Impacts of universal influenza mRNA vaccine on enhancing the efficacy of seasonal vaccination

SUMMARY Current influenza (flu) vaccines based on immunity to variable hemagglutinin (HA) provide low efficacy because of continuing HA antigenic changes and poor cross-protection. The flu ion channel M2 protein ectodomain (M2e) represents highly conserved epitopes and the HA-stem (HA2-fusion) is also an immune target for conferring protection against different viruses. My mentor's lab reported that heterologous (human, swine, avian) tandem repeat M2e protein (5xM2e) could be a cross-protective immunogen and chimeric M2e-stem protein vaccine conferred broad cross-group protection. Nonetheless, the prior 5xM2e and M2e- stem protein vaccines require high doses and need to add neutralizing immunity. COVID-19 mRNA vaccines have been approved to widely immunize six-month-old children to the elderly, validating mRNA vaccine modality. My preliminary mouse study demonstrated that 5xM2e mRNA and M2e-stem mRNA vaccines (encapsulated into lipid nanoparticles, LNP) effectively induced M2e and stem IgG antibody responses at a low dose. Most innovatively, I found that 5xM2e mRNA-LNP supplemented conventional inactivated split flu vaccination significantly enhanced the immunogenicity and efficacy with a single dose, probably via transient induction of innate cytokine and chemokines. These preliminary data warrant further investigation of this novel vaccination strategy of combining cross-protective flu mRNA and conventional flu vaccines, overcoming a weakness of each vaccine platform. As supported by my preliminary data, I hypothesize that neutralizing HA immunity (HA mRNA or split) plus universal target immunity (M2e-Stem mRNA or protein) will offer increased immunogenicity leading to enhanced protection against homologous and heterologous viruses. In aim 1, I will determine the immunogenicity and efficacy of protection against homologous and antigenically different flu viruses after HA-based (HA mRNA or split) plus cross-protective antigen (M2e-stem mRNA or protein) vaccination. For aim 2 approaches, I will investigate the immune mechanisms of mRNA-LNP supplemented split- and protein-based vaccines inducing enhanced protection. The potential mechanisms to study will determine the contribution of antigen-specific humoral and cellular immunity to cross-protection, and the innate immune responses (innate cell phenotypes, cytokines, chemokines), likely leading to enhanced adaptive immunogenicity of vaccines. The roles of Fc receptor (FcR), natural killer (NK) cells, and ADCC (antibody-dependent cell-mediated cytotoxicity) in conferring cross-protection will be determined by using mutant mice and in vitro assays. The expected outcome of this project will advance our knowledge of how mRNA-LNP supplemented conventional vaccine elicits enhanced efficacy. If successful, this project could open a new avenue for research in enhancing vaccine efficacy for other pathogens.