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1Principles of Biomedicine - MD1 > 82 - Influenza > Flashcards

82 - Influenza Flashcards

1
Q

Seasonal flu symptoms

A

Ranges from subclinical to severe Typical influenza involves fever/chills, cough, headache, muscle aches, fatigue, loss of appetite Chest X-ray normal Acute infection lasting about 7 days or longer; no persistence of virus; weakness and cough may last for several weeks

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2
Q

Percentage of population infected annually

A

10-20% of Australian population

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3
Q

Annual consultations due to flu in Australia

A

~1 million

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4
Q

Annual flu deaths in Australia

A

1,500

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5
Q

Annual global deaths due to flu

A

250,000 - 500,000

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6
Q

Influenza incubation period and infectious period

A

Incubation period 1 - 5 days; Infectious for 5 - 6 days

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7
Q

Flu receptor

A

Sialic acid-containing receptors in ciliated resp epithelium (AS alpha2-6 linkage to galactose in humans)

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8
Q

Where in the airways does flu particularly replicate?

A

Large airways (in epithelial cells of URT and LRT)

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9
Q

Cytokine leading to fever in flu

A

IL-1

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10
Q

Cytokine leading to malaise, headaches, muscle aches in flu

A

IFN

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11
Q

When does bacterial secondary infection become a danger with flu?

A

Late-stage infection can have replication in ciliated epithelium of trachea and bronchi gives bacteria a good place to replicate (H. influenzae, S aureus, S pneumoniae)

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12
Q

Can influenza cause pneumonia?

A

Can cause viral pneumonia only rarely. Mostly secondary bacterial pneumonia

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13
Q

Cause of flu death in elderly

A

From secondary bacterial infection

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14
Q

Family of influenza

A

Orthomyxoviridae

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15
Q

Flu virion structure

A

Enveloped, ssRNA (-)-sense, segmented genome,.

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16
Q

Types of influenza

A

A, B and C. No immunological cross-reactivity.

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17
Q

Influenza types that are major human pathogens

A

Type A and B. C is a minor human pathogen

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18
Q

*Influenza genome segment structure

A
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19
Q

Type of flu viruses that infect non-human species

A

Type A

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20
Q

Number of genome segments in flu

A

8

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21
Q

*Influenza virion structure

A
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22
Q

Anti-IFN flu protein

A

NS1

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23
Q

Number of RDRP subunits in flu

A

3

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24
Q

HA structure

A

Trimeric, elongated

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25
Q

NA structure

A

Tetrameric

26
Q

Influenza type that is distinguished based on HA and NA types

A

Type A

27
Q

Number of HA in type A

A

16

28
Q

Number of NA in type A

A

9

29
Q

Ancestral host of flu type A

A

Aquatic birds

30
Q

At what pH does influenza escape endosome?

A

~pH=5

31
Q

Current;y-circulating type A flu strains

A

H1N1 and H3N2

32
Q

How does flu enter target cell?

A

RME

33
Q

Tryptase Clara role

A

Cleaves HA in newly-budded virions to make them infectious. Reveals hydrophobic fusion protein.

34
Q

Important cell in recovering from flu

A

CD8+ T cell

35
Q

Types of flu antigens recognised by CTL

A

Internal antigens (which are conserved between type A subtypes, not between A and B).

36
Q

How long-lived is CTL immunity against flu?

A

Not long-lived

37
Q

Process responsible for ineffective anti-flu antibody response

A

Antigenic drift

38
Q

Where do neutralising Ig against HA bind?

A

Overlapping epitopes in 5 sites around receptor-binding pocket

39
Q

Where do mutations accumulate in flu HA?

A

5 sites around receptor-binging pocket

40
Q

When does a flu strain arise against which there is no immunity?

A

When all five epitopes around binding pocket have mutated

41
Q

Flu vaccine

A

Inactivated trivalent vaccine. Most recent strains of flu A H1N1, H3N2, and flu B (newer vaccines have 2 flu B strains)

42
Q

People for whom a flu vaccine is recommended

A

People over 65 People with chronic lung, heart, kidney diseases With diabetes Immunosuppressed Health workers (might transmit to at-risk patients)

43
Q

Where are flu vaccines grown?

A

In 10-day embryonated egg, in allantoic fluid.

44
Q

Do flu vaccines induce CTL immunity?

A

No. Is an inactivated vaccine

45
Q

Average flu vaccine efficacy

A

~70%

46
Q

How long does it take to produce vaccine after strains have been predicted?

A

~6 months

47
Q

Targets for flu antivirals

A

Ion channel blockers (M2) NA inhibitors

48
Q

What does endosome acidification do to flu virion?

A

Reveals HA hydrophobic fusion protein. Allows endosome escape. M2 ion channel allows acidification of interior of virion, unlocks genome segments from capsid, allowing release of genome segments into cytoplasm.

49
Q

Effect of amantadine, rimantadine

A

Block M2 ion channel. Inhibit uncoating of flu A virus in the endosome.

50
Q

How are amantadine, rimantadine administered?

A

Orally, daily

51
Q

How soon must zanamivir, ostelamivir be given?

A

Within two days of infection

52
Q

Strains of flu showing resistance to zanamivir and ostelamivir

A

H1N1

53
Q

How is Relenza administered?

A

Inhaled

54
Q

How is Tamiflu administered?

A

Orally-administered prodrug

55
Q

Human flu virus receptor

A

SA alpha2-6 linkage to galactose

56
Q

Avian flu virus receptor

A

SA alpha2-3 linkage to galactose

57
Q

Change required for HA specificity to either alpha2-6 or alpha2-3

A

Single amino acid change

58
Q

Type of evolution of flu

A

Linear. Most-recent strain replaces previous strain

59
Q

Possible pandemic flu configuration from antigenic shift

A

Human-adapted internal proteins, avian HA and NA (that aren’t recognised by human immune systems)

60
Q

People particularly susceptible to swine flu

A

Pregnant women, obese people, indigenous populations

1Principles of Biomedicine - MD1 (157 decks)

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