Biology subjects

Cohen, S. B.

Publications and source records attributed to Cohen, S. B..

14 recordsLinked to original sources

bioRxiv2026

Modulation of Ferroptosis During Early Mycobacterium tuberculosis Infection Contributes to Beijing Lineage Strain SA161 Virulence

Although spread of internalized Mtb from the initial infected alveolar macrophages (AMs) is a crucial determinant of infection outcomes, the role of cell death in facilitating this spread, and how it is regulated by Mtb remains poorly understood. Ferroptosis, a lipid peroxidation-mediated form of necrotic cell death, contributes to pathology during later stages of infection. However, the role of ferroptosis in early AM cell death remains inadequately defined, and its induction during infection has been primarily studied with the laboratory strain, H37Rv. Using gene set variation analysis of single cell RNAseq data profiling Mtb-infected murine lungs, we found that the hypervirulent Beijing sublineage clinical strain SA161 is associated with an elevated pro-ferroptotic transcriptional response in AMs compared to H37Rv by 17 days post infection. Consistent with these transcriptional profiles, we found that SA161 induced increased lipid peroxidation in comparison to H37Rv during infection in vitro and in vivo. Administration of the lipid peroxidation inhibitor, ferrostatin-1 (Fer-1), reduces this Mtb-induced lipid peroxidation. Notably, we found that administration of Fer-1 to Mtb-infected mice significantly reduced bacterial burden for SA161 at 14 dpi while having no effect on H37Rv. Microscopic analysis of SA161-infected lung lesions at 14 dpi suggests that inhibition of ferroptosis-driving lipid peroxidation results in a greater proportion of AMs amongst infected cells and decreased neutrophil-associated IFN signaling. Collectively, these findings reveal that ferroptosis plays an important role during early infection with virulent clinical strains of Mtb by influencing bacterial spread and signaling of immune cell responders, potentially informing host-directed intervention strategies.

immunology↗

bioRxiv2026

Intranasal oxytocin mRNA-LNP can promote social behaviour and reduce pain

The COVID-19 epidemic and success of mRNA-LNP vaccines demonstrated the transformative potential of mRNA therapeutics. Beyond vaccination, mRNA delivery offers a platform for transient on-demand expression of therapeutic proteins for both rare and common diseases. While delivery of therapeutics to the liver is relatively straightforward, targeted delivery of mRNA-LNPs to the central nervous system (CNS) remains a significant challenge. Here we show that intranasal mRNA-LNP delivery results in localized mRNA cargo uptake and functional expression in the respiratory and olfactory epithelium, where the encoded cargo protein is secreted and can enter the CNS. Guided by genomic data of pain-associated gene expression, we identified secreted proteins as candidate mRNA-encoded analgesics. Intranasal mRNA-LNP encoding a synthetic oxytocin transcript (OXT) resulted in bioactive oxytocin peptide delivery to the CNS. Functionally, intranasal OXT mRNA-LNP enhanced social behaviour and attenuated pain responses across multiple behavioural paradigms, without impairing motor coordination. Importantly, repeated dosing was well tolerated and intranasal mRNA-LNP did not elicit an inflammatory response or alter overall health. Together, these findings establish intranasal mRNA-LNP delivery of secreted ligands as a safe, non-invasive route to target the CNS, unlocking a new class of mRNA therapeutics for pain or other disorders of the brain. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=189 SRC="FIGDIR/small/711938v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@131252aorg.highwire.dtl.DTLVardef@17efb79org.highwire.dtl.DTLVardef@1afe479org.highwire.dtl.DTLVardef@c0f2f5_HPS_FORMAT_FIGEXP M_FIG C_FIG One sentence summaryIntranasal administration of mRNA-LNP enables local transfection in nasal epithelium and subsequent secretion of therapeutic oxytocin peptides into the brain, promoting social interactions and reducing pain.

neuroscience↗

bioRxiv2026

SpeciefAI: Multi-species mRNA-level Antibody Framework Generation using Transformers

