Influenza

Question 1

what was influenza predicted to be

Answer 1

a cause of major pandemic for humans

Question 2

what is one of the advantages of influenza viruses

Answer 2

ahead of the curve of vaccination against the virus

Question 3

what type of virus is influenza

Answer 3

RNA

Question 4

what are the types of influenza

Answer 4

A, B and C

Question 5

where is RNA found in viruses

Answer 5

within the nucleic acid

Question 6

what are the key stages of viral replication for influenza virus

Answer 6

attachment
penetration
uncoating
synthesis of viral components
assembly
release

Question 7

how can influenza be transmitted

Answer 7

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

Question 8

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

Answer 8

respiratory tract

Question 9

what does the initial stage of influenza infection look like

Answer 9

• 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

Question 10

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

Answer 10

• travels along the microtubules with the help of kinesins

Question 11

how does the capsid of the virus become decoded

Answer 11

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.

Question 12

how do the viral core proteins and RNA enter the nucleus

Answer 12

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

Question 13

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

Answer 13

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

Question 14

what happens once the viral surface proteins are made

Answer 14

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

Question 15

how do the progeny viruses exit the cell

Answer 15

budding

Question 16

how do vaccines work to prevent influenza

Answer 16

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

Question 17

what is hemagglutinin

Answer 17

one of the proteins on the influenza virus envelope

Question 18

how does the virus attach to the host cell

Answer 18

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

Question 19

how does the cell take up the virus

Answer 19

endocytosis

Question 20

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

Answer 20

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

Question 21

how many RNA segments are within the influenza virus

Answer 21

8

Question 22

how does the viral genome enter the host nucleus

Answer 22

nuclear pores

Question 23

what is haemagglutinin

Answer 23

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

Question 24

how many types of haemagglutinin are there

Answer 24

14

Question 25

what are the two key surface proteins on the influenza virus

Answer 25

haemagglutinin and neuroaminidase

Question 26

what is neuroaminidase

Answer 26

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

Question 27

how many types of neuroaminidase

Answer 27

nine

Question 28

what are glycoproteins

Answer 28

protein molecules with sugar sidechains

Question 29

what is antigenic drift

Answer 29

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

Question 30

what does genetic drift lead to

Answer 30

new viruses

Question 31

what are the proteins involved in antigenic drift

Answer 31

neuroaminidase and haemagglutinin

Question 32

why do some vaccines only protect us for one season

Answer 32

antigenetic drift

Question 33

how is influenza named

Answer 33

from the protein combination of the surface proteins HA and NA

Question 34

what do HA proteins usually interact with on the host cell

Answer 34

sugars to create a bond and allow entry

Question 35

what can happen to viruses when they replicate

Answer 35

they can mutate slightly

Question 36

what can accumution of the virus mutations lead to

Answer 36

antigenic drift - new strains of the virus

Question 37

which change is more severe - antigenic shift or antigenic drift

Answer 37

shift

Question 38

what is antigenic shift

Answer 38

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

Question 39

which form of influenza is affected by antigenic shift

Answer 39

A

Question 40

do most viruses change

Answer 40

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

Question 41

how can viruses that grow in birds grow in humans

Answer 41

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

Question 42

can bird flu affect humans

Answer 42

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