In vitro culture of Lambdina fiscellaria lugubrosa nucleopolyhedrovirus in heterologous cell lines.

Infections of two heterologous insect cell lines derived from Malacosoma disstria (Md108) and Choristoneura fumiferana (Cf70) by the Lambdina fiscellaria lugubrosa nucleopolyhedrovirus (LafiNPV-W) were characterized. Cytopathic effects characteristic of LafiNPV-W infection, including rounding of cells, nuclear hypertrophy, and occlusion body (OB) production, were observed in both cell lines. Budded virus titers were slightly higher in Md108 cells than Cf70 cells (5.8 x 10(7) versus 3.1 x 10(7) TCID(50) units mL(-1)). Viral replication kinetics and cytopathic effects induced by LafiNPV-W infection were very similar in both cell lines. Actin rearrangements and redistribution of heterochromatin and euchromatin were observed within 24 h post-inoculation (hpi), and large quantities of nucleocapsids and virions were observed by electron microscopy at 48 hpi in both cell lines. Cf70 cultures produced OBs with numerous embedded virions, while OBs in Md108 cultures contained few virions or were empty with nucleocapsids packed in the nucleoplasm between OBs. In bioassays against second instar L. fiscellaria lugubrosa, OBs derived from LafiNPV-W-infected Md108 cells induced significantly lower levels of mortality than OBs derived from LafiNPV-W-infected Cf70 cells or from infected L. fiscellaria fiscellaria larvae.