Predictive value of serological tests in rubella virus infection during pregnancy

In an attempt to define diagnostic criteria that may help to distinguish th e congenital rubella syndrome (CRS) from subclinical intrauterine rubella v irus (RV) infection, maternal and fetal serum samples were analyzed using ( 1) enzyme immunoassay employing RV synthetic peptides as antigen, (2) IgG a vidity assay, and (3) immunoblot under nonreducing conditions, in addition to hemagglutination inhibition and commercial enzyme immunoassays. Infants born with CRS and their mothers were shown to reveal low or undetectable le vels of E2-specific antibodies and deficient IgG recognizing the major neut ralizing antibody-inducing epitope on the E1 protein (SP15). Antibody respo nses were normal in mothers with presumed RV reinfection as well as in asym ptomatic infants born after maternal primary rubella. The results indicate that the maturation of specific humoral immune responses is obviously less efficient when intrauterine RV infection results in CRS. The detection of h igh avidity IgG, conformational E2-specific as well as SP15-reactive antibo dies may serve as a potential predictor for a benign outcome of intrauterin e RV infections.