MOLECULAR CHARACTERIZATION, ANTIGENICITY AND IMMUNOGENICITY OF ANATOXIC POLYMERIC FORMS CONFERRING PROTECTION AGAINST SCORPION VENOMS

Two polymeric forms of Buthus occitamus tunetanus (Bet) G-50 and Andro ctonus australis hector (Aah) G-50 were obtained by controlled polymer ization with glutaraldehyde. Their mol. wts, determined by sodium dode cyl sulfate-polyacrylamide gel electrophoresis and exclusion high-perf ormance liquid chromatography using radiolabelled toxin, ranged from 1 4,000 to 90,000 and 90,000 to 100,000 for Aah G-50 and Bot G-50, respe ctively. Modification of about 20% of the lysine residues yielded comp letely detoxified Bot G-50 fractions which retained the antigenic cros s-reactivity with the native G-50 fraction, venom and toxins. High lev els of specific antibodies against venoms and toxins were generated by immunization with prepared polymeric forms because absorbance values higher than 3 units were regularly observed by enzyme-linked immunosor bent assay with immune sera dilutions of 1/10,000, In vitro protection experiments demonstrated that immune sera from mice, horse and monkey s efficiently neutralized either Aah or Bot venom. Depending on the ad juvant and animal model species used, the neutralizing titre estimated by subcutaneous injection in mice varied between 20 and 40 LD50/ml. T he in vivo protection assays showed that immunized mice could resist t he challenge by six times the LDS, amounts of the toxic fraction. This protection was found to be long-lived. It was concluded that G-50 pol ymeric forms are highly detoxified and immunogenic, and should be usef ul for the production of potent polyvalent antivenom against scorpion toxins. They could also be considered for further studies towards the development of vaccine candidates. (C) 1997 Elsevier Science Ltd.