Preparations of toxic components from Naja kaouthia venom by selective heat denaturation

A simple procedure to prepare the toxic components from Naja kaouthia venom for use as immunogens has been studied. The aim was to produce serum rich in antitoxins. By heating the venom (1-6 mg/ml) at 100 degrees C for 10 min at pH 5.0, at least 10 proteins with MW greater than 25,000 daltons were precipitated and removed. The toxic components, i.e., postsynaptic toxins, Direct Lytic Factor (DLF), and phospholipase A2 were relatively stable to this treatment; however, their activities were progressively lost as the heating time was prolonged. The LD50S of the heated (100 degrees C, 10 min) and the unheated venom were 0.37 and 0.325 mg/kg, respectively. As compared to the unheated venom, immunization of rabbits with the heated venom resulted in a 3.38-fold increase in precipitable antibodies against N. kaouthia toxin 3 and a 1.85-fold increase in neutralizing capacity. This toxin preparation should be useful as an immunogen or as a starting material for chemical modification prior to immunization in the production of potent therapeutic antiserum.