Structural and immunological characterization of human cytomegalovirus gp55-116 (gB) expressed in insect cells

The gene encoding the major envelope glycoprotein complex, gp55-116 (gB), of human cytomegalovirus (HCMV) was expressed at high levels in insect cells utilizing a recombinant baculovirus. The mature intracellular form of the insect-derived gp55-116 was a protein of Mr 150K which contained approximately 50K of N-linked oligosaccharides. The oligosaccharide linkages were almost exclusively endoglycosidase H-sensitive. The 150K protein was processed, presumably by proteolytic cleavage, to yield at least one of the previously defined cleavage products of the gp55-116. This processing step was significantly less efficient in insect cells than the analogous step in mammalian cells. Finally, the insect-derived gp55-116 was highly immunogenic in experimental animals and readily recognized by antibodies contained within HCMV-immune human serum, suggesting that this recombinant protein warrants further study as a potential HCMV subunit vaccine candidate.