Biology subjects

Aggarwal, M.

Publications and source records attributed to Aggarwal, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Mapping Gene Expression to an Interpretable Semantic Space

Cell embeddings organize single-cell expression data, but their dimensions have no biological meaning, so clusters are interpreted afterward. We present MESIC (Mapping Expression to Semantic space with Interpretable Components), which builds the written knowledge about genes held in curated databases into the dimensions themselves. A biomedical language model converts each gene's summary into a semantic embedding. MESIC compresses these embeddings into a small number of components, each concentrated on a small set of genes and explained by their annotations. The components are computed once from the summaries, so any expression dataset can be mapped onto them, and every cluster, outlier, or cell-type assignment is then characterized by named genes. In cardiomyocytes, outliers in the component space were enriched for hypertrophic cardiomyopathy. In a lung atlas, unsupervised clusters in that space matched the broad cell types that experts had annotated. In both, the components that separated the cells matched their known biology. For about half of the cells that the atlas itself had left unannotated, the same space gave a confident cluster assignment, and with it an interpretation through component-associated genes. Gene summaries thus give single-cell analysis a coordinate system in which every result is traced to genes and what is written about them.

bioinformatics↗

bioRxiv2026

PartiNet is a dynamic adaptive neural network for high-performance particle picking in cryo-electron microscopy

Accurate, efficient and autonomous particle picking is a major bottleneck in high-resolution cryo-electron microscopy (cryo-EM). We introduce PartiNet, an Artificial Intelligence (AI)-based particle picker with size-agnostic detection and pre-trained models that eliminate manual parameter specification and dataset-specific training, pioneering dynamic neural network inference for single particle cryo-EM pipeline. Unlike static architectures, PartiNet employs a dynamic framework that adjusts network complexity in real-time based on perceived micrograph quality. This adaptive approach accelerates inference up to 7-fold compared to existing tools without sacrificing particle selection quality. Training on diverse protein datasets showed that PartiNet improves particle yields, enhances sampling of rare orientations, and is compatible with on-the-fly workflows. Comprehensive evaluation on benchmark datasets and validation on a new dataset of the chromatin remodeler MORC2 demonstrates superior precision and recall, with the ability to detect heterogeneous protein species, leading to more complete structural models and consistently higher-resolution reconstructions.

molecular biology↗

bioRxiv2025

Dual Preconditioned Mesenchymal Stem Cells-Derived Culture Conditioned Media Augment Immunomodulation and Drive Metabolic Reprogramming in Acute Graft-versus-Host Disease

BackgroundThe toxicity associated with conventional conditioning regimens limits treatment outcomes in autoimmune disorders such as acute graft-versus-host disease (aGVHD). Developing effective adjunctive interventions to restore immune balance is therefore essential. This study investigated the immunomodulatory potential of mesenchymal stem cells (MSCs)-derived culture-conditioned media (CCM) from naive and preconditioned MSCs-hypoxic (MSCsHYP), apoptotic (MSCsAPO), and dual preconditioned (MSCsHYP+APO) in aGVHD. MethodsHuman MSCs isolated from bone marrow and Whartons Jelly were preconditioned under hypoxia (1% O2), apoptosis (1 {micro}M staurosporine, 24 h), or both. The immunoregulatory and antioxidant properties of their CCM were evaluated through T-cell proliferation assays, Treg induction, macrophage polarization, mitochondrial function, and T-cell bioenergetics. Comparative proteomic profiling of CCM from WJ-MSCs and WJ-MSCsHYP+APO co-cultured with aGVHD patient-derived activated PBMNCs was performed using LC-MS/MS, alongside in vivo validation in a chemotherapy-induced aGVHD murine model. ResultsWJ-MSCsHYP+APO-CCM exhibited superior immunomodulatory efficacy, suppressing T-cell proliferation, promoting Treg and Th2/Th9 differentiation, and driving M2 macrophage polarization. It reduced mitochondrial ROS, enhanced mitochondrial polarization, and shifted T-cell metabolism from glycolysis toward oxidative phosphorylation. Proteomic analysis revealed modulation of IL-12, IL-17, and JAK-STAT pathways, along with regulation of complement, coagulation, and metabolic cascades. Interaction with immune cells further enhanced its antioxidant and tissue-reparative properties via extracellular matrix remodeling. ConclusionDual preconditioning under hypoxia and apoptosis amplifies the immunomodulatory, antioxidant, and reparative efficacy of WJ-MSC-CCM, offering a potent non-cellular therapeutic strategy for aGVHD management. GRAPHICAL ABSTRACTImmunomodulatory and immune metabolic reprogramming potential of naive and preconditioned MSCs (MSCs, MSCsHYP, MSCsAPO, MSCsHYP+APO) derived CCM in Acute GVHD (created using Biorender.com) O_FIG O_LINKSMALLFIG WIDTH=95 HEIGHT=200 SRC="FIGDIR/small/686182v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@f7ed73org.highwire.dtl.DTLVardef@1063015org.highwire.dtl.DTLVardef@13ed827org.highwire.dtl.DTLVardef@e103c0_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Forecasting drug resistant HIV protease evolution

