with severe respiratory illness. (4) Hantavirus isolates in the U.S. are maintained and transmitted in rodent populations (primarily deer mice) as shown by antibodies to virus antigen and/or virus present in rodent excreta. (5) Virus transmission to humans most likely occurs via contact with rodent excreta;

Retrovirus - Genes

5'cap: 4: U5 (PBS): (leader): gag:prot:pol:int:env:(PPT):U3:R:polyAn:3' R (terminal repeat seq, 19-250 bases) and U5 and U3 (75-200 bases each) contain transcriptional control signals for provirus. PBS: Primer binding site (short seq >15 based on cellular tRNA primer that initiates reverse transcription) Leader (50-400 bases) contains genome packaging. Gag:prot:pol:int (Gag-Pol precursor) - synthesis requires codon suppression or ribosomal frameshifting (5% of gag) Prot (protease) - generates pol and int proteins from precursor. Env - Always translated from a spliced mRNA (cryptic ORF) PPT - A short polypurine tract also used for reverse transcription.

Influenza - Orthomyxoviruses - RNAs and mRNA splicing

6 of the 8 flu segments encode a single mRNA and a single polypeptide (PB1, PA, PB2, HA, NP, NA) 2 flu segments encode spliced mRNAs to produce: M1 - matrix protein M2 - ion channel NS1 - non-structural protein; inhibits host immune response and mRNA maturation/nuclear export NS2 - minor virion component; role in viral RNP export from nucleus

Papillomavirus - HPV - Genome - Circular ds DNA virus.

7900 bp All ORFs on same strand LCR: Control Region E proteins: early (basal cell) L proteins: late (keratinocyte: terminal cell) Via differential splicing Large multidomain protein - eliminates need for early functions. Viral mRNAs are made from two promoters and polyadenylation signals. - Early promoter located upstream of E6 gene. - Late promoter located upstream of E1 gene.

HERVs / Human Endogenous Retroviruses - Retroviruses

8% of human genome is derived from sequences similar to retroviruses (w/o v-oncs) HERVs are the remnants of an ancient infection in human germline DNA. Many acquired mutations and deletions over evolution and cannot produce protein now. Contain gag, pol, env. LTRs may still be active and affect gene expression. HERV-W env proteins mediate fusion of trophoblasts required for placenta formation. Primate P53 regulate circuit heavily modified by retroviruses.

Flavivirus (West Nile - Facts)

A mosquito-borne infection with a rapidly expanding geographic distribution. One in 5 infected individuals develops mild febrile illness; 1 in 150 develops meningitis, encephalitis, or both. Advanced age is by far the greatest risk factor for severe neurologic disease, long-term morbidity, and death. Presence of virus-infected birds, onset of meningitis or encephalitis in late summer or early fall, and profound muscle weakness provide important diagnostic clues. IgM antibody capture ELISA testing of cerebrospinal fluid or serum is the most efficient diagnostic method; testing is available through state and local health departments; false-positive results may occur after other flavi- virus infections or vaccinations. Rapid reporting of possible cases to health departments is essential to guide public health control efforts.

Arenaviruses - Fast Facts - Seg, Neg sense

ARENAVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 50 - 300 Yes Helix RNA V ss - 2 5 10 - 14 kb (total) MEMBERS Lassa fever virus, lymphocytic choriomeningitis virus (LCMV) Junin virus, Machupo virus, Pichinde virus

Filoviruses - Disease Mechanisms - Neg Strand RNA - Nonsegmented

Acquired from monkeys or infected humans Replication leads to necrosis in liver, spleen, lymph nodes, and lungs Hemorrhage causes edema and shock.

Retrovirus / DNA virus - Generalizaiton

Activate oncogenes -- Negate tumor suppression genes

SV40 T-Antigen Functions - Polyomavirus - DNA Viruses

Activates cellular DNA/RNA synthesis - overcomes cell cycle, initiates S (nuclear) Blocks apoptosis Binds SV40 ori - initiate viral DNA replication via host system Shuts off early viral transcription Activates late transcription Assists in virion assembly Mostly via regional protein domains.

Herpesviruses - Herpes Simplex Virus Life Cycle - Characteristics

Acute Infection (peripheral tissues) - Shut-off host genes - Viral replication - Cell Death Latency (neurons) - Limited viral gene exp - Perisistence of viral DNA Recurrent infection - Periodic reactivation resulting in shedding of virus.

Alpha Herpesviruses (HSV-1, HSV-2, VZV) - Characteristics

Acute non-fatal disease Wide host range for acute infection Short replication cycle Highly cytopathic in cell culture Tropism for both epithelial and neuronal cells Can become latent in neuron Reactivation causes recurrent disease at same site.

HIV-1 - Phases - Retroviruses

Acute: 10^7 RNA/ml Small set of T cells active, produce virus. Many T cells latent CTLs kill, reduce to set point. Asymptomatic: 10^3-10^5 RNA/ml set point. Dynamic, not latent, HIV 1/2 life 6 hours. Needs 10^10-11 RNA/day, 2X10^9 cells/day. Most cells not HIV infected (bystander death)

Adenoviruses - Therapeutic Vector - DS DNA

Advantages: infects a wide variety of cells, can express genes at hgih levels, fairly easy to manipulate to insert genes. Uses: Gene therapy, cancer therapy. Use of viral proteins: to manipulate cell metabolism.

Vaccinia poxvirus - Cell Exit - Poxviruses

After WV are carried to the periphery on microtubules, they re-organize actin cytoskeleton in order to pass through. Of the three membranes now enclosing the virion: - The outermost of the three membranes is lost during exocytosis [This shows vesicle exocytosis -> This is supposed to be a representation of Virion exocytosis But may not be a crystal clear fig.] - The middle membrane (#2) is lost later, just prior to cell entry in the next round of infection (rupture required to expose entry-fusion complex (EFC)). Its role may be in immune evasion? - The remaining (innermost) membrane has the entry-fusion complex for the entry step of the next cycle, to allow the virus core to enter the cytoplasm and initiate a new MV infection

Picornaviruses (Characteristic 6)

After infection begins, many picornaviruses (e.g., human rhinovirus, coxsackievirus, poliovirus) inhibit host macromolecular synthesis (DNA, RNA, protein) -> only viral gene products are synthesized.

Negative-Strand Viruses (Rep Mech 8)

After several rounds of transcription and translation, there is replication of (+) strand RNAs to yield new (-) virion RNAs. These newly-synthesized (-) strands associate with specific viral proteins to form RNPs that are now ready for packaging into new virus particles. (g) Maturation of the virus begins when newly-synthesized viral glycoproteins begin to be incorporated in the cell plasma membrane in specific patches. Newly synthesized RNPs begin to specifically associate with these patches on the inside of the cell plasma membrane, prior to acquiring their envelope and initiating the budding process.

Retrovirus - C-Onc genes

All genes regulate cell growth directly or indirectly. 1. Growth hormones: Surface detection 2. Growth hormone receptors and other extracellular growth-promoting ligands. 3. G protein transducers of growth signals 4. Protein kinases (Tyr or Ser/Thr specific) that regulate by phosphorylation. 5. Specific TFs turn on / off critical genes (myc, P53). Rb and p53 often targets for DNA tumor viruses. Kill neutrophils.

Reoviruses (Rotaviruses) - (Characteristic 7) - Double-stranded RNA viruses

All steps of the reovirus life cycle (including virion assembly) occur in the cytoplasm of infected cells.

Adenoviruses - DNA Repl - DS DNA

All synthesis is continuous and does not involve Okasaki fragments. Requires 3 viral proteins: Pre-terminal protein DNA polymerase ssDNA binding protein. Repl is primed with 80 kDA precursor terminal protein with covalently bound cytosine Uses virus encoded Pol. Asymmetric: Results in semiconserved new ds DNA and ss remaining (circularizes by ITR).

Herpesviruses - Gene Regulation

Alpha: immediate-early genes - Required the infection started, usually takes over the host cell (introns) - Does not require a cell to be actively replicating. Beta: early genes - required to get virion replication going (host-like; rolling circle) Gamma: Late genes - required for making the structural proteins to build the new virions.

Togaviruses (Examples)

Alphavirus: Sindbis virus, Semliki Forest, Chikungunya Virus, western equinine encephalitis virus. Rubivirus: Rubella virus -> Causative agent of measles.

Togaviruses (Species)

Alphaviruses: Eastern / Western equinine encephalitis virus Chikungunya viruses Rubella Virus

Rotavirus - (Mechanism 2) - DS RNA

Alteration of gastrointestinal enterocyte functions: - rotavirus infection down-regulates the biosynthesis of a key enzyme (dipeptidyl peptidase IV) associated with a brush-border membrane located at the apical surface of enterocytes in the villi of the intestine - reduced levels of this enzyme lead to dramatic reduction in the intestinal absorption of amino acids, thus contributing to diarrhea

Poxviruses - Entry

Alternative cell-entry mechanisms: (1) Virus-induced cell-cell fusion (of vaccinia virus-infected with uninfected cells): Triggered by low pH. EFC Receptor At least six of the 9 - 10 fusion/entry proteins are essential for virus virus-induced cell-cell fusion too. (2) Virion pushed from infected cell into (or even all the way through) neighboring cell on 'actin tails' (more later) After entry, virion rides microtubules deeper into the cell, as far as the nuclear envelope.

