Notch4 signaling limits regulatory T-cell-mediated tissue repair and promotes severe lung inflammation in viral infections.

A cardinal feature of COVID-19 is lung inflammation and respiratory failure. In a prospective multi-country cohort of COVID-19 patients, we found that increased Notch4 expression on circulating regulatory T (Treg) cells was associated with disease severity, predicted mortality, and declined upon recovery. Deletion of Notch4 in Treg cells or therapy with anti-Notch4 antibodies in conventional and humanized mice normalized the dysregulated innate immunity and rescued disease morbidity and mortality induced by a synthetic analog of viral RNA or by influenza H1N1 virus. Mechanistically, Notch4 suppressed the induction by interleukin-18 of amphiregulin, a cytokine necessary for tissue repair. Protection by Notch4 inhibition was recapitulated by therapy with Amphiregulin and, reciprocally, abrogated by its antagonism. Amphiregulin declined in COVID-19 subjects as a function of disease severity and Notch4 expression. Thus, Notch4 expression on Treg cells dynamically restrains amphiregulin-dependent tissue repair to promote severe lung inflammation, with therapeutic implications for COVID-19 and related infections.

Multiscale networks in multiple sclerosis.

Complex diseases such as Multiple Sclerosis (MS) cover a wide range of biological scales, from genes and proteins to cells and tissues, up to the full organism. In fact, any phenotype for an organism is dictated by the interplay among these scales. We conducted a multilayer network analysis and deep phenotyping with multi-omics data (genomics, phosphoproteomics and cytomics), brain and retinal imaging, and clinical data, obtained from a multicenter prospective cohort of 328 patients and 90 healthy controls. Multilayer networks were constructed using mutual information for topological analysis, and Boolean simulations were constructed using Pearson correlation to identified paths within and among all layers. The path more commonly found from the Boolean simulations connects protein MK03, with total T cells, the thickness of the retinal nerve fiber layer (RNFL), and the walking speed. This path contains nodes involved in protein phosphorylation, glial cell differentiation, and regulation of stress-activated MAPK cascade, among others. Specific paths identified were subsequently analyzed by flow cytometry at the single-cell level. Combinations of several proteins (GSK3AB, HSBP1 or RS6) and immune cells (Th17, Th1 non-classic, CD8, CD8 Treg, CD56 neg, and B memory) were part of the paths explaining the clinical phenotype. The advantage of the path identified from the Boolean simulations is that it connects information about these known biological pathways with the layers at higher scales (retina damage and disability). Overall, the identified paths provide a means to connect the molecular aspects of MS with the overall phenotype.

Evaluation of Frequency of CMV Replication and Disease Complications Reveals New Cellular Defects and a Time Dependent Pattern in CVID Patients.

PURPOSE: Common Variable Immunodeficiency (CVID) is characterized by hypogammaglobulinemia and failure of specific antibody production due to B-cell defects. However, studies have documented various T-cell abnormalities, potentially linked to viral complications. The frequency of Cytomegalovirus (CMV) replication in CVID cohorts is poorly studied. To address this gap in knowledge, we set up an observational study with the objectives of identifying CVID patients with active viraemia (CMV, Epstein-Barr virus (EBV)), evaluating potential correlations with immunophenotypic characteristics, clinical outcome, and the dynamic progression of clinical phenotypes over time. METHODS: 31 CVID patients were retrospectively analysed according to viraemia, clinical and immunologic characteristics. 21 patients with non CVID humoral immunodeficiency were also evaluated as control. RESULTS: Active viral replication of CMV and/or EBV was observed in 25% of all patients. CMV replication was detected only in CVID patients (16%). CVID patients with active viral replication showed reduced HLA-DR+ NK counts when compared with CMV-DNA negative CVID patients. Viraemic patients had lower counts of LIN-DNAMbright and LIN-CD16+ inflammatory lymphoid precursors which correlated with NK-cell subsets. Analysis of the dynamic progression of CVID clinical phenotypes over time, showed that the initial infectious phenotype progressed to complicated phenotypes with time. All CMV viraemic patients had complicated disease. CONCLUSION: Taken together, an impaired production of inflammatory precursors and NK activation is present in CVID patients with active viraemia. Since "Complicated" CVID occurs as a function of disease duration, there is need for an accurate evaluation of this aspect to improve classification and clinical management of CVID patients.

