Altered ontogeny and transcriptomic signatures of tissue-resident pulmonary interstitial macrophages ameliorate allergic airway hyperresponsiveness.

Introduction: Environmental exposures and experimental manipulations can alter the ontogenetic composition of tissue-resident macrophages. However, the impact of these alterations on subsequent immune responses, particularly in allergic airway diseases, remains poorly understood. This study aims to elucidate the significance of modified macrophage ontogeny resulting from environmental exposures on allergic airway responses to house dust mite (HDM) allergen. Methods: We utilized embryonic lineage labeling to delineate the ontogenetic profile of tissue-resident macrophages at baseline and following the resolution of repeated lipopolysaccharide (LPS)-induced lung injury. We investigated differences in house dust mite (HDM)-induced allergy to assess the influence of macrophage ontogeny on allergic airway responses. Additionally, we employed single-cell RNA sequencing (scRNAseq) and immunofluorescent staining to characterize the pulmonary macrophage composition, associated pathways, and tissue localization. Results: Our findings demonstrate that the ontogeny of homeostatic alveolar and interstitial macrophages is altered after the resolution from repeated LPS-induced lung injury, leading to the replacement of embryonic-derived by bone marrow-derived macrophages. This shift in macrophage ontogeny is associated with reduced HDM-induced allergic airway responses. Through scRNAseq and immunofluorescent staining, we identified a distinct subset of resident-derived interstitial macrophages expressing genes associated with allergic airway diseases, localized adjacent to terminal bronchi, and diminished by prior LPS exposure. Discussion: These results suggest a pivotal role for pulmonary macrophage ontogeny in modulating allergic airway responses. Moreover, our findings highlight the implications of prior environmental exposures in shaping future immune responses and influencing the development of allergies. By elucidating the mechanisms underlying these phenomena, this study provides valuable insights into potential therapeutic targets for allergic airway diseases and avenues for further research into immune modulation and allergic disease prevention.

Recapitulation of human pathophysiology and identification of forensic biomarkers in a translational model of chlorine inhalation injury.

Chlorine gas (Cl2) has been repeatedly used as a chemical weapon, first in World War I and most recently in Syria. Life-threatening Cl2 exposures frequently occur in domestic and occupational environments, and in transportation accidents. Modeling the human etiology of Cl2-induced acute lung injury (ALI), forensic biomarkers, and targeted countermeasures development have been hampered by inadequate large animal models. The objective of this study was to develop a translational model of Cl2-induced ALI in swine to understand toxico-pathophysiology and evaluate whether it is suitable for screening potential medical countermeasures and to identify biomarkers useful for forensic analysis. Specific pathogen-free Yorkshire swine (30-40 kg) of either sex were exposed to Cl2 (≤240 ppm for 1 h) or filtered air under anesthesia and controlled mechanical ventilation. Exposure to Cl2 resulted in severe hypoxia and hypoxemia, increased airway resistance and peak inspiratory pressure, and decreased dynamic lung compliance. Cl2 exposure resulted in increased total leucocyte and neutrophil counts in bronchoalveolar lavage fluid, vascular leakage, and pulmonary edema compared with the air-exposed group. The model recapitulated all three key histopathological features of human ALI, such as neutrophilic alveolitis, deposition of hyaline membranes, and formation of microthrombi. Free and lipid-bound 2-chlorofatty acids and chlorotyrosine-modified proteins (3-chloro-l-tyrosine and 3,5-dichloro-l-tyrosine) were detected in plasma and lung tissue after Cl2 exposure. In this study, we developed a translational swine model that recapitulates key features of human Cl2 inhalation injury and is suitable for testing medical countermeasures, and validated chlorinated fatty acids and protein adducts as biomarkers of Cl2 inhalation.NEW & NOTEWORTHY We established a swine model of chlorine gas-induced acute lung injury that exhibits several features of human acute lung injury and is suitable for screening potential medical countermeasures. We validated chlorinated fatty acids and protein adducts in plasma and lung samples as forensic biomarkers of chlorine inhalation.

Antigen-loaded Monocyte Administration and Flt3 Ligand Augment the Antitumor Efficacy of Immune Checkpoint Blockade in a Murine Melanoma Model.

