Immunochemical cross-reactivity of neurotoxic phospholipase A 2 enzymes from Indian cobra ( Naja naja naja) venom using polyclonal antibodies

Abstract

B. S. Basavarajappa, S. C. Guru and T. V. Gowda. Immunochemical cross-reactivity of neurotoxic phospholipase A 2 enzymes from Indian cobra ( Naja naja naja) venom using polyclonal antibodies. Toxicon 31, 1167–1177, 1993.—Rabbit antibodies were prepared against purified phospholipase A 2 (NN-XI a-PLA 2) from Indian cobra ( Naja naja naja) venom. The PLA 2 has haemolytic, neurotoxic, myotoxic, cytotoxic and oedema-inducing activities apart from the catalytic activity. The immunological cross-reactivity of structurally similar neurotoxic PLA 2s was investigated using enzyme-linked immunosorbent assay (ELISA) and immunodiffusion. Anti-NN-XI a-PLA 2 IgG cross-reacted with other purified neurotoxic PLA 2s from the same venom. Immunochemical cross-reactions of anti-NN-XI a-PLA 2 IgG with NN-XI a-PLA 2, NN-XI b-PLA 2, NN-XIII-PLA 2, NN-IV bl-PLA 2 and NN-V b-PLA 2 were shown by a very high ELISA titre and a single precipitin band on double immunodiffusion agarose plates. The catalytic activity of these PLA 2s was inhibited dose-dependently by anti-NN-XI a-PLA 2 IgG but was unable to neutralize lethality and neurotoxic symptoms in experimental animals injected with neurotoxic PLA 2. Anti-NN-XI a-PLA 2 IgG fails to neutralize myotoxicity and oedema-inducing activities of NN-XI a-PLA 2 and NN-XIII-PLA 2. Anti-NN-XI a-PLA 2 IgG inhibited cytotoxic effects of NN-XI a-PLA 2 dose-dependently, but failed to inhibit NN-XIII-PLA 2-induced cytotoxicity. Direct haemolytic activity of NN-XI a-PLA 2 and NN-XIII-PLA 2 was inhibited dose-dependently by these antibodies. The results indicate the presence of separate catalytic and pharmacologic site(s).