Partial purification and characterization of <i>Echinococcusgranulosus</i> antigen 5, extracted from hydatid cyst: Radiolabeling study with Iodine 125

Abstract Cystic echinococcosis is a parasitic disease caused by the development of the larval form (hydatid cyst) of Echinococcus granulosus sensu lato (s.l) in humans and herbivores. In this study, antigen 5 (Ag 5), recognized as the major and most immunogenic fraction of E. granulosus (s.l), was partially purified using ammonium sulfate precipitation at 70 % saturation and characterized by physicochemical and immunological methods. Analysis of the supernatant resulting from the precipitation showed typical mobility for antigen 5. The antigen produced a single precipitation arc when tested against a pool of sera from patients and rabbits immunized with this antigen. A band of approximately 66 kDa was observed through SDS-PAGE under denaturing conditions. Radiolabeling of the antigen with iodine-125 (I 125 ) achieved a yield of 63 % with a radiochemical purity of 92.6 %. In evaluating antigenic integrity, a tolerable non-specific binding of 16 % was observed, alongside satisfactory specific binding of 60 % when tested with rabbit anti-fraction 5 serum. These preliminary results are promising and will be further refined to determine optimal conditions for preparing a high-quality tracer, which could be valuable in the diagnosis of hydatid disease.