Antiviral immune responses of Bombyx mori cells during abortive infection with Autographa californica multiple nucleopolyhedrovirus

•Multiple antiviral responses are activated in Bombyx mori cells upon AcMNPV infection.•These include apoptosis, global protein synthesis shutdown, and rRNA degradation.•Apoptosis and global protein synthesis shutdown occur upon viral DNA replication.•rRNA is degraded prior to viral DNA replication as the primary antiviral response.•AcMNPV(Δp35) triggers more prominent apoptosis than BmNPV(Δp35) in B. mori cells. Lepidopteran cells rely on multiple antiviral responses to defend against baculovirus infections, including apoptosis, global protein synthesis shutdown, and rRNA degradation. Here, we characterized apoptosis and rRNA degradation in Autographa californica multiple nucleopolyhedrovirus (AcMNPV)-infected Bombyx mori cells, a system resulting in abortive infection, in relation to viral DNA replication and viral late gene expression. RNAi-mediated silencing of viral DNA replication-related genes prevented apoptosis, but not rRNA degradation, in B. mori cells infected with p35-deficient AcMNPV. Additionally, AcMNPV, but not B. mori nucleopolyhedrovirus (BmNPV), drastically reduced B. mori cellular iap1 transcript levels and p35-deficient AcMNPV induced more prominent apoptosis than did p35-deficient BmNPV. These results, together with previous results that global protein synthesis shutdown follows viral DNA replication, demonstrate that rRNA degradation is the primary antiviral response that abolishes productive AcMNPV infection of B. mori cells. Our results also demonstrate that B. mori cells induce apoptosis to a different extent depending on NPV species.