A RADIOIMMUNO-PRECIPITATION ASSAY FOR ANTIBODIES TO BOTULINUM-A

We quantified antibodies to botulinum A (anti-BTx) by immunoprecipitat ion of I-125-BTX. We tested seven bioassay-positive sera and 68 coded samples, including 18 from patients who had ceased to respond to BTx t reatment. Compared with values from healthy control subjects and 42 ne urologic control subjects, all bioassay-positive sera were positive (r ange, 258 to 2,809 pM) and 49 of 50 patients who continued to respond to BTx were negative (<130 pM). This simple, specific, sensitive, and quantitative assay should prove helpful in the investigation of BTx re sistance.