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Immune Cell-Stratified Regulatory Contexts Associated With BMI-Related Multi-System Disease Risk: A Cell-Stratified Mendelian Randomization Study Using Single-Cell eQTL Data.

AIMS: Body mass index (BMI) is associated with multisystem disease risk, but the immune cell-specific regulatory contexts underlying BMI-related genetic associations with disease outcomes remain unclear. METHODS: We applied a cell-stratified Mendelian randomization framework integrating European-ancestry BMI GWAS data, GWAS datasets for 33 disease outcomes across five disease systems, single-cell cis-eQTL data from 28 peripheral blood immune cell types, and dynamic CD4+ T cell eQTL data. SuSiE-based colocalization was used to identify BMI-associated loci sharing causal variants with immune-cell gene expression. These variants were used as cell-stratified instruments for Mendelian randomization. RESULTS: Across 28 immune cell types, 1326 colocalized variants regulating 1426 genes were identified. In primary MR analyses, genetically predicted BMI showed Bonferroni-significant associations with 26 disease outcomes. Cell-stratified analyses identified 87 Bonferroni-significant associations across 17 disease outcomes. Cardiovascular diseases showed the broadest cell-stratified associations, followed by respiratory and metabolic diseases. CD4+ T cell regulatory contexts contributed one of the largest shares of prioritized associations, and BMI-related effects varied across CD4+ T cell activation states. Cross-disease prioritization highlighted recurrent immune feature genes, including TRAF3 and FGFR1. CONCLUSION: These findings prioritize CD4+ T cell regulatory contexts as potential immunogenetic links between BMI and multi-system disease risk, while requiring further validation in diverse populations and mechanistic models.

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SLA2 is Associated With Immune evasion and Exhaustion of CD8+ T Cells in Gastric Cancer.

The Src-like adaptor 2 (SLA2) functions as a negative regulator of T cell receptor signalling. However, its involvement in the tumour microenvironment (TME) of gastric cancer (GC) remains unexplored. In this study, we found that SLA2 expression was significantly elevated in GC tissues, and a high level of SLA2 was associated with poor prognosis in GC patients. Bioinformatics analyses revealed a close association between SLA2 and TME in GC. Single-cell RNA sequencing analysis indicated that SLA2 was significantly enriched in CD8+ T cells in GC tissues. Functional validation demonstrated that SLA2 overexpression contributed to the exhaustion of CD8+ T cells by suppressing their proliferation, upregulating the expression of exhaustion markers, reducing the secretion of effector cytokines (IFN-γ and TNF-α) and impairing cytotoxic function. SLA2 knockdown in in vitro-generated exhausted CD8 T cells significantly alleviated T cell exhaustion. Mechanistically, we found that inverse promoter methylation and active histone marks (H3K27ac, H3K4me3 and H3K4me1) may regulate SLA2 expression. Our findings suggest that SLA2 may modulate the TME and promote immune evasion via CD8+ T cell exhaustion in GC.

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Tumor-derived antioxidants suppress immunity by depriving T cells of reactive oxygen species.

Reactive oxygen species (ROS) promote genomic instability and fuel oncogenic signaling in cancer, but antioxidant therapies have so far failed to improve, or worsen, cancer outcomes. Emerging data suggest that T cells depend on ROS for signal transduction. In this study, we show that tumors exploit this dependency, releasing antioxidant enzymes into the tumor environment to suppress T cell-mediated antitumor immunity. The interstitial fluid of tumors possesses potent antioxidant activity, associated with enrichment of the antioxidant enzyme peroxiredoxin 1 (PRDX1). Extracellular PRDX1 deprives T cells of ROS, preventing oxidative inactivation of phosphatases required for T cell receptor-driven kinase signaling and effector function. Prdx1 is up-regulated upon cancer immunoediting, and loss of PRDX1 within tumors enhances antitumor immunity and immunotherapy responses. These findings define a redox-dependent mechanism of tumor immunosuppression that is potentially amenable to therapeutic intervention.

