Influenza A virus derived NS1 enhances translation of HPLC purified mRNA and interferon adjuvanted mRNA vaccination

Non-structural protein (NS1) derived from influenza A virus is a potent immune evasion protein capable of enhancing translation of nucleoside-modified mRNA via host gene expression inhibition (HGEI) effect. In this study, we show that the HGEI effect on NS1 transfected cells reduces de novo synthesis and polyadenylation of host RNA. Co-delivering NS1 mRNA also enhances translation of non-inflammatory nucleoside-modified and HPLC-purified mRNA in NIH3T3 cells. Co-delivering NS1 mRNA also enhances translation of nucleoside-modified mRNA in DCs by 100% based on GFP expression, but completely inhibits cytokine induced maturation of primary human dendritic cells (DCs). Co-delivering NS1 mRNA also significantly enhances in vivo translation of naked mRNA via intramuscular route with transgene expression persisting for 12 days. As a proof of concept to mimic natural viral infection, when mRNAs encoding NS1 and interferon alpha were co-delivered, translation inhibition of the reporter gene was rescued both in vitro and in vivo. Using ovalbumin as a model antigen, we show that humoral response in C57BL/6 mice was enhanced when naked mRNAs encoding ovalbumin, NS1 and IFN were delivered together via intramuscular route. These novel properties of NS1 have the potential to impact mRNA therapeutics in significant ways.