Undifferentiated monocytes can be loaded with tumor antigens (Ag) and administered intravenously to induce antitumor cytotoxic T lymphocyte (CTL) responses. This vaccination strategy exploits an endogenous Ag cross-presentation pathway, where Ag-loaded monocytes (monocyte vaccines) transfer their Ag to resident splenic dendritic cells (DC), which then stimulate robust CD8 + CTL responses. In this study, we investigated whether monocyte vaccination in combination with CDX-301, a DC-expanding cytokine Fms-like tyrosine kinase 3 ligand (Flt3L), could improve the antitumor efficacy of anti-programmed cell death (anti-PD-1) immune checkpoint blockade. We found that Flt3L expanded splenic DC over 40-fold in vivo and doubled the number of circulating Ag-specific T cells when administered before monocyte vaccination in C57BL/6 mice. In addition, OVA-monocyte vaccination combined with either anti-PD-1, anti-programmed cell death ligand 1 (anti-PD-L1), or anti-cytotoxic T lymphocyte antigen-4 (anti-CTLA-4) suppressed subcutaneous B16/F10-OVA tumor growth to a greater extent than checkpoint blockade alone. When administered together, OVA-monocyte vaccination improved the antitumor efficacy of Flt3L and anti-PD-1 in terms of circulating Ag-specific CD8 + T cell frequency and inhibition of subcutaneous B16/F10-OVA tumor growth. To our knowledge, this is the first demonstration that a cancer vaccine strategy and Flt3L can improve the antitumor efficacy of anti-PD-1. The findings presented here warrant further study of how monocyte vaccines can improve Flt3L and immune checkpoint blockade as they enter clinical trials.

CD8+ T cells maintain killing of MHC-I-negative tumor cells through the NKG2D-NKG2DL axis.

The accepted paradigm for both cellular and anti-tumor immunity relies upon tumor cell killing by CD8+ T cells recognizing cognate antigens presented in the context of target cell major histocompatibility complex (MHC) class I (MHC-I) molecules. Likewise, a classically described mechanism of tumor immune escape is tumor MHC-I downregulation. Here, we report that CD8+ T cells maintain the capacity to kill tumor cells that are entirely devoid of MHC-I expression. This capacity proves to be dependent instead on interactions between T cell natural killer group 2D (NKG2D) and tumor NKG2D ligands (NKG2DLs), the latter of which are highly expressed on MHC-loss variants. Necessarily, tumor cell killing in these instances is antigen independent, although prior T cell antigen-specific activation is required and can be furnished by myeloid cells or even neighboring MHC-replete tumor cells. In this manner, adaptive priming can beget innate killing. These mechanisms are active in vivo in mice as well as in vitro in human tumor systems and are obviated by NKG2D knockout or blockade. These studies challenge the long-advanced notion that downregulation of MHC-I is a viable means of tumor immune escape and instead identify the NKG2D-NKG2DL axis as a therapeutic target for enhancing T cell-dependent anti-tumor immunity against MHC-loss variants.

Allergic Asthma Responses Are Dependent on Macrophage Ontogeny.

The ontogenetic composition of tissue-resident macrophages following injury, environmental exposure, or experimental depletion can be altered upon re-establishment of homeostasis. However, the impact of altered resident macrophage ontogenetic milieu on subsequent immune responses is poorly understood. Hence, we assessed the effect of macrophage ontogeny alteration following return to homeostasis on subsequent allergic airway responses to house dust mites (HDM). Using lineage tracing, we confirmed alveolar and interstitial macrophage ontogeny and their replacement by bone marrow-derived macrophages following LPS exposure. This alteration in macrophage ontogenetic milieu reduced allergic airway responses to HDM challenge. In addition, we defined a distinct population of resident-derived interstitial macrophages expressing allergic airway disease genes, located adjacent to terminal bronchi, and reduced by prior LPS exposure. These findings support that the ontogenetic milieu of pulmonary macrophages is a central factor in allergic airway responses and has implications for how prior environmental exposures impact subsequent immune responses and the development of allergy.

Lessons from the pandemic: Responding to emerging zoonotic viral diseases-a Keystone Symposia report.

