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 virus (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 missing the first 30 amino acids that comprise the signal peptide of the protein. The diagnostic value of these antigens was examined by two methods: (1) immunoblot assay based on MBP-gG1 and MBP-gG2 fusion proteins present in crude E. coli cell extracts and (2) enzyme-linked immunosorbent assay (ELISA) of immunoaffinity-purified recombinant MBP-gG1 and 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 positive for mixed antibody to HSV-1/HSV-2), 27 were reactive to the MBP-gG1 recombinant protein both in ELISA and in immunoblotting. In addition, of 20 serum samples known to have antibody to HSV-2 (2 specimens positive for HSV-2 alone and 18 samples positive for mixed antibody to HSV-1/HSV-2), 15 were found to be reactive to the MBP-gG2 recombinant protein by ELISA and 16 by immunoblotting. None of the 13 HSV-antibody-negative serum samples showed reactivity to the MBP-gG1 or MBP-gG2 antigens by either assay. Moreover, none of the serum samples known to have antibody to HSV-1 alone showed reactivity to the MBP-gG2 recombinant antigen. This study verified the potential application of the E. coli-expressed recombinant gG1 and gG2 proteins as diagnostic antigens and demonstrated the MBP fusion system to be a simple and effective method of producing adequate amounts of low-cost, easily purified gG antigens.