Recently, Vitetta was using ricin poison in her search for a cancer drug. "We were attaching a part of the ricin toxin to antibodies directed against tumors," she says. "You could say the antibody was the delivery system for a warhead and the warhead was the toxin." There were side effects to the treatment, but Vitetta and colleagues were able to eliminate them through genetic engineering of the toxin. Then it occurred to them: Because they were able to eliminate the side effect, they could probably eliminate the toxicity as well, thus producing a vaccine for the poison.