The mRNA vaccine encoding Gc protein confers complete protection against severe fever with thrombocytopaenia syndrome virus.

Severe fever with thrombocytopaenia syndrome virus (SFTSV), an emerging tick-borne pathogen, causes haemorrhagic fever in infected patients and is associated with a high mortality rate in humans. The imperative need for vaccines against this lethal virus is underscored by a lack of effective preventive measures. The results of this study yield notable advancements: the successful development of an SFTSV mRNA vaccine encoding the glycoprotein C (Gc) gene, achieving N-linked glycosylation in the expressed protein. This vaccination regimen induced a balanced TH1/TH2 immune response and elicited robust levels of both cellular and humoral immunity in C57BL/6 and IFNAR-/- mice. The results of the present study demonstrate that immunization with 1 μg mRNA vaccine provides complete protection (100 %) against lethal SFTSV infection (77,000 LD50) in IFNAR-/- mice. Moreover, the vaccine candidate induces long-lasting immunity and confers protection against SFTSV for at least six months. Notably, the antibody provides 100 % protection according to passive transfer assays, suggesting that humoral immunity plays a crucial role in resisting SFTSV challenge. These findings present a promising stride forward in the quest for an effective vaccine against SFTSV, highlighting the potential of the developed mRNA vaccine in conferring substantial immunity.