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IgA is necessary and sufficient to prevent norovirus infection in mice.

Human norovirus is the leading cause of viral gastroenteritis, yet effective vaccines and therapeutics remain elusive. Using murine norovirus as a model, we found that mucosal immunoglobulin A (IgA) is both necessary and sufficient for protection against infection, whereas CD8+ T cells are dispensable. Robust intestinal IgA production requires at least 4 weeks of enteric infection, consistent with kinetics of human norovirus RNA clearance. Systemic vaccination elicits high titers of neutralizing serum IgG but fails to prevent enteric norovirus infection, phenocopying a recent human norovirus vaccine failure. In contrast, prophylactic delivery of dimeric anti-norovirus IgA via mRNA lipid nanoparticles confers sterilizing immunity. Together, these findings define a critical role for mucosal IgA in norovirus protection and identify IgA-based treatments as a therapeutic approach for human norovirus.

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First-in-human use of recombinant IL-7 to potentiate antigen-specific T cell therapy: a single patient case study.

Clinical trials of adoptive cellular therapy demonstrate that a key characteristic associated with durable responses is in vivo expansion and persistence of transferred T cells. Strategies to develop a less differentiated, stem/memory population in the infusion product and peri-infusional regimens to promote the maintenance of desired T cell states following adoptive transfer would be desirable. Endogenous T cell therapy studies have routinely achieved memory T cells enriched for expression of interleukin (IL)-7 receptor; to eliminate the conventional requirement for immunosuppressive lymphodepletion and its attendant life-threatening toxicities, we performed the first-in-human use of IL-7 in combination with adoptively transferred antigen-specific memory CD8 T cells in a patient with refractory metastatic uveal melanoma. Single-cell immune repertoire profiling of serial peripheral blood sampling revealed substantial in vivo proliferation and expansion of a stem cell memory population in the endogenous T cell therapy product that achieved a >79% predominance of total circulating T cells by 3 weeks post-infusion in this non-lymphodepleted recipient. Although the patient's disease ultimately progressed, these findings demonstrate safety and proof of concept for an IL-7 treatment regimen for expansion of adoptively transferred T cells in vivo and induced memory differentiation in a heavily pretreated patient with refractory solid malignancy.

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An Update on Inborn Errors of V(D)J Recombination.

V(D)J recombination is the fundamental process by which developing T and B lymphocytes generate diverse antigen receptors, enabling adaptive immunity. This tightly regulated program operates exclusively in lymphoid precursors during G1 phase and depends on the lymphocyte-specific RAG1-RAG2 recombinase to introduce programmed DNA double-strand breaks at recombination signal sequences, followed by repair through the classical nonhomologous end joining (c-NHEJ) pathway. Disruption of any step in this molecular choreography compromises antigen receptor diversity and underlies a spectrum of inborn errors of immunity (IEIs), ranging from severe combined immunodeficiency (SCID) to immune dysregulation with autoimmunity and granulomatous disease. In this review, we place disorders of V(D)J recombination within the broader framework of T-cell development, detailing the temporal waves of recombinase activity, chromatin accessibility, and DNA damage responses that guide thymocyte differentiation. We discuss pathogenic variants affecting the cleavage phase [RAG1, RAG2, and the recently identified RAG cochaperone NudC domain-containing 3 (NUDCD3)], end processing (ARTEMIS), ligation and repair (LIG4, XLF, XRCC4, PRKDC), and genome surveillance pathways (ATM, MRN complex, RNF168), highlighting genotype-phenotype correlations and mechanisms driving immune deficiency and dysregulation. We briefly review recent diagnostic advances, including newborn screening using T-cell receptor excision circles, repertoire sequencing, and functional assays, alongside current therapeutic strategies. Finally, we outline key unanswered questions and argue that continued integration of clinical observation with molecular discovery is essential to improve outcomes and deepen understanding of adaptive immune development.

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A Phase II Feasibility Study Combining Pembrolizumab and Metformin in Patients with Metastatic Head and Neck Cancer.

