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IntroductionSepsis engenders distinct host immunologic changes that include the expansion of myeloid-derived suppressor cells (MDSCs). These cells play a physiologic role in tempering acute inflammatory responses but can persist in patients who develop chronic critical illness.MethodsCellular Indexing of Transcriptomes and Epitopes by Sequencing and transcriptomic analysis are used to describe MDSC subpopulations based on differential gene expression,RNA velocities,and biologic process clustering.ResultsWe identify a unique lineage and differentiation pathway for MDSCs after sepsis and describe a novel MDSC subpopulation. Additionally,we report that the heterogeneous response of the myeloid compartment of blood to sepsis is dependent on clinical outcome.DiscussionThe origins and lineage of these MDSC subpopulations were previously assumed to be discrete and unidirectional; however,these cells exhibit a dynamic phenotype with considerable plasticity. View Publication

Innate antiviral factors are essential for effective defense against viral pathogens. However,the identity of major restriction mechanisms remains elusive. Current approaches to discover antiviral factors usually focus on the initial steps of viral replication and are limited to a single round of infection. Here,we engineered libraries of >1500 replication-competent HIV-1 constructs each expressing a single gRNAs to target >500 cellular genes for virus-driven discovery of antiviral factors. Passaging in CD4+ T cells robustly enriched HIV-1 encoding sgRNAs against GRN,CIITA,EHMT2,CEACAM3,CC2D1B and RHOA by >50-fold. Using an HIV-1 library lacking the accessory nef gene,we identified IFI16 as a Nef target. Functional analyses in cell lines and primary CD4+ T cells support that the HIV-driven CRISPR screen identified restriction factors targeting virus entry,transcription,release and infectivity. Our HIV-guided CRISPR technique enables sensitive discovery of physiologically relevant cellular defense factors throughout the entire viral replication cycle. Innate immune mechanisms are critical for antiviral defense. Here,the authors developed a CRISPR/Cas9-based HIV-driven approach to identify cellular factors compromising viral transcription,assembly,release or infectivity in human T cells. They identify targets of the Nef protein as antiviral factors. View Publication

Gene silencing without gene editing holds great potential for the development of safe therapeutic applications. Here,we describe a novel strategy to concomitantly repress multiple genes using zinc finger proteins fused to Krüppel-Associated Box repression domains (ZF-Rs). This was achieved via the optimization of a lentiviral system tailored for the delivery of ZF-Rs in hematopoietic cells. We showed that an optimal design of the lentiviral backbone is crucial to multiplex up to three ZF-Rs or two ZF-Rs and a chimeric antigen receptor. ZF-R expression had no impact on the integrity and functionality of transduced cells. Furthermore,gene repression in ZF-R-expressing T cells was highly efficient in vitro and in vivo during the entire monitoring period (up to 10 weeks),and it was accompanied by epigenetic remodeling events. Finally,we described an approach to improve ZF-R specificity to illustrate the path toward the generation of ZF-Rs with a safe clinical profile. In conclusion,we successfully developed an epigenetic-based cell engineering approach for concomitant modulation of multiple gene expressions that bypass the risks associated with DNA editing. Graphical abstract David Fenard and colleagues developed a lentiviral backbone for the multiplexing of up to three ZF-R sequences,allowing an efficient,stable,and specific epigenetic control of multiple genes in T cells or Tregs after a single lentiviral transduction event. View Publication

Manufacturing chimeric antigen receptor (CAR) T cell therapies is complex,with limited understanding of how medium composition impacts T cell phenotypes. CRISPR-Cas9 ribonucleoproteins can precisely insert a CAR sequence while disrupting the endogenous T cell receptor alpha constant (TRAC) gene resulting in TRAC-CAR T cells with an enriched stem cell memory T cell population,a process that could be further optimized through modifications to the medium composition. In this study we generated anti-GD2 TRAC-CAR T cells using "metabolic priming" (MP),where the cells were activated in glucose/glutamine-low medium and then expanded in glucose/glutamine-high medium. T cell products were evaluated using spectral flow cytometry,metabolic assays,cytokine production,cytotoxicity assays in vitro,and potency against human GD2+ xenograft neuroblastoma models in vivo. Compared with standard TRAC-CAR T cells,MP TRAC-CAR T cells showed less glycolysis,higher CCR7/CD62L expression,more bound NAD(P)H activity,and reduced IFN-γ,IL-2,IP-10,IL-1β,IL-17,and TGF-β production at the end of manufacturing ex vivo,with increased central memory CAR T cells and better persistence observed in vivo. MP with medium during CAR T cell biomanufacturing can minimize glycolysis and enrich memory phenotypes ex vivo,which could lead to better responses against solid tumors in vivo. Graphical abstract Cappabianca and colleagues manufactured virus-free CAR T cells at scale with CRISPR-Cas9 and “metabolically primed” them by attenuating activation in low-glucose/glutamine medium with expansion in high-glucose/glutamine medium. Priming made CAR T cells with increased stem cell memory properties,including enriched central memory phenotypes in vivo while lysing solid tumors. View Publication

