Virus Supplement Study Guide
What is Hepatitis A virus (HAV)?
(Genus Hepatovirus) Hepatitis A, also known as infectious hepatitis, is caused by the RNA-type hepatitis A virus. Symptoms include tender abdomen, fever, nausea, loss of appetite, and eventually jaundice. Recovery is usually complete in 3 months. Transmission of (HAV) is typically via direct contact (orally or through sexual intercourse), but may involve the use of dirty needles.
What is Hepatitis C virus (HCV)?
(genus Hepacvirus) Hepatitis C is the etiological agent of the silent epidemic, a form of hepatitis that has killed more people in the Unites States than AIDS. These viruses are capable of rapid genetic variation and tend to invade the immune system. Their mode of transmission is not entirely clear.
What is Hepatitis B virus (HBV)?
(genus Hepadnavirus) Hepatitis B, also known as serum hepatitis, is caused by the DNA-type hepatitis B virus (HBV), and is a severe form of hepatitis that is sometimes progressively fatal. Transmission of HBV is typically via contaminated needles or serum inoculations. HBV can also cause liver tumors.
The mRNA transcribed from genes encoding viral envelope proteins is translated by _____________ attached to the ________________. The polyprotein produced is moved to the Golgi complex where it is cleaved and ____________.
*Ribosomes attached to the rough endoplasmic reticulum.* The polyprotein produced is moved to the Golgi complex where it is cleaved and *glycosylated*
Diseases of the Gastrointestinal System:
1) Picornaviruses(Picornaviridae) 2) Hepadnaviruses (Hepadnaviridae) 3) Flaviviruses(Flaviviridae) 4) Deltaviruses(Deltaviridae) 5) Caliciviruses (Caliciviridae)
Diseases of Skin and Oral/Genital regions:
1. Herpesviruses (Herpesviridae) Paramyxoviruses (Paramyxoviridae) Togaviruses (Togaviridae) 4) Poxviruses (Poxviridae) 5) Human Papovaviruses (Papoviridae)
What are the different types of Herpesviruses (Herpesviridae)?
1. Human herpesvirus 1 and 2 (genus Simplexvirus) 2. Human herpesvirus 3 (genus Varicellovirus) 3. Human herpesvirus 4 (genus Lymphocryptovirus) 4. Human herpesvirus 6 (genus Roseolovirus) 5. Human herpesvirus 8
What are the types of Caliciviruses (Caliciviridae)?
1. Norwalk-like virus (genus Norovirus) 2. Hepatitis E virus
The Human Immunodeficiency Virus (HIV) is a __________, __________-stranded RNA type virus known as a retrovirus because it has the ability to: This virus has an envelope and enters its host by fusing its viral _________ with the host cell __________.
A diploid, single-stranded RNA type virus known as a retrovirus because it has the ability to reverse transcribe the information carried on its viral genome from RNA into DNA. This virus has an envelope and enters its host by fusing its viral envelope with the host cell membrane.
What is the protein hemagglutinin (H)?
A protein that causes red blood cells to clump together
Eventually the viral DNA will become __________ (possibly being triggered by other viral agents, stress, etc.) and will be transcribed.
Active (possibly being triggered by other viral agents, stress, etc.)
Typically the human body will produce quantities of immune cells and antibodies against specific types of antigens following exposure to them, but _______________ responses are specific. This means that vaccines developed to protect people must stimulate an immune response against the right ______________ in order to be effective.
Adaptive immune responses are specific. Virus serotype
After release, ___________ enzymes separate the proteins of the polyprotein chains and these undergo assembly to form the _________ and ________ layers characteristic of mature visions.
After release, *protease* enzymes separate the proteins of the polyprotein chains and these undergo assembly to form the *capsid and matrix* layers characteristic of mature visions.
What is the protein neuraminidase (N)?
An enzyme that breaks the glycosidic linkage of neuraminic acid (a component of N-acetylneuraminic acid, a substance associated with mucous membranes and prevention of infection).
