Detoxification of Snake Venom Using Ionizing Radiation

Abstract

It is generally recognized that energy absorbed from ionizing radiation (gamma rays) can inactivate biological material in two ways. A direct effect occurs when the primary event, i. e., ionization, is produced in the molecule itself. This is the case when a compound is irradiated in dry state. When a compound is irradiated in a solution, the indirect effect joins the direct(9). Since water is the most abundant constituent of biological material, it is important to consider the species produced by excitation and ionization of water itself, and the reaction of these species with the target molecules of biological importance. This indirect effect results from the reactions among the studied molecules and the products of radiation interaction with water or other solvents. Highly reactive compounds, the so-called free radicals, which are formed undergo many reactions among themselves, with the dissolved gas, and with other molecules in the solution. With water, the excitation is less important than ionization which is followed within picoseconds by the formation of free hydroxyl radicals and hydrated electrons(2,4,16). Alexander & Hamilton(1) showed that irradiation of proteins has revealed damage to aminoacid side chains, production of new groups, splitting of peptide bonds and formation of intramolecular and intermolecular cross-links. With these results, it would be possible to use of ionizing radiation to change those protein molecules in order to improve some of their properties according to the necessity. On the other hand, it is recognized that venoms in general are poorly immunogenic, yet fairly toxic(15). This causes problems because serotherapy is the treatment of choice in snakebite envenomations, and horse antivenom availability is dependent upon immunogenicity

Immunological assessment of mice hyperimmunized with native and Cobalt-60-irradiated Bothrops venoms

“…This agrees with the findings of other authors (7,12,21,(31)(32)(33)(34)(35)(36)(37)(38)42), which assured that ionizing radiation has the property to attenuate venoms toxicity without altering immunological properties.…”

“…It is known that antigens, as they enter the organism, suffer an oxidation process by the defensive cells to facilitate phagocytosis (38). In irradiated samples, macrophages already find these molecules oxidized, and therefore, they eliminate to abolish paralysis and miotoxicity caused by the venom.…”

“…The principal physical agents are: x-ray radiation (19), ultraviolet radiation (46), heat (15), and gamma radiation (25). The latter, according to previous works (1,7,9,12,14,17,21,(31)(32)(33)(34)(35)(36)(37)(38)(41)(42)(43), has proved to be an excellent tool of detoxification, since it is able to reduce toxicity without altering immunogenicity. In addition, this radiation does not add any new substance to the venom.…”

Effect of gamma irradiation on the behavioral properties of crotoxin

“…Since the useful life of immunized horses is impaired by chronic venom toxic-ity, it became necessary to develop techniques that would improve antiserum production. For this purpose, biochemical, immunological and radiobiological studies have been carried out with crotalic venom and crotoxin submitted to gamma radiation (5)(6)(7). These studies have shown that irradiated crotoxin is about 2-fold less toxic than crotoxin, but its immunogenicity is preserved (8).…”

Comparação entre a nefrotoxicidade da crotoxina nativa e a irradiada com raios gama de Co-60 em camundongos

“…Atravessa qualquer tipo de matéria e remove elétrons da camada eletrônica periférica dos átomos, que resulta na formação de cátions e ânions. A radiação gama pode ainda excitar os elétrons das camadas externas atômicas, e estes absorvem energia suficiente para atingir seu estado energético mais alto, emitindo energia sob a forma de luz visível ou ultravioleta (ROGERO; NASCIMENTO, 1995 Sendo assim, as mudanças no material biológico, podem ocorrer por efeito direto da radiação, onde a ionização é produzida na própria molécula. Ou pode ocorrer efeito indireto, em que as alterações nas moléculas do material são induzidas pelos produtos formados a partir da radiólise da água, quando este material é irradiado em solução.…”