Protease inhibitors (PIs) target the protease (PR) enzyme to suppress viral replication. Their efficacy in human immunodeficiency virus treatment is compromised by the emergence of drug-resistant strains. Therefore, forecasting drug-resistance during viral evolution would help in the design of effective treatment strategies. We develop a probabilistic large-deviation model to infer epistatic interactions in genotypes observed in different treatment regimens and compute transition probabilities of point-mutations conditioned on the genotype and the treatment regimen. We simulate stochastic evolutionary paths weighted by such transition probabilities and show that low probable mutations are required for the viral population to evolve to diverse fit genotypes. We train classification models using a clinical data set of in vitro susceptibility tests to learn to infer the drug resistance of a genotype. We infer drug resistance along simulated evolutionary paths and predict that the combination PI-therapy of Atazanavir (ATV) and Ritonavir (RTV) is the least drug resistant. Without prior knowledge of PI-associated mutations, our model predicts known primary and secondary PI-resistant mutations as critical to drug resistance. This validates that our model learned mechanistic relations in the small data sets, tackling the challenge of sparse sequence data compared to the large combinatorial complexity of protein evolution and changing functionality in dynamic environments.

systems biology↗

bioRxiv2025

Predictive Modeling of acute Graft-versus-Host-Disease using Machine Learning on Immune Cell and Cytokine Profiles at Engraftment

BackgroundAcute Graft-versus-Host-Disease (aGvHD) is a major immune complication following allogenic hematopoietic stem cell transplantation (Allo-HSCT), initiated by conditioning regimen-associated tissue damage. It involves the complex interplay of immune cells and cytokines. Our study aims to leverage machine learning (ML) algorithms on the immune and cytokine profile of Allo-HSCT recipients to develop biomarker-based classification models to predict the onset of aGvHD at the time of engraftment. Materials and MethodsSeventy patients diagnosed with hematological disorders who had undergone Ist Allo-HSCT were recruited from All India Institute of Medical Sciences, New Delhi, India. Peripheral blood (PB) was collected from the patients at the time of engraftment, and the immune cell subtypes and cytokine profiles were analyzed using flow cytometry and ELISA respectively. The individual cell counts were then processed using basic ML models, including support vector classifier with RBF kernel, Decision Tree, and Random Forest, chosen for their mathematical simplicity and feature importance advantage of Decision Trees and Random Forests. Various data settings were utilized in the study: combined immune and cytokine counts, immune cell counts only, cytokine counts only, T-cell counts only, NK cell counts only, dendritic cell counts only, and B-cell counts only. These configurations were selected to investigate how different data sets impact the prediction of aGvHD before its onset. ResultsAt the engraftment flow cytometric analysis of reconstituted lymphocytes in patients who developed aGvHD revealed that there was a remarkable decrease in the ratio of CD4+/CD8+ T-cell and Tregs, with an increase in the cytotoxic regulatory NK-cell, dendritic cells, and B-cell. The levels of pro-inflammatory cytokines (IFN-{gamma}, IL-1{beta}, IP-10, TNF-, IL-17, IL-12p70, MIP-1, MIP-1{beta}, RANTES), and Th17-and Th1-cells were elevated with consequent decline of the levels of anti-inflammatory cytokine IL-10, IL-2, IL-4 and Th2-, Th9-cells. Machine learning based on 48 parameters [all immune cell subsets n=34 and all cytokines (n=14)]. The correlation heat map shows a higher correlation of aGvHD with the cytokine profile with or without immune cells (accuracy: 1), T-cell alone (accuracy: 0.96); NK-cell alone (accuracy: 0.93); dendritic cells alone (accuracy: 0.90), B-cell alone (accuracy: 0.86). ConclusionThe current models classify perfectly, indicating the potential for a ML algorithm in predicting the onset of aGvHD. However, a study with a larger sample size is required to validate these classification models and mitigate the risk of overfitting observed due to the consistently high performance. The study also highlights the potential of cytokine profiles as a viable alternative to T-cell counts, as evidenced by the correlation heat map and classifier models. These findings provide valuable insights into dataset requirements and future directions for integrating ML models into aGvHD prediction.

