Stepwise iodination. A general procedure for detoxification of proteins suitable for vaccine development and antiserum production.

By gradual incorporation of stable iodine into toxins and whole venoms it is possible to abolish completely the lesion and lethal properties of the native components. Allergen extracts can be turned anallergic. Physiological proteins with strong biological activity can also be rendered innocuous. Tyrosine and histidine are the reactive groups that incorporate the hapten. Within the same batch of protein, there is a defined ratio hapten/protein to achieve the desired modified properties of the derivative. The iodinating solutions are easily prepared, can be accurately standardized and have unlimited shelf lives. The derivatives are obtained in a short time. The cost of the entire procedure is very low. The method was applied to tityustoxin and whole venom of the scorpion Tityus serrulatus; crotoxin and whole venom of Crotalus durissus terrificus; to five bothropic venoms; to allergenic extracts of Schistosoma mansoni; to cholera and tetanus toxin; and to insulin, kallikrein and tonin. The derivatives obtained were stable, did not show any reversion to toxicity, generated antibodies against the native antigens and gave active protection when injected into animals. No local or systemic side effects were observed, even after prolonged use. The injections were also apparently painless. By extensive haptenization self proteins can be rendered non-self, able to generate antibodies against both the derivative and the native unmodified protein, and iodination was very convenient for this purpose. A new schedule for immunization, only feasible with completely toxoided venoms is presented. It is based on a clonal expansion induced by a small dose, followed by an exponential saturation dose of the same toxoid. The attainment of higher levels of antibodies against the native antigen, in the generated sera is unmatched by other procedures.