Study on protective immunity induced by severe fever with thrombocytopenia syndrome virus DNA vaccine

Abstract

Although the incidence of severe fever with thrombocytopenia syndrome virus (SFTSV) infection has increased from its discovery with a mortality rate of 10–20%, no effective vaccines are currently available. DNA plasmids encoding SFTSV proteins were developed as preventive vaccine against SFTS. The study describes immunogenicity and protective efficacy of SFTSV DNA vaccine by immunizing mouse, ferret, monkey model. Vaccine candidates induced both a neutralizing antibody response and multifunctional SFTSV-specific T-cell response in animal models. When the vaccine efficacy was investigated in aged-ferrets that recapitulate fatal clinical symptoms, vaccinated ferrets were completely protected from lethal SFTSV challenge without developing any clinical signs. The results suggested that anti-envelope antibodies play an important role in protective immunity by a serum transfer study and non-envelope-specific T-cell responses also can contribute to protection against SFTSV infection. Moreover, vaccinated monkey possessed robust T-cell responses, similar to the magnitude of that elicited by infection in SFTS patients, and cross-reactive antibody responses to two different genotypes of SFTSV strain. This study provided important insights into the development of an effective vaccine, as well as corresponding immune parameters, to control SFTSV infection.