Fine specificity and neutralizing activity of human serum antibodies directed to the major antigenic region on gp 116 of human cytomegalovirus

The human antibody response to the conserved neutralization-related site on the gp 116 of human cytomegalovirus (HCMV) was investigated in healthy blood donors by the use of synthetic peptides. Anti-HCMV positive sera investigated in ELISA gave a reactivity of 48-56% with the peptide T7-13 (amino acids (aa) 67-86). Though epitope mapping revealed several individual fine specificities within this region, the average reactivity pattern was similar to that of the human monoclonal antibody (MAb) ITC88, the binding of which has been localized to aa 69-80. By the use of superparamagnetic Dynabeads coated with the peptide T7-13, serum antibodies were affinity isolated and the neutralizing activity was investigated. A clear reduction in infectivity was seen only with antibodies from one out of four sera and this serum exhibited a fine specificity nearly identical to that of MAb ITC88. A complete adsorption of antibodies to this site was not achieved, yet the results imply that antibodies against this region do not constitute a major part of the HCMV-neutralizing activity in human serum. The potent complement-independent neutralizing activity of antibodies directed to this site nevertheless suggests that it will contribute beneficially to a subunit vaccine