Rubella virus (RV)-specific
immunoglobulin G antibodies were studied by
enzyme-linked
immunosorbent assay (ELISA) techniques in sera from RV (RA 27/3)-vaccinated individuals, patients experiencing natural RV
infection,
congenital rubella syndrome patients, and individuals failing to respond to repeated RV immunization. Results obtained by using whole-RV ELISAs (
detergent-solubilized M33 strain or intact Gilchrist strain) and hemagglutination inhibition (HAI) and neutralization (NT) assays were compared with results obtained with the same sera by using ELISAs employing a synthetic
peptide, BCH-178, representing a putative neutralization domain on the RV E1
protein. Murine RV E1-specific
monoclonal antibodies with HAI and NT activities exhibited strong reactivity in ELISAs with BCH-178
peptide. In sera from RA 27/3-vaccinated individuals collected at 0 (prevaccine), 1, 2, 3, 4, 5, 6, 12, and 24 to 52 weeks postvaccine, the development of E1-peptide-reactive
antibodies closely paralleled increases in RV-specific
antibodies measured by whole-RV ELISAs and HAI and NT assays. Similarly, sequential serum samples obtained from patients during acute and convalescent phases of natural RV
infection showed a coordinate increase in RV-specific
antibodies as measured by whole-RV and
peptide ELISAs. Conversely,
congenital rubella syndrome patient sera, although exhibiting high levels of antibody in whole-RV ELISAs, had little or no antibody directed to the neutralization domain peptide. Sera from patients failing to respond to repeated RV immunization contained very low levels of RV-specific antibody in all ELISAs. Our results that the sequence represented by BCH-178
peptide may be a previously unidentified neutralization
epitope for human
antibodies on the RV E1
protein and may prove useful in determining effective RV immunity.