Pigs are amplification hosts for Japanese encephalitis virus (JEV). JEV can persist in the tonsils for months despite the presence of neutralizing antibodies.
Japanese encephalitis virus (JEV), a mosquito-borne zoonotic virus, is one of the most important causes of human viral encephalitis. JEV relies on various attachment or entry co-factors to enter host cells. Among these co-factors, hTIM-1 has been identified as an attachment factor to promote JEV infection through interacting with phosphatidylserine (PS) on the viral envelope. However, the reasons why JEV prefers to use hTIM-1 over other PS binding receptors are unknown. Here, we demonstrated that hTIM-1 can directly interact with JEV E protein. The interaction between hTIM-1 and JEV relies on specific binding sites, respectively, ND114115 in the hTIM-1 IgV domain and K38 of the E protein. Furthermore, during the early stage of infection, hTIM-1 and JEV are co-internalized into cells and transported into early and late endosomes. Additionally, we found that the hTIM-1 soluble ectodomain protein effectively inhibits JEV infection in vitro. Moreover, hTIM-1-specific antibodies have been shown to downregulate JEV infectivity in cells. Taken together, these findings suggested that hTIM-1 protein directly interacts with JEV E protein and mediates JEV infection, in addition to the PS-TIM-1 interaction.
Japanese encephalitis virus (JEV) is a mosquito-borne Flavivirus, which may cause severe encephalitis in humans, horses, and other animals. TIM-1 has been identified to be a receptor that promotes various viruses to enter into target cells in recent years. In the present study, we found that TIM-1 protein was significantly increased in A549 cells at the late stage of JEV infection, while the transcription levels of TIM-1 remained unaltered. Interestingly, we found that NS1’ protein plays a key role in increasing the expression of TIM-1 in cells infected with JEV. Further, we found that the NS1’ protein also efficiently regulates TIM-1 protein to distribute in the cytoplasm in JEV-infected cells, and the amount of TIM-1 protein located on the cell membrane was reduced instead. As a consequence, NS1’ protein antagonize TIM-1 mediated viral restriction for further viral infection and propagation in the late stage of infection. In molecular mechanism, the molecular weight of TIM-1 increased a bit in the present of NS1’. Expression of NEU1 down-regulated TIM-1 expression and oseltamivir treatment increased the expression of TIM-1. Therefore, our data indicated that JEV NS1’ protein facilitated the sialylation modification of TIM-1 to up-regulate the level of TIM-1 expression and regulate its distribution. Collectively, our study revealed that JEV NS1’ protein regulates the expression and distribution of TIM-1 by facilitating its sialylation to antagonize TIM-1-mediated JEV restriction for further infection. Understanding the functional interplays between TIM-1 and NS1’ proteins will offer new insights into virus-host interaction.
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