IMMUNOCHEMICAL CROSS-REACTIVITY OF NEUROTOXIC PHOSPHOLIPASE-A(2) ENZYMES FROM INDIAN COBRA (NAJA-NAJA-NAJA) VENOM USING POLYCLONAL ANTIBODIES

Rabbit antibodies were prepared against purified phospholipase A2 (NN- XI(a)-PLA2) from Indian cobra (Naja naja naja) venom. The PLA2 has hae molytic, neurotoxic, myotoxic, cytotoxic and oedema-inducing activitie s apart from the catalytic activity. The immunological cross-reactivit y of structurally similar neurotoxic PLA2s was investigated using enzy me-linked immunosorbent assay (ELISA) and immunodiffusion. Anti-NN-XI( a)-PLA2 IgG cross-reacted with other purified neurotoxic PLA2S from th e same venom. Immunochemical cross-reactions of anti-NN-XI(a)-PLA2 IgG with NN-XI(a)-PLA2, NN-XI(b)-PLA2, NN-XIII-PLA, NN-IV(b1)-PLA2 and NN -V(b)-PLA, were shown by a very high ELISA titre and a single precipit in band on double immunodiffusion agarose plates. The catalytic activi ty of these PLA2s was inhibited dose-dependently by anti-NN-XI(a)-PLA2 IgG but was unable to neutralize lethality and neurotoxic symptoms in experimental animals injected with neurotoxic PLA2. Anti-NN-XI(a)-PLA , IgG fails to neutralize myotoxicity and oedema-inducing activities o f NN-XI(a)-PLA2 and NN-XIII-PLA2. Anti-NN-XI(a)-PLA2 IgG inhibited cyt otoxic effects of NN-XI(a)-PLA2 dose-dependently, but failed to inhibi t NN-XIII-PLA2-induced cytotoxicity. Direct haemolytic activity of NN- XI(a)-PLA2 and NN-XIII-PLA2 was inhibited dose-dependently by these an tibodies. The results indicate the presence of separate catalytic and pharmacologic site(s).