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Preexisting #immunity to the 2009 pandemic #H1N1 virus reduces susceptibility to #H5N1 #infection and disease in #ferrets

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By G.M.

Editor’s summary

The vast majority of the human population has immunity to influenza A virus (IAV) by prior infection, vaccination, or both. However, protection is generally subtype-specific, and it is not clear whether prior infection against one subtype could confer protection against clade 2.3.4.4b H5N1 IAVs, which are currently circulating in birds and dairy cows. Here, Restori et al. demonstrated that prior infection with the 2009 pandemic H1N1 IAV was protective against subsequent direct infection with H5N1 IAV in ferrets. Moreover, prior immunity reduced susceptibility to infection by transmission from an infected donor ferret. These data suggest that prior immunity to IAV, especially to the 2009 pandemic H1N1 virus, may offer a degree of protection against H5N1 infection. —Courtney Malo


Abstract

Zoonotic infections with emerging influenza viruses occur in the context of population-wide immunity to seasonal strains. Because of the worldwide spread of highly pathogenic clade 2.3.4.4b H5N1 influenza viruses in wild birds, there have been numerous spillover events into mammals. This includes a recent spillover into dairy cows that started an ongoing outbreak across the United States. Human infections with avian and bovine origin H5N1 influenza viruses have been documented, raising concern that these viruses may cause a pandemic. Therefore, using a ferret model, we evaluated the impact of preexisting, infection-elicited immunity on susceptibility to H5N1 infection and on severity of disease. Preexisting immunity to the 2009 pandemic H1N1 influenza virus prevented severe H5N1 disease and reduced susceptibility to infection through direct contact with an infected donor ferret. These studies demonstrate that preexisting immunity to influenza viruses, especially the 2009 pandemic H1N1 virus, is a barrier to infection and disease caused by clade 2.3.4.4b H5N1 viruses.

Source: Science Translational Medicine, https://www.science.org/doi/10.1126/scitranslmed.adw4856

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