The COVID-19 pandemic caught the world largely unprepared, including scientific and policy communities. On April 10-13, 2022, researchers across academia, industry, government, and nonprofit organizations met at the Keystone symposium "Lessons from the Pandemic: Responding to Emerging Zoonotic Viral Diseases" to discuss the successes and challenges of the COVID-19 pandemic and what lessons can be applied moving forward. Speakers focused on experiences not only from the COVID-19 pandemic but also from outbreaks of other pathogens, including the Ebola virus, Lassa virus, and Nipah virus. A general consensus was that investments made during the COVID-19 pandemic in infrastructure, collaborations, laboratory and manufacturing capacity, diagnostics, clinical trial networks, and regulatory enhancements-notably, in low-to-middle income countries-must be maintained and strengthened to enable quick, concerted responses to future threats, especially to zoonotic pathogens.

Neuronal CaMKK2 promotes immunosuppression and checkpoint blockade resistance in glioblastoma.

Glioblastoma (GBM) is notorious for its immunosuppressive tumor microenvironment (TME) and is refractory to immune checkpoint blockade (ICB). Here, we identify calmodulin-dependent kinase kinase 2 (CaMKK2) as a driver of ICB resistance. CaMKK2 is highly expressed in pro-tumor cells and is associated with worsened survival in patients with GBM. Host CaMKK2, specifically, reduces survival and promotes ICB resistance. Multimodal profiling of the TME reveals that CaMKK2 is associated with several ICB resistance-associated immune phenotypes. CaMKK2 promotes exhaustion in CD8+ T cells and reduces the expansion of effector CD4+ T cells, additionally limiting their tumor penetrance. CaMKK2 also maintains myeloid cells in a disease-associated microglia-like phenotype. Lastly, neuronal CaMKK2 is required for maintaining the ICB resistance-associated myeloid phenotype, is deleterious to survival, and promotes ICB resistance. Our findings reveal CaMKK2 as a contributor to ICB resistance and identify neurons as a driver of immunotherapeutic resistance in GBM.

Nicotinic stimulation of splenic T cells is protective in endoscopic retrograde cholangiopancreatography-induced acute pancreatitis in mice.

It has previously been shown that current smoking is protective against endoscopic retrograde cholangiopancreatography (ERCP)-induced acute pancreatitis, but the mechanism of this effect was not identified. We tested the hypothesis that nicotine is the active factor in this protection in a mouse model of ERCP. Pretreatment with nicotine dose dependently inhibited acute pancreatitis caused by infusion of ERCP contrast solution into the main pancreatic duct in mice. 3-2,4-Dimethoxybenzylidene anabaseine (GTS-21), a specific partial agonist of the α7 nicotinic cholinergic receptor (α7nAChR), also protected the pancreas against ERCP-induced acute pancreatitis. The effects of GTS-21 were abolished by pretreatment with the nicotinic receptor antagonist mecamylamine. Surgical splenectomy performed 7 days before ERCP-induced pancreatitis blocked the protective effects of GTS-21. Intravenous injection of a crude preparation of total splenocytes prepared from mice pretreated with GTS-21 inhibited ERCP-induced pancreatitis; splenocytes from mice treated with vehicle had no effect. When T cells were removed from the crude GTS-21-treated splenocyte preparation by immunomagnetic separation, the remaining non-T-cell splenocytes did not protect against ERCP-induced acute pancreatitis. We conclude that nicotine protects against ERCP-induced acute pancreatitis and that splenic T cells are required for this effect. Stimulation of α7 nicotinic cholinergic receptors may protect against ERCP-induced acute pancreatitis and may also be a novel approach to therapeutic reversal of ongoing acute pancreatitis.NEW & NOTEWORTHY Epidemiological evidence indicated that acute smoking reduced the risk of endoscopic retrograde cholangiopancreatography (ERCP)-induced pancreatitis, but the mechanism has remained elusive. The current findings indicate the nicotine reduces the severity of ERCP-induced pancreatitis by stimulating a population of splenic T cells that exert a protective effect on the pancreas. These findings raise the possibility that nicotinic agonists might be useful in treating pancreatitis.

Monocytes as a Cellular Vaccine Platform to Induce Antitumor Immunity.

