Biology subjects

Ochoa, M. T.

Publications and source records attributed to Ochoa, M. T..

4 recordsLinked to original sources

bioRxiv2026

CD1a-Mediated Presentation of Canonical Microbial Peptides to T Cells

Langerhans cells express the nonpolymorphic antigen-presenting molecule CD1a, positioning them as contributors to host immunity against Mycobacterium leprae in human leprosy. CD1a was originally shown to present non-canonical lipopeptide antigens such as dideoxymycobactin and chemically diverse hydrophobic ligands. Here, we generated CD4 T cell lines from leprosy lesions that recognized M. leprae in a CD1a-restricted manner. Unexpectedly, antigen recognition was protease-sensitive, prompting biochemical purification that identified two microbial protein antigens: LppX, a 25-kDa lipoglycoprotein, and Ag85A, a 30-kDa secreted protein with no known lipid modification. Recombinant proteins activated the corresponding T cell lines in a CD1a-dependent manner. Epitope mapping identified 12-mer peptides that fully reconstituted antigenicity, were conserved between M. leprae and M. tuberculosis, and elicited robust, dose-dependent IFN-{gamma} production and T cell proliferation, establishing that DNA-encoded, ribosomally translated peptides serve as CD1a-restricted cognate antigens. Biochemical analyses showed peptide binding to CD1a, supported by isoelectric focusing and surface plasmon resonance (KD [~]75 M for Ag85A). CD1a-peptide tetramers specifically stained cognate T cells, soluble CD1a was sufficient to present peptide antigen, and transfer of the LppX-specific TCR into naive T cells restored antigen responsiveness. Using CD1a-peptide tetramers, we identified antigen-specific T cells enriched in patients undergoing reversal reactions compared with patients with lepromatous leprosy and healthy donors. The CD1a-restricted T cell lines secreted IFN-{gamma} and IL-26, cytokines with established antimicrobial activity. Together, these findings demonstrate that CD1a can present canonical microbial peptides as part of a cell-mediated immune response in leprosy, extending the known spectrum of CD1a ligands. Because CD1a is nonpolymorphic and presents antigens to antimicrobial T cells, CD1a-peptide complexes may provide a broadly applicable platform for studying, detecting, and potentially targeting mycobacterial immunity.

immunology↗

bioRxiv2026

Targeting IL-6-STAT3/STAT4 Signaling Restores FOXP3 Expression in Pulmonary Arterial Endothelium and Reveals Novel Biomarkers for PAH

BackgroundInterleukin-6 (IL-6) is a central driver of pulmonary vascular remodeling in idiopathic, heritable, and connective tissue disease-associated pulmonary arterial hypertension (PAH). Elevated IL-6 correlates with right ventricular (RV) dysfunction and poor survival. However, the specific downstream mechanisms by which IL-6 drives pathogenesis remain poorly defined. We investigated the therapeutic impact of direct IL-6 neutralization and its regulation of a novel epigenetic signaling axis in PAH. Materials and MethodsWe evaluated species-specific IL-6-neutralizing antibodies in murine Sugen/hypoxia and rat monocrotaline models of PAH. RV structure and function were assessed using cardiac MRI and invasive hemodynamics. Lung transcriptomic profiling was performed by RNA sequencing mouse lung tissue. Key findings were validated in explanted human PAH lungs, serum, and peripheral blood mononuclear cells (PBMCs), and further interrogated through mechanistic in vitro studies in human pulmonary artery endothelial cells (PAECs). ResultsIL-6 neutralization significantly improved RV function, reduced pulmonary arterial pressures, and attenuated pulmonary vascular remodeling in both experimental models. Transcriptomic analysis identified a dysregulated FOXP3 signaling axis. Mechanistically, IL-6 induced cooperative binding of phosphorylated STAT3 and STAT4 to the FOXP3 promoter, facilitating DNMT1-mediated DNA methylation and stable gene silencing. IL-6 blockade restored downstream FOXP3 expression, rescued downstream BMPR2 signaling, and re-established endothelial homeostasis. In clinical PAH cohorts, FOXP3 expression was markedly reduced and inversely correlated with circulating IL-6 levels and indices of disease severity. ConclusionIL-6 drives pulmonary hypertension through STAT3/STAT4- and DNMT1-dependent epigenetic repression of FOXP3, linking chronic inflammation to BMPR2 dysfunction and pulmonary vascular remodeling. IL-6 neutralization reverses this pathogenic program in experimental PAH. FOXP3 emerges as a mechanistic biomarker of disease severity and a potential tool for precision stratification of patients likely to benefit from IL-6-targeted therapies. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LISynergistic Gene Repression: The study demonstrates that phosphorylated STAT3 functional transcriptional complex that binds directly to the FOXP3 promoter. Acting as a molecular scaffold, this complex actively represses FOXP3 expression within the pulmonary endothelium. C_LIO_LIEpigenetic Silencing Mechanism: IL-6 does not merely induce a transient suppression of FOXP3. Instead, IL-6/STAT3 signaling recruits DNMT1 to the FOXP3 promoter, leading to site-specific DNA methylation and long-term epigenetic silencing. This mechanism provides a direct molecular link between chronic systemic inflammation and sustained pulmonary vascular injury. C_LIO_LIThe FOXP3-BMPR2 Connection: The findings identify FOXP3 as a critical positive regulator of BMPR2 expression. Neutralization of IL-6 disrupts this pathological inhibitory loop, permitting restoration of BMPR2 signaling, the central gatekeeper of pulmonary vascular integrity and homeostasis. C_LIO_LITranslational Biomarkers: Importantly, the molecular changes within the lung are reflected systemically. Suppressed FOXP3 expression is readily detectable in PBMCs and serum, offering a non-invasive biomarker that correlates with pulmonary hemodynamic status and vascular health. C_LI Clinical ImplicationsO_LIPrecision Patient Stratification: FOXP3 expression in PBMCs and serum functions as a surrogate marker of pulmonary vascular epigenetic health. This could identify a specific inflammatory endotype of PAH patients most likely to respond to IL-6-targeted therapies. C_LIO_LIPrognostic Biomarker: Because FOXP3 levels integrate both systemic inflammatory burden and dysfunction of the RV-pulmonary vascular axis, they may provide a more sensitive tool for monitoring therapeutic response and predicting clinical worsening than current standard-of-care markers. C_LI