HIV-1 - Drugs - Retroviruses

Anti-HIV-1 Drugs: Approved: Nucleoside analog reverse transcriptase (RT/inhibitor) Non-nucleoside analog RT (RT inhibitor) Protease inhibitors T-20 a fusion blocker Integrase inhibitors Drugs: CCR5 blockers.

Influenza Viruses - Antigenic Drift and Shift

Antigenic Drift and Shift • Antigenic Drift - mutational changes in HA and/or N which alter the recognition of Influenza by antibody but do not change its fundamental type. • Antigenic Shift-results when two strains of influenza exchange genes (usually HA or N) and this results in a viable progeny virus of a new type. Strains arising by antigenic shift often result in pandemics. • Eg:H1/N1xH5/N2>>H5/N1

Paramyxovirus - Transcription and Replication

Antigenome RNA <-> Replication (high N) <-> RNA polymerase (L/P) + Genomic RNA <-> Transcription (Low N levels)

Adenoviruses, polyomaviruses, and papillomaviruses - DNA Life Cycle - DNA viruses

Appear to enter the cell by receptor-mediated endocytosis. (1) Then migrate to the nucleus during which time their protein coats are removed. (2) Final uncoating of viral cores (DNA and protein) occurs in the cell nucleus. (3) These cores are thought to enter nucleus through membrane pores or a nuclear pocket. (4) Polyomavirus DNAs (and possibly adenovirus DNAs) associate with cell histone proteins, forming a chromosome-like structure in the nucleus ® it is this form that is actively transcribed.

Herpesviruses - DNA Packaging - DNA Viruses

Assemble nucleoprotein cores in the nucleus; virus acquires its envelope by budding though the nuclear membrane (altered by viral specific glycoproteins) into cytoplasm. Cytomegaloviruses appear to target specific proteins in the inner nuclear membrane to allow exit from the nucleus. From the cytoplasm, virus particles are transported out of the cell via the endoplasmic reticulum and the Golgi apparatus. (1) Final maturation of virus glycoproteins occurs during transit through the cytoplasm. (2) During transit of virus particles through cytoplasm, virions are associated with membranous vesicles. For some, these vesicles fuse with the plasma membrane of the infected cell. (3) Some do not bud from the plasma membrane and may stay cell-associated for long periods of time.

Poxviruses - Early Infection End

At the end of the early phase of infection - The virion core disassembles - Early transcription thereby ceases - The genome is released for DNA replication, and factories expand in size.

Bunyaviruses - Fast Facts - Negative Strand RNA

BUNYAVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 80 - 120 Yes Helix RNA V ss - 3 5 11 - 21 kb (total) MEMBERS Rift Valley fever virus, La Crosse virus, Sin Nombre virus Hantaan virus, California encephalitis virus, Uukuniemi virus

HIV-1 - Binding - Retroviruses

CD4 binding - Gp120 (SU) binds CD4 SU conformational change - CD4 binding exposes the coreceptor binding domain. Coreceptor binding - SU binds to the chemokine receptors which act as coreceptors (CCR5 or CXCR4). GP41 (TM) conformational change - TM extends into target cell membrane. Folds back upon itself to initiate fusion of membranes.

Coronaviruses (Fast Facts)

CORONAVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 80 - 120 Yes Helix RNA IV ss+; 5' cap 3' poly(A) 1 7 27 - 32 kb MEMBERS human respiratory coronavirus, SARS-CoV mouse hepatitis virus, infectious bronchitis virus (avian)

Poxviruses - Entry

Can enter the cell by either neutral or low pH route: Neutral route: Classical membrane fusion. Acid route: Virions can stimulate membrane "blebbing" at the base of the filopodia, leading to endocytosis by retracting blebs. The only endocytic route used by poxviruses is Macropinocytosis ("cell drinking"; = an endocytic pathway with very large vesicles, large enough to engulf a poxvirus). Moreover, the virion mimics an apoptotic body (which are typically phagocytosed), coz virus envelope's outer leaflet has a high phosphatidylserine content, as the apoptotic body does. Vacuole acidification activates some kind of fusion of the virion core with vacuole membrane, via a complex of 9 - 10 membrane proteins in the virion's innermost membrane (the "entry- fusion complex", EFC - more polypeptide chains employed for membrane fusion than with any other virus), followed by entry of core from the vesicle into the cytoplasm.

Adenoviruses - Host Immune Response - DNA Viruses

Can persist in lymphocytes; they also encode viral gene products (E1A protein and VA RNAs) that inhibit the cellular response to a- and b-interferons. Protein E3 protects cells from lysis by cytotoxic T cells and TNF, as a result of down-regulation of MHC class I expression due to the binding of E3 to the peptide binding domain of MHC class I antigens and retention in the ER. b. HSV encodes genes that prevent cellular apoptosis via interaction with Ab and complement; prevents induction of CD8+ cytotoxic T cells. c. EBV produces an IL-10 homologue that blocks synthesis of cytokines like TNF-a. d. CMV blocks cell surface expression of MHC class I antigens.

Papillomaviruses - Cervical Cancer Rates - Circular DNA Viruses.

Cancer of the cervix is the second most common cancer in women worldwide, with about 500 000 new cases and 250 000 deaths each year. Almost 80% of cases occur in low-income countries, where cervical cancer is the most common cancer in women. Virtually all cervical cancer cases (99%) are linked to genital infection with human papillomavirus (HPV), which is the most common viral infection of the genital and reproductive tract.

Human Papillomavirus - Gardasil Vaccine - circular ds DNA Viruses

Causes cervical cancer, cervical adenocarcinoma, vaginal cancer, genital warts, and anal cancer. Gardasil is a sterile preparation for intramuscular injection and contains purified inactive proteins from types 6, 11, 16, and 18. ...

Papilloma Viruses - Facts - Circular DNA Viruses

Causes warts or papillomas Greater than 100 serotypes of human viruses Some spread by non-sexual contact: common skin warts Can be sexually transmitted: genital warts and oral carcinoma Natural replication scheme can require the formation of tumors (warts) as part of the replication cycle. Persistence of virus is consequence of continued replication of virus-infected basal cells (episomal). HPV 16 and 18: Most closely linekd to cervical cancer (91% of women with cervical cancer are found to have defective HPV DNA)

Reoviruses - Cytoplasmic Replication - Double-stranded RNA viruses

Cell-mediated endocytosis -> Uncoating -> release of Core -> viral Protein synthesis -> early Transcription -> Early complexes -> replication -> Late transcription -> viral protein synthesis -> Mature progeny -> release Nucleus is not involved; cytoplasmic replication

Hepadnaviruses - HBV - Retro-like Viruses - Characteristics

Cellular 3.2 kb noncovalent ssDNA genome with partial RNA strand DNA gap is about 1/3 genome Encodes: Pol (5' primer, + ssDNA) Nucleocapsid - C Glycoprotein - S Transcription activating X factor

Retrovirus - Insertional Activation

Chronic transforming (slow-transforming) retrovirus genomes do not contain oncogenes - activate c-oncs by a mechanism known as insertional activation. 1. Can occur if the provirus is integrated upstream of the c-onc gene: read-thru 2. Can also occur when a provirus integrates downstream / upstream of a c-onc seq: enhancer.

Hantaviruses - Transmission - Negative mRNA Viruses

Chronically infected rodent Horizontal transmission of infection by intra-specific aggressive behavior Virus is present in aerosolized excreta, particularly urine Virus also present in throat swab and feces Secondary aerosols, mucous membrane contact, and skin breaches are also sources of infection

SV40 Genome and Genetic Map - Control Region

Control Region Ori, early promoter and enhancer, late promoter. Early promoter - TATA box and enhancer region - transcriptional complex formation Late promoter - no TATA box and mRNA for late genes intiates several places along stretch of nucleotides. Origin of replication - 150 bp, sequence-specific elements.

Picornaviruses (Replication Cycle 5)

Control of this depends upon the concentration of capsid proteins. (a) Early in infection, when the concentration of capsid proteins is low, (+) strand RNAs associate with ribosomes for further rounds of translation. (b) Late in infection, when the concentration of capsid proteins is high, newly synthesized (+) RNAs have a greater chance of associating with capsid proteins and forming progeny virions. (7) Newly-assembled virus particles then rupture cell and are released -> can now infect other cells in a second round of infection; this leads to large amplification of the level of virus.

Flaviviruses (Disease Mechanisms)

Cytolytic Viremia, systemic infection Nonneutralizing antibodies can facilitate infection of monocytes / macrophages via Fc receptors

Poxviruses - Characteristics - DNA Viruses

Defining features: (1) Large, double-stranded, DNA genome (single-segment, linear, 130 - 300 kb in length which is quite large by virus standards). (2) Replicate entirely within cytoplasmic compartment of infected cell. (3) Large, complex virion containing enzymes with roles in mRNA synthesis and modification.

Bunyaviruses - Segmented, Negative Sense RNA

Disease: Transmitted by arthropod bite or rodent Primary viremia, then secondary viremia leads to virus spread to target tissues, including central nervous system, various organs, vascular endothelium Antibody essential for controlling viremia.

Retrovirus - Cis-acting retrovirus

Do not carry oncogenes - Retain all viral genes - Are replication-competent.