BODIPY-Based Analogue of the TREM2-Binding Molecular Adjuvant Sulfavant A, a Chemical Tool for Imaging and Tracking Biological Systems.

Recently, we described synthetic sulfolipids named Sulfavants as a novel class of molecular adjuvants based on the sulfoquinovosyl-diacylglycerol skeleton. The members of this family, Sulfavant A (1), Sulfavant R (2), and Sulfavant S (3), showed important effects on triggering receptor expressed on myeloid cells 2 (TREM2)-induced differentiation and maturation of human dendritic cells (hDC), through a novel cell mechanism underlying the regulation of the immune response. As these molecules are involved in biological TREM2-mediated processes crucial for cell survival, here, we report the synthesis and application of a fluorescent analogue of Sulfavant A bearing the 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene moiety (Me4-BODIPY). The fluorescent derivative, named PB-SULF A (4), preserving the biological activity of Sulfavants, opens the way to chemical biology and cell biology experiments to better understand the interactions with cellular and in vivo organ targets and to improve our comprehension of complex molecular mechanisms underlying the not fully understood ligand-induced TREM2 activity.

Extensive activation, tissue trafficking, turnover and functional impairment of NK cells in COVID-19 patients at disease onset associates with subsequent disease severity.

The SARS-CoV-2 infection causes severe respiratory involvement (COVID-19) in 5-20% of patients through initial immune derangement, followed by intense cytokine production and vascular leakage. Evidence of immune involvement point to the participation of T, B, and NK cells in the lack of control of virus replication leading to COVID-19. NK cells contribute to early phases of virus control and to the regulation of adaptive responses. The precise mechanism of NK cell dysregulation is poorly understood, with little information on tissue margination or turnover. We investigated these aspects by multiparameter flow cytometry in a cohort of 28 patients hospitalized with early COVID-19. Relevant decreases in CD56brightCD16+/- NK subsets were detected, with a shift of circulating NK cells toward more mature CD56dimCD16+KIR+NKG2A+ and "memory" KIR+CD57+CD85j+ cells with increased inhibitory NKG2A and KIR molecules. Impaired cytotoxicity and IFN-γ production were associated with conserved expression of natural cytotoxicity receptors and perforin. Moreover, intense NK cell activation with increased HLA-DR and CD69 expression was associated with the circulation of CD69+CD103+ CXCR6+ tissue-resident NK cells and of CD34+DNAM-1brightCXCR4+ inflammatory precursors to mature functional NK cells. Severe disease trajectories were directly associated with the proportion of CD34+DNAM-1brightCXCR4+ precursors and inversely associated with the proportion of NKG2D+ and of CD103+ NK cells. Intense NK cell activation and trafficking to and from tissues occurs early in COVID-19, and is associated with subsequent disease progression, providing an insight into the mechanism of clinical deterioration. Strategies to positively manipulate tissue-resident NK cell responses may provide advantages to future therapeutic and vaccine approaches.

Sulfavant A as the first synthetic TREM2 ligand discloses a homeostatic response of dendritic cells after receptor engagement.

OBJECTIVE: The immune response arises from a fine balance of mechanisms that provide for surveillance, tolerance, and elimination of dangers. Sulfavant A (SULF A) is a sulfolipid with a promising adjuvant activity. Here we studied the mechanism of action of SULF A and addressed the identification of its molecular target in human dendritic cells (hDCs). METHODS: Adjuvant effect and immunological response to SULF A were assessed on DCs derived from human donors. In addition to testing various reporter cells, target identification and downstream signalling was supported by a reverse pharmacology approach based on antibody blocking and gene silencing, crosstalk with TLR pathways, use of human allogeneic mixed lymphocyte reaction. RESULTS: SULF A binds to the Triggering Receptor Expressed on Myeloid cells-2 (TREM2) and initiates an unconventional maturation of hDCs leading to enhanced migration activity and up-regulation of MHC and co-stimulatory molecules without release of conventional cytokines. This response involves the SYK-NFAT axis and is compromised by blockade or gene silencing of TREM2. Activation by SULF A preserved the DC functions to excite the allogeneic T cell response, and increased interleukin-10 release after lipopolysaccharide stimulation. CONCLUSION: SULF A is the first synthetic small molecule that binds to TREM2. The receptor engagement drives differentiation of an unprecedented DC phenotype (homeDCs) that contributes to immune homeostasis without compromising lymphocyte activation and immunogenic response. This mechanism fully supports the adjuvant and immunoregulatory activity of SULF A. We also propose that the biological properties of SULF A can be of interest in various physiopathological mechanisms and therapies involving TREM2.

