CTLA-4 Pathway Is Instrumental in Giant Cell Arteritis.

BACKGROUND: Giant cell arteritis (GCA) causes severe inflammation of the aorta and its branches and is characterized by intense effector T-cell infiltration. The roles that immune checkpoints play in the pathogenesis of GCA are still unclear. Our aim was to study the immune checkpoint interplay in GCA. METHODS: First, we used VigiBase, the World Health Organization international pharmacovigilance database, to evaluate the relationship between GCA occurrence and immune checkpoint inhibitors treatments. We then further dissected the role of immune checkpoint inhibitors in the pathogenesis of GCA, using immunohistochemistry, immunofluorescence, transcriptomics, and flow cytometry on peripheral blood mononuclear cells and aortic tissues of GCA patients and appropriated controls. RESULTS: Using VigiBase, we identified GCA as a significant immune-related adverse event associated with anti-CTLA-4 (cytotoxic T-lymphocyte-associated protein-4) but not anti-PD-1 (anti-programmed death-1) nor anti-PD-L1 (anti-programmed death-ligand 1) treatment. We further dissected a critical role for the CTLA-4 pathway in GCA by identification of the dysregulation of CTLA-4-derived gene pathways and proteins in CD4+ (cluster of differentiation 4) T cells (and specifically regulatory T cells) present in blood and aorta of GCA patients versus controls. While regulatory T cells were less abundant and activated/suppressive in blood and aorta of GCA versus controls, they still specifically upregulated CTLA-4. Activated and proliferating CTLA-4+ Ki-67+ regulatory T cells from GCA were more sensitive to anti-CTLA-4 (ipilimumab)-mediated in vitro depletion versus controls. CONCLUSIONS: We highlighted the instrumental role of CTLA-4 immune checkpoint in GCA, which provides a strong rationale for targeting this pathway.

Deep immunophenotyping reveals that autoimmune and autoinflammatory disorders are spread along two immunological axes capturing disease inflammation levels and types.

OBJECTIVES: Based on genetic associations, McGonagle and McDermott suggested a classification of autoimmune and autoinflammatory diseases as a continuum ranging from purely autoimmune to purely autoinflammatory diseases and comprising diseases with both components. We used deep immunophenotyping to identify immune cell populations and molecular targets characterising this continuum. METHODS: We collected blood from 443 patients with one of 15 autoimmune or autoinflammatory diseases and 71 healthy volunteers. Deep phenotyping was performed using 13 flow cytometry panels characterising over 600 innate and adaptive cell populations. Unsupervised and supervised analyses were conducted to identify disease clusters with their common and specific cell parameters. RESULTS: Unsupervised clustering categorised these diseases into five clusters. Principal component analysis deconvoluted this clustering into two immunological axes. The first axis was driven by the ratio of LAG3+ to ICOS+ in regulatory T lymphocytes (Tregs), and segregated diseases based on their inflammation levels. The second axis was driven by activated Tregs and type 3 innate lymphoid cells (ILC3s), and segregated diseases based on their types of affected tissues. We identified a signature of 23 cell populations that accurately characterised the five disease clusters. CONCLUSIONS: We have refined the monodimensional continuum of autoimmune and autoinflammatory diseases as a continuum characterised by both disease inflammation levels and targeted tissues. Such classification should be helpful for defining therapies. Our results call for further investigations into the role of the LAG3+/ICOS+ balance in Tregs and the contribution of ILC3s in autoimmune and autoinflammatory diseases. TRIAL REGISTRATION NUMBER: NCT02466217.

The universal effects of low-dose interleukin-2 across 13 autoimmune diseases in a basket clinical trial.

BACKGROUND: A Tregs insufficiency is central to autoimmune and inflammatory diseases pathophysiology and low dose interleukin-2 (IL-2LD) can specifically activate Tregs. OBJECTIVE: To assess IL-2LD therapeutic potential and select diseases for further clinical development, we performed an open-label, phase 2a, disease-finding, "basket trial" involving patients with one of 13 different autoimmune diseases. METHODS: 81 patients treated with IL-2LD (1 million IU/day) for 5 days, followed by fortnightly injections. The first 48 patients received diluted Proleukin®, while the subsequent 33 received ready-to-use ILT-101®. The primary endpoint was the change in Tregs at day-8 compared to baseline. Key secondary endpoints included clinical efficacy assessments using the Clinical Global Impression (CGI) scale, disease-specific scores, and EuroQL-5D-5L. RESULTS: Our study unveiled a universal and significant expansion and activation of Tregs, without concomitant Teffs activation, across all 13 autoimmune diseases. Both Proleukin® and ready-to-use ILT-101® demonstrated identical effects on Tregs. CGI scores reflecting activity, severity, and efficacy were significantly reduced in the overall patient population. Disease-specific clinical scores improved in five of the six disease cohorts with at least six patients, namely ankylosing spondylitis, systemic lupus erythematosus, Behçet's disease, Sjögren's syndrome, and systemic sclerosis. Urticaria was the only severe adverse event related to treatment. CONCLUSION: IL-2LD was well-tolerated, exhibiting specific Treg activation and clinical improvements across the 13 autoimmune diseases. CLINICAL IMPLICATION: Tregs stimulation by IL-2LD is a promising therapeutic strategy and IL-2LD holds considerable promise for integration into combinatorial therapeutic approaches.