A major limitation of chimeric antigen receptor (CAR) T cell therapies is the poor persistence of these cells in vivo1. The expression of memory-associated genes in CAR T cells is linked to their long-term persistence in patients and clinical efficacy2–6,suggesting that memory programs may underpin durable CAR T cell function. Here we show that the transcription factor FOXO1 is responsible for promoting memory and restraining exhaustion in human CAR T cells. Pharmacological inhibition or gene editing of endogenous FOXO1 diminished the expression of memory-associated genes,promoted an exhaustion-like phenotype and impaired the antitumour activity of CAR T cells. Overexpression of FOXO1 induced a gene-expression program consistent with T cell memory and increased chromatin accessibility at FOXO1-binding motifs. CAR T cells that overexpressed FOXO1 retained their function,memory potential and metabolic fitness in settings of chronic stimulation,and exhibited enhanced persistence and tumour control in vivo. By contrast,overexpression of TCF1 (encoded by TCF7) did not enforce canonical memory programs or enhance the potency of CAR T cells. Notably,FOXO1 activity correlated with positive clinical outcomes of patients treated with CAR T cells or tumour-infiltrating lymphocytes,underscoring the clinical relevance of FOXO1 in cancer immunotherapy. Our results show that overexpressing FOXO1 can increase the antitumour activity of human CAR T cells,and highlight memory reprogramming as a broadly applicable approach for optimizing therapeutic T cell states. The transcription factor FOXO1 has a key role in human T cell memory,and manipulating FOXO1 expression could provide a way to enhance CAR T cell therapies by increasing CAR T cell persistence and antitumour activity. View Publication

IntroductionB-cell activation triggers the release of endoplasmic reticulum calcium stores through the store-operated calcium entry (SOCE) pathway resulting in calcium influx by calcium release-activated calcium (CRAC) channels on the plasma membrane. B-cell-specific murine knockouts of SOCE do not impact humoral immunity suggesting that alternative channels may be important.MethodsWe identified a member of the calcium-permeable transient receptor potential (TRP) ion channel family,TRPV5,as a candidate channel expressed in B cells by a quantitative polymerase chain reaction (qPCR) screen. To further investigate the role of TRPV5 in B-cell responses,we generated a murine TRPV5 knockout (KO) by CRISPR–Cas9. ResultsWe found TRPV5 polarized to B-cell receptor (BCR) clusters upon stimulation in a PI3K–RhoA-dependent manner. TRPV5 KO mice have normal B-cell development and mature B-cell numbers. Surprisingly,calcium influx upon BCR stimulation in primary TRPV5 KO B cells was not impaired; however,differential expression of other calcium-regulating proteins,such as ORAI1,may contribute to a compensatory mechanism for calcium signaling in these cells. We demonstrate that TRPV5 KO B cells have impaired spreading and contraction in response to membrane-bound antigen. Consistent with this,TRPV5 KO B cells have reduced BCR signaling measured through phospho-tyrosine residues. Lastly,we also found that TRPV5 is important for early T-dependent antigen specific responses post-immunization. DiscussionThus,our findings identify a role for TRPV5 in BCR signaling and B-cell activation. View Publication

