title: 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.
abstract: 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 alpha-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.
authors.affiliation: Departamento de Inmunologia, Instituto de Investigaciones Biomedicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-228, 04510 Mexico, DF, Mexico.
authors.forename: Hugo
authors.initials: H
authors.lastname: Diaz-Silvestre
authors.forename: Patricia
authors.initials: P
authors.lastname: Espinosa-Cueto
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sanchez-Gonzalez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Esparza-Ceron
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Pereira-Suarez
authors.forename: German
authors.initials: G
authors.lastname: Bernal-Fernandez
authors.forename: Clara
authors.initials: C
authors.lastname: Espitia
authors.forename: Raul
authors.initials: R
authors.lastname: Mancilla
mesh_terms: D000117:Acetylglucosamine / Q000494:pharmacology; D018829:Adhesins, Bacterial / Q000276:immunology* / Q000378:metabolism; D000942:Antigens, Bacterial / Q000276:immunology; D001422:Bacterial Adhesion; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D037181:Lectins, C-Type / Q000276:immunology* / Q000378:metabolism; D008351:Mannans / Q000494:pharmacology; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000276:immunology* / Q000378:metabolism; D008766:Methylmannosides / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000378:metabolism; D010587:Phagocytosis / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D011956:Receptors, Cell Surface / Q000276:immunology* / Q000378:metabolism; D014376:Tuberculosis / Q000382:microbiology*
chemical_list: D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D037181:Lectins, C-Type; D008351:Mannans; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008766:Methylmannosides; D011956:Receptors, Cell Surface; C008466:methylmannoside; D000117:Acetylglucosamine