Abstract
By application of IgG 1, IgG 2-, and IgM-specific conjugates in an enzyme-linked immunosorbent assay (ELISA), dominance of IgG 1 in natural Q-fever infections of cattle could be demonstrated. In contrast, vaccination with an inactivated Q-fever vaccine predominantly induced IgG 2 antibodies. Complement fixing activity was detected in positive sera (inactivated at 56°C) in the IgG 1 fraction only. Therefore, with serum samples containing exclusively IgM (10%), or IgG 2 (4%), a serodiagnosis could be achieved only by ELISA. Furthermore, it could be shown that IgG 2 and IgM may suppress fixation of complement by IgG 1 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, IgG 1, and IgG 2-specific conjugates were used. In comparison to sera, only 73 % of corresponding milk samples were positive in the IgG 1-ELISA. However, for seroepidemiological purposes testing of bulk milk samples by ELISA may be feasible.
Published Version
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