immunology↗

bioRxiv2025

Dose-Response Immunomodulatory Effects of Mesenchymal Stem Cells-Derived Culture-Conditioned Media in Acute Graft-versus-Host-Disease

BackgroundMesenchymal stem cell-based therapy faces challenges that have driven interest in MSCs-derived culture-conditioned media (CCM) as a cell-free alternative. Our study aims to optimize the dose, and collection timing of CCM to enhance its therapeutic efficacy in aGVHD, while also standardizing co-culture conditions for CD3+ T-cell interaction with CCM. Material and MethodsHuman MSCs were isolated from BM and WJ and subsequently preconditioned under hypoxic conditions (1% O2) for 24 hours in a tri-gas incubator. Culture-conditioned media (CCM) was collected from both naive and hypoxia-preconditioned MSCs at 24, 48, and 72 hours and filtered using a 0.2 m membrane filter. CD3+ T-cell were isolated from PBMNCs derived from aGVHD patients. These T-cell were co-cultured at varying densities (2*106, 5*106, and 10*106 cells/ml) with different concentrations of CCM (25%, 50%, and 100%), and cell proliferation was assessed using the MTS assay. Furthermore, CD3+ T-cell proliferation and activation status were evaluated in a 2D co-culture model of CD3+ T-cell and CCM using flow cytometry. ResultsOur findings revealed that CCM collected at 48 hours, at a 50% concentration, exerted the most pronounced inhibitory effect on CD3+ T-cell proliferation, particularly at a density of 5*106 cells/ml, irrespective of the MSCs source. Hypoxia preconditioning significantly enhanced the immunomodulatory effects, with WJ-MSCsHYP-CCM demonstrating superior efficacy in suppressing T-cell proliferation, increasing the CD4+/CD8+ T-cell ratio, and reducing CD4+ T-cell activation compared to BM-MSCsHYP-CCM. ConclusionThese results emphasize the critical role of optimizing CCM collection timing and concentration to maximize therapeutic potential. Our study paves the way for the development of standardized, scalable, and effective cell-free therapies for aGVHD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=198 HEIGHT=200 SRC="FIGDIR/small/640019v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@16ecc48org.highwire.dtl.DTLVardef@12591dborg.highwire.dtl.DTLVardef@18af4beorg.highwire.dtl.DTLVardef@1c9e8c9_HPS_FORMAT_FIGEXP M_FIG C_FIG Optimum conditions for CCM dose, collection time point, and CD3+ T-cell dose for effective immunomodulatory effect of MSCs-derived CCM in aGVHD. (created using Biorender.com)

immunology↗

bioRxiv2025

Sensitivity based model agnostic scalable explanations of deep learning

Deep neural networks (DNNs) are powerful tools for data-driven predictive machine learning, but their complex architecture obscures mechanistic relations that they have learned from data. This information is critical to the scientific method of hypotheses development, experiment design, and model validation, especially when DNNs are used for biological and clinical predictions that affect human health. We design SensX, a model agnostic explainable AI (XAI) framework that outperformed current state-of-the-art XAI in accuracy (up to 52% higher) and computation time (up to 158 times faster), with higher consistency in all cases. It also determines an optimal subset of important input features, reducing dimensionality of further analyses. SensX scaled to explain vision transformer (ViT) models with more than 150, 000 features, which is computationally infeasible for current state-of-the-art XAI. SensX validated that ViT models learned justifiable features as important for different facial attributes of different human faces. SensX revealed biases inherent to the ViT architecture, an observation possible only when importance of each feature is explained. We trained DNNs to annotate biological cell types using single-cell RNA-seq data and SensX determined the sets of genes that the DNNs learned to be important to different cell types.

