Lesion-Specific Immune Response in Granulomas of Patients with Pulmonary Tuberculosis: A Pilot Study

Abstract

The formation and maintenance of granulomas is central to the host response to Mycobacterium tuberculosis (Mtb) infection. It is widely accepted that the lungs of patients with tuberculosis (TB) usually contain multiple infection foci, and that the granulomas evolve and differentiate independently, resulting in considerable heterogeneity. Although gene expression profiles of human blood cells have been proposed as biomarkers of Mtb infection and/or active disease, the immune profiles of discrete lesion types has not been studied extensively. Using histology, immunopathology and genome-wide transcriptome analysis, we explored the immunological profile of human lung TB granulomas. We show that although the different granulomas share core similarities in their immunological/inflammatory characteristics, they also exhibit significant divergence. Despite similar numbers of CD68+ macrophages in the different lesions, the extent of immune reactivity, as determined by the density of CD3+ T cells in the macrophage rich areas, and the extent of fibrosis, shows considerable variation. Both quantitative and qualitative differences among significantly differentially expressed genes (SDEG) were noted in each of the lesion types studied. Further, network/pathway analysis of SDEG revealed differential regulation of inflammatory response, immune cell trafficking, and cell mediated immune response in the different lesions. Our data highlight the formidable challenges facing ongoing efforts to identify peripheral blood biomarkers due to the diversity of lesion types and complexity of local immune responses in the lung.

Heterogeneity in tuberculosis

“…Recent studies using both animal models of TB 14,37 and surgically resected tissue from humans with TB 38,39 support these findings and reiterate the inherent complexity of the disease. Importantly, this granuloma-specific heterogeneity is crucial in determining host outcome, as only one or a few granulomas that poorly contain their bacteria are probably responsible for allowing bacterial dissemination, worsening pathology and driving the onset of active disease 37,40–42 .…”

“…In a pilot study that examined lung granulomas from patients with chronic pulmonary TB, Subbian et al 38 found significant variability in the density of T cells and in the extent of fibrosis, which varied in accordance with immune activation and bacterial load. The authors suggested that the observed heterogeneity was at least partly driven by differential immune profiles in individual granuloma microenvironments that reflected the maturation state of the granuloma.…”

Specific Human and Candida Cellular Interactions Lead to Controlled or Persistent Infection Outcomes during Granuloma-Like Formation

“…Moreover, the technical manipulation and isolation of these complex structures were similar to those implemented for mycobacterial in vitro granulomas. Similar models have been useful to investigate and recapitulate other mycobacterial, protozoan, helminthic, and fungal pathophysiologies, for which granuloma formation is a hallmark of pathology (38, 46–52). In a previous work, we have validated an in vitro multicellular interaction model with C.…”

Mutations in Rv2983 as a novel determinant of resistance to nitroimidazole drugs in Mycobacterium tuberculosis

“…In order to study bacterial genetic, host and pharmacological factors associated with emergence of nitroimidazole resistance in vivo, we selected pretomanid-resistant mutants using a wide range of pretomanid doses in two mouse models of TB and characterized them by whole genome sequencing (WGS). Because the lungs of TB patients feature a heterogeneous array of lesion types associated with diversified immune responses and drug penetration (24,25), we used both C3HeB/FeJ mice, which develop caseating lung lesions in response to M. tuberculosis infection, and BALB/c mice, which do not, to investigate the impact of these caseating lesions and their associated micro-environments on mutant selection. In the present study, we found that pretomanid-resistant mutants were readily selected by monotherapy in both mouse strains.…”