Influenza viruses can change their surface antigens (hemagglutinins and neuraminidases) through two different mechanisms called ____________ and _____________.
Antigenic drift and antigenic shift.
What is Antigenic drift?
Antigenic drift involves slight changes in surface antigens due to mutation. The viral RNA genome can experience random changes in nucleotide sequence, and these can change the proteins ultimately made. Recall the potential consequences of substitution type point mutations (silent, missense and nonsense) and the changes in amino acid sequence that can result from insertion or deletion mutations (frameshifts).
What is Antigenic shift?
Antigenic shift involves more significant changes in surface antigens due to recombination of RNA strands from more than one host within a single virion. Because influenza A viruses can infect swine, fowl and humans it is possible for one host to be infected by viruses from different sources. This is especially true where humans, swine and fowl live in close proximity and have frequent contact. If RNA strands from different virus types are recombined within the same capsid, the resulting virus is likely to produce a new combination of hemagglutinin and neuraminidase antigens.
Viruses that infect plants (also those infecting algae and fungi) must cross a rather formidable barrier represented by the cell wall surrounding these cells. In the case of plant viruses, this barrier is passed with the aid of:
Biting arthropods (mites and insects), nematodes, snails, etc. that feed on plant tissues.
The influenza A viruses that infect humans can also infect swine and fowl, so have a ________ host range. These viruses are enveloped, and can be divided into subtypes based on two ___________ present on their envelope surfaces.
Broad Proteins (antigens) - hemagglutinin (H) & neuraminidase (N)
Immature virus particles typically exit host cells by means of a process called ___________________
Budding (however HIV can also be passed from cell to cell).
Polyprotein chains, enzymes and viral RNA collected near the cell surface cause the cell membrane to______________. The membrane eventually breaks and the _____________________ is released into the environment.
Bulge outward. Immature virion (wrapped in a membranous envelope)
Influenza viruse D infects primarily __________
Cattle.
What is Human herpesvirus 6 (genus Roseolovirus)?
Causes exanthema subitum or sixth disease, an acute, short-lived disease of infants and young children characterized by high fever (for 3-4 days) followed by a skin rash.
Animal viruses can more readily gain access to their host cells because animal cells do not have _______________
Cell walls
What are Cowpox (genus Orthopoxvirus)?
Cowpox is a zoonosis commonly associated with rodents, but also transmitted to cats, cows and humans. Edward Jenner used the fluid from cowpox lesions to prevent smallpox.
What is Hepatitis D virus (HDV)?
Delta Hepatitis or Hepatitis D is viroid-like and related to HBV. It can cause both acute and chronic hepatitis. During coinfection with hepatitis B, HDV can cause progressively fatal damage to the liver.
Since the budding process damages the host cell membrane, the release of numerous virus particles will ultimately cause the host cell to _____________.
Die
In most cases, animal viruses enter cells by means of:
Endocytosis, a process involving the activity of actin and other proteins.
What is Human herpesvirus 4 (genus Lymphocryptovirus)?
Epstein Bar herpesvirus and 5 (Cytomegalovirus) cause infectious mononucleosis, Burkitt's lymphoma, nasopharyngeal carcinoma, and cytomegalic inclusions disease.
The viral ____________ within the chromosome of the host cell will be replicated along with that chromosome, and any new cells formed via mitosis will also carry the ___________.
Genome Virus.
What is a type of Togaviruses (Togaviridae)?
German measles (genus Rubivirus)
It is the loss of the __________________ (along with associated imbalances within the immune system) that ultimately brings on the symptoms of Acquired Immune Deficiency Syndrome (AIDS). Loss of immune function leaves the host organism susceptible to:
Helper-T lymphocytes Infection by numerous opportunistic pathogens that can eventually kill the host.
What is a type of Picornaviruses(Picornaviridae)?
