Microscopic Investigations of the Infection Process of Choristoneura Fumiferana Nucleopolyhedrovirus in the Spruce Budworm

Choristoneura fumiferana nucleopolyhedrovirus(CfMNPV) is a baculovirus that infects the spruce budworm, Choristoneura fumiferana(Cf), and a few other related species. To study the infection process of this virus within the spruce budworm, we have constructed a recombinant virus (CfMNPV-GFP) expressing the green fluorescence protein(GFP) under the control of the polyhedrin promoter of Autographa californica nucleopolyhedrovirus. Each larva was fed 10,000 CfMNPV-GFP occlusion bodies(OB) applied to diet plugs and various tissues were dissected from the larvae at 24 hr intervals and examined for the presence of the OB and/or GFP using a fluorescence microscope. Larvae were also fixed and embedded for light and electron microscopy. GFP-specific fluorescence was first detected as a few spots at the posterior end of the midgut at 72 hr post feeding(PF). By 96 hr PF, the fluorescence had expanded to include adjacent cells and some hemocytes.