[Enzyme-linked immunosorbent assay (ELISA) for the demonstration of IgG1, IgG2 and IgM antibodies in bovine Q fever infection].

By application of IgG1-, IgG2-, and IgM-specific conjugates in an enzyme-linked immunosorbent assay (ELISA), dominance of IgG1 in natural Q-fever infections of cattle could be demonstrated. In contrast, vaccination with an inactivated Q-fever vaccine predominantly induced IgG2 antibodies. Complement fixing activity was detected in positive sera (inactivated at 56 degrees C) in the IgG1 fraction only. Therefore, with serum samples containing exclusively IgM (10%), or IgG2 (4%), a serodiagnosis could be achieved only by ELISA. Furthermore, it could be shown that IgG2 and IgM may suppress fixation of complement by IgG1 antibodies, thus resulting in incomplete inhibition of hemolysis and even reduction of CF-titers. So, sera with low CF-titers may give incorrect negative results in the CF-test. Applying the ELISA with L-chain-specific conjugates, such problems could be avoided. For evaluation of the early and later stages of infection or the status of vaccination, IgM, IgG1-, and IgG2-specific conjugates were used. In comparison to sera, only 73% of corresponding milk samples were positive in the IgG1-ELISA. However, for seroepidemiological purposes testing of bulk milk samples by ELISA may be feasible.