Biology subjects

Machelart, A.

Publications and source records attributed to Machelart, A..

7 recordsLinked to original sources

bioRxiv2026

Galectin-3 recruitment at the Mycobacterium tuberculosis-containing phagosome is critical in macrophage but dispensable in epithelial cells

Mycobacterium tuberculosis (Mtb) virulence relies in part on its ability to induce phagosomal membrane rupture, enabling bacterial access to the host cell cytosol. This process is largely mediated by the ESX-1 secretion system, which is present in Mtb but absent from the vaccine strain BCG. Galectin-3 (Gal3), a {beta}-galactoside-binding lectin, is recruited to damaged endomembranes and functions as a cytosolic sensor of membrane disruption. However, the kinetics and quantitative features of Gal3 recruitment to Mtb-containing vacuoles have remained poorly characterized. Here, we performed a longitudinal quantitative imaging study of Gal3 recruitment in human macrophages over a five-day infection period. Gal3 was recruited to mycobacteria-containing vacuoles shortly after infection with both live and heat-killed Mtb. Differences between the two conditions emerged from day 1 post-infection and persisted until macrophage death. A similar kinetic profile was observed with recombinant BCG::ESX-1, whereas parental BCG failed to induce Gal3 recruitment, confirming the requirement for ESX-1-dependent membrane damage. Cytoplasmic Gal3 levels were higher in bystander macrophages than in infected cells and were comparable to non-infected controls, suggesting that diffuse cytoplasmic Gal3 is associated with cells lacking intracellular mycobacteria. Functional studies revealed that Gal3 silencing enhanced long-term intracellular Mtb replication, demonstrating a role for Gal3 in restricting bacterial growth. Importantly, Gal3 recruitment was not observed in alveolar epithelial cells. This cell-type specificity was confirmed in a microfluidic alveolus-on-chip model. Together, these findings identify sustained Gal3 recruitment to the mycobacteria-containing vacuole as a robust quantitative marker of ESX-1-dependent phagosomal rupture and Mtb virulence.

microbiology↗

bioRxiv2025

Cis-aconitate therapy protects against influenza mortality by dual targeting of viral polymerase and ERK/AKT/NF-κB signaling

Influenza virus poses a significant global health challenge, causing approximately 500,000 deaths annually. Its ability to evade antiviral treatments and vaccine-induced immunity underscores the need for novel therapeutic approaches. Our study identifies cis-aconitate (cis-aco), a mitochondria-derived metabolite, as a potent dual-action agent against influenza, independently of its metabolic derivative, itaconate. Cis-aco impairs viral polymerase activity, suppressing viral mRNA expression and protein synthesis to inhibit replication across a range of influenza subtypes. This antiviral efficacy is confirmed in ex vivo human airway and lung organotypic models. Beyond its antiviral properties, cis-aco exhibits potent anti-inflammatory effects, disrupting key inflammatory cascades and reducing the secretion of inflammatory mediators. In a mouse model of influenza pneumonia, cis-aco mitigates viral replication, inflammation, and immune cell activation, significantly improving survival. Notably, its efficacy persists even when administered at later stages of infection, when oseltamivir/Tamiflu(R) is no longer effective. These findings position cis-aco as a promising influenza treatment, combining antiviral and anti-inflammatory benefits within a clinically relevant timeframe.

immunology↗

bioRxiv2025

Mycobacterium tuberculosis-infected macrophages accumulate more nanoparticles

In response to the escalating threat of infectious diseases and the widespread emergence of antimicrobial-resistant strains, novel therapeutic strategies are being actively developed. Nanoparticle-based delivery systems have emerged as promising tools to improve the targeted administration of antimicrobials directly to sites of infection. In the context of pulmonary infections, aerosolized nanocarriers can enhance local biodistribution while minimizing systemic exposure and associated side effects. In this study, we demonstrate that following pulmonary administration in Mycobacterium tuberculosis-infected mice, poly(lactic-co-glycolic acid) (PLGA) nanoparticles are broadly distributed throughout the lungs and preferentially interact with alveolar macrophages--the primary host cells of the pathogen. Remarkably, infected macrophages internalize significantly more nanoparticles than uninfected cells independently of the virulence and viability of the bacteria. Using transcriptomic analysis, we uncovered a list of 21 commonly modulated genes that may be responsible for this phenotype. Collectively, our findings reveal a striking feature of nanoparticles: their capacity to selectively accumulate in infected cells, offering a powerful mechanism to enhance antimicrobial delivery precisely where it is most needed.

cell biology↗

bioRxiv2024

Integrative metagenomics and metabolomics reveal age-associated gut microbiota and metabolite alterations in experimental COVID-19

