Interaction of human mannose-binding protein with Mycobacterium avium

The interaction between human mannose-binding protein (MBP) and Mycobacterium avium was explored. By ELISA, calcium-dependent and mannan-inhibitable binding of human recombinant MBP (rMBP) to live M. avium was observed. Preincubation of M. avium with rMBP resulted in a 2-fold increase in uptake by human neutrophils. Mycobacterial cell wall components were assessed by ELISA for their ability to bind the carbohydrate recognition domain of rMBP. The best ligand was mannosyl-lipoarabinomannan, followed by lipomannan, phosphatidylinositol mannoside, arabinosyl-lipoarabinomannan, and dimycolated trehalose (cord factor). rMBP did not bind to partially purified lipid fractions containing glycopeptidolipids. These results are consistent with the known structural basis for rMBP ligand recognition. They suggest that MBP may play a role in host defense against M. avium by opsonizing both whole organisms and free cell wall components for internalization.