ESCHERICHIA-COLI EXPRESSED HERPES-SIMPLEX VIRUS GG1 AND GG2 PROTEINS IN ELISA AND IMMUNOBLOTTING ASSAYS

The type 1 and type 2 glycoprotein G (gG1 and gG2) of herpes simplex v irus (HSV) were expressed in Escherichia coli as fusion proteins with the maltose binding protein (MBP) using the pMAL-c2 expression vector. The MBP-gG1 fusion protein contains all but the four amino acids from the amino-terminus of gG1, whereas the MBP-gG2 fusion protein was mis sing the first 30 amino acids that comprise the signal peptide of the protein. The diagnostic value of these antigens was examined by tao me thods: (1) immunoblot assay based on MBP-gG1 and MBP-gG2 fusion protei ns present in crude E. coli cell extracts and (2) enzyme-linked immuno sorbent assay (ELISA) of immunoaffinity-purified recombinant MBP-gG1 a nd MBP-gG2 fusion proteins. Of 28 serum samples known to have antibody to HSV-1 (10 specimens positive for HSV-1 alone and 18 specimens posi tive for mixed antibody to HSV-1/HSV-2), 27 were reactive to the MBP-g G1 recombinant protein both in ELISA and in immunoblotting. In additio n, of 20 serum samples known to have antibody to HSV-2 (2 specimens po sitive for HSV-2 alone and 18 samples positive for mixed antibody to H SV-1/HSV-2), 15 were found to be reactive to the MBP-gG2 recombinant p rotein by ELISA and 16 by immunoblotting. None of the 13 HSV-antibody- negative serum samples showed reactivity to the MBP-gG1 or MBP-gG2 ant igens by either assay. Moreover, none of the serum samples known to ha ve antibody to HSV-1 alone showed reactivity to the MBP-gG2 recombinan t antigen. This study verified the potential application of the E. col i-expressed recombinant gG1 and gG2 proteins as diagnostic antigens an d demonstrated the MBP fusion system to be a simple and effective meth od of producing adequate amounts of low-cost, easily purified gG antig ens.