Enhanced immune sera and vaccine: safe approach to treat scorpion envenoming

Abstract

Irradiation of Androctonus australis hector venom using a dose of 2 kGy has successfully abolished toxicity without reducing its antigenic or immunogenic properties. Toxicity of irradiated antigen was abolished until 20 times of LD(50) of native venom. Analysis of physiopathological effects induced by native and irradiated venoms was assessed by the analysis of tissue damage, immunohistochemistry and metabolical analysis in the organs (heart, lungs and liver). Immunological response of Aah venom using native or irradiated venom showed high titers of IgG1 in the plasma of immunized animals with native venom suggesting that Th2 cells were predominantly involved in the immune response. In the other hand, irradiated venom induced high titers of IgG2, indicating a predominantly Th1 type response. A protective effect of immunized mice with irradiated venom was evaluated. Immunized mice were protected from the toxic effects of native venom doses at one, three and six months after immunization. Mice were protected against a challenge of 4 LD(50) doses of native venom, one month after immunization. This protective effect was improved and effective at 3 and 6 months, all immunized mice were protected respectively against 6 and 10 LD(50) of native venom. At the one-month time point, the protective effect of mice was associated with high levels of antibodies in the plasma of immunized mice. However, despite the persistence of higher protection levels, the antibody titers decreased in a time-dependent manner. These results suggest that additional factors other than circulating antibodies provided the long-term protective activity produced by immunization with irradiated venom.