The surface charge of Trypanosoma cruzi: analysis using cell electrophoresis, lectins and ultrastructural cytochemistry.

The surface charge of epimastigote and trypomastigote forms of Trypanosoma cruzi was analysed by three approaches: a) visualization by electron microscopy of the binding of cationic particles (cationized ferritin at pH 7.2 and colloidal iron hydroxyde at pH 1.8) to the parasite's surface, b) visualization of the binding of fluorescein-labeled lectins (PNA and LPA) to the parasite's surface, and c) by cell electrophoresis. In all cases control, trypsin and neuraminidase-treated cells were analysed. The results obtained indicate that sialic acid residues located on the parasite's surface are responsible for the binding of cationic particles to it and the major component responsible for the net negative surface charge presented by T. cruzi. Phosphate groups, associated to phospholipids, also contribute to the negative surface charge. The effect of previous incubation of the parasites in the presence of lectins (ConA, WGA, PNA, RCA and LPA) on their surface charge was also analysed by cell electrophoresis.