Characterization of rubella virus-specific antibody responses by using a new synthetic peptide-based enzyme-linked immunosorbent assay.

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.