Hepatitis A virus (HAV)
What is a type of Hepadnaviruses (Hepadnaviridae)?
Hepatitis B virus (HBV)
What is a type of Flaviviruses (Flaviviridae)?
Hepatitis C virus (HCV)
What is a type of Deltaviruses (Deltaviridae)?
Hepatitis D virus (HDV)
What is Human herpesvirus 1 and 2 (genus Simplexvirus)?
Herpes labialis and genitalis. Most commonly associated with cold sores (fever blisters) and genital herpes (also neonatal herpes) respectively, but can cross infect.
Viruses can also enter when plant tissue is damaged through ___________ or _____________ activity or through other events resulting in plant trauma. The same is probably true for viruses infecting fungi and algae.
Human or grazing animal activity
What are the types of Human Papovaviruses (Papoviridae)?
Human wart virus (genus Papillomavirus)
What is Human wart virus (genus Papillomavirus)?
Human wart viruses induce the formation of warts on the skin surface and can be spread by scratching, direct or indirect contact. Their existence on the skin is usually self-limiting. A more significant threat posed by Human Papillomaviruses (HPV) is their association with oncogenes and tumor development. These viruses are known to cause cervical cancer, as-well-as cancer of the vulva, vagina, penis, anus, mouth, throat and oropharynx. According to the CDC, about 14 million people are infected with HPV each year. Since HPV is readily transmitted through sexual contact, vaccination is highly recommended for preteens (both sexes). Adult individuals can also be immunized against HPV.
Current influenza vaccines are designed to provide protection against influenza ________, ___________ and one or two influenza ____ viruses.
Influenza A (H1N1), A (H3N2) and one or two influenza B viruses.
What is influenza?
Influenza is a lower respiratory tract infection that can cause severe illness and sometimes death in a variety of animals.
What is influenza caused by?
Influenza is caused by viruses in the genus Orthomyxovirus and there are four types categorized as A, B, C and D.
Influenza vaccines are made to stimulate an immune response against:
Influenza viruses.
Integration of the viral DNA into the host cell chromosome requires a second enzyme, encoded by the viral genome and carried into the host within the viral capsid; this is called _____________.
Integrase
What is the function of integrase?
Integrase picks up the DNA version of HIV, carries it through a nuclear pore into the nucleus, and then nicks a host chromosome allowing the viral DNA to be integrated.
Following adsorption, the host cell membrane ________________ taking the virus particle into the cytoplasm enclosed within a membranous bubble (vacuole or vesicle). Some enveloped viruses enter through a different mechanism called _________. What does this do? In either case, the entire virion _________ the host cell.
Invaginates (folds inward) Fusion; the envelope of the virus (being composed of cell membrane materials) fuses with the membrane surface and allows the virus to enter the host cell without being enclosed in a vacuole or vesicle. Virion enters the host cell.
What is Human herpesvirus 8?
Kaposi's sarcoma. Causes tumor formation in tissues below the skin or in mucous membranes of the mouth, nose or anus. Lesions or abnormal tissue areas appear as red, purple or brown blotches or nodules that may be quite painful.
What are Monkeypox (genus Orthopoxvirus)?
Monkeypox is a disease with symptoms similar to smallpox. A recent outbreak in the United States involved transmission from rodents to prairie dogs and from prairie dogs to humans.
The length of time HIV can remain within the human body without causing disease symptoms is variable, but the entire disease syndrome, acquired immune deficiency syndrome (AIDS) does not usually develop until ___________ or __________ after the initial infection.
Months or years
What are Mumps (genus Rubulavirus)?
Mumps is an acute, contagious disease characterized by enlargement of one or both parotid salivary glands. Entry may be via mouth or respiratory tract. Other glandular tissues may be involved.
Finally the entire viral genome is transcribed to yield a new copy of the ________ viral RNA. This RNA genome is bound to ________________, and along with other enzymes and polyproteins, is moved to the cell surface.
