In an attempt to define diagnostic criteria that may help to distinguish the
congenital rubella syndrome (CRS) from subclinical intrauterine rubella virus (RV)
infection, maternal and fetal serum samples were analyzed using (1)
enzyme immunoassay employing RV synthetic
peptides as
antigen, (2)
IgG avidity 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 levels of E2-specific
antibodies and deficient
IgG recognizing the major
neutralizing antibody-inducing
epitope on the E1
protein (SP15). Antibody responses were normal in mothers with presumed RV
reinfection as well as in asymptomatic 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 high avidity
IgG, conformational E2-specific as well as SP15-reactive
antibodies may serve as a potential predictor for a benign outcome of intrauterine RV
infections.