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

PLoS Pathog. 2014 Jun 12;10(6):e1004176. doi: 10.1371/journal.ppat.1004176. eCollection 2014 Jun.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptive Immunity*
  • Animals
  • BCG Vaccine / adverse effects*
  • BCG Vaccine / antagonists & inhibitors
  • BCG Vaccine / therapeutic use
  • Bacterial Proteins / adverse effects*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Bacterial Proteins / therapeutic use
  • Cell Polarity
  • Cells, Cultured
  • Dendritic Cells / immunology*
  • Dendritic Cells / metabolism
  • Dendritic Cells / microbiology
  • Female
  • Glycoproteins / adverse effects*
  • Glycoproteins / genetics
  • Glycoproteins / metabolism
  • Glycoproteins / therapeutic use
  • Glycosylation
  • Immunologic Memory*
  • Inflammation Mediators / metabolism
  • Macrophages, Peritoneal / immunology
  • Macrophages, Peritoneal / metabolism
  • Macrophages, Peritoneal / microbiology
  • Mice, Inbred BALB C
  • Mycobacterium bovis / immunology
  • Mycobacterium bovis / metabolism
  • Mycobacterium tuberculosis / immunology*
  • Mycobacterium tuberculosis / metabolism
  • Protein Processing, Post-Translational
  • Recombinant Proteins / adverse effects
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / therapeutic use
  • Spleen / immunology
  • Spleen / metabolism
  • Spleen / microbiology
  • Th1 Cells / immunology
  • Th1 Cells / metabolism
  • Th1 Cells / microbiology
  • Th17 Cells / immunology
  • Th17 Cells / metabolism
  • Th17 Cells / microbiology
  • Tuberculosis / immunology
  • Tuberculosis / metabolism
  • Tuberculosis / microbiology
  • Tuberculosis / prevention & control

Substances

  • BCG Vaccine
  • Bacterial Proteins
  • Glycoproteins
  • Inflammation Mediators
  • Recombinant Proteins

Grant support

This work was supported by grant number BT/PR7240/INF/22/52/2006 from Department of Biotechnology, Ministry of Science and Technology, Government of India. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.