Influenza Flashcards

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1
Q

what was influenza predicted to be

A

a cause of major pandemic for humans

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2
Q

what is one of the advantages of influenza viruses

A

ahead of the curve of vaccination against the virus

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3
Q

what type of virus is influenza

A

RNA

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4
Q

what are the types of influenza

A

A, B and C

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5
Q

where is RNA found in viruses

A

within the nucleic acid

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6
Q

what are the key stages of viral replication for influenza virus

A

attachment
penetration
uncoating
synthesis of viral components
assembly
release

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7
Q

how can influenza be transmitted

A

from person to person through large respiratory droplets, direct contact or airborne dispersal

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8
Q

where does infection from influenza mainly take place in the human body

A

respiratory tract

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9
Q

what does the initial stage of influenza infection look like

A
  • attachment of virus proteins to a receptor on the surface of the host cell
  • virus is then taken into the cell by receptor mediated endocytosis
  • internalised in a membrane bound capture vesicle that carries the viral core
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10
Q

how does the virus get to the nucleus of the cell once it has been internalised

A
  • travels along the microtubules with the help of kinesins
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11
Q

how does the capsid of the virus become decoded

A

the membrane of the vesicles fuses with the membrane of the virus to decode the capsid. the viral core RNA and proteins are then released into the cytoplasm and are guided by host proteins to the nucleus of the host cell.

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12
Q

how do the viral core proteins and RNA enter the nucleus

A

guided to the nucleus by host proteins and enter via host protein channels

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13
Q

what happens once the RNA and proteins of the virus have entered the host cell nucleus

A

cell machinery is used to replicate the viral genome to make mRNA. some will exit the cell to exploit cellular ribosomes to direct synthesis of viral proteins which go back to the nucleus to associate with viral RNA

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14
Q

what happens once the viral surface proteins are made

A

they are processed in the cytoplasm and travel to the cell surface where they combine with encapsulated nuclear proteins to form progeny viruses which depart from the cell by budding

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15
Q

how do the progeny viruses exit the cell

A

budding

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16
Q

how do vaccines work to prevent influenza

A

they stimulate host cellular responses to ingest the virus but are ineffective against viruses that cause the common cold and AIDS

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17
Q

what is hemagglutinin

A

one of the proteins on the influenza virus envelope

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18
Q

how does the virus attach to the host cell

A

haemagglutinin binds to the host receptor with sialic acid because it recognises the receptor polysaccharides that terminate with the sialic acid

19
Q

how does the cell take up the virus

A

endocytosis

20
Q

what does the endocytic vesicle of the virus fuse with and what are the events following this

A

lysosome, and the acidity within the lysosome allows protons to travel across ion channels into the viral core and cause matrix proteins to detach the proteins covering the RNA genome. haemogglutinin undergoes conformational change and inserts into the vesicle membrane to stimulate the membrane fusion between the virus and lysosome. the genome and proteins then flow freely away into the cytoplasm

21
Q

how many RNA segments are within the influenza virus

A

8

22
Q

how does the viral genome enter the host nucleus

A

nuclear pores

23
Q

what is haemagglutinin

A

a glycoprotein composed of sugars and proteins which binds to sialic acid on the surface of cells.

24
Q

how many types of haemagglutinin are there

A

14

25
Q

what are the two key surface proteins on the influenza virus

A

haemagglutinin and neuroaminidase

26
Q

what is neuroaminidase

A

a glycoprotein that is important for the release of the virus from inside the infected cells

27
Q

how many types of neuroaminidase

A

nine

28
Q

what are glycoproteins

A

protein molecules with sugar sidechains

29
Q

what is antigenic drift

A

change in the surface structure due to point mutations in the genomes

30
Q

what does genetic drift lead to

A

new viruses

31
Q

what are the proteins involved in antigenic drift

A

neuroaminidase and haemagglutinin

32
Q

why do some vaccines only protect us for one season

A

antigenetic drift

33
Q

how is influenza named

A

from the protein combination of the surface proteins HA and NA

34
Q

what do HA proteins usually interact with on the host cell

A

sugars to create a bond and allow entry

35
Q

what can happen to viruses when they replicate

A

they can mutate slightly

36
Q

what can accumution of the virus mutations lead to

A

antigenic drift - new strains of the virus

37
Q

which change is more severe - antigenic shift or antigenic drift

A

shift

38
Q

what is antigenic shift

A

a major change in the antigenic structure due to recombination which can result in a pandemic

39
Q

which form of influenza is affected by antigenic shift

A

A

40
Q

do most viruses change

A

no, for many our immune systems are able to recognise them from one year to the next

41
Q

how can viruses that grow in birds grow in humans

A

pig cells have locks that can be opened by human and bird flu. this leads to the genes combining at random and result in a new flu virus that no human immune system has seen before

42
Q

can bird flu affect humans

A

no they have different surface keys that do not match the human cell receptor keys

43
Q
A