[Seminar] Epitope focusing of humoral immune responses in highly antigen-experienced vaccine recipients

Join us on Thursday, 8 October, for a lecture by Dr Anne Hahn, Peter Doherty Institute for Infection and Immunity, University of Melbourne.

• Dr Anne M Hahn Research Officer, Valkenburg Laboratory, Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne

Date: Thursday, 8 October

Time: 12:00-13:30

Location: SR1A G/F Jockey Club Building for IR, 5 Sassoon Road

Registration: https://hkuems1.hku.hk/hkuems/ec_hdetail.aspx?ueid=109345

• Epitope focusing of humoral immune responses in highly antigen-experienced vaccine recipients

Influenza viruses pose significant risks to global health due to their evolution and spread in animal reservoirs. Seasonal vaccination with yearly updated strains mitigates severe disease outcomes particularly for at risk populations. Vaccine effectiveness varies with antigenic similarity of vaccine strains and circulating viruses as well as individual exposure histories. Immunity from previous vaccinations and infections influences both, the immune response to novel antigen encounters as well as the antigenic diversity of viral populations. To further improve vaccine strategies, a better understanding of the intersection of host immune responses mounted through cumulative antigen exposures and antigenic drift of influenza viruses is needed.

The primary objective of this study is to determine the extent of epitope focussing of the antigenic footprint of humoral immune responses after repeated vaccination and its selective implications for viral evolution. For this, we use serum samples collected from a cohort of elderly individuals from a five-year randomised control trial that received twice-annual standard inactivated influenza vaccinations. We combine sub-neutralising longitudinal immune serum with matching vaccine representative virus strains of influenza A (H1N1 & H3N2 subtypes) for in vitro passaging. We assess the antigenic footprints of polyclonal vaccine sera and the mutational capacity of the viruses by measuring viral diversity and the emergence of variants at the sub-consensus level using deep whole-genome sequencing. These results will be further integrated with additional data for each study participant including longitudinal immunological characterisation of cellular and humoral immune responses.

Taken together, this study improves the understanding of how host immune responses may impact influenza virus evolution and antigenic changes to inform future vaccine design and control strategies.

About Dr Anne Hahn:

Dr Anne Hahn completed her PhD at the University Erlangen-Nuremberg, Germany, on unconventional T cell development and anti-viral immune responses. She then pursued an M.Sc. at the London School of Hygiene and Tropical Medicine, UK, before working at the Yale School of Public Health, US. As a postdoctoral research associate, she led a SARS-CoV-2 genomic surveillance initiative and investigated viral evolution and variant emergence. Since 2024, she is a Research Officer at the University of Melbourne in the group of A/Prof Sophie Valkenburg, where her research focuses on emerging and re-emerging RNA viruses, mostly influenza virus, at the interface of viral evolution and human immune responses and its implication for vaccinology. She has authored >30 peer-reviewed publications and received several competitive fellowships in Germany, the US and Australia. She is further active in science outreach and advocates for early- and mid-career researchers.