Injection site fibroblasts are highly enriched with delivered mRNA and express IFN-β specifically in response to the mRNA component.
Lipid nanoparticles (LNP) trigger pro-inflammatory responses at the injection site.
Type I interferon responses are a dominant feature of the immune reaction to mRNA vaccines.
Migratory dendritic cells expressing interferon-stimulated genes are induced by mRNA-LNP but not by LNP alone.
Co-injection of IFN-β with an LNP-subunit vaccine enhances antigen-specific cellular immune responses.
Blocking IFN-β signaling reduces cellular immune responses induced by the .
Simplified
mRNA vaccines against SARS-CoV-2 have revolutionized vaccine development, but their immunological mechanisms are not fully understood. Here, we investigate injection site responses of mRNA vaccines by generating a comprehensive single-cell transcriptome profile upon lipid nanoparticle (LNP) or LNP-mRNA challenge in female BALB/c mice. We show that LNP-induced stromal pro-inflammatory responses and mRNA-elicited type I interferon responses dominate the initial injection site responses. By tracking the fate of delivered mRNA, we discover that injection site fibroblasts are highly enriched with the delivered mRNA and that they express IFN-β specifically in response to the mRNA component, not to the LNP component of mRNA vaccines. Moreover, the mRNA-LNP, but not LNP alone, induces migratory dendritic cells highly expressing IFN-stimulated genes (mDC_ISGs) at the injection site and draining lymph nodes. When co-injected with LNP-subunit vaccine, IFN-β induces mDC_ISGs at the injection site, and importantly, it substantially enhances antigen-specific cellular immune responses. Furthermore, blocking IFN-β signaling at the injection site significantly decreases -induced cellular immune responses. Collectively, these data highlight the importance of injection site fibroblasts and IFN-β signaling during early immune responses against the mRNA vaccine and provide detailed information on the initial chain of immune reactions elicited by mRNA vaccine injection.
Key numbers
Substantial
Cellular Immune Response Increase
Co-injection of IFN-β with LNP-subunit vaccines
Significant
Decrease in Immune Response
Compared to LNP+mRNA vaccination
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