Gamma Herpesviruses (EBV, HHV-8) - Characteristics

Do not replicate well in tissue culture maintained as a latent infection. Tropism for lymphoid tissue and epithelial of nasopharynx. Can become latent in B and T cells. Infectious mononucleosis. Tumor-associated: Burkitt lymphoma in Africa, nasopharyngeal carcinoma in Asia, Kaposi's sarcoma in AIDS. Burkitt Lymphoma Tumor.

Papillomavirus - Genes - DNA Viruses

E7 protein - Activates cycle progression E7 and E6 - Disrupts with p53 - Prevents apoptosis and cell cycle arrest. Causes growth of wart in order to propagate DNA.

Epstein-Barr Virus Latency

EBV persists in a circulating subset of resting memory B cells (latency 1). Genome is maintained as a circular multi-copy episome in the nucleus of cells (10-100 copies). Latent Gene Products: ~20% of genome coding capacity -6 EBNAs, 2 LMPs - alternative splicing - coding elements dispersed throughout the genome - cis control elements promoter / enhancer clustered - no homologs of EBV immortalization genes in other HVs.

Adenoviruses - Late Gene Expression - DS DNA

Early DBP shuts off most early genes Change in polyadenylation site usage Late gene products: structural, others required for assembly and release of virus Tripartite leader - shunts ribosome scan eIF4F-CAP binding - inactive via PO4.

Poxviruses - Early gene expression

Early gene expression: Starts immediately after cell entry, during and after ride to the nuclear membrane Virion envelope is lost upon cell entry (this can be mimicked in vitro using mild detergent) -> BUT virion's protein/nucleic acid CORE remains intact and can synthesize and extrude genomic transcripts: Enzymes within the virion core (left) form a complete transcriptional system which can synthesize correctly initiated/terminated, capped and polyadenylated, transcripts of the packaged genome: Following extrusion from the core, the mature transcripts are ready for translation by cytoplamic ribosomes.

Retrovirus - MLV Host Range

Ectropic - Infecting Mouse Xenotropic - Infecting only cells other than mouse (in mouse genome, also chicken) Polytropic/amphitropic - both (wild mouse genome) Receptor-env mediated (reservoir of env's also ERVs in mouse genome)

Herpesviruses - Life Cycle

Encapsidation, Release, Complex membrane, budding

Togavirus (Characteristics 3)

Encode polyproteins that are proteolytically cleaved by viral and host cell proteases; cleavage products of viral polyproteins include: a viral RNA-dependent RNA polymerase and several accessory proteins required for viral RNA replication

Picornaviruses (transmission)

Enteroviruses: Fecal-oral Rhinoviruses: Inhalation of droplets, contact with contaminated hands.

HIV-1 - Glycoproteins - Retroviruses

Entry: Viral glycoproteins: Initial production by a cellular protease into gp41 (TM) and gp120 (SU). GP120 (SU): Interacts with CD4 and chemokine coreceptors (CCR5, CXCR4) Gp41 (TM): Mediates fusion of the viral envelope with the host cell plasma membrane (immune suppressive) Receptor: CD4 (T helper, monocytes, dendritic cells) Co-receptors: CCR5 and CXCR4 (B and a chemokines) - (macrophage / memory-T and naive T cells; CCR5 mutants)

Oncornaviruses and Lentiviruses -Proteins - Retroviruses

Enveloped SU (gp120) and TM (gp41) glycoproteins on surface. GAG: MA under lipid bilayer CA forms capsid core NC associates with genome. Enzymes are packaged: RT Pol: (RT, RNAse H, DNA pol, helicase) protease, integrase.

Togavirus (Characteristics 1)

Enveloped particles with glycoprotein spikes

Coronaviruses (Characteristic 1)

Enveloped virion particles with glycoprotein spikes

Flavivirus (Characteristics 1)

Enveloped virion particles with glycoprotein spikes

Orthomyxoviruses - Influenza Virus - Characteristics

Enveloped, minus strand, segmented RNA - Segmentation allows random assortment in mixed infections - Pandemics approximately every 15 years due to antigenic shift - Yearly epidemics due to antigenic drift - Virus replication sensitive to amantadine and rimantidine (inhibitors

Herpesvirus - Common Properties - DNA Viruses

Enzymology: Encode enzymes for DNA metabolism, DNA synthesis, protein processing / mod. Nuclear Rep: Syn of DNA and capsid assembly occur in nucleus, envelopment occurs in transit through nuclear membrane but also cytoplasm. Cytolytic: Production of infectious progeny virus results in host cell death (epithelial cells) Latency: All herpesviruses have the capacity for latency. Latent genome is circular and only limited genome.

Picornaviruses (examples)

Ex. Poliovirus, coxsackievirus, human rhinovirus, hepatitis A virus, enteric cytopathic human orphan (ECHO) virus, enteric virus.

Filoviruses - Characteristics - Neg Strand RNA. - Nonsegmented

Examples: Ebola and Marburg viruses; causes severe hemorrhagic disease. b. Negative strand RNA, single strand genome (19 kb in length); seven known genes; arranged linearly on the genome (in common with rhabdoviruses and paramyxoviruses). c. Enveloped virions -> U-shaped, 6-shaped, or circular shape; 80 nm in diameter; up to 14,000 nm long (unique) d. Proteins: L: polymerase/transcriptase GP: glycoprotein NP: nucleoprotein VP40: matrix protein VP35: RNA polymerase cofactor; also inhibits the induction of antiviral genes, including interferon b (unique) VP30: minor nucleoprotein VP24: minor matrix protein.

Herpesviruses - Latency-associated Transcript (LAT)

Expressed in productive infection, does not shut off during latency Lat transcript is spliced: yields a stable 2kb intron and 6 miRNAs Function of LAT: RNA inhibition of apoptosis, open chromatin, reactivation? LAT can still establish latency wtih less efficiency and high reactivation.

Influenza - DAPI Results for Sialic Acid Linkages

Expression of of a2,3 and a2,6 sialic acid linkages in human respiratory epithelium. -Red, reaction with MAA lectin, indicating the presence of SAα2,3Gal (avian virus receptor). -Green, reaction with SNA lectin, indicating the presence of SAα2,6Gal (human virus receptor). -Cells counterstained with DAPI.

Adenoviruses - Cell Cycle Arrest - DS DNA

FIGURE 12.2 The action of the p53 protein and the effect of viral oncoproteins that block its action. p53 accumulates and is activated by damage to cellular DNA or aberrant growth signals and functions to protect multicellular organisms against the growth or survival of such damaged cells. One action of p53, as illustrated in this figure, is to cause growth arrest by initiating the transcription of a protein, p21, which binds to a complex of cyclin-CDK (cyclindependent kinase). This complex activates the cell cycle by moving cells from G1 into S phase. When p21 binds this complex it is inactivated, providing a brake on the cell cycle. DNA viral oncoproteins (HPV E6, adenovirus E1B, SV40 large T antigen) bind p53 and interfere with p53-mediated growth arrest, thus removing a critical brake on the cell cycle and contributing to the transformation or immortalization of cells.

Filoviridae (Fast Facts)

FILOVIRIDAE SIZE (nm): 80 x 1000 (variable) ENVELOPED: Yes CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: Helix RNA V ss - 1 7 19 kb MEMBERS Ebola virus, Marburg virus

Herpesviruses - DNA VIruses - Transcription of Proteins

For the former virus, temporal control of early to late functions is associated with three classes of proteins synthesized: Immediate early -> Early -> Late alpha -> beta -> gamma (a) a-proteins are required for synthesis of b-proteins. (b) b-proteins are required for synthesis of g (late) proteins and they also inhibit a-gene expression. (c) g-proteins are virion structural polypeptides. g-protein synthesis requires transcription of viral DNA and replication of viral DNA.

Poxviruses - Crescents becoming spheres

Freeze-etch EM has demonstrated the homeycomb lattice cage (external scaffold made from a single protein, D13) within which each immature virion develops. - D13 may anchor or aid in pinching-off of lipid bilayer edges that would otherwise be unstable. - D13 is shed before the virus leaves the assembly areas, probably via proteolytic processing steps

SV40 T-Antigen - Genes - Polyomavirus - DNA Viruses

Functional and protein-binding: Pol a, Rb, TBP, P300, Topoisomerase I, p53 J domain, DNA binding, ATPase, Transactivation, DNA helicase

HIV-1 - Retroviruses

Gag: Processed to matrix and other core proteins that determine retroviral vore. Pol: Reverse transcriptase, RNase H and integrase functions. Env: Envelope protein, resides in lipid bilayer; determine viral tropism.

Negative Sense RNA viruses - Key Points

General features: •All viruses are enveloped with genomic RNA in a helical RNP •Virions carry viral transcriptase (RNA-dependent RNA polymerase) •Transcription template is an RNP complex •Some virion glycoproteins have special features/activities •Cause many different types of disease Viruses with non-segmented genomes (rhabdoviruses, paramyxo- viruses, filoviruses): •Synthesize multiple mRNAs from one genomic RNA •Some utilize RNA editing to increase coding capacity Viruses with segmented genomes (orthomyxoviruses, bunyaviruses arenaviruses): •Potential for segment re-assortment; disease implications •Unique coding strategies •Influenza has numerous unique features during virus replication

Influenza Viruses - Avian Flu - Pandemic?

H5N1/H7N9 Receptor specificity: • Sialic acid linkage preference of avian versus human influenza viruses • Sialic acid expression in different species Route of Transmission: • Aerosol versus droplet versus contact • Tissue distribution of sialic acid receptors Host adaptation: • Polymerase activity • Optimal temperature for replication Other: • HA stability?