Early systemic inflammation induces neurodevelopmental disorders: results from ARTEMIS, a French multicenter study of juvenile rheumatisms and systemic autoimmune and auto-inflammatory disorders and meta-analysis.

Prenatal immune-mediated events are known risk factors for neurodevelopmental disorders in the offspring (NDD). Although the brain continues to develop for years after birth and many postnatal factors alter the regular trajectory of neurodevelopment, little is known about the impact of postnatal immune factors. To fill this gap we set up ARTEMIS, a cohort of juvenile rheumatisms and systemic autoimmune and auto-inflammatory disorders (jRSAID), and assessed their neurodevelopment. We then complemented our results with a systematic review and meta-analysis. In ARTEMIS, we used unsupervised and supervised analysis to determine the influence of jRSAID age at onset (AO) and delay in introduction of disease-modifying therapy (DMT) on NDD (NCT04814862). For the meta-analysis, we searched MEDLINE, EMBASE, PsycINFO, Cochrane, and Web of Science up to April 2022 without any restrictions on language, or article type for studies investigating the co-occurence of jRSAID and NDD (PROSPERO- CRD42020150346). 195 patients were included in ARTEMIS. Classification tree isolated 3 groups of patients (i) A low-risk group (AO > 130 months (m)) with 5% of NDD (ii) A medium-risk group (AO < 130 m and DMT < 2 m) with 20% of NDD (iii) and a high-risk-group (AO < 130 m and DMT > 2 m) with almost half of NDD. For the meta-analysis, 18 studies encompassing a total of (i) 46,267 children with jRSAID; 213,930 children with NDD, and 6,213,778 children as controls were included. We found a positive association between jRSAID and NDD with an OR = 1.44 [95% CI 1.31; 1.57] p < 0.0001, [I2 = 66%, Tau2 = 0.0067, p < 0.01]. Several sensitivity analyses were performed without changing the results. Metaregression confirmed the importance of AO (p = 0.005). Our study supports the association between jRSAID and NDD. AO and DMT have pivotal roles in the risk of developing NDD. We plead for systematic screening of NDD in jRSAID to prevent the functional impact of NDD.

Children with a history of both maternal immune activation and prematurity are not at increased risk of ADHD symptoms.

Maternal autoimmune diseases (AID) are risk factors for Attention Deficit Hyperactivity Disorder (ADHD). Animal studies suggest that maternal immune activation (MIA) is a disease primer for ADHD, with second environmental factor precipitating the onset of the disease. Prematurity is also a major risk factor for ADHD. In this study, we sought to explore the interaction between parental AID and prematurity on ADHD risk in a community sample. Children of AID parents born prematurely appeared at increased odds of ADHD but these two risk factors do not appear to be additive (OR 1.39 [95 CI 0.75; 2.46]). Longitudinal studies with larger numbers of participants are needed.

Mast cells drive pathologic vascular lesions in Takayasu arteritis.

