Immunological characteristics and T cell receptor clonal diversity in children with systemic juvenile idiopathic arthritis undergoing T cell depleted autologous stem cell transplantation.

Children with systemic Juvenile Idiopathic Arthritis (sJIA), the most severe subtype of JIA, are at risk of from destructive polyarthritis and growth failure, and corticosteroids as part of conventional treatment can result in osteoporosis and growth delay. In children where there is failure or toxicity from drug therapies, disease has been successfully controlled by T cell depleted autologous stem cell transplantation (ASCT). At present, the immunological basis underlying remission post ASCT is unknown. Immune reconstitution of T, B, NK, NK-T cell and monocytes, in parallel with T cell receptor diversity by analysis of beta variable region (TCRVb) complementarity determining region-3 (CDR3) using spectratyping and sequencing, were studied in 5 children with sJIA before and after ASCT. At time of follow up (mean 11.5 years), 4 patients remain in complete remission, while 1 child had relapsed within 1 month of transplant. The CD8(+) TCRVb repertoire was highly oligoclonal early in immune reconstitution and re-emergence of pre-transplant TCRVb CDR3 dominant peaks was observed post transplant in certain TCRVb families. Further, re-emergence of pre-ASCT clonal sequences in addition to new sequences was identified post transplant. These results suggest that a chimeric TCR repertoire, comprising T cell clones developed before and after transplant, can be associated with clinical remission from severe arthritis. This article is protected by copyright. All rights reserved

Identification of Heterozygous Single- and Multi-exon Deletions in IL7R by Whole Exome Sequencing

PURPOSE: We aimed to achieve a retrospective molecular diagnosis by applying state-of-the-art genomic sequencing methods to past patients with T-B+NK+ severe combined immunodeficiency (SCID). We included identification of copy number variations (CNVs) by whole exome sequencing (WES) using the CNV calling method ExomeDepth to detect gene alterations for which routine Sanger sequencing analysis is not suitable, such as large heterozygous deletions. METHODS: Of a total of 12 undiagnosed patients with T-B+NK+ SCID, we analyzed eight probands by WES, using GATK to detect single nucleotide variants (SNVs) and small insertions and deletions (INDELs) and ExomeDepth to detect CNVs. RESULTS: We found heterozygous single- or multi-exon deletions in IL7R, a known disease gene for autosomal recessive T-B+NK+ SCID, in four families (seven patients). In three families (five patients), these deletions coexisted with a heterozygous splice site or nonsense mutation elsewhere in the same gene, consistent with compound heterozygosity. In our cohort, about a quarter of T-B+NK+ SCID patients (26%) had such compound heterozygous IL7R deletions. CONCLUSIONS: We show that heterozygous IL7R exon deletions are common in T-B+NK+ SCID and are detectable by WES. They should be considered if Sanger sequencing fails to detect homozygous or compound heterozygous IL7R SNVs or INDELs

Allogeneic hematopoietic stem cell transplantation for severe, refractory juvenile idiopathic arthritis.

Patients with juvenile idiopathic arthritis (JIA) can experience a severe disease course, with progressive destructive polyarthritis refractory to conventional therapy with disease-modifying antirheumatic drugs including biologics, as well as life-threatening complications including macrophage activation syndrome (MAS). Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative immunomodulatory strategy for patients with such refractory disease. We treated 16 patients in 5 transplant centers between 2007 and 2016: 11 children with systemic JIA and 5 with rheumatoid factor-negative polyarticular JIA; all were either refractory to standard therapy, had developed secondary hemophagocytic lymphohistiocytosis/MAS poorly responsive to treatment, or had failed autologous HSCT. All children received reduced toxicity fludarabine-based conditioning regimens and serotherapy with alemtuzumab. Fourteen of 16 patients are alive with a median follow-up of 29 months (range, 2.8-96 months). All patients had hematological recovery. Three patients had grade II-IV acute graft-versus-host disease. The incidence of viral infections after HSCT was high, likely due to the use of alemtuzumab in already heavily immunosuppressed patients. All patients had significant improvement of arthritis, resolution of MAS, and improved quality of life early following allo-HSCT; most importantly, 11 children achieved complete drug-free remission at the last follow-up. Allo-HSCT using alemtuzumab and reduced toxicity conditioning is a promising therapeutic option for patients with JIA refractory to conventional therapy and/or complicated by MAS. Long-term follow-up is required to ascertain whether disease control following HSCT continues indefinitely

Biallelic RIPK1 mutations in humans cause severe immunodeficiency, arthritis, and intestinal inflammation.