Orthomyxovirus and Paramyxovirus Glycoproteins

HA (or H): Hemagglutinin - binds to cell surface receptors NA (or N): Neuraminidase - removes terminal sialic acid residues from oligosaccharides on cell surface proteins and glycolipids; also, acts on nearby HA proteins in the ER, at the plasma membrane, and on virus particles to prevent progeny virus particles from aggregating. Þ Important for infectivity. In addition, NA may cleave HA from its receptor to facilitate movement of the attached particle to the cell surface. F: Fusion protein - mediates fusion of viral envelope with cell plasma membrane; also mediates cell-to-cell fusion G: Surface glycoprotein - has cell receptor binding activity

Orthomyxoviruses - Influenza virions - Surface Glycoproteins

HA = hemagglutinin -> responsible for attachment of virus to surface of cell. HA is the major surface epitope seen by immune system. HA attaches to cell sialyloglycoproteins or sialyloglycolipids; defines viral specificity/tropism. (2) NA = neuraminidase -> functions to remove receptors from HA, from itself, and from the surface of infected cell. Cleavage of such receptors prevents aggregation and facilitates release of virions from c even through ER and plasma membrane. NA may also help in virion penetration of mucus layer in respiratory tract. NA is mainly thought to function at end of cycle during exit from cell, although it may cleave HA from its receptor to facilitate movement of attached particle to cell surface during exit. NOTE: Point mutations in HA (and to a minor extent, NA) leading to amino acid substitutions are responsible for genetic variation and epidemics.

Herpesvirus - Human - DNA Viruses

HHV-1 Herpes simplex-1 a cold sore/skin lesions HHV-2 Herpes simplex-2 a genital herpes, neonatal infections HHV-3 Varicella-Zoster Virus a chicken pox/shingles HHV-4 Epstein-Barr Virus y infectious mononucleosis, tumors HHV-5 Cytomegalovirus B pneumonia/retinitis congenital HHV-6 Human herpesvirus-6 B HHV-7 Human herpesvirus-7 B roseola infantum / exanthem subitum HHV-8 KSHV y Karposi's sarcoma

Alpha Herpesviruses (HSV-1, HSV-2, VZV) - Pathogenesis and Symptoms

HSV-1: Primary infection of a sensory ganglion -> Cold sores. HSV-2: external genitalia. Varicella-Zoster Virus -> Conjunctivia and Upper respiratory tract -> Primary Lymph Nodes -> Skin and Rash. Herpes Zoster Lesions: Trigeminal Ganglion

Beta Herpesviruses (HCMV, HHV-6, HHV-7) - Characteristics

Harmless acute primary infection Very restricted host range Long replication cycle Grow slowly in cell culture Can become latent in the bone marrow blood (lymphoid) In fetal infections can cause abnormal development HCMV - prevalent silent beta HV (AIDS / transplant / in utero) Congenital Cytomegalo Microcephaly

Poxviruses - Virion Structure

Have among the largest of all the animal virus virions, 200 - 400 nm in longest dimension. - Oval or brick-shaped (depending whether you are a fan of EM or AFM). - Extracellular virion is encapsulated with double lipid bilayer (two envelopes). Intracellular mature virion has three envelopes. - Core: "dumbbell-shaped'' or rounded. - Within the core: Genome and enzymes for mRNA synthesis and maturation. - AFM indicates core is encapsulated with a proteinaceous "coat" - Features called 'lateral bodies' are present flanking the core: Function unknown (may carry immune modulators into the cell?).

Hepadnaviruses - Hepatitis B viral proteins - Retro-like viruses

Hepatitis B virus proteins: - X protein - mplicated in development of hepatocellular carcinoma. - Upregulates: c-src kinase, Ras/raf/MAPK/SAPK, protein kinase C, JAK/Stat patient, NF-kB. - Sequesters tumor suppressor protein p53. - Inhibits apoptosis mediated by Fas, tumor necrosis factor, and others.

Herpesviruses - HV Genome Organization - Characteristics

Herpes Simplex Virus Linear dsDNA Genome - 152 kb Lipid Envelope Tegument. HV have large genomes (up to 235 kbp) and are complex virion proteins. HV are widely separated, transcription, similar in terms of virion structure and genome. HV genomes have a unique long (UL) and unique short (US) region, bounded by inverted repeats. HV genomes also have multiple repeated sequences: genome size for a given virus can vary in different isolates.

Herpesviruses - Key Points

Herpesviruses: Large dsDNA linear genome, circular replication, ubiquitous viruses, nuclear budding. Lytic (productive) and Latent (episomal) stages of lifecycle, reactivation via multiorigins - a, B, y classifications. HSV: Mostly single transcripts with own promoter, few spliced. viral TK (and pol) that can be inhibited (acyclovir) Latency - sensory ganglion: episomal, repressed. a-TIF (VP16, tegument) needed for IE genes LAT - noncoding nuclear RNA, latent neurons. EBV: Lytic in nasopharynx epithelia, latency in B memory cell. 2 latent states: Resting B cells, silent, only EBERS Immortalized B cell - EBNA genes. Cofactors for cancer.

Coronaviruses (Characteristic 5)

High frequency of recombination in cells infected with two different viruses

Adeno-associated Virus - Parvovirus - Gene Therapy - DNA Viruses

Human therapeutic vector because its genome can integrate at only one specific site in the human genome (chromosome 19) Efficient integration: >70% of cells (not genomes) Can be used to deliver genes to cells Advantages: not associated with human disease, high stocks, easy to manipulate, stable single site integration, infects dividing and nondividing cells. Disadvantages: Small genome size limits amount of DNA that can be added to 4.5 kb. In vivo integration?

EBV and Cancer - Herpesviruses

Identified in Burkitt lymphoma tumors In most cancers the viral genome does not interate. Needs cofactors - malaria, diet, infectious - to cause cancer.

Positive Strand RNA virus

Important causative agents of numerous diseases Have genomic RNAs that are the same sense as mRNAs. Can be enveloped or naked. 1. Picornaviruses 2. Togaviruses 3. Flaviviruses 4. Coronaviruses

Picornaviruses (Replicative Cycle 3)

Important features of protein processing: (a) Carried out by viral proteinases that cleave at specific amino acid pairs, leading to specific cleavage products. (b) Autocatalytic cleavage of polyprotein (c) The regulation of the relative amounts of viral proteins occurs at the level of protein processing of precursor polypeptides by viral proteinases -> post-translational regulation. *All other positive strand RNA viruses use proteolytic cleavage of precursor polypeptides during their intracellular replication cycles.

DNA Viruses - Integration and Latency

In addition to a productive life cycle, all of the above viruses have oncogenic potential -> ability to transform cells by integration of viral DNA sequences into host chromosomes. b. Herpesviruses can cause latent infections in which virus growth is normally blocked. No virus can be detected during latent infection (discussed further, below).

Picornaviruses (Polio Vaccinations)

Inactivated Virus, Intramuscular injection, IgG - (Salk) Attenuated Live Virus, Oral, IgG, IgA - (Sabin)

Paramyxoviruses - Respiratory syncytial virus - Disease Mech - Neg Strand RNA

Infects the respiratory tract, does not spread systemically May cause bronchitis, febrile rhinitis, pharyngitis, common cold, or pneumonia Bronchiolitis probably caused by host immune system virus. In newborns, infection may be fatal because narrow airways are blocked by virus-induced pathology Infants are not protected from infection by maternal antibody. Reinfection may occur after a natural infection.

Influenza virus (Disease Mechanisms)

Infects upper and lower respiratory tract Pronounced systemic symptoms by cytokine response to infection Antibodies against hemagglutinin and neuraminidase (HA and NA) are important for protection against infection Recovery depends upon interferon and cell-mediated immune response. Susceptibility to bacterial superinfection due to loss of natural epithelial barriers. HA and NA of influenza A virus undergoes major and minor antigenic changes, leading to new susceptible hosts.

Orthomyxoviruses

Influenza A, B, C Disease: Acute respiratory infection Rapid onset of fever, malaise, sore throat Children may have abdominal pain, otitis media Complications: Primary viral pneumonia Myositis and cardiac involvement Guillain-Barre' syndrome Encephalopathy Encephalitis Reye's syndrome Incubation: 1-2 days

Influenza Diagnostics

Influenza Diagnostics fall into Conventional and Rapid categories: Conventional Tests- These are essential for establishing etiology and tracking infection in the population Viral Culture from Nasopharyngeal swabs is the gold standard method but requires 3-10 days. Immunofluorescence staining, RT-PCR, and Enzyme Immunoassays are faster, but less specific (2-4hrs) Paired acute and convalescent sera can be used to establish a serological diagnosis, but require 2 weeks or more. Rapid Tests- Allow a rapid decision point for the use of antiviral drugs A variety of dipstick and spot tests are marketed to diagnose Flu in 10-15 minutes in the physicians office. These use Nasal aspirates or Swabs to detect the presence of Influenza antigens in the patient. Many of these distinguish between Flu A and B, and the rapid result facilitates the prescription of antivirals.