AbstractLong single-stranded DNA (ssDNA) is a versatile molecular reagent with applications including RNA-guided genome engineering and DNA nanotechnology,yet its production is typically resource-intensive. We introduce a novel method utilizing an engineered Escherichia coli ‘helper’ strain and phagemid system that simplifies long ssDNA generation to a straightforward transformation and purification procedure. Our method obviates the need for helper plasmids and their associated contamination by integrating M13mp18 genes directly into the E. coli chromosome. We achieved ssDNA lengths ranging from 504 to 20 724 nt with titers up to 250 μg/l following alkaline lysis purification. The efficacy of our system was confirmed through its application in primary T-cell genome modifications and DNA origami folding. The reliability,scalability and ease of our approach promise to unlock new experimental applications requiring large quantities of long ssDNA. Graphical Abstract Graphical Abstract View Publication

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by anti-nuclear autoantibodies whose production is promoted by autoreactive T follicular helper (TFH) cells. During SLE pathogenesis,basophils accumulate in secondary lymphoid organs (SLO),amplify autoantibody production and disease progression through mechanisms that remain to be defined. Here,we provide evidence for a direct functional relationship between TFH cells and basophils during lupus pathogenesis,both in humans and mice. PD-L1 upregulation on basophils and IL-4 production are associated with TFH and TFH2 cell expansions and with disease activity. Pathogenic TFH cell accumulation,maintenance,and function in SLO were dependent on PD-L1 and IL-4 in basophils,which induced a transcriptional program allowing TFH2 cell differentiation and function. Our study establishes a direct mechanistic link between basophils and TFH cells in SLE that promotes autoantibody production and lupus nephritis. Basophils have been implicated in systemic lupus erythematosus (SLE),as evidenced by the fact that basophil-deficient mice do not develop the disease. Here,the authors demonstrate that PD-L1 and IL-4 expression in basophils promotes the pathogenic accumulation of follicular helper T cells in patients with SLE and murine models. View Publication

AbstractPolysialic acid (polySia) is a linear polymer of α2,8-linked sialic acid residues that is of fundamental biological interest due to its pivotal roles in the regulation of the nervous,immune,and reproductive systems in healthy human adults. PolySia is also dysregulated in several chronic diseases,including cancers and mental health disorders. However,the mechanisms underpinning polySia biology in health and disease remain largely unknown. The polySia-specific hydrolase,endoneuraminidase NF (EndoN),and the catalytically inactive polySia lectin EndoNDM,have been extensively used for studying polySia. However,EndoN is heat stable and remains associated with cells after washing. When studying polySia in systems with multiple polysialylated species,the residual EndoN that cannot be removed confounds data interpretation. We developed a strategy for site-specific immobilization of EndoN on streptavidin-coated magnetic beads. We showed that immobilizing EndoN allows for effective removal of the enzyme from samples,while retaining hydrolase activity. We used the same strategy to immobilize the polySia lectin EndoNDM,which enabled the enrichment of polysialylated proteins from complex mixtures such as serum for their identification via mass spectrometry. We used this methodology to identify a novel polysialylated protein,QSOX2,which is secreted from the breast cancer cell line MCF-7. This method of site-specific immobilization can be utilized for other enzymes and lectins to yield insight into glycobiology. View Publication

Heat shock protein 90 (Hsp90) is a molecular chaperone important for maintaining protein homeostasis (proteostasis) in the cell. Hsp90 inhibitors are being explored as cancer therapeutics because of their ability to disrupt proteostasis. Inhibiting Hsp90 increases surface density of the immunological receptor Major Histocompatibility Complex 1 (MHC1). Here we show that this increase occurs across multiple cancer cell lines and with both cytosol-specific and pan-Hsp90 inhibitors. We demonstrate that Hsp90 inhibition also alters surface expression of both IFNGR and PD-L1,two additional immunological receptors that play a significant role in anti-tumour or anti-immune activity in the tumour microenvironment. Hsp90 also negatively regulates IFN-γ activity in cancer cells,suggesting it has a unique role in mediating the immune system’s response to cancer. Our data suggests a strong link between Hsp90 activity and the pathways that govern anti-tumour immunity. This highlights the potential for the use of an Hsp90 inhibitor in combination with another currently available cancer treatment,immune checkpoint blockade therapy,which works to prevent immune evasion of cancer cells. Combination checkpoint inhibitor therapy and the use of an Hsp90 inhibitor may potentiate the therapeutic benefits of both treatments and improve prognosis for cancer patients. View Publication