Epitope mapping studies of snake venom phospholipase A2 using monoclonal antibodies.

Fifteen different monoclonal antibodies developed against pseudexin, a snake venom phospholipase A2 with presynaptic neurotoxicity, were screened for linear epitope recognition. Peptides (9-mers) spanning pseudexin were synthesized by using alanine-derivatized polyethylene pins and subsequently probed with antibody. Four antibodies bound to toxin peptides and were detected with an enzyme-linked immunosorbent assay. Three of the bound antibodies recognized a site important in calcium binding and the interlocking of dimeric forms of snake venom phospholipase A2. Analogous regions from other phospholipases were synthesized and probed with the four reactive antibodies. A good correlation was found between the reactivity of whole molecule phospholipases and peptide regions with the antibodies. Monoclonal antibodies neutralizing the lethal or enzymatic effects of pseudexin did not recognize any linear epitopes.