Two amino acid pairs in the glycoprotein of severe fever with thrombocytopenia syndrome virus responsible for the enhanced virulence

Severe fever with thrombocytopenia syndrome (SFTS) virus poses a major public health threat, with high mortality rates in both humans and cats. This study investigates the genetic factors underlying the differing virulence of SFTS virus (SFTSV) strains Tk-F123 and Ng-F264, isolated from cats. In type I interferon receptor-knockout mice, the Tk-F123 strain was uniformly lethal, while the Ng-F264 strain caused no fatalities. A critical difference was identified in the Gc protein: Tk-F123 encodes glycine and serine at residues 581 and 934, respectively, whereas Ng-F264 encodes arginine and asparagine at these positions. These amino acid differences significantly impact Gc protein function, modulating SFTSV virulence. These findings offer valuable insights into the molecular mechanisms of SFTSV pathogenicity and could guide the development of live-attenuated vaccines and antiviral therapies.
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