BACKGROUND: Takayasu arteritis (TAK) is a large vessel vasculitis resulting in artery wall remodeling with segmental stenosis and/or aneurysm formation. Mast cells (MCs) are instrumental in bridging cell injury and inflammatory response. OBJECTIVES: This study sought to investigate the contribution of MCs on vessel permeability, angiogenesis, and fibrosis in patients with TAK. METHODS: MC activation and their tissue expression were assessed in sera and in aorta from patients with TAK and from healthy donors (HDs). In vivo permeability was assessed using a modified Miles assay. Subconfluent cultured human umbilic vein endothelial cells and fibroblasts were used in vitro to investigate the effects of MC mediators on angiogenesis and fibrogenesis. RESULTS: This study found increased levels of MC activation markers (histamine and indoleamine 2,3-dioxygenase) in sera of patients with TAK compared with in sera of HDs. Marked expression of MCs was shown in aortic lesions of patients with TAK compared with in those of noninflammatory aorta controls. Using Miles assay, this study showed that sera of patients with TAK significantly increased vascular permeability in vivo as compared with that of HDs. Vessel permeability was abrogated in MC-deficient mice. MCs stimulated by sera of patients with TAK supported neoangiogenesis (increased human umbilic vein endothelial cell proliferation and branches) and fibrosis by inducing increased production of fibronectin, type 1 collagen, and α-smooth muscle actin by fibroblasts as compared to MCs stimulated by sera of HD. CONCLUSIONS: MCs are a key regulator of vascular lesions in patients with TAK and may represent a new therapeutic target in large vessel vasculitis.

Low-dose interleukin-2 therapy in active systemic lupus erythematosus (LUPIL-2): a multicentre, double-blind, randomised and placebo-controlled phase II trial.

OBJECTIVES: A regulatory T cell (Treg) insufficiency due to shortage of interleukin-2 (IL-2) is central to the pathophysiology of systemic lupus erythematosus (SLE). We performed a multicentre, double-blinded, randomised, placebo-controlled phase II proof-of-concept trial to evaluate the efficacy of low-dose IL-2 therapy in patients with SLE having moderate-to-severe disease activity while receiving standard treatment. METHODS: We randomly assigned 100 patients in a 1:1 ratio to receive either 1.5 million IU/day of subcutaneous IL-2 (ILT-101) or placebo for 5 days followed by weekly injections for 12 weeks. Clinical efficacy was assessed at week 12 in a predefined hierarchical analysis of (1) the SLE responder index-4 (SRI-4) response as a primary end point, and of (2) relative and (3) absolute changes in the Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index scores as key secondary end points. RESULTS: The primary end point was not met in the intention-to-treat population (ILT-101: 68%, placebo: 58%; p=0.3439), due to a 100% SRI-4 response rate in the placebo group from the two sites from Bulgaria. A post hoc per-protocol analysis on a prespecified population that excluded patients from these two sites (n=53) showed a statistically significant difference for the SRI-4 response rate (ILT-101: 83.3%; placebo: 51.7%; p=0.0168), and for the two key secondary end points, accompanied by differences in several secondary exploratory end points. ILT-101 was well tolerated and there was no generation of antidrug antibodies. CONCLUSIONS: The post hoc hierarchical analysis of the primary and key secondary end points in a per-protocol population, complemented by the exploratory analyses of multiple other secondary end points, support that low-dose IL-2 is beneficial in active SLE. TRIAL REGISTRATION NUMBER: NCT02955615.

Interferon signature in giant cell arteritis aortitis.

OBJECTIVES: Molecular mechanisms underlying large-vessel involvement in giant cell arteritis (LV-GCA) are largely unknown. Herein, we explore the critical involvement of pro-inflammatory signaling pathways in both aorta and T cells from patients with LV-GCA. METHODS: We analyzed transcriptome and interferon gene signature in inflamed aortas from LV-GCA patients and compared them to non-inflammatory control aorta. Differential transcriptomic analyses of circulating CD4+ and CD8+ T cells were also performed between patients with active GCA (not under any immunosuppressants or corticosteroid doses higher than 10 mg/day by the time of blood collection) and healthy donors. Interferon-alpha serum levels were measured using ultra-sensitive technique (HD-X Simoa Planar Technology) in GCA patients according to disease activity status. RESULTS: Transcriptomic analyses revealed 1042, 1479 and 2075 significantly dysregulated genes for aortas, CD4+ and CD8+ cells from LV-GCA patients, respectively, as compared to controls. A great enrichment for pathways linked to interferons (type I, II and III), JAK/STAT signaling, cytokines and chemokines was seen across aortas and circulating T cells. A type I interferon signature was identified as significantly upregulated in the aorta of patients with LV-GCA, notably regarding EPSTI1 and IFI44L genes. STAT3 was significantly upregulated in both aorta and T cells and appeared as central in related gene networks from LV-GCA patients. Interferon-alpha serum levels were higher in patients with active GCA when compared to those in remission (0.024 vs. 0.011 pg/mL; p = 0.028). CONCLUSION: LV-GCA presents a clear type I interferon signature in aortas, which paves the way for tailored therapeutical targeting.

Low dose IL-2 in patients with steroid-dependent dysimmune manifestations associated with myelodysplastic syndromes: a three-case report.

