Rice, BCM team finds weakness in H1N1's method for evading detection by the immune system
The H1N1 influenza virus has been keeping a secret that may be the key to defeating it and other flu viruses as well.
Researchers at Rice University and Baylor College of Medicine (BCM) have found what they believe is a weakness in H1N1's method for evading detection by the immune system.
Comparing its genetic sequences going all the way back to the virus's first known appearance in the deadly "Spanish flu" outbreak of 1918, they discovered a previously unrealized role of receptor-binding residues in host evasion, which effectively becomes a bottleneck that keeps the virus in check.
Rice's Jianpeng Ma and graduate student Jun Shen and BCM's Qinghua Wang compared the sequences of more than 300 strains of H1N1 to track its evolution; they reported their results in a recent online edition of the scientific journal PLoS ONE.
The researchers were looking in particular at hemagglutinin (HA), the protein "hook" that allows the virus to attach itself to and infect host cells. It's long been known that five regions of H1N1's HA serve as antigenic sites, the protein fragments that trigger the body's immune system. These antigenic sites, first mapped in 1981, shuffle their amino-acid sequences in the endless cat-and-mouse game that viruses play to survive.
The researchers discovered several key residues involved in both antigenic sites and the receptor-binding site, the part of the protein that attaches to a cell and allows the virus to invade.
The common belief has been that the receptor binding could not change. "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," Ma said. "But it turns out this region is not only variable, but also interacts with the immune system."