A Perspective on the Emergence of Sialic Acids as Potent Determinants Affecting Leishmania Biology

Figure 3

Enhanced 9-O-AcSA on Leishmania sp. with increased α2-6 linked SA. (a) Differential presence of 9-O-AcSA on the surface of virulent and avirulent promastigotes. The binding of FITC-Achatinin-H with promastigotes AG83 and UR6 was analyzed before and after de-O-acetylation followed by subsequent desialylation using sialidase from Arthrobacter ureafaciens by flow cytometry as described in [68, 69]. (b) Demonstration of 9-O-AcSA by ELISA. Membrane lysates of the respective strains were incubated separately with Achatinin-H and the binding was recorded colorimetrically as described in [68]. (c) Increased number of surface 9-O-AcSA containing sialoglycotope on AG83 and their minimal distribution on UR6 promastigotes. The receptors (O-acetylated sialoglycoproteins) on AG83 were estimated by determining the specific binding of AG83 (black diamond) by subtracting the nonspecific binding (black square) using excess unlabelled Achatinin-H from total binding (white square). UR6 (white diamond) evidenced a basal level of specific binding. Inset: scatchard plot showing the binding of ¹²⁵I-Achatinin-H with 9-O-AcSA containing sialoglycoproteins present on AG83 promastigotes as described in [69]. (d) Presence of 9-O-acetylated sialoglycoproteins as detected by Western blot on virulent promastigotes of different Leishmania sp. The specificity of binding was examined by using membrane proteins of de-O-acetylated promastigotes as described in [68, 69] (reproduced and adapted from [68, 69] with permission of the publishers, Oxford University Press, and Cambridge University Press, resp.).