Expression kinetics and innate immune response after electroporation and lipid nanoparticle-mediated delivery of a self-amplifying mRNA in the skin of mice

In this work, we studied the expression kinetics and innateimmune response of a self-amplifying mRNA (sa-RNA) after electroporationand lipid-nanoparticle (LNP)-mediated delivery in the skin of mice. Intradermal electroporationof the sa-RNA resulted in a plateau-shaped expression, with the plateau between day 3 and day 10. The overall protein expression of sa-RNA was significantly higher than that obtained after electroporationof plasmid DNA (pDNA) or non-replication mRNAs. Moreover, using IFN-β reporter mice, we elucidated that intradermal electroporationof sa-RNA induced a short-lived moderate innateimmune response, which did not affect the expression of the sa-RNA. A completely different expression profile and innateimmune response were observed when LNPs were used. The expression peaked 24 h after intradermal injectionof sa-RNA-LNPs and subsequently showed a sharp drop. This drop might be explained by a translational blockage caused by the strong innateimmune response that we observed in IFN-β reporter mice shortly (4 h) after intradermal injectionof sa-RNA-LNPs. A final interesting observation was the capacity of sa-RNA-LNPs to transfect the draining lymph nodes after intradermal injection.