systems biology↗

bioRxiv2025

Hypoxia-Mediated Molecular Interactions of Tissue-Specific Mesenchymal Stem Cells Drive Metabolic Reprogramming and Immunomodulation in Acute Graft-versus-Host Disease

BackgroundMesenchymal stem cells (MSCs) mediate immunomodulation through various mechanisms, including apoptosis, efferocytosis, and mitochondrial transfer. Our study investigates the impact of hypoxia preconditioning on the immune metabolic reprogramming and immunomodulatory potential of MSCs in acute graft-versus-host disease (aGVHD). Additionally, we explored the differential immunomodulatory effects of tissue-specific MSCs, specifically bone marrow (BM) and Whartons Jelly (WJ), and elucidated the mechanisms underlying variability in their therapeutic efficacy. MethodsMSCs were isolated from BM and WJ and subjected to hypoxia preconditioning. Their immunometabolic programming potential was assessed by evaluating T-cell proliferation, regulatory T-cell (Treg) induction, effector T-cell differentiation toward Th2, Th9 phenotypes, and macrophage polarization, T-cell bioenergetics in the direct co-culture systems. ResultsWJ-MSCsHYP exhibited superior immunomodulatory properties compared to BM-MSCsHYP, by inhibiting T-cell proliferation, enhancing Treg induction, and promoting anti-inflammatory macrophage polarization. WJ-MSCsHYP demonstrated enhanced mitochondrial transfer to T-cell, improving mitochondrial health, reducing ROS, and promoting oxidative phosphorylation, leading to immune homeostasis. Unlike BM-MSCs, WJ-MSCs exhibited higher rates of apoptosis, which facilitated immune modulation through mechanisms independent of efferocytosis. ConclusionOur findings highlight that WJ-MSCsHYP is a superior candidate for aGVHD by utilizing apoptosis, mitochondrial transfer, and metabolic reprogramming to achieve immune regulation.

immunology↗

bioRxiv2024

A Comparative assessment of T-Cell response of Healthy donors and Acute Graft-versus-Host-Disease Patients: Customizing immune monitoring platform

BackgroundT-cell activation and proliferation are critical for understanding immune responses in both healthy and pathological conditions such as acute graft-versus-host disease (aGVHD). Phytohemagglutinin (PHA) and interleukin-2 (IL-2) are commonly used in in vitro assays to study T-cell responses. In view of the discrete response of T cells from aGvHD patients cohorts, our study optimized PHA / IL-2 based T-cell response among healthy individuals versus aGVHD patients. MethodsPeripheral blood was collected from age- and sex-matched healthy individuals (n=10) and aGVHD patients (n=10). CD3+ T-cell were isolated and stimulated with varying concentrations of PHA (1-10g/ml) and IL-2 (50-500 IU/ml). Cell proliferation was assessed using MTS and CFSE assays, while their apoptosis was evaluated with Annexin V/7-AAD staining. ResultsWe observed enhanced proliferation of healthy individuals at higher PHA concentrations (5-10g/ml), whereas aGVHD patients exhibited heightened proliferation even at lower PHA concentrations (1-2.5g/ml) at 48 hours. Prolonged exposure of T cells from GvHD patients to PHA led to decreased proliferation while it increased in the T cells from healthy donors.IL-2 supplementation (50 IU/ml) of T-cells from healthy donors significantly enhanced their proliferation and survival, with the optimal concentration supporting robust proliferation over extended culture periods. ConclusionOur study optimized PHA and IL-2 concentrations required for T-cell proliferation studies among healthy individuals and aGVHD patients. and underscored experimental conditions required for studying T-cell behavior/dysregulation in aGVHD condition. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/611044v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@ab3c47org.highwire.dtl.DTLVardef@2786forg.highwire.dtl.DTLVardef@30c698org.highwire.dtl.DTLVardef@3e4821_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights of the studyO_LILower doses of PHA (1.0g/ml) and IL-2 (50IU/ml) are optimum conditions for aGVHD patients derived CD3+ T-cell proliferation under in vitro conditions. C_LIO_LIThe maximum T-cell proliferation in healthy individuals occurs with 7.5g/ml PHA and 50IU/ml IL-2. C_LIO_LIHigher doses of PHA induce cytotoxicity in both cohorts. C_LIO_LIIL-2 significantly enhances T-cell survival, with 50IU/ml maintaining robust proliferation over extended periods. C_LI

immunology↗

bioRxiv2024

Malnutrition drives infection susceptibility and dysregulated myelopoiesis that persists after refeeding intervention

