Influenza- Drift and Shift

Question 1

Antigenic drift

Answer 1

occurs due to point mutations

- where the altered shape of the receptor prevents neutralising antibodies from recognising the viral receptor

Question 2

antigenic drift is the reason

Answer 2

different vaccines are being constantly developed

Question 3

Influenza and antigenic dfit

Answer 3

1) Pathogens, like the influenza virus, have receptors which enable them to bind to host cell surfaces
2) Antibodies to these viral receptors, bind and prevent them from binding to the host cell, preventing infection.
o These antibodies are known as neutralising, as they neutralise the virus’ ability to infect the host cell
3) However, some viruses, have point mutations, which alter the shape of their receptor, preventing antibodies from recognising the viral receptor.
4) Now the virus is able to bind to and infect host cells
5) In this way, the pattern of antigens expressed by a virus can change over time- this process of developing small changes to receptors over time is called antigenic drift
6) Caused by point mutations
7) Causes our susceptibility to influenza infections, even if prior infection has already taken place
8) Why different vaccines are being constantly developed

Question 4

antigenic shift is associated with

Answer 4

large scale viral epidemics

Question 5

influenza and antigenic shift

Answer 5

1) Pathogens such as the influenza virus, have receptors which enable them to bind to the host cell surfaces
2) Antibodies recognise and prevent these receptors from binding to and infecting host cells- neutralising
3) Sometimes viruses arrive which can escape the effect of these neutralising antibodies
4) This can occur when two different strain of influenza virus are able to infect a host cell
5) The progeny virus’ produced from such doubly infected cells can contain segments of genome from both strains
6) Some viruses will gain parts of the genome encoding receptors for host cell surfaces
7) Neutralising antibodies will be unable to recognise these receptors from the second strain and unable to prevent the virus from binding to the cell surface of the host cell and causing infection
8) This process in which large changes in the antigenicity of viruses occur is known as Antigenic shift- these large changes can mean that much of the immunity against the original influenza virus’ are lost
9) Such antigenic shift is often associated with large scale viral epidemics

Question 6

antigenic shift

Answer 6

the process in which large changes in the antigenicity of viruses occur- large changes can mean that much of the immunity against the original influenza virus’ are lost