Lectins in the brown ear tick, Rhipicephalus appendiculatus: detection and partial characterization

Abstract

Lectins (agglutinins) were detected and isolated from the hemolymph and gut of Rhipicephalus appendiculatus, the vector of Theileria parva, using various vertebrate red blood cells (RBC). Although the hemolymph lectin agglutinated RBC's of horse at the titre of 4096, mouse (2048), rabbit (512) and rat (128), it did not agglutinate those of domestic animal tick hosts, e.g. cow, goat and sheep. Erythrocytes from some wildlife hosts showed agglutination, with rhino showing the highest titre (4096), zebra (512) and giraffe (256). Virtually no agglutination was observed with erythrocytes from Thomson's gazelle, and the oryx and buffalo gave no agglutination at all. The hemolymph lectin was inhibited by Xylose, N-acetyl galactosamine and partially by β-d-Fructose. The gut lectin gave an agglutination titre of 4096, with rabbit erythrocytes, mouse (512), horse (4) and 16 for oryx, giraffe and Thomson's gazelle. It also did not agglutinate cattle or sheep erythrocytes but showed trace agglutination (2) for goat rbcs. The gut lectin was inhibited by D(-) mannosamine, D(+) glucosamine, D(+) galactosamine and Fetuin. Free lectins were not detected in the gut lumen, but in the gut integral membrane. The heterogeneity in the agglutination of the different erythrocytes suggests differences in the binding affinity and quantities of lectins or presence of several different lectins. If the lectin binding affinity of the erythrocyte surface membrane of T. parva infected cells is identical to that of uninfected erythrocytes then, the fact that the hemolymph and gut lectins did not agglutinate the domestic animal erythrocytes might be due to evolutionary adaptations and may influence disease transmission.