PURPOSE: Survival for recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) remains low with <20% immunotherapy response. Metformin increases tumor-infiltrating CD8+ T and natural killer (NK) cells, which harbor PD-1. In this phase II clinical trial (NCT04414540), we combined metformin and pembrolizumab to evaluate the overall response rate (ORR) in R/M HNSCC and assess NK-cell activity. PATIENTS AND METHODS: Eligible patients were randomized 1:1 into two arms: (i) metformin extended-release (ER) dose escalation to 2,000 mg over 14 days followed by combination with pembrolizumab 200 mg every 3 weeks or (ii) pembrolizumab 200 mg every 3 weeks followed by combination with metformin ER 2,000 mg daily. The primary endpoint was ORR per RECIST 1.1. Nineteen evaluable patients were planned to estimate the proportion of approximately 32% ORR. Safety was evaluated according to Common Terminology Criteria for Adverse Events v5.0. The distribution, activation, and cytotoxic function of NK cells were analyzed via flow cytometry. RESULTS: Twenty-one patients were enrolled; 76% were male, 52% were smokers, and the median age was 64 years. Ten patients had oropharyngeal tumors, of which nine were p16+. Eighteen patients were evaluable for response, including four complete and five partial responses for an ORR of 50% [95% confidence interval (29-71)]. Combination therapy was well tolerated with no unexpected adverse events (AE). Five grade 3 AEs occurred: nausea, diarrhea, fatigue, and weight loss. Metformin led to increased peripheral NK-cell maturation and cytotoxic ability. CONCLUSIONS: The combination of metformin and pembrolizumab was well tolerated with mild gastrointestinal AEs and promising activity, warranting further investigation in a randomized trial.

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CAR T Cells Targeting an Intracellular Leukemia Antigen Promiscuously Presented by Diverse HLA-II Alleles.

UNLABELLED: Chimeric antigen receptor (CAR) technology has revolutionized B-cell malignancy treatment by enabling T cells to effectively recognize and target lineage-specific surface antigens. However, CAR T cells show limited efficacy against myeloid neoplasms and solid tumors due to challenges in identifying suitable surface targets. In this study, we present a CAR targeting the intracellular WT1 oncoprotein, cross-presented by surface HLA class II (HLA-II) alleles. WT1-CAR T cells, derived from an antibody raised solely against a WT1 peptide, recognized the WT1330-348 peptide promiscuously presented by 18 out of 20 tested HLA-II alleles, overcoming traditional HLA restrictions. WT1-CAR T cells specifically recognized leukemic cells in a WT1- and HLA-II-dependent manner and mediated an antitumor response in vitro and in vivo. This approach broadens CAR-targetable antigens beyond traditional HLA restrictions and offers a promising therapeutic option to a wide and genetically diverse patient population. SIGNIFICANCE: Leveraging the promiscuous binding of HLA-II-peptide complexes, we developed a CAR T-cell approach targeting an intracellular oncoprotein WT1 presented across diverse HLA-II families. Our study establishes a framework for CAR therapies against intracellular antigens, extending potential CAR T-cell applications to new cancer types and patient populations.

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A stromal platform for robust expansion of functional IL-10-producing B cells for immune regulation.

IL-10-producing B cells exert immunosuppressive effects, yet their low abundance and poor in vitro viability have limited their therapeutic application. Here, we developed a stromal coculture system using MS5 cells engineered to express human CD40L, BAFF, and IFN-&#x3b2;1 (MS5-3F, for "3 factors"), which enables robust induction and greater than 1000-fold expansion of human IL-10-producing B cells. The expanded cells showed phenotypic and transcriptional profiles characteristic of unswitched (IgM+) plasmablasts and potently suppressed CD4+ T cell proliferation in an IL-10-dependent manner. MS5-3F-expanded B cells also increased the frequency of regulatory T cells in vitro, an effect that was not abrogated by IL-10/IL-10R blockade, suggesting contributions from additional mechanisms. IL-10 production originated predominantly from naive B cells, rather than memory B cells. Furthermore, B cells from patients with systemic lupus erythematosus, despite impaired IL-10 production under conventional conditions, were efficiently differentiated into IL-10-producing B cells using this system. The expanded cells showed minimal IgG-secreting output. Our platform offers a scalable strategy for generating human regulatory B cells, laying the foundation for B cell-based immunotherapies.

