Hexavalent coronavirus vaccine elicits both humoral and cellular immune responses in mice

Abstract Coronaviruses have caused three deadly human outbreaks over the last 20 years, the latest causing the COVID-19 pandemic which has now lasted over three years. The animal reservoir of coronaviruses is extensive, and history has shown that coronaviruses are able to crossover from animals to humans. Thus, there is a clear need for a universal coronavirus vaccine. In this study, we produced S1 subunits of spike proteins of six different human coronaviruses fused to the antibody Fc fragment in HEK293 cells. In addition, we produced another coronavirus protein (CP) in High Five™ insect cells. The vaccine compositions included either the six S1-Fc or the six S1-Fc together with CP, and mice were immunized either intranasally or with a combination method utilizing both subcutaneous and intranasal injections. Our results showed that both vaccine compositions elicited both humoral and cellular immune responses in mice. Antigen-specific IgG levels were higher in mice immunized solely intranasally but using a combination of different immunization routes seemed to boost cellular immune responses. As a conclusion, all the vaccine compositions were highly immunogenic and generated both antibody and T cell responses in mice. Further studies are needed to optimize the immunization scheme. Additionally in the future, in order to better characterize the T cell responses generated by intranasal immunization, the nasal associated lymphoid tissue and cervical lymph nodes from the mice will be collected and analyzed. Supported by a grant from The Research Foundation of the Pulmonary Diseases (Finland)