Selection and identification of specific glycoproteins and glycan biomarkers of macrophages involved in Mycobacterium tuberculosis infection.

Macrophages are the primary host target cells of Mycobacterium tuberculosis (M.tb). However, little is known about the changes of membrane glycopatterns of macrophages in response to M. tb infection. Using lectin microarrays we compared the differential expression of glycopatterns of macrophages upon stimulation with the heat-inactivated virulent M.tb H37Rv or attenuate M.tb H37Ra. We found that widespread alteration of macrophage membrane glycopatterns were induced by the heat-inactivated virulent M. tb H37Rv, as shown by the significantly changed binding abilities of 11 lectins (sugar binding proteins) among 40 lectins tested. The binding ability of the lectin ABA to macrophages showed the greatest increase after virulent M. tb H37Rv treatment, which suggests that the expression of N-acetyl-d-lactosamine (ABA binding ligand Galβ1-3GalNAc, O-link glycan) is mainly increased on macrophages during virulent M.tb infection. Addition of ABA blocked the attachment/engulfment of M. tb H37Rv, but not H37Ra, to macrophages. Further, increased glycosylated CD44, one of ABA-binding glycoproteins on macrophages, was identified by pull-down assays with ABA-agarose, followed by mass spectrometry and western blotting. ABA directly binds with Galβ1-3GalNAc-glycosylated CD44 on macrophage, and inhibits M. tb mannose-capped lipoarabinomannan (ManLAM) binding to glycosylated CD44. Moreover, ABA increases IL-6, but reduces IL-10 production of ManLAM-treated macrophages and inhibits M. tb H37Rv-induced necrosis in macrophages. Our study will help to reveal the mechanism of pathogenicity and virulence of M. tb from a new perspective and provide a potential new diagnostic and therapeutic strategy for tuberculosis based on glycopatterns, ABA and its ligand Galβ1-3GalNAc-glycosylated CD44 target molecule on macrophage.