Biology subjects

Monteith, A. J.

Publications and source records attributed to Monteith, A. J..

9 recordsLinked to original sources

bioRxiv2026

Preserving Nanotherapy-Induced Allogeneic Murine Islet Graft Tolerance During Distal Methicillin-Resistant Staphylococcus aureus Skin Infection

Eliminating lifelong immunosuppression can make islet transplantation a durable alternative to insulin therapy for type 1 diabetes. As short-course tolerogenic regimens are developed to replace lifelong immunosuppression, it is critical to test their robustness against perturbations such as hospital-acquired infections, which transplant recipients routinely encounter. Herein, we investigated whether rapamycin-loaded polymersomes (rPS), a subcutaneous nanotherapy that induces long-term murine islet allograft survival, can preserve host defenses in a Methicillin-resistant Staphylococcus aureus (MRSA) skin infection, and whether the resulting immune response from this distal infection relative to graft location erodes rPS-induced tolerance. rPS maintained neutrophil antibacterial activity despite inhibiting oxidative mechanisms in vitro, and rPS-treated mice demonstrated normal recovery following MRSA challenge. However, MRSA skin infection caused a decline of ~43% in recipient survival for rPS-treated mice, despite surviving recipients retaining glucose-stimulated insulin responsiveness. This erosion of allograft acceptance coincided with a burst of IL-6 within 24h of the infection followed by elevated TNF-[a] and neutrophilia at 13 days post-infection. Combining rPS with a single dose of methylprednisolone reduced IL-6 and TNF- without altering neutrophilia, nearly doubling survival among infected recipients to 80%. Our findings demonstrate that partial dampening of inflammatory insults can restore superior islet allograft acceptance following perioperative infection.

bioengineering↗

bioRxiv2026

Efficient colonic colonization by Campylobacter jejuni requires the heme receptor ChuA

Previous research demonstrated that Campylobacter jejuni encodes a heme utilization system that facilitates heme-dependent growth under iron-limiting conditions and that transcription of this system is induced during human infection. Despite these observations, it remained unknown whether the heme transport system is required for colonization and disease in a susceptible host. To address this, we created individual non-polar deletion mutants of each component of the heme transport system and examined their ability to promote heme-dependent growth and iron uptake. From this work, we found that only the heme receptor, ChuA, was required for heme-dependent growth and iron acquisition, which supports the earlier work of another group. Further, we examined whether intestinal colonization, immune activation, and pathology were altered during infection with these mutants. After establishing that elevated heme and chuABCD expression occur during C. jejuni infection of IL-10-/- mice, we found that a mutant of the heme receptor, ChuA, exhibited significantly reduced colonization of the colon. In addition, we found that neutrophil and circulating monocyte recruitment were significantly reduced in the colon during infection with the ChuA mutant, but that populations of self-maintaining tissue macrophages remained high. Loss of ChuA reduced colonic colonization and was accompanied by diminished innate immune cell recruitment and intestinal pathology. Together, these findings identify ChuA-dependent heme acquisition as a key determinant of efficient colonic colonization and the associated inflammatory disease.

microbiology↗

bioRxiv2026

Specific F1 ATP synthase inhibition delivers transient mitochondrial stress for selective targeting of acute myeloid leukemia

Targeting oxidative phosphorylation (OXPHOS) represents an attractive therapeutic strategy in acute myeloid leukemia, which exhibits exceptional dependence on mitochondrial respiration compared to normal hematopoietic cells. However, clinical attempts to exploit this vulnerability have been limited by on-target toxicity to healthy tissue. Here, we comprehensively compare the cellular consequences of inhibiting distinct nodes of the electron transport chain in AML. We demonstrate that selective inhibition of the F1 subunit of ATP synthase with EB2023 (ammocidin A) delivers an energetic stress to AML cells without the profound redox stress that characterizes complex I inhibition, preventing NAD/NADH imbalance and allowing continued TCA cycling. Further, the duration of OXPHOS inhibition is transient in nature in vivo, a finding revealed through pharmacokinetic and serial pharmacodynamic monitoring of AMPK phosphorylation accompanied by OPA1-mediated mitochondrial structural remodeling that primes AML cells for BCL2 inhibitor synergy. EB2023 in combination with venetoclax demonstrates potent anti-AML activity across cell lines and patient-derived xenograft models at doses that spare normal hematopoietic progenitors and avoid the neuropathy and sustained detrimental systemic metabolic rewiring in healthy tissues associated with prior efforts to target OXPHOS. These findings establish F1-selective ATP synthase inhibition as a clinically actionable therapeutic strategy in AML and establish the duration of OXPHOS inhibition as a critical and previously underappreciated determinant of therapeutic index.

