EXPRESSION OF EQUINE HERPESVIRUS TYPE-1 GLYCOPROTEIN GP14 IN ESCHERICHIA-COLI AND IN INSECT CELLS - A COMPARATIVE-STUDY ON PROTEIN PROCESSING AND HUMORAL IMMUNE-RESPONSES

The extracellular portion (amino acids 1 to 844) of the equine herpesv irus type 1 (EHV-1) glycoprotein gp14, the homologue of gB of herpes s implex virus, was expressed in Escherichia coli and in insect cells us ing a recombinant baculovirus. Immunoblot analysis revealed that the r ecombinant E. coli expressed a fusion protein of M(r) 135K which was c omposed of the truncated gp14 and the maltose-binding protein (MBP) pr ovided by the vector and a 90K protein tacking the MBP moiety. Both pr oteins were sequestered within the cells in form of inclusion bodies. Infection of insect cells with the recombinant baculovirus resulted in the production of a 115K to 118K glycoprotein which was cleaved intra cellularly into two subunits of M(r) 55K and 63K to 65K. The cleaved s ubunits were secreted into the cell culture supernatant and formed dis ulphide-linked dimers of M(r) 120K to 122K. The recombinant proteins p roduced in E. coli and in insect cells elicited EHV-1-specific antibod ies in goats as demonstrated by Western blot analysis. The gp14 expres sed in insect cells induced antibodies with virus-neutralizing activit y. In contrast, the truncated gp14 expressed by E. coli failed to elic it neutralizing antibodies. The results suggest that posttranslational modification of the EHV-1 gp14 may be important for the expression of epitopes necessary for the induction of neutralizing antibodies.