HIV-1 infection is characterized by a chronic activation of the immune system and suppressed function of T lymphocytes. Regulatory CD4+ CD25high FoxP3+CD127low T cells (Treg) play a key role in both conditions. Here, we show that HIV-1 positive patients have a significant increase of Treg-associated expression of CD39/ENTPD1, an ectoenzyme which in concert with CD73 generates adenosine. We show in vitro that the CD39/adenosine axis is involved in Treg suppression in HIV infection. Treg inhibitory effects are relieved by CD39 down modulation and are reproduced by an adenosine-agonist in accordance with a higher expression of the adenosine A2A receptor on patients' T cells. Notably, the expansion of the Treg CD39+ correlates with the level of immune activation and lower CD4+ counts in HIV-1 infected patients. Finally, in a genetic association study performed in three different cohorts, we identified a CD39 gene polymorphism that was associated with down-modulated CD39 expression and a slower progression to AIDS.

Capsule summary 55This article demonstrates that JAK inhibition represents a highly promising and well-tolerated 56 therapy for STING-associated vasculopathy, and which may also be relevant to the treatment 57 of other type I interferonopathies. 58 59Key words: Stimulator of Interferon genes, TMEM173, Janus kinase 1/2 inhibitor, type I 60 interferonopathy, interstitial lung disease, vasculopathy. 61 To the Editor: 62Gain-of-function mutations in TMEM173 encoding STING (Stimulator of Interferon Genes) 63 underlie a novel type I interferonopathy, 1 termed SAVI (STING-associated vasculopathy with 64 onset in infancy). 2,3 This disease is associated with high childhood morbidity and mortality. 65 STING is a central component of DNA sensing that leads to the induction of type I 66 interferons (IFN), which in turn drives the expression of IFN-stimulated genes (ISGs) through 67 the engagement of a common receptor and subsequent activation of Janus kinase 1 (JAK1) 68 and tyrosine kinase 2 (TYK2). 69We describe, for the first time, the use and efficacy of ruxolitinib, a selective oral JAK1/2 70 inhibitor, in three children with TMEM173-activating mutations over 6 to 18 months of 71 follow-up. The patients, aged between 5 and 12 years, exhibited the phenotypic variability 72 associated with TMEM173-activating mutations, 2,3,4 with lung disease and systemic 73 inflammation being the major features in P1 and P3, whilst in P2 skin involvement was most 74 prominent (Fig 1 and see Supplemental Text, Fig E3, and Table E1 in the Online Repository). 75There was minimal response to a broad spectrum of immunosuppressive therapies including 76 steroids, methotrexate and anti-CD20 monoclonal antibodies. 77 78An increased expression of ISGs, a so-called type I IFN signature, 5 was observed in all three 79 patients (see Fig E1, A in the Online Repository). Increased levels of STAT1 phosphorylation 80 were recorded in patient T lymphocytes (P1, P2, P3), T cultured lymphoblasts (P1) and 81 primary fibroblasts (P3) compared to controls (see Fig E2, A in the Online Repository). Liu et 82 al. demonstrated that, in vitro, three JAK1 inhibitors (ruxolitinib, tofacitinib and baricitinib) 83 were able to block the constitutive phosphorylation of STAT1 in lymphocytes from 84 TMEM173-mutated patients, 2 and we saw that exposure to ruxolitinib inhibited the 85 constitutive phosphorylation of STAT1 and decreased the expression of IL-6 and 3 ISGs 86 tested in T lymphoblasts from P1 (see Fig E2, B, C in the Online Repository). Considering the 87 severity of the phenotype and the poor response to conventional immunosuppressive 88 therapies, we hypothesized that JAK1 inhibition would block IFN signaling in the context of 89 activating mutations in TMEM173. 90 91We observed a marked positive effect on all aspects of the phenotype in all three treated 92 children. There was a general improvement in patient-reported well-being, a reduction of 93 febrile episodes, an almost complete resolution of the associated cutaneous lesions and a 94 major impr...

The mechanisms by which Regulatory T cells suppress IL-2 production of effector CD4+ T cells in pathological conditions are unclear. A subpopulation of human Treg expresses the ectoenzyme CD39, which in association with CD73 converts ATP/ADP/AMP to adenosine. We show here that Treg/CD39+ suppress IL-2 expression of activated CD4+ T-cells more efficiently than Treg/CD39−. This inhibition is due to the demethylation of an essential CpG site of the il-2 gene promoter, which was reversed by an anti-CD39 mAb. By recapitulating the events downstream CD39/adenosine receptor (A2AR) axis, we show that A2AR agonist and soluble cAMP inhibit CpG site demethylation of the il-2 gene promoter. A high frequency of Treg/CD39+ is associated with a low clinical outcome in HIV infection. We show here that CD4+ T-cells from HIV-1 infected individuals express high levels of A2AR and intracellular cAMP. Following in vitro stimulation, these cells exhibit a lower degree of demethylation of il-2 gene promoter associated with a lower expression of IL-2, compared to healthy individuals. These results extend previous data on the role of Treg in HIV infection by filling the gap between expansion of Treg/CD39+ in HIV infection and the suppression of CD4+ T-cell function through inhibition of IL-2 production.

Idiopathic myelofibrosis (IMF) is a chronic myeloproliferative disorder characterized by megakaryocyte hyperplasia and bone marrow fibrosis. Biologically, an autonomous megakaryocyte growth and differentiation is noticed, which contributes to the megakaryocyte accumulation. To better understand the molecular mechanisms involved in this spontaneous growth, we searched for genes differentially expressed between normal megakaryocytes requiring cytokines to grow and IMF spontaneously proliferating megakaryocytes. Using a differential display technique, we found that the immunophilin FKBP51 was 2 to 8 times overexpressed in megakaryocytes derived from patients' CD34 ؉ cells in comparison to normal megakaryocytes. Overexpression was moderate and confirmed in 8 of 10 patients, both at the mRNA and protein levels. Overexpression of FKBP51 in a UT-7/Mpl cell line and in normal CD34 ؉ cells induced a resistance to apoptosis mediated by cytokine deprivation with no effect on proliferation.