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Path: Virology > Viral Replication > Flashcards

Viral Replication Flashcards

1
Q

What determines tropism HIV?

A

Receptor-binding characteristics

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2
Q

What’s the receptor for HIV?

A

CD4 and chemokine co-receptor

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3
Q

What is part of HIV binds to CD4?

A

Envelope protein (gp120)

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4
Q

What does EBV glycoprotein bind to on the host cell?

A

CD21

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5
Q

What is required for membrane fusion?

A

2 membranes drawn close together, followed by membrane disruption

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6
Q

How does influenza penetrate the host cell?

A

Influenza virus ptcle endocytosed by cell and endosome acidified

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7
Q

Why is the eclipse phase so-called?

A

No virus particles are present in the host cell

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8
Q

What occurs during eclipse phase?

A

Virus ptcle disassembled
Virus genome being replicated
Virus proteins being made

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9
Q

Why are nucleic acid polymerases needed early?

A

To transcribe/replicate virus genome

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10
Q

Why are capsid proteins needed late and in higher amounts?

A

During infection

Build new virions

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11
Q

Why is virus nucleic acid synthesis highly specific?

A

To recognise specific sequences/structures, ie origins of replication

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12
Q

What is the min requirement for protein coding?

A

Virus-specific nucleic acid polymerase

Virus coat proteins

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13
Q

How may a virus acquire nucleic acid polymerases?

A

Provide it’s own

Evolve to utilise one from host

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14
Q

What is the unifying theme of virus replication strategies?

A

Need to translate mRNA on host cell ribosomes

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15
Q

What is different about the replication influenza compared to other negative strand RNA viruses?

A

Replicates in nucleus therefore requires nuclear functions (rather than cytoplasmic functions)

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16
Q

What is the purpose of reverse transcriptase in replication retroviruses?

A

Copies positive strand RNA into dsDNA intermediate

17
Q

What is a general feature of temporal control of virus gene expression?

A

Viral DNA polymerases required early in cycle; capsid proteins required late in cycle

18
Q

What is a polyprotein?

A

Single large polypeptide

19
Q

How is a polyprotein post-translationally cleaved?

A

By proteases into several smaller polypeptides

20
Q

For which types of viruses is post translational cleavage of polyproteins an important feature?

A

RNA viruses

21
Q

Which elements of the post translational cleavage polyproteins are potential targets for chemotherapy?

A

Proteases: responsible for cleavage and virus-specified

22
Q

How do retroviruses use splicing?

A

Place coding region for some of their proteins at 5’end of mRNA so that ribosomes encounter this 1st as they scan from the 5’ end

23
Q

How is the HIV envelope protein gp160 made?

A

Splicing by placing coding region at 5’end of mRNA

24
Q

What is HIV gp160 proteolytically cleaved into?

A

gp120 and gp41

25
Q

What type of assembly occurs for capsomer helical viruses?

A

Addition protein subunits around nucleic acid molecule

26
Q

What is an example of virus with a helical capsid?

A

Tobacco mosaic virus (TMV)

27
Q

How are icosahedral viruses assembled?

A

Proteins subunits formed alone; nucleic acid inserted into ‘empty’ capsids to form nucleocapsid

28
Q

What is latent infection?

A

Viruses infect cell by existing in a quiescent state

29
Q

Examples viruses capable establishing latent infections?

A

Retroviruses and herpesviruses

30
Q

Risk of latently infected virus integrating into germ cell?

A

Enables vertical transmission of virus to next host

31
Q

What is an episome?

A

Quiescent viral DNA which exists as an extrachromosomal circular molecule

32
Q

What is reactivation?

A

Switch from latent infection to productive cycle

33
Q

When may reactivation occur?

A

Changes in transcription factors allow recognition of viral promoters

Path: Virology (7 decks)

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