MotivationEncoding antibodies (Abs) and nanobodies (Nbs) as mRNA enables in vivo production of therapeutic proteins. However, this approach requires meeting two species-dependent requirements: the mRNA encoding must support efficient expression in the host species, and the encoded protein sequence must resemble the natural Ab repertoire of the recipient species to minimize immunogenicity. These requirements motivate species-conditioned generative models for joint mRNA and protein design. ResultsWe propose SpeciefAI a transformer-based model for multi-species Ab and Nb species sequence-harmonisation by generation of novel Framework Regions (FRs) tailored to input Complementarity-Determining Regions (CDRs). Our model works directly in the mRNA space and learns the correspondence between FRs and CDRs in six species. The model is capable of generating sequences with a highly similar distribution to natural sequences and a mean absolute difference in codon adaptation index (CAI) of 0.013 and 0.033 for humans and dogs respectively. We show that the generated human sequences are highly human (0.95 T20 score) and canine sequences highly canine (0.95 cT20 score). We furthermore demonstrate that we can generate diverse candidate sequences using our method. Availability and ImplementationSource code is available on https://github.com/Dominko/SpeciefAI. OAS and COGNANO data are publicly available on https://opig.stats.ox.ac.uk/webapps/oas/ and https://cognanous.com/datasets/vhh-corpus (preprocessed versions available upon request). Canine data is available on https://zenodo.org/records/18301526.

bioinformatics↗

bioRxiv2026

CPLfold: Chimeric and Pseudoknot-capable almost Linear-time RNA Secondary Structure Prediction

Motivation RNA structure plays a central role in how transcripts function, but inferring it reliably remains difficult, especially when pseudoknots need to be part of the prediction. Chemical probing experiments provide additional signals, yet these signals do not directly identify base pairing partners. RNA proximity ligation provides direct evidence of base pairing, but balancing this evidence with pseudoknot prediction accuracy and scalability of structure prediction for long sequences remains challenging. Results We present CPLfold, a fast and flexible RNA folding method that combines thermodynamic modeling with chimeric evidence from RNA cross-linking and ligation experiments, while naturally supporting pseudoknots. CPLfold scales to long sequences and recovers more accurate global structures and long-range interactions than existing approaches across multiple benchmarks such as COMRADES and IRIS. By tuning two simple trade-off parameters (, {beta}) the method allows flexibility in the level of incorporating chimeric evidence and asserting pseudoknots. Availability and Implementation Source code and scripts are available at https://github.com/Vicky-0256/CPLfold. ContactK.Wang-72@sms.ed.ac.uk

bioinformatics↗

bioRxiv2025

Single-cell profiling reveals that dynamic lung immune responses distinguish protection from susceptibility to tuberculosis

The mechanisms that underlie protective immunity to Mycobacterium tuberculosis (Mtb) remain incompletely defined. To identify immune correlates associated with protection, we performed single-cell RNA sequencing of lung immune cells after aerosol Mtb infection of naive mice and mice with contained Mtb infection (CoMtb), a model of naturally acquired resistance, across multiple time points, mouse strains, and Mtb strains. Across conditions, protection was associated with distinct temporal patterns of immune activation, cell recruitment, and resolution. Early after challenge, CoMtb mice exhibited rapid, transient recruitment and activation of CD4 T cells, macrophages, NK, and NKT cells, accompanied by short-lived bursts of type I and II interferon signaling, increased oxidative phosphorylation, and enhanced chemokine-mediated cell-cell communication. In contrast, primary infection elicited delayed but sustained interferon and neutrophil responses and higher bacterial burdens. These data indicate that protection involves dynamically coordinated immune pathways rather than the magnitude of any single response. Transcriptional features of CoMtb overlapped with those observed in nonhuman primates following intravenous BCG vaccination, including enrichment of activated tissue-resident CD4 T cells and innate effector populations. Together, these findings support a model in which effective immunity to Mtb depends on the timing and coordination of immune activation, providing a framework for vaccine strategies that reproduce protective lung immune dynamics.

immunology↗

bioRxiv2025

ESX-5 Deletions in Mycobacterium tuberculosis Alter Macrophage Cytokine Signaling and Bacterial Heavy Metal Response

The ESX-5 secretion system is critical for Mycobacterium tuberculosis (Mtb) viability and putatively linked to pathogenesis, but a functional understanding of how it interacts with the host is unknown. ESX-5 is encoded at a single genomic locus with small, paralogous, secreted targets (ESX-5a, 5b, 5c) spaced throughout the genome. To examine host-pathogen interactions of these putative virulence clusters, we made mutant strains lacking these loci and infected primary human macrophages. Surprisingly, all deletion mutants independently reduced cytokine secretion during infection, specific to certain analytes. This defect depended on viable bacteria and was mediated by a post-transcriptional mechanism. In bacterial transcriptomic analyses, each mutant downregulated heavy metal response genes compared to wild type bacteria. Treatment of Mtb with Cu or Cd led to increased ESX-5a and ESX-5c expression, concurrent with increased TNF and IL-6 secretion in macrophages compared to untreated bacilli, indicating a link between ESX-5 expression and cellular cytokine levels.

