Presentation of hemagglutinin on adjuvant-bearing self-assembling peptide nanofibers increases heterologous responses against influenza

Influenza presents a global threat representing hundreds of thousands of deaths each year worldwide, yet influenza vaccines currently do not offer full protection against infection and must be updated each year to account for antigenic drift. Subunit vaccines using hemagglutinin (HA) are a promising approach to decrease reactogenicity while still providing protection, but these vaccines require large antigen doses or inclusion of reactogenic adjuvants. Here, we use multivalent presentation of HA on the self-assembling nanofiber platform Q11 coupled with a nanoscale adjuvant to augment responses to HA vaccines. We leverage polypeptides containing random combinations of lysine, glutamic acid, tyrosine, and alanine (KEYA) as a nanoscale, non-reactogenic adjuvant and demonstrate two methods of bioconjugation of HA to Q11 nanofibers, namely β-tail co-assembly and SortaseA (SrtA)-mediated ligation. Both conjugation methods demonstrated effective conjugation to Q11, with minimal perturbation of HA antigenicity with the inclusion of low concentrations of KEYA. β-tail co-assembly offered increased humoral responses, and the inclusion of KEYA-Q11 enabled modest increases in breadth of antibody binding and survival against influenza challenge. SrtA-mediated conjugation additionally augmented humoral immune responses and also elicited a significant increase in breadth of antibody binding, achieving significant binding to HA trimers with up to 30 years of antigenic drift from the immunized antigen, increased hemagglutinin inhibition to homologous and heterologous viruses, and survival in a lethal disease challenge. Together, these results demonstrate the utility of peptide nanofiber bioconjugation strategies to augment subunit vaccines, particularly in the context of influenza. STATEMENT OF SIGNIFICANCE: Influenza causes hundreds of thousands of deaths each year worldwide, yet current influenza vaccines do not offer full protection and must be updated each year. In this report, we describe self-assembled peptide nanofiber subunit vaccines comprised of the Q11 nanofiber platform, hemagglutinin antigens, and a nanoscale adjuvant consisting of randomized lysine, glutamic acid, tyrosine, and alanine (KEYA). Optimized formulations augmented humoral immune responses and elicited a significant increase in the breadth of antibody binding, achieving significant binding to HA trimers with up to 30 years of antigenic drift from the original antigen. These findings illustrate the utility of peptide nanofibers as platforms for subunit vaccines.