Ribosomal protein L40 promotes cypovirus replication by suppressing the host antiviral immunity in silkworms

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a persistent threat to sericulture and a classic model for insect-reovirus interactions. Here, we investigated the role of Bombyx mori ribosomal protein L40 (BmRPL40) in virus-host interactions using this model. We found that BmCPV infection significantly downregulated host BmRPL40 expression. Both knockdown and overexpression experiments further demonstrated that BmRPL40 expression levels were positively correlated with viral replication. Moreover, BmRPL40 overexpression suppressed the IMD and Toll pathways, thereby impairing host immunity and facilitating viral replication. Accordingly, upon BmCPV infection, the host downregulates BmRPL40 to counteract its immunosuppressive effects and enhance antiviral defense. Collectively, these findings reveal a mechanism by which the silkworm modulates viral replication and activates host defense through BmRPL40 expression, offering critical insights into virus-host interactions at the translational level.