Expert: Florence M Rollwagen - 4/28/2009

Question
Can you explain how Hemagglutinin and Neuraminidase are used by the flu virus? I understand that the H gets it in your cells and the N lets it reproduce. But exactly how does that operate on a cellular level? I've had one year college Bio so far, so you don't have to go too soft with the answer.

Also, what is the significance of the combination, H5N1, H1N1, ect?

Answer
Hi Andrew:  What a timely question!

You are correct, the H allows the virus to bind to the cell.  Then the cell takes up the virus and incorporates it into the cytoplasm.
http://en.wikipedia.org/wiki/Influenza_hemagglutinin

The N is an enzyme that digests sialic acid.  This allows the virus to move around in the mucus of the respiratory tract and to exit from the infected cell.
http://en.wikipedia.org/wiki/Viral_neuraminidase

The numbers refer to the antigenic determinant.  They represent a change in protein structure.  The easiest way to picture this is by analogy to blood groups.  Let's say instead of blood groups A, B and O, we called them 1, 2 and 3.  So a person could be blood group 1,3 (if AO), or 1,2 (if AB).  

There are at least 16 H numbers and 9 N numbers.  They refer to the host origin of the flu.  Flu viruses can come in any combination, such as H1N1, H1N2, H1N3, etc.  

For more information (maybe more than you wanted!) look here:http://en.wikipedia.org/wiki/Influenza

Hope this helps.  Write back if you have more questions.

FM Rollwagen, PhD