An anti-human immunoglobulin M monoclonal antibody for detection of antibodies to Toxoplasma gondii

Generation of a novel high-affinity monoclonal antibody with conformational recognition epitope on human IgM

As IgM is the first isotype of antibody which appears in blood after initial exposure to a foreign antigen in the pattern of primary response, detection, and quantification of this molecule in blood seems invaluable. To approach these goals, generation, and characterization of a highly specific mAb (monoclonal antibody) against human IgM were investigated. Human IgM immunoglobulins were used to immunize Balb/c mice. Spleen cells taken from the immunized animals were fused with SP2/O myeloma cells using PEG (polyethylene glycol, MW 1450) as fusogen. The hybridomas were cultured in HAT containing medium and supernatants from the growing hybrids were screened by enzyme-linked immunosorbent assay (ELISA) using plates coated with pure human IgM and the positive wells were then cloned at limiting dilutions. The best clone designated as MAN-1, was injected intraperitoneally to some Pristane-injected mice. Anti-IgM mAb was purified from the animals' ascitic fluid by protein-G sepharose followed by DEAE-cellulose ion exchange chromatography. MAN-1 interacted with human IgM with a very high specificity and affinity. The purity of the sample was tested by SDS-PAGE and the affinity constant was measured (K(a) = 3.5 x 10(9)M(-1). Immunoblotting and competitive ELISA were done and the results showed that the harvested antibody recognizes a conformational epitope on the mu chain of human IgM and there was no cross-reactivity with other subclasses of immunoglobulins. Furthermore, isotyping test was done and the results showed the subclass of the obtained mAb which was IgG(1)kappa.

Comparison of six commercial enzyme linked immunosorbent assays for detecting IgM antibodies against Toxoplasma gondii

To evaluate the usefulness of different commercial enzyme linked immunosorbent assays (ELISAs) for the detection of IgM antibodies against Toxoplasma gondii the results of six of these assays for a panel of 81 sera were compared. The following tests were selected: Toxoplasma gondii IgM ELISA (Clark Laboratories), Toxoplasma IgM EIA (Labsystems), Toxo-M EIA (Abbott), Toxonostika M (Organon), Toxo M Enzyme Immunoassay (Hybritech) and Platelia Toxo IgM (Diagnostics Pasteur). An antibody capture ELISA developed at our laboratory was used as the reference test. An IgM immunoblotting assay was also performed. Four (Toxoplasma IgM EIA, Tox-M EIA, Toxonostika M, and Platelia Toxo IgM) of the commercial IgM ELISAs gave a high sensitivity and a high specificity. Toxo-M EIA, Toxonostika M, Toxoplasma IgM EIA and the Toxo M Enzyme Immunoassay were too insensitive, and the Toxoplasma gondii IgM ELISA was both insensitive and unspecific. No remarkable differences were observed between the results of indirect or antibody capture ELISAs, and between the results of ELISAs performed with polyclonal or monoclonal antibodies.

Comparison of different serotests for specific Toxoplasma IgM-antibodies (ISAGA, SPIHA, IFAT) and detection of circulating antigen in two cases of laboratory acquired Toxoplasma infection

Two symptomatic Toxoplasma infections of laboratory personnel have been serologically followed up for 5.5 and 10 months, respectively. Results obtained by commonly used test systems (indirect fluorescent antibody tests for IgG and IgM antibodies, complement fixation test) were compared with those of two recently developed and improved tests for IgM detection (immunosorbent agglutination assay [ISAGA] and solid-phase indirect haemadsorption assay [SPIHA] as well as with those of a test designed for the detection of circulating antigen (cag-ELISA).

Use of monoclonal antibodies in an ELISA to detect IgM class antibodies specific for Toxoplasma gondii

Two monoclonal antibodies CH6 and C1E3 were used in an antibody class capture assay for the detection of IgM antibodies specific for Toxoplasma gondii. CH6 was used on the solid phase to capture human IgM. After a Toxoplasma gondii antigen had been added, specifically bound material was detected using C1E3 coupled to horseradish peroxidase. The assay was compared with an established system using polyclonal antisera at both the capture and antigen detection stages. A good correlation was found, with 97.3% (125 of 128) of sera giving the same classification in both assays. Three sera were positive only in the polyclonal system. No false positive results were found when 118 negative sera were examined. The two monoclonal antibodies provide a viable alternative to the use of polyclonal sera at the capture and antigen detection stages in the antibody class capture assay for the measurement of specific IgM against T gondii.