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Distinct immune landscapes characterize highly versus minimally invasive brain metastases.

Brain metastases (BrMs) occur in approximately 30% of cancer patients, causing nearly one-fifth of cancer deaths. While immune checkpoint inhibitors (ICIs) benefit some BrM patients, responses remain highly variable. This variability partly reflects distinct histopathological growth patterns that include minimally invasive (MI) and highly invasive (HI) brain BrMs. Here we show that MI BrMs exhibit robust immune infiltration, whereas HI lesions are immunosuppressed. However, histological differentiation between MI and HI can be challenging because of subjective margin assessment. Here, using highly multiplexed spatial proteomics on 119 tumor sections from 46 patients with BrMs, we identify CHI3L1 as a key mediator of the immunosuppressive microenvironment in HI BrMs. In preclinical models, genetic deletion of CHI3L1 converts immune-cold metastases into lymphocyte-rich, ICI-responsive lesions infiltrated by granzyme B+ CD8+ T cells. In BrM patients treated with ICI, immunohistochemical quantification of CHI3L1 expression was a stronger predictor of ICI response than traditional MI/HI classification. Thus, CHI3L1 represents a promising biomarker and therapeutic target for BrMs.

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Th2 skewing in patients with disseminated coccidioidomycosis.

BACKGROUNDDisseminated coccidioidomycosis (DCM) is an often fatal and otherwise intractable condition requiring lifelong antifungal treatment. We have previously shown that a deranged polarization of CD4+ T cells toward a Th2 phenotype can exist in the context of DCM. Here, we studied a large population to determine the frequency of abnormal Th2 skewing of CD4+ T cells in patients with coccidioidomycosis and to identify underlying genetic mechanisms supporting this phenotype.METHODSWe collected PBMCs from 204 patients with coccidioidomycosis, including 96 patients with disseminated disease. We measured immune phenotypes and cytokine production by CD4+ T cells from patients and healthy controls, and comparisons between groups were made based on disease severity and demographics. Whole-genome sequencing was conducted on 180 individuals who also had cytokine profiling.RESULTSWe found that approximately 25% of patients with DCM had a CD4+ T cell compartment that was abnormally skewed toward a Th2 phenotype, and Th2 skewing was highly correlated with male sex. Coculture of T cells with the IL-4R/IL-13R-blocking antibody dupilumab reduced Th2 skewing. Sequencing revealed rare variants in genes involved in the IL-12/IFN-&#x3b3; axis in several Th2-skewed patients, and we validated one such variant in IFNGR1 as hypomorphic.CONCLUSIONPatients with DCM, especially males, should be screened for Th2 skewing of CD4+ T cells. Patients with Th2 skewing should be additionally screened for genetic defects in the IL-12/IFN-&#x3b3; axis. Our findings give a mechanistic rationale for blockade of IL-4R in Th2-skewed patients with refractory coccidioidomycosis.FUNDINGNational Institute of Allergy and Infectious Diseases/NIH grants R21 AI149654 and U19 AI166059 and University of California Office of the President grant VFR-19-633386.

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Benchmarking urinary cell transcriptomes for noninvasive differentiation of BK polyomavirus-associated nephropathy from T cell-mediated rejection.

