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cellular basis of immunity > 8 - viral infection > Flashcards

8 - viral infection Flashcards

1
Q

most common recurrent infection in humans

A

viral

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2
Q

transient

A

feature of viral infections

last only for a short time

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3
Q

zoonotic

A

jumped species barrier

viral infection caused in humans, originally from another animal

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4
Q

why do zoonotic infections have high mortality rates in humans

A

new to humans so have not co-evolved

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5
Q

examples of zoonotic infection s

A

HIV –> originally from chimpanzees in africa
hantavirus –> originally from rodents in N/S america
severe acute respiratory sydrome (SARS) –> coronavirus from bats in china

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6
Q

viral replication

A

depend on host proteins and machinery

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7
Q

features of viral genomes

A

3 –> 300 genes
single or souble stranded RNA/DNA
enclosed within capsid

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8
Q

capsid

A

coat protein

recognised by immune cells

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9
Q

cytopathic effect

A

virus infects cell and causes lysis

induces autophagy or apoptosis on exit of cell

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10
Q

example of cytopathic virus

A

polio virus

influenza

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11
Q

latent virus

A

infect cells but only activated when immunity wanes

activation prodces infectious virions

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12
Q

example of latent virus

A

herpes

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13
Q

non-cytopathic virus

A

replicate without destruction of cells

e.g. Hep B

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14
Q

how do viruses cross epithelial barriers in intestinal infections
example

A

using antigen-sampling M cells

HIV
poliovirus

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15
Q

how do viruses cross epithelial barriers in respiratory viruses
example

A

establish infection in airway lining

INfluenza
rhinovirus

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16
Q

other methods to cross epithelial barriers

A 
insect vectors
physical trauma (causes bloodborne viruses)
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17
Q

what mediates viral innate immunity

A

type 1 interferons
complement
NK cells

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18
Q

type 1 interferons

A

host proteins that interfere with viral gene transcription

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19
Q

viral invasion

A

viruses exploit specific molecules on cells as receptors for invasion
(tissue tropsim)

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20
Q

HIV tropism

A

tissues support growth of virus
CD4 important
chemokine receptor CXCR4 and CCR5

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21
Q

indirect antibody binding

A

couples antibody binding to classical pathway of complement

C1 q/r/s complex

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22
Q

direct antibody binding

A

Fc receptors bind directly to neutralising antibody which is an opsonising virus particle

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23
Q

role of NK cells on antibody binding

A

Fc receptors on surface of NK cell bind to antibody as virus leaves infected cell
stimulated to kill infected cell using using perforins and granzymes

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24
Q

epidemic

A

new case of disease in a population at a higher rate than expected

25
Q

outbreak

A

disease in one location

can be contained

26
Q

global epidemic

A

pandemic

27
Q

main mech of AIDS

A

infects and destroys CD4+ T cells

28
Q

Gay-Related ImmunoDeficiency (GRID)

A

1980s

original name for HIV

29
Q

prevalence of AIDS

A

39+ million deaths globally since 1st clinically recognised

30
Q

AIDS patients show symptoms of …

A

PCP pneumonia

31
Q

PCP pneumonia

A

pneumocystic pneumonia
common lung infection
bad in immunocompromised patients
trreatable if found early

32
Q

HIV-1 retrovirus spread

A

zoontoic
requires high risk transmission for human to human spread
spread due to prostitution in african colonies

33
Q

when was HIV-1 first seen in humans

A

congo 1959

34
Q

HIV protein structures

A

GP 120 - Docking glycoprotein

GP 41 - transmembrane glycoprotein

35
Q

HLA-DR

A

human leukocyte antigen - antigen D related
MHC class II receptor
ligand for the T cell receptor

36
Q

HIV epithelial entry mechanisms

A

M cells
epithelial damage
langerhan cells
chemokine receptor CCR5

37
Q

M cells used by HIV for epithelial entry

A

transfer through and present to dendritic cells

38
Q

importance of langerhan cells

A

projections stick out to sample antigens

39
Q

where is the chemokine receptor CCR5 found

A

small intestine

40
Q

HIV-1 binds to chemokine receptor CCR5

mechanism

A

HIV-1 binds via gp120

virus is transcytosed across membrane and exposed to dendritic cells

41
Q

consequences of HIV infection

A

dendritic cells translocate HIV from mucosa i
viral proliferation and viremia
loss of helper T activities
therefore no maintenance of CD8 cels and no antibody response of `b cells

42
Q

timescale of HIV infection

A

dendritic cells translocate HIV from mucosa in 30 mins - quick
by 3 weeks all lymphoid tissues are infected

43
Q

why flu symptoms shown in HIV

A

loss of CD4 T cells in the blood

opportunistic infection when CD4 T cells <200ul

44
Q

3 classes of influenxa

A

A
B
C

45
Q

influenza A

A

most common

responsible for pancdemic outbreaks

46
Q

flu is zoonotic

A

bird (avian) virus that adapts to humans

spread via aerosol droplets

47
Q

influenza cytolytic effects

A

infections created in respiratory tract epithelium

48
Q

structure of influenza virus

A

spherical or rod
enveloped
2 x spike glycoproteins on surface (HA and NA)

49
Q

HA

A

trimeric haemaglutinin

mediates binding to cell surface (sialic acid)
mediates internalisation of viral particles (endocytosis)

50
Q

NA

A

tetrameric haemaglutinin

cleaves sialic and promotes viral release from cells using ennzymes

51
Q

bird genotypes

A

diverse

52
Q

HA subtypes

A

H1 to H5

53
Q

NA subtypes

A

N1 to N9

54
Q

importance of pigs in influenza virus transfer to humans

A

pigs carry both types of linkage (e.g. alpha-2,6)
pigs infected by both linkages and exhange viral genomes
crucial for transfer

55
Q

antigenic drift in influenza virus

A

point mutations in HA and NA
means virus is no longer recognised by neutralising antibodies
common cause of antibiotic

56
Q

antigenic shift in influenza virus

A

reassortment of human/bird genomes inside pig
whole cell change
therefore highly transmissable
pandemic caused

57
Q

3 major pandemics

A

1918 - spanish flu
1957 - asian flu
1968 - hong kong flu

58
Q

spanish flu

A

1918-1920
H1N1 subtypes
brought over by US after WWI
targets active immune systems (20-40 yr olds)
high infection rates - 5% population died

59
Q

hypercytokinemia

A

response of immune system to spanish flu
cytokine storm
release of over 150 inflammatory mediators

cellular basis of immunity (21 decks)

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