Impact of deletion of the Lymantria dispar nucleopolyhedrovirus PEP gene on viral potency: Expression of the green fluorescent protein prevents larval liquefaction

The Lymantria dispar multicapsid nucleopolyhedrovirus (LdMNPV) is an effect ive biological control agent of the gypsy moth, L. dispar, but is not in ge neral use because the high cost of production limits availability. In an ef fort to generate a more cost efficient LdMNPV biopesticide, two recombinant baculoviruses were generated to evaluate the impact of deleting the polyhe dral envelope protein (PEP) gene on viral potency. One of these baculovirus es had the PEP gene inactivated by insertional mutagenesis with the green f luorescent protein (GFP) gene from Aequorea victoria (vGFP: PEP-); and the other contained a partial deletion of the PEP gene from the LdMNPV viral ge nome (vPEP-), Both recombinant baculoviruses produced polyhedra that were l acking a polyhedral envelope and displayed an unusually pitted surface as a nalyzed by scanning and transmission electron microscopy. Polyhedra produce d by vGFP:PEP- were considerably smaller than those produced by vPEP- or wi ld-type virus. Although vPEP- and vGFP:PEP- polyhedra exhibited abnormal ph enotypes, bioassay results indicated that there was no significant differen ce in the potency of these polyhedral envelope-lacking polyhedra in compari son to wildtype polyhedra, In addition, expression of GFP prevented virus-i nduced larval liquefaction upon death, and the deletion of PEP prevented ly sis of infected cells in culture.