Production and characterization of antisera specific for chlorinated biphenyl species: initiation of a radioimmunoassay for Aroclors

Monoclonal antibodies for dioxin: antibody characterization and assay development

A set of 5 anti-dioxin monoclonal antibodies (mAbs), named DD-1, DD-3, DD-4, DD-5 and DD-6, have been isolated. In order to evaluate the ability of these mAbs to recognize various kinds of polychlorinated dibenzodioxins and dibenzofurans, a competition enzyme-linked immunosorbtion assay (ELISA) was developed. All 5 antibodies recognize tetrachloro- and pentachloro-dibenzodioxins and -dibenzofurans. They fail to bind either non-chlorinated, mono-, hexa-, or octa-chlorinated dibenzodioxins, nor do they recognize non-chlorinated, octachloro- or 1,2,3,4,8,9-hexachloro-dibenzofurans. Chlorine substitution on both rings appears necessary for antibody recognition. In the course of our experiments, 3 of the mAbs did not recognize any of the polychlorinated biphenyls (PCBs) tested, while 2 mAbs (DD-1 and DD-6) weakly recognized the 3,3',4,4'-tetrachloro congener. DD-4 and DD-5 are the most specific of the antibodies for the dibenzodioxin and dibenzofuran structure. They do not recognize any of a panel of chlorinated phenols, benzenes, or pesticides. Significantly, these antibodies do not react with PCBs, pentachlorophenol, 2,4-dichlorophenoxyacetic acid, trichlorophenol, or 2,4,5-trichlorophenoxyacetic acid (the latter is weakly recognized by DD-6), any or all of which might be present in large quantities in some dioxin-contaminated samples. Finally, the competition ELISA is able to easily detect 0.5 ng of the most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin. It should thus prove useful as an environmental screen for contamination.

Monoclonal antibodies to chlorinated dibenzo-p-dioxins

A thyroglobulin conjugate of dioxin (thyroglobulin-2 adipamide, 3,7,8-trichlorodibenzo-p-dioxin) (TG-TCDD) was used to immunize BALB/c mice. Hybridomas were produced by cell fusion between immune spleen cells and mouse myelomas SP2/0, P3, or NS1. To screen the thousands of resultant cultures for production of monoclonal antibodies (MoAb), a rapid, solid-phase radioimmunoassay for antibody to dioxins was developed. This procedure involved attaching bovine serum albumin coupled with trichlorodibenzo-p-dioxin (BSA-TCDD) to polystyrene plates to be used as a solid-phase target antigen for reaction with MoAb. Fourteen hybridomas were identified that produced MoAb reacting with BSa-TCDD but not with BSA alone. Antibodies were tested for binding to BSA-aniline to eliminate those with limited binding specificity. Initial studies indicated that most MoAbs bound BSA-aniline as well as BSA-TCDD. More detailed analyses indicated that while most MoAbs showed some reaction with BSA-aniline, two showed preferential binding to BSA-TCDD of more than 200-fold whereas rabbit antisera demonstrated only a 5-fold discrimination. MoAb 391-1B was purified from mouse ascites fluid and after radioiodination, was tested for direct binding to BSA-TCDD or BSA-aniline. 125I-MoAb 391-1B showed no significant binding to BSA-aniline while demonstrating high binding to BSA-TCDD (Ka = 4.5 X 10(8) liters/mol).

Radioimmunoassay of PCBs in milk and blood

A radioimmunoassay was developed capable of determining Aroclor 1260 in milk at levels of from 20 to 80 ppb and in blood from 2 to 16 ppb. The values obtained by radioimmunoassay correlate well with those determined by gas-liquid chromatography (r2 = 0.96 for milk and 0.99 for blood) but were lower. Antiserum was produced in rabbits and was specific for 2,2',4,4',5,5'-hexachlorobiphenyl. It cross-reacted with congeners and isomers in Aroclor 1254 and 1260 to the extent that a 20% decrease in binding was observed with 0.1 ng of either mixture. The method requires preliminary cleanup of the extract on alumina and utilizes 25% dimethyl sulfoxide in the assay medium to promote solubilization of the substrates.