Spontaneous NLRP3 inflammasome-driven IL-1-ß secretion is induced in severe COVID-19 patients and responds to anakinra treatment.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may result in a severe pneumonia associated with elevation of blood inflammatory parameters, reminiscent of cytokine storm syndrome. Steroidal anti-inflammatory therapies have shown efficacy in reducing mortality in critically ill patients; however, the mechanisms by which SARS-CoV-2 triggers such an extensive inflammation remain unexplained. OBJECTIVES: To dissect the mechanisms underlying SARS-CoV-2-associated inflammation in patients with severe coronavirus disease 2019 (COVID-19), we studied the role of IL-1ß, a pivotal cytokine driving inflammatory phenotypes, whose maturation and secretion are regulated by inflammasomes. METHODS: We analyzed nod-like receptor protein 3 pathway activation by means of confocal microscopy, plasma cytokine measurement, cytokine secretion following in vitro stimulation of blood circulating monocytes, and whole-blood RNA sequencing. The role of open reading frame 3a SARS-CoV-2 protein was assessed by confocal microscopy analysis following nucleofection of a monocytic cell line. RESULTS: We found that circulating monocytes from patients with COVID-19 display ASC (adaptor molecule apoptotic speck like protein-containing a CARD) specks that colocalize with nod-like receptor protein 3 inflammasome and spontaneously secrete IL-1ß in vitro. This spontaneous activation reverts following patient's treatment with the IL-1 receptor antagonist anakinra. Transfection of a monocytic cell line with cDNA coding for the ORF3a SARS-CoV-2 protein resulted in ASC speck formation. CONCLUSIONS: These results provide further evidence that IL-1ß targeting could represent an effective strategy in this disease and suggest a mechanistic explanation for the strong inflammatory manifestations associated with COVID-19.

Effects of colchicine on tissue factor in oxLDL-activated T-lymphocytes.

Several studies have shown that T-cells might be involved in pathophysiology of acute coronary syndromes (ACS). Tissue factor (TF) plays a key role in ACS. Many evidences have indicated that some statins reduce TF expression in several cell types. However, literature about rosuvastatin and TF and about statins effects on T-cells is still scanty. Colchicine is an anti-inflammatory drug recently proven to have beneficial effects in ACS via unknown mechanisms. This study investigates the effects of colchicine and rosuvastatin on TF expression in oxLDL-activated T-cells. T-cells, isolated from buffy coats of healthy volunteers, were stimulated with oxLDL (50 µg/dL). T-cells were pre-incubated with colchicine (10 µM) or rosuvastatin (5 µM) for 1 h and then stimulated with oxLDL (50 µg/mL). TF gene (RT-PCR), protein (western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. NF-κB/IκB axis was examined by western blot analysis and translocation assay. Colchicine and rosuvastatin significantly reduced TF gene, and protein expression and procoagulant activity in oxLDL stimulated T-cells. This effect was associated with a significant reduction in TF surface expression as well as its procoagulant activity. These phenomena appear modulated by drug effects on the transcription factor NF-kB. Rosuvastatin and colchicine prevent TF expression in oxLDL-stimulated T-cells by modulating the NF-κB/IκB axis. Thus, we speculate that this might be another mechanism by which these drugs exert benefic cardiovascular effects.

Human T cells interacting with HNSCC-derived mesenchymal stromal cells acquire tissue-resident memory like properties.

