Multiple infections with seasonal influenza A virus induce cross-protective immunity against A(H1N1) pandemic influenza virus in a ferret model

Abstract

Background. An age bias toward children and young adults has been reported for infection and hospitalizations with pandemic H1N1 influenza (A[H1N1]pdm) in the 2009 and 2010 influenza seasons in the Southern and Northern Hemispheres. Serological analysis of prepandemic samples has shown a higher incidence of cross-reactive antibodies to A(H1N1)pdm virus in older populations; conserved T cell epitopes between viruses have been identified. The contribution of preexisting immunity to seasonal influenza to protection against A(H1N1)pdm infection was analyzed in a ferret model. Methods. Ferrets were pre-infected with influenza A viruses and/or vaccinated with inactivated influenza viruses with adj..