We recently developed a monocyte-based cellular vaccine platform for cancer treatment. In contrast to the traditional utilization of monocytes as precursors to generate dendritic cells (DC) for vaccination purposes, we find that freshly isolated monocytes with no differentiation process can be loaded with tumor antigens (Ag) and trigger robust antitumor cytotoxic T lymphocyte (CTL) responses. In this chapter, we describe methods to prepare, administer, and evaluate murine Ly-6Chi monocyte-based cellular vaccines for their therapeutic efficacy. This includes procedures for isolation, purity determination, Ag loading, administration of bone marrow (BM)-derived monocytes, as well as methods to determine vaccine efficacy through the examination of Ag-specific CD8+ T cell expansion and antitumor responses in murine melanoma models. As a vaccine platform, undifferentiated monocytes can be easily adapted to different tumor models with a multitude of target antigens. The method described here seeks to facilitate preclinical research of monocyte-based vaccination as a strategy for cancer immunotherapy.

Th17 Immunity in the Colon Is Controlled by Two Novel Subsets of Colon-Specific Mononuclear Phagocytes.

Intestinal immunity is coordinated by specialized mononuclear phagocyte populations, constituted by a diversity of cell subsets. Although the cell subsets constituting the mononuclear phagocyte network are thought to be similar in both small and large intestine, these organs have distinct anatomy, microbial composition, and immunological demands. Whether these distinctions demand organ-specific mononuclear phagocyte populations with dedicated organ-specific roles in immunity are unknown. Here we implement a new strategy to subset murine intestinal mononuclear phagocytes and identify two novel subsets which are colon-specific: a macrophage subset and a Th17-inducing dendritic cell (DC) subset. Colon-specific DCs and macrophages co-expressed CD24 and CD14, and surprisingly, both were dependent on the transcription factor IRF4. Novel IRF4-dependent CD14+CD24+ macrophages were markedly distinct from conventional macrophages and failed to express classical markers including CX3CR1, CD64 and CD88, and surprisingly expressed little IL-10, which was otherwise robustly expressed by all other intestinal macrophages. We further found that colon-specific CD14+CD24+ mononuclear phagocytes were essential for Th17 immunity in the colon, and provide definitive evidence that colon and small intestine have distinct antigen presenting cell requirements for Th17 immunity. Our findings reveal unappreciated organ-specific diversity of intestine-resident mononuclear phagocytes and organ-specific requirements for Th17 immunity.

Ultrasensitive point-of-care immunoassay for secreted glycoprotein detects Ebola infection earlier than PCR.

Ebola virus (EBOV) hemorrhagic fever outbreaks have been challenging to deter due to the lack of health care infrastructure in disease-endemic countries and a corresponding inability to diagnose and contain the disease at an early stage. EBOV vaccines and therapies have improved disease outcomes, but the advent of an affordable, easily accessed, mass-produced rapid diagnostic test (RDT) that matches the performance of more resource-intensive polymerase chain reaction (PCR) assays would be invaluable in containing future outbreaks. Here, we developed and demonstrated the performance of a new ultrasensitive point-of-care immunoassay, the EBOV D4 assay, which targets the secreted glycoprotein of EBOV. The EBOV D4 assay is 1000-fold more sensitive than the U.S. Food and Drug Administration-approved RDTs and detected EBOV infection earlier than PCR in a standard nonhuman primate model. The EBOV D4 assay is suitable for low-resource settings and may facilitate earlier detection, containment, and treatment during outbreaks of the disease.

Nonclassical Monocytes Sense Hypoxia, Regulate Pulmonary Vascular Remodeling, and Promote Pulmonary Hypertension.

An increasing body of evidence suggests that bone marrow-derived myeloid cells play a critical role in the pathophysiology of pulmonary hypertension (PH). However, the true requirement for myeloid cells in PH development has not been demonstrated, and a specific disease-promoting myeloid cell population has not been identified. Using bone marrow chimeras, lineage labeling, and proliferation studies, we determined that, in murine hypoxia-induced PH, Ly6Clo nonclassical monocytes are recruited to small pulmonary arteries and differentiate into pulmonary interstitial macrophages. Accumulation of these nonclassical monocyte-derived pulmonary interstitial macrophages around pulmonary vasculature is associated with increased muscularization of small pulmonary arteries and disease severity. To determine if the sensing of hypoxia by nonclassical monocytes contributes to the development of PH, mice lacking expression of hypoxia-inducible factor-1α in the Ly6Clo monocyte lineage were exposed to hypoxia. In these mice, vascular remodeling and PH severity were significantly reduced. Transcriptome analyses suggest that the Ly6Clo monocyte lineage regulates PH through complement, phagocytosis, Ag presentation, and chemokine/cytokine pathways. Consistent with these murine findings, relative to controls, lungs from pulmonary arterial hypertension patients displayed a significant increase in the frequency of nonclassical monocytes. Taken together, these findings show that, in response to hypoxia, nonclassical monocytes in the lung sense hypoxia, infiltrate small pulmonary arteries, and promote vascular remodeling and development of PH. Our results demonstrate that myeloid cells, specifically cells of the nonclassical monocyte lineage, play a direct role in the pathogenesis of PH.