cancer biology↗

bioRxiv2026

Neutrophils rapidly release nucleoli-stored IFNα during infection

Type I interferons (IFN-I) are critical for antiviral defense but can drive severe pathology when dysregulated. Excess IFN-I is associated with prominent neutrophil accumulation; however, the contribution of neutrophils to IFN-I overproduction remains underexplored. In all cell types previously studied, IFN-I is synthesized de novo following sensing of microbial or host-derived inflammatory stimuli. Contrary to this paradigm, we find that neutrophils express IFN during development and store it in the nucleolus, a membrane-less intranuclear condensate classically functioning in ribosome biogenesis. TLR-mediated bacterial sensing induces a nucleolar stress response in neutrophils that triggers rapid release of nucleoli-stored IFN independent of de novo protein synthesis. These findings reveal that neutrophils have repurposed the nucleolus as a cytokine storage and secretory organelle, identify the first naturally occurring immunoregulatory function of nucleolar stress, and provide insight into the relationship between detrimental IFN-I levels and neutrophil accumulation.

immunology↗

bioRxiv2026

Reduced late endosome/lysosome function promotes SLE through chronic PI3k activity and SHP-1/SHIP-1 defects

Degradation of cellular waste from phagocytosis, endocytosis and autophagy occurs through hydrolases that become activated during acidification of late endosomes and lysosomes (LELs). In a cross-sectional study we show diminished LEL acidification and the accumulation of surface-bound nucleosome on monocytes, dendritic cells, and B cells from SLE patients. Diminished acidification and exocytosis of undegraded IgG-ICs is evident in active, but not inactive disease. This is supported by our murine study where LEL acidification is diminished, promoting exocytosis and the accumulation of cell surface IgG-immune complexes. Mechanistically, LEL dysfunction is induced by chronic PI3k activation in lupus-prone MRL/lpr mice. We also show that on a non-autoimmune C57BL/6 background, deficiency in SHP-1 and inhibition of SHIP-1 activity is sufficient to recapitulate LEL dysfunction found in MRL/lpr mice. Non-acidic LELs are evident in 67% of patients, and associate with SLEDAI arthritis, rash, and nephritis. The high frequency of LEL dysfunction in SLE suggests it could serve as a biomarker identifying a specific disease endotype.

immunology↗

bioRxiv2025

Activation of the Spx redox sensor counters cysteine-driven Fe(II) depletion under disulfide stress

In many low G+C Gram-positive bacteria, the global regulator Spx helps maintain thiol homeostasis during disulfide stress, when protein thiols form aberrant disulfide bonds that can lead to misfolding and oxidative damage. Spx-dependent gene expression is triggered when an intramolecular disulfide bond forms between two cysteines in its redox switch. Surprisingly, some Spx functions persist even in the absence of an active redox switch, highlighting the need to better understand the physiological significance of maintaining this regulatory feature. Here, we utilize a spxC10A mutant that encodes a redox-insensitive Spx variant to study the role of the Spx redox switch in Staphylococcus aureus. We show that the spxC10A mutant is hypersensitive to diamide-induced disulfide stress and exhibits widespread transcriptional dysregulation of genes that contribute to thiol maintenance and disulfide repair. Remarkably, the spxC10A mutant rapidly adapts to disulfide stress by increasing its intracellular pool of L-cysteine (L-Cys) through enhanced uptake, which helps restore a reduced intracellular environment. However, during this process increased L-Cys inadvertently depletes cytosolic Fe(II), leading to growth inhibition of the spxC10A mutant. Finally, we show that the Spx-dependent control of intracellular L-Cys is critical for S. aureus survival when it encounters human neutrophils. Overall, these findings suggest that staphylococcal adaptation to disulfide stress through intracellular L-Cys accumulation imposes significant fitness costs that S. aureus overcomes by rapid regulatory control of thiol homeostasis through a functional Spx redox switch. SignificanceAll cells have a pool of low molecular weight thiols, such as cysteine, glutathione, bacillithiol, and coenzyme A, to maintain redox balance under oxidative and disulfide stress. Among these, cysteine is a very effective thiol but is highly reactive, and its intracellular concentration must be tightly regulated. In S. aureus, we found that cysteine accumulates intracellularly during disulfide stress and if left unchecked, can inadvertently deplete cytosolic Fe(II), leading to growth inhibition. To prevent cysteine toxicity, S. aureus activates the global regulator Spx, which rapidly induces genes that restore thiol homeostasis and limits cysteine accumulation.

