Project description:mRNA vaccines are emerging as a powerful vaccine platform as they are well-tolerated and scalable. Modified non-replicating mRNA encoding Influenza hemagglutinin and encapsulated in lipid nanoparticles (LNP) induced robust antibody and CD4 T cell responses after intramuscular or intradermal delivery in rhesus macaques. We investigated the local innate immune responses modulating such vaccine-induced immunity at the sites of immunization (skeletal muscle and skin) and their draining lymph nodes (LNs). Rapid mobilization of antigen presenting cells was found at the LNP/mRNA-injection sites and LNs. Dendritic cells efficiently internalized the LNPs, translated the mRNA cargo and upregulated co-stimulatory molecules. In addition, several type I interferon-inducible genes were expressed at the immunization sites and draining LNs. The innate immune activation was transient and resulted in priming of antigen-specific CD4+ T cells exclusively in the vaccine-draining LNs. Collectively, mRNA-based vaccines induce type I interferon-polarized innate immunity and antigen production by antigen presenting cells, which resulted potent vaccine-specific responses.
