Induction of neutralizing antibodies in mice immunized with scorpion toxins detoxified by liposomal entrapment

Abstract

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

Engineered nanoparticles mimicking cell membranes for toxin neutralization

“…It has also been observed that direct encapsulation of animal venoms using liposomes significantly reduced toxicity, and the resulting formulations were effective at raising anti-venom antibodies [156–158]. While nanoparticle-sequestered toxin has several advantages over conventional toxoid preparations, formulations containing non-denatured toxins inevitably raise safety concerns.…”

Innovative Immunization Strategies for Antivenom Development

“…In relation to delivery systems, already by 1985, New and colleagues employed sphingomyelin-cholesterol liposomes to encapsulate Echis carinatus snake venom, in order to raise an efficacious immune response in mice, rabbits, and sheep [ 143 ]. Other studies also utilized liposomes with successful results [ 77 , 144 , 145 , 146 , 147 , 148 , 149 ]. For instance, in 1988, Laing et al encapsulated E. carinatus snake venom in sphingomyelin-cholesterol liposomes, and utilized these to immunize mice [ 144 ].…”

“…In 1993, Laing & Theakston demonstrated protection in immunized mice against 4.3 LD 50 s (subcutaneous route) of E. ocellatus venom after immunization with venom and lipopolysaccharide (LPS) encapsulated in membrane-stabilized reverse phase evaporation liposomes [ 147 ]. Fonseca et al also reported immunization of mice with encapsulated T. serrulatus scorpion venom, providing antiserum with neutralization capacity of up to 3 LD 50 s (subcutaneous route) against Tst-G50 in naïve mice [ 148 ].…”

Evolution of alternative methodologies of scorpion antivenoms production

“…This would allow immunized animals to eliminate small doses of toxin over time, thereby reducing their toxicity. Chavez-Olortegui et al (1991) and Fonseca et al (1997) used sphingomyelin-cholesterol liposomes to partially detoxify a toxic fraction of T. serrulatus venom obtained by Sephadex G-50 fractionation; however, the mouse's antivenom generated following immunization had a reduced neutralizing potential compared to that generated following immunization with the toxic non-encapsulated fraction. These data indicated that detoxification of venoms using liposome-based approaches requires additional studies and development.…”