OBJECTIVES: Systemic inflammatory and autoimmune diseases can be associated with myelodysplastic syndromes. Current treatments (steroids, immunosuppressive agents, biologics) are unsatisfactory because of their low response rate, dependence or adverse events. We aimed at evaluating the effects of low doses of IL-2 (ld-IL2) as a regulatory T-cell inducer in this context. METHODS: We treated three patients with ld-IL2 with myelodysplastic syndromes and an associated dysimmune disorder (polymyalgia rheumatic, relapsing polychondritis associated with Sweet's syndrome and vasculitis with cutaneous and joint involvement, respectively). All three patients were dependent on steroids and refractory to biologics or azacitidine. They received doses of 1-1.5 million units of proleukin/day during 5 days and then every fortnight. RESULTS: The treatment led to a clinical improvement and steroid sparing in 2/3 patients with no serious adverse events, and no progression of the disease. CONCLUSION: Our results support the investigation of ld-IL2 in MDS associated with immune disorders in controlled clinical studies.

High-resolution repertoire analysis reveals a major bystander activation of Tfh and Tfr cells.

T follicular helper (Tfh) and regulatory (Tfr) cells are terminally differentiated cells found in germinal centers (GCs), specialized secondary lymphoid organ structures dedicated to antibody production. As such, follicular T (Tfol) cells are supposed to be specific for immunizing antigens, which has been reported for Tfh cells but is debated for Tfr cells. Here, we used high-throughput T cell receptor (TCR) sequencing to analyze the repertoires of Tfh and Tfr cells, at homeostasis and after immunization with self- or foreign antigens. We observed that, whatever the conditions, Tfh and Tfr cell repertoires are less diverse than those of effector T cells and Treg cells of the same tissues; surprisingly, these repertoires still represent thousands of different sequences, even after immunization with a single antigen that induces a 10-fold increase in Tfol cell numbers. Thorough analysis of the sharing and network of TCR sequences revealed that a specific response to the immunizing antigen can only, but hardly, be detected in Tfh cells immunized with a foreign antigen and Tfr cells immunized with a self-antigen. These antigen-specific responses are obscured by a global stimulation of Tfh and Tfr cells that appears to be antigen-independent. Altogether, our results suggest a major bystander Tfol cell activation during the immune response in the GCs.

Intrathymic adeno-associated virus gene transfer rapidly restores thymic function and long-term persistence of gene-corrected T cells.

BACKGROUND: Patients with T-cell immunodeficiencies are generally treated with allogeneic hematopoietic stem cell transplantation, but alternatives are needed for patients without matched donors. An innovative intrathymic gene therapy approach that directly targets the thymus might improve outcomes. OBJECTIVE: We sought to determine the efficacy of intrathymic adeno-associated virus (AAV) serotypes to transduce thymocyte subsets and correct the T-cell immunodeficiency in a zeta-associated protein of 70 kDa (ZAP-70)-deficient murine model. METHODS: AAV serotypes were injected intrathymically into wild-type mice, and gene transfer efficiency was monitored. ZAP-70-/- mice were intrathymically injected with an AAV8 vector harboring the ZAP70 gene. Thymus structure, immunophenotyping, T-cell receptor clonotypes, T-cell function, immune responses to transgenes and autoantibodies, vector copy number, and integration were evaluated. RESULTS: AAV8, AAV9, and AAV10 serotypes all transduced thymocyte subsets after in situ gene transfer, with transduction of up to 5% of cells. Intrathymic injection of an AAV8-ZAP-70 vector into ZAP-70-/- mice resulted in a rapid thymocyte differentiation associated with the development of a thymic medulla. Strikingly, medullary thymic epithelial cells expressing the autoimmune regulator were detected within 10 days of gene transfer, correlating with the presence of functional effector and regulatory T-cell subsets with diverse T-cell receptor clonotypes in the periphery. Although thymocyte reconstitution was transient, gene-corrected peripheral T cells harboring approximately 1 AAV genome per cell persisted for more than 40 weeks, and AAV vector integration was detected. CONCLUSIONS: Intrathymic AAV-transduced progenitors promote a rapid restoration of the thymic architecture, with a single wave of thymopoiesis generating long-term peripheral T-cell function.

Low-dose IL-2 in children with recently diagnosed type 1 diabetes: a Phase I/II randomised, double-blind, placebo-controlled, dose-finding study.