Original viral RNA. This RNA genome is bound to reverse transcriptase
Changes in surface antigens are ____________ responses to changes in viral genomes, i.e., genetic drift and genetic shift.
Phenotypic
Because antigenic drift and antigenic shift occur, the specific influenza serotypes used must be determined ____________________ in order to insure effectiveness. This is an ever-shifting target, and people refusing immunization actually add to the problem.
Prior to manufacture
Once the viral genome has been copied into a double-stranded DNA format, it can become integrated into the chromosome of its host to form a ____________
Provirus. Note - a human virus cannot be called a prophage because it is not a bacteriophage.
What is German measles (genus Rubivirus)?
Rubella virus. German measles or three-day measles is an acute illness characterized by a rash, mild fever, and sore throat. It is not serious except in women in the first trimester of pregnancy when it can cause congenital rubella syndrome resulting in serious abnormalities of the eye, ear, heart, genitalia, and nervous system. Infection can lead to fatality.
What are Measles (genus Morbillivirus)?
Rubeola virus. Measles is an acute, highly infectious disease characterized by a maculopapular rash, fever, and respiratory symptoms. Rapid improvement usually occurs within three days.
Human influenza viruses A and B cause ____________ in the United States almost every winter
Seasonal epidemics
There are _________ known types of hemaglutinin and ___________ known types of neuraminidase proteins so the combinations are numerous. These proteins are encoded by genes carried on ___________, each of which is composed of eight single-strands of RNA.
Sixteen Nine Viral genomes
Influenza viruses are designated as __________ or ________________ according to the hemaglutinin and neuraminidase antigens they carry, e.g., H1N1, H3N2, etc.
Subtypes or serotypes (serological types)
Although HIV can infect a variety of host cells, its primary target is ___________________________ Infection of a few host cells will leave some viral proteins on cell surfaces; however, this may or may not trigger an immune reaction (antibody production) sufficient for detection or diagnosis.
T4 lymphocytes (cells called helper-T cells or T-helper cells). .
What are Caliciviruses (Caliciviridae)?
The Caliciviruses have single-stranded RNA (positive- sense RNA) genomes and are non-enveloped.
What are Deltaviruses (Deltaviridae)?
The Delta viruses have one strand of negative-sense , single- stranded RNA as their genome.
What is Flaviviruses (Flaviviridae)?
The Flaviviruses have single-stranded RNA genomes (positive-sense RNA) and are enveloped. Many are transmitted by arthropods.
What is Hepadnaviruses (Hepadnaviridae)?
The Hepadnaviruses have double-stranded DNA genomes and are enveloped.
What is a Hepatitis E virus?
The Hepatitis E virus (HEV) causes symptoms indistinguishable from hepatitis A including malaise, anorexia, abdominal pain, joint pain and fever.
What is Picornaviruses(Picornaviridae)?
The Picorna viruses have single-stranded RNA genomes (positive-sense RNA) and are nonenveloped.
After HIV enters the host cell, two protein coverings, the ____________ and an outer layer called a ____________, are removed. The process involved is called ____________ and involves enzymes present within the host cell cytoplasm. After the viral genome is released within the cytoplasm a type of enzyme called ____________________, also contained within the viral capsid, causes the viral RNA to be reverse transcribed into DNA as the RNA is degraded. The single-stranded DNA formed is then replicated (also by reverse transcriptase) to form a __________________.
The capsid and an outer layer called a matrix, are removed. The process involved is called _______________ and involves enzymes present within the host cell cytoplasm. Reverse transcriptase (an RNA-dependent DNA polymerase) DNA duplex.
What is a Norwalk-like virus (genus Norovirus)?
The genus Norovirus has recently been assigned to a group of viruses known as Norwalk-like viruses that are the most common cause of infectious gastroenteritis (often referred to as the 24-hour flu).
What is Herpesviruses (Herpesviridae)?
The herpesviruses are double-stranded DNA viruses with nucleocapsids and envelopes. All have a tendency to go into a latent stage following primary infection, and to reactivate at later intervals.
