Question

2. Explain how and why this form of genetic change occurs to influenza within a host. (Hint: is it due to reassortment between two Influenza viruses OR mutations?). Please be thorough in your response. You may draw it out if it helps. (2pts) 3. Recently, flu vaccines for 2017-2018 included protection against H3N2. What does H3 and N2 represent? Please spell them out for full credit AND explain why 3 and 2 stands for. You may need to refer back to unit 1. (2pts).

Answer 1

Answer:

2) Antigenic drift is the mechanism happening in influenza virus. This is a genetic variation in viruses by accumulation of mutations.

These mutations result in change of their surface proteins. In a host these proteins act as antigens.

The prior antibodies formed cannot recognize this changed antigens. That is aquired immunity by prior infection cant resist new infection after genetic drift.

So many mutations in short time for influenza virus because there is no proof reading mechanism for RNA polymerase of the virus. That is no error correction when new RNA is formed.

3) H and N in influenza virus stands for HEMAGGLUTININ and NEURAMINIDASE respectively. They are surface proteins of influenza virus.

Influenza viruses are of 4 types in general A B C and D

Of this A is the one considered here.

There are 18 different hemagglutinin subtypes numbered from 1 to 18.

There are 11 different neuraminidase subtypes, numbered from 1 to 11.

This can occur in different permutation and combination. Say 198. Only 131 combinations are detected in nature.

So H3N2 means.

Hemagglutinin subtype 3 and Neuraminidase subtype 2.