AIMS/HYPOTHESIS: Low-dose IL-2 (ld-IL2) selectively activates and expands regulatory T cells (Tregs) and thus has the potential to skew the regulatory/effector T (Treg/Teff) cell balance towards improved regulation. We investigated which low doses of IL-2 would more effectively and safely activate Tregs during a 1 year treatment in children with recently diagnosed type 1 diabetes. METHODS: Dose Finding Study of IL-2 at Ultra-low Dose in Children With Recently Diagnosed Type 1 Diabetes (DF-IL2-Child) was a multicentre, double-blinded, placebo-controlled, dose-finding Phase I/II clinical trial conducted in four centres at university hospitals in France: 24 children (7-14 years old) with type 1 diabetes diagnosed within the previous 3 months were randomly assigned 1:1:1:1 to treatment by a centralised randomisation system, leading to a 7/5/6/6 patient distribution of placebo or IL-2 at doses of 0.125, 0.250 or 0.500 million international units (MIU)/m2, given daily for a 5 day course and then fortnightly for 1 year. A study number was attributed to patients by an investigator unaware of the randomisation list and all participants as well as investigators and staff involved in the study conduct and analyses were blinded to treatments. The primary outcome was change in Tregs, expressed as a percentage of CD4+ T cells at day 5. It pre-specified that a ≥60% increase in Tregs from baseline would identify Treg high responders. RESULTS: There were no serious adverse events. Non-serious adverse events (NSAEs) were transient and mild to moderate. In treated patients vs placebo, the commonest NSAE was injection site reaction (37.9% vs 3.4%), whereas other NSAEs were at the same level (23.3% vs 19.2%). ld-IL2 induced a dose-dependent increase in the mean proportion of Tregs, from 23.9% (95% CI -11.8, 59.6) at the lowest to 77.2% (44.7, 109.8) at the highest dose, which was significantly different from placebo for all dose groups. However, the individual Treg responses to IL-2 were variable and fluctuated over time. Seven patients, all among those treated with the 0.250 and 0.500 MIU m-2 day-1 doses, were Treg high responders. At baseline, they had lower Treg proportions in CD4+ cells than Treg low responders, and serum soluble IL-2 receptor α (sIL-2RA) and vascular endothelial growth factor receptor 2 (VEGFR2) levels predicted the Treg response after the 5 day course. There was no significant change in glycaemic control in any of the dose groups compared with placebo. However, there was an improved maintenance of induced C-peptide production at 1 year in the seven Treg high responders as compared with low responders. CONCLUSIONS/INTERPRETATION: The safety profile at all doses, the dose-dependent effects on Tregs and the observed variability of the Treg response to ld-IL2 in children with newly diagnosed type 1 diabetes call for use of the highest dose in future developments. The better preservation of insulin production in Treg high responders supports the potential of Tregs in regulating autoimmunity in type 1 diabetes, and warrants pursuing the investigation of ld-IL2 for its treatment and prevention. TRIAL REGISTRATION: ClinicalTrials.gov NCT01862120. FUNDING: Assistance Publique-Hôpitaux de Paris, Investissements d'Avenir programme (ANR-11-IDEX-0004-02, LabEx Transimmunom and ANR-16-RHUS-0001, RHU iMAP) and European Research Council Advanced Grant (FP7-IDEAS-ERC-322856, TRiPoD).

Targeting JAK/STAT pathway in Takayasu's arteritis.

OBJECTIVE: Takayasu's arteritis (TAK) is a large vessel vasculitis with important infiltration of proinflammatory T cells in the aorta and its main branches, but its aetiology is still unknown. Our work aims to explore the involvement of Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT) signalling pathway in proinflammatory T cells differentiation and disease activity of TAK. METHODS: We analysed transcriptome and interferons gene signatures of fluorescence-activated cell sorting (FACS-sorted) CD4+ and CD8+ T cells from healthy donors (HD) and in 25 TAK (median age of 37.6 years including 21 active TAK with National Institutes of Health (NIH) score >1). Then we tested, in vitro and in vivo, the effects of JAK inhibitors (JAKinibs) in TAK. RESULTS: Transcriptome analysis showed 248 and 432 significantly dysregulated genes for CD4+ and CD8+ samples between HD and TAK, respectively. Among dysregulated genes, we highlighted a great enrichment for pathways linked to type I and type II interferons, JAK/STAT and cytokines/chemokines-related signalling in TAK. We confirmed by Real Time Reverse Transcription Polymerase Chain Reaction (RT-qPCR) the upregulation of type I interferons gene signature in TAK as compared with HD. JAKinibs induced both in vitro and in vivo a significant reduction of CD25 expression by CD4+ and CD8+ T cells, a significant decrease of type 1 helper T cells (Th1) and Th17 cells and an increase of Tregs cells in TAK. JAKinibs also decreased C reactive protein level, NIH score and corticosteroid dose in TAK patients. CONCLUSIONS: JAK/STAT signalling pathway is critical in the pathogenesis of TAK and JAKinibs may be a promising therapy.