Brain immunology and immunotherapy in brain tumours.

Gliomas, the most common malignant primary brain tumours, remain universally lethal. Yet, seminal discoveries in the past 5 years have clarified the anatomy, genetics and function of the immune system within the central nervous system (CNS) and altered the paradigm for successful immunotherapy. The impact of standard therapies on the response to immunotherapy is now better understood, as well. This new knowledge has implications for a broad range of tumours that develop within the CNS. Nevertheless, the requirements for successful therapy remain effective delivery and target specificity, while the dramatic heterogeneity of malignant gliomas at the genetic and immunological levels remains a profound challenge.

Antigen-loaded monocyte administration induces potent therapeutic antitumor T cell responses.

Efficacy of dendritic cell (DC) cancer vaccines is classically thought to depend on their antigen-presenting cell (APC) activity. Studies show, however, that DC vaccine priming of cytotoxic T lymphocytes (CTLs) requires the activity of endogenous DCs, suggesting that exogenous DCs stimulate antitumor immunity by transferring antigens (Ags) to endogenous DCs. Such Ag transfer functions are most commonly ascribed to monocytes, implying that undifferentiated monocytes would function equally well as a vaccine modality and need not be differentiated to DCs to be effective. Here, we used several murine cancer models to test the antitumor efficacy of undifferentiated monocytes loaded with protein or peptide Ag. Intravenously injected monocytes displayed antitumor activity superior to DC vaccines in several cancer models, including aggressive intracranial glioblastoma. Ag-loaded monocytes induced robust CTL responses via Ag transfer to splenic CD8+ DCs in a manner independent of monocyte APC activity. Ag transfer required cell-cell contact and the formation of connexin 43-containing gap junctions between monocytes and DCs. These findings demonstrate the existence of an efficient gap junction-mediated Ag transfer pathway between monocytes and CD8+ DCs and suggest that administration of tumor Ag-loaded undifferentiated monocytes may serve as a simple and efficacious immunotherapy for the treatment of human cancers.

Twist1 in Infiltrating Macrophages Attenuates Kidney Fibrosis via Matrix Metallopeptidase 13-Mediated Matrix Degradation.

BACKGROUND: Following an acute insult, macrophages regulate renal fibrogenesis through the release of various factors that either encourage the synthesis of extracellular matrix synthesis or the degradation of matrix via endocytosis, proteolysis, or both. However, the roles of infiltrating versus resident myeloid cells in these opposing processes require elucidation. The transcription factor Twist1 controls diverse essential cellular functions through induction of several downstream targets, including matrix metalloproteinases (MMPs). In macrophages, Twist1 can influence patterns of cytokine generation, but the role of macrophage Twist1 in renal fibrogenesis remains undefined. METHODS: To study Twist1 functions in different macrophage subsets during kidney scar formation, we used two conditional mutant mouse models in which Twist1 was selectively ablated either in infiltrating, inflammatory macrophages or in resident tissue macrophages. We assessed fibrosis-related parameters, matrix metallopeptidase 13 (MMP13, or collagen 3, which catalyzes collagen degradation), inflammatory cytokines, and other factors in these Twist1-deficient mice compared with wild-type controls after subjecting the animals to unilateral ureteral obstruction. We also treated wild-type and Twist1-deficient mice with an MMP13 inhibitor after unilateral ureteral obstruction. RESULTS: Twist1 in infiltrating inflammatory macrophages but not in resident macrophages limited kidney fibrosis after ureteral obstruction by driving extracellular matrix degradation. Moreover, deletion of Twist1 in infiltrating macrophages attenuated the expression of MMP13 in CD11b+Ly6Clo myeloid cells. Inhibition of MMP13 abrogated the protection from renal fibrosis afforded by macrophage Twist1. CONCLUSIONS: Twist1 in infiltrating myeloid cells mitigates interstitial matrix accumulation in the injured kidney by promoting MMP13 production, which drives extracellular matrix degradation. These data highlight the complex cell-specific actions of Twist1 in the pathogenesis of kidney fibrosis.

