A synthetic peptide ELISA for the screening of rubella virus neutralizing antibodies in order to ascertain immunity

One hundred and fifty-one human sera from patients exposed to rubella virus (RV) and shown to be negative for IgM antibodies were tested for total RV-IgG, hemagglutination inhibition (HAI) and for virus neutralizing (VN) antibodies using a peptide enzyme-linked immunosorbent assay (ELISA) based on BCH-178, a peptide representing one of several known neutralizing epitopes on RV hemagglutinin (E1). The data showed that, among 39 and 51 sera with HAI and RV-IgG titres of 1/128 and >150 IU/ml, respectively, neutralizing antibody readings using the BCH-178 ELISA were above cut-off values. However, 13% of HAI positive sera (titre greater than or equal to 1/16) and 16% of RV-IgG ELISA positive sera ( greater than or equal to 20 IU/ml) were below the cutoff value of the BCH-178 ELISA. This may explain why several cases of congenital rubella syndrome (CRS) have been observed in spite of positive tines. We suggest that a diagnosis of sufficient immunity against RV infection or reinfection may be safer if an additional test detecting antibodies against VN RV epitopes is positive as well. (C) 2004 Elsevier B.V. All rights reserved.