BV/ODV-E26 is a conserved baculoviral inhibitory factor for optimizing viral virulence in lepidopteran hosts.

Alphabaculoviruses induce abnormal behavior in lepidopteran larval hosts. A baculoviral gene, , is crucial for behavioral manipulation in larvae by Bombyx mori nucleopolyhedrovirus (BmNPV). However, how fulfills its role in this phenotype remains largely unknown. In this study, we found that the overexpression of BmNPV delayed viral infection in cultured cells and decreased pathogenicity in larvae. We also discovered that homologs of are conserved more widely in alphabaculoviruses than previously thought. The inhibitory activity was demonstrated in homologs of phylogenetically close and distant baculoviruses, indicating conserved inhibitory function among alphabaculoviruses. Furthermore, locomotory analyses revealed that increased larval locomotory activity but had little effect on the timing of abnormal behavior initiation. Collectively, our findings demonstrate that is a baculoviral inhibitory factor that is widely conserved in the genus and may reduce viral virulence for successful host behavioral manipulation.