Pre-treatment with IL2 gene therapy alleviates Staphylococcus aureus arthritis in mice.

BACKGROUND: Staphylococcus aureus (S. aureus) arthritis is one of the most detrimental joint diseases known and leads to severe joint destruction within days. We hypothesized that the provision of auxiliary immunoregulation via an expanded compartment of T regulatory cells (Tregs) could dampen detrimental aspects of the host immune response whilst preserving its protective nature. Administration of low-dose interleukin 2 (IL2) preferentially expands Tregs, and is being studied as a treatment choice in several autoimmune conditions. We aimed to evaluate the role of IL2 and Tregs in septic arthritis using a well-established mouse model of haematogenously spred S. aureus arthritis. METHODS: C57BL/6 or NMRI mice we intravenously (iv) injected with a defined dose of S. aureus LS-1 or Newman and the role of IL2 and Tregs were assessed by the following approaches: IL2 was endogenously delivered by intraperitoneal injection of a recombinant adeno-associated virus vector (rAAV) before iv S. aureus inoculation; Tregs were depleted before and during S. aureus arthritis using antiCD25 antibodies; Tregs were adoptively transferred before induction of S. aureus arthritis and finally, recombinant IL2 was used as a treatment starting day 3 after S. aureus injection. Studied outcomes included survival, weight change, bacterial clearance, and joint damage. RESULTS: Expansion of Tregs induced by IL2 gene therapy prior to disease onset does not compromise host resistance to S. aureus infection, as the increased proportions of Tregs reduced the arthritis severity as well as the systemic inflammatory response, while simultaneously preserving the host's ability to clear the infection. CONCLUSIONS: Pre-treatment with IL2 gene therapy dampens detrimental immune responses but preserves appropriate host defense, which alleviates S. aureus septic arthritis in a mouse model.

TLR9 signalling in HCV-associated atypical memory B cells triggers Th1 and rheumatoid factor autoantibody responses.

BACKGROUND & AIMS: Hepatitis C virus (HCV) infection contributes to the development of autoimmune disorders such as cryoglobulinaemia vasculitis (CV). However, it remains unclear why only some individuals with HCV develop HCV-associated CV (HCV-CV). HCV-CV is characterized by the expansion of anergic CD19+CD27+CD21low/- atypical memory B cells (AtMs). Herein, we report the mechanisms by which AtMs participate in HCV-associated autoimmunity. METHODS: The phenotype and function of peripheral AtMs were studied by multicolour flow cytometry and co-culture assays with effector T cells and regulatory T cells in 20 patients with HCV-CV, 10 chronicallyHCV-infected patients without CV and 8 healthy donors. We performed gene expression profile analysis of AtMs stimulated or not by TLR9. Immunoglobulin gene repertoire and antibody reactivity profiles of AtM-expressing IgM antibodies were analysed following single B cell FACS sorting and expression-cloning of monoclonal antibodies. RESULTS: The Tbet+CD11c+CD27+CD21- AtM population is expanded in patients with HCV-CV compared to HCV controls without CV. TLR9 activation of AtMs induces a specific transcriptional signature centred on TNFα overexpression, and an enhanced secretion of TNFα and rheumatoid factor-type IgMs in patients with HCV-CV. AtMs stimulated through TLR9 promote type 1 effector T cell activation and reduce the proliferation of CD4+CD25hiCD127-/lowFoxP3+ regulatory T cells. AtM expansions display intraclonal diversity with immunoglobulin features of antigen-driven maturation. AtM-derived IgM monoclonal antibodies do not react against ubiquitous autoantigens or HCV antigens including NS3 and E2 proteins. Rather, AtM-derived antibodies possess rheumatoid factor activity and target unique epitopes on the human IgG-Fc region. CONCLUSION: Our data strongly suggest a central role for TLR9 activation of AtMs in driving HCV-CV autoimmunity through rheumatoid factor production and type 1 T cell responses. LAY SUMMARY: B cells are best known for their capacity to produce antibodies, which often play a deleterious role in the development of autoimmune diseases. During chronic hepatitis C, self-reactive B cells proliferate and can be responsible for autoimmune symptoms (arthritis, purpura, neuropathy, renal disease) and/or lymphoma. Direct-acting antiviral therapy clears the hepatitis C virus and eliminates deleterious B cells.

