Defence mechanism against Coccidia using common antigens related with host cell invasion

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Coccidiosis is caused by intercellular protozoa belonging to apicomplexans. After initial infection with Coccidia, hosts acquire immunity to reinfection and much effort is currentry underway to identify potential vaccine antigens capable of inducing protective host immune response. In order to identify potential receptor molecules of Eimeria which are involved in host cell invasion, several chicken monoclonal antibodies (mAbs) against E.acervulina (EA) were developed. One of these mAbs, 6D-12-G10, recognized the conoid antigen of EA sporozoites and significantry inhibited sporozoite invasion of CD8-positive T lymphocytes in vitro. Furthermore, this mAb also showed cross-reactivity with tachyzoites from closely related coccidian parasite including Neospora and Toxoplasma. The species-specificity and cross-reactivity of other mAbs were determined using the sporozoites of several different avian Eimeria species including EA, E.brunetti, E.maxima, E.mitis, E.necatrix, E.praecox and E.tenel … More la. The mAb 8E-1 recognized a common antigenic determinant present on all Eimeria species whereas the mAbs HE-4, 8D-2 and 5D-11 recognized interspeciese-specific epitopes. The mAbs 8C-3 identified a species-specific epitope.The infection of Cryptosporidium parasites belonging to the phylum Apicomplexa is now a well recognized cause diarrhea in immunologically healthy and immunocompromised humans and animals throughout the world. In this study, we studied the cross-reactivity of these chicken mAbs with C.muris and C.Parvum. By indirect immunofluoreacsnt assay, 6D-12-G10 showed an intense fluorescent staining a 47.9 kDa protein, and mAbs 5D-11 identified a 154.9 kDa protein of C.muris. Mabs 6D-12-G10 and HE-4 showed an intense fluorescent staining on C.parvum sporozoites. Furthermore, in western blloting, mAbs 6D-12-G10 identified a 47.9 kDa protein of C.parvum. These results indicate that some of these mAbs may identify a common epitope which represent on the apical complex of the apicomplexan parasites. Less