Tissue-resident memory (Trm) cells are specialized components of both CD4+ and CD8+ T cell subsets that persist in peripheral nonlymphoid tissues following infections and provide fast response in case of a secondary invasion by the same pathogen. Trm cells express the surface markers CD69, CD103, and the immune checkpoint molecule PD-1. Trm cells develop not only in the context of infections but also in tumors, where they can provide a line of defense as suggested by the positive correlation between the frequency of tumor-infiltrating Trm cells and patients' survival. Trm cells persistence in peripheral tissues depends on their adaptation to the local microenvironment and the presence of survival factors, mainly IL-7, IL-15, and Notch ligands. However, the cell sources of these factors are largely unknown, especially in the context of tumors. Here, we show that head-neck squamous cell carcinoma (HNSCC) is enriched in CD4+ and CD8+ T cells with a Trm phenotype. Moreover, we show that mesenchymal stromal cells that accumulate in HNSCC are a source of survival factors and allow proper expression of Trm-typical markers in a VCAM1-dependent manner.

Characterization of T lymphocytes in severe COVID-19 patients.

In this observational study, 13 patients with severe COVID-19 and 10 healthy controls were enrolled. The data concerning the analysis of circulating T cells show that, in severe COVID-19 patients, the expansion of these cell compartments is prone to induce antibody response, inflammation (CCR4+ and CCR6+ TFH) and regulation (CD8+ Treg). This pathogenic mechanism could lead us to envision a possible new form of biological target therapy.

Rarity of human T helper 17 cells is due to retinoic acid orphan receptor-dependent mechanisms that limit their expansion.

The reason why CD4(+) T helper 17 (Th17) cells, despite their well-known pathogenic role in chronic inflammatory disorders, are very rare in the inflammatory sites remains unclear. We demonstrate that human Th17 cells exhibit low ability to proliferate and to produce the T cell growth factor interleukin-2 (IL-2), in response to combined CD3 and CD28 stimulation. This was due to the upregulated expression of IL-4-induced gene 1 (IL4I1) mRNA, a secreted L-phenylalanine oxidase, which associated with a decrease in CD3ζ chain expression and consequent abnormalities in the molecular pathway that allows IL-2 production and cell proliferation. High IL4I1 mRNA expression was detectable in Th17 cell precursors and was strictly dependent on Th17 cell master gene, the retinoid acid related orphan receptor (RORC). Th17 cells also exhibited RORC-dependent CD28 hyperexpression and the ability to produce IL-17A after CD28 stimulation without CD3 triggering. Our findings suggest that the rarity of human Th17 cells in inflamed tissues results from RORC-dependent mechanisms limiting their expansion.

Eomes controls the development of Th17-derived (non-classic) Th1 cells during chronic inflammation.

It is well accepted that Th17 cells are a highly plastic cell subset that can be easily directed toward the Th1 phenotype in vitro and also in vivo during inflammation. However, there is an ongoing debate regarding the reverse plasticity (conversion from Th1 to Th17). We show here that ectopic ROR-γt expression can restore or initiate IL-17 expression by non-classic or classic Th1 cells, respectively, while common pro-Th17 cytokine cocktails are ineffective. This stability of the Th1 phenotype is at least partially due to the presence of a molecular machinery governed by the transcription factor Eomes, which promotes IFN-γ secretion while inhibiting the expression of ROR-γt and IL-17. By using a mouse model of T cell-dependent colitis we demonstrate that Eomes controls non-classic Th1 cell development also in vivo and promotes their pathogenic potential. Eomes expression associates to a highly inflammatory phenotype also in patients with juvenile idiopathic arthritis. Indeed, it favors the acquisition of a cytotoxic signature, and promotes the development of IFN-γ+ GM-CSF+ cells that have been described to be pathogenic in chronic inflammatory disorders.

Preparation, Supramolecular Aggregation and Immunological Activity of the Bona Fide Vaccine Adjuvant Sulfavant S.

