Development of monoclonal antibodies specific for Ricinus agglutinins

Ricin is a highly toxic, dichain ribosome-inactivating protein present in the seeds of Ricinus communis (castor), grown principally as a source of high quality industrial lubricant and as an ornamental. Because of its presence in industrial byproducts and its documented use for intentional poisoning, there is a need for analytical methodology to quantify ricin in both castor extracts and food matrices. We developed a panel of monoclonal antibodies to ricin, with most having strong cross-reactivity with RCA-1, a homologous but less toxic castor agglutinin. Some of the IgM-producing hybridomas appeared to produce a second, IgG isotype and were further analysed by fluorescence-activated cell sorting. The antibodies were effective in various ELISA formats, many with IC50's in the range of 0.1-10 ng/mL and minimal matrix effects in skim milk. Assay specificity can be adjusted for analytical needs by varying the combination of antibodies in a sandwich ELISA format.