January 8, 2008

Massachusetts scientists discover bird flu transmission to humans

A big factor affecting the transmission of bird flu to humans is the shape of the sugar receptors in human lung cells, professor Ram Sasisekharan of Massachusetts Institute of Technology (MIT) said.

Previous researchers indicate that an influenza strain infects humans depending on the ability of a protein on the surface of the virus, called hemagglutinin, to bind to a sugar receptor in the respiratory tract.

In humans, these receptors are called as alpha 2-6, while in birds, these are known as alpha 2-3.

Until recently, scientists believed it was a genetic switch in the virus that allowed it to bind to human rather than bird receptors, allowing the much-feared "species jump."

The MIT study, however, found that it actually depends on the shape of the sugar receptors in human lung cells.

The human alpha 2-6 receptors have two shapes, one resembling an umbrella, the other a cone.

Researchers discovered that to infect humans, flu viruses must bind to the umbrella-shaped receptors.

Sasisekharan said that this discovery would not only aid in monitoring of the bird flu virus, but also in the development of potentially improved therapeutic interventions for both avian and seasonal flu.