Exam 6
Compare and contrast the major steps of bacteriophage and animal viral replication.
Bacteriophages: Animal Virus: Attachment -tall fiber attaches to proteins Entry -viral DNA injected into host receptor Uncoating -not required Biosynthesis -in cytoplasm Chronic infection -Lysogeny Release -Host cell is lysed Animal virus: Attachment -attachment sites are plasma cellular membranes and glycoproteins Entry -capsid enters by receptor-mediated endocytosis or fusion Uncoating -enzymatic removal of capsid proteins Biosynthesis -in nucleus of DNA virus; in cytoplasm of RNA virus Chronic infection -latency;slow viral infection Release -enveloped viruses bud out; nonenveloped virsuses rupture plasma membrane
Track the changes in HIV numbers in the blood, CD4 T-helper cell count in the blood, and anti-HIV antibodies in the blood during (1) the weeks post-infection with HIV, and (2) the years post-infection with HIV. A CD4 T-helper cell count below ____________ is diagnostic for AIDS. What is AIDS? What is an opportunistic disease (in the context of HIV infection)?
CD4 Tcell count below 200/ml is diagnostic for AIDs AIDs: acquired immunodeficiency syndrome Oppurtunistic diseases occur more frequently and are move severe due to a weakened immune system
Briefly discuss the progression of disease in Ebola-infected individuals, including early stage, middle stage, and late state symptoms.
Early Symptoms: 2-21 days after infection; headache, fever, fatigue, dizziness, sore throat, muscle pain. followed by minor red and purple blood spots Middle Stage: high fever, massive bloody vomitting, and diarrhea Late Symptoms: damage to blood vessels causes severe interal hemorrhaging as well as bleeding from other body orifices, including mouth, eyes, and ears, and organ damage. Survivors have long-lasting, severe joint pain and eye complications ranging from vision changes to inflammation leading to blindness
Discuss the epidemiology, diagnosis, treatment, and prevention of HHV-1 and HHV-2 infections.
Epidemiology: -spread b/w mucous membranes of mouths/gentials -herpes infections in adults are not life threatening -neonatal infections can be fatal Diagnosis, Treatment, and Prevention: -diagnosis is made by presence of characteristic lesions -immunoassay reveals presence of viral antigens -chemotherapeutic drugs help control the disease but do not cure it -healthcare workers can wear gloves to limit exposure
Discuss the epidemiology, diagnosis, treatment, and prevention of papillomavirus infections.
Epidemiology: transmitted via direct contact & fomites; individuals can spread viruses among locations on their own body Diagnosis: -diagnosed by observation Treatment: -various techniques to remove warts; new warts can develop as a result of latent viruses
What is a poxvirus? Provide the taxonomic information for the poxviruses.
Family Poxvirdiae Genus Orthopoxvirus
What are the symptoms of the flu? What are the biological roles performed by HA and NA spikes? How is the annual flu prevented?
Fever, chills, headache, and muscle aches Hemaggluntin (HA) spikes: attachment to host cells Neuraminidasse (NA) spikes: release virus from cell
Which countries were most directly affected by the 2014 Ebola epidemic?
Guinea, Sierra Leone, Liberia
Which two viruses are known as (or until recently were known as) hemorrhagic viruses, or filoviruses?
Marburg virus Ebola virus
What is the vector for the arboviruses that cause EEE, WEE, SLE, and LAC? What do each of these abbreviations "stand for"? What is encephalitis?
Mosquito EEE: eastern equine encephalitis WEE: western equine encephalitis SLE: St. Louis encephalitis LAC: La Crosse encephalitis Encephalitis is inflammation of the brain
In what geographical regions (worldwide) is HIV/AIDS most prevalent? What are the primary modes of HIV transmission, as indicated by modes of HIV transmission in people over 12 years of age in the United States during 2011?
Most prevalent in US, Africa, Russia, China, and India Males: homosexual contact, high risk heterosexual contact, use of injected drugs Females: high risk hetero contact, use of injected drugs
Briefly discuss how hemorrhagic viruses are transmitted to humans and the diagnosis, treatment, and prognosis of infected human individuals.