Undernutrition is one of the largest persistent global health crises, with nearly 1 billion people facing severe food insecurity. Infectious disease represents the main underlying cause of morbidity and mortality for malnourished individuals, with infection during malnutrition representing the leading cause of childhood mortality worldwide. In the face of this complex challenge, simple refeeding protocols have remained the primary treatment strategy. Although an association between undernutrition and infection susceptibility has been appreciated for over a century, the underlying mechanisms remain poorly understood and the extent to which refeeding intervention is sufficient to reverse nutritionally acquired immunodeficiency is unclear. Here we investigate how malnutrition leads to immune dysfunction and the ability of refeeding to repair it. We find that chronic malnutrition induced through prolonged dietary restriction (40% reduction in food intake) severely impairs the ability of mice to control a sub-lethal Listeria monocytogenes infection. Malnourished mice exhibit blunted immune cell expansion, impaired immune function, and accelerated contraction prior to pathogen clearance. While this defect is global, we find that myelopoiesis is uniquely impacted, resulting in reduced neutrophil and monocyte numbers prior to and post-infection. Upon refeeding, we observe that mice recover body mass, size, cellularity across all major immune organs, the capacity to undergo normal immune cell expansion in response to infection, and a restoration in T cell responses. Despite this broad improvement, refed mice remain susceptible to Listeria infection, uncoupling global lymphoid atrophy from immunodeficiency. We find peripheral neutrophil and monocyte numbers fail to fully recover and refed mice are unable to undergo normal emergency myelopoiesis. Altogether, this work identifies dysregulated myelopoiesis as a link between prior nutritional state and immunocompetency. We believe these findings raise the possibility that exposure to food scarcity should be treated as an immunologic variable, even post-recovery, with considerations for how patient medical history and public health policy.

immunology↗

bioRxiv2024

Synergistic Hypoxia and Apoptosis Conditioning Unleashes Superior Mesenchymal Stem Cells Efficacy in Acute Graft-versus-Host-Disease

Mesenchymal stem cells (MSCs) have emerged as promising candidates for immune modulation in various diseases that are associated with dysregulated immune responses like Graft-versus-Host-Disease (GVHD). MSCs are pleiotropic and the fate of MSCs following administration is a major determinant of their therapeutic efficacy. In this context, we here demonstrate that hypoxia preconditioned apoptotic MSCs [bone marrow (BM), Whartons Jelly (WJ)] bear more immune programming ability in a cellular model of acute Graft-versus-Host-Disease (aGVHD). To this purpose, we programmed MSCs by exposing them to hypoxia and inducing apoptosis both sequentially as well as simultaneously. Our findings demonstrated that WJ MSCs that were conditioned with indicated approaches simultaneously induced the differentiation of CD4+T-cell towards Tregs, enhanced Th2 effector, and concomitantly mitigated Th1 and Th17, with polarization of M1 effector macrophages towards their M2 phenotype, and more interestingly enhanced efferocytosis by macrophages indicated Th2 programming ability of MSCs programmed by conjunctional approaches Overall, our study highlights the potential of WJ-MSCs conditioned with hypoxia and apoptosis concurrently, as a promising therapeutic strategy for aGVHD and underscores the importance of considering MSC apoptosis in optimizing MSCs-based cellular therapy protocols for enhanced therapeutic efficacy in aGvHD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=123 HEIGHT=200 SRC="FIGDIR/small/588248v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@92c102org.highwire.dtl.DTLVardef@bd895forg.highwire.dtl.DTLVardef@185e041org.highwire.dtl.DTLVardef@45ef0f_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

Distinguishing microgliosis and tau deposition in the mouse brain using paramagnetic and diamagnetic susceptibility source separation

