DIFFERENT AFFINITY OF MONOCLONAL-ANTIBODIES FOR CONSERVED NEUTRALIZING EPITOPES ON 2 STRAINS OF RUBELLA-VIRUS

There is, apparently, only one serological type of rubella virus (RV) in the population, although several isolates exist with different char acteristics. Some authors failed to detect significant differences amo ng RV strains by neutralization, hemagglutination inhibition, and enzy me immunoassay using polyclonal and monoclonal antibodies, but differe nces in growth, plaque morphology, and temperature sensitivity between vaccine and wild-type strains were shown by Chantler et al. (3) With the purpose of analyzing the possible differences among several strain s of RV, we studied the affinity constant of two monoclonal antibodies (MAbs) for two conserved neutralizing epitopes. Wild-type Cordoba (re gional isolation of a post-natal infection) and RA 27/3 (vaccine) stra ins of RV were tested. H3 and H14 MAbs were generated against wild-typ e Cordoba strain. They defined two epitopes with conserved neutralizin g and hemagglutinating activity on both Strains. The affinity of the M Abs (expressed as the affinity constant), was greater for Cordoba stra in than for RA 27/3. Analyzing the results obtained, we conclude that the neutralizing epitopes defined by our MAbs on E-1 glycoprotein are conserved in the two strains, but react with significative different a ffinities. This could be a way to characterize antigenically different viral strains of the same serotype.