Abstract
Highly pathogenic H5N1 avian influenza viruses of clade 2.3.4.4b cause sporadic human infections and currently raise concerns about a new influenza pandemic. Heterogeneities in disease severity have been observed in the past and are reported among infected farm workers in the United States. These may be attributed to differences in pre-existing H5N1 cross-reactive antibodies. In this study, we characterize H5N1 cross-reactive antibody landscapes in the current population (#NCT05794412 and #NCT01022905) and assess the effect of AS03-adjuvanted pandemic H1N1 and non-adjuvanted seasonal influenza vaccination on H5N1 cross-neutralizing and IgG antibody titers targeting a range of influenza virus-derived antigens. We detect H5N1 cross-neutralizing antibodies using a vesicular stomatitis virus-based pseudovirus system that correlate well with antibodies inhibiting the spread of authentic H5N1 viruses, anti-group 1 hemagglutinin stalk and anti-trimeric hemagglutinin antibodies. Additionally, we find that AS03-adjuvanted pandemic H1N1 vaccination increases H5N1 cross-reactive antibodies significantly in a pandemic H1N1 immunologically partially naïve population. Furthermore, we show that immune imprinting causes distinct H5N1 cross-reactive antibody patterns pre-vaccination.
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Acknowledgements
We sincerely thank Prof. Florian Krammer for providing stalk HA antigens and Prof. Gert Zimmer for sharing VSV-H5N1 and protocols for the pseudoneutralization assay. We also thank Lisa Butticaz and Thomas Vivet for their excellent technical help. We thank Florence Pojer and Kelvin Lau from the EPFL Protein Production Facility for helping with trimerized HA antigen expression. We thank Yves Alexandre Cambet, Vincent Jaquet and Adriana Renzoni for help with the fluorescent microscope and the Luminex reader. We also thank Olha Puhach and the study teams for sample collection. Last, we thank Kenz Le Gouge for help with data analysis. This project was supported by the Swiss National Science Foundation Ambizione program (grant number: 193475) and a research grant from Moderna Inc. We are grateful for the participants who were willing to donate their samples and agree to participate in our research. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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M.A.B. and B.M. conceptualized the study, M.A.B. performed the experiments and analyzed the data. D.B. produced the stalk HA antigens, C.A.S. collected the clinical samples, M.A.B. and B.M. analyzed and interpreted the data, A.D. and B.M. supervised the work, All authors read and approved the final version of the manuscript. M.A.B. and B.M. verified the underlying data.
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B.M. has received research support from Moderna and consulting fees from Rocketvax AG. A.D. is a member of scientific advisory boards for Bioaster and Sanofi, is a consultant for Boost Biopharma, Botanical solutions and Vaccine Formulation Institute, and has research collaborations with Moderna, GSK and Sanofi. The remaining authors declare that they have no competing interests.
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Alcocer Bonifaz, M., Bhavsar, D., Siegrist, CA. et al. Adjuvanted influenza vaccination increases pre-existing H5N1 cross-reactive antibodies. Nat Commun (2026). https://doi.org/10.1038/s41467-025-68137-x
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DOI: https://doi.org/10.1038/s41467-025-68137-x
