Pharmacological characterization and neutralization of the venoms used in the production of Bothropic antivenom in Brazil.

Some pharmacological effects of the venoms of five different Brazilian Bothrops species and a pool of these venoms (AgB) were quantified. The ability of polyspecific Bothropic antivenom produced at Fundação Ezequiel Dias (FUNED, Brazil) to neutralize the principal toxic and enzymatic activities was studied using in vivo and in vitro assays. The lethality, hemorrhagic, necrotizing, proteolytic, phospholipase, coagulant and fibrinolytic activities were measured for each of these venoms. Comparison of protein electrophoretic patterns showed significant differences such as the presence of common and also unique components. Furthermore, experimental studies revealed differences in their biological properties among individual samples. It was found that the Bothrops antivenom was highly effective in the neutralization of the toxic activities of all venoms tested. In addition, indirect ELISA was used to compare the antigenic cross-reactivity for each of the five Bothrops venoms as well as the venoms of B. atrox, B. leucurus and B. erythromelas which were not included in the antigenic pool (AgB). Therefore, the characterization of several toxic activities of snake venoms is necessary, if toxicity is to be properly evaluated. Results indicate that the Brazilian antivenom prepared at FUNED against Bothrops snakes is effective in neutralizing the main toxic effects of Bothrops venoms.

Kallikrein-like proteinase from bushmaster snake venom.

A kallikrein-like proteinase of Lachesis muta muta (bushmaster) venom, designated LV-Ka, was purified by gel filtration and anion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 33 kDa monomeric glycoprotein, the Mr of which fell to 28 kDa after deglycosylation with PNGase F. Approximately 77% of the protein sequence was determined by sequencing the various fragments derived from digestions with endoproteases. The partial sequence obtained suggests that LV-Ka is of a similar size to other serine proteinases (i.e., approximately 234 amino acid residues). Sequence studies on the NH2-terminal region of the protein indicate that LV-Ka shares a high degree of sequence homology with the kallikrein-like enzymes EI and EII from Crotalus atrox, with crotalase from Crotalus adamanteus and significant homology with other serine proteinases from snake venoms and vertebrate serum enzymes. LV-Ka showed kallikrein-like activity, releasing bradikinin from kininogen as evidenced by guinea pig bioassay. In addition, intravenous injection of the proteinase (0.8 microg/g) was shown to lower blood pressure in experimental rats. In vitro, the isolated proteinase was shown to have neither fibrin(ogeno)lytic activity nor coagulant effect. LV-Ka was active upon the kallikrein substrates S-2266 and S-2302 (specific activity=13.0 and 31.5 U/mg, respectively; crude venom=0.25 and 6.0 U/mg) but had no proteolytic effect on dimethylcasein and insulin B chain. Its enzymatic activity was inhibited by NPGB and PMSF, indicating that the enzyme is a serine proteinase. Interestingly, one of the other reactions catalyzed by plasma kallikrein, the activation of plasminogen was one of the activities exhibited by LV-Ka.