Section 6.2

Question 1

2) Parvoviruses: (genome)

Answer 1

linear ssDNA
*smallest animal DNA viruses

Question 2

3) circoviruses:

Answer 2

Circular ssDNA
* similar to geminiviruses that infect plants

Question 3

4) papillomaviruses:

Answer 3

Circular dsDNA
*examples: HPV: warts, infection can lead to cervical cancer

Question 4

5) polyomaviruses:

Answer 4

circular dsDNA
*example SV40

Question 5

6) Adenoviruses

Question 6

All the following viruses reply on:

Answer 6

Cellular RNA and DNA polymerase machinery for replication/transcription

Question 7

Parvoviruses replicate in _____

Answer 7

cells with activated cell cycles (cuz they can’t activate a cell on their own)

Question 8

parvoviruses clinically:

Answer 8

B19 infection: erythema infectiosum “fifth disease”

Question 9

parvoviruses genomic content

Answer 9

very simple 2 genes

1 gene encoding non-structural proteins that interact with things inside the cell for the virus to replicate (generated by diff RNA splicing)

1 gene coding structural (capsid) protiens

Question 10

parvovirus structure:
(capsid and what’s inside it)

Answer 10

small naked icosahedral capsid (very stable)

• inside capsid: linear ssDNA folded in the ends into T structures that allow initiation of DNA replication

Question 11

Parvoviruses can only infect cells in the __-________ that are actively replicating their DNA

(cuz its viral genomic DNA can’t act as a template for transcription and they need host cell DNA to replicate)

Answer 11

S-phase

Question 12

parvoviruses are now used as potential

Answer 12

oncolytic viruses; kill cancer cells
gene therapy vectors: AAV deliver genes

Question 13

parvoviruses diversity fun facts: (3)

Answer 13

• high mutation rates*
  *Make lots of ERRORS (rdrp don’t proof read)
• also very frequently engaged in recombination when more than one strain co infects a host
• most of its diversity are viruses that don’t infect humans

Question 14

Veterinary parvoviruses: (2)

Answer 14

feline panleukopenia parovirus (FPV)
canine provirus (CPV)

Question 15

feline panleukopenia parovirus (FPV)

Answer 15

known to infect cats, replicates in bone marrow and lymph nodes (leukopenia) and intestine (causing hemorrhagic enteritis)

Question 16

canine provirus (CPV)

Answer 16

identified in dogs and rapidly spread around the globe (high mortality similar to FPV)

Question 17

CPV has been characterized and found to originate from a cross species transmission of FPV to dogs

Answer 17

original CPV only infects dogs
now dominant CPV infects both dogs and cats

Question 18

What led FPV to become CPV

Answer 18

two substitutions in the capsid proteins allowed for transmission to dogs

several other mutations allowed infection of both dogs and cats

Question 19

ANOTHER veterinary parvovirus

Answer 19

Aleutian mink disease virus (AMDV)

Question 20

Aleutian mink disease virus (AMDV)

global spread

problem where

replicates where

facts (transmission and stability)

how is it lethal

Answer 20

globally distributed due to transport of infected animals before recognition as infectious disease

is a major problem for farms

replicates in macrophages causes chronic infection (never cleared)

highly transmissible spreads quickly

very stable in environment (super compact virions)

virus antibody complexes block arteries and deposit in tissue therefore lethal

Question 21

intersting about the evolution of AMDV

Answer 21

the two genes (structural and non structural) were evolving differently and at diff rates
(sturctural ones were evolving slower than non structural ones)

Question 22

Normal evolution

Answer 22

structure (capsid) protiens evolve quick due to immune pressure

non-structural don’t evolve, are under strong selection to maintain function in host cell

Question 23

Therefore AMDV displays:

Answer 23

antibody dependant enhancement (antibodies stimulate infection, help the virus get taken up by host cell)
Therefore, vaccine makes it worse and second infection is worse cuz u have antibodies

selection acts to maintain immune epitopes

Question 24

Polyomaviruses: (genome and structure)

Answer 24

circular dsDNA wrapped In histones making nucleosomes (mini chromosomes) packaged inside capsid

Question 25

Polyomavirus infection effects:

Answer 25

widespread in humans but usually doesn’t cause overt symptoms and presists as long term infection

Only causes skin cancer in immunocompromised

Question 26

Polyomavirus example:

Answer 26

SV4 = simian virus 40

Question 27

SV40 accidentally spread how?

Answer 27

contaminant in polio vaccine ( was in the mockey cell culture used and was not innactivated in the process of inactivating polio)

Question 28

productive infection of SV40 causes:

Non-productive infection of SV40 causes:

Answer 28

productive: cell lysis and virion release

non-productive: happens in non-permissive cells where the genome doesn’t replicate and no virions form
(can transform cultured cells into tumour cells)
- but, the virus protiens that are called t-antigens that expressed and stimulate cell division and lead to cellular transformation (if it integrates to genome, continus T-Ag expression

Question 29

Cellular transformation by SV40

Answer 29

(in susceptible but non permissive cell)

• genome goes inside and makes T-Ag

small T-Ag activates the MAPK pathway

medium T-Ag activates cell cycle through Src pathway

Large T-Ag interacts with diff cellular protiens p53 and rb that effect cell cycle

Question 30

Adenoviruses structure:

Answer 30

icosohedral structure with fibre projections at 12 vertices that interact w cell receptors

Question 31

Adenovirus genome:

Answer 31

linear dsDNA (similar to phage)
— has terminal repeats
—- has a protein attached to 5’ end of ds molecules (so 2 in total)

Very Important for DNA replication

Question 32

Adenoviruses led to discovery and noble prize win of ______

Answer 32

RNA splicing

same region makes many diff RNAs and protiens

Question 33

Adenoviruses and “the end problem”:

Answer 33

all linear DNA genomes have end problem cuz they need a primer to initiate replication on lagging strand
- to prevent loss of DNA bits each replication

Question 34

how do parvoviruses linear dsDNA get rid of “the end problem”

Answer 34

folds itself to make DNA hairpins

Question 35

how do herpesviruses linear dsDNA get rid of “the end problem”

Answer 35

circularize their genome and do RCR

Question 36

how do Adenoviruses linear dsDNA get rid of “the end problem”
4 STEPS

Answer 36

use a special protein (terminal protein: TP) that acts as primer for DNA replication (recruits DNA pol) at inverted terminal repeats

1- Starts as Pre-TP that brings viral DNA pol to terminus of the DNA genome and a C base attaches to it where DNA synthesis begins

2- the displaced strand is covered with a viral DNA binding protein DBP

3-after completion we have a full DNA duplex and pTP gets cut by a protease to become TP

4- displaced strand reaneals using the repeated inverted sequences

5- this process repeats (2 full dsDNA genomes after each replication)