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49 Cards in this Set

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What is a capsid?
A symmetric protein shell that encloses a virus' nucleic acid.
What are the 2 functions of a capsid?
1. To protect the nucleic acid.
2. To aid in infection of host cells
what is the name of a
capsid + enclosed nucleic acid?
Nucleocapsid
How is a Nucleocapsid different from a virion?
A virion can be simply a nucleocapsid, or that with an envelope as well. The complete infective virus particle.
Give 3 examples of viruses that have a virion = nucleocapsid:
1. Adenovirus
2. Papovavirus
3. Picornavirus
Give 2 examples of viruses that have an envelope in addition to the nucleocapsid:
1. Herpesvirus
2. Myxovirus
What is a CAPSOMERE?
A cluster of polypeptides which form a capsid on isometric virus particles.
How are capsomeres visible?
With electron microscopy; they are morphologic units.
What are Structural units of a virus?
The basic building blocks of the capsid - may be individual polypeptides.
So how do structural units and capsomeres differ?
Capsomeres are clusters of polypeptides, where struct. units are individual pp's.
What is a PSEUDOVIRION?
A particle that looks like an ordinary virus, but actually contains the wrong nucleic acid - that of the host cell.
How do pseudovirions function compared to normal viruses?
They cannot replicate.
What is PRIMARY nucleic acid structure?
the base sequence in the acid chain.
What is SECONDARY nucleic acid structure?
the spatial arrangement of the complete chain - tells whether it is ss or ds.
What is the TERTIARY strcture?
Fine spatial detail; supercoils, deletions, gaps, cations, etc.
What is Transcription?
Transfer of Nucleic acid information to mRNA.
What is Translation?
Using the mRNA to build a specific amino acid sequence and protein!
When you picture a virus, what do you see?
---Nucleic Acid Center---
---Capsomeres together making up the Capsid Coat---
Envelope Surrounding the Nucleocapsid.
What is an envelope made out of?
Lipid material from the host cell's membrane.
What enzymes are contained in viruses along with the genome?
Replicative enzymes --> NOT oxidative enzymes; that's what the host cell is for!
What acronym stands for the 6 steps in viral infection?
APURAR
What does APURAR stand for?
A = Attachment
P = Penetration
U = Uncoating
R = Replication/Reproduction
A = Assembly
R = Release
How do viruses attach to host cells?
With specificity, like an Ag-Ab reaction.
What are 5 cellular responses to a viral infection?
1. Cell injury
2. Proliferation
3. Inclusion production
4. No visible change
5. Giant cell formation
What is the acronym for cell response to infection?
CPING... like shhh the cell is sleeping
-What are some indicators of cell injury?
-What is another name for this?
Ballooning, vacuolization, death.
Cytopathic effect, CPE.
What are the 4 main contributors to CPE?
1. Cellular metabolism diversion
2. Lysozomal damage
3. Cell membrane damage
4. Toxic viral products
Why is diverting cell metblsm so cytopathic?
Intended to keep Na/K pumps working to keep K inside the cell and Na out; if this fails, the cell breaks down.
How does the cell membrane contribute to CPE?
During penetration the virus leaves antigenic fragments which cause immunological damage later.
What is the most common type of cell proliferation, and what virus is associated with it?
Liver cell carcinoma.
Chronic Hepatitis C.
What are 4 main contributors to viral pathogenicity?
1. Portal of Entry
2. Local replication/spread
3. Dissemination
4. Shedding sites
What are common portals of entry for viruses?
Oral, anal, respiratory, venereal.
What is viral TROPISM? What is a major determinant in this?
-Viral affinity for specific body tissues.
-Important factor is presence of receptor for specificity.
What are 2 alternate ways of viral dissemination?
1. Viremic
2. Neural
What is Viremic spread of infection?
Via the lymphatics, to enter the circulatory system. Virus may infect white cells as vehicle.
What is neural spread? What virus exhibits it?
Via the neurons/ganglia; Rabies.
What symptoms are seen in the incubation period of infection?
None - its usually asymptomatic.
List 4 ways to RESIST viruses:
1. Lack the receptor
2. Develop Antibodies
3. T-Cells
4. Interferon
What two specific ways do antibodies neutralize viruses?
1. By binding virus receptors, Ab blocks it from binding target host cells!
2. By binding virus, the complex can activate ADCC or complement-mediated lysis.
What antibody classes participate in viral defense?
IgM, IgG, and IgA.
What role does cell-mediated immunity play in fighting viral infections?
T cells are very important, as well as cytokines.
Which leukocytes can recognize and kill infected host cells?
T-cytotoxic cells
NK cells
Macrophages
Which leukocytes produce antiviral cytokines?
T-helper cells
NK cells
Monocytes
What is the main purpose of the nonspecific immune response to viruses?
To prevent proliferation and replication of the disease.
What is the main player in this nonspecific response?
When are they seen at work?
-Interferon and NK cells.

-Seen early in the acute phase.
What is the main purpose of the specific immune response?
-To eliminate virus at the END of the acute phase, and develop specificity to prevent future infections.
HOw are antibodies and interferon SIMILAR?
Both are made of protein.
What are Ab and INF each specific FOR?
Antibody: virus
Interferon: host
What are the 6 stages of Illness in viral infections?
1. Incubation
2. Prodrome
3. Onset
4. Acute Phase
5. Recovery
6. Convalescent