Natural reservoir and mode of transmission to humans is unknwn Spread b/w humans by contaminated body fluids and syringes Uncontrolled bleeding under the skin and from every body opening 90% of human victims die; only treatment is fluid replacement
Which poxvirus causes smallpox? How is smallpox transmitted? Why was it possible to eradicate smallpox?
Orthopoxvirus variola causes smallpox. It is transmitted via inhalation of virus. It was possible to eradicate smallpox because ring vaccination, anyone who came in contact with an infected person was found and vaccinated.
How are common cold viruses transmitted? A _____________ deposited on the nasal mucosa is often sufficient to cause a cold. How does the dry, cool air of winter facilitate the transmission of the common cold?
Transmitted via airborne droplets or by contacted w/ infected nasal secretions or other contaminated objects. single In the cool, dry air, droplets are smaller and remain airborne longer. The cillary body also moves slower, allowing the virus to spread in the upper respiratory system.
Discuss what is meant by viral dormancy with respect to the virus that causes "chicken pox" and the relationship between viral dormancy and shingles.
VZV remains dormant in the nervous system, trigeminal and dorsal root ganglia, of the patient. It reactivates later in life producing shingles
What is the name of the virus that causes so-called "chicken pox"? What are the symptoms of "chicken pox"?
Varicella Zoster virus Symptoms; -itchy rash -fever -headache
Describe the signs, symptoms, and pathology of warts. Papillomaviruses cause warts? Provide the taxonomic information for the papillomaviruses.
Various papillomaviruses casue warts. Signs/Symptoms: benign epithelial growth on skin or mucous membranes; can form on many body surfaces Pathogensis: warts develop over time; most are harmless; papillomaviruses may precipitate some cancers Family Papovavirdae Genus Papillomavirus
What is a virion? Name and describe the various components of a virion.
Virion is a complete, fully developed infectious viral particle. It consists of: nucleic acid (DNA or RNA), capsid (capsomeres), envelope, and spikes.
Describe how viruses are grouped for taxonomic purposes. How is a viral species defined? What kinds of characteristics are used to classify viruses. Which taxonomic levels are linked to the following two suffixes: -viridae and -virus.
Virsues are grouped by host range: animal, bacterial, or plant Viral species are groups of viruses that share the same genetic info and ecological niche (host) Classification systems are based on: type of nucleic acid, morphological shape & presence or absence of an envelope -viridae: family name -virus: genus name
Contrast the general size of viruses with that of prokaryotic and eukaryotic cells.
Virus-small Prokaryote-big Eukaryote- large
Compare and contrast viruses with the cells of living organisms and explain why viruses are not technically considered living organisms.
Virus: Cells: ~inert outside cell ~do not divide or grow ~acellular ~obligate intracellular parasite ~contain DNA or RNA ~genomes: dsDNA, ssDNA, dsRNA, ssRNA ~Ultramicroscopic(10nm-500nm) ~proteionaceous capsid around genome ~some have envelope around capsid ~replicate assembly line style using enzymes and organelles of host Cells: ~metabolize on their own ~divide and grow ~cellular ~most are free living ~contain DNA and RNA ~genome: DNA ~200nm-12cm ~phospholipid membrane and cell wall ~self replicating via asexual or sexual repro Viruses are not considered living organisms because they are inert outside of a living host.
Zika virus is closely related to which types of virus that are more commonly known? What are the usual symptoms associated with Zika viral infections? Briefly describe pregnancy-related issues related to Zika infection.
Yellow fever, dengue, West Nile, Japanese encephalitis viruses Symptoms: asymptomatic or mild symptoms including fever, rash, joint pain, conjunctivitis, muscle pain, headache Microcephaly: smaller head in infants; causes brain to be smaller and not properly developed
The virus has only _______________ genes. The viral genome contains information to make __________ and ____________. Viruses use the host's _____________________________ to replicate their genetic material and for protein synthesis.
a few; protein and enzymes; metabolic machinery
What is an "arbovirus"? Name at least two viruses that are accurately described as "arboviruses" and have infected humans in the continental United States in the 21st Century.
arbovirus: ARthropod-BOrne virus West Nile Virus and Zika Virus
Although viruses do not reproduce within the contents of the digestive system like ______________, they invade many organs associated with the system.
bacteria
How is arboviral encephalitis prevented?
