Virulence differences of closely related pandemic 2009 H1N1 isolates correlate with increased inflammatory responses in ferrets.

Several early pandemic H1N1 influenza isolates cause severe disease in different animals models, while most strains result in mild clinical signs similar to seasonal influenza. In this study, the pathogenesis of the virulent Mexican isolate A/Mexico/InDRE4487/2009 and a mild Canadian isolate A/Canada-AB/RV1532/2009 was compared in ferrets. These viruses differed at nine residues, none of which has been previously identified as virulence factor.

Assessment of the efficacy of commercially available and candidate vaccines against a pandemic H1N1 2009 virus.

Background: The emergence and global spread of the pandemic H1N1 2009 influenza virus have raised questions regarding the protective effect of available seasonal vaccines and the efficacy of a newly produced matched vaccine.

Methods: Ferrets were immunized with the 2008-2009 formulations of commercially available live attenuated (FluMist; MedImmune) or split-inactivated (Fluviral; GlaxoSmithKline) vaccines, a commercial swine vaccine (FluSure; Pfizer), or a laboratory-produced matched inactivated whole-virus vaccine (A/Mexico/InDRE4487/2009). Adaptive immune responses were monitored, and the animals were challenged with A/Mexico/InDRE4487/2009 after 5 weeks.