Mixed lipopeptide-based mucosal vaccine elicits a long-term bone marrow memory response that is potentially cross-reactive against a broad-spectrum of coronaviruses in mice

Raj Samir PatelBabita Agrawal^*

• University of Alberta, Edmonton, Canada

SARS-CoV-2 is continuing to prevail as an endemic virus, and therefore, we need a next-generation vaccine that prevents SARS-CoV-2 infections, broadly protects against multiple CoVs, and induces long-term local and systemic immunity. To address that need, we have designed a mixed lipopeptide-based pan-coronavirus (LPMix) vaccine based on T and B cell epitopes derived from highly conserved and functional regions of the SARS-CoV-2 S, N, and M proteins. Here, we demonstrate that intranasal immunizations of mice with LPMix induced a long-lasting systemic IgM/IgG, and mucosal IgA response against a broad-spectrum of CoVs, showing clinically significant levels of neutralizing antibody titers. Splenocytes and bone marrow cells, derived from LPMix immunized mice, demonstrated a robust proliferation response against vaccine antigens (P1-7), which were maintained up to 2 months and 7 months, after LPMix immunizations, respectively. Moreover, antigen-specific B cells and memory CD4 + /CD8 + T cells were long-lived and maintained up to 7 months after LPMix immunizations, in the lungs, spleen and bone marrow. The addition of HKCC (heat-killed Caulobacter crescentus), a novel mucosal adjuvant, promoted the longevity of memory CD4 + /CD8 + T cell and B cell responses. Overall, our studies demonstrate that a mucosal lipopeptide based vaccine, targeting conserved epitopes of SARS-CoV-2, elicits a durable, long-lasting immune responses against a broad range of CoVs.