RIPK1 (receptor-interacting serine/threonine kinase 1) is a master regulator of signaling pathways leading to inflammation and cell death and is of medical interest as a drug target. We report four patients from three unrelated families with complete RIPK1 deficiency caused by rare homozygous mutations. The patients suffered from recurrent infections, early-onset inflammatory bowel disease, and progressive polyarthritis. They had immunodeficiency with lymphopenia and altered production of various cytokines revealed by whole-blood assays. In vitro, RIPK1-deficient cells showed impaired mitogen-activated protein kinase activation and cytokine secretion and were prone to necroptosis. Hematopoietic stem cell transplantation reversed cytokine production defects and resolved clinical symptoms in one patient. Thus, RIPK1 plays a critical role in the human immune system

Defective Leukocyte Adhesion and Chemotaxis Contributes to Combined Immunodeficiency in Humans with Autosomal Recessive MST1 Deficiency.

PURPOSE: To investigate the clinical and functional aspects of MST1 (STK4) deficiency in a profoundly CD4-lymphopenic kindred with a novel homozygous nonsense mutation in STK4. Although recent studies have described the cellular effects of murine Mst1 deficiency, the phenotype of MST1-deficient human lymphocytes has yet to be fully explored. Patient lymphocytes were therefore investigated in the context of current knowledge of murine Mst1 deficiency. METHODS: Genetic etiology was identified by whole exome sequencing of genomic DNA from two siblings, combined with linkage analysis in the wider family. MST1 protein expression was assessed by immunoblotting. The ability of patient lymphocytes to adhere to ICAM-1 under flow conditions was measured, and transwell assays were used to assess chemotaxis. Chemokine receptor expression was examined by flow cytometry and receptor signalling by immunoblotting. RESULTS: A homozygous nonsense mutation in STK4 (c.442C > T, p.Arg148Stop) was found in the patients, leading to a lack of MST1 protein expression. Patient leukocytes exhibited deficient chemotaxis after stimulation with CXCL11, despite preserved expression of CXCR3. Patient lymphocytes were also unable to bind effectively to immobilised ICAM-1 under flow conditions, in keeping with a failure to develop high affinity binding. CONCLUSION: The observed abnormalities of adhesion and migration imply a profound trafficking defect among human MST1-deficient lymphocytes. By analogy with murine Mst1 deficiency and other defects of leucocyte trafficking, this is likely to contribute to immunodeficiency by impairing key aspects of T-cell development and function such as positive selection in the thymus, thymic egress and immune synapse formation in the periphery.This is thepublished version. It first appeared at http://link.springer.com/article/10.1007%2Fs10875-016-0232-2

Treosulfan, Fludarabine Conditioning for HSCT in Children with Primary Immunodeficiency: UK Experience

We previously published results of 70 children who received treosulfan with cyclophosphamide (30) or fludarabine (40) before haematopoietic stem cell transplantation (HSCT) for Primary Immunodeficiency (PID). Toxicity was lower and T cell chimerism better in those receiving fludarabine, but numbers were relatively small and follow-up short. We now report outcome of 160 children who received homogeneous conditioning with treosulfan, fludarabine mostly with alemtuzumab (n=124). Median age at transplant was 1.36 years (0.09-18.25). Donors were: matched unrelated, 73; 1-3 antigen mismatched unrelated, 54; matched sibling, 12; other matched family, 17; haploidentical, 4. Stem cell source was: peripheral blood stem cells (PBSCs), 70; Bone marrow, 49; Cord Blood, 41. Median follow up was 4.3 years (0.8-9.4). Overall survival was 83%. There was no veno- occlusive disease. Seventy-four (46%) had acute GVHD, but only 14(9%) greater than grade II. Four patients were successfully retransplanted for graft loss or poor immune reconstitution. One further patient who rejected the graft, died. There was no association between T cell chimerism > 95% and stem cell source, but a significant association with myeloid chimerism > 95% and use of PBSC without an increased risk of significant GVHD compared to other sources. All 11 patients with severe combined immunodeficiency diagnosed at birth are alive with up to 8.7 years follow up. Long-term studies are required to determine late gonadotoxic effects and pharmacokinetic studies are needed to identify whether specific targeting is advantageous. The combination of treosulfan, fludarabine and alemtuzumab gives excellent results in HSCT for PID