A Monoclonal Antibody Assay for Detecting Cyclodiene Insecticides
Researchers at the University of California (UC) have produced a mouse hybridoma cell line, which secretes monoclonal antibodies directed against the most common and persistent polychlorinated cyclodiene insecticides. The monoclonal antibodies are the basis of a competition enzyme-linked immunosorbent assay (cELISA), which the UC researchers have developed for use as a sensitive and straight-forward system for detecting the contaminants in foods, soils, and human populations.
Polychlorinated cyclodienes are a class of chemical compounds employed as pesticides. The compounds, chlordane in particular, receive extensive use in most parts of the world, but have been restricted or banned in the U.S. since the mid-1970s. The compounds persist in this country as widely-distributed environmental contaminants, and are present as residues on many imported foodstuffs.
Considerable concern exists about these compounds. Cyclodiene pesticides are highly toxic to fish, birds, and small mammals, and they are considered potentially oncogenic by the U.S. E.P.A.. Furthermore, as lipophilic molecules, they have a strong tendency to accumulate in milk and in the fatty tissues of both animals and human beings. Consequently, both the U.S.D.A. and the E.P.A. have established in the U.S. limits on the levels of these contaminants which are permitted in foods and the environment. Similar recommendations have been made by the World Health Organization world-wide.
No detection system has existed, however, with which to conduct systematic testing. Assessment of total organic chlorine content is one indicator, but is non-specific. Techniques of analytical chemistry, on the other hand, while suitable in principle, have been found too costly and cumbersome for the task. Gas chromatography coupled with electron capture (GC/EC) is the single chemical analytical detection system viable, and it requires elaborate steps when applied to typical foodstuffs and environmental samples. Lengthy, costly and not portable in the field, the technique requires an equipped, central laboratory and an highly trained staff. Monoclonal antibody-based detection systems, in contrast, are now well known for both their sensitivity and their straight-forwardness. Every federal agency involved in health in some aspect has assigned funds for development of these assays, and portable test kits are in common use by the untrained public, in the form of the modern home pregnancy test. The trace insecticide test developed by UC researchers is a conventional cELISA, based on a monoclonal antibodies specific to polycholorinated norbornenes and to mono- and dicyclopentadienes. The assay detects quantitatively the presence of the common insecticides heptachlor, chlordane, aldrin, dieldrin, endrin, endosulfan, toxaphene, and multiple isomers of BHC. The assay test exhibits sufficient sensitivity to measure concentrations of these compounds at levels below the federally set limits. In samples of spiked beef fat, fish, and heavy cream, the cELISA could accurately quantify contaminant concentrations of 20-50 ppb and above. In tests characterizing the binding affinity of the monoclonal antibodies, 50% inhibition occurred at roughly 1 ng/well for endrin, aldrin, chlordane, heptachlor, and heptachlor epoxide (the metabolized form of heptachlor as it commonly accumulates in tissues). The cELISAs are suited for use in kit format by field inspectors. An individual with limited training can readily analyze one hundred samples at a time.
In the scientific community, interest exists in cyclodienes because of their ability to disrupt central nervous system function in human beings, and because of their established association with anemia and leukemia. The monoclonal antibodies secreted by the UC-developed cell line would readily provide the basis for an affinity column purification system. Such a system would be extremely valuable for any investigations of the specific effects of cyclodienes in living organisms.
US 5,334,528 [MORE INFO
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