While the genomes of Choristoneura fumiferana (spruce budworm) and its viruses are being sequenced, the functions of most of the putatively expressed proteins remain to be established. Though computer programs have been developed to predict functions of proteins based on the genomic information, it is only through practical studies at the protein level that functions will be verifiably assigned. Moreover mRNA expression does not parallel protein expression in many cases. The goal of this study is to investigate the functions of some of these proteins employing both the traditional and ‘genomic’ methods. When insect cells are infected by C. fumiferana (Cf) entomopoxvirus (EPV), two distinct types of inclusion body are present in the infected cells. The larger of these, termed spheroids, consist of the virions, and the proteins that make up the matrix of these occlusion bodies are called spheroidin. The other type of inclusion body is called spindles and they are found within the spheroids. The spindles do not contain virus particles. The matrix of the spindles seems to be composed of a single protein called fusolin. The exact functional role of fusolin is not known. Though it has been demonstrated by some researchers that spindle particles enhance nucleopolyhedrovirus (NPV) infection in insects, this enhancing function cannot be considered to be the native biological activity of the spindles. It is one of our goals to define the biological functions of the CfEPV fusolin. As new biologic insecticides for controlling spruce budworm are being developed by DNA recombinants, little is known about the innate immunity in this insect. It is the goal of this study to investigate the role of immune responses to viral and bacterial infections in spruce budworm. An understanding of the immune genes in spruce budworm would certainly be helpful in designing new biologic insecticides.