Vaccine Production - Influenza Viruses

Influenza Vaccine Production is based on the seasonality of Flu. The predominant strains causing human disease are reported from collaborating labs in the Southern Hemisphere and vaccine producers in the Northern Hemisphere use this information to select the strains for the production of the following year s vaccine. Occasionally as was the case in 2009, the selection does not include a potentially problematic strain like H1N1 2009. In that case a vaccine has to be produced rapidly.

Adenoviruses - Repl Cycle - DS DNA

Integrins -> endosome -> virion DNA -> Late mRNAs.

Picornaviruses (Poliomyetis)

Intestine -> Bloodstream - Paralysis -> Viremia -> CNS -> Paralysis

Papillomavirus - Transcriptional Events - circular ds DNA Viruses

Keratinocyte diff. Stratum corneum - Mature virions shed. Granular layers - Mature virions. Upper Spinous Layers - Virion assembly, late capsid L2 and L1, vegetative DNA amp, high levels of early diff-dependent proteins, E4. Lower Spinous Layers - Diff-dependent E6 and E7 proteins Early proteins E1, E2, E4, and E6. Transit amplifying cells - Keratins 1 and 10, frequent cell division - possible alternative site of infection - Immediate early proteins E1, E2, and E5. Basal stem and reserve cells - Occasional division to replenish transit amplifying cells. Keratins 5 and 14 - Primary infection, establishment replication, immediate early proteins E1, E2, and E5. Basement membrane. Dermis - Connective tissue, fibroblasts, lymphocytes, vascular endothelium.

Papillomavirus - HPV - Genomic Map - Circular ds DNA virus.

LCR, - Untranslated region E6 - Oncogene (150 aa) E7 - Oncogene (98 aa) E1 - Episomal maintainence E2 - Replication and translation E4, E5, L2, L1 - Capsid Protein

Prions - Replication

Lacking nucleic acid, prions cannot reproduce, but they replicate by stimulating normal cellular prion protein to refold into a form called PrP scrapie (PrPSc) - named after scrapie, the first TSE* discovered.

Coronaviruses (Characteristic 2)

Large (20-30 kb) genomic RNA [single-strand, (+) polarity] with 7mG cap structure at the 5' end and a 3' poly(A) tract

Herpesviruses - Examples - DNA viruses

Large enveloped virion particles containing an icosahedral capsid; within the capsid is a core which contains the linear, double strand genomic DNA (125-235 kbp for human viruses). Surrounding the capsid (underneath the envelope) in virion particles is a protein layer called the tegument, which contains a number of viral proteins (and viral mRNAs). The capsid and envelope also contain a number of viral-encoded proteins. (1) Herpes simplex virus (HSV 1 and HSV 2); causes mucosal lesions (2) Varicella zoster virus (VZV); causes chicken pox and shingles (3) Epstein-Barr virus (EBV); causes infectious mononucleosis, pharyngitis; strong association with Burkitt's lymphoma and certain nasopharyngeal carcinomas. (4) Cytomegalovirus (CMV); causes intrauterine disease leading to congenital defects (developmental defects and mental retardation); also, CMV causes an infectious mononucleosis-like disease that is usually inapparent. However, CMV infection targets organ systems in immuno-suppressed individuals. (5) Human herpes virus 8 (HHV 8) ® Kaposi's sarcoma-associated herpesvirus

HIV-1 - Essential and accessory regulators - Retroviruses

Latent: NO expression, no NFkb Early, essential: Tat - stimulates RNA synthesis Rev - allows RNA transport Late, regulatory (immuno): all others - 'non-essential'. Latent: Unstimulated memory CD4 T cell. Stimulated T cell: NF-kB expression. Essential, early stimulators: Tat - from 2x spliced RNA, binds RNA (pol II) Rev - from 2x spliced RNA, binds RNA (transp) Late, full RNA - structural genes, RT Accessory immunoregulatory: Vpu, Vif, Vpr, Vpx (Nef).

Adenoviruses - Transformation - DS DNA

Like SV40: Infection of non-permissive cells with some Ads can result in cell transformation and tumor formation (in newborn) Transforming genes: E1A and E1B. Adenovirus DNA may cause obesity?

Reoviruses (Rotaviruses) - (Characteristic 8) - Double-stranded RNA viruses

Like other RNA viruses with segmented genomes, these viruses must overcome problem of getting correct RNA segments into virion particles. Mechanism is unknown but must be fairly efficient because particle to PFU ratio is relatively low (10-200); may occur at the single-stranded RNA level and involve viral-specific RNA binding proteins.

Herpesviruses - Genomic Map

Linear, ~152,000 bp in HSV-1 Circularize upon insertion ~100 transcripts and >70 ORFs Most ORFs are single transcripts with contiguous promoter Few (a,b) viral transcripts are spliced. Three DNA ori's 2-s (bi), 1-l (rc)

SV40 Genome and Genetic Map - Productive Infection

Long Cycle: 72 hours Early: Genome and histone transported to nucleus Pol II mediated transcription of early pre-mRNA Processing into mRNA for t and T Translation to yield t and T proteins T to nucleus: inactivation of p53 and Rb, stimulate DNA synthesis, associate with Ori.

Arenaviruses - Negative Sense RNAs

Lymphocytic choriomeningitis virus - Febrile, flu-like myalgia, meningitis. Lassa Virus - Severe systemic fever, increased vascular permeability, shock. Junin Virus - Argentine hemorrhagic fever: similar to Lassa but extensive bleeding. Machupo virus - Bolivian hemorrhagic fever.

Rhabdoviruses (Negative Strand RNA)

Lyssavirus: Rabies -> Rabies Related viruses of rodents and bats -> Encephalitis Vesiculovirus Vesicular stomatis virus -> Flu-like illness

DNA VIruses - Splicing

Many DNA viruses use splicing of viral mRNAs. Splicing provides use of the same DNA sequence in different coding (reading) frames and allows for multiple uses of the same RNA segment. For herpes simplex virus, there is very little splicing of viral mRNAs, but other herpesviruses (like Epstein-Barr virus) employ extensive mRNA splicing.

Coronaviruses (Characteristic 3)

Many viral proteins are derived from proteolytic cleavage of precursor polyproteins (similar to other positive-strand RNA viruses) while others are synthesized from six to eight unique sub-genomic mRNAs

Filoviruses (Examples) - Negative Strand RNA - Nonsegmented

Marburg Virus - Hemorrhagic Fever Ebola Virus - Hemorrhagic Fever

Vaccinia poxvirus - Enwrapping - Poxviruses

Mature virions (MV) exiting cytoplasmic factories contain a single outer membrane (MVs may now be disseminated by cell lysis or cell-cell fusion). • Some MVs are enwrapped by budding through modified cisternae of endosomes/trans- Golgi network to form wrapped virions (WV) that have two additional membranes. • These two additional membranes are derived from the intermediate compartment between endoplasmic reticulum (ER) and Golgi (ERGIC): (this is known because marker proteins from the TGN and endosomal cisternae are found in purified WV).

Reoviruses (Rotaviruses) - (Characteristic 9) - Double-stranded RNA viruses

Mature virions are released by cell lysis, which may be a slow, incomplete process.

Togaviruses (Disease Mechanisms)

Mechanisms: Cytolytic (minus Rubella) Viremia, systemic infection Antibodies limit virus spread Cell-mediated immunity resolves infection.

Paramyxoviruses (Measles virus) - (Examples) - Neg Strand RNA

Morbiliviruses - Measles viruses - Measles Paramyxoviruses - Parainfluenza virus - Cold, bronchitis, croup Mumps virus - Mumps Pneumoviruses - Respiratory syncytial virus - Bronchiolitis, pneumonia, febrile rhinitis, pharyngitis, common cold

Vaccinia Virus - Membranes - Pox Virus

Morphogenesis starting with scaffolding-crescents that fill with the inner envelope derived from the ER. During transit to the cell periphery, mature virus buds through a golgi stack, picking up two additional envelopes. Intracellular virions harvested by breaking cells therefore have a triple envelope. As part of the natural mechanism of cell exit, the outer of the three membranes fuses with the plasma membrane and is therefore lost. Extracellular virions harvested from outside of cells therefore have two envelopes. The outer one (#2) is quite smooth and shields the virion from host defenses, the inner one has the entry-fusion proteins and other virion membrane proteins. #2 may morph into a "Mexican hat" if the virion is 'CEV', ie. remains attached at the plasma membrane. One route of cell EV entry is macropinocytosis, in which the virus enters the cell, engulfed by a large vesicle. The EV-derived virus escapes the vesicle and into the cytoplasm via an acid-triggered mechanism in which the outer of the two envelopes (the 'wrapper') opens into a "Mexican hat" that is is pushed aside, so that the inner one fuses with the vesicle membrane and the virion core is dropped into the cytoplasm.

Hantavirus Pulmonary Syndrome -Clinical Presentation

Most Frequent: Fever Myalgia Nausea/Vomiting Cough Other: Dizziness Arthralgia Shortness of Breath (late in the course of disease) Rare: Rhinorrhea Sore Throat

Polyomaviruses - Examples - DNA Viruses

Murine Polyoma Virus - Ubiquitous, can cause tumors SV40 Virus - Contaminant in African Green Monkey cultures used for poliovirus. - Vaccinated patients got large doses of SV40 without ill effects. - Used to study carcinogenesis - Leads to identification of tumor suppressor cell growth and division.