microbiology↗

bioRxiv2025

A TLR7/9-IFNα-LDHB axis drives vital NET release and compromises antibacterial defense.

Patients with systemic lupus erythematosus (SLE) are susceptible to bacterial infections, but the underlying dysfunction remains unclear. We found that Staphylococcus aureus triggers mitochondria-dependent suicidal NETosis via lactate sensing in healthy neutrophils, but this response is defective in SLE. Herein, we show that chronic Toll-like receptor (TLR) 7/9 signaling represses mitochondrial lactate dehydrogenase B (LDHB), thereby impairing lactate sensing and downstream suicidal NETosis. Instead, SLE neutrophils default to vital NET release; a less bactericidal, type I interferon (IFN)-driven process amplified by staphylococcal pore-forming toxins and sustained by elevated systemic IFN levels observed in SLE. Combined treatment with hydroxychloroquine (HCQ) and interferon-alpha/beta receptor (IFNAR) blockade restores LDHB expression, NET homeostasis, and bacterial clearance in lupus-prone mice. Neutrophils from SLE patients exhibit similar defects, which are reversed by HCQ and the IFNAR-blocking antibody anifrolumab. These findings identify a clinically actionable immunometabolic checkpoint linking chronic autoimmune signaling to defective antibacterial defense in SLE.

immunology↗

bioRxiv2025

Efficient gastrointestinal colonization by Campylobacter jejuni requires components of the ChuABCD heme transport system

Previous research demonstrated that Campylobacter jejuni encodes a heme utilization system that facilitates heme-dependent growth under iron-limiting conditions and that transcription of this system is induced during human infection. Despite these observations, it remained unknown whether the heme transport system is required for colonization and disease in a susceptible host. To address this, we created individual non-polar deletion mutants of each component of the heme transport system, as well as a total deletion of the inner membrane transporter, ChuBCD, and examined their ability to promote heme-dependent growth and iron uptake. From this work, we found that only the heme receptor, ChuA, was required for heme-dependent growth and iron acquisition, which supports earlier work of another group. Further, we examined whether intestinal colonization, immune activation, and pathology were altered during infection with these mutants. After establishing that elevated heme and chuABCD expression occurs during C. jejuni infection of IL-10-/- mice, we found that heme transport mutants exhibited significantly reduced fecal shedding and colonization of the cecum and colon. In addition, we found that neutrophil and macrophage recruitment and intestinal pathology often remained intermediately elevated despite decreased bacterial loads. These results suggest that heme utilization promotes efficient colonization and full pathogenicity in C. jejuni, but that neither is completely abrogated in its absence.

microbiology↗

bioRxiv2020

Spatially-targeted proteomics of the host-pathogen interface during staphylococcal abscess formation

Staphylococcus aureus is a common cause of invasive and life-threatening infections that are often multi-drug resistant. To develop novel treatment approaches, a detailed understanding of the complex host-pathogen interactions during infection is essential. This is particularly true for the molecular processes that govern the formation of tissue abscesses, as these heterogeneous structures are important contributors to staphylococcal pathogenicity. To fully characterize the developmental process leading to mature abscesses, temporal and spatial analytical approaches are required. Spatially targeted proteomic technologies, such as micro liquid extraction surface analysis, offer insight into complex biological systems including detection of bacterial proteins, and their abundance in the host environment. By analyzing the proteomic constituents of different abscess regions across the course of infection, we defined the immune response and bacterial contribution to abscess development through spatial and temporal proteomic assessment. The information gathered was mapped to biochemical pathways to characterize the metabolic processes and immune strategies employed by the host. These data provide insights into the physiological state of bacteria within abscesses and elucidate pathogenic processes at the host-pathogen interface.

microbiology↗