Persistence of viral infections

Question 1

What causes a viral infection to be persistant?

Answer 1

strategy not to kill the cell it infects –> virus survival and resistance to host defense mechanisms

Question 2

What are 4 patterns of viral infection?

Answer 2

1. acute viral infection followed by viral clearance
2. Acute viral infection followed by latent infection and periodic reactivation
3. Acute viral infection followed by chronic infection
4. Slow chronic infection

Question 3

What are 3 mechanisms of viral persistence?

Answer 3

1. Ability to infect host cells without being cytopathic
2. Long-term maintenance of viral genome
3. Inhibition of detection and elimination by the host immune response

Question 4

What are the three ways a virus can infect host cells without being cytopathic?

Answer 4

1. Infection of nonpermissive cells (sensory neurons)
2. Cycling or smoldering of low number of permissive cells: only infect small # of cells
3. Generation of viral variants: small plaque mutants, temperature sensitive mutants, defective interfering particles

Question 5

How is there long term maintenance of viral genome?

Answer 5

1. Integration into host chromosomes (parvovirus)
2. Episomal state w/o viral genome replication (BHV)
3. Episomal state with viral genome replication

Question 6

What things may cause alpha herpesvirus activation?

Answer 6

Immunosupression
Stress
Hormonal changes
Nerve damage
UV exposure

Question 7

What is the Papillomavirus life cycle?

Answer 7

Infects basal layer of skin
virus replicates only when basal cells differentiate into keratinized cells of stratum spinosum and granular layer of epithelium

Question 8

What is required for adeno-associated virus replication?

Answer 8

coinfection with adenovirus or herpesvirus

Question 9

What is a provirus?

Answer 9

RNA genome converted into dsDNA