Parvovirus (Dr. Frappier)

Question 1

Types of parvovirus

Answer 1

Autonomous parvoviruses
Dependovirus (AAV)

Question 2

How does B19 affect our body?

Answer 2

infect RBD precursors —> less RBD produced

Question 3

how does fifth disease manifest itself?

Answer 3

build up of immune complex
–> slapped cheek

Question 4

Features of genome for parvovirus

Answer 4

linear ssDNA

Question 5

Difference between genome of autonomous viruses and AAV

Answer 5

i) location of encapsidation
-> on the one complementary to mRNA for auto
-> either strand (50% chance) for AAV
ii)sequence at both ends
-> different for auto
–> inverted terminal repeats for AAV

Question 6

Parts within coding region of parvovirus

Answer 6

i) one for capsid proteins (2-3)
ii) others encode non-structural proteins needed in viral replication

Question 7

How does parvovirus enter cell?

Answer 7

bind cell surface receptor
–> endocytosis

Question 8

How does virion enter nucleus of cell?

Answer 8

thru nuclear pore (small size allows that)

Question 9

What happens after virion enter nucleus?

Answer 9

i) DNA comes out of virion with capsid intact (AAV)
ii) release DNA from virus (uncoating) occur in nonpermissive cells

Question 10

What must happen before viral genes of parvovirus can be expressed?

Answer 10

ssDNA copied to dsDNA

Question 11

Features of replication oin autonomous parvoviruses

Answer 11

i) wait for cells to enter S phase to replicate
ii) cannot induce host DNA synthesis
iii) DNA remains in capsid until replication starts

Question 12

what viruses can be helper virus for AAV?

Answer 12

usually adenovirus, sometimes herpesviruses

Question 13

How does adenovirus help AAV?

Answer 13

stimulate AAV replication
–> affect expression of cellular and AAV genes

help is indirect by altering cellular protein levels

Question 14

What is used for DNA replication of parvovirus?

Answer 14

cellular DNA polymerase (delta one is crucial)

Question 15

Describe steps for AAV DNA replication

Answer 15

i) single stranded virion forms hairpin
ii) elongates 3’ end with help of DNA polymerase
iii) nick introduced, elongate from nick
iv) separate strands and form hairpins for next round

Question 16

Proteins used in automous parvoviruses and AAV in DNA replication

Answer 16

autonomous: NS1
AAV:Rep 68/78

Question 17

similarities between proteins used in DNA replication in both types of parvovirus

Answer 17

i) able to recognize specific sequence in viral DNA
ii) help cleavage of replicative intermediates at specific sites
iii) covalently linked to 5’ end of DNA after cleavage
iv) have DNA helicase and ATPase roles
v) additional roles to prevent cells form leaving S phase + activate viral transcription

Question 18

When is NS1 or Rep68/78 removed from DNA?

Answer 18

before packaging in virions

Question 19

Difference between NS1 and Rep68/78

Answer 19

NS1 only cleave one end, while Rep68/78 cleave both ends
–> one strand is preferentially packaged in autonomous

Question 20

Where does DNA of AAV integrate in latent AAV infection?

Answer 20

specific site in chromosome 19

Question 21

Function of Rep68/68 in latent AAV infection

Answer 21

link AAV terminal to cellular integration site

Question 22

How long is AAV DNA remain integrated?

Answer 22

until cell is infected with helpervirus

Question 23

What happens after helpervirus comes in?

Answer 23

induce expression of lots of Rep 68/78 proteins
–> excise AAV DNA from cellular + virus production

Question 24

What happes in latent AAV infection?

Answer 24

i) AAV DNA released in nucleus
ii) copied to make dsDNA
iii) little Rep68/78 made
–> DNA integrate into cellular DNA at chromosome 19