Development of a mucosal vaccine for pan-Sarbecoviruses: a papilloma pseudovirus expressing SARS-CoV-2 M and N proteins 2259718
Over the past two decades, three major coronavirus (CoV) outbreaks–SARS, MERS, and COVID-19–have occurred, all caused by Beta-coronaviruses. Future outbreaks of yet-undiscovered CoVs with pandemic potential are anticipated. This underscores the urgent need for a broadly protective CoV vaccine. We hypothesize that targeting conserved regions of the CoV genome, such as the membrane (M) and nucleocapsid (N) proteins shared across Sarbecoviruses, can provide cross-protective immunity. To induce mucosal immune responses at the site of CoV infection (upper respiratory tract), we used papillomavirus-like particles (VLPs) as a delivery vector. Vaccine constructs were designed using rearranged SARS-CoV-2 Omicron-XEC M and N sequences fused to ubiquitin to enhance antigen processing and T cell activation. These constructs were cloned into a pVax1 vector and expressed in HEK293T cells. Expression was confirmed by RT-PCR and Western blotting. The constructs were then packaged into pseudoviruses using bovine papillomavirus VLPs. Mice were immunized with these pseudoviruses. Intracellular cytokine staining revealed antigen-specific T cell responses in lymph nodes and spleens of immunized mice following peptide stimulation. These responses were absent in control animals. Furthermore, vaccinated transgenic K18-hACE2 mice showed protection against heterologous challenge with SARS-CoV-2 Omicron-KP.3, indicating cross-variant efficacy. Our findings demonstrate that mucosal delivery of conserved CoV antigens via papillomavirus VLPs induces strong, antigen-specific T cell responses and protects against heterologous SARS-CoV-2 challenge. This strategy shows promise for developing a pan-coronavirus vaccine. NIH Vaccines and Immunotherapy (VAC)