Key bird flu infection factor found

WASHINGTON, Jan. 9 (UPI) -- U.S. scientists have identified a key factor that determines the ability of influenza viruses to infect cells of the human upper respiratory tract.

The finding, published online in the journal Nature Biotechnology, explains how the H5N1 avian flu virus would have to change in order to spread through human populations, the National Institute of General Medical Sciences said in a release .

Although the H5N1 virus has infected several hundred people, person-to-person transmission has been limited. To trigger a widespread outbreak, the bird flu virus must infect the cells lining human noses and throats, the report said.

Ram Sasisekharan of the Massachusetts Institute of Technology said the virus can gain access only through a subset of the sugar molecules coating upper airway cells.

While the protein from human-adapted flu viruses favors the sugars dotting the cells of the nose and throat, the one from bird flu viruses opts for glycans on cells deeper in the respiratory tract. The findings suggest that for H5N1 bird flu virus to spread widely in humans, it must adapt so that it can latch onto the umbrella-shaped glycans of the upper respiratory tract, the report said.

http://www.upi.com/NewsTrack/Science/2008/01/09/key_bird_flu_infection_factor_found/9456/