title: Mycobacterium bovis bacillus Calmette-Guérin secreting active cathepsin S stimulates expression of mature MHC class II molecules and antigen presentation in human macrophages.
abstract: A successful Th cell response to bacterial infections is induced by mature MHC class II molecules presenting specific Ag peptides on the surface of macrophages. In recent studies, we demonstrated that infection with the conventional vaccine Mycobacterium bovis bacillus Calmette-Guérin (BCG) specifically blocks the surface export of mature class II molecules in human macrophages by a mechanism dependent on inhibition of cathepsin S (Cat S) expression. The present study examined class II expression in macrophages infected with a rBCG strain engineered to express and secrete biologically active human Cat S (rBCG-hcs). Cat S activity was completely restored in cells ingesting rBCG-hcs, which secreted substantial levels of Cat S intracellularly. Thus, infection with rBCG-hcs, but not parental BCG, restored surface expression of mature MHC class II molecules in response to IFN-gamma, presumably as result of MHC class II invariant chain degradation dependent on active Cat S secreted by the bacterium. These events correlated with increased class II-directed presentation of mycobacterial Ag85B to a specific CD4(+) T cell hybridoma by rBCG-hcs-infected macrophages. Consistent with these findings, rBCG-hcs was found to accelerate the fusion of its phagosome with lysosomes, a process that optimizes Ag processing in infected macrophages. These data demonstrated that intracellular restoration of Cat S activity improves the capacity of BCG-infected macrophages to stimulate CD4(+) Th cells. Given that Th cells play a major role in protection against tuberculosis, rBCG-hcs would be a valuable tuberculosis vaccine candidate.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, University of British Columbia and Vancouver Costal Health Institute, Vancouver, British Columbia, Canada.
authors.forename: Hafid
authors.initials: H
authors.lastname: Soualhine
authors.forename: Ala-Eddine
authors.initials: AE
authors.lastname: Deghmane
authors.forename: Jim
authors.initials: J
authors.lastname: Sun
authors.forename: Karen
authors.initials: K
authors.lastname: Mak
authors.forename: Amina
authors.initials: A
authors.lastname: Talal
authors.forename: Yossef
authors.initials: Y
authors.lastname: Av-Gay
authors.forename: Zakaria
authors.initials: Z
authors.lastname: Hmama
mesh_terms: D000217:Acyltransferases / Q000276:immunology / Q000378:metabolism; D017951:Antigen Presentation / Q000235:genetics / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism; D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism; D002403:Cathepsins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000276:immunology*; D005818:Genetic Engineering; D006681:HLA-D Antigens / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D032581:Tuberculosis Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D006681:HLA-D Antigens; D011994:Recombinant Proteins; D032581:Tuberculosis Vaccines; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis; D002403:Cathepsins; C028217:cathepsin S