A competitive enzyme-linked immunosorbent assay was used to test for human antibodies to antigenic sites on herpes simplex virus (HSV) glycoproteins C and D, which are recognized by mouse monoclonal antibodies. One of these antibodies (3-G11) reacts with a glycoprotein C complex (molecular weight, 80,000 and 120,000)that is specific for HSV type 1, while the other three antibodies (6-A6, 6-E12, and 6-H11) react with proteins that are specific for HSV type 2 and that have molecular weights of 140,000, 55,000, and 38,000, respectively. G., Kirschner, M. in Intervirology 32:351–360, 1991; Eis-Hübinger et al. Furthermore, we uncovered that MAb-B2 recognizes the ORF72 of KHV as revealed by liquid chromatography–tandem mass spectrometry and Western blot assays. The positive predictive value (using the resolved sample results) for Herpchek, IDEIA HSV and SureCell HSV was 100 %, 97.8 % and 78.1 % respectively, and the negative predictive value 88.7 %, 83.6 % and 58.8 % respectively. The antibody was found to recognise a discontinuous epitope comprised of the HSV type 1 glycoprotein B residues 299 to 305 and one or more additional discontinuous regions that can be mimicked by the sequence FEDF.
Identification of the epitope was confirmed by loss of antibody binding to mutated glycoprotein B with replacement of the epitopic key residues, expressed in COS-1 cells. Similarly, MAb 2c was not able to neutralise HSV mutants with altered key residues, and MAb 2c was ineffective in mice inoculated with such mutants. Interestingly, identification and fine-mapping of the discontinuous epitope was not achieved by binding studies with truncated glycoprotein B variants expressed in COS cells but by peptide scanning with synthetic overlapping peptides and peptide key motif analysis. Reactivity of MAb 2c was immensely increased towards a peptide composed of the glycoprotein B residues 299 to 305, a glycine linker, and a C-terminal FEDF motif. If it could be demonstrated that antibodies of the specificity and bioactivity of MAb 2c can be induced by the epitope or a peptide mimicking the epitope, strategies for active immunisation might be conceivable.