Tauopathies, including Alzheimers disease (AD), are neurodegenerative disorders characterized by hyperphosphorylated tau protein aggregates in the brain. In addition to protein aggregates, microglia-mediated inflammation and iron dyshomeostasis are other pathological features observed in AD and other tauopathies. It is known that these alterations at the subcellular level occur much before the onset of macroscopic tissue atrophy or cognitive deficits. The ability to detect these microstructural changes with MRI therefore has substantive importance for improved characterization of disease pathogenesis. In this study, we demonstrate that quantitative susceptibility mapping (QSM) with paramagnetic and diamagnetic susceptibility source separation has the potential to distinguish neuropathological alterations in a transgenic mouse model of tauopathy. 3D multi-echo gradient echo data were acquired from fixed brains of PS19 (Tau) transgenic mice and age-matched wild-type (WT) mice (n = 5 each) at 11.7 T. The multi-echo data were fit to a 3-pool complex signal model to derive maps of paramagnetic component susceptibility (PCS) and diamagnetic component susceptibility (DCS). Group-averaged signal fraction and composite susceptibility maps showed significant region-specific differences between the WT and Tau mouse brains. Significant bilateral increases in PCS and |DCS| were observed in specific hippocampal and cortical sub-regions of the Tau mice relative to WT controls. Comparison with immunohistological staining for microglia (Iba1) and phosphorylated-tau (AT8) further indicated that the PCS and DCS differences corresponded to regional microgliosis and tau deposition in the PS19 mouse brains, respectively. The results demonstrate that quantitative susceptibility source separation may provide sensitive imaging markers to detect distinct pathological alterations in tauopathies.

neuroscience↗

bioRxiv2024

Senolytic therapy preserves blood-brain barrier integrity and promotes microglia homeostasis in a tauopathy model

Cellular senescence, characterized by expressing the cell cycle inhibitory proteins, is evident in driving age-related diseases. Senescent cells play a crucial role in the initiation and progression of tau-mediated pathology, suggesting that targeting cell senescence offers a therapeutic potential for treating tauopathy associated diseases. This study focuses on identifying non-invasive biomarkers and validating their responses to a well-characterized senolytic therapy combining dasatinib and quercetin (D+Q), in a widely used tauopathy mouse model, PS19. We employed human-translatable MRI measures, including water extraction with phase-contrast arterial spin tagging (WEPCAST) MRI, T2 relaxation under spin tagging (TRUST), longitudinally assessed brain physiology and high-resolution structural MRI evaluated the brain regional volumes in PS19 mice. Our data reveal increased BBB permeability, decreased oxygen extraction fraction, and brain atrophy in 9-month-old PS19 mice compared to their littermate controls. (D+Q) treatment effectively preserves BBB integrity, rescues cerebral oxygen hypometabolism, attenuates brain atrophy, and alleviates tau hyperphosphorylation in PS19 mice. Mechanistically, D+Q treatment induces a shift of microglia from a disease-associated to a homeostatic state, reducing a senescence-like microglial phenotype marked by increased p16/INK4a. D+Q-treated PS19 mice exhibit enhanced cue-associated cognitive performance in the tracing fear conditioning test compared to the vehicle-treated littermates, implying improved cognitive function by D+Q treatment. Our results pave the way for application of senolytic treatment as well as these noninvasive MRI biomarkers in clinical trials in tauopathy associated neurological disorders.

neuroscience↗

bioRxiv2023

Influenza A virus resistance to 4-fluorouridine coincides with viral attenuation in vitro and in vivo

