In article <4i5im9$m79 at otis.netspace.net.au>, ruth at netspace.net.au (Ruth
> I have heard that Haemagglutinin receptors of Influenza viruses may
> initiate clumping of erythrocytes.Is this true? If so, what is the
> purpose of this effect? Does it actually benefit the virus in any way?
Dead right, hence the name haem (blood) agglutinin (sticking... well
roughly translated anyway). The HA (there are lots of HA molecules on the
surface of the virus) binds to a receptor (sialic acid residues on
glycoproteins) on the cell surface, and can clump cells by effectively
forming a bridge between two (or more) cells.
The virus doesn't necessarily "intend" to bind erythrocytes (and probably
doesn't get the chance to in natural infections of man, as the virus does
not enter the bloodstream) but it must bind sialic acid residues on its
target cells to initiate an infection (the virus is taken into the cells
by endocytosis following this binding).
In any case, the virus doesn't actually come to any harm by binding
erythrocytes (although it cannot infect them) as there is a second protein
on the virus surface called neuraminidase. Neuraminidase is an enzyme
which cleaves sialic acid residues and so can free the virus from cell
Hope this helps
Microbial Molecular Genetics and Cell Biology Group,
School of Biological Sciences, Biology West Building,
University of Birmingham,
West Midlands, B15 2TT.
Tel. (+44) (0)121 414 6555
Fax. (+44) (0)121 414 6557
E-mail g.e.price at bham.ac.uk