title: The glycosylated Rv1860 protein of Mycobacterium tuberculosis inhibits dendritic cell mediated TH1 and TH17 polarization of T cells and abrogates protective immunity conferred by BCG.
abstract: We previously reported interferon gamma secretion by human CD4⁺ and CD8⁺ T cells in response to recombinant E. coli-expressed Rv1860 protein of Mycobacterium tuberculosis (MTB) as well as protection of guinea pigs against a challenge with virulent MTB following prime-boost immunization with DNA vaccine and poxvirus expressing Rv1860. In contrast, a Statens Serum Institute Mycobacterium bovis BCG (BCG-SSI) recombinant expressing MTB Rv1860 (BCG-TB1860) showed loss of protective ability compared to the parent BCG strain expressing the control GFP protein (BCG-GFP). Since Rv1860 is a secreted mannosylated protein of MTB and BCG, we investigated the effect of BCG-TB1860 on innate immunity. Relative to BCG-GFP, BCG-TB1860 effected a significant near total reduction both in secretion of cytokines IL-2, IL-12p40, IL-12p70, TNF-α, IL-6 and IL-10, and up regulation of co-stimulatory molecules MHC-II, CD40, CD54, CD80 and CD86 by infected bone marrow derived dendritic cells (BMDC), while leaving secreted levels of TGF-β unchanged. These effects were mimicked by BCG-TB1860His which carried a 6-Histidine tag at the C-terminus of Rv1860, killed sonicated preparations of BCG-TB1860 and purified H37Rv-derived Rv1860 glycoprotein added to BCG-GFP, but not by E. coli-expressed recombinant Rv1860. Most importantly, BMDC exposed to BCG-TB1860 failed to polarize allogeneic as well as syngeneic T cells to secrete IFN-γ and IL-17 relative to BCG-GFP. Splenocytes from mice infected with BCG-SSI showed significantly less proliferation and secretion of IL-2, IFN-γ and IL-17, but secreted higher levels of IL-10 in response to in vitro restimulation with BCG-TB1860 compared to BCG-GFP. Spleens from mice infected with BCG-TB1860 also harboured significantly fewer DC expressing MHC-II, IL-12, IL-2 and TNF-α compared to mice infected with BCG-GFP. Glycoproteins of MTB, through their deleterious effects on DC may thus contribute to suppress the generation of a TH1- and TH17-dominated adaptive immune response that is vital for protection against tuberculosis.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Vijaya
authors.initials: V
authors.lastname: Satchidanandam
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Naveen
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Rajiv S
authors.initials: RS
authors.lastname: Jumani
authors.affiliation: National Tuberculosis Institute, Bangalore, Karnataka, India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Challu
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Shobha
authors.initials: S
authors.lastname: Elangovan
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Naseem A
authors.initials: NA
authors.lastname: Khan
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D001500:BCG Vaccine / Q000009:adverse effects* / Q000037:antagonists & inhibitors / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000009:adverse effects* / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use; D016764:Cell Polarity; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D005260:Female; D006023:Glycoproteins / Q000009:adverse effects* / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use; D006031:Glycosylation; D007156:Immunologic Memory; D018836:Inflammation Mediators / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D008807:Mice, Inbred BALB C; D009163:Mycobacterium bovis / Q000276:immunology / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000009:adverse effects / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use; D013154:Spleen / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D058504:Th17 Cells / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D014376:Tuberculosis / Q000276:immunology / Q000378:metabolism / Q000382:microbiology / Q000517:prevention & control
chemical_list: D001500:BCG Vaccine; D001426:Bacterial Proteins; D006023:Glycoproteins; D018836:Inflammation Mediators; D011994:Recombinant Proteins