Even as UN health experts are still looking for places to bury their faces in as the swine flu pandemic scare turned out to be a dud, here is some help at hand - Hong Kong researchers hypothesize perhaps prior exposure to seasonal influenza could have blunted the edge of the pandemic.
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.