Background

Tuberculosis (TB) spans a spectrum from infection with Mycobacterium tuberculosis (Mtb) to latent and active disease. After inhaling Mtb, individuals may (1) resist infection, (2) develop latent TB that can persist for years, or (3) progress to active TB, typically affecting the lungs (pulmonary TB), though it can spread to other organs.

Macrophages play a dual role in TB—they are both the main site of Mtb replication and key to initiating immune responses. The interaction between Mtb and macrophages influences disease outcomes, but the mechanisms remain only partly understood.

This study investigates the proteomic profiles of Mtb-infected macrophages from individuals with different TB outcomes: infection resisters (RSTR), latent TB (LTBI), and those with prior pulmonary (PTB) or meningeal TB (TBM). We aim to identify distinct protein signatures, especially in phosphorylation and ubiquitylation, that may explain resistance or susceptibility. This observational study may form the foundation for understanding this disease mechanism to improve TB control.

Objective

To determine differential profile changes in host protein abundance and post-translational modifications during Mtb infection in macrophage from 4 groups: previous PTB, previous TBM, LTBI and RSTR
To identify host genetic variants associated with protein abundance.

Methods

We hypothesize that variations in proteomics profiling of macrophages are associated with different forms of TB infection. Because macrophages isolated from active patients with TBM or PTB could be still activated by Mtb infection, we aim to isolate cells from those patients who successfully recovered from the disease. This is a cross-sectional observational study of 100 healthy adults, including 4 groups: resistant to TB infection (referred to as RSTR); latent TB infection (LTBI); individuals with previous PTB (previous PTB); individuals with previous TBM (previous TBM)
PBMC will be isolated from heparin blood using the density gradient centrifugation. Monocytes will be purified from PBMCs and differentiated into monocyte-derived macrophages. The macrophages are infected with media alone or H37Rv Mtb. Then, cells will be lysed, digested with trypsin, and applied subsequent enrichment steps for purification and protein abundance measurement. The peptide samples will go through protein identification and quantification using a state-of-the-art tribrid mass spectrometry system.

Human DNA will be extracted from blood. Genome-wide SNP typing will be performed to identify genetics variants associated with protein abundance.