BK polyomavirus-associated nephropathy (BKVN) adversely impacts kidney allograft survival and often mimics acute T cell-mediated rejection (TCMR), confounding diagnosis and management. To address this conundrum, we performed unbiased RNA sequencing of urinary cells matched to biopsies classified as BKVN with intragraft inflammation (BKVN-P), BKVN without inflammation (BKVN-N), TCMR, or no rejection (NR). BKVN-N displayed dominant host DNA replication, cell cycle, and repair programs, while BKVN-P samples exhibited expansive innate immune activation, antigen presentation, chemokine upregulation, and epithelial injury. Both BKVN subtypes shared signatures of T cell exhaustion and mature and tolerogenic dendritic cell activation but differed in immune orientation - Th1 predominance in BKVN-N versus Treg and CD8 enrichment in BKVN-P. Compared with TCMR samples, BKVN-P lacked robust TCR/CD28 signaling and was enriched for viral and innate modules; BKVN-N lacked alloimmune activation. B cell exhaustion characterized BKVN-N, while BKVN-P displayed robust B cell activation with metabolic downregulation. A ratiometric urinary cell biomarker, CXCL10 mRNA/CD3E mRNA, distinguished both BKVN subtypes from TCMR with diagnostic accuracy, replicated by quantitative reverse transcription PCR for clinical translation, and confirmed in an independent cohort. These findings demonstrate the utility of urinary cell transcriptomics for resolving viral injury from alloimmunity, enabling precision diagnostics and targeted immunomodulation in kidney transplantation.

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Longitudinal clinical proteomics reveals pneumonia type-specific protein biomarkers and autoantibodies.

Community-acquired pneumonia is a major cause of morbidity and mortality globally. Specific molecular endotypes are currently not well defined, and different viral or bacterial pathogens may trigger specific host responses and pathogenic mechanisms. We performed longitudinal proteomic profiling of bronchoalveolar lavage fluid and plasma from bacterial, influenza, and SARS-CoV-2-driven pneumonia. Our analysis revealed highly pneumonia type-specific proteomic signatures, including COVID-19-specific antibodies locally produced in the lung. These antibodies showed biased immunoglobulin V-domain usage, linked to a CD69/CD83 plasma cell state associated with disease severity and degree of autoimmunity. Using mass spectrometry-driven autoantibody profiling in 2 independent COVID-19 cohorts, we identified 177 putative autoantibodies targeting extracellular matrix, nuclear, and immune-related proteins. Of note, temporal changes in autoantibody profiles correlated with clinical markers of inflammation, organ dysfunction, and duration of hospitalization. These findings highlight the autoimmune aspects of COVID-19 and provide potential biomarkers and therapeutic targets to help improve patient outcomes.

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CAR-T Cell Therapy: Manufacturing Platforms and Clinical Consequences.

Chimeric antigen receptor (CAR) T-cell therapy has transformed hematological cancer care, yet variability in efficacy, durability, and safety cannot be explained solely by antigen selection or patient factors. We propose that manufacturing platforms are active biological determinants of outcome. Viral vectors, used in all licensed products, provide stable genomic integration and durable expression but are limited by cost, cargo capacity, and centralized production. Nonviral strategies, including transposons, CRISPR knock-ins, and messenger RNA delivery, enable faster, less-expensive manufacturing with larger payloads, while introducing distinct safety and persistence profiles. This review presents a three-layer mechanistic framework that reframes manufacturing as biology: integration biology determines genomic risk and transgene stability; clonal fitness shapes persistence, dominance, and exhaustion; and epigenomic imprinting, influenced by gene transfer method, cytokines, and culture stress, preconfigures functional trajectories. Clinical observations link platform choice to immune recovery, where prolonged B-cell aplasia and delayed T-cell reconstitution contribute to infection-related nonrelapse mortality, and hematopoietic reserve at apheresis emerges as a practical predictor. Finally, manufacturing is positioned as the key to democratizing cell therapy. Decentralized, nonviral production aligned with regulatory standards may enable equitable access and transition CAR-T therapy from innovation to sustainable global care.

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A modular &#x3b3;&#x3b4; TCR-T platform combining KRAS pMHC targeting with re-dosable mRNA engager redirection.

