Immune responses to viruses Flashcards

1
Q

What is a virus?

A

an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy and is able to multiple only within the living cells of a host

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2
Q

What is the programme viruses have to self-replication and multiplication?

A

gene expression; genome replication; virus assmebl; virus release and transmission

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3
Q

how are viruses classified?

A

Baltimore classificaation: type of genoma and method of replication

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4
Q

Give examples of dsDNA viruses?

A

herpes; poxvirus; adenovirus; papillomavirus

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5
Q

Give examples of ssDNA viruses?

A

adeno-associated virus

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6
Q

Give examples of dsRNA viruses?

A

reovirus

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7
Q

Give examples of negative ssRNA viruses?

A

influenza

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8
Q

Give examples of positive ssRNA viruses?

A

poliovirus; hep A and C

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9
Q

Give exaample of reverse RNA virus?

A

HIV

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10
Q

Give an example of a reverse DNA virus?

A

hep b

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11
Q

Give an example of a cytopathic virus

A

hep B

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12
Q

Give an example of a non-cytopathic virus?

A

rhinovirus

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13
Q

What is involved in immmunity against chronic viruses?

A

T cells

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14
Q

what is involved in immunity against acute viruses?

A

neutralising antibodies

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15
Q

What aer the features of barrier protection against infection in the skin?

A

epithelial cells joined by tight junctions; longitudinal flow of air/fluid; fatty acids; antibacterial peptides; normal flora

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16
Q

What are the type III interferons?

A

IFN delta 1,2,3

17
Q

What are the functions of type I and type III IFNs?

A

induce antiviral repsonses and limit viral replication

18
Q

Which cells are IFN receptors found on?

A

all nucleated cells

19
Q

What do NK cells secrete to lyse cells?

A

perforin and granzyme B

20
Q

What activates invariant and unconventional T cells?

A

lipids; microbiota metabolites or cytokines

21
Q

What are the types of invariant and unconventional T cells?

A

NKT; MAIT and yd T cells

22
Q

How is infection related to viral load and T cell response?

A

infection occurs at the same time as T cell reponse not at the peak of the viral load

23
Q

How are antibodies invovled in the removal of viruses?

A

coat infected cell which leads to ADCC by NK cells; activate complement; opsonise for phagocytosis

24
Q

Which cells are specialised for production of type I IFns?

A

plasmacytoid DCs

25
Q

What is the function of Th1 cells in viral responses?

A

provide help for opsonising and complement fixing virus specific abs that block entry into uninfected cells and activate complemetn to destroy enveloped viruses

26
Q

Why do RNA viruses have a higher rate of replication than DNA viruses?

A

have to replicate their genoma using RNA polymerase which lacks the proofreading ability of DNA polymerase

27
Q

What is the benefit of RNA polymerase for RNA viruses?

A

high rate of mutations allows them to change the antigenic epitopes recognised by the adaptive immune system

28
Q

Aside from RNA polymerase, what other mutation mechanism do RNA viruses have?

A

segmented genomes which they can rearrange during viral replication

29
Q

What are the major viral surface glycoproteins?

A

haemagluttinin and neuramidase

30
Q

What is antigenic drift?

A

point mutations which change the epitopes on the viral surface glycoproteins recognised by adaptive immune system

31
Q

What is antigenic shift?

A

antigenic chanegs in virus that result from reassortment of hte segmented RNA genome between 2 different versions of a virus in a secondary host and result in major changes in the haemagglutinin ex[ressed

32
Q

Waht is the benefit for DNA viruses not having such a high rate of mutations?

A

can support a much larger genome that can subvert many aspects of antiviral defence

33
Q

What protein do many DNA viruses produce that prevents presentaiton of peptide:MHC I complexes?

A

immunoevasins

34
Q

Waht is dislocation?

A

viral proteins taht catalyse the degradation of newly made MHC-I complexes which activates the pathway normally used to degrade misfloded ER by directing them back into the cytosol (ERAD pathway)

35
Q

How does EBV cause immunosuppression of the host?

A

produces a homolog of IL10 which inhibits Th1 cells and IFNy production

36
Q

How can viruses evade NK cells?

A

producing a homolog of MHC-I which binds to KIRs and LIRs providing an inhibitory response

37
Q

What are cells with immune exhaustion characterised by?

A

expression of PD-1

38
Q

What receptor does EBV use to gain access to B cells?

A

CR2 (CD21)

39
Q

What is the function of EBNA1 in latent EBV infection?

A

interacts with the proteasome to prevents its viral genome from being degraded