Different Susceptibility of Mammalian Cell Lines to Severe Fever with Thrombocytopenia Syndrome Virus Infection

Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging tick-borne infectious disease that poses a significant public health threat. SFTS virus (SFTSV) has a broad host range, including humans, cats, and natural reservoir species. Therefore, cultured cell lines derived from different mammalian species are useful for understanding the susceptibility of SFTSV in hosts. In this study, we evaluated pathogenicity and infectivity, focusing on cytopathic effect (CPE) induction and growth kinetics of SFTSV in several mammalian cell lines, including our original tiger-derived TLT, wild deer-derived DFKT and DFLT, and hedgehog-derived HHoVT. Following SFTSV infection, TLT, CRFK (cat), FCWF-4 (cat), and CPK (porcine) cells exhibited CPE, whereas Vero E6 (monkey), A549 (human), BHK-21 (hamster), DFKT, DFLT, and HHoVT cells did not. Infectious viral yields in the supernatants of TLT, CRFK, FCWF-4, Vero E6, and BHK-21 were higher than those of CPK, A549, DFLT, and DFKT. SFTSV infection in hedgehog-derived HHoVT cells was very limited. These observations suggest that features such as viral CPE and virus yield following SFTSV infection depend on cell type. It is noteworthy that TLT formed clear plaques that were easy to count, indicating that TLT cells are useful for the titration of infectious SFTSV by plaque-forming assay. Our results provide useful information and tools for further elucidating the mechanisms of SFTSV infectivity, proliferation, and pathogenicity using in vitro models.