Improved efficacy against malignant brain tumors with EGFRwt/EGFRvIII targeting immunotoxin and checkpoint inhibitor combinations.

BACKGROUND: D2C7-IT is a novel immunotoxin (IT) targeting wild-type epidermal growth factor receptor (EGFRwt) and mutant EGFR variant III (EGFRvIII) proteins in glioblastoma. In addition to inherent tumoricidal activity, immunotoxins induce secondary immune responses through the activation of T cells. However, glioblastoma-induced immune suppression is a major obstacle to an effective and durable immunotoxin-mediated antitumor response. We hypothesized that D2C7-IT-induced immune response could be effectively augmented in combination with αCTLA-4/αPD-1/αPD-L1 therapies in murine models of glioma. METHODS: To study this, we overexpressed the D2C7-IT antigen, murine EGFRvIII (dmEGFRvIII), in established glioma lines, CT-2A and SMA560. The reactivity and therapeutic efficacy of D2C7-IT against CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII cells was determined by flow cytometry and in vitro cytotoxicity assays, respectively. Antitumor efficacy of D2C7-IT was examined in immunocompetent, intracranial murine glioma models and the role of T cells was assessed by CD4+ and CD8+ T cell depletion. In vivo efficacy of D2C7-IT/αCTLA-4/αPD-1 monotherapy or D2C7-IT+αCTLA-4/αPD-1 combination therapy was evaluated in subcutaneous unilateral and bilateral CT-2A-dmEGFRvIII glioma-bearing immunocompetent mice. Further, antitumor efficacy of D2C7-IT+αCTLA-4/αPD-1/αPD-L1/αTim-3/αLag-3/αCD73 combination therapy was evaluated in intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII glioma-bearing mice. Pairwise differences in survival curves were assessed using the generalized Wilcoxon test. RESULTS: D2C7-IT effectively killed CT-2A-dmEGFRvIII (IC50 = 0.47 ng/mL) and SMA560-dmEGFRvIII (IC50 = 1.05 ng/mL) cells in vitro. Treatment of intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII tumors with D2C7-IT prolonged survival (P = 0.0188 and P = 0.0057, respectively), which was significantly reduced by the depletion of CD4+ and CD8+ T cells. To augment antitumor immune responses, we combined D2C7-IT with αCTLA-4/αPD-1 in an in vivo subcutaneous CT-2A-dmEGFRvIII model. Tumor-bearing mice exhibited complete tumor regressions (4/10 in D2C7-IT+αCTLA-4 and 5/10 in D2C7-IT+αPD-1 treatment groups), and combination therapy-induced systemic antitumor response was effective against both dmEGFRvIII-positive and dmEGFRvIII-negative CT-2A tumors. In a subcutaneous bilateral CT-2A-dmEGFRvIII model, D2C7-IT+αCTLA-4/αPD-1 combination therapies showed dramatic regression of the treated tumors and measurable regression of untreated tumors. Notably, in CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII intracranial glioma models, D2C7-IT+αPD-1/αPD-L1 combinations improved survival, and in selected cases generated cures and protection against tumor re-challenge. CONCLUSIONS: These data support the development of D2C7-IT and immune checkpoint blockade combinations for patients with malignant glioma.

Author Correction: Sequestration of T cells in bone marrow in the setting of glioblastoma and other intracranial tumors.

In the version of this article originally published, the figure callout in this sentence was incorrect: "Furthermore, in S1P1-KI mice themselves, whereas PD-1 blockade was ineffectual as monotherapy, the effects of 4-1BB agonism and checkpoint blockade proved additive, with the combination prolonging median survival and producing a 50% long-term survival rate (Fig. 6f)." The callout should have been to Supplementary Fig. 6b. The error has been corrected in the PDF and HTML versions of the article.

Biased agonists of the chemokine receptor CXCR3 differentially control chemotaxis and inflammation.