immunology↗

bioRxiv2024

CD4-mediated immunity shapes neutrophil-driven tuberculous pathology

Pulmonary Mycobacterium tuberculosis (Mtb) infection results in highly heterogeneous lesions ranging from granulomas with central necrosis to those primarily comprised of alveolitis. While alveolitis has been associated with prior immunity in human post-mortem studies, the drivers of these distinct pathologic outcomes are poorly understood. Here, we show that these divergent lesion structures can be modeled in C3HeB/FeJ mice and are regulated by prior immunity. Using quantitative imaging, scRNAseq, and flow cytometry, we demonstrate that Mtb infection in the absence of prior immunity elicits dysregulated neutrophil recruitment and necrotic granulomas. In contrast, prior immunity induces rapid recruitment and activation of T cells, local macrophage activation, and diminished late neutrophil responses. Depletion studies at distinct infection stages demonstrated that neutrophils are required for early necrosis initiation and necrosis propagation at chronic stages, whereas early CD4 T cell responses prevent neutrophil feedforward circuits and necrosis. Together, these studies reveal fundamental determinants of tuberculosis lesion structure and pathogenesis, which have important implications for new strategies to prevent or treat tuberculosis.

immunology↗

bioRxiv2024

Re-appraising the role of T-cell derived interferon gamma in restriction of Mycobacterium tuberculosis in the murine lung

T cells producing interferon gamma (IFN{gamma}) have long been considered a stalwart for immune protection against Mycobacterium tuberculosis (Mtb), but their relative importance to pulmonary immunity has been challenged by murine studies which achieved protection by adoptively transferred Mtb-specific IFN{gamma}-/-T cells. Using IFN{gamma}-/- T cell chimeric mice and adoptive transfer of IFN{gamma}-/-T cells into TCR{beta}-/-{delta}-/-mice, we demonstrate that control of lung Mtb burden is in fact dependent on T cell-derived IFN{gamma}, and furthermore, mice selectively deficient in T cell-derived IFN{gamma} develop exacerbated disease compared to T cell-deficient controls despite equivalent lung bacterial burdens. Deficiency in T cell-derived IFN{gamma} skews infected and bystander monocyte-derived macrophages (MDMs) to an alternative M2 phenotype, and promotes neutrophil and eosinophil influx. Our studies support an important role for T cell-derived IFN{gamma} in pulmonary immunity against TB.

immunology↗

bioRxiv2023

Highly amine-reactive graphene-oxide EM grids for biochemical surface modification in aqueous buffer

Graphene oxide (GO), an oxidized derivative of graphene, has found application in cryo-electron microscopy (cryo-EM) as a hydrophilic and transparent solid support on which to adsorb biological macromolecules, providing an alternative to traditional aqueous films. Current applications generally adsorb the macromolecule directly onto unmodified GO or modify the GO surface with polyethylene glycol-amine reagents. This nucleophilic amine reaction must be performed in an aprotic organic solvent and therefore precludes the use of biological samples such as nucleic acids and peptides. The utility of GO could be expanded by the ability to covalently modify its surface with biochemical affinity reagents such as small- molecule metabolites, peptides, or nucleic acids, in aqueous buffer at neutral pH. Presented here is a chemical procedure that converts all oxygen functionalities of GO to highly amine- reactive glycidyl epoxide groups, achieved without the need of specialized laboratory equipment. We show that single sheets of glycidyl epoxide-modified GO react on the EM grid with primary amines at micromolar concentrations in minutes at room temperature in aqueous buffer. Given the ease of derivatizing biochemical reagents with amines, the chemistry described here will enable imaging of macromolecules immobilized on GO through specific biochemical and biologically relevant binding interactions.

molecular biology↗

bioRxiv2023

Assessing vaccine-mediated protection in an ultra-low dose Mycobacterium tuberculosis murine model

Despite widespread immunization with Bacille-Calmette-Guerin (BCG), the only currently licensed tuberculosis (TB) vaccine, TB remains a leading cause of mortality globally. There are many TB vaccine candidates in the developmental pipeline, but the lack of a robust animal model to assess vaccine efficacy has hindered our ability to prioritize candidates for human clinical trials. Here we use a murine ultra-low dose (ULD) Mycobacterium tuberculosis (Mtb) challenge model to assess protection conferred by BCG vaccination. We show that BCG confers a reduction in lung bacterial burdens that is more durable than that observed after conventional dose challenge, curbs Mtb dissemination to the contralateral lung, and, in a small percentage of mice, prevents detectable infection. These findings are consistent with the ability of human BCG vaccination to mediate protection, particularly against disseminated disease, in specific human populations and clinical settings. Overall, our findings demonstrate that the ultra-low dose Mtb infection model can measure distinct parameters of immune protection that cannot be assessed in conventional dose murine infection models and could provide an improved platform for TB vaccine testing.