controlling mosquitoes; DEET
Viruses can be ___________ to study. ___________________ are commonly used in viral studies; the virus grows in the developing chick embryo or associated tissues.
difficult; embryonated eggs
Outside the risk associated with avian influenza, there is rapid _____________ of the HA and NA antigens that the human immune system encounters. Changes in the structure of the HA and NA proteins arise as a result of ______________ and ________________. Discuss these two sources of HA and NA change.
evolution genetic mutations Two sources of HA and NA change: antigenic drift: accumulations over time (RNA viruses have a high mutation rate) antigenic shift: caused by major genetic recombination events
The majority of arboviral infections in humans are asymptomatic or may result in a non-specific ___________________________. Onset may be insidious (slow) or sudden with ____________, ______________, ____________, and _________________. Infection may, however, lead to encephalitis, with a fatal outcome, or permanent _____________________.
flu-like symptoms; fever, headache, myalgias, malaise; neurological damage
The ultimate goal is to develop a flu vaccine that will protect against all flu strains. For now, there are two kinds of flu vaccine available: _______________ and _______________.
injected, inactivated vaccine nasal spray vaccine made w/ a live, attenuated virus
Dane particles are ____________ for HBV infection. What are Dane particles? Differentiate a Dane particle from a filamentous particle and a spherical particle. With which hepatitis virus are Dane particles associated?
necessary; Dane particles are a complete HBV particle. It is associated with HBV
For a virus to reach the lower respiratory system and initiate disease, it must pass numerous host defenses designed to ________________. Nonetheless, numerous respiratory ailments are caused by viruses.
trap and destroy it
Probably the most prevalent disease of humans, at least those living in the temperate zones, is a viral diseases affecting the ___________ respiratory system known as ______________.
upper; the common cold
The flu virus responsible for the flu pandemic of 1918-1919 was unusually _____________; the virus may have been better able to infect cells in many ____________ than other flu strains. During the flu pandemic of 1918-1919, approximately how many humans died worldwide? Approximately how many humans died in the United States?
virulent organs worldwide deaths: 20-50m U.S deaths: 675k
Describe what is meant by each of the following: positive-sense, single-stranded RNA virus (+ssRNA); negative-sense, single-stranded RNA virus (-ssRNA), and double-stranded RNA virus. Generally: how is viral multiplication achieved by each of these types of RNA viruses?
+ssRNA-positive-sense, single stranded RNA: similar to mRNA and can be immediately translated -ssRNA-negative-sense, single stranded RNA: complentary to mRNA so it must be transcripted into +ssRNA and then can be translated
Describe the various kinds of lesions associated with warts in different bodily regions.
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The so-called "central dogma of biology" has been discussed at various points in both the lecture and lab Microbiology courses this semester. Describe the biomolecules and biological processes that constitute the "central dogma of biology." Why is it important to keep this in mind when studying viruses?
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Name two ways in which spongiform encephalopathies can develop. What is the condition of spongiform encephalopathy called in cattle? In sheep? In humans?
... Sheep: sheep scrapie Humans: Creutzfeldt-Jakob disease Gerstmann-Straussler-Scheinker syndrome Cattle: Mad Cow disease
Name and discuss four characteristics shared by all viruses. Some viruses also possess an envelope or spikes. What is a viral envelope? What are spikes?
Acellular Obligatory intracellular parasites (inactive outside living host Contain DNA or RNA Contain protein coat Viral envelope is a lipid bilayer that surrounds the capsid and contains viral proteins Spikes are a glycoprotein that will only bind to certain receptors
Name four human ailments of the nervous system to which prions may be linked.
Alzheimer's Parkinson's Huntingtons Amyotrophic
Because filoviruses are extremely infectious, ____________ procedures are reuiqred in order for laboratory workers to perform diagnostic testing.
BSL-4
What is a virus that infects bacteria called? What is a prophage?
Bacteriophage copy of the viral genome inserted into host cell chromosome
REVIEW: Compare and contrast the major steps of bacteriophage and animal viral replication.