Aging is a key contributor of morbidity and mortality during acute viral pneumonia. The potential role of age-associated dysbiosis on disease outcomes is still elusive. In the current study, we used high-resolution shotgun metagenomics and targeted metabolomics to characterize SARS-CoV-2-associated changes in the gut microbiota from young (2-month-old) and aged (22-month-old) hamsters, a valuable model of COVID-19. We show that age-related dysfunctions in the gut microbiota are linked to disease severity and long-term sequelae in older hamsters. Our data also reveal age-specific changes in the composition and metabolic activity of the gut microbiota during both the acute phase (day 7 post-infection, D7) and the recovery phase (D22) of infection. Aged hamsters exhibited the most notable shifts in gut microbiota composition and plasma metabolic profiles. Through an integrative analysis of metagenomics, metabolomics, and clinical data, we identified significant associations between bacterial taxa, metabolites and disease markers in the aged group. On D7 (high viral load and lung epithelial damage) and D22 (body weight loss and fibrosis), numerous amino acids, amino acid-related molecules, and indole derivatives were found to correlate with disease markers. In particular, a persistent decrease in phenylalanine, tryptophan, glutamic acid, and indoleacetic acid in aged animals positively correlated with poor recovery of body weight and/or lung fibrosis by D22. In younger hamsters, several bacterial taxa (Eubacterium, Oscillospiraceae, Lawsonibacter) and plasma metabolites (carnosine and cis-aconitic acid) were associated with mild disease outcomes. These findings support the need for age-specific microbiome-targeting strategies to more effectively manage acute viral pneumonia and long-term disease outcomes.

immunology↗

bioRxiv2021

A screening pipeline identifies a broad-spectrum inhibitor of bacterial AB toxins with cross protection against influenza A virus H1N1 and SARS-CoV-2

A challenge for the development of host-targeted anti-infectives against a large spectrum of AB-like toxin-producing bacteria encompasses the identification of chemical compounds corrupting toxin transport through both endolysosomal and retrograde pathways. Here, we performed a high-throughput screening of small chemical compounds blocking active Rac1 proteasomal degradation triggered by the Cytotoxic Necrotizing Factor-1 (CNF1) toxin, followed by orthogonal screens against two AB toxins hijacking defined endolysosomal (Diphtheria toxin) or retrograde (Shiga-like toxin 1) pathways to intoxicate cells. This led to the identification of the molecule N-(3,3-diphenylpropyl)-1-propyl-4-piperidinamine, referred to as C910. This compound induces the swelling of EEA1-positive early endosomes, in absence of PIKfyve kinase inhibition, and disturbs the trafficking of CNF1 and the B-subunit of Shiga toxin along the endolysosomal or retrograde pathways, respectively. Together, we show that C910 protects cells against 8 bacterial AB toxins including large clostridial glucosylating toxins from Clostridium difficile. Of interest, C910 also reduced viral infection in vitro including influenza A virus subtype H1N1 and SARS-CoV-2. Moreover, parenteral administration of C910 to the mice resulted in its accumulation in lung tissues and reduced lethal influenza infection.

microbiology↗

bioRxiv2021

Large scale screening discovers clofoctol as an inhibitor of SARS-CoV-2 replication that reduces COVID-19-like pathology

Drug repurposing has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to favorable safety profile and pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC50 measured against SARS-CoV-2 in human pulmonary cells. This compound inhibits SARS-CoV-2 at a post-entry step. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and lowered pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients. SummaryAntivirals targeting SARS-CoV-2 are sorely needed. In this study, we screened a library of drug compounds and identified clofoctol as an antiviral against SARS-CoV-2. We further demonstrated that, in vivo, this compound reduces inflammatory gene expression and lowers pulmonary pathology.

microbiology↗

bioRxiv2019

IRG1 controls immunometabolic host response and restricts intracellular Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb), the pathogen causing human tuberculosis, has evolved multiple strategies to successfully prevent clearance by immune cells and to establish dissemination and long-term survival in the host. The modulation of host immunity to maximize pathogen elimination while minimizing inflammation-mediated tissue damage may provide another tool to fight drug-resistant Mtb strains. Metabolic reprogramming of phagocytes can dramatically influence the intracellular colonization by Mtb and the key players involved in this process remain a matter of debate. Here, we demonstrate that aconitate decarboxylase 1 (Acod1; also known as immune-responsive gene 1, IRG1), which converts cis-aconitate into the metabolite itaconate, is a major player in controlling the acute phase of Mtb infection. Exposure of IRG1-deficient mice to a virulent Mtb strain (H37Rv) was lethal, while M. bovis BCG and the H37Ra attenuated Mtb strain induced neither lethality nor severe lung immunopathology. Lungs of IRG1-deficient mice infected by Mtb H37Rv displayed large areas of necrotizing granulomatous inflammation and neutrophil infiltration, accompanied by reduced levels of B and T lymphocytes and increased levels of alveolar and interstitial macrophage populations, compared to their wild type counterparts. Next, we show that IRG1, beyond its recruitment to Mtb-containing vacuoles, restricts Mtb replication and lipid droplets accumulation in phagocytes, hallmarks of a tight interplay between the bacillus and the host. Altogether, IRG1 confines the host response to create a favourable phagocytic environment for Mtb controlled intracellular replication.

immunology↗