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Virology > 10 Orthomyxoviridae > Flashcards

10 Orthomyxoviridae Flashcards

1
Q

what is M2

A

core protein, has a channel through it

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2
Q

what are the single-stranded negative strand RNA viruses like

A

analysis RNA-dependent
RNA- polymerases
Many branches harbour human pathogens

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3
Q

what is the order of Orthomyxoviridae Family

A

unassigned

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4
Q

what is the family of orthomyxoviridae like

A

Straight, mucus, RNA Viruses

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5
Q

how many genera are there

A

7 genera of Orthomyxoviridae

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6
Q

what are the genera of orthomyxoviridae

A 
›	Influenza virus A
›	Influenza virus B
›	Influenza virus C
›	Influenza virus D
›	Thogotovirus 
›	QuaranJAvirus
›	Isavirus (ISA: infectious salmon anaemia)
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7
Q

what can influenza type A viruses infect

A

man, horses, pigs, bats and birds

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8
Q

what can influenza type A cause

A

pandemics

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9
Q

what can influenza type B viruses infect

A

man and seals

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10
Q

what can influenza type B cause

A

human disease but generally not a severe as A types

Re-assortment with type A can lead to pandemics

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11
Q

how are influenza A and B differentiated

A

they are not able to be distinguished by electron microscope

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12
Q

what does influenza C infect

A

man
pig
dog

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13
Q

what does influenza C cause

A

doesn’t cause infection

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14
Q

how is influenza C distinguished

A

EM - distinguishable structures

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15
Q

what does influenza D infect

A

pigs

cattle

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16
Q

what is the orthomyxoviridae genome like

A

Segmented single stranded (-) sense RNA (8 A, B:7 C,D) (-ve sense = opposite to mRNA, cant translate directly – has to make an mRNA to translate)

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17
Q

what is the orthomyxoviridae lipid envelope like

A
  • spherical sometimes filamentous (pleomorphic, change shape)
  • glycoproteins + major antigenic determinants
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18
Q

what is the M1 protein in orthomyxoviridae like

A 
Matrix Protein (M1)
- between envelope and core
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19
Q

what is the core in orthomyxoviridae like

A
  • RNP (ribonucleoprotein) complex
  • ve sense RNA has various proteins that surround it: polymerase basic protein (PB1, PB2) polymerase acid protein (PA) nucleoprotein (NP)
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20
Q

what do viral glycoproteins bind with

A

Glycoproteins + major antigenic determinants haemagglutinin, trimer (Ha or H)
Binds sialic acid

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21
Q

what are viral glycoproteins involved in

A

in attachment, entry and fusion

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22
Q

what must happen to viral glycoproteins on exit

A

must be cleaved – done by neuraminidase, tetramer (NA or N)

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23
Q

how if flu infection caused

A
  • virus droplets circulate in air following a sneeze
  • FLU circulating in air for over an hour
  • aerosol directly contact with nose/mouth
    Or
  • aerosol directly contact fomite e.g. mobile phone and then you touch phone and then your face
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24
Q

what are flu symptoms

A

fever, headache, extreme muscular tiredness, vomiting

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25
Q

difference between flu and cold

A
  • flu = fever characteristic high temperature for few days (host cell response)
  • flu = severe aches
  • cold = usually more stuffy nose
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26
Q

where does flu droplets attach

A

Aerosol transmission to respiratory tract via droplets attached to Sialic Acid receptors on epithelial cells

27
Q

what does influenza virus cause after 1-3 days of infection

A
  • damaged cells release cytokines (storm) causing chills, malaise, fever and muscular ache
  • additional respiratory symptoms: runny nose and cough
28
Q

what does influenza virus restricted to respiratory tract cause

A
  • no viremia or spread to other tissues
  • Direct viral damage
  • Indirect through inflammatory
    = possible bronchitis and interstitial pneumonia
29
Q

what are the virus life cycle stages

A
  1. attachment
  2. endocytosed
  3. fusion and uncoating
  4. viral -ve sense RNA released – goes into nucleus
  5. post-translational processing and packaging
  6. budding
30
Q

what happens at attachment stage

A
  • HA binds to sialic acid (neuraminic acid) on host cell

- adapted to host sialic acid host /cell specificity

31
Q

what happens at endocytosed stage

A

Endocytosis engulfs virion = endocytotic vesicles

32
Q

what happens at fusion and uncoating stage

A
  1. Cleavage of haemagglutinin 2. Under low pH induces fusion of the 2 membranes (assisted by M2 protein)
33
Q

effect of fusion of the 2 membranes in virus life cycle

A

Opens a pore = release virion content into cytoplasm

- RNA travel to and into the nucleus (function of the NP protein)

