Dysregulation in B-cell responses and T follicular helper cell function in ADA2 deficiency patients.

Adenosine deaminase 2 deficiency (DADA2) is an autoinflammatory disease characterized by inflammatory vasculopathy, early strokes associated often with hypogammaglobulinemia. Pure red cell aplasia, thrombocytopenia, and neutropenia have been reported. The defect is due to biallelic loss of function of ADA2 gene, coding for a protein known to regulate the catabolism of extracellular adenosine. We therefore investigated immune phenotype and B- and T-cell responses in 14 DADA2 patients to address if ADA2 mutation affects B- and T-cell function. Here, we show a significant decrease in memory B cells, in particular class switch memory, and an expansion of CD21low B cells in DADA2 patients. In vitro stimulated B lymphocytes were able to secrete nonfunctional ADA2 protein, suggesting a cell intrinsic defect resulting in an impairment of B-cell proliferation and differentiation. Moreover, CD4+ and CD8+ T cells were diminished; however, the frequency of circulating T follicular helper cells was significantly increased but they had an impairment in IL-21 production possibly contributing to an impaired B cell help. Our findings suggest that ADA2 mutation could lead to a B-cell intrinsic defect but also to a defective Tfh cell function, which could contribute to the immunodeficient phenotype reported in DADA2 patients.

A novel knock-in mouse model of cryopyrin-associated periodic syndromes with development of amyloidosis: Therapeutic efficacy of proton pump inhibitors.

BACKGROUND: Cryopyrin-associated periodic syndromes (CAPS) are a group of autoinflammatory diseases linked to gain-of-function mutations in the NOD-like receptor family, pyrin domain containing 3 (NLRP3) gene, which cause uncontrolled IL-1ß secretion. Proton pump inhibitors (PPIs), which are commonly used as inhibitors of gastric acid production, also have anti-inflammatory properties, protect mice from sepsis, and prevent IL-1ß secretion by monocytes from patients with CAPS. OBJECTIVE: We sought to develop a novel Nlrp3 knock-in (KI) mouse model of CAPS to study amyloidosis, a severe CAPS complication, and test novel therapeutic approaches. METHODS: We generated KI mice by engineering the N475K mutation, which is associated with the CAPS phenotype, into the mouse Nlrp3 gene. KI and wild-type mice received PPIs or PBS intraperitoneally and were analyzed for survival, inflammation, cytokine secretion, and amyloidosis development. RESULTS: Mutant Nlrp3 KI mice displayed features that recapitulate the immunologic and clinical phenotype of CAPS. They showed systemic inflammation with high levels of serum proinflammatory cytokines, inflammatory infiltrates in various organs, and amyloid deposits in the spleen, liver, and kidneys. Toll-like receptor stimulated macrophages from KI mice secreted high levels of IL-1ß, IL-18, and IL-1α but low amounts of IL-1 receptor antagonist. Treatment of KI mice with PPIs had a clear clinical effect, showing a reduction in inflammatory manifestations, regression of amyloid deposits, and normalization of proinflammatory and anti-inflammatory cytokine production by macrophages. CONCLUSION: Nlrp3 KI mice displayed a CAPS phenotype with many characteristics of autoinflammation, including amyloidosis. The therapeutic effectiveness of PPIs associated with a lack of toxicity indicates that these drugs could represent relevant adjuvants to the anti-IL-1 drugs in patients with CAPS and other IL-1-driven diseases.

Efficacy and Adverse Events During Janus Kinase Inhibitor Treatment of SAVI Syndrome.

OBJECTIVES: Mutations affecting the TMEM173 gene cause STING-associated vasculopathy with onset in infancy (SAVI). No standard immunosuppressive treatment approach is able to control disease progression in patients with SAVI. We studied the efficacy and safety of targeting type I IFN signaling with the Janus kinase inhibitor, ruxolitinib. METHODS: We used DNA sequencing to identify mutations in TMEM173 in patients with peripheral blood type I IFN signature. The JAK1/2 inhibitor ruxolitinib was administered on an off-label basis. RESULTS: We identified three patients with SAVI presenting with skin involvement and progressive severe interstitial lung disease. Indirect echocardiographic signs of pulmonary hypertension were present in one case. Following treatment with ruxolitinib, we observed improvements of respiratory function including increased forced vital capacity in two patients, with discontinuation of oxygen therapy and resolution of echocardiographic abnormalities in one case. Efficacy was persistent in one patient and only transitory in the other two patients. Clinical control of skin complications was obtained, and one patient discontinued steroid treatment. One patient, who presented with kidney involvement, showed resolution of hematuria. One patient experienced increased recurrence of severe viral respiratory infections. Monitoring of peripheral blood type I interferon signature during ruxolitinib treatment did not show a stable decrease. CONCLUSIONS: We conclude that targeting type I IFN receptor signaling may represent a promising therapeutic option for a subset of patients with SAVI syndrome and severe lung involvement. However, the occurrence of viral respiratory infection might represent an important cautionary note for the application of such form of treatment.

