New cell lines from heliothis virescens: characterization and susceptibility to baculoviruses

New cell lines from embryos of Heliothis virescens were recently developed. Six primary cultures were initiated in June 1995. From these initial cultures, two produced sufficient cell growth to allow subcultivation and eventually led to the establishment of seven cell strains, three of which are maintained at low temperatures (17 degreesC). The strains were compared with a previously established cell line from H. virescens by isozyme analysis and shown to be from the same species. All the strains were inoculated with various baculoviruses, including Autographa californica nucleopolyhedrovirus (NPV), Anagrapha falcifera NPV, Anticarsa gemmatalis NPV, Rachoplusia ou NPV, Lymantria dispar NPV (LdMNPV), Orgyia pseudotsugata NPV (OpSNPV), O. leucostigma NPV (OlMNPV), and Helicoverpa zea NPV (HzSNPV). All seven strains were highly susceptible to the noctuid NPVs, and large numbers of occlusion bodies (OBs) were produced in most of the inoculated cells. The HzSNPV infection developed at a slower rate (requiring 1 week or more before a substantial number of cells contained OBs compared with 2-3 days for the other three noctuid NPVs). Three of the H. virescens strains were also susceptible to OpSNPV although only 10-20% of the cells produced OBs with this virus. We did not observe cytopathology (CPE) in any cells inoculated with OlMNPV or LdMNPV. Our results suggest that these new strains can be useful for the study and possibly the production of baculoviruses for which no effective cell systems are available and for comparative studies on multiple virus species.