A DNA methylome biosignature in alveolar macrophages from TB-exposed individuals predicts exposure to mycobacteria

Several studies have identified biomarkers for tuberculosis (TB) diagnosis based on blood cell transcriptomics. Here, we instead studied epigenomics in the lung compartment by obtaining induced sputum from subjects included in a TB contact tracing. CD3- and HLA-DR-positive cells were isolated from the collected sputum and DNA methylome analyses performed. Unsupervised cluster analysis revealed that DNA methylomes of cells from TB-exposed individuals and controls appeared as separate clusters and the numerous genes that were differentially methylated were functionally connected. The enriched pathways were strongly correlated to data from published work on protective heterologous immunity to TB. Taken together, our results demonstrate that epigenetic changes related to trained immunity occurs in the pulmonary immune cells of TB-exposed individuals and that a DNA methylation signature can be derived from the DNA methylome. Such a signature can be further developed for clinical use as a marker of TB exposure.