Rosalvo Guidolin

Neutralization of crotaline snake venoms from Central and South America by antivenoms produced in Brazil and Costa Rica.

A study was performed on the ability of antivenoms, produced in Brazil and Costa Rica, to neutralize lethal, hemorrhagic and coagulant activities of the venoms of 16 species of Central and South American snakes of the subfamily Crotalinae. Neutralization of lethality was studied by two different methods routinely used in the quality control of antivenoms at Instituto Butantan (IB) and Instituto Clodomiro Picado (ICP). Both antivenoms neutralized the majority of the venoms studied, but the values of effective doses 50% (ED(50)) differed markedly depending on the method used. In general, higher potencies were obtained with the method of ICP, where a challenge dose corresponding to 4 LD(50)s is used, than with the method of IB, where a challenge dose of 5 LD(50)s is employed. All venoms induced hemorrhagic activity in the mouse skin test, which was effectively neutralized by the two antivenoms. All venoms, except those of Porthidium nasutum and Bothriechis lateralis, induced coagulation of human plasma in vitro and both antivenoms were effective in the neutralization of this activity. In conclusion, our results provide evidence of an extensive cross reactivity between these antivenoms and Central and South American crotaline snake venoms.

Esterilização de soros e vacinas por radiação gama de cobalto

Os soros antitetânico, antidifterico e antibotropico-crotalico e, ainda, a vacina difterica-pertussis-tetânica foram submetidos a diferentes intensidades de radiacao gama, com os seguintes intuitos: verificacao da resistencia das atividades especificas destes produtos a acao dos raios gama; avaliacao das possibilidades de utilizacao deste tipo de energia radiante para a esterilizacao de alguns soros hiperimunes heterologos e vacinas, mais comumente utilizados em saude publica. Os resultados obtidos, segundo os parâmetros empregados, mostraram a possibilidade de esterilizacao sem alteracoes das atividades especificas, de ordem biologica ou quimica, dos produtos experimentados.

Characterization of anti-crotalic antibodies

Crotalus durissus terrificus, C. d. collilineatus, C. d. cascavella and C. d. marajoensis are responsible minor but severe snake bites in Brazil. The venoms of these snakes share the presence of crotoxin, a neurotoxin comprising of two associated components, crotapotin and phospholipase A2 (PLA2). Treatment of the victims with specific antiserum is the unique effective therapeutic measure. The ability of anti-Crotalus antisera produced by the routine using crude venom to immunize horses or purified crotoxin and PLA2 as individual immunogens was compared. Antisera obtained from horses immunized with C. durissus terrificus crude venom were able to recognize and neutralize not only the toxins presents in C. durissus terrificus, but also the ones present in the venoms from C. d. collilineatus, C. d. cascavella and C. d. marajoensis. Antisera from horses immunized with individual crotoxin or PLA2, although in lesser titers, were also able of recognizing the toxins in all four Crotalus species and neutralize the lethality of the C. d. terrificus venom.

An alternative method for purifying and detoxifying diphtheria toxin

Infections caused by Corynebacterium diphtheriae frequently induce situations in which very small doses of antigens injected intradermally can cause strong inflammatory reactions. This bacterium secretes the diphtheria toxin (DT), a virulence factor that can be lethal to the human organism at doses below 0.1 μg/kg of body weight. The present work proposes alternative methods of DT purification using affinity chromatography and of DT detoxification through conjugating with the polymer methoxypolyethylene glycol activated (mPEG). Tests were performed to evaluate: the formation of edemas and the presence of dermonecrotic activity, in vitro cytotoxicity to Vero cells, the neutralizing activity of serum from guinea pigs immunized with the diphtheria toxoid inactivated with mPEG, and the immunogenic activity of the purified and modified toxin. The results indicated that purification with Blue Sepharose was an efficient method, yielding antigen purity equivalent to 2600 Lf/mg of protein nitrogen. The modification of the Purified Toxin with mPEG did not result in the formation of edema or necrosis although it was immunogenic and stimulated the formation of antibodies that could neutralize the Purified Toxin. The toxoid obtained from the purified toxin maintained its immunogenic characteristics, inducing antibodies with neutralizing activity; edema and necrosis were still observed, however.