Caliciviruses (Characteristics)

NO envelope YES polypeptide YES subgenomic mRNAs - 1

Adenoviruses - Examples - DNA viruses

Naked, icosahedral viruses with double strand, linear DNA genome (~ 35 kbp); associated with upper respiratory illnesses, conjunctivitis, and some infantile gastroenteritis

Papillomaviruses - Examples - DNA viruses

Naked, icosahedral viruses with ds circular genomic DNA (~ 8 kbp) (1) Human papilloma virus (HPV) (a) HPV is found associated with epithelial and proliferative lesions that usually remain benign. (b) Causative association of HPV with cervical carcinoma and genital warts. (2) Bovine and rabbit viruses as well (3) Virus not normally found in dividing cells; usually found in outer keratinized tissue

Hantaviruses - Characteristics - Negative mRNA Viruses

No arthropod vector established Unique among genera of Bunyaviridae - Rodent hosts (e.g., deer mouse, cotton rat) Genus and possibly species specific - Transmission: Aerosolization of rodent excreta

Herpes Simplex Virus - Latency

No infectious virus Limited viral transcripts (no mRNA): Latency Associated Transcript (LAT) is RNA species that is abundantly transcribed. LAT can function as a marker of late neuronal cells. LAT can encode 6 miRNAs - antisense ICP0, inhibits apoptosis. HSV encodes more than 140 miRNAs (ICP0)

Negative-Strand Viruses

Non-segmented Genomes: Rhabdoviruses Paramyxoviruses Filoviruses Segmented Genomes: Orthomyxoviruses Bunyaviruses Arenaviruses

Retrovirus - Nuclear import and integration

Nuclear import: Viral preintegration complex enters. Integration: 3 step process. 1. Integrase (IN) trims 2 NTs from 3' ends of genome 2. IN cleaves host cell DNA (open chromatin) and joins retrovirus host 5' ends 3. Host DNA repair machinery fixes gaps and nicks.

Orthomyxoviruses - Influenza - Fast Facts

ORTHOMYXOVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 80 - 120 Yes Helix RNA V ss - 8 10 13 - 14 kb (total) MEMBERS influenza virus A, B, and C

Retrovirus - Genomic Map

Oncornaviruses: 1. ALV and MLV have simple genoe cause tumors in animals but do so endogenous in rodents (HERV C) 2. RSV and MMTV are "rapid transforming" (cause tumors rapidly contain an additional gene, a v-oncogene) gene. Endogenous in rodents (HERV K) 3. HTLV encodes additional activator proteins (tax and rex) that stimulate cell division and metabolic activity (slow transforming) Lentivirus: 1. HIV encodes several additional genes (vif, tat, rev, nef, vpr, vpu) via a complex splicing pattern - regulate HIV replication during latent phase.

Orthomyxovirus and Paramyxovirus glycoproteins (Examples)

Orthomyxoviruses: Influenza: HA, NA Paramyxoviruses: Sendai: F, HN Measles: F, H RSV: F, G

Reovirus (Rotavirus) - Double strand RNA virus - Examples

Orthoreovirus - Orbivirus / coltivirus: Mild upper respiratory tract disease, gastroenteritis, biliary atresia. Colorado tick fever: febrile disease, headache, myalgia (zoonosis) Rotavirus - Gastroenteritis

Polyomaviruses, papillomaviruses, and adenoviruses - DNA Packaging - DNA viruses

Package their DNA into capsids. (1) Polyomaviruses also package cellular histone proteins associated with their viral DNA. (2) These viruses do not have known cell lysis functions; however, adenoviruses encode a proteinase that cleaves a polypeptide associated with cellular intermediate filaments. This cleavage event, coupled with the activity of another adenovirus protein, may facilitate lysis and virion release. Also, SV40 virions may be released via their association with cellular membrane vesicles or stay cell-associated until cell death.

Papillomaviruses - Sites of Infection - Circular ds DNA Viruses

Papillomaviruses cause skin and mucosal lesions Soles of feet, hands, oral, arms, forehead, trunk, genitals, larynx, and nasal cavity source of warts.

Picornaviruses (symptoms)

Paralytic disease, encephalitis, meningitis, cancer, respiratory tract infections, undifferentiated fever, carditis, diarrhea, gastrointestinal disease

Picornaviruses (At risk or risk factors)

Poliovirus Young Children Older Children, Adults Coxackievirus, enterovirus Rhinovirus

Picornaviruses (Vaccines or Antiviral drugs)

Poliovirus: Live oral or inactivated polio vaccines No vaccines for other enteroviruses or rhinoviruses No antiviral drugs

Polyomaviruses - Key Points - DNA Viruses

Polyoma: SV40 Early and late transcription: alternative promoter and splicing T-Ag and t-Ag: Master DNA/RNA regulators via binding domains: inactivation of p53 and Rb. Normally life-long episomal persistence. Transformation resulting from nonproductive abortive infection, T-Ag integration.

HIV-1 - Diversity - Retroviruses

Power of HIV diversity Each cell is a mixed infection Each virion is also a mixture Every progeny may differ What is target? HAART.

Poxviruses - Therapeutic Uses

Poxviruses - Homologous recombination Genome as artificial recombination. Oncolytic poxviruses: Viruses targeted to a tumor can kill it. Recombinant virus has been engineered to lack the thymidine kinase gene: Tumor cell has high levels of TK to promote rapid, uncontrolled cell division (match made in heaven?). This virus (named JX-594) also has GM-CSF gene inserted artificially ..

Poxviruses - Inactivation of Immune System

Poxviruses - Secreted where they bind and neutralize complement factors, interferons, cytokines, chemokines. Complement inactivation: - Secreted, soluble cytokine receptors ('Molecular decoys') - Intracellular (Molecular decoys and inhibitors) - Other

Vaccinia poxvirus - Enwrapping Example - Poxviruses

Precise wrapping mechanism not know, but I like to imagine it like this: Sticking-out membranous stack of golgi, floating around like a big dollop of air bag Virion moving along microtubule on fixed trajectory collides with end of golgi stack. The golgi portion sticks to and wraps around the virion as the virion moves past, then gets torn off, like cotton candy, after which the wrapper heals into two concentric envelopes around the virus, and the golgi also heals.

Herpesviruses - Common Replication Features - Characteristics

Primary infection - Virus replicates moderate to high levels; mild symptomatic fairly rapidly resolved Developed effective immunity 1 or more cell types can maintain viral DNA without the presence of infectious virus. Reactivated infection is usually milder and can pass on to naive host, infected individual is the reservoir

Influenza Virus - 1918 Pandemic - Host Factors

Proposed Anatomy of a Cytokine Storm: A cytokine storm, or hyper-cytokinemia is a potentially fatal immune reaction consisting of a positive feedback loop between cytokines and immune cells, with highly elevated levels of various cytokines.

Flavivirus (Characteristic 3)

Protein products are produced by proteolytic cleavage of a viral polyprotein; these viruses utilize virus-encoded and cellular proteinases, and they encode a viral RNA-dependent RNA polymerase.

Paramyxoviruses - Proteins - Neg Strand RNA

Proteins -> MW -> Function L (Large) -> >150 K -> Replication and Transcription NP -> 40 K -> Nucleoprotein M -> 60 K -> Matrix Protein HN -> 70 K -> Hemagglutinin Neuraminidase F -> 55 K -> Fusion Protein P -> 47 K -> Transcriptase Subunit HN -> Outer proteins F -> Fusion Bound to Genomic RNA: N: Nucleocapsid L: Polymerase P: Phosphoprotein SH: Small hydrophobic M: Matrix

HIV-1 - Co-receptors: R5 and X4 - Retroviruses

R5 strains of HIV: Use CC-chemokine receptor (CCR5) is found on dendritic cells, activated T cells. R5 virus predominate in early infection and mucosal membranes (sexual intercourse) X4 strains: Use CXCR4 as a coreceptor. Eliminates T-cell immunity and rapidly progresses.

Reovirus - Double-stranded RNA - Fast Facts

REOVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 65 - 85 No Icosahedral RNA III ds 10 - 12 11 - 12 16 - 27 kb (total) MEMBERS reovirus, rotavirus, Colorado tick fever virus

Rhabdoviruses (Mech) - Neg Strand RNA

RHABDOVIRIDAE SIZE (nm): 180 x 75 ENVELOPED: Yes CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: Helix RNA V ss - 1 5 11 - 16 kb MEMBERS rabies virus, vesicular stomatitis virus (VSV), Chandipura virus

Structures of Neuramidase Inhibitors - Influenza Viruses

Relenza Tamiflu Neuraminidase inhibitors act as transition state analogs of sialic acid.

Reovirus - Characteristics - Double-stranded RNA viruses

Reovirus was prepared under conditions of gentle crosslinking, viral disruption, and partial denaturation of the ds RNA. Note the RNA segments attached to the residual viral proteins.

Picornaviruses (Characteristic 3)

Replication is completely cytoplasmic

Adenoviruses - Characteristics - DS DNA

Respiratory, enteric, persistent Non-enveloped Icosahedral Genome Architecture Protein bound to 5' ends via C-terminal Inverted terminal repeats are ORI

Herpesviruses - Latency Requirements

Reversibly nonproductive infection of a cell by replication-competent virus Requirements for latency: 1. Evasion of host immunity - minimizing gene expression (HSV-1 via ncRNA in neurons) or specific genes designed to suppress immunity (EBV, CMV) 2. Genome persistence - Relatively 'easy' in non-dividing cells (neurotropic herpesviruses). More complex in dividing cells (lymphotropic herpesviruses use ncRNA and genes).