Bacteriophages: Animal Virus: Attachment -tall fiber attaches to -att. sites are plasma cellular proteins membrane proteins and glyco proteins Entry -viral DNA injected -capsid enters by into host receptor-mediated endocytosis or fusion Uncoating -not required -Enzymatic removal of capsid proteins Biosynthesis -in cytoplasm -in nucleus (DNA virus); in cytoplasm (RNA virus) Chronic infection -Lysogeny -latency; slow viral infection Release -Host cell is lysed -enveloped viruses bud out; nonenveloped virsuses rupture plasma membrane
Name and describe the six steps of animal virus infection and multiplication.
1. Attachment -virus attaches to cell membrane 2. Penetration -enters cell by endocytosis or fusion 3. Uncoating -virus capsis is destroyed by viral or host enzymes and its genetic material is released inside cell 4. Biosynthesis -production of nucleic acid 5. Maturation -nucleic acid and capsid proteins are synthesized and new virus is assembled 6. Release - by budding (enveloped virus) or rupture
REVIEW: Name and describe the six steps of animal virus infection and multiplication.
1. Attachment -virus attaches to cell membrane 2. Penetration -enters cell by endocytosis or fusion 3. Uncoating -virus capsis is destroyed by viral or host enzymes and its genetic material is released inside cell 4. Biosynthesis -production of nucleic acid 5. Maturation -nucleic acid and capsid proteins are synthesized and new virus is assembled 6. Release - by budding (enveloped virus) or rupture
List and describe the stages of lesions of poxviral skin infections.
1. Macule 2. Papule 3. Vesicle 4. Pustule 5. Crust 6. Scar
Describe the multiplication and inheritance processes of the Retroviridae. In what critical ways is viral multiplication of retroviruses different from other RNA viruses?
1. retrovirus enters host cell by fusion b/w attachment spikes and host cell receptors 2. uncoating releases the 2 viral RNA genomes and viral enzymes reverse transcriptase, integrase, & protease 3. reverse transcriptase copies viral RNA to produce dsDNA 4. new viral DNA is transported into the host cell's nucleus, where it is integrated into a host cell chromosome as a provirus by viral integrase. The provirus may be replicated when the host cell replicates 5. transcription of the provirus mat also occur producing RNA for new retrovirus genomes & RNA that encodes the retrovirus capsid, enzymes, & envelope proteins 6. Viral proteins are processed by viral protease. Some of the viral proteins are moved to the host plasma membrane 7. Mature retrovirus leaves host cell, acquiring an envelope, and attachment spikes as it buds out
More than ______ different viruses are known to cause colds. Which two types of viruses most commonly cause the common cold? What are the symptoms of this ailment?
200 Rhinovirus and Corona Virus
How does a prion differ from a virus? Briefly describe how a protein can be infectious.
A prion is an infectious protein composition that infects mammals Virus-DNA/RNA Prion-Protein
Briefly discuss the basic biological characteristics and pathology of each of the RNA hepatitis viruses.
HAV: ssRNA w/o an envelope; no chronic form of hepatitis A HBV: larger than HAV; genome is dsDNA; enveloped; 1/3 of the world's population shows serological evidence of past infection but most have cleared the virus HCV: ssRNA; enveloped; doesnt kill the infected cells but triggers an immune inflammation response that may destroy liver; majority of cases progress to chronic hepatitis HDV: ssRNA; if occuring w/ HBV, a super infection can cause progressive liver damage w/ high fatality rate; HDV is not capable of causing infection; it becomes infectious when a surface antigen of HBV covers the protein core of HDV HEV: ssRNA; known as "enteric hepatitis" as it is associated w/ fecally contaminated drinking water, causes inflammed liver; fatal in 20% of infected pregnant woman
How is HDV infection related to HBV infection?
HBV must cover the protein core of HDV for it to become infectious.
Describe the signs and symptoms of human herpesvirus (HHV) infections. Differentiate between HHV-1 and HHV-2 infections.
HHV-1 HHV-2 Usual Diseases -90% of cold sores -85% of genital herpes fever blisters; whitlow Mode of Transmission -Close Contact -Sexual intercourse Site of Latency -Trigeminal and -Sacral ganglia brachial root Locations of lesions -Face, mouth, & rarely -External genitalia and trunk thighs, butt, and anus
In what skin areas do HHV-1 and HHV-2 lesions commonly form? Are lesions generally painful?
HHV-1: face, mouth, rarely trunk HHV-2: sexual genitalia
Name and describe the four general categories of viruses with respect to general morphology.
