[Demonstration of Rubella-specific IgG and IgM antibody (sub) classes using the enzyme immunoassay (EIA)]

The sensitivity of three different enzyme-linked immunosorbent assays (ELISAs: Enzygnost-Rubella/Behring Co., Rubazyme (M)/Abbott Co., Rubelisa M/M.A.B.) was examined for detection of rubella-specific IgM and IgG antibodies. The screening of the sera of 20 s.c. vaccinated persons (rubella strain Cendehill) using these diagnostic systems revealed that the ELISAs are capable to detect the rubella IgG antibodies reliably. Additional haemagglutination inhibition (HI), and single radial haemolysis (SRH) tests confirmed this fact. Antibody kinetics seen in Enzygnost-Rubella are similar to those determined by HI. In contrast, it was found that the Rubazyme test is able to detect largely late IgG antibodies in agreement with the data obtained by SRH, which may be helpful to exclude a rubella reinfection. A result negative in Rubazyme, but positive in HI should indicate a positive rubella IgM test. For the determination of subclass-specific IgG antibodies the sandwich assay was extended to a 4-phases-test, using specific antibodies to IgG1-IgG4. After acute rubella infection or vaccination the antibodies of the IgG3 subclass appear before the other. The rubella antibodies in the IgG3 exceed its quantitative distribution in the total IgG (about 7.5%). The determination of IgM-specific rubella antibodies with the Enzygnost-Rubella and Rubazyme M systems proved also to be rather sensitive and reliable. No interference was seen from rheumatoid factor activity, IgG competition and heterologous IgM. In contrast, the Rubelisa M system should be improved in evaluation procedures. However, since all systems showed also differences to HI using IgM fractions, it seems to be advisable to apply an additional rubella IgM test beside ELISA in critical cases.