Pre-existing or rapidly emerging resistance of influenza viruses to approved antivirals makes the development of novel therapeutics to mitigate seasonal influenza and improve preparedness against future influenza pandemics an urgent priority. We have recently identified the chain-terminating broad-spectrum nucleoside analog clinical candidate 4-fluorouridine (4-FlU) and demonstrated oral efficacy against seasonal, pandemic, and highly pathogenic avian influenza viruses in the mouse and ferret model. Here, we have resistance-profiled 4-FlU against a pandemic A/CA/07/2009 (H1N1) (CA09). In vitro viral adaptation yielded six independently generated escape lineages with distinct mutations that mediated moderate resistance to 4-FlU in the genetically controlled background of recombinant CA09 (recCA09). Mutations adhered to three distinct structural clusters that are all predicted to affect the geometry of the active site of the viral RNA-dependent RNA polymerase (RdRP) complex for phosphodiester bond formation. Escape could be achieved through an individual causal mutation, a combination of mutations acting additively, or mutations functioning synergistically. Fitness of all resistant variants was impaired in cell culture, and all were attenuated in the mouse model. Oral 4-FlU administered at lowest-efficacious (2 mg/kg) or elevated (10 mg/kg) dose overcame moderate resistance when mice were inoculated with 10 LD50 units of parental or resistant recCA09, demonstrated by significantly reduced virus load and complete survival. In the ferret model, invasion of the lower respiratory tract by variants representing four adaptation lineages was impaired. Resistant variants were either transmission-incompetent, or spread to untreated sentinels was fully blocked by therapeutic treatment of source animals with 4-FlU. Author SummaryReduced sensitivity to FDA-approved influenza drugs is a major obstacle to effective antiviral therapy. We have previously demonstrated oral efficacy of a novel clinical candidate drug, 4-FlU, against seasonal, pandemic, and highly pathogenic avian influenza viruses. In this study, we have determined possible routes of influenza virus escape from 4-FlU and addressed whether resistance imposes a viral fitness penalty, affecting pathogenicity or ability to transmit. We identified three distinct clusters of mutations that lead to moderately reduced viral sensitivity to the drug. Testing of resistant variants against two chemically unrelated nucleoside analog inhibitors of influenza virus, conditionally approved favipiravir and the broad-spectrum SARS-CoV-2 drug molnupiravir, revealed cross-resistance of one cluster with favipiravir, whereas no viral escape from molnupiravir was noted. We found that the resistant variants are severely attenuated in mice, impaired in their ability to invade the lower respiratory tract and cause viral pneumonia in ferrets, and transmission-defective or compromised. We could fully mitigate lethal infection of mice with the resistant variants with standard or 5-fold elevated oral dose of 4-FlU. These results demonstrate that partial viral escape from 4-FlU is feasible in principle, but escape mutation clusters are unlikely to reach clinical significance or persist in circulating influenza virus strains.

microbiology↗

bioRxiv2022

4-Fluorouridine mitigates lethal infection with pandemic human and highly pathogenic avian influenza viruses

Influenza outbreaks are associated with substantial morbidity, mortality and economic burden. Next generation antivirals are needed to treat seasonal infections and prepare against zoonotic spillover of avian influenza viruses with pandemic potential. Having previously identified oral efficacy of the nucleoside analog 4-Fluorouridine (4-FlU, EIDD-2749) against SARS-CoV-2 and respiratory syncytial virus, we explored activity of the compound against seasonal and highly pathogenic influenza (HPAI) viruses in cell culture, human airway epithelium organoids, and/or two animal models, ferrets and mice, that assess IAV transmission and lethal viral pneumonia, respectively. 4-FlU inhibited a panel of relevant influenza A and B viruses with nanomolar potency in organoids. In vitro polymerase assays revealed immediate chain termination of IAV polymerase after 4-FlU incorporation, in contrast to delayed chain termination of SARS-CoV-2 and RSV polymerase. Once-daily oral treatment of ferrets with 2 mg/kg 4-FlU initiated 12 hours after infection rapidly stopped virus shedding and prevented direct-contact transmission to untreated sentinels. Treatment of mice infected with a lethal inoculum of pandemic A/CA/07/2009 (H1N1)pdm09 (Ca09) with 2 mg/kg 4-FlU alleviated pneumonia. Three doses mediated complete survival when treatment was initiated up to 60 hours after infection, indicating an unusually broad window for effective intervention. Therapeutic oral 4-FlU ensured survival of animals infected with HPAI A/VN/12/2003 (H5N1) and of immunocompromised mice infected with pandemic Ca09. Recoverees were fully protected against homologous reinfection. This study defines the mechanistic foundation for high sensitivity of influenza viruses to 4-FlU and supports 4-FlU as developmental candidate for the treatment of seasonal and pandemic influenza. Author SummaryNext-generation antiviral therapeutics are needed to better mitigate seasonal influenza and prepare against zoonotic virus spillover from animal reservoirs. At greatest risk are the immunocompromised and patients infected with highly pathogenic influenza viruses. In this study, we have demonstrated efficacy of a broad-spectrum nucleoside analog, 4-fluorouridine, against a representative panel of influenza viruses in cell culture, human organoids, and two animal models, ferrets and mice. Acting as an immediate chain terminator of the influenza virus polymerase, once-daily oral treatment protected against lethal infection with seasonal and highly pathogenic avian influenza viruses, prevented direct-contact transmission to untreated sentinels, and mitigated lethal infection of immunocompromised hosts. These results support the developmental potential of 4-fluorouridine for treatment of vulnerable patient groups and mitigation of pandemic influenza, providing a much-needed additional therapeutic option for improved disease management.

