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PPE57 induces activation of macrophages and drives Th1-type immune responses through TLR2

Ying Xu1, Enzhuo Yang, Qi Huang

  • 1State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Science, Fudan University, No. 220 Handan Road, Shanghai, 200433, China, yingxu2520@fudan.edu.cn.

Journal of Molecular Medicine (Berlin, Germany)
|January 15, 2015
PubMed
Abstract

Insights

The Mycobacterium tuberculosis PPE57 protein enhances bacterial entry into macrophages by interacting with Toll-like receptor 2 (TLR2). This interaction activates macrophages and promotes a Th1 immune response, suggesting PPE57 as a potential vaccine antigen.

Area of Science:

  • Immunology
  • Microbiology
  • Vaccinology

Background:

  • Proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) proteins are unique to Mycobacteria and modulate innate immune pathways.
  • The PPE57 protein is a cell wall-associated protein found on the surface of Mycobacterium species.

Purpose of the Study:

  • To investigate the role of PPE57 in host-pathogen interactions and immune response modulation.
  • To elucidate the mechanism by which PPE57 influences macrophage function and T cell polarization.
  • To evaluate the potential of PPE57 as a vaccine candidate against Mycobacterium tuberculosis.

Main Methods:

  • Cell surface localization and expression analysis of PPE57.
  • Macrophage infection assays to assess bacterial entry and phagocytosis.
  • Flow cytometry and cytokine analysis to evaluate macrophage activation markers and inflammatory responses.
  • T cell polarization assays (in vitro and in vivo) to measure cytokine secretion and cell surface marker expression.
  • Immunization studies using recombinant Bacillus Calmette-Guérin (BCG) overexpressing PPE57.

Main Results:

  • PPE57 is located on the mycobacterial cell surface and enhances bacterial entry into macrophages.
  • PPE57 directly interacts with Toll-like receptor 2 (TLR2) on macrophages, leading to macrophage activation.
  • PPE57 upregulates key cell surface molecules (CD40, CD80, CD86, MHC class II) and pro-inflammatory cytokines (TNF-α, IL-6, IL-12p40) in a TLR2-dependent manner.
  • PPE57 promotes Th1 polarization by inducing interferon-γ and IL-2 secretion and CXCR3 expression in T cells.
  • Recombinant BCG overexpressing PPE57 demonstrated enhanced protective efficacy against M. tuberculosis challenge compared to control BCG.

Conclusions:

  • PPE57 is a cell surface protein that enhances M. tuberculosis entry into macrophages via TLR2 interaction.
  • PPE57 plays a critical role in TLR2-mediated macrophage activation and subsequent Th1 immune response induction.
  • PPE57 is a promising antigen for the development of novel vaccines against tuberculosis.

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