TIM-1 Promotes Japanese Encephalitis Virus Entry and Infection

Japanese encephalitis virus (JEV) is a mosquito-borne Flavivirus, the leading cause of viral-induced encephalitis. Several host molecules have been identified as the JEV attachment factor; however, the molecules involved in JEV entry remain poorly understood. In the present study, we demonstrate that TIM-1 is important for efficient infection by JEV. Firstly, three TIM-1 variants (V1, V2, and V3) were cloned from A549 cells, and we revealed that only ectopically TIM-1 V2 expression in 293T cells significantly promotes JEV attachment, entry and infection. Point mutation of phosphatidylserine (Ptdser) binding pocket in the TIM-1 IgV domain dampened JEV entry, indicating that TIM-1-mediated JEV infection is Ptdser-dependent. Furthermore, we found the cytoplasmic domain of TIM-1 is also required for enhancing JEV entry. Additionally, knock down of TIM-1 expression in A549 cells impaired JEV entry and infection, but not attachment, suggesting that additional factors exist in A549 cells that allow the virus to bind. In conclusion, our findings demonstrate that TIM-1 promotes JEV infection as an entry cofactor, and the polymorphism of TIM-1 is associated with JEV susceptibility to host cells.