The Japanese encephalitis virus NS1′ protein facilitates virus infection in mosquitoes

Background The Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is known for its capacity to cause severe neurological disease in Asia. Neurotropic flaviviruses within the Japanese encephalitis (JE) serogroup possess the distinctive feature of expressing a unique nonstructural protein, NS1 '. The NS1 ' protein consists of the full NS1 protein with an additional 52 amino acid extension at the C-terminus and has been demonstrated to exhibit virulence in mammalian hosts upon infection. However, the precise role of the NS1 ' protein in the mosquito vectors has yet to be elucidated.Methodology/principal findings In this study, an NS1 '-defective virus (rG66A) was engineered, and its effect on the infection of mosquito cells was investigated. The results demonstrated a significant reduction in the infectivity of the rG66A virus in mosquito cells by RT-qPCR, indicating that the absence of the NS1 ' protein impedes JEV replication in Culex mosquitoes. Additionally, this research elucidated the underlying mechanism by which the NS1 ' protein enhances viral infection in mosquitoes by RNA-Seq analysis. Specifically, the NS1 ' protein was found to facilitate infection through the suppression of antimicrobial peptides (AMPs) regulated by the Toll pathway.Conclusions/significance Our research demonstrated that the JEV NS1 ' protein contributes to immune escape, thereby enhancing viral infection in mosquitoes. This finding offers new insights into the transmission mechanisms of JEV, elucidating novel aspects of viral propagation.