A new American study has found a weakness in H1N1's method for dodging detection by the immune system.
Jianpeng Ma, professor in bioengineering at Rice University and graduate student Jun Shen and Qinghua Wang, an assistant professor of biochemistry and molecular biology at Baylor College of Medicine, compared the sequences of over 300 strains of H1N1 to track its evolution.
The researchers were particularly examining hemagglutinin (HA), the protein "hook" that enables the virus to attach itself to and infect host cells.
Earlier research had found that five regions of H1N1's HA serve as antigenic sites, the protein fragments that activate the body's immune system. These antigenic sites constantly reorder their amino-acid sequences in the continuous cat-and-mouse game that viruses play to live on.
Researchers discovered several vital residues involved in both antigenic sites and the receptor-binding site, the part of the protein that affixes to a cell and allows the virus to attack.
Ma said: "The site is known, but no one thought it was involved in the immune system. In order to recognize the receptor, that particular region has to be robust.... But it turns out this region is not only variable, but also interacts with the immune system."
If a virus eludes antibodies, all five antigenic sites would have to mask themselves by mutating. The new discovery led the researchers to believe the receptor-binding residues would also have to mutate, but not so much that the binding no longer functions.
Ma explained: "If the binding is abolished, the virus dies."
He pointed out that such dual-function residues are a likely block for the virus.
He said: "It becomes a weak link and provides us with a window into the virus that we can monitor.... The virus's bottleneck is our opportunity."
Wang said: "An underlying implication is that this may not be restricted to H1N1...It may apply to other influenza viruses as well. If studying viral evolution can help predict what will cause a severe problem in humans, you can actually pre-stock vaccines, which will save time."