microbiology↗

bioRxiv2022

A novel pH-sensitive reporter reveals the cocaine-regulated trafficking of dopamine transporters in neuronal processes

The dopamine transporter (DAT) mediated DA reuptake is a major molecular mechanism for termination of dopaminergic signaling in the brain. Psychoactive substances such as cocaine act by inhibition of plasma membrane DAT function as well as by altering its expression. The precise manner and mechanism by which cocaine regulates DAT trafficking, especially at neuronal processes, are poorly understood. We have now engineered a novel pH-sensitive reporter for DAT by conjugating pHluorin to the second exofacial loop of human DAT. We show that DAT-pHluorin can be used to study DAT localization and its dynamic trafficking at neuronal processes. Using DAT-pHluorin we show that unlike neuronal soma and dendrites, which contain majority of the DATs in weakly acidic intracellular compartments, axonal DATs at both shafts and boutons are primarily (75%) localized to the plasma membrane, while varicosities contain abundant intracellular DAT within acidic intracellular structures. Using this novel reporter, we show, for the first time, that cocaine exposure leads to a brief DAT internalization followed by membrane reinsertion that lasts for days. We further show that the cocaine-induced DAT trafficking is sensitive to the activities of Synaptojanin1 phosphatase. Thus, our study using the newly engineered DAT optical reporter reveals the previously unknown dynamics and molecular regulation for cocaine-regulated DAT trafficking in neuronal processes.

neuroscience↗

bioRxiv2021

Selective estrogen receptor modulators limit alphavirus infection by targeting the viral capping enzyme nsP1

Alphaviruses cause animal or human diseases that are characterized by febrile illness, debilitating arthralgia, or encephalitis. Selective estrogen receptor modulators (SERMs), a class of FDA-approved drugs, have been shown to possess antiviral activities against multiple viruses, including Hepatitis C virus, Ebola virus, dengue virus, and vesicular stomatitis virus. Here, we evaluated three SERM compounds, namely 4-hydroxytamoxifen, tamoxifen, and clomifene, for plausible antiviral properties against two medically important alphaviruses, chikungunya virus (CHIKV) and Sindbis virus (SINV). In cell culture settings, these SERMs displayed potent activity against CHIKV and SINV at non-toxic concentrations with EC50 values ranging between 400 nM and 3.9 M. Further studies indicated that these compounds inhibit a post-entry step of the alphavirus life cycle, while enzymatic assays involving purified recombinant proteins confirmed that these SERMs target the enzymatic activity of non-structural protein 1 (nsP1), the capping enzyme of alphaviruses. Finally, tamoxifen treatment restrained CHIKV growth in the infected mice and diminished musculoskeletal pathologies. Combining biochemical, cell culture-based studies, and in vivo analyses, we strongly argue that SERM compounds, or their derivatives, may provide for attractive therapeutic options against alphaviruses.

immunology↗

bioRxiv2021

4'-Fluorouridine is a broad-spectrum orally efficacious antiviral blocking respiratory syncytial virus and SARS-CoV-2 replication

The COVID-19 pandemic has underscored the critical need for broad-spectrum therapeutics against respiratory viruses. Respiratory syncytial virus (RSV) is a major threat to pediatric patients and the elderly. We describe 4-fluorouridine (4-FlU, EIDD-2749), a ribonucleoside analog that inhibits RSV, related RNA viruses, and SARS-CoV-2 with high selectivity index in cells and well-differentiated human airway epithelia. Polymerase inhibition in in vitro RdRP assays established for RSV and SARS-CoV-2 revealed transcriptional pauses at positions i or i+3/4 post-incorporation. Once-daily oral treatment was highly efficacious at 5 mg/kg in RSV-infected mice or 20 mg/kg in ferrets infected with SARS-CoV-2 WA1/2020 or variant-of-concern (VoC) isolate CA/2020, initiated 24 or 12 hours after infection, respectively. These properties define 4-FlU as a broad-spectrum candidate for the treatment of RSV, SARS-CoV-2 and related RNA virus infections. One-Sentence Summary4-Fluorouridine is an orally available ribonucleoside analog that efficiently treats RSV and SARS-CoV-2 infections in vivo.

microbiology↗