Solid tumors often evade TCR-engineered &#x3b1;&#x3b2; T cells when antigen expression varies or when the restricting Human Leukocyte Antigen (HLA) allele is lost. &#x3b3;&#x3b4; T cells, in contrast, detect cellular dysregulation through non-peptide/Major Histocompatibility Complex (MHC) cues, including phosphoantigens and stress ligands, and can be developed as allogeneic therapies. Although intratumoral &#x3b3;&#x3b4; T cell signatures are associated with improved outcome across cancers, &#x3b3;&#x3b4; recognition itself is broad and still selected within the thymus just as &#x3b1;&#x3b2; T cell receptors (TCRs) are. It does not, however, anchor specificity to a defined driver-mutation pMHC epitope. We therefore asked whether a high-affinity, co-receptor-independent &#x3b1;&#x3b2; TCR could graft oncogenic-driver specificity onto &#x3b3;&#x3b4; T cells while leaving the endogenous &#x3b3;&#x3b4; TCR intact. We knocked the KRASG12V/HLA-A*11:01 TCR A11v into primary human &#x3b3;&#x3b4; T cells. Engineered cells co-expressed the transgenic &#x3b1;&#x3b2; TCR and the endogenous &#x3b3;&#x3b4; TCR and lysed KRASG12V/HLA-A*11:01+ tumor cells in vitro and in vivo. To cover potential resistance through loss of HLA-A*11:01, we delivered an mRNA lipid nanoparticle (LNP) encoding a secreted mesothelin&#xd7;CD3 (M5) bispecific T cell engager (TCE). LNP-M5 produced circulating TCE that redirected &#x3b3;&#x3b4; A11v T cells and polyclonal bystander T cells to kill mesothelin+ targets, accompanied by development of higher &#x3b3;&#x3b4; A11v T cell counts in vivo. In humanized mice bearing mixed HLA-A*11:01+ and HLA-A*11:01&#x2009;-&#x2009;KRASG12V tumors, &#x3b3;&#x3b4; A11v T cells produced transient control, whereas adding LNP-M5 yielded complete responses and prolonged survival. Thus, this two-part therapy couples invariant driver targeting to tunable redirection and addresses loss of the restricting HLA allele, a central escape route for TCR-based therapy. It provides an off-the-shelf reagent to enable KRAS-anchored treatment with the ability to redeliver the reagent.

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A Functionally Constrained Immune Ecosystem in Microsatellite-stable Colorectal Cancer Resolved by Single-cell and Exome Profiling.

BACKGROUND/AIM: Microsatellite-stable (MSS) colorectal cancer (CRC) generally responds poorly to immune checkpoint blockade, but some MSS tumors are T-cell rich. We examined whether such infiltration reflected effective immunity or functional immune constraint. CASE REPORT: A 77-year-old woman underwent resection of a mismatch repair-proficient (pMMR), MSS, low-mutational-burden CRC with a synchronous adenoma. Whole-exome sequencing of tumor, adenoma and adjacent normal tissue detected no shared high-confidence somatic mutations between tumor and adenoma within the sensitivity of this WES analysis and identified tumor-specific APC, KRAS and TP53 alterations. Tumor single-cell RNA sequencing yielded 7,569 cells, with T-lineage populations comprising 83.5%. Cytotoxic T cells showed cytolytic and dysfunction-associated features, regulatory T cells (Tregs) showed suppressive remodeling, and Th17 cells showed inflammatory/profibrotic programs. CellChat nominated stromal MIF/FN1-CD74/CD44 and extracellular-matrix communication with T-cell compartments. CONCLUSION: This molecular case report shows that T-cell abundance and immune effectiveness can be uncoupled in MSS CRC.

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Chimeric vaccine based on Iraqi HLA alleles against a predominant local Escherichia coli phylogroup.

