Restriction of Bombyx mori Nucleopolyhedrovirus (NPV) Replication by Hyphantria cunea NPV in a Cell Line from B. mori

Abstract

BmN-4 cells from the silkworm, Bombyx mori, are permissive for B. mori nucleopolyhedrovirus (BmNPV) replication, whereas infection of BmN-4 cells with Hyphantria cunea NPV (HycuNPV) results in an abortive infection at the step before viral late gene expression. In this study, we found that coinfection of BmN-4 cells with BmNPV and HycuNPV led to severe restriction of BmNPV replication accompanying restricted BmNPV DNA replication and total shutdown of protein synthesis. Northern blot hybridization analysis showed that immediate early gene transcripts of both BmNPV and HycuNPV accumulated abundantly in BmN-4 cells coinfected with BmNPV and HycuNPV. These results indicate that restriction of BmNPV replication in the coinfected BmN-4 cells occurs at a post-entry step prior to viral DNA replication. Superinfection experiments further demonstrate that an intracellular environment that restricts BmNPV replication is established in BmN-4 cells shortly after HycuNPV infection.