UNICOR-v, a Pan-Coronavirus Subunit Vaccine, Demonstrates Immunogenicity and Efficacy Against MERS-CoV Infection

Coronaviruses are a family of positive-sense RNA viruses that cause respiratory and gastrointestinal disease in mammals and birds. Their zoonotic nature and high mutability make them a pandemic threat. UNICOR-v is a pre-pandemic, pan-coronavirus vaccine composed of an adjuvanted mix of twelve synthetic peptides originating from conserved regions within Nsp12 and M coronavirus proteins containing clusters of predicted T-cell epitopes. Here, we evaluate the immunogenicity of UNICOR-v and its efficacy against Middle East Respiratory Syndrome-related coronavirus (MERS).

Animals were vaccinated with an adjuvanted equimolar mix of UNICOR-v. Humoral and cellular immunogenicity were assessed 28 days later through ELISA and FLUOROSpot. Vaccine efficacy was assessed in a DPP4 knock-in (HDPP4-KI) mouse model where mice were challenged post-vaccination with a lethal or non-lethal dose of MERS-CoV-MA.

Vaccination with UNICOR-v induced high IgG titers in both mice and rabbits and cellular secretion of pro-inflammatory cytokines. Vaccination with UNICOR-v, or passive serum transfer, significantly reduced viral lung titers 4 days post-infection compared to placebo. Vaccination induced lower immune cell infiltration in the alveolar space and increased repair of the cells lining the major airways in vaccinated mice, translating to increased survival rate compared to placebo.

These data demonstrate the ability of conserved T-cell epitopes to protect against MERS-CoV infection, supporting further characterization of the breadth of protection of UNICOR-v against other coronaviruses that affect humans and livestock, following a One Health approach to control this highly zoonotic family of viruses.