The 19-kDa antigen of Mycobacterium tuberculosis is a major adhesin that binds the mannose receptor of THP-1 monocytic cells and promotes phagocytosis of mycobacteria

• Published in: Microbial pathogenesis 2005-09, Vol.39 (3), p.97-107
• Main Authors: Diaz-Silvestre, Hugo, Espinosa-Cueto, Patricia, Sanchez-Gonzalez, Alejandro, Esparza-Ceron, Miguel A., Pereira-Suarez, Ana Laura, Bernal-Fernandez, German, Espitia, Clara, Mancilla, Raul
• Format: Article
• Language: English
• Subjects: 19-kDa antigen; Acetylglucosamine - pharmacology; adhesins; Adhesins, Bacterial - immunology; Adhesins, Bacterial - metabolism; animal pathogenic bacteria; Antigens, Bacterial - immunology; Bacterial Adhesion; bacterial antigens; Biological and medical sciences; Enzyme-Linked Immunosorbent Assay; Fundamental and applied biological sciences. Psychology; human health; Humans; Immunoblotting; Immunoprecipitation; Lectins, C-Type - immunology; Lectins, C-Type - metabolism; Macrophages; Mannans - pharmacology; mannose; Mannose receptor; Mannose-Binding Lectins - immunology; Mannose-Binding Lectins - metabolism; Methylmannosides - pharmacology; Microbiology; monocytes; Monocytes - immunology; Monocytes - metabolism; Monocytes - microbiology; Mycobacterium smegmatis; Mycobacterium tuberculosis; Mycobacterium tuberculosis - immunology; Mycobacterium tuberculosis - metabolism; Phagocytosis; Phagocytosis - immunology; protein binding; Protein Binding - immunology; receptors; Receptors, Cell Surface - immunology; Receptors, Cell Surface - metabolism; tuberculosis; Tuberculosis - microbiology
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/j.micpath.2005.06.002

Identification of mycobacterial adhesins is needed to understand better the pathogenesis of tuberculosis and to develop new strategies to fight this infection. In this work, THP-1 monocytic cells were incubated with Mycobacterium tuberculosis culture filtrate proteins labelled with biotin and a dominant 19-kDa adhesin was found. This adhesin was characterized as the glycosylated and acylated 19-kDa antigen (Rv 3763). These findings were confirmed in assays with culture filtrate proteins and cell-wall fractions from a recombinant Mycobacterium smegmatis strain that overexpresses the 19-kDa antigen. Further, fluorescent microspheres coated with recombinant culture filtrate proteins adhere to cells in higher numbers than microspheres coated with native M. smegmatis proteins. The binding of the 19-kDa antigen to cells was inhibited with mannose receptor competitor sugars, Ca 2+ chelators and with a monoclonal antibody to the human mannose receptor. Phagocytosis assays showed high-level binding of bacilli to THP-1 cells that was inhibited with α-methyl-mannoside, mannan, EDTA and mAbs to the mannose receptor and to the 19-kDa M. tuberculosis antigen. Immunoprecipitation, cell-surface ELISA and immunostaining confirmed the expression of the mannose receptor by THP-1 cells. In conclusion, here we show that the macrophage mannose receptor, considered a pathogen pattern recognition receptor, may interact with mannose residues of mycobacterial glycoproteins that could promote the phagocytosis of mycobacteria.