Helical Viruses -resemble long rods; capsids are hollow cylinders w/ helical structure (ex. tobacco mosaic virus) Polyhedral (many sided) Viruses -capsid in shape of a icosahedron, which has 20 sides, (ex. adenovirus) Enveloped Viruses -have an outer membrane surrounding capsid (ex. influenza, HIV virus) Complex Virus: -do not contain an identifiable capsid (ex. bacteriophages-virus that infects bacteria)
How are the other four hepatitis viruses different biologically different from Hepatitis B virus? Which of the other four hepatitis viruses can only infect humans if "piggybacking" on a Hepatitis B infection?
Hepatitis B is the only DNA virus out of all 5 viruses. Hepatitis D piggybacks on HBV to cause an infection
What is hepatitis? Other than chemical toxicity, EB virus, or CMV, which viruses cause various forms of hepatitis? Which of the hepatitis viruses is an RNA virus? Which of the hepatitis viruses is a DNA virus?
Hepatitis is an inflammation of the liver. Chemical toxicity, EB virus, CMV, and hepatitis virus cause various forms of hepatitis. HAV, HCV, HDV, HEV=RNA virus HVB=DNA virus
What is hepatitis? Hepatitis may result from ___________, ___________, __________, or the ____________ viruses.
Hepatitis is the inflammation of the liver. May result from toxicity, EB virus, CMV, or the hepatitis viruses.
Do viruses have generally have general or specific host ranges and abilities to infect different types of cells? Explain.
Host range is determined by specific host attachment sites and cellular factors. Most viruses only infect specific cells.
What does HIV "stand for"? Which human body system is primarily targeted (especially during the initial stages of infection)? Describe the HIV virion, its various components, and the function of key components, such as reverse transcriptase and integrase.
Human immunodeficiency virus The immune system is primarily targeted especially during initial stages of infection. Components of HIV virion: capsid (ssRNA genome, protease: processes viral proteins, integrase: integrates viral DNA into host cell chromosome, reverse transcriptase: copies RNA) envelope spikes made of gp120(stems) and gp41(tops)
Briefly discuss the concern regarding the formation of an altogether new flu virus as a result of multiple different flu viruses, typically found in separate host species, occupying a single host animal.
If a host is infected with different viruses for the flu, the viruses can swap genetic material with each other, forming a new flu virus.
Name and describe the five steps of the lytic cycle. Describe the lysogenic cycle. Contrast the lytic and lysogenic cycles. How are these cycles interrelated with respect to infected bacteria?
Phage attaches to the host cell and injects DNA. The DNA circularizes and enters the lytic or lysogenic cycle Lytic: 1.Attachment -phage attaches by tail fibers to host cell 2. Penetration -phage lysozyme opens cell wall; tail sheath contracts to force tail core & DNA into cell 3. Biosynthesis -production of phage DNA & proteins 4. Maturation -assembly of phage particles 5. Release -phage lysozyme breaks cell wall Lysogenic cycle: 1. Phage DNA integrates w/in bacterial chromosomes by recombination, becoming a prophage 2. Lysogenic bacterium reproduce normally ----many cell divisions----- 3. Occasionally, the prophage may excise from the bacterial chromosome by another recombination event, starting a lytic cycle. With respect to infected bactera, lytic cycle is the active part and the lysogenic cycle is the latent part of infection.
Which viral taxonomic family includes HIV? Briefly discuss the multiplication process for RNA "retroviruses."
Retroviridae 1. retrovirus enters host cell by fusion b/w attachment spikes and host cell receptors 2. uncoating releases the 2 viral RNA genomes and viral enzymes reverse transcriptase, integrase, & protease 3. reverse transcriptase copies viral RNA to produce dsDNA 4. new viral DNA is transported into the host cell's nucleus, where it is integrated into a host cell chromosome as a provirus by viral integrase. The provirus may be replicated when the host cell replicates 5. transcription of the provirus mat also occur producing RNA for new retrovirus genomes & RNA that encodes the retrovirus capsid, enzymes, & envelope proteins 6. Viral proteins are processed by viral protease. Some of the viral proteins are moved to the host plasma membrane 7. Mature retrovirus leaves host cell, acquiring an envelope, and attachment spikes as it buds out