Different Affinity of Monoclonal Antibodies for Conserved Neutralizing Epitopes on Two Strains of Rubella Virus

Abstract

There is, apparently, only one serological type of rubella virus (RV) in the population, although several isolates exist with different characteristics. Some authors failed to detect significant differences among RV strains by neutralization, hemagglutination inhibition, and enzyme immunoassay using polyclonal and monoclonal antibodies, but differences 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 strains of RV, we studied the affinity constant of two monoclonal antibodies (MAbs) for two conserved neutralizing epitopes. Wild-type Cordoba (regional isolation of a post-natal infection) and RA 27/3 (vaccine) strains of RV were tested. H3 and H14 MAbs were generated against wild-type Cordoba strain. They defined two epitopes with conserved neutralizing and hemagglutinating activity on both strains. The affinity of the MAbs (expressed as the affinity constant), was greater for Cordoba strain than for RA 27/3. Analyzing the results obtained, we conclude that the neutralizing epitopes defined by our MAbs on E1 glycoprotein are conserved in the two strains, but react with significative different affinities. This could be a way to characterize antigenically different viral strains of the same serotype.

Evaluation of Antibodies against a Rubella Virus Neutralizing Domain for Determination of Immune Status

“…Monoclonal antibodies (MAbs) were used to define the neutralizing domains on the E1 glycoprotein whose amino acid sequences were determined by overlapping synthetic peptides (9,11,12,14,21,22,24). One of these domains was defined by three independent MAbs that recognized the same sequence, represented by the synthetic peptide SP15 (E1 amino acids 208 to 239) (4,25). Moreover, SP15 was shown to induce polyvalent antibodies with neutralizing and hemagglutination inhibition activity in mice and rabbits.…”

Presence of a neutralizing domain in isolates of rubella virus in Cordoba, Argentina

“…The sequence of SP15 includes amino acids E1 208-239 . The set of MAbs were produced by intraperitoneally injecting 2-to 4-week-old male BALB/c mice with 150 g of purified Cordoba strain of RV (10 6 PFU/ 0.2 ml) in Freund's complete adjuvant on days 0, 10, and 20 (2,21). The ascitic fluids were collected after 2 to 3 weeks and clarified by low-speed centrifugation.…”