PNNL

Abstract

Like SARS-CoV a decade earlier, MERS-CoV maintains a mix of highly conserved and novel genetic elements necessary for infection and pathogenesis. In this study, we focus on the highly conserved function of non-structural protein (NSP) 16, a viral 2’O methyl-transferase (MTase) previously implicated as critical in immune modulation and infection. With this in mind, we disrupted a key motif in the conserved KDKE motif of MERS NSP16 (D130A) and evaluated the effect on viral infection and pathogenesis. Similar to previous reports, the absence of 2’O MTase activity had only marginal impact on propagation and replication in Vero cells. However, both in primary human airway cultures and in vivo, the MERS dNSP16 mutant demonstrated significant attenuation relative to control. Further examination indicated the MERS dNSP16 mutant had a type I IFN based attenuation and was partially restored in the absence of IFIT molecules. Importantly, the robust attenuation permitted use of MERS dNSP16 as a live attenuated vaccine platform protecting from challenge with a mouse adapted MERS-CoV strain. Together, the results demonstrate the importance of 2’O MTase activity for CoV pathogenesis and highlights NSP16 as a conserved target for therapeutic treatment.