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Microbio. (MEDI2003) > Virus > Flashcards

Virus Flashcards

1
Q

Why is it not possible to grow virus in artificial media?

A

bc viruses are obligate intracellular parasites - requires a host (cell) to replicate in

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2
Q

List the main structures of an enveloped virus.

A
  • capsid (protein coat) made up of capsomeres (w/ nucleic acid inside)
  • envelop (membrane)
  • protein projections (for attachment on host cell)
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3
Q

What are the main functions of structural proteins?

A

make up the viral structure
> facilitate entry into host cell (protein projections)
> protect viral nucleic acid (capsid)
> stabilisation: keep structure tog.

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4
Q

What are the main types of viral capsid symmetries & e.g? (3)

A
  • Icosahedral (cubic) e.g. herpesvirus
  • Helical: spiral e.g. coronavirus
  • Complex: neither icosahedral or helical e.g. bacteriophage T4
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5
Q

What is the main classification difference b/w parvovirus & picornavirus?

A
  • Parvovirus: Nucleic acid is DNA

- Picornavirus: RNA

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6
Q

List the Baltimore classes of virus

A

Class:

1: dsDNA
2. ssDNA
3. dsRNA (segmented)
4. ssRNA +sense (already an mRNA)
5. ssRNA -ve sense (needs to be converted to +ve)
6. ssRNA +ve sense w/ dsDNA intermediate (before replication). MEANS: RNA + reverse transcriptase => DNA => mRNA
7. dsDNA w/ +ve sense (ssDNA). undergo reverse transcriptase => mRNA

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7
Q

List the main replication events of a virus

A
  1. Attachment to specific host cell’s receptor on membrane
  2. Penetration: enter host cell & “uncoats” capsid
  3. Replication of viral genome: production of viral mRNA
    & early viral proteins (non-structural> assist in replication)
  4. Production of late viral (structural) proteins
  5. Assembly of the progeny virions
  6. Release of virions
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8
Q

What’s the diff. b/w lytic & lysogenic cycles?

A
  • Lytic: lysis of host cell to release viral particles

- Lysogenic: viral genome integrated in host chromosome (- prophage). May enter lytic cycle

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9
Q

Describe the 2 mechanisms viruses cause disease

A
  1. Replication w/in host cell => damage in cell

2. Damage form host defenses in its attempt to remove virus from infected cells

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10
Q

Describe the host factors that are important in viral infections

A
  • Appropriate receptors on surface: determine if virus gets entry
  • Internal cellular environment suitability: molecular machinery for replication (@ S phase) is present, & physical environment is suitable
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11
Q

What is “CPE” and how does it occur?

A

Cytopathic effect: is the effect of viral replication on host cell. It occurs since host cell’s function will change = detectable

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12
Q

What is the main action of HIV as a result of AIDS?

A

T helper cells have CD4 receptor - HIV binds to => destroys T helper cells => destroy humoral/adaptive immune resp.

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13
Q

List the events of a viral infection

A
  1. Invade host
  2. Replicate in cells of inoculation
  3. Overcome local defences
  4. Spread to other cells & other areas
  5. Replicate again
  6. Exit from host in lrg no. to infect another host
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14
Q

How can viruses evade the immune system? (7)

A
  • poorly immunogenic (stimulate IR)
  • Not displaying enough of their antigen on the surface
  • Inactivate B cells, T cells, macrophages
  • Interfere w/ expression/transport of MHC proteins
  • excess antigen production > neutralise antibodies
  • mutations - change antigens of virus
  • infection to foetus before immune system has developed
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15
Q

What is the incubation time for measles?

A

13-14 days

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16
Q

What does “recruitment” mean in relation to prion disease?

A

When a normal protein gets in contact w/ an abnormal protein => that normal protein will be converted into an abnormal conformation

17
Q

*Describe the types of clinical manifestations (signs & symptoms) resulting from viral infections.

A

*skin rashes, low immunity, transformation of cells, inclusion bodies, syncytia, lysis

18
Q

Describe the basic structure of a Herpes virus.

A
  • Linear dsDNA
  • Nucleocapsid
  • Tegument (proteins)
  • Lipid envelop
  • envelop proteins
19
Q

What does VP16 do in Herpes virus infections?

A

VP16 protein (in tegument) activates a genes(/phase) but requires host’s proteins Oct 1 & HCF (human factor C)

20
Q

Once Herpes virus is in the cell, describe phases of gene expression

A
  • 1 phase activates the next & inhibits the previous
    1. a-phase: a gene (regulator) activated by VP16 protein
    2. B-phase: B gene -> (early) proteins for DNA replication
    3. Y-phase: gamma gene -> (late) structural proteins
21
Q

*What are the differences between “chicken pox” and “shingles”?

A

*“chicken pox” is an acute infection while “shingles” is a latent infection

22
Q

What are the functions of the Haemagglutinin (H) and Neuraminidase (N) surface protein spikes on the influenza virus?

A
  • Haemagglutinin: binds to sialic acid on mucous memb. & RBC, & causes ENTRY in host cell
  • Neuraminidase: release virions (EXIT out of cell)
23
Q

What’s the genome of influenza virus & Where in the host cell does the genome replicate?

A
  • (Class 5) ss(-) RNA segmented genome

- repicate in nucleus

24
Q

What are “Antigenic Drift” and “Antigenic Shift”?

A
  • Drift: minor changes in H & N bc host selection of mutants (mutations freq. in RNA bc no proofreading)
  • Shift: major change in H & N from recombination b/w animal & humans bc Hi chance of reassortment of segmented RNA (e.g. when 2 diff. virus infect the same cell genes can be interchanged = new cell)
25
Q

Entry of a virus in mucous memebranes is easy/difficult?

A

Esay bc epithelial cells (line mucosal lining) are thin: can pass through/ absorbed w/ ease

26
Q

How do DNA viruses replicate?

A 
General idea in class 1 (& 2): (ssDNA->) *dsDNA  -> mRNA 
Class 7: make full dsDNA (from partial dsDNA & ssDNA) -> mRNA -> rvs transcriptase = partial DNA to package
27
Q

How do RNA viruses replicate?

A
  • need to end up w/ +ve sense aka mRNA
    Class 3: -ve sense in ds RNA -> +ve (mRNA)
    C5: -ve ssRNA -> +ve (mRNA)
    C6: ssRNA -> rvs transcriptase = dsDNA -> lysogenic -> transcribe to mRNA

Microbio. (MEDI2003) (16 decks)

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