Immunological and clinical effects of low-dose interleukin-2 across 11 autoimmune diseases in a single, open clinical trial.

OBJECTIVE: Regulatory T cells (Tregs) prevent autoimmunity and control inflammation. Consequently, any autoimmune or inflammatory disease reveals a Treg insufficiency. As low-dose interleukin-2 (ld-IL2) expands and activates Tregs, it has a broad therapeutic potential. AIM: We aimed to assess this potential and select diseases for further clinical development by cross-investigating the effects of ld-IL2 in a single clinical trial treating patients with 1 of 11 autoimmune diseases. METHODS: We performed a prospective, open-label, phase I-IIa study in 46 patients with a mild to moderate form of either rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, psoriasis, Behcet's disease, granulomatosis with polyangiitis, Takayasu's disease, Crohn's disease, ulcerative colitis, autoimmune hepatitis and sclerosing cholangitis. They all received ld-IL2 (1 million IU/day) for 5 days, followed by fortnightly injections for 6 months. Patients were evaluated by deep immunomonitoring and clinical evaluation. RESULTS: ld-IL2 was well tolerated whatever the disease and the concomitant treatments. Thorough supervised and unsupervised immunomonitoring demonstrated specific Treg expansion and activation in all patients, without effector T cell activation. Indication of potential clinical efficacy was observed. CONCLUSION: The dose of IL-2 and treatment scheme used selectively activate and expand Tregs and are safe across different diseases and concomitant treatments. This and preliminary indications of clinical efficacy should licence the launch of phase II efficacy trial of ld-IL2 in various autoimmune and inflammatory diseases. TRIAL REGISTRATION NUMBER: NCT01988506.

Direct-Acting Antiviral Therapy Restores Immune Tolerance to Patients With Hepatitis C Virus-Induced Cryoglobulinemia Vasculitis.

BACKGROUND & AIMS: Interferon-free direct-acting antiviral (DAA) therapies are effective in patients with hepatitis C virus-induced cryoglobulinemia vasculitis (HCV-CV). We analyzed blood samples from patients with HCV-CV before and after DAA therapy to determine mechanisms of these drugs and their effects on cellular immunity. METHODS: We performed a prospective study of 27 consecutive patients with HCV-CV (median age, 59 y) treated with DAA therapy (21 patients received sofosbuvir plus ribavirin for 24 weeks, 4 patients received sofosbuvir plus daclatasvir for 12 weeks, and 2 patients received sofosbuvir plus simeprevir for 12 weeks) in Paris, France. Blood samples were collected from these patients before and after DAA therapy, and also from 12 healthy donors and 12 individuals with HCV infection without CV. HCV load, cryoglobulins, and cytokines were quantified by flow cytometry, cytokine multiplex assays, and enzyme-linked immunosorbent assay. RESULTS: Twenty-four patients (88.9%) had a complete clinical response of CV to DAA therapy at week 24, defined by improvement of all the affected organs and the absence of relapse. Compared with healthy donors and patients with HCV infection without CV, patients with HCV-CV, before DAA therapy, had a lower percentage of CD4+CD25hiFoxP3+ regulatory T cells (P < .01), but higher proportions of IgM+CD21-/low memory B cells (P < .05), CD4+IFNγ+ cells (P < .01), CD4+IL17A+ cells (P < .01), and CD4+CXCR5+interleukin 21+ follicular T-helper (Tfh) cells (P < .01). In patients with HCV-CV, there was a negative correlation between numbers of IgM+CD21-/low memory B cells and T-regulatory cells (P = .03), and positive correlations with numbers of Tfh cells (P = .03) and serum levels of cryoglobulin (P = .01). DAA therapy increased patients' numbers of T-regulatory cells (1.5% ± 0.18% before therapy vs 2.1% ± 0.18% after therapy), decreased percentages of IgM+CD21-/low memory B cells (35.7% ± 6.1% before therapy vs 14.9% ± 3.8% after therapy), and decreased numbers of Tfh cells (12% ± 1.3% before therapy vs 8% ± 0.9% after therapy). Expression levels of B lymphocyte stimulator receptor 3 and programmed cell death 1 on B cells increased in patients with HCV-CV after DAA-based therapy (mean fluorescence units, 37 ± 2.4 before therapy vs 47 ± 2.6 after therapy, P < .01; and 29 ± 7.3 before therapy vs 48 ± 9.3 after therapy, P < .05, respectively). CONCLUSIONS: In a prospective clinical trial of patients with HCV-CV, DAA-based therapy restored disturbances in peripheral B- and T-cell homeostasis.

