Reverse Genetics System for Severe Fever with Thrombocytopenia Syndrome Virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne pathogen that was first reported in China in 2009. Phylogenetic analysis of the viral genome showed that SFTS virus represents a new lineage within the Phlebovirus genus, distinct from the existing sandfly fever and Uukuniemi virus groups, in the family Bunyaviridae. SFTS disease is charac-terized by gastrointestinal symptoms, chills, joint pain, myalgia, thrombocytopenia, leukocytopenia, and some hemorrhagic manifestations with a case fatality rate of about 2 to 15%. Here we report the development of reverse genetics systems to study STFSV replication and pathogenesis. We developed and optimized functional T7 polymerase-basedM- and S-segment minige-nome assays, which revealed errors in the published terminal sequences of the S segment of the Hubei 29 strain of SFTSV.We then generated recombinant viruses from cloned cDNAs prepared to the antigenomic RNAs both of the minimally passaged vi-rus (HB29) and of a cell culture-adapted strain designated HB29pp. The growth properties, pattern of viral protein synthesis, and subcellular localization of viral N and NSs proteins of wild-type HB29pp (wtHB29pp) and recombinant HB29pp viruses were indistinguishable. We also show that the viruses fail to shut off host cell polypeptide production. The robust reverse genet-ics system described will be a valuable tool for the design of therapeutics and the development of killed and attenuated vaccines against this important emerging pathogen. IMPORTANC