Messenger RNA translation enhancement by immune evasion proteins: a comparative study between EKB (vaccinia virus) and NS1 (influenza A virus).

In this study, we compared vaccinia virus derived monofunctional E3, K3 and B18R (also known as EKB) with influenza A virus derived multifunctional non-structural protein 1 (NS1) based on their ability to enhance mRNA translation. EKB and NS1-TX91 were all found to enhance mRNA translation and suppress interferon production, yet level of enhancement by EKB was much lower than NS1-TX91. Similarly, greater luciferase expression was mediated by co-delivery of unmodified luciferase with NS1 mRNA, compared to co-delivery of unmodified luciferase with either E3, K3 or B18R mRNA, respectively. Different combinations of E3, K3 and/or B18R mRNA were mixed with NS1-TX91 mRNA at varying ratios and co-delivered with luciferase mRNA. However, no synergism was observed as mRNA translation enhancement mediated by NS1-TX91 could not be improved by the inclusion EKB in all tested combinations. Lastly, it was found that E3 was able to rescue mRNA translation enhancement mediated by NS1 PKR knockout mutant (PR8), suggesting that one of NS1's multiple immune evasion mechanisms overlapped with E3. Altogether, our data validated mRNA translation enhancement mediated by immune evasion proteins (EKB and NS1) and showed that the multifunctional nature of NS1 accounted for its superior performance.