Biology subjects

Nargan, K.

Publications and source records attributed to Nargan, K..

3 recordsLinked to original sources

bioRxiv2021

Aggregated Mycobacterium tuberculosis enhances the inflammatory response

Mycobacterium tuberculosis (Mtb) readily aggregates in culture and Mtb aggregates in the lung were observed in experimental Mtb infection. However, the physiological consequences of Mtb aggregation are incompletely understood. Here we examined the human macrophage transcriptional response to aggregated Mtb relative to infection with non-aggregated single or multiple bacilli per host cell. Infection with aggregated Mtb led to an early upregulation of pro-inflammatory associated genes and enhanced TNF signaling via the NF{kappa}B pathway. Both these pathways were significantly upregulated relative to infection with single bacilli, and TNF signaling was also significantly elevated relative to infection with multiple non-aggregated Mtb. Secretion of TNF and downstream cytokines were also enhanced. On a longer timescale, aggregate infection led to overall increased acidification per macrophage and a high proportion of death in these cells after aggregate phagocytosis. Host cell death did not occur when Mtb aggregates were heat killed despite such clumps being readily picked up. To validate that Mtb aggregates do occur in the human lung, we document Mtb aggregates surrounding a cavity in a human TB lesion. Aggregates may therefore be present in some lesions and elicit a stronger inflammatory response resulting in recruitment of additional phagocytes and their subsequent death, potentially leading to necrosis and transmission.

microbiology↗

bioRxiv2020

Single-cell profiling of tuberculosis lung granulomas reveals functional lymphocyte signatures of bacterial control

Mycobacterium tuberculosis lung infection results in a complex multicellular structure, the granuloma. In some granulomas, immune activity promotes bacterial clearance; in others, bacteria persist and grow. We identified correlates of bacterial control in cynomolgus macaque lung granulomas by co-registering longitudinal PET-CT imaging, single-cell RNA-sequencing, and measures of bacterial clearance. We find that bacterial persistence occurs in granulomas enriched for mast, endothelial, fibroblast and plasma cells, signaling amongst themselves via Type II immunity and wound healing pathways. In contrast, these interactions are largely absent in granulomas that drive bacterial control, which are often those that form later in the course of infection; these restrictive lesions are characterized by cellular ecosystems enriched for Type1-Type17, stem-like, and cytotoxic T cells engaged in pro-inflammatory signaling networks that involve diverse myeloid and non-immune cell populations. There is also a temporal aspect to bacterial control, in that granulomas that arise later in infection (in the context of an established immune response) share the functional characteristics of restrictive granulomas and are more capable of killing Mtb. Taken together, our results define the complex multicellular ecosystems underlying (lack of) granuloma resolution and highlight host immune targets that can be leveraged to develop new vaccine and therapeutic strategies for TB. One-Sentence SummaryBacterial control in TB lung granulomas correlates with distinct cellular immune microenvironments and time of formation after infection.

immunology↗

bioRxiv2020

3D microarchitecture of the human tuberculous granuloma

Our current understanding of the pathophysiology of human pulmonary TB is limited by the paucity of human TB lung tissue for study and reliance on 2D analytical methods. Here, to overcome the limitations of conventional 2D histopathology, we used high-resolution 3D X-ray imaging ({micro}CT/nCT) to characterize necrotic lesions within human tuberculous lung tissues in relation to the airways and vasculature. We observed marked heterogeneity in the 3D structure and volume of lesions. Also, 3D imaging of large human TB lung sections provides unanticipated new insight into the spatial organization of TB lesions in relation to airways and the vascular system. Contrary to the current dogma depicting granulomas as simple spherical structures, we show that TB lesions exhibit complex, cylindrical, branched-type morphologies, which are connected to, and shaped by, the small airways. Our results highlight the likelihood that a single structurally complex lesion could be wrongly viewed as multiple independent lesions when evaluated in 2D. These findings have strong implications for understanding the pathophysiology and evolution of TB disease and suggest that aerosolized drug delivery strategies for TB should be reconsidered.

microbiology↗