Type I interferon pathway activation in COPA syndrome.

Mutations of the COPA gene cause an immune dysregulatory disease characterised by polyarticular arthritis and progressive interstitial lung disease with pulmonary haemorrhages. We report the case of a young girl that presented at age 3 with polyarticular arthritis, chronic cough and high titer rheumatoid factor. Radiologic imaging showed interstitial lung disease with tree-in-a-bud nodules and air-filled cysts. Targeted genetic analysis of COPA gene showed the reported c.698G>A mutation. The patient was lost to follow up for 3years during which therapy was discontinued with the development of joint damage and deformities. Analysis of peripheral blood showed activation of type 1 interferon pathway, which was also confirmed in 4 previously reported COPA patients. Our observations underline the importance of early treatment in COPA disease to avoid loss of joint function. Furthermore, our results suggest a role for type 1 interferon in disease pathogenesis opening the possibility for targeted therapeutic approaches.

Murine Rankl-/- Mesenchymal Stromal Cells Display an Osteogenic Differentiation Defect Improved by a RANKL-Expressing Lentiviral Vector.

Autosomal recessive osteopetrosis (ARO) is a severe bone disease characterized by increased bone density due to impairment in osteoclast resorptive function or differentiation. Hematopoietic stem cell transplantation is the only available treatment; however, this therapy is not effective in RANKL-dependent ARO, since in bone this gene is mainly expressed by cells of mesenchymal origin. Of note, whether lack of RANKL production might cause a defect also in the bone marrow (BM) stromal compartment, possibly contributing to the pathology, is unknown. To verify this possibility, we generated and characterized BM mesenchymal stromal cell (BM-MSC) lines from wild type and Rankl-/- mice, and found that Rankl-/- BM-MSCs displayed reduced clonogenicity and osteogenic capacity. The differentiation defect was significantly improved by lentiviral transduction of Rankl-/- BM-MSCs with a vector stably expressing human soluble RANKL (hsRANKL). Expression of Rankl receptor, Rank, on the cytoplasmic membrane of BM-MSCs pointed to the existence of an autocrine loop possibly activated by the secreted cytokine. Based on the close resemblance of RANKL-defective osteopetrosis in humans and mice, we expect that our results are also relevant for RANKL-dependent ARO patients. Data obtained in vitro after transduction with a lentiviral vector expressing hsRANKL would suggest that restoration of RANKL production might not only rescue the defective osteoclastogenesis of this ARO form, but also improve a less obvious defect in the osteoblast lineage, thus possibly achieving higher benefit for the patients, when the approach is translated to clinics. Stem Cells 2017;35:1365-1377.

CD70 Deficiency due to a Novel Mutation in a Patient with Severe Chronic EBV Infection Presenting As a Periodic Fever.

Primary immunodeficiencies with selective susceptibility to EBV infection are rare conditions associated with severe lymphoproliferation. We followed a patient, son of consanguineous parents, referred to our center for recurrent periodic episodes of fever associated with tonsillitis and adenitis started after an infectious mononucleosis and responsive to oral steroid. An initial diagnosis of periodic fever, aphthous stomatitis, pharyngitis, cervical adenitis syndrome was done. In the following months, recurrent respiratory infections and episodes of keratitis were also observed, together with a progressive reduction of immunoglobulin levels and an increase of CD20+ cells. Cell sorting and EBV PCR showed 25,000 copies for 100,000 leukocytes with predominant infection of B lymphocytes. Lymph node's biopsy revealed reactive lymphadenopathy with paracortical involvement consistent with a chronic EBV infection. Molecular analysis of XIAP, SHA2D1A, ITK, and CD27 genes did not detect any pathogenic mutation. The patients underwent repeated courses of anti-CD20 therapy with only a partial control of the disease, followed by stem cell transplantation with a complete normalization of clinical and immunological features. Whole exome sequencing of the trio was performed. Among the variants identified, a novel loss of function homozygous c.163-2A>G mutation of the CD70 gene, affecting the exon 2 AG-acceptor splice site, fit the expected recessive model of inheritance. Indeed, deficiency of both CD27, and, more recently, of its ligand CD70, has been reported as a cause of EBV-driven lymphoproliferation and hypogammaglobulinemia. Cell surface analysis of patient-derived PHA-T cell blasts and EBV-transformed lymphoblastoid cell lines confirmed absence of CD70 expression. In conclusion, we describe a case of severe chronic EBV infection caused by a novel mutation of CD70 presenting with recurrent periodic fever.