In vitro analysis of antigen induced T cell-monocyte conjugates by imaging flow cytometry

Unraveling the potential of graphene quantum dots against Mycobacterium tuberculosis infection

Introduction

The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) strains has underscored the urgent need for novel therapeutic approaches. Carbon-based nanomaterials, such as graphene oxide (GO), have shown potential in anti-TB activities but suffer from significant toxicity issues.

Methods

This study explores the anti-TB potential of differently functionalized graphene quantum dots (GQDs) - non-functionalized, L-GQDs, aminated (NH2-GQDs), and carboxylated (COOH-GQDs) - alone and in combination with standard TB drugs (isoniazid, amikacin, and linezolid). Their effects were assessed in both axenic cultures and in vitro infection models.

Results

GQDs alone did not demonstrate direct mycobactericidal effects nor trapping activity. However, the combination of NH2-GQDs with amikacin significantly reduced CFUs in in vitro models. NH2-GQDs and COOH-GQDs also enhanced the antimicrobial activity of amikacin in infected macrophages, although L-GQDs and COOH-GQDs alone showed no significant activity.

Discussion

The results suggest that specific types of GQDs, particularly NH2-GQDs, can enhance the efficacy of existing anti-TB drugs. These nanoparticles might serve as effective adjuvants in anti-TB therapy by boosting drug performance and reducing bacterial counts in host cells, highlighting their potential as part of advanced drug delivery systems in tuberculosis treatment. Further investigations are needed to better understand their mechanisms and optimize their use in clinical settings.

Role of Axl in target organ inflammation and damage due to hypertensive aortic remodeling

We have shown that excessive endothelial cell stretch causes release of growth arrest-specific 6 (GAS6), which activates the tyrosine kinase receptor Axl on monocytes and promotes immune activation and inflammation. We hypothesized that GAS6/Axl blockade would reduce renal and vascular inflammation and lessen renal dysfunction in the setting of chronic aortic remodeling. We characterized a model of aortic remodeling in mice following a 2-wk infusion of angiotensin II (ANG II). These mice had chronically increased pulse wave velocity, and their aortas demonstrated increased mural collagen. Mechanical testing revealed a marked loss of Windkessel function that persisted for 6 mo following ANG II infusion. Renal function studies showed a reduced ability to excrete a volume load, a progressive increase in albuminuria, and tubular damage as estimated by periodic acid Schiff staining. Treatment with the Axl inhibitor R428 beginning 2 mo after ANG II infusion had a minimal effect on aortic remodeling 2 mo later but reduced the infiltration of T cells, γ/δ T cells, and macrophages into the aorta and kidney and improved renal excretory capacity, reduced albuminuria, and reduced evidence of renal tubular damage. In humans, circulating Axl+/Siglec6+ dendritic cells and phospho-Axl+ cells correlated with pulse wave velocity and aortic compliance measured by transesophageal echo, confirming chronic activation of the GAS6/Axl pathway. We conclude that brief episodes of hypertension induce chronic aortic remodeling, which is associated with persistent low-grade inflammation of the aorta and kidneys and evidence of renal dysfunction. These events are mediated at least in part by GAS6/Axl signaling and are improved with Axl blockade.NEW & NOTEWORTHY In this study, a brief, 2-wk period of hypertension in mice led to progressive aortic remodeling, an increase in pulse wave velocity, and evidence of renal injury, dysfunction, and albuminuria. This end-organ damage was associated with persistent renal and aortic infiltration of CD8+ and γ/δ T cells. We show that this inflammatory response is likely due to GAS6/Axl signaling and can be ameliorated by blocking this pathway. We propose that the altered microvascular mechanical forces caused by increased pulse wave velocity enhance GAS6 release from the endothelium, which in turn activates Axl on myeloid cells, promoting the end-organ damage associated with aortic stiffening.

High-throughput analysis of T cell-monocyte interaction in human tuberculosis

The lack of efficient tools for identifying immunological correlates of tuberculosis (TB) protection or risk of disease progression impedes the development of improved control strategies. To more clearly understand the host response in TB, we recently established an imaging flow cytometer‐based in‐vitro assay, which assesses multiple aspects of T cell–monocyte interaction. Here, we extended our previous work and characterized communication between T cells and monocytes using clinical samples from individuals with different TB infection status and healthy controls from a TB endemic setting. To identify T cell–monocyte conjugates, peripheral blood mononuclear cells (PBMC) were stimulated with ds‐Red‐expressing Mycobacterium bovis bacille Calmette–Guérin or 6‐kDa early secreted antigenic target (ESAT 6) peptides for 6 h, and analyzed by imaging flow cytometer (IFC). We then enumerated T cell–monocyte conjugates using polarization of T cell receptor (TCR) and F‐actin as markers for synapse formation, and nuclear factor kappa B (NF‐κB) nuclear translocation in the T cells. We observed a reduced frequency of T cell–monocyte conjugates in cells from patients with active pulmonary tuberculosis (pTB) compared to latent TB‐infected (LTBI) and healthy controls. When we monitored NF‐κB nuclear translocation in T cells interacting with monocytes, the proportion of responding cells was significantly higher in active pTB compared with LTBI and controls. Overall, these data underscore the need to consider multiple immunological parameters against TB, where IFC could be a valuable tool.