microbiology↗

bioRxiv2021

TCAB1 is necessary for telomerase assembly

Localization of a wide variety of RNAs to non-membrane bound cellular compartments such as nucleoli, Cajal bodies, and stress-granules is critical for their function and stability. The molecular mechanisms that underly the recruitment and exclusion of specific RNAs from these phase-separated organelles is incompletely understood. Telomerase is a ribonucleoprotein (RNP) that is composed of the reverse transcriptase protein TERT, the telomerase RNA (TR), and several auxiliary proteins that associate with TR, including TCAB1. Here we show that in the absence of TCAB1, TR is tightly bound to the nucleolus, while TERT localizes to the nucleoplasm and is largely excluded from the nucleolus, significantly reducing telomerase assembly. Thus, nuclear compartmentalization by the non-membrane bound nucleolus counteracts telomerase assembly and TCAB1 is required to exclude the telomerase RNA from the nucleolus. Our work provides insight into the mechanism and functional consequences of RNA recruitment to organelles formed by phase separation proposes a new model explaining the critical role of TCAB1 in telomerase function.

cell biology↗

bioRxiv2020

TOLLIP promotes durable alveolar macrophage-mediated immunity during Mycobacterium tuberculosis infection by resolving cellular stress from lipids.

Relative deficiency of TOLLIP expression in monocytes is associated with increased tuberculosis (TB) susceptibility in genetic studies, despite antagonizing host innate immune pathways that control Mycobacterium tuberculosis (Mtb) infection. In this study, we investigated the mechanisms by which TOLLIP influences Mtb immunity. Tollip-/- mice developed worsened disease, consistent with prior genetic observations, and developed large numbers of foam cells. Selective TOLLIP deletion in alveolar macrophages (AM) was sufficient to induce lipid accumulation and increased Mtb persistence 28 days after infection, despite increased antimicrobial responses. We analyzed sorted, Mtb-infected Tollip-/- AM from mixed bone marrow chimeric mice to measure global gene expression 28 days post-infection. We found transcriptional profiles consistent with increased EIF2 signaling. Selective lipid administration to Tollip-/- macrophages induced lipid accumulation, and Mtb infection of lipid laden, Tollip-/- macrophages induced cellular stress and impaired Mtb control. EIF2 activation induced increased Mtb replication within macrophages, irrespective of TOLLIP expression, and EIF2 kinases were enriched in human caseous granulomas. Our findings define a critical checkpoint for TOLLIP to prevent lipid-induced EIF2 activation and demonstrate an important mechanism for EIF2 signaling to permit Mtb replication within macrophages.

immunology↗

bioRxiv2020

A mechanism for the extension and unfolding of parallel telomeric G-quadruplexes by human telomerase at single-molecule resolution

Telomeric G-quadruplexes (G4) were long believed to form a protective structure at telomeres, preventing their extension by the ribonucleoprotein telomerase. Contrary to this belief, we have previously demonstrated that parallel-stranded conformations of telomeric G4 can be extended by human and ciliate telomerase. However, a mechanistic understanding of the interaction of telomerase with structured DNA remained elusive. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) microscopy and bulk-phase enzymology to propose a mechanism for the resolution and extension of parallel G4 by telomerase. Binding is initiated by the RNA template of telomerase interacting with the G-quadruplex; nucleotide addition then proceeds to the end of the RNA template. It is only through the large conformational change of translocation following synthesis that the G-quadruplex structure is completely unfolded to a linear product. Surprisingly, parallel G4 stabilization with either small molecule ligands or by chemical modification does not always inhibit G4 unfolding and extension by telomerase. These data reveal that telomerase is a parallel G-quadruplex resolvase.

biochemistry↗

bioRxiv2019

BCG-induced T cells shape Mycobacterium tuberculosis infection before reducing the bacterial burden

Growing evidence suggests the outcome of Mycobacterium tuberculosis (Mtb) infection is established rapidly after exposure, but how the current tuberculosis vaccine, BCG, impacts early immunity is poorly understood. Here we found that murine BCG immunization promotes a dramatic shift in infected cell types. While alveolar macrophages (AM) are the major infected cell for the first two weeks in unimmunized animals, BCG promotes the accelerated recruitment and infection of lung infiltrating phagocytes. Interestingly, this shift is dependent on CD4 T cells, yet does not require intrinsic recognition of antigen presented by infected AM. Mtb-specific T cells are first activated in lung regions devoid of infected cells, and these events precede vaccine-induced reduction of the bacterial burden, which occurs only after the co-localization of T cells and infected cells. Understanding how BCG alters early immune responses to Mtb provides new avenues to improve upon the immunity it confers.

immunology↗