In aqueous conditions, amphiphilic bioactive molecules are able to form self-assembled colloidal structures modifying their biological activity. This behavior is generally neglected in preclinical studies, despite its impact on pharmacological development. In this regard, a significative example is represented by a new class of amphiphilic marine-inspired vaccine adjuvants, collectively named Sulfavants, based on the ß-sulfoquinovosyl-diacylglyceride skeleton. The family includes the lead product Sulfavant A (1) and two epimers, Sulfavant R (2) and Sulfavant S (3), differing only for the stereochemistry at C-2 of glycerol. The three compounds showed a significant difference in immunological potency, presumably correlated with change of the aggregates in water. Here, a new synthesis of diastereopure 3 was achieved, and the study of the immunomodulatory behavior of mixtures of 2/3 proved that the bizarre in vitro response to 1-3 effectively depends on the supramolecular aggregation states, likely affecting the bioavailability of agonists that can effectively interact with the cellular targets. The evidence obtained with the mixture of pure Sulfavant R (2) and Sulfavant S (3) proves, for the first time, that supramolecular organization of a mixture of active epimers in aqueous solution can bias evaluation of their biological and pharmacological potential.

A New Bioassay Platform Design for the Discovery of Small Molecules with Anticancer Immunotherapeutic Activity.

Immunotherapy takes advantage of the immune system to prevent, control, and eliminate neoplastic cells. The research in the field has already led to major breakthroughs to treat cancer. In this work, we describe a platform that integrates in vitro bioassays to test the immune response and direct antitumor effects for the preclinical discovery of anticancer candidates. The platform relies on the use of dendritic cells that are professional antigen-presenting cells (APC) able to activate T cells and trigger a primary adaptive immune response. The experimental procedure is based on two phenotypic assays for the selection of chemical leads by both a panel of nine tumor cell lines and growth factor-dependent immature mouse dendritic cells (D1). The positive hits are then validated by a secondary test on human monocyte-derived dendritic cells (MoDCs). The aim of this approach is the selection of potential immunotherapeutic small molecules from natural extracts or chemical libraries.

Prognostic Factors and Biomarkers of Responses to Immune Checkpoint Inhibitors in Lung Cancer.

Manipulation of the immune response is a game changer in lung cancer treatment, revolutionizing management. PD1 and CTLA4 are dynamically expressed on different T cell subsets that can either disrupt or sustain tumor growth. Monoclonal antibodies (MoAbs) against PD1/PDL1 and CTLA4 have shown that inhibitory signals can be impaired, blocking T cell activation and function. MoAbs, used as both single-agents or in combination with standard therapy for the treatment of advanced non-small cell lung cancer (NSCLC), have exhibited advantages in terms of overall survival and response rate; nivolumab, pembrolizumab, atezolizumab and more recently, durvalumab, have already been approved for lung cancer treatment and more compounds are in the pipeline. A better understanding of signaling elicited by these antibodies on T cell subsets, as well as identification of biological determinants of sensitivity, resistance and correlates of efficacy, will help to define the mechanisms of antitumor responses. In addition, the relevance of T regulatory cells (Treg) involved in immune responses in cancer is attracting increasing interest. A major challenge for future research is to understand why a durable response to immune checkpoint inhibitors (ICIs) occurs only in subsets of patients and the mechanisms of resistance after an initial response. This review will explore current understanding and future direction of research on ICI treatment in lung cancer and the impact of tumor immune microenvironment n influencing clinical responses.

Immune Checkpoint Blockade for Advanced NSCLC: A New Landscape for Elderly Patients.

The therapeutic scenario for elderly patients with advanced NSCLC has been limited to radiotherapy and chemotherapy. Recently, a novel therapeutic approach based on targeting the immune-checkpoints has showed noteworthy results in advanced NSCLC. PD1/PD-L1 pathway is co-opted by tumor cells through the expression of PD-L1 on the tumor cell surface and on cells within the microenvironment, leading to suppression of anti-tumor cytolytic T-cell activity by the tumor. The success of immune-checkpoints inhibitors in clinical trials led to rapid approval by the FDA and EMA. Currently, data regarding efficacy and safety of ICIs in older subjects is limited by the poor number of elderly recruited in clinical trials. Careful assessment and management of comorbidities is essential to achieve better outcomes and limit the immune related adverse events in elderly NSCLC patients.

A simple twist of phosphate: Immunological synapse formation and T cell receptor signaling outcome in regulatory T cells.

