mRNA vaccines induce rapid antibody responses in mice.

mRNA vaccines can be developed and produced quickly, making them prime candidates for immediate outbreak responses. Furthermore, clinical trials have demonstrated rapid protection following mRNA vaccination. Thus, we sought to investigate how quickly mRNA vaccines elicit antibody responses compared to other vaccine modalities. We first compared the immune kinetics of mRNA and DNA vaccines expressing SARS-CoV-2 spike in mice. We observed rapid induction of antigen-specific binding and neutralizing antibodies by day 5 following mRNA (4 µg/mouse), but not DNA (50 µg/mouse), immunization. Comparing innate responses hours post immunization, the mRNA vaccine induced increased levels of IL-5, IL-6, and MCP-1 cytokines which maybe promoting humoral responses downstream. We then evaluated the immune kinetics of an HIV-1 mRNA vaccine in comparison to DNA, protein, and rhesus adenovirus 52 (RhAd52) vaccines of the same HIV-1 envelope antigen in mice. Again, induction of envelope-specific antibodies was observed by day 5 following mRNA vaccination, whereas antibodies were detected by day 7-14 following DNA, protein, and RhAd52 vaccination. Thus, eliciting rapid humoral immunity may be a unique and advantageous property of mRNA vaccines for controlling infectious disease outbreaks.