Intro to Virus

Question 1

Virus are …. pathogens

Answer 1

Obligate intracellular (can only replicate inside host cell)

Question 2

Virus are ……….. and have icosahedral, ……. and complex structure

Answer 2

non-cellular
helical

Icosahedral: 20 faces, each an equilateral triangle - either DNA/RNA
Helical: protein binds around DNA/RNA in a helical fashion
Complex: neither icosahedral or helical

Question 3

Most viruses have a specific host range and only infect specific host cell types

Answer 3

Tissue tropism

Question 4

Virus families can be classified according to:

Answer 4

Genome structure
Virion shape / symmetry
Presence / absence of envelope
Mode of replication

Question 5

vertical route

Answer 5

at birth, through breast feeding

Question 6

Coinfection of human and animal or bird strains in one organism may lead to …… and ….. of a new strain

Answer 6

recombination
generation
= resistance

Question 7

Consequences of viral infection

Answer 7

Clearance of virus
Chronic infection
Latent infection
Transformation

Clearance of virus (with no, short or long term immunity)
Hepatitis C (no lasting immunity)
Measles (long term immunity)

Chronic infection
HIV, hepatitis B, hepatitis C

Latent infection (HSV, VZV)

Some lie dormant in cell - full viral genome is retained in the host cell, - expression is restricted - few viral Ag and no viral particles are produced.
Reactivation more likely to occur and more severe in Immunocompromised

Transformation (long term infection with altered cellular gene expression)
Epstein-Barr Virus, Human Papillomavirus

Question 8

Mechanisms that can cause cancer:

Answer 8

cell cycle control (driving cell proliferation)
apoptosis (prevention of programmed cell death)
Reactive oxygen species mediated damage

(some persistent viral infections can cause persistent inflammatory processes which lead to cancer via reactive oxygen species

Question 9

lymphomas caused by

Answer 9

EBV

Question 10

Cervical, anal, oropharyngeal cancers caused by

Answer 10

Human Papillomavirus

Question 11

hepatocellular carcinoma caused by

Answer 11

Hepatitis

Question 12

antivirals may be used for:

Answer 12

Prophyaxis (to prevent infection)
Pre-emptive therapy (when evidence of infection/replication detected, but before symptoms are apparent)
Suppressive therapy (to keep viral replication below the rate that causes tissue damage in an asymptomatic infected patient
overt (open - symptoms can be seen)