INTRODUCTION: Escherichia coli remains amongst the most globally important pathogens implicated in severe clinical manifestations. The progressive rise in multidrug-resistant strains highlights the urgent need for new vaccines. Therefore, this study was designed to develop a new multi-epitope vaccine containing the most conserved epitopes across E. coli pathotypes. Consequently, the study aimed to investigate the immunoadjuvant role of faecal microbiota transplantation in enhancing vaccine efficacy. METHODS: Eighteen of the most conserved B-cell and T-cell epitopes of FimH, LptD, and BamA proteins were selected and included in a single construct. During the epitope selection process, HLA alleles predominant in the Iraqi population, as reported in previous studies, were used as criteria for selecting T-cell epitopes. The chimeric protein was expressed in BL21 E. coli and purified using affinity chromatography. Vaccine cross-protective immunity and protection were tested in in vivo experiments. Different formulations were used in the experimental evaluation: three doses of 100 &#x3bc;g of purified chimeric protein, injected intraperitoneally alone or encapsulated in PLGA nanoparticles, after faecal microbiota transplantation with and without gut microbiota modulation mediated by a cocktail of antibiotics. IgG1, IL-4, INF-&#x3b3;, and NLRP3 levels were measured at 30 and 75 days after the first immunisation dose. Immunised mice were challenged with the local B2 UPEC phylogroup, and protection efficacy was considered 48&#xa0;h later. Finally, the histological effects of the different chimeric protein formulations on the liver were assessed. RESULTS: All vaccine formulations except those after faecal microbiota transplantation without gut microbiota modulation induce significant increases in IgG1, IL-4, and INF-&#x3b3; levels at different times. Only vaccination after faecal microbiota transplantation with gut microbiota modulation elicited robust NLRP3 levels at 30 and 75 days after, and this was linked to the highest reduction in bladder bacterial load by 813-fold compared to the other formulations, as well as the mildest effect on liver histological changes. DISCUSSION: These results demonstrated that the chimeric vaccine provides preliminary protection against a local B2 UPEC isolate. Furthermore, modulating gut microbiota via faecal transplantation markedly enhances the immunogenicity and protective efficacy of vaccination, suggesting its adjuvanticity.

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Pre-treatment T cell features and immune-milieu characteristics shape treatment-induced exhaustion and resistance to Blinatumomab in B-cell acute lymphoblastic leukemia.

BACKGROUND: Blinatumomab (Blina), a CD19&#xd7;CD3 bispecific T cell engager, is approved for the treatment of B-cell precursor acute lymphoblastic leukemia (BCP-ALL), yet resistance remains a major challenge and the mechanisms driving treatment failure remain poorly understood. METHODS: To define the immunological determinants of resistance, we performed longitudinal profiling of peripheral blood T cells and the immune milieu of 34 patients receiving Blina using flow cytometry (n=19), single-cell CITE-seq (n=13), ex vivo Blina-induced cytotoxicity (n=26) and serum proteomics (n=17). RESULTS: At baseline, Responders (R) were enriched for CD8+ effector memory T cells (TEM) expressing higher levels of cytotoxic genes and their transcriptional regulator ZNF683. Conversely, CD8+ TEM from Non-Responders (NR) displayed transcriptional features of activation without proportionate cytotoxic commitment. Over the course of the first treatment cycle, NR exhibited a progressive expansion of TIM3+CD8+ T cells that correlated with a rapid loss of ex vivo cytotoxic function. Linking baseline state to post-treatment T-cell exhaustion, the magnitude of TIM3+CD8+ expansion correlated inversely with baseline ZNF683 expression in CD8+TEM. Beyond T-cell-intrinsic features, NR harbored an immunosuppressive milieu characterized by higher circulating levels of M2-polarizing factors (CSF-1, HGF) and the TIM-3 ligand Galectin-9, which correlated positively with the magnitude of TIM3+CD8+ T-cell expansion. CONCLUSIONS: These findings indicate that post-Blina CD8+ T-cell exhaustion is associated with resistance and it is shaped by both reduced ZNF683-dependent cytotoxic programming in CD8+ TEM and an immunosuppressive milieu. This provides a rationale for risk stratification based on baseline transcriptional profiling of CD8+ TEM and for combinatorial strategies targeting the suppressive microenvironment.

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