Protective effect of Eimeria stiedae coproantigen against hepatic coccidiosis in rabbits.

Immunization of rabbits against hepatic coccidiosis was tried. The animals were immunized twice with Eimeria stiedae coproantigen in freund's adjuvant with two week intervals. The rabbits were challenged orally with sporulated E. stiedae oocysts one week post last injection. The protection was assessed by number of oocysts output, number of focal liver lesions, clinical sings and antibody response. The immunization resulted in 70% protection from infection and decline in oocysts count. High level of IgG response in immunized rabbits than control infected ones was occurred and being responsible for the recorded protection. The electrophoretic make up of the coproantigen and oocyst antigen showed different patterns of separation. Common as well as specific bands to each antigen were identified. Using the rabbit sera after 3 weeks post vaccination in immunoblot assay, immunogenic components were detected of molecular weight 155, 103, 74, 66, 44, 22KD with coproantigen and 155, 115, 57, 26 KD with oocyst antigen. While, the rabbit sera after 2 and 4 weeks post challenge reacted with oocyts antigen, in immunoblot assay, revealing immunogenic bands of molecular weight 155, 115, 57, 26, 22KD and 155, 115, 57, 25 KD respectively. Bands of 22KD and 155KD are partially responsible for eliciting host protective immune response where they were recognized by immunized sera in coproantigen and by immunized infected sera in oocyst antigen.

Cross-reaction: a common trait among helminthes.

Cross-reaction between three important zoonotic helminths, Fasciola gigantica, Trichinella spiralis and Echinococcus granulosus, was proved by ELISA. Cross-binding activities in the prepared antisera were strongly directed towards protoscolices and hydatid fluid antigens of E. granulosus rather than to F. gigantica and T. spiralis antigens. Two sets of polypeptides were identified in each antigen by immunoblot; species-specific and cross-reactive. Cross-reactive components in F. gigantica antigen were 205 KD, 178 KD, 166 KD, 106 KD, 100 KD, 65 KD, 45 KD and 32 KD. While, cross-reactive molecules in T. spiralis antigen were 205 KD, 191 KD, 166 KD, 148 KD, 132 KD, and 32 KD. In protoscolices antigen six cross-reactive components were identified, 205 KD, 191 KD, 149 KD, 106 KD, 45 and 32 KD. Moreover, 205 KD, 190 KD, 177 KD, 149 KD, 103 KD and 33 KD were detected in hydatid fluid antigen by heterologous antisera. Interestingly, three polypeptides of 205 KD, 149 KD and 32 KD showed broad immunogenicity with the developed antisera raising the prospect of being putative common immunoprophylactic components.