Immunoenzymatic quantitation of antibodies to Bothrops asper myotoxins after polyvalent antivenom administration in mice

ABSTRACT

Two quantitative enzyme-ummunoassays (EIA) for Bothrops asper myotoxin and anti-myotoxin antibodies, respectively, were utilized to study their in vivo distribution in mice (Swiss, 18 to 20 g). After polyvalent antivenom (0.4 ml) administration by the iv route, there was an immediated peak in plasma anti-myotoxin antibodies which declined rapidly during the first hour, and then decreased more gradually. Anti-myotoxin antibodies were detected in muscular tissue (gastrocnemius) following iv injection of antivenom. After im injection of antivenom (0.4 ml), a slow and steady increase in plasma anmti-myotoxin levels was observed, with a peak at 24 h. Mice that received antivenom (0.4 ml) by the iv or im route 15 min after im injection of B. asper venom (100 ug) had lower levels of plasma anti-myotoxin antibodies than controls injected with antivenom only, suggesting that at least a fraction of the antibodies combines with myotoxins in vivo. Myotoxin was not detected in plasma at any time after venom injection by the im (100 ug) or ip (40 ug) route. Following iv injection of 50 ug of purified myotoxin II, all plasma samples were also negative, at a detection limit of 10 ng/ml. It was demonstrated that myotoxin II binds to mouse erythrocytes in vitro, a fact that could partially explain its rapid in vivo disappearance from plasma. The present results on the distribution of anti-myotoxin antibodies in vivo are in agreement with previous experimental studies reporting the poor neutralization of myotoxicity induced by B. asper venom when antivenom is injected im, in comparison to iv injection