34
Q

what is the effect of M2

A

affects pH (uncoating) as allows H ions through

35
Q

what is the effect of antiviral amantadine

A

blocks this release of the vRNA by acidification

36
Q

what is viral RNA

A

-ve sense strand

37
Q

what happens when -ve viral RNA released

A 
must make (+) sense mRNA (protein production)
PB1, PB2 and PA (polymerase) - in nucleus needs to make mRNA and cRNA 
- RNAs helped out of nucleus into cytoplasm by NEP and M1
38
Q

what is RNA always in association with

A

viral proteins (vRNP)

39
Q

what is mRNA made for

A

translation

40
Q

what is cRNA

A

copy RNA

41
Q

what is cRNA made for

A

serves as a template for replication

42
Q

what happens to mRNA segments in post-translational processing and packaging

A

translated

43
Q

what happens to cRNA segments in post-translational processing and packaging

A

replicated/packaged

44
Q

what happens in post-translational processing and packaging

A

Exit nucleus => reach assembly site => package segments (NEP-Nuclear Exit Protein)
unknown if packaging is a random or selective

45
Q

what happens if packaging is random in post-translational processing and packaging

A

If random: (expect to get >8) 12 segments in a single flu as suggested by some scientists would suggest that any 12 go in an then 10% of the viruses would be viable

46
Q

what happens if packaging is selective post-translational processing and packaging

A

If selective: 8 different segments would need to be packaged by a specific mechanism

47
Q

what happens in budding stage

A

Assemble and Bud out from the apical cell membrane
reverse of entry sequence
= Cell membrane Provides envelope

48
Q

what happens in budding stage when released

A

Need releasing as HA anchors to sialic acid receptors
NA activity for removal of sialic acid
= hence NA inhibitor as anti-virals (Oseltamir, Zanamir)

49
Q

what are PB2, PB1, PA

A

RNA-dependent RNA polymerase complex

50
Q

what do PB2, PB1, PA require

A

ve sense RNA to make more +ve sense RNA from the -ve sense

51
Q

what is HA

A

receptor-binding protein haemagglutinin

52
Q

what is NP

A

nucleoprotein

53
Q

what is NA

A

sialic acid-destroying enzyme neuraminidase

54
Q

what is M

A

matrix protein M1 and ion channel M2

55
Q

what is NS

A

nuclear export protein (NEP/NS2)

host antiviral response antagonist non-structural protein 1 (NS1)

56
Q

mRNA synthesis

A

starts 3’ end to 5’ end
+ve sense being made by -ve sense
Has a cap

57
Q

what is an epidemic

A

localised cluster of cases

58
Q

what is a pandemic

A

worlswide epidemic

59
Q

what is antigenic drift

A

changes in protein by genetic point mutation and selection

60
Q

what happens to virus in antigenic drift

A

changes shape

61
Q

what is antigenic shift

A

changes in proteins through genetic-reassortment (nucleic acids)

62
Q

what causes antigenic shift

A

Due to segmented genome (influenza has 8 segments)

= allows rapid and constant re-assortment between genes of different influenza viruses (“mixed/co-infections”)

63
Q

what does the segmented genome of influenza mean

A

sudden acquisition of a gene for a completely new HA or NA
= novel subtype that spreads rapidly around the world as most or all humans have no immunity to it
= BIG CHANGE (pandemic?)

64
Q

how can influenza be prevented

A

Vaccines
- Epidemics can be controlled by vaccines based on HA
polyvalent vaccine of several strains circulating based on surveillance data

Virology (15 decks)

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