Papoviridae

Question 1

____ is an oncogenic DNA virus

Answer 1

Simian Virus 40

• induces primary brain and bone cancers, malignant mesothelioma, lymphomas in lab animals
• epidemiological evidence shows that SV40 likely does not cause cancer in humans

Question 2

SV40 genome

Answer 2

• early region: expressed prior to onset of viral DNA replication, encodes viral tumor antigens (T antigens)
• late region: encodes viral capsid proteins

Question 3

Roles of viral T antigens

Answer 3

• alter and/or recruit specific host cell proteins to participate in virus production
• block cellular antiviral defense systems
• participate directly in viral replication

Question 4

Large T antigens are _____ and are required to _______

Answer 4

DNA helicases; replicate viral DNA

Question 5

3 mRNA expressed by SV40

Answer 5

• large T antigen
• small t antigen
• tiny t antigen

Question 6

All T antigens encoded by a virus have a common _______

Answer 6

Amino-terminal domain

Question 7

Only _____ and _____ are essential for productive infection and viral tumorigenicity

Answer 7

Large T antigen (SV40) and large/middle T antigens (PyV)

Question 8

Small t antigens contribute to _______

Answer 8

Both infection and transformation

Question 9

Budgerigar fledgling disease virus

Answer 9

Isolated from papillomas on legs of European finches and in proliferative lesions on the head and eyelids of African grey parrots

• murine polyomavirus
• has oncogenic potential

Question 10

Does BFD infect Budgies?

Answer 10

No, but can infect other species (adults are carriers)

• in baby budgies it causes generalized infection –> lack of down feathers, retarded growth of tail and feathers, distended abdomen
• dehydration leads to a reddish skin coloration

Question 11

Post mortem examination of BFD

Answer 11

• hydropericardium
• cardiomegaly
• hepatic necrosis
• enlarged hyperemic kidneys
• karyomegalic inclusions on histopath

Question 12

Morphology

Answer 12

Nonenveloped, isometric nucleocapsids (round)

• 40-44 nm in diameter
• icosahedral symmetry
• incomplete viral particles present as empty capsids

Question 13

Nucleic acid

Answer 13

10-13% nucleic acid content in virions, with one molecule of circular dsDNA

Question 14

Human papillomaviruses all target _______

Answer 14

Epithelial tissues for infection

- productive life cycle is linked to epithelial differentiation

Question 15

Papillomaviruses establish their genomes as _______

Answer 15

Multicopy nuclear episomes

• viral DNA is replicated with cellular chromosomes
• daughter cell migrates away from basal layer to undergo differentiation

Question 16

What property allows papillomavirus to persist for several decades, or until the immune system clears the infection?

Answer 16

Virion production is limited to differentiated cells

Question 17

____ and ____ genes encode for oncoproteins

Answer 17

E6 and E7

• target Rb and p53
• facilitate stable maintenance of episomes and stimulate differentiated cells to reenter S phase

Question 18

Papillomavirus morphology

Answer 18

Non-enveloped

• virions are of one type of particle only, or more than one type of particle
• icosahedral symmetry

Question 19

Papillomavirus genome

Answer 19

One molecule of circular, dsDNA

Question 20

Why are papillomaviruses good models for studying molecular evolution of DNA?

Answer 20

Large number of isolates are available that exhibit genomic diversity and host species and tissue specificity
- phylogeny suggests that some branches of papillomavirus evolution are restricted to particular target tissues = long-term papillomavirus-host coevolution has occurred

Question 21

What is the first virus isolated from the order Sirenia?

Answer 21

Trichechus manatus latirostris

• novel papillomavirus found in Florida manatee
• was one of the first wart viruses to evolve