Signaling through the T cell receptor (TCR) regulates T cell homeostasis and effector functions. However, a full accounting of the TCR-coupled signaling networks and how their interplay determines specific functional outcomes remains elusive. Of particular interest are efforts over the last years to elucidate distinctive features of TCR signaling in regulatory T cells (Treg) that may account for some of their unique functional attributes as compared to conventional T (Tconv) cells. In this issue of the European Journal of Immunology, van Ham et al. [Eur. J. Immunol. 2017. 47: 2043-2058] employed differential phosphoproteomics to identify a set of 11 proteins mainly linked to cytoskeletal organization and molecular transport that discriminate between TCR signaling in the respective cell subset. They further linked these differences to cell subset-specific alterations in the spatio-temporal organization of signaling pathways at immune synapse (IS) in Treg versus T conv. These data support the idea that these proteins may act as a molecular "twist" element driving Treg cell-specific responses by affecting cytoskeletal dynamics and IS formation. Taken together, these findings may facilitate the development of novel immunomodulatory agents that exploit differences in TCR signaling between Treg and Tconv cells.

Musculin inhibits human T-helper 17 cell response to interleukin 2 by controlling STAT5B activity.

We recently demonstrated that human T-helper (Th) 17 cells, unlike Th1 cells, do not proliferate in response to T-cell receptor stimulation, mainly because of their reduced capacity to produce and respond to IL-2. In this study, we show that their lower responsiveness to IL-2 is due to the selective expression of Musculin (MSC), a member of the basic helix-loop-helix transcription factors. We show that MSC expression in human Th17 cells is retinoic acid orphan receptor (ROR)γt-dependent, and allows the upregulation of PPP2R2B, a regulatory member of the protein phosphatase 2A (PP2A) enzyme. High PPP2R2B levels in human Th17 cells were responsible for the reduced STAT5B Ser-193 phosphorylation upon IL-2 signalling and, therefore, impaired STAT5B DNA binding and transcriptional activity on IL-2 target genes. PP2A, observed in Th17 cells, controls also STAT3, dephosphorylating Ser727, thus increasing its activity that plays a crucial role in Th17 development and/or maintenance. Thus, our findings identify an additional mechanism responsible for the limited expansion of human Th17 cells, and could provide a further explanation for the rarity of these cells in inflamed tissues.

Human circulating group 2 innate lymphoid cells can express CD154 and promote IgE production.

BACKGROUND: Protection against helminths consists of adaptive responses by TH2 cells and innate responses by group 2 innate lymphoid cells (ILC2s), with these latter being well characterized in mice but less so in human subjects. OBJECTIVE: We sought to characterize human circulating ILC2s and compare their functional profile with that of autologous TH2 cells. METHODS: Circulating ILC2s and TH2 cells were isolated by means of fluorescence-activated cell sorting and magnetic cell sorting and expanded in vitro. ILC2s were then stimulated with phorbol 12-myristate 13-acetate plus ionomycin, IL-25 plus IL-33 (IL-25/IL-33), or a mixture of Toll-like receptor ligands to evaluate their ability to produce cytokines, express CD154, and induce IgE production by autologous B cells. Cytokines and transcription factor gene methylation were assessed. RESULTS: ILC2s expressed GATA-3, retinoic acid orphan receptor (RORC) 2, and RORα; were able to produce IL-5, IL-13, and IL-4; and, accordingly, were characterized by demethylation of IL4, IL13, IL5, GATA3, and RORC2, whereas the IFNG, IFNG promoter, and TBX21 regions of interest were methylated. ILC2s expressed TLR1, TLR4, and TLR6, and TLR stimulation induced IL-5 and IL-13 production. Moreover, ILC2s expressed CD154 in response to phorbol 12-myristate 13-acetate plus ionomycin, IL-25/IL-33, or a mixture of TLR ligands. Stimulated ILC2s also induced IgM, IgG, IgA, and IgE production by B cells. Finally, circulating ILC2s from atopic patients were not different in numbers and frequency but expressed higher IL-4 levels than those from nonatopic subjects. CONCLUSION: This study provides the first evidence that human ILC2s can express CD154 and stimulate the production of IgE by B lymphocytes through IL-25/IL-33 stimulation or TLR triggering.