What is Human Papovaviruses (Papoviridae)?
The name for this virus group is derived from three words, papilloma, polyoma, and vacuolating viruses. These are double-stranded DNA viruses with naked capsids.
What is Paramyxoviruses (Paramyxoviridae)?
The paramyxoviruses are single-stranded RNA viruses with nucleocapsids and envelopes. They tend to cause fusion of host cells with the resulting formation of giant cells.
What is Poxviruses (Poxviridae)?
The poxviruses are double-stranded DNA viruses with envelopes. They tend to be large, complex and brick-shaped.
What is Togaviruses (Togaviridae)?
The togaviruses are single-stranded RNA viruses (positive- sense RNA) with envelopes. Many are transmitted by arthropod vectors, but some can be transmitted by the respiratory route.
Before the genome of an animal virus may be activated, the protein capsid must be removed. This process is referred to as _____________ and requires the activity of cellular enzymes.
Uncoating
What is Human herpesvirus 3 (genus Varicellovirus)?
Varicella-zoster virus. Human herpesvirus type 3 causes chickenpox (varicella), a mild highly contagious disease of children, and shingles (zoster) a sporadic, incapacitating disease of adults.
What is Smallpox (genus Orthopoxvirus)?
Variola virus. Smallpox is transmitted through the respiratory system, but infects various internal organs before entering the bloodstream and reaching the skin. Viral replication causes the formation of lesions on the skin surface often resulting in scars. Smallpox was declared eradicated from the world in 1979, but remains a potential agent for bioterrorism.
Vesicles carrying the resulting glycoproteins (gp120 and gp41) leave the Golgi, move to the ___________ and fuse with the ______________ depositing the viral glycoproteins on the __________. Viral genes encoding capsid/matrix polyproteins and the enzymes needed for viral function are transcribed into _____________ that is translated by host ribosomes free in the cytoplasm.
Vesicles carrying the resulting glycoproteins (gp120 and gp41) leave the Golgi, move to the *cell surface* and fuse with the *cell membrane* depositing the viral glycoproteins on the *outside.* Viral genes encoding capsid/matrix polyproteins and the enzymes needed for viral function are transcribed into *mRNA* that is translated by host ribosomes free in the cytoplasm.
Viral glycoproteins identified as gp120 and gp41 interact with specific receptors located on the surfaces of T4 lymphocytes and other related cells. These receptors are the CD4 (cluster of differentiation 4) membrane markers characteristic of T4 cells and CCR5 (chemokine coreceptor type 5) proteins. The viral gp120 binds to CD4 first, and then to the CCR5, then gp41 binds with the cell membrane and causes the viral envelope and the cell membrane to fuse. Some individuals carry a mutant version of the CCR5 gene called Delta 32 (a 32-base deletion mutation) and consequently cannot be infected by certain strains of HIV.
Viral glycoproteins identified as gp120 and gp41 interact with specific receptors located on the surfaces of T4 lymphocytes and other related cells. These receptors are the CD4 (cluster of differentiation 4) membrane markers characteristic of T4 cells and CCR5 (chemokine coreceptor type 5) proteins. The viral gp120 binds to CD4 first, and then to the CCR5, then gp41 binds with the cell membrane and causes the viral envelope and the cell membrane to fuse. Some individuals carry a mutant version of the CCR5 gene called Delta 32 (a 32-base deletion mutation) and consequently cannot be infected by certain strains of HIV.
Influenza type C causes ___________
While influenza type C causes only mild disease
What are the types of Paramyxoviruses (Paramyxoviridae)?
a. Measles (genus Morbillivirus) b. Mumps (genus Rubulavirus)
What are the types of Poxviruses (Poxviridae)?
a. Smallpox (genus Orthopoxvirus) b. Cowpox (genus Orthopoxvirus) c. Monkeypox (genus Orthopoxvirus)
