Description of a technique for the determination of the concentration and quality of rubella virus antibody molecules and experience with testing sera from humans with recent and past rubella infection.

The method of equilibrium filtration described by Fazekas and Webster (7, 8) for the determination of the concentration (A) and quality (K) of influenza virus antibody molecules was modified in order to permit such determinations to be made for rubella virus hemagglutination inhibiting (HI) antibodies. The technique was used for determining the A and K values of humans with recent and past rubella infection. Sera from patients collected within 59 days after onset of rubella rash were found to have larger K values than found for sera collected therafter or from persons with past rubella infection. The difference in K values was found not to depend on the levels of IgM rubella antibodies. Therefore, sera from persons with recent and past rubella infection can be distinguished by use of this technique independently from the relative concentrations of rubella IgM and IgG HI antibodies.