Stalk-specific pH1N1 antibodies may have snuffed out seasonal H1N1 flu

CIDRAP:

Jan 31, 2012

Stalk-specific pH1N1 antibodies may have snuffed out seasonal H1N1 flu
Infection with 2009 H1N1 pandemic influenza (pH1N1) boosted antibodies specific to the hemagglutinin (HA) stalk rather than its head, a phenomenon that may have contributed to the disappearance of seasonal H1N1 influenza strains circulating at the time, US researchers reported in a study in Proceedings of the National Academy of Sciences. The team created chimeric hemagglutinin (cHA) proteins and viruses expressing those chimeric proteins that allowed them to detect stalk-specific antibodies in preparations that also included head-specific antibodies. (The HA of flu viruses is shaped like a mushroom, with a head and a stalk.) They found relatively high titers of stalk-specific immunoglobulin G antibodies in the blood of pH1N1-infected patients compared with those who weren't infected. By using cHA engineered with heads of viruses not seen in humans, the researchers showed the antibodies were reacting with the stalk and not the head. They also showed that the antibodies reduced virus replication. They write, "We believe that the sudden boost in antistalk titer that occurred with pH1N1 virus infection may have generated herd immunity against the seasonal virus, ultimately resulting in its disappearance."
Jan 30 Proc Natl Acad Sci abstract