saasp21 - Systematic & Applied Acarology Special...

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(2006) 21, 1–15 1 © 2006 ISSN 1461-0183 Potential role of lectins in ticks: Rhipicephalus appendiculatus and Rhipicephalus pulchellus (Acari: Ixodidae) ESTHER KIBUKA-SEBITOSI Centre for African Renaissance Studies (CARS), University of South Africa (UNISA) 287 Skinner Street, Pretoria, P.O. Box 392, UNISA, 0003 Pretoria, South Africa; E-mail: sebitek@unisa.ac.za Abstract The role of lectins in tick vectors was investigated by comparing the presence of lectins in the hemolymph, guts and salivary glands of two tick species: (1) Rhipicephalus appendiculatus, the vector of Theileria parva, and (2) Rhipicephalus pulchellus, which is refractory to this protozoan parasite. There was variation in the agglutination titres with erythrocytes from bovine, mouse and rabbit erythrocytes, suggesting different binding affinities and quantities of lectins. The hemolymph from R. pulchellus gave the highest agglutination titer with mouse erythrocytes (1024) compared to that obtained with rabbit cells (8). No agglutination was observed with bovine erythrocytes when assayed with the gut, salivary gland or hemolymph lectins from either tick species. The gut lectin from R. pulchellus also demonstrated high titers (1024) with rabbit cells but moderate titers with mouse erythrocytes (256). Hemolymph from T . parva- infected R. appendiculatus contained double (512) the quantities of lectins compared to uninfected ticks (256) with mouse erythrocytes suggesting an increase in the amount of lectin in the presence of infection and implying a role of lectins in the immunity of these arthropods. Lectin from the gut of R. appendiculatus agglutinated purified piroplasms, a stage in the T. parva life cycle ingested by the tick when it feeds on infected cattle. The anti-lectin antibodies conjugated with Fluorescein isothiocyanate (FITC) bound to the piroplasms, suggesting a possible point at which intervention may be developed for the control of theileriosis. The significance of lectins in tick parasite transmission lies in the fact that these molecules play an important part in cell-to-cell adhesion. Defining their binding specificities and quantities in a given tick species may lead to development of a novel type of disease control whose mode of action would be based on competing for the ligands for binding to pathogen receptors or preventing adhesion to host tissues (transmission-blocking), thereby preventing infection. This study revealed that tick-derived antigens in the form of lectins produced antibodies that recognized the piroplasm as well as schizont stages of T. parva. With increasing attention on vaccination of cattle against ticks, there is a need to identify and show target antigens within the tick. The study has elucidated three targets, the salivary gland, hemolymph and the gut. It forms one of the first reports on the effect of lectin antibody on the development and transmission of
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saasp21 - Systematic & Applied Acarology Special...

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