Japanese Encephalitis Virus (JEV) NS1′ Enhances the Viral Infection of Dendritic Cells (DCs) and Macrophages in Pig Tonsils

Pigs are the amplifying hosts of Japanese encephalitis virus (JEV). Currently, the safe and effective live attenuated vaccine made of JEV strain SA14-14-2, which does not express NS1′, is widely used in humans and domestic animals to prevent JEV infection. In this study, we constructed the NS1′ expression recombinant virus (rA66G) through a single nucleotide mutation in NS2A of JEV strain SA14-14-2. Animal experiments showed that NS1′ significantly enhanced JEV infection in pig central nervous system (CNS) and tonsil tissues. Pigs shed virus in oronasal secretions in the JEV rA66G virus inoculation group, indicating that NS1′ may facilitate the horizontal transmission of JEV. Additionally, dendritic cells (DCs) and macrophages are the main target cells of JEV infection in pig tonsils, which are an important site of persistent JEV infection. The reduction of major histocompatibility complex class II (MHC II) and activation of inducible nitric oxide synthase (iNOS) in pig tonsils caused by viral infection may create a beneficial environment for persistent JEV infection. These results are of significance for JEV infection in pigs and lay the foundation for future studies of JEV persistent infection in pig tonsils. IMPORTANCE Pigs are amplification hosts for Japanese encephalitis virus (JEV). JEV can persist in the tonsils for months despite the presence of neutralizing antibodies. The present study shows that NS1′ increases JEV infection in pig tonsils. In addition, DCs and macrophages in the tonsils are the target cells for JEV infection, and JEV NS1′ promotes virus infection in DCs and macrophages. This study reveals a novel function of JEV NS1′ protein and lays the foundation for future studies of JEV persistent infection in pig tonsils.