Preclinical mouse studies of vector immunity and long-term responses to CORAVAX, a Rabies virus-vectored COVID-19 vaccine

Abstract The objective of this study is to further analyze the recombinant Rabies virus-vectored SARS-CoV-2 vaccine, CORAVAX, as an effective COVID-19 vaccine strategy. CORAVAX has proven immunogenic and protective against SARS-CoV-2 in animal models. Here, we have screened adjuvants for the highest quality antibody titers, negated the concern of pre-existing Rabies-vector immunity, and established its potential as a long-term COVID-19 vaccine. We have tested TLR4 agonists, inflammasome activators, and Alum adjuvants in CORAVAX and found TLR4-activating MPLA-AddaVax to have the greatest potential. We followed the humoral immune response to CORAVAX in mice with pre-existing Rabies virus immunity and saw no significant differences compared to naïve mice. We then followed the immune response to CORAVAX over several months and 1 year post-immunization. Mice maintained high antigen-specific serum antibody titers as well as long-lived antibody-secreting cells in the spleen and bone marrow. We believe this Rabies-vector strategy combats the problem of waning immunity of other COVID-19 vaccines. These results together support CORAVAX’s potential during the ongoing COVID-19 pandemic.