Characterization of Spodoptera littoralis type B nucleopolyhedrovirus infection in selected insect cell lines

We have examined Spodoptera littoralis type B nucleopolyhedrovirus (SpliNPV) infections in CLS79, Sf9, and Se1 cells derived from lepidopteran insects of the genus Spodoptera (Family: Noctuidae), Ld652Y cells from Lymantria dispar (Family: Lymantriidae), and Md210 cells from Malacosoma disstria (Family: Lasiocampidae). CLS79, Sf9, and Se1 cells were permissive for SpliNPV infection as these cell lines supported complete viral DNA replication, virus-specific transcription, and production of viable progeny. Neither Ld652Y nor Md210 cells supported production of viable SpliNPV progeny. Ld652Y cells supported limited viral DNA replication and displayed reduced and delayed transcription of viral-specific RNAs. Md210 did not support viral DNA replication and displayed dramatically reduced transcription of viral-specific RNAs. We used transient expression assays as an indirect measure of the translation of SpliNPV early gene products in Sf9, Ld652Y, and Md210 cells. While transactivation of viral promoter-mediated luciferase expression occurred in SpliNPV-infected Ld652Y cells, little to no transactivation activity was detected in SpliNPV-infected Md210 cells. Our data indicated that the block to productive SpliNPV infection in Ld652Y and Md210 cells may be at the level of viral RNA transcription and further suggested that host factors play an important role in productive SpliNPV infection.