Replication of nucleopolyhedroviruses of Autographa californica (Lepidoptera: Noctuidae), Bombyx mori (Lepidoptera: Bombycidae), Hyphantria cunea (Lepidoptera: Arctiidae), and Spodoptera exigua (Lepidoptera: Noctuidae) in four lepidopteran cell lines

Abstract

Four different NPV isolates from Autographa californica (AcNPV), Bombyx mori (BmNPV), Hyphantria cunea (HcNPV) and Spodoptera exigua (SeNPV) were characterized for their biological properties in four lepidopteran cell lines which were derived from S. frugiperda (IPLB-Sf-21), B. mori (BmN-4), Spilosoma imparilis (FRI-SpIm-1229), and S. exigua (Se301). On the basis of the data on viral DNA replication, viral structural protein synthesis, budded virion (BV) yield, polyhedrin synthesis, and polyhedral formation in the infected cells, it was demonstrated that each of these NPV isolates established specific interactions with the respective cell lines. Of 16 NPV-cell systems examined, three NPV-cell systems exhibited two different types of abortive infection. In HcNPV-infected BmN-4 cells, viral DNA replication occurred but the infection aborted at the step prior to late gene expression, whereas both AcNPV-infected BmN-4 cells and HcNPV-infected IPLB-Sf-21 cells yielded BVs into culture medium but were defective in polyhedrin expression. In addition, it was found that SeNPV exhibited a unique infection process in FRI-SpIm-1229 cell cultures, in which viral DNA replicated and a limited number of polyhedra were formed in a restricted number of infected cells while few, if any, progeny BVs were produced and a significant proportion of infected cells displayed apoptotic-like morphology. The present study, thus, developed various NPV-cell systems which facilitate the analysis of molecular mechanisms underlying baculovirus host specificity determination.