The chemokine receptor CXCR3 plays a central role in inflammation by mediating effector/memory T cell migration in various diseases; however, drugs targeting CXCR3 and other chemokine receptors are largely ineffective in treating inflammation. Chemokines, the endogenous peptide ligands of chemokine receptors, can exhibit so-called biased agonism by selectively activating either G protein- or ß-arrestin-mediated signaling after receptor binding. Biased agonists might be used as more targeted therapeutics to differentially regulate physiological responses, such as immune cell migration. To test whether CXCR3-mediated physiological responses could be segregated by G protein- and ß-arrestin-mediated signaling, we identified and characterized small-molecule biased agonists of the receptor. In a mouse model of T cell-mediated allergic contact hypersensitivity (CHS), topical application of a ß-arrestin-biased, but not a G protein-biased, agonist potentiated inflammation. T cell recruitment was increased by the ß-arrestin-biased agonist, and biopsies of patients with allergic CHS demonstrated coexpression of CXCR3 and ß-arrestin in T cells. In mouse and human T cells, the ß-arrestin-biased agonist was the most efficient at stimulating chemotaxis. Analysis of phosphorylated proteins in human lymphocytes showed that ß-arrestin-biased signaling activated the kinase Akt, which promoted T cell migration. This study demonstrates that biased agonists of CXCR3 produce distinct physiological effects, suggesting discrete roles for different endogenous CXCR3 ligands and providing evidence that biased signaling can affect the clinical utility of drugs targeting CXCR3 and other chemokine receptors.

Sequestration of T cells in bone marrow in the setting of glioblastoma and other intracranial tumors.

T cell dysfunction contributes to tumor immune escape in patients with cancer and is particularly severe amidst glioblastoma (GBM). Among other defects, T cell lymphopenia is characteristic, yet often attributed to treatment. We reveal that even treatment-naïve subjects and mice with GBM can harbor AIDS-level CD4 counts, as well as contracted, T cell-deficient lymphoid organs. Missing naïve T cells are instead found sequestered in large numbers in the bone marrow. This phenomenon characterizes not only GBM but a variety of other cancers, although only when tumors are introduced into the intracranial compartment. T cell sequestration is accompanied by tumor-imposed loss of S1P1 from the T cell surface and is reversible upon precluding S1P1 internalization. In murine models of GBM, hindering S1P1 internalization and reversing sequestration licenses T cell-activating therapies that were previously ineffective. Sequestration of T cells in bone marrow is therefore a tumor-adaptive mode of T cell dysfunction, whose reversal may constitute a promising immunotherapeutic adjunct.

Interleukin 1 receptor (IL-1R1) activation exacerbates toxin-induced acute kidney injury.

Acute kidney injury (AKI) is a leading cause of morbidity and mortality. Drug-induced/toxic AKI can be caused by a number of therapeutic agents. Cisplatin is an effective chemotherapeutic agent whose administration is limited by significant nephrotoxicity. Therapies to prevent cisplatin-induced AKI are lacking. Although tumor necrosis factor-α (TNF) plays a key role in the pathogenesis of cisplatin nephrotoxicity, the innate immune signaling pathways that trigger TNF generation in this context require elucidation. In this regard, sterile injury triggers the release and activation of both isoforms of interleukin(IL)-1, IL-1α and IL-1ß. In turn, stimulation of the interleukin-1 receptor (IL-1R1) by these ligands engages a proinflammatory signaling cascade that induces TNF induction. We therefore hypothesized that IL-1R1 activation exacerbates cisplatin-induced AKI by inducing TNF production, thereby augmenting inflammatory signals between kidney parenchymal cells and infiltrating myeloid cells. IL-1R1+/+ (WT) and IL-1R1-/- (KO) mice were subjected to cisplatin-induced AKI. Compared with WT mice, IL-1R1 KO mice had attenuated AKI as measured by serum creatinine and BUN, renal NGAL mRNA levels, and blinded histological analysis of kidney pathology. In the cisplatin-injured kidney, IL-1R1 KO mice had diminished levels of whole kidney TNF, and fewer Ly6G-expressing neutrophils. In addition, an unbiased machine learning analysis of intrarenal immune cells revealed a diminished number of CD11bint/CD11cint myeloid cells in IL-1R1 KO injured kidneys compared with IL-1R1 WT kidneys. Following cisplatin, IL-1R1 KO kidneys, compared with WTs, had fewer TNF-producing: macrophages, CD11bint/CD11cint cells, and neutrophils, consistent with an effect of IL-1R1 to polarize intrarenal myeloid cells toward a proinflammatory phenotype. Interruption of IL-1-dependent signaling pathways warrants further evaluation to decrease nephrotoxicity during cisplatin therapy.