Vaccinia poxvirus - Packaging -Poxviruses

Rides microtubules from factories to sites of additional membrane wrapping. - In cell culture, a fraction of the intracellular mature virions (MV) remain intracellular (spreading by virus-induced cell-cell fusion). - The MV that externalize: First move away from the factory area by riding microtubular filaments to the cell surface (via interaction with kinesin motor). Microtubular movement: Above shows still images taken 8 h after infection, and 5 s apart, from confocal time-lapse recording of a HeLa cell expressing both "green" tubulin and "green" F13 protein on the virus. A single moving virus particle is indicated by the white arrowheads, the original starting position indicated by the yellow arrowhead.

Picornaviruses (Fast Facts)

SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 27 No Icosahedral RNA IV ss+; 3' poly(A) 5' protein (VPg) 1 6 - 8 7 - 8 kb MEMBERS poliovirus, rhinovirus, coxsackievirus, hepatitis A virus

Flaviviridae (Fast Facts)

SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 45 - 60 Y es Icosahedral RNA IV ss+ 1 8 - 10 10 - 11 kb MEMBERS yellow fever virus, Dengue virus, West Nile virus St. Louis encephalitis virus, Japanese encephalitis virus hepatitis C virus (HCV)

Paramyxovirus (Fast Facts)

SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 150 - 350 Y es Helix RNA V ss - 1 7 15 - 20 kb MEMBERS parainfluenza virus, mumps virus, measles virus Sendai virus, respiratory syncytial virus (RSV)

SV40 T-Antigen - Polyomaviruses - DNA Viruses

SV40 is very small and does not carry info for DNA rep. Essential for the host cell to enter S phase, when cell DNA and virus genome are replicated together. Protein-protein interactions between T-antigen and DNA polymerase directly stimulate replication in virus genome. Inactivation of tumor suppressor protein bound to T-antigen causes G1-arrest phase and divide and this results in transformation. A function of T-antigen is to alter the cellular environment to permit virus DNA replication.

Poxviruses - Next Round of Infection

Shows membrane #2 being lost from a CEV, revealing the MV with innermost membrane, ready to infect

Influenza Viruses - Specificity.

Sialic acid linkage preferences of influenza viruses contribute to species specificity Avian influenza viruses - a2,3 linkages. Human influenza viruses - a2,6 linkages. Crystal structure reveals - The amino acids surrounding the binding pocket are highly mutable whereas the pocket is not.

Parvoviruses - Key Points - DNA Viruses

Simplest virus: need S phase: 2 genes, rep and capsid Autonomous and dependoviruses (helper virus) Replication by hairpin loop priming - repair synthesis.

SV40 Genome and Genetic Map - Early Transcription Unit

Single mRNA precursor 1/2 of the genome 2 open translational reading frames Single pre-mRNA - Splices at 1 of 2 specific sites - Alternative splicing

Picornaviruses (Characteristic 2)

Single-stranded RNA genome: (+) strand polarity -> mRNA

Polyomavirus - Examples - DNA Viruses

Small, naked, icosahedral viruses with ds circular genomic DNA [~ 5 kbp (kilobase pairs)] (1) SV40 (simian virus 40) (2) Polyoma virus (a murine virus) (3) In humans: BK and JC virus (a) BK virus (BKV) is associated with hemorrhagic cystitis in the bladder. (b) JC virus (JCV) is the causative agent in progressive multifocal leukoencephalopathy (PML), a subacute, demyelinating disease; cell killing caused by replication of the virus in oligodendrocytes (the brain's myelin-producing cells). (c) Both BK and JC viruses induce tumors in hamsters and mice; also, they transform hamster cells in culture. More recent studies have found them associated with tumors of the human colorectal epithelium (JCV), brain (JCV and BKV), pancreas (BKV), lung (BKV), liver (BKV), and urinary tract (BKV). However, no causal link between JCV or BKV and these tumors has yet been demonstrated.

Smallpox - Chordopoxvirus.

Smallpox, Vaccinia represent only a narrow slice of the poxvirus family: They are individual species within just one of 8 genera in the chordopox subfamily, which is one of two sub-families of poxvirus. Poxviridae - Chordopoxvirinae

Poxviruses - DNA Viruses

Smallpox: First disease for which vaccine was developed, and totally eradicated. Cowpox - Benign, used to eradicate smallpox. Vaccinia virus - prototypical poxvirus used to study poxviruses.

Herpesvirus - Properties - DNA Viruses

Some have a wide host range, and some have a narrow host range - latency is restricted. Distinct transcription profiles. Some multiply rapidly (a HSV< VSV), others (B, y) Different cell types for latency: HSV, VSV, sensory neurons (ganglions), EBV memory B cells, CMV: T cells

Negative Strand Viruses (Rep Mech 6 - Paramyxoviruses)

Some viral mRNAs are edited to provide additional coding capacity for viral proteins. Example: Sendai virus P mRNA; full-length P protein is a phosphoprotein required for viral RNA synthesis V protein: W protein: has novel Zn2+ binding domain; antagonizes host innate immunity terminates just downstream from editing site; function unknown

Bunyaviruses (Examples)

Spread by Mosquito, fly, tick. Bunyavirues Bunyamwera virus - Febrile Illnesses, encephalitis, feverish rash. California encephalitis Phelobovirus Rift Valley Fever Nairovirus Uukuvirus Hantavirus Sin Nombre Virus - Hantavirus pulmonary syndrome

Arboviruses (Included Families)

Spread by Mosquitoes or Ticks: Togaviruses Flaviviruses Bunyaviruses Reoviruses

Flaviviruses (Examples)

Spread by mosquitoes and ticks Dengue - Fever Yellow Fever virus - Hepatitis, hemorrhagic fever Japanese encephalitis - West Nile virus - Hepatitis C virus - Hepatitis Zika virus - Neonatal Teratogeny

Epstein-Barr Virus - Herpesviruses

Spread through oral route of infection. Primary infection: nasopharynx epithelial cell. Establishes latency in B lymphocytes Immortalizes B cells Approx. 90 genes: Most function in viral rep. 14 latency associated genes (EBER) Virus produced by epithelial cells is more infectious for B cells. Virus produced by B cells equally infectious for B cells epithelial cells. Clinical diseases (e.g. mononucleosis) are associated with the latent state, not lytic reactivation as with HSV.

Herpesviruses - Reactivation

Stress response: Hyperthermia Fever Hypothermia UVB exposure Immunosuppression Physical trauma.

Picornaviruses (Characteristic 5)

Structure of virion RNA -> in virus particle, one strand per particle (a) ~7-8kb in length (b) Polyadenylated RNA -> 3' end of genomic RNA (c) 5' end has unique feature -> covalently-linked protein (called VPg)

Reoviridae - Characteristics - Double-stranded RNA viruses

Structure: Size - 70 to 85 nm Shape: nearly spherical icosahedral Nonenveloped Double protein capsid shell. Genome: Double-stranded RNA 10 to 12 segments. Replication: Fully cytoplasmic replication Inclusion body formation Full-length, capped (5'), nonpolyadenylated mRNA transcripts. Possession of all enzymes required for dsRNA transcription.

Reoviruses (Rotaviruses) - (Characteristic 5) - Double-stranded RNA viruses

Sub-viral particles contain an activated RNA-dependent RNA polymerase (transcriptase) that synthesizes (for reovirus) 10 individual mRNAs that are 5' capped but not 3' polyadenylated.

Poxviruses - DAPI and Replication

Subsequent steps of virus replication (including genome replication) occur within discrete virus factories in the cytoplasm that are attached to the nuclear envelope, surrounded by ER membrane. Each virion forms a discrete factory in the cytoplasm, attached to the nuclear envelope, which is surrounded by the ER membrane. Yellow DAPI - mRNA, viral, and host transcription factors, ribosomes, and translation factors co-localize within the discrete viral factories.

Herpesviruses - Gene Regulation Cascade

TAATGARAT: a-TIF _ Transcriptional activator, works with proteins to activate gene expression, aka VP-16 Virion factor turns on a-gene expression -> a-genes -> autoregulation of a-gene expression -> B-genes -> y-genes

Togavirus (Fast Facts)

TOGAVIRIDAE SIZE (nm): ENVELOPED: CAPSID SYMM: NUCLEIC ACID: CLASS: FORM: SEG: GENES: GENOME SIZE: 70 Y es Icosahedral RNA IV ss+; 5' cap 3' poly(A) 1 7 - 8 10 - 12 kb MEMBERS Sindbis virus, Semliki Forest virus, WEE, EEE, rubella virus

Papillomavirus - HPV - Genomic Replication - Circular ds DNA virus.

The genome is replicated as a multicopy nuclear plasmid. Two mechanisms are involved in genome replication: 1. Plasmid Replication - Occurs in cells in the basal layer. Dermis (dividing basal cells). Initially, the virus DNA is amplified to 50-400 copies / diploid genome. After this, it replicates once per cell division, the copy number / cell remaining constant. The E1 protein is involved in this phase of replication and DNA segregation (persistence) 2. Vegetative Replication - Occurs in terminally differentiated epidermial cells. DNA synthesis is normally off. Control of copy numbers is lost and DNA is amplified up to high levels.

