Washington, Oct 16 : Researchers have revealed that determining the structure of a protein called hemagglutinin on the surface of influenza B may give clues as to what kinds of mutations could spark the next flu pandemic.

Dr. Qinghua Wang, assistant professor of biochemistry and molecular biology at Baylor College of Medicine, and Dr. Jianpeng Ma, associate professor, and their colleagues described the actual structure of influenza B virus hemagglutinin and compared it to a similar protein on influenza A virus.

Ma said that the comparison might be a key to understanding the changes that will have to occur before avian flu (which is a form of influenza A virus) mutates to a form that can easily infect humans.

The researchers have identified a particular residue or portion of the protein that might play a crucial role in how different types of hemagglutinin bind to human cells.

Hemagglutinin sits on the membrane or surface of the virus. When it finds a receptor in a cell, it clicks in and enters to infect the cell. The hemagglutinin on influenza B only fits into a receptor on human cells. However, influenza A virus hemagglutinin fits into receptors on human and bird cells.

Researchers say that understanding the differences in the two “keys” may provide a clue as to how the avian flu virus, which infects only bird cells easily now, must change to infect humans easily.

Ma said that understanding those changes could provide researchers with information about how likely a pandemic of bird flu might be.

“What would it take for the bird flu to mutate and start killing people? That’s the next part of our work,” Ma said.

There are two main forms of influenza virus – A and B. Influenza B virus infects only people while influenza A infects people and birds.

In the past, influenza A has been the source of major worldwide epidemics (called pandemics) of flu that have swept the globe, killing millions of people. The most famous of these was the Pandemic of 1918-1919, which is believed to have killed between 20 and 40 million people worldwide. It killed more people than World War I, which directly preceded it. 
The new study is published online in the Proceedings of the National Academy of Sciences. (ANI)