Development and Evaluation of Two Double-Antibody Sandwich ELISAs for Detecting Severe Fever with Thrombocytopenia Syndrome Virus Infection

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly emerging tick-borne virus with a fatality rate between 12% and 50%. Currently, effective vaccines or antiviral drugs are not available to treat SFTSV infection, and a diagnostic method for its detecting is urgently needed. Monoclonal (MAb) and polyclonal antibodies (PAbs) against SFTSV were prepared by immunizing animals with the SFTSV nucleocapsid protein (NP). We developed 2 double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) to detect the SFTSV NP, which was captured using the MAbs and PAbs generated. Both methods were applicable for the diagnosis of SFTSV-infected patients, as confirmed by a quantitative polymerase chain reaction. Furthermore, the sensitivity and specificity of the 2 assays for diagnosing severe fever with thrombocytopenia syndrome were 100% and the antibodies did not react with recombinant Dabieshan NP or recombinant dengue virus NS1 subtype 1 and 2 proteins. In addition, 2 standard curves were established for quantitative detection of the NP: the monoclonal antibody-based ELISA (MAb-based ELISA) had a lower limit of detection than the polyclonal-based ELISA. Therefore, the MAb-based ELISA can be employed for convenient and effective detection of SFTSV.