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Immunity, Infection and Haematology > Viral block > Flashcards

Viral block Flashcards

1
Q

What are viruses?

A

Obligate intracellular parasites

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2
Q

What does a virus particle consist of?

A

a nucleic acid genome protected by a protein shell (capsid), which may be surrounded by a membranous envelope

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3
Q

What are the members of the virus group I? Examples?

A

dsDNA viruses - HSV, adenovirus

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4
Q

Group II, examples

A

ssDNA viruses - parvovirus

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5
Q

Group III, examples

A

dsRNA - Reoviruses, bluetongue

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6
Q

Group IV, examples

A

sense RNA viruses - HCV, polio, Yellow fever

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7
Q

Group V, examples

A

Antisense RNA - Influenza, Ebola, Measles

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8
Q

Group VI, examples

A

RNA reverse transcriptase virus - HIV

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9
Q

Group VII, examples

A

DNA reverse transcriptase virus - HBV

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10
Q

What is an example of an icosahedral virus?

A

Adenovirus

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11
Q

What are the 4 steps of the virus lifecycle?

A

Enter, Replicate, Assemble, Release

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12
Q

What are the 3 types of viral components synthesised in the infected cell?

A
  1. the essential replication factors - non-structural proteins
  2. subunits that are assembled to form new capsids & virions - structural proteins
  3. copies of the viral genome
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13
Q

What examples of cytopathic viruses that destroy target cell by cell lysis?

A

Almost all non-enveloped viruses (adenovirus, polio virus etc)

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14
Q

How were viruses identified before the introduction of ELISA?

A
  1. suspected virus-containing cultures grown in widely permissive cells (Vero, Hela, A549)
  2. many viruses showdistinct patholgies in culture (e.g. polio in Hep-B cells) - e.g. distinctive plaque formation
  3. imaging of infected cells on electron micrographs
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15
Q

What are the ELISA based methods?

A

Identification directly on basis of their antigens or by detecting antibodies to the virus

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16
Q

What are the 4 common types of viral disease?

A
  1. Acute Infection e.g. rhinovirus, rotavirus, influenza virus
  2. Persistent infection, smouldering e.g. lymphocytic choriomeningitis virus
  3. Persistent infection, latent e.g. Herpes simplex virus
  4. Persistent infection, slow e.g. Measles virus SSPE, HIV, Human T-lymphotropic virus
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17
Q

What are some examples of the cytosolic PAMP sensors?

A

cGAS, NOD2, MD5, RIG-I

18
Q

What do the cytosolic PAMP sensors do?

A

trigger expression of inflammatory cytokines (TNFa, IL-1B, IL-12) and 2 classes of interferons - type I (IFN-a, IFN-b) and type III (IFN-L)

19
Q

How do the interferons work against viruses?

A

they trigger a cascade of Interferon Stimulated Genes (ISGs) which encode over 300 antiviral proteins

20
Q

What do type II interferons (IFNg) do?

A

they are a key activator of macophages and induces MHC II expression
In innate response: produced by NK cells
In adaptive response: produced by T & B cells

21
Q

What is ELISPOT?

A

Process of staining antigen stimulated cells for the presence of IFNg

22
Q

How does the adaptive immune system recognise viruses?

A

Viruses initially present antigens as endogenous protein (MHC I) –> induction of cytotoxic T cells
Once released from the infected cel, virions can present as exogenous antigens via MHC Class II –> CD4 T helper cells

23
Q

What is meant by ‘prodromal’?

A

Most common symptoms of viral infection. Du to the general effects of innate immune responses (due to interferons)

24
Q

What are the intracellular molecules used for signalling by PRRs?

A

MyD88, TRAM, TIRAP, TRIF

25
Q

How are NK cells activated in a viral infection? (general)

A

MHC I act as inhibitory signals to inactivate NK cells. Reduced levels of MHC I caused by viruses would therefore lead to a ‘missing self’ phenotype which activates NK cells

26
Q

What are the 3 ways in which NK cells are activated?

A
  1. By releasing IFNg - potent inducer of ISGs
  2. By releasing cytolytic granules –> directly target the MHC I null cell for destruction
  3. By death-receptor mediated cytolysis of target cell
27
Q

What causes NK cells to move towards infected cells?

A

IL-12 gradients

28
Q

What are the cytotoxins contained within a CD8 T cell?

A

perforin, granzyme, granulysin

29
Q

How does FAS ligand help in the cytotoxic response?

A

MHC class I recognition induces CD8 cell proliferation and expression of FAS ligand (FASL). Binding of FASL to FAS on target cell induces a cascade of pro-apoptatic signals leading to target cell destruction

30
Q

What is Antibody-Directed Cell Cytotoxicity (ADCC)?

A

NK cells have Fc receptor (FcgRIII - CD16) which binds to Fc portion of IgG bound to surface of infected cells. This triggers killing of virus response

31
Q

What type of virus is the influenza virus?

A

segmented RNA virus. member of orthomyxoviruses

32
Q

Infection in which area of the respiratory tract is associated with a high mortality?

A

Lower respiratory tract

33
Q

What is antigenic drift?

A

Gradual accumulation of mutations with changes in the dominant membrane antigens Haemagglutinin (H) & Neuraminidase (N)

34
Q

What is antigenic shift?

A

A sudden change in the antigenic type, caused by reassortment of the individual segments of genome

35
Q

What group of virus is the HIV?

A

Class VI

36
Q

What is the family and the genus for HIV?

A

Retroviridae family, Lentivirus genus

37
Q

What type of virus is the HIV?

A

Enveloped, single-stranded, positive sense RNA virus

38
Q

What 3 major genes does HIV encode?

A
  1. gag (capsid or core protein)
  2. pol (polymerase, integrase, protease)
  3. env (envelope)
39
Q

What 6 accessory genes does HIV-1 encode?

A

tat, rev, nef, vif, vpu, vpr

40
Q

Which cell does HIV infect?

A

CD4+ T cells

41
Q

How does HIV bind to the host cell?

A

Binding via the gp120 envelope protein and 2 co-receptors (CCR5, CSCR4) which subsequently bind to gp120 and cause structural changes to allow virla membrane to fuse with CD4+ T cell plasma membrane

42
Q

What changes occur during translocation to the nucleus?

A

Reverse transcriptase converts the viral ssRNA into a dsDNA copy, the viral integrase enzyme then cuts the host DNA & ligates in the viral dsDNA genome (provirus)

Immunity, Infection and Haematology (6 decks)

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