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Virology > Lecture 23 - Influenza > Flashcards

Lecture 23 - Influenza Flashcards

1
Q

What type of genome does influenza virus have?

A

8 segments of (-)ssRNA

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2
Q

What viral family does influenza virus belong to?

A

Orthymyxoviridae

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3
Q

What can change your immunity to a type of influenza?

A

when it mutates

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4
Q

What are the 2 types of mutations?

A

antigenic shift and antigenic drift

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5
Q

What are the characteristics of the influenza viral capsid?

A

enveloped containing hemagglutinin (HA) and neraminidase (NA) antigenic glycoprotein spikes on the surface

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6
Q

What helps us name the influenza viruses? What is it based on?

A

HA and NA proteins

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7
Q

What are the 4 influenza viral capsid proteins?

A

HA, NA, M1 and M2

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8
Q

What are M2 influenza viral proteins?

A

ion channel proteins

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9
Q

What species is influenza A H1 found in?

A

human, swine, bird

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10
Q

What species is influenza A N1 found in?

A

human, swine, bird

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11
Q

What species are most of the H and N subtypes of influenza A are found in?

A

birds

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12
Q

What is the issue with the influenza A H1N1?

A

it is in 3 different species including humans

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13
Q

What does HA protein bind to?

A

sialic acid

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14
Q

Where is sialic acid found?

A

present on glycoproteins of ciliated cells lining the sinuses and airways

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15
Q

How does the influenza virus enter the cell?

A

receptor-mediated endocytosis

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16
Q

In order for the influenza viral genome to exit the endosome, what must happen?

A

drop the pH from 7 to 5 to expose fusion peptide proteins = triggers fusion with endosomal membrane and viral membrane to deliver the viral RNPs (ribonucleoproteins)

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17
Q

What is the function of M2 proteins?

A

the ion channels allow hydrogen ions to penetrate virion

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18
Q

Where does the influenza virus replicate its genome?

A

cytoplasm

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19
Q

What is the function of the M1 protein?

A

matrix proteins that holds the vRNPs together

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20
Q

How are the M1 proteins dissociated from the vRNPs?

A

increase in hydrogen ions weakens the matrix proteins association from the vRNPs

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21
Q

What happens to the vRNPs once released into cytoplasm?

A

is directed towards the nucleus and enters it

22
Q

What helps initiate genome replication?

A

the proteins on the end of the genome

23
Q

What are 2 things that will be synthesized from copying the (-)ssRNA genome?

A

the viral mRNA and the (+)ssRNA template (antigenome)

24
Q

In order for the viral mRNA to be translated by the host cell ribosomes, what modification must the virus do its viral mRNA?

A

snatch a 5’ cap to put on it

25
Q

What is the function of the influenza viral protein NS1?

A

prevents nuclear export of cellular pre-mRNAs by trapping them in the nucleus

26
Q

What is the 5’ cap used/beneficial for the influenza virus?

A

as a primer to initiate transcription of viral RNA

27
Q

What intermediate is formed during influenza viral replication?

A

double-stranded RNA (dsRNA)

28
Q

Which influenza viral protein binds and sequesters the dsRNA intermediate?

A

NS1

29
Q

Where does assembly of the progeny influenza virion occur in the cell?

A

cell membrane

30
Q

How are new influenza virions released?

A

budding off

31
Q

Which organ does influenza virus initially enter the body through?

A

respiratory tract

32
Q

In the lungs, what does influenza virus infect?

A

pneumocytes lining alveoli of the lungs

33
Q

What do the pneumocytes release as the influenza virus replicates?

A

cytokines and chemokines

34
Q

What mediates genetic variation that causes new strains of influenza to appear more often than yearly?

A

antigenic shift and antigenic drift

35
Q

What is antigenic drift responsible for?

A

localized/seasonal influenza epidemics caused by types A or B

36
Q

Where do the mutations in the influenza virus occur in the antigenic drift process?

A

in the HA and/or NA genes

37
Q

What is antigenic shift responsible for?

A

pandemic strains

38
Q

In which genetic variation process are new influenza virions produced?

A

antigenic shift

39
Q

Which genetic variation process allows for influenza viruses to move from animals to birds in order to infect humans?

A

antigenic shift

40
Q

Why was the H1N1 Swine flu pandemic alarming?

A

traced to an antigenic shift resulting in triple reassortment of bird, human, and pig viruses

41
Q

What is a consequence of a single mutation within the H5N1 strain?

A

allow the influenza virus spread more efficiently

42
Q

What was significant of the H5N1 influenza virus strain?

A

jumped directly to infecting humans which never observed before; same strain was killing chickens

43
Q

What animal reservoir does the H5N1 infleunza virus strain infect?

A

birds

44
Q

What type of genetic variation process did the H5N1 strain undergo?

A

antigenic drift – did not combine with human strain

45
Q

What happens when the M2 ion channels are inhibited?

A

prevents uncoating step

46
Q

What is the issue with using antivirals that inhibit the M2 ion channels?

A

the virus develops drug resistance

47
Q

What happens with the NA capsid protein is inhibited?

A

prevents NA from cleaving sialic acid during budding

48
Q

What is the most effective way to prevent influenza?

A

vaccines

49
Q

Why does recombination occur within influenza?

A

due to segmented genome

50
Q

What are 3 distinguishing characteristics about the H7N9 strain?

A

in birds and humans | combo of 3 viruses fromwild birds and domesticated ducks and chickens | short lived

Virology (23 decks)

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