Pre-exposing Canada Geese (Branta canadensis) to a low-pathogenic H1N1 avian influenza virus protects them against H5N1 HPAI virus challenge.

In previous studies we examined the role of Canada Geese (Branta canadensis) in the epidemiology of Eurasian highly pathogenic avian influenza (HPAI) H5N1. To expand on this and better understand how pre-exposure to heterosubtypic low-pathogenic avian influenza (LPAI) viruses might influence the outcome of H5N1 HPAI infection, we pre-exposed naïve juvenile Canada Geese to different North American wild-bird-origin LPAI viruses. We selected H1, H2, and H6 hemagglutinin subtype viruses based on their higher-order evolutionary relatedness to the H5 hemagglutinin. Pre-exposing Canada Geese to either H2N3 or H6N5 viruses did not protect them against a lethal H5N1 HPAI virus challenge. In addition, H5N1 was transmitted to naïve control birds that were placed among both groups resulting in death by 5 days postcontact. In contrast, Canada Geese that were pre-exposed to H1N1 were protected against a lethal H5N1 challenge, shed minimal amounts of the virus into the environment, and did not transmit the infection to naïve contact birds. None of the H1N1, H2N3, or H6N5 pre-exposure sera neutralized H5N1 in vitro; however, sera from H1N1-infected birds reduced virus plaque size but not number when compared with H2N3, H6N5, or negative sera, suggesting that antibodies directed against the neuraminidase may have had a role in the protective effects observed.