Detection of residual toxin in tissues of ricin-poisoned mice by sandwich enzyme-linked immunosorbent assay and immunoprecipitation

This work aimed to evaluate a method to detect the residual ricin in animal tissues. Immunoprecipitation and sandwich enzyme-linked immunosorbent assay (ELISA) were used to detect ricin in the tissues of intoxicated mice. The monoclonal antibodies (Mabs) 4C13 and 3D74 were used to assay the whole ricin molecules via sandwich ELISA. Mab 4C13 was conjugated with Sepharose 4B to capture ricin or ricin A chain by immunoprecipitation. Mice injected intravenously with ricin at the dosage of 5 μg/mouse were killed at different time points after intoxication. The serum, liver, kidney, lung, and intestine were harvested. High levels of ricin were found in serum and liver samples at each poisoning time point by sandwich ELISA, suggesting the possibility of determining ricin intoxication by detecting residual ricin in the serum. However, this method turned out to be ineffective for examining ricin in the kidney, lung, and intestine of poisoned mice. Although the same tissue samples of intoxicated mice were analyzed by immunoprecipitation, positive bands were found. This indicated that some components in the kidney, lung, and intestine could bind with ricin and interfere in its binding activity with the coated antibody. Immunoprecipitation could be used to measure the existence of ricin in these samples.