Immunogenicity of Double-Stranded RNA in mRNA Vaccines and its Impact on Immune Cell Function 2335037

Introduction Double-stranded RNA (dsRNA) is a natural activator of innate immune responses in mammalian cells and can form as a limited byproduct during in vitro transcription of mRNA vaccines Methods We sought to further characterize humoral and cell-mediated immune responses to varying levels of dsRNA using a prototype nucleoside-modified mRNA (modRNA) based respiratory syncytial virus (RSV) vaccine. The modRNA lipid nanoparticle formulations contained defined quantities of a full-length dsRNA generated from complementary sense and antisense strands of RSV modRNA. Results In vivo analysis in BALB/c mice revealed that increasing levels of dsRNA impurities in a modRNA LNP vaccine delivered intramuscularly led to a modest induction of inflammatory cytokines, including Type I interferons, but had no effect on neutralizing antibody titers or the functionality of CD4+ and CD8+ T cells. In parallel, in vitro analysis of human PBMCs exposed to the same formulations showed no significant changes in inflammatory cytokine production or cell-mediated immunity; Increasing levels of dsRNA impurities did not alter population composition, antigen-presenting cell (APC) activation, or CD4+ and CD8+ T cell exhaustion, indicating limited immunostimulatory potential of N1-Methylpseudouridine (m1ψ) modified dsRNA in immune cells. Conclusion Together, these results improve our understanding of potential dsRNA impurities and immune responses in mRNA vaccines.