Clade 2.3.4.4b non-replicating-protein based interventions against H5 highly pathogenic avian influenza virus in turkeys

Authors: LEE, JIHO - Orise Fellow; Lee, Chang; Lee, Scott; IBRAHIM, SHERIF - Orise Fellow; Suarez, David; Spackman, Erica

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2025
Publication Date: 9/2/2025
Citation: Lee, J., Lee, C.W., Lee, S.A., Ibrahim, S., Suarez, D.L., Spackman, E. 2025. Clade 2.3.4.4b non-replicating-protein based interventions against H5 highly pathogenic avian influenza virus in turkeys. Avian Diseases. Volume 69, Issue 3, 288–294. https://doi.org/10.1637/aviandiseases-D-25-00055.
DOI: https://doi.org/10.1637/aviandiseases-D-25-00055

Interpretive Summary: In the U.S. the most poultry flocks affected by bird flu have been turkeys. New interventions have been shown to mitigate disease and mortality, and can slow transmission in chickens, but data for turkeys are lacking. Here we evaluated an inert protein to mitigate infection in commercial turkeys. The protein was made from a recent U.S. virus and was tested for it's ability to prevent disease and mortality in 10 week old commercial turkeys after a single exposure The turkeys were divided into groups that were exposed at different ages in order to characterize the immune response over time. There was 100% protection against death for all the turkeys and only 2 of 10 turkeys in the group with the least time to build immunity had mild clinical signs for 2 days before recovering. Importantly, the turkeys also excreted much less virus, which is known to help limit virus spread. Lastly, the surveillance program for bird flu in the U.S. would have to be modified for bird-flu interventions in US poultry. Therefore, we also evaluated a new test that could be used with exposed turkeys. The new test was successful at detecting antibodies to the bird flu virus in serum from the turkeys after exposure.

Technical Abstract: The global outbreak of clade 2.3.4.4b H5N1 highly pathogenic avian influenza (HPAI) virus has caused tremendous losses in poultry. Although turkeys are a smaller sector in poultry production compared to chickens, they tend to be affected more severely by HPAI virus because they can usually be infected with a lower dose of influenza A virus than chickens (i.e., they are more susceptible). Exposure to non-replicating proteins may help control HPAI, however data with turkeys are somewhat limited regarding how well they work and approaches to modifying surveillance have not been developed. Here, an H5N9 non-replicating protein comprised of a clade 2.3.4.4b H5 hemagglutinin from A/turkey/Indiana/22-003707-003/2022 (TK/IN/22) and a North American wild bird lineage N9 was evaluated in commercial broad breasted white turkeys by challenge to live virus. Turkeys were divided into three groups, where each group was exposed to the non-replicating protein once at 3 (3wk), 7 (7wk), or 9 (9wk) weeks of age. All birds were challenged at 10 weeks of age with TK/IN/22 HPAIV. There was 100% survival in all groups except the sham exposure group which had 100% mortality. A significant decrease in viral shedding was observed in all exposed groups compared to the shams, although the 9wk group shed significantly higher quantities by the cloacal route at seven days post challenge (DPC) compared to the 3wk group. The neuraminidase inhibition-enzyme linked lectin assay (NI-ELLA) was used as a serological test that was able to detect antibody in birds that had been infected after exposure and challenge based on antibodies to the NA protein of the challenge virus (N1 NA) in serum collected 7, 10 and 14DPC. Between 50 and 90% of turkeys, depending on age at exposure, were positive by NI-ELLA at 7DPC and 100% were positive at 14DPC regardless of age at exposure.