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MIIM2002 > Influenza > Flashcards

Influenza Flashcards

1
Q

Symptoms of influenza

A

Cough, fever, chills, muscle aches, headache, normal chest X-ray

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2
Q

Duration of acute infection

A

Seven days or longer. Weakness and cough might persist for several weeks

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3
Q

Incubation period

A

1 - 5 days

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4
Q

Infectious period

A

5-6 days

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5
Q

At-risk groups

A

Young, elderly, people with underlying chronic heart, lung, renal, metabolic condition

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6
Q

Receptor bound by flu

A

Sialic acid-containing receptor on non-ciliated respiratory epithelium.

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7
Q

Configuration of sialic acid

A

Bound by alpha-2-6 linkage to galactose

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8
Q

Place in airways where flu particularly replicates

A

Large airways

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9
Q

Factor contributing to fever

A

IL1

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10
Q

Factor contributing to muscle aches

A

Interferon alpha

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11
Q

Where later infection can occur

A

Ciliated epithelium of trachea and bronchi

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12
Q

Bacterial pneumonia pathogenesis

A

1) Late-stage flu replicates in ciliated epithelium, deciliates it
2) Bacterial species colonise airways
- H. influenzae, staph. aureus, strep. pneumoniae

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13
Q

How closely related are influenza types A, B and C?

A

Not closely related.

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14
Q

Role of M1 protein

A

Capsid stability (matrix)

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15
Q

Role of M2 protein

A

Ion channel.

Allows H+ into virus, causing matrix conformation change, RNPs can exit capsid

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16
Q

Location of RNA-dependent RNA polymerase

A

Attached to ribonucleoprotein

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17
Q

Number of ribonucleoproteins

A

Eight

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18
Q

Genes encoded

A

Ten

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19
Q

Total number of HA and NA subtypes

A

17HA, 10NA

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20
Q

Type of genome

A

ssRNA, segmented into eight ribonucleoproteins

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21
Q

Number of RNA polymerase subunits

A

Three

22
Q

Number of silalic acid receptors on HA

A

Three

23
Q

Number of sialic acid receptors on NA

A

Four

24
Q

Area of influenza replication

A

Nucleus of host cell (despite being RNA virus)

25
Q

Reason for replication in the nucleus

A

Spliceosome needed to separate gene products of RNPs with two genes

26
Q

Tryptase Clara origin

A

Clara cells, limited to respiratory tract

27
Q

Tryptase Clara role

A

Removes lysine from HA cleavage site.

Allows HA to change conformation at pH 5 in endosome, escape endosome

28
Q

Mannose-binding lectin

A

Looks just like C1a.

Can take role of C1a in complement cascade

29
Q

Role of innate immune system in influenza infection

A

Slow virus until adaptive immune system is ready

30
Q

Role of CD8+ in influenza immunity
1)
2)

A

1) Not long-lived
2) Recognise peptides from internal antigens of virus. These peptides are broadly cross-reactive between type A subtypes
(NOT between A and B)

31
Q 
Role of antibodies in influenza immunity
1)
2)
3)
4)
A

1) LIfelong response
2) Bind HA, NA, prevent attachment/release
3) Ab+C’ lysis of infected cells
4) Preexisting antibodies neutralise input virus

32
Q

Antigenic drift

A

Formation of new strains within a subtype because of accumulated missense mutations

33
Q

Reason for greater number of mutations in RNA genomes

A

RNA genomes no more error-prone than others.

RNA-dependent RNA polymerase lacks proofreading system

34
Q

Effect of antigenic drift affecting HA/NA antibody-binding site

A

Antibodies can no longer bind/lower affinity binding. These mutations are selected FOR by natural selection

35
Q

Number of antibody-binding sites on HA

A

Five

36
Q

Duration of reverse-transcriptase PCR diagnosis

A

Hours - 1 day

37
Q

Duration of culture diagnosis (determine subtype)

A

Days

38
Q

Reverse-transcriptase PCR diagnosis:
1)
2)

A

1) RT-PCR sample

2) Antibody strip captures nucleoprotein in lysed virus sample

39
Q

Culture diagnosis:
1)
2)
3)

A

1) 10-days eggs with embryo infected with virus
2) Allantoic fluid is sampled
3) Allantoic fluid haemagglutination tested

40
Q

Definition of seroconversion

A

Four-fold titre increase in antibodies

41
Q

Haemagglutination test

A

1) Influenza virus can bind sialic acid on red blood cells, causing them to agglutinate
2) Chicken RBCs have sample added. If virus is not present, cells sink.

42
Q

Reason for use of chicken RBCs in haemagglutination tests

A

RBCs are nucleated, so sink if there is no agglutination (as they are heavy)

43
Q

Haemagglutination-inhibition test

A

1) Antibody added to haemagglutination test.
2) If antibody can bind to flu, no haemagglutionation.
Used to determine specific subtype of flu

44
Q

Influenza vaccine:
1)
2)
3)

A

1) Inactivated trivalent vaccine
2) H1N1, H3N2, influenza B strains
3) Intramuscular injection

45
Q

Influenza vaccine manufacture:
1)
2)
3)

A

1) Viruses grown in chicken eggs
2) Viruses purified from allantoic fluid
3) Virus chemically inactivated, detergent-disrupted

46
Q

Influenza vaccine effect on the immune system:
1)
2)
3)

A

1) Induces AB, not CD8+ response
2) 70% seroconversion in the healthy
3) After strains are selected, takes ~6 months to make vaccine

47
Q

Types of antiviral drugs for influenza:
1)
2)

A

1) Ion channel blockers

2) NA inhibitors

48
Q

Ion channel blocker action:
1)
2)

A

1) Inhibit M2 channel function in the endosome

2) H+ from pH drop cant enter virus, prevents endosomal escape

49
Q

Limitations of ion channel blockers

A

Only effective for type A influenza

50
Q

NA inhibitor action

A

1) Mimic sialic acid
Zanamivir - (+)’ve guanidine binds bottom of NA pocket.
Ostelamivir - Hydrophobic group fits into hydrophobic pocket in NA pocket.

51
Q

NA inhibitor limitations

A

Only effective if given within 2 days of symptoms

52
Q

NA inhibitor advantages

A

Effective for influenza types A and B

MIIM2002 (13 decks)

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