A CHICKEN ANTI-CONOID MONOCLONAL-ANTIBODY IDENTIFIES A COMMON EPITOPEWHICH IS PRESENT ON MOTILE STAGES OF EIMERIA, NEOSPORA, AND TOXOPLASMA

The chicken monoclonal antibody (mAb) 6D12-G10, raised against Eimeria acervulina sporozoites, has previously been shown to recognize the co noid of E. acervulina sporozoites and inhibit sporozoite invasion of l ymphocytes in vitro. In indirect immunofluorescent assay, the mAb 6D12 -G10 also reacted with merozoites from E. acervulina and identified a 21-kDa merozoite protein on western blots. By confocal laser scanning microscopy, the conoid of sporozoites from 6 different avian Eimeria s pecies (E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox, and E. tenella) were reactive with 6D12-G10 mAb. Furthermore, the 6D12-G1 0 mAb also showed cross-reactivity with motile stages of 2 closely rel ated apicomplexans, Neospora, and Toxoplasma. These results indicate t hat the mAb 6D12-G10 identifies a conserved epitope on the conoid that is important in host cell invasion by the apicomplexan parasites.