Developmentally regulated lectins in Eimeria species and their role in avian coccidiosis

Avian coccidiosis caused by Eimeria species is characterized by rather specific site infections of the intestine. We used hemagglutination and hemagglutination inhibition assays on various developmental stages of Eimeria tenella and on sporozoites of Eimeria acervulina and Eimeria maxima to assay for parasite lectins. Various monosaccharides, polysaccharides, and glycoproteins were used to demonstrate differences in sugar specificity of the lectins between these species. Surface lectins were found on the primary infective stage, i.e., sporozoites, but not on merozoites or unsporulated oocysts. Also, there were differences in the specificities of the various sugar lectins among the different parasite species. Furthermore, there was a dose-dependent reduction of infection of tissue culture cells by sporozoites of E. tenella that were continuously exposed to fetuin, 1 of the specific inhibitors of the lectin. The results of our study are unique in that in 3 species of avian Eimeria all have a lectin on their sporozoites, but the lectins for each species have different sugar specificities. We hypothesize that these lectins found on the surface of the sporozoites may play a role in determining the site of infection within the intestine of the host.