Solid-phase radioimmunoassays for quantitative antibody determination of bacterial exotoxins. Measurement of Clostridium perfringens type D epsilon antitoxin.

Two reversed solid-phase radioimmunoassays have been developed for quantitative determination of antibodies against Clostridium perfringens type D epsilon toxin. 125I labelled prototoxin was used in the bromoacetyl cellulose-bound antibody method and in the antibody coated tube method. The procedures are based on the competition for 125I labelled prototoxin between the insoluble antibodies and the antibodies present in the unknown sample. The radioactivity bound to solid-phase is in inverse ratio to quantity of measured antibodies. The antibody values which can be detected are in the range of 0.004 IU/ml of investigated serum. The methods allow the rapid and inexpensive screening of large groups of vaccinated sheep, and are very suitable for measuring small amounts of Cl. perfringens D epsilon antibodies with a small experimental error.