INDUCTION OF NEUTRALIZING ANTIBODIES IN MICE IMMUNIZED WITH SCORPION TOXINS DETOXIFIED BY LIPOSOMAL ENTRAPMENT

The possibility of producing neutralizing antibodies against the letha l effects of scorpion toxins was evaluated in the mouse model by immun ization with an immunogen devoid of toxicity. A toxic fraction (5 mg) from the venom of the scorpion Tityus serrulatus was entrapped in sphi ngomyelin-cholesterol liposomes. The liposomes were treated for 1 h at 37 degrees C with a 1% (w/w) trypsin solution in 0.2 M sodium carbona te buffer, pH 8.3. This treatment led to a strong reduction in venom t oxicity. Immunization was performed as follows: mice were injected sc with 20 mu g of the liposome-entrapped toxic fraction on days 1 and 21 and a final injection (20 mu g) was administered ip on day 36. After injection of the immunogen, all mice developed an IgG response which w as shown to be specific for the toxic antigen. The antibodies were mea sured 10 days after the end of the immunization protocol. In an in vit ro neutralization assay we observed that pre-incubation of a lethal do se of the toxic fraction with immune serum strongly reduced its toxici ty. In vivo protection assays showed that mice with anti-toxin antibod ies could resist the challenge with the toxic fraction, which killed, 30 min after injection, ail nonimmune control mice.