On Sept. 8, 2020, Vaxart announced pre-publication of a manuscript titled “Preclinical studies of a recombinant adenoviral mucosal vaccine to prevent SARS-CoV-2 infection.”

Key Findings:

• Immunization with the vaccine candidate induced IgA response in the lungs of animals, which is indicative of a mucosal immune response.  Of particular note, neutralizing antibodies in the lungs were observed at a very high percentage of the total antibody response. 
• Immunization with our vaccine candidate expressing full length S and N proteins induced IgG responses in a dose-dependent manner.
• Antigen-specific CD4+ and CD8+ T cells were induced at both low and high doses.
• Vaccine administration induced only low levels of IL-4 production, suggesting little risk of vaccine- dependent disease enhancement.

The study was designed to assess the relative immunogenicity of four candidate vaccines expressing multiple combinations of the spike (S) and nucleocapsid (N) proteins of the SARS-CoV-2 virus in a standard mouse model. While all candidates demonstrated the ability to elicit a strong immune response, the most successful candidate contained the full length S and N proteins. While the S protein is responsible for receptor binding, membrane fusion, and tissue tropism and a major target for neutralizing antibodies, targeting full length S protein in combination with N protein may prevent future vaccine-driven escape due to the accumulation of mutations in the S protein. The inclusion of N protein in the vaccine candidate provides additional conserved T epitopes. Further, the induction of polymeric IgA at mucosal surfaces may be superior for generating neutralizing antibodies against divergent viruses.