Why Pandemic Alert Turned Out To Be A Dud?

They think such exposure to seasonal influenza A, either infection or vaccination, may induce a cross-reactive immune response against the pandemic virus. Their logic is indeed interesting - currently available seasonal flu vaccines do not offer cross-reactivity to pandemic H1N1 in any age group. So then individuals previously infected or exposed to seasonal influenza A viruses may have memory cell-induced cross-protection to pandemic H1N1.

Prior research showed humans having cross-reactive memory cells to a wide range of H5N1 peptides despite any previous exposure to avian influenza A (H5N1). In this study researchers determined that memory cells established by seasonal influenza viruses can break down pandemic H1N1-infected target cells and ultimately induce cross-protective antibodies.

“Our data suggest that individuals who were infected with seasonal human influenza A viruses previously or who received seasonal human influenza vaccines may derive benefit, at least in part, from the preexisting cross-reactive memory cytotoxic T lymphocytes to reduce the severity of pdmH1N1 infection even without protective antibodies,” say the researchers.

Their article, Cytotoxic T lymphocytes established by seasonal human influenza cross-react against 2009 pandemic H1N1 influenza virus, appears in the July 2010 issue of the Journal of Virology.