Retrovirus-Based Virus-Like Particle Immunogenicity and Its Modulation by Toll-Like Receptor Activation.

Retrovirus-derived virus-like particles (VLPs) are particularly interesting vaccine platforms, as they trigger efficient humoral and cellular immune responses and can be used to display heterologous antigens. In this study, we characterized the intrinsic immunogenicity of VLPs and investigated their possible adjuvantization by incorporation of Toll-like receptor (TLR) ligands. We designed a noncoding single-stranded RNA (ncRNA) that could be encapsidated by VLPs and induce TLR7/8 signaling. We found that VLPs efficiently induce in vitro dendritic cell activation, which can be improved by ncRNA encapsidation (ncRNAVLPs). Transcriptome studies of dendritic cells harvested from the spleens of immunized mice identified antigen presentation and immune activation as the main gene expression signatures induced by VLPs, while TLR signaling and Th1 signatures characterize ncRNAVLPs. In vivo and compared with standard VLPs, ncRNAVLPs promoted Th1 responses and improved CD8+ T cell proliferation in a MyD88-dependent manner. In an HIV vaccine mouse model, HIV-pseudotyped ncRNAVLPs elicited stronger antigen-specific cellular and humoral responses than VLPs. Altogether, our findings provide molecular evidence for a strong vaccine potential of retrovirus-derived VLPs that can be further improved by harnessing TLR-mediated immune activation.IMPORTANCE We previously reported that DNA vaccines encoding antigens displayed in/on retroviral VLPs are more efficient than standard DNA vaccines at inducing cellular and humoral immune responses. We aimed to decipher the mechanisms and investigated the VLPs' immunogenicity independently of DNA vaccination. We show that VLPs have the ability to activate antigen-presenting cells directly, thus confirming their intrinsic immunostimulatory properties and their potential to be used as an antigenic platform. Notably, this immunogenicity can be further improved and/or oriented by the incorporation into VLPs of ncRNA, which provides further TLR-mediated activation and Th1-type CD4+ and CD8+ T cell response orientation. Our results highlight the versatility of retrovirus-derived VLP design and the value of using ncRNA as an intrinsic vaccine adjuvant.

Deep phenotyping of immune cell populations by optimized and standardized flow cytometry analyses.

Multicolor flow cytometry is a technology of choice for phenotyping of immune cells, and it can be used routinely for the follow up of patients in clinical trials. But it is challenging to define combinations of conjugated antibodies that efficiently allow the detailed analysis of major immune cell subsets and the identification of rare cell populations. In a collaborative work among the Immunology, Immunopathology, Immunotherapy (I3 ) laboratory, and the laboratory of immunomonitoring in oncology (L.I.O), we developed and validated 12 different 10-color flow cytometry panels that allow the deep immunophenotyping of cells from whole blood for the follow up of autoimmune and cancer patients. Here, we describe these optimized flow cytometry panels, showing that they provide the advanced analysis of T cells (including regulatory T cells), B cells, NK cells, MAIT cells, myeloid cells, monocytes, and dendritic cells. Most of the panels have been dried to improve standardization of the labeling and the entire procedure can be performed on less than 2 ml of whole blood. These deep immunophenotyping flow cytometry panels constitute a powerful tool for the monitoring of immune blood cells and will hopefully lead to the discovery of new biomarkers and potential therapeutic targets in autoimmune and cancer clinical trials. © 2018 International Society for Advancement of Cytometry.

Regulatory T Cells Orchestrate Similar Immune Evasion of Fetuses and Tumors in Mice.

Embryos and tumors are both masses of dividing cells expressing foreign Ags, but they are not rejected by the immune system. We hypothesized that similar tolerogenic mechanisms prevent their rejection. Global comparison of fetal and tumor microenvironments through transcriptomics in mice revealed strikingly similar and dramatic decreases in expression of numerous immune-related pathways, including Ag presentation and T cell signaling. Unsupervised analyses highlighted the parallel kinetics and similarities of immune signature downregulation, from the very first days after tumor or embryo implantation. Besides upregulated signatures related to cell proliferation, the only significant signatures shared by the two conditions across all biological processes and all time points studied were downmodulated immune response signatures. Regulatory T cell depletion completely reverses this immune downmodulation to an immune upregulation that leads to fetal or tumor immune rejection. We propose that evolutionarily selected mechanisms that protect mammalian fetuses from immune attack are hijacked to license tumor development.