molecular biology↗

bioRxiv2026

Sotatercept Reverses SIN3a Deficiency-Driven PAH by Reprogramming BMPR2/TGF-β-HIF-1α Signaling Pathways

BackgroundPulmonary arterial hypertension is a progressive and fatal cardiopulmonary disease marked by excessive proliferation of pulmonary artery smooth muscle cells (PASMCs), pathological vascular remodeling, and ultimately right heart failure. Dysregulated BMPR2 signaling is a central molecular hallmark of PAH and is often associated with epigenetic suppression of BMPR2 expression. Switch-independent 3a (SIN3a), a transcriptional co-regulator and chromatin-modifying scaffold protein, has emerged as a key regulator of BMPR2 expression, yet its role in PAH pathogenesis remains poorly defined. MethodsWe generated smooth muscle cell-specific SIN3a knockout mice (SIN3aSMC-/-) and subjected them to the Sugen/hypoxia protocol to induce PAH. A cohort received Sotatercept treatment. In parallel, human PASMCs engineered to overexpress SIN3a were exposed to TGF{beta}1 or hypoxia (1% O2) in vitro. Comprehensive transcriptomic profiling and pathway analyses identified molecular networks regulated by SIN3a and Sotatercept. Hemodynamic measurements and detailed morphometric analyses were used to assess disease severity and treatment response. ResultsSIN3a overexpression in PASMCs suppressed hypoxia-inducible factor-1 and TGF-{beta}/SMAD2/3 signaling, restored BMPR2 expression, and activated canonical BMP signaling through SMAD1/5/9 phosphorylation, while reducing pro-inflammatory, oxidative, and fibrotic gene programs. Transcriptomic analyses revealed that SIN3a and Sotatercept converge on gene networks that regulate BMPR2 signaling, ID isoforms, extracellular matrix remodeling, oxidative stress, and inflammation. In vivo, smooth muscle-specific SIN3a deletion exacerbated Sugen/hypoxia-induced PAH, increasing right ventricular systolic pressure, right ventricular hypertrophy, pulmonary vascular remodeling, and fibrosis. Sotatercept treatment reversed these pathological features, restored SIN3a and BMPR2 expression, reactivated BMP signaling, and attenuated HIF-1 and TGF-{beta} signaling in SIN3a-deficient mice. ConclusionsSIN3a is a central epigenetic regulator of PASMC homeostasis that integrates oxidative stress, inflammation, and fibrotic signaling. Loss of SIN3a accelerates PAH progression, whereas Sotatercept restores SIN3a expression, rebalances BMPR2 and TGF-{beta} signaling, and attenuates pulmonary vascular remodeling and right ventricular dysfunction. Together, these findings identify SIN3a as a disease-relevant therapeutic target and support the use of Sotatercept as a disease-modifying approach for pulmonary vascular disease.

molecular biology↗

bioRxiv2020

Single Cell and Spatial Transcriptomics Defines the Cellular Architecture of the Antimicrobial Response Network in Human Leprosy Granulomas

Granulomas are complex cellular structures comprised predominantly of macrophages and lymphocytes that function to contain and kill invading pathogens. Here, we investigated single cell phenotypes associated with antimicrobial responses in human leprosy granulomas by applying single cell and spatial sequencing to leprosy biopsy specimens. We focused on reversal reactions (RR), a dynamic process in which some patients with disseminated lepromatous leprosy (L-lep) transition towards self-limiting tuberculoid leprosy (T-lep), mounting effective antimicrobial responses. We identified a set of genes encoding proteins involved in antimicrobial responses that are differentially expressed in RR versus L-lep lesions, and regulated by IFN-{gamma} and IL-1{beta}. By integrating the spatial coordinates of the key cell types and antimicrobial gene expression in RR and T-lep lesions, we constructed a map revealing the organized architecture of granulomas depicting compositional and functional layers by which macrophages, T cells, keratinocytes and fibroblasts contribute to the antimicrobial response.

immunology↗