Lethal potency and fractionation of Duvernoy's secretion from the brown tree snake, Boiga irregularis

The liquid secretion contained only 15% protein and had relatively low proteolytic activity. The reconstituted crude secretion had a murine i.p. LD50 of 10.33 mg/kg and was not hemorrhagic in doses up to 200 micrograms. Fast Protein Liquid Chromatographic (FPLC) cation exchange analysis of reconstituted crude secretion resulted in resolution of 16 peaks. Lethal activity was identified in three peaks. The major lethal fraction was 12.5% of the secretion protein and had a murine i.p. LD50 of 7.3 mg/kg. A pooled fraction containing two lethal peaks which comprised 9.4% of secretion protein had moderate proteolytic activity and produced myoglobinuria in mice. The fraction had an approximate murine i.p. LD50 of 3.7 mg/kg. Microscopic examination of muscle tissue from mice succumbing to this fraction revealed multifocal myofiber degeneration and necrosis. SDS-PAGE indicated that the major lethal fraction contained three proteins with mol. wts of 12,500, 18,000 and 52,000 and the myotoxic fraction contained two proteins with mol. wts of 14,500 and 17,000. While B. irregularis Duvernoy's secretion has a low lethal index, it does contain a myotoxic fraction with moderate lethal potency. These observations and recent data describing clinical envenomation of several infant patients suggest that large specimens may pose a hazard to infants and small children.