Poxviruses - DNA replication

The point is simply that DNA replication seems to proceed through large concatameric (branched) intermediates. [The self-priming/rolling hairpin model shown below - speculative due to presence of viral primase (an enzyme not required for rolling-hairpin DNA replication), and the recent discovery of replication origins and Okazaki fragments.]

Papillomavirus - HPV - Oncogenes - Circular ds DNA virus.

The synergistic effect of E6 and E7, two oncogenes. Three groups of mice were followed for the frequency of skin tumors: mice transgenic for the E6 gene, for the E7 gene and for both genes. The expression of the oncogenes is controlled by - keratin 14 promoter - which is active in the basal cells and hair follicles where stem cells reside.

DNA Viruses - RNA synthesis / transcription

These DNA virus life cycles are under temporal control; divided into early and late gene expression. Generally, early functions precede viral DNA synthesis and late expression occurs after DNA synthesis. a. Early transcription: synthesis of mRNAs coding for viral biosynthetic enzymes (1) Examples of proteins encoded by early mRNAs: (a) Viral DNA polymerase (adenovirus and herpesviruses) (b) Viral DNA binding proteins (c) Other proteins involved with DNA synthesis (2) Transcription is carried out by host cell RNA polymerase II (normally carries out host cell mRNA synthesis). (3) After transcription, these mRNAs are processed (capped, polyadenylated, and/or spliced) before they are transported to the cytoplasm.

Reoviruses (Rotaviruses) - (Characteristic 6) - Double-stranded RNA viruses

These mRNA are then translated and the viral proteins produced initiate subsequent rounds of RNA synthesis, ultimately producing progeny ds RNA molecules.

Influenza - Orthomyxoviruses - Transcription and Regulation

Transcription apparatus encodes a nuclease activity that cleaves capped mRNAs ~ 10-15 nucleotides from the cap structure of cellular mRNAs in nucleus; called "cap stealing". Nuclease cleavage of cellular mRNAs provides a primer for chain elongation by viral RNA-dependent RNA polymerase. Virus needs a constant supply of newly-synthesized capped mRNAs in the nucleus of infected cells to allow initiation of influenza transcription, which explains inhibitor data and the presence of viral antigens in nucleus. Assembly of nucleocapsids occurs in nucleus, while envelope (with viral glycoproteins) is assembled at plasma-membrane surface; assembled nucleocapsids are transported to patches on cytoplasmic surface of the plasma membrane where this assembly process begins (M1, the matrix protein may help.)

Retrovirus - Cell Transformation by Viruses

Transformed cells have an altered phenotype: Displayed as one (or more) of the following characteristics: Immortalization Loss of anchorage dependence Loss of contact inhibition (surface communication) Colony formation in semi-solid media. Decreased requirements for growth factors. Form tumors in immunocompromised.

Retrovirus - Transduction by Viruses

Transforming genes (v-oncs) dervied from host and are highly homologous to normal cellular growth control genes: c-oncs. Most v-oncs possess minor seq alt which alter the function of oncoprotein produced, others contain short deletion gene. Most transducing retroviruses (rep-def). Acquire onc causes loss of function of essential genes. RSV and MMTV are uncommon types. Most oncoproteins from acutely transforming retroviruses are fusion proteins, containing additional sequences derived from virus genes. These additional seq may alter the function or the cellular protein and these abnormal attributes result in transformation.

Orthomyxoviruses - Influenza - Epidemiology - Negative Sense RNA

Transmission: Inhalation of small aerosol droplets Widely spread by school children At risk or risk factors: Adults (flu) Children (asymptomatic to severe) Elderly, immunocompromised, cardiac or respiratory problems ( high risk) Distribution: Ubiquitous; local epidemics, global pandemics. More common in winter. Vaccines or antiviral drugs: Killed vaccine against annual strains of influenza A and B viruses. Live, attenuated influenza A and B vaccine (nasal spray) Antiviral drugs: amantadine, rimantadine, zanamivir, oseltamivir.

Bunyaviruses (Epidemiology)

Transmission: Arthropod bite Rodent excreta At risk or risk factors: People in area of vector, eg. campers, forest rangers, woodspeople Distribution of virus: Depends of distribution of vector or rodents. Disease more common in summer Vaccines or antiviral drugs: None.

Filoviruses (Examples) - Negative Strand RNA - Nonsegmented

Transmission: Contact with infected monkeys, tissues, secretions, or body fluids Contact with infected humans Accidental injections, contamiated syringes At risk or risk factors: Monkey handlers Health care workers attending sick Distribution: Endemic in African monkeys No seasonal Vaccines: None

Arenaviruses - Epidemiology - Negative Sense RNA Viruses

Transmission: Contact with infected rodents or their secretions or body fluids. At risk or risk factors: Lymphocytic choriomeningitis virus: contact with pet hamsters, rodent infestations, habitats. Distribution of virus: Lymphocytic choriomeningitis virus: hamsters and house mice in Europe, Americas, Australia, possibly Asia. Other arenaviruses: Africa, South America, United States No seasonal incidence. Vaccines or antiviral drugs: No vaccines Antiviral drug ribavirin.

Paramyxoviruses - Respiratory syncytial virus - Epidemiology - Neg Strand RNA

Transmission: Inhalation of large-droplet aerosols At risk or risk factors: Infants (bronchiolitis, pneumonia) Children (mild disease to pneumonia) Adults (mild symptoms) Distribution of virus: Ubiquitous Incidence seasonal Vaccines or antiviral drugs: No vaccine Antiviral drugs: ribavirin for infants

Paramyxoviruses - Measles virus - Transmission - Neg Strand RNA

Transmission: Inhalation of large-droplet aerosols Highly contagious At risk or risk factors: Adults and children Immunocompromised persons (more serious outcomes) Distribution: Ubiquitous Endemic from autumn to spring Vaccines or antiviral drugs Live, attenuated vaccine No antiviral drugs.

Paramyxoviruses - Mumps virus - Transmission - Neg Strand RNA

Transmission: Inhalation of large-droplet aerosols Highly contagious At risk or risk factors: Adults and children Immunocompromised persons (more serious outcomes) Distribution: Ubiquitous Endemic from late winter, and early spring Vaccines or antiviral drugs Live, attenuated vaccine No antiviral drugs.

Togaviruses (Epidemiology)

Transmission: Mosquito Vectors Rubella Virus: Respiratory Route Vaccines or antivirals: Live, attenuated vaccine - Rubella No antiviral drugs

Flaviviruses (Epidemiology)

Transmission: Mosquito or tick vectors Distributed: Aedes Mosquito: Urban Culex: Forest At risk: Niche of vector Vaccines: Live, attenuated - Yellow fever and Japanese encephalitis No antiviral drugs

Rhabdoviruses (Epidemiology) - Neg Strand RNA

Transmission: Reservoir: Wild animals Vectors: wild animals, dogs, cats Bite of rabid animal or aerosols from caves with rabid bats Distribution: Ubiquitous No seasonal incidence At risk: Animal handlers No pet vaccinations Vaccines or antiviral drugs: Vaccines for pets and wild animals Inactivated for at-risk, postexposure prophalayxis No antiviral drugs

Sin Nombre Virus - Bunyavirus - Segmented, Negative Sense RNA

Transmission: vertebrate hosts, no arthropod vectors Viral particles: spherical, 80-120 nm Structural proteins: glycoproteins: G1, G2 nucleoprotein: N Genome: ss RNA, tri-segmented, negative polarity

Reoviruses (Rotaviruses) - Epidemiology - Double-stranded RNA viruses

Transmission: Fecal-oral route. At risk: Rotavirus type A Infants (gastroenteritis, dehydration) Older children (mild diarrhea) Undernourished persons in underdeveloped countries (diarrhea, dehydration, death) Rotavirus type B Infants, older children, adults in China (severe gastroenteritis) Distribution of virus: Ubiquitous (Type A) Less common in summer Vaccines or antiviral drugs Live, attenuated vaccines (multivalent): RotaTeq (Merck) Rotarix (GlaxoSmithKline)

Rotavirus - Disease Mechanisms

Transmitted by fecal-oral route nsP4 is a viral enterotoxin that causes diarrhea (causes holes) Disease is serious in infants <24 months old, asymptomatic. Large quantities of virions released in diarrhea Immunity to infection depends on IgA in gut lumen.

Paramyxoviruses - Mumps virus - Disease Mech. - Neg Strand RNA

Transmitted by respiratory secretions Infects epithelial cells of respiratory tract Replicates in salivary glands, testes, respiratory tract, central nervous system Cell-mediated immunity is required to control infection

Paramyxoviruses - Measles - Disease Mechanisms - Neg Strand RNA

Transmitted by respiratory secretions Infects epithelial cells of respiratory tract, spreads in lymphocytes and by viremia Replicates in conjunctivae, respiratory tract, urinary tract, lymphatic system, blood vessels, central nervous system T-cell response to virus-infected capillaries, endothelial cells cause rash. Complications are due to immunopathogenesis (postinfectious measles encephalitis) or viral mutants (subacute sclerosing panecephalitis)

Rhabdoviruses (Mech) - Neg strand RNA

Transmitted by saliva or aerosols Replicates in muscle at bite Incubation period of weeks to months Infects peripheral nerves Replication in brain causes hydrophobia, hallucinations, paralysis Spreads to salivary glands Postexposure immunization can prevent due to long incubation period.