[Enzyme-linked immunosorbent assay (ELISA) for IgG- and IgM antibodies in chlamydial infections of humans].

The development and evaluation of an indirect ELISA for IgG and IgM antibodies in human sera against the genus-specific chlamydial antigen is described. Application of commercial anti-immunoglobulins for production of conjugates usually resulted in direct conjugate/antigen reactions. Therefore, all immunoreagents had to be prepared by the authors. Using anti-immunoglobulins purified by affinity chromatography for the production of anti-human IgG(H + L)-peroxidase conjugates, these conjugates showed high specific activity and could be diluted 1/10,000 for the test, whereby direct reactions with antigens were negligible (12 +/- 12 ELISA units). Results with the mu-chain-specific IgM ELISA could be verified additionally by rheumatoid factor analysis and gel-chromatographic investigations. Reactions with sodium deoxycholate extracted antigen from cells not infected with chlamydiae ("negative antigen") were observed with sera from persons working with cell cultures. In comparison with microimmunofluorescence (MIF) test and radioimmunoassay (RIA), the ELISA was the most sensitive method. However, for differentiation of urogenital infections associated with chlamydiae, the type-specific MIF test was superior to the genus-specific ELISA. In comparison to persons with chlamydia-associated prostatitis, the high percentage of IgM-positive reactions in patients with nongonococcal urethritis (10% and 56%, respectively) pointed to a predominant participation of genus-specific IgM antibodies in recent infections. As compared to ELISA values of patients with infections of the urogenital tract (up to 875 ELISA units), in some apparently healthy blood donors significantly higher ELISA values (up to 1400 ELISA units) were recorded. Such reactions may be attributed to systemic infections, e.g. chlamydial pneumonias. The importance to differentiate between IgG and IgM antibodies in such infections is discussed.