PURIFICATION AND ANALYSIS OF A POLYDNAVIRUS GENE-PRODUCT EXPRESSED USING A POLY-HISTIDINE BACULOVIRUS VECTOR

The VHv1.1 polydnavirus gene has been implicated in suppressing the en capsulation response in parasitized insects [Li and Webb (1994) J, Vir ol. 68, 7482-7489]. In order to characterize this gene product and to further our analysis of its immunosuppressive function, we expressed t he VHv1.1 using a custom-designed C-terminal poly-histidine baculoviru s vector which allows for high expression and single-step purification of the protein, The 34 kDa VHv1.1 protein was expressed in baculoviru s-infected cell cultures and in H. virescens larvae. Highly enriched p reparations of the secreted VHv1.1 protein were obtained after affinit y chromatography using a NTA-(Ni2+) resin, Characterization with purif ied preparations of the VHv1.1 protein established that the protein is N-glycosylated, containing glycogroups which are PNGase F-sensitive b ut Endo H-resistant. The recombinant VHv1.1 protein bound to hemocytes in vitro and in vivo and was endocytosed in a manner similar to the n ative protein produced in CsPDV-infected larvae. (C) 1997 Elsevier Sci ence Ltd.