Rescue of Murine IL-7 Receptor Deficiency with Human IL-7 Receptor Gene Therapy

In humans, interleukin 7 (IL-7) receptor (IL-7R) deficiency causes approximately 10% of cases of severe combined immunodeficiency (SCID). IL-7R deficient SCID is a T-B+NK+ SCID and is caused by autosomal recessive deficiency of the IL-7R alpha chain gene (IL7R). IL-7R is a heterodimeric receptor comprised of the alpha chain and the IL-2 receptor common gamma chain (IL2RG). In both mouse and human, IL-7R is a marker of the common lymphoid progenitor cell, and IL-7 signaling leads to STAT5 phosphorylation and proliferation of developing T and B cells. Mice lacking IL7R, Il7r -/-, lack both T and B cells (Peschon, JJ, et al. J Exp Med. 1994). T cells do not progress to TCR beta chain rearrangement and B cell development is halted at the pre-pro-B cell stage. Similar to the mouse, IL-7 signaling in humans is required for T cell receptor beta gene rearrangement and T cell maintenance, however humans lacking IL-7R can develop B cells. A prior attempt to rescue murine IL-7R deficiency utilized a retroviral vector (mouse stem cell virus, MSCV), the MSCV retroviral promoter, and the murine Il7r gene (Jiang, Q, et al. Gene Therapy. 2005). This strategy did restore T cells and had variable restoration of B cells. However, retroviral-based gene addition of Il7r led to a myeloproliferative condition with significant neutrophilia and splenomegaly. Transduced bone marrow cells formed myeloid progenitors in response to IL-7 in vitro. We evaluated a novel gene therapy for IL-7R deficient SCID that utilizes the human IL7R gene. To prevent lineage skewing, we sought to limit ectopic expression of IL7R in non-lymphoid cells by utilizing the endogenous enhancers and promoters of IL7R. These sequences were identified as sites of high sequence conservation across species and DNA accessibility/hypersensitivity (DHS) in human lymphocytes. We are testing these sequences alone or in combination with the constitutive phosphoglycerate kinase promoter (PGK) in VSV-G pseudotyped lentiviral vectors (LV): vPGK_DHS_hIL7R and vDHS_hIL7R. Here we present the first data evaluating the ability of the human IL-7R protein to functionally replace the murine IL-7R protein and the ability of IL7R gene addition to rescue the murine Il7r -/- immunodeficient phenotype in vivo. Transduction of Il7r -/- bone marrow cells with IL7R encoding LV rescued the formation of lymphocyte precursors from murine bone marrow cells in colony forming unit (CFU) assays (pre-B CFU with human IL-7), with the most robust response seen with vPGK_DHS_hIL7R. Mouse bone marrow from Il7r -/- animals transduced ex vivo engrafted in lethally irradiated (8 Gy) Il7r -/-oppositegender recipients and there were no significant aberrations in absolute neutrophil count, hemoglobin or platelet count. Absolute lymphocyte counts in mice receiving transduced Il7r -/-bone marrow cells was higher (mean 2555/μL) than in mice receiving untransduced bone marrow (mean 1410/μL). The proportion of leukocytes that were T cells was 4.2-fold and 9.8-fold higher at 1 and 2 months post-transplant, respectively. B cells were only seen in mice receiving vPGK_DHS_hIL7R: 7.4% of leukocytes versus 1.5% in controls. A reciprocal decrease in the fraction of Gr1+ cells (neutrophils and monocytes) was seen at two months post-transplant in transduced marrow recipients compared to untransduced controls: 36.5% versus 63% Gr1+, respectively. Lymphocyte subsets are being further analyzed, bone marrow and thymic lymphoid precursors assessed, and T and B cell function in response to immunizations are in progress. Further evaluation in human derived IL7R deficient human cells is warranted. For individuals with IL-7R deficient SCID, but no HLA matched hematopoietic stem cell (HSC) donor, there is a difficult choice between the risks of GVHD with a mismatched HSC donor and supportive care with the hope of identifying a matched HSC donor in the future. In immunodeficiencies however age and serious infection are both associated with increased mortality (Pai, SY, et al. NJEM. 2014). This novel approach to IL7R gene replacement has the potential to be a therapeutic and expedient option for those without a matched donor. Additionally, this would be an ideal disorder for HSC conditioning with less toxic, HSC-targeted strategies given gene corrected lymphocytes and progenitors will preferentially expand post-transplant. Disclosures Rivella: Disc Medicine: Consultancy, Membership on an entity's Board of Directors or advisory committees; Keros Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Consultancy; Ionis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; MeiraGTx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forma Theraputics: Consultancy; Incyte: Consultancy.

Interleukin-7 Receptor Gene Heterozygous Mutations in Recipients Significantly Increase Acute Graft-Versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation

Acute graft-versus-host disease (aGVHD) is one of major complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Genetic polymorphisms of interleukin-7 receptor (IL-7R) have an impact on transplant-related mortality (Z Shamim et al. BMT 2006). Our previous studies indicated that hematological and immunological hereditary predisposition genes have potential influence on major complications of allo-HSCT in patients with hematological malignancies (unpublished data). In present study, the influence of hematological and immunological hereditary predisposition genes on aGVHD after allo-HSCT in the patients with hematological malignancies was investigated. Between February 2018 and August 2019, 92 patients with hematological malignancies who underwent allo-HSCT in Beijing Boren Hospital were enrolled. The median age was 17 (1 to 45) years old. The diagnoses included acute myeloid leukemia (37, 40.2%), acute lymphoblastic leukemia (36, 39.1%), non-Hodgkin's lymphoma (13, 14.1%), and myelodysplastic syndrome (6, 6.5%). The disease status before transplant was complete remission in 54 (58.7%), non-remission in 23 (25%), and relapse in 15 (16.3%). Before transplants, blood samples were collected from the patients, their parents and potential related donors to detect hematological and immunological hereditary predisposition genes with whole exon sequencing and validation by sanger sequencing. The donors were from identical siblings (4, 4.3%) or matched unrelated volunteers (8, 8.7%) or haploidentical family members (80, 86.9%). Myeloablative conditioning regimens with either total body irradiation/fludarabine-based or busulfan/fludarabine-based were applied. Anti-thymocyte globulin was used in haploidentical and unrelated transplants. GVHD prophylaxis was with cyclosporine, short-term methotrexate and mycophenolate mofetil. Methylprednisolong 1-2mg/kg daily was used for aGVHD treatment and basiliximab was administrated in severe aGVHD. Forty-eight patients (52.2%) developed aGVHD as aGVHD group and 44 patients (47.8%) have no aGVHD as non-aGVHD group. IL7R gene heterozygous mutations in recipients significantly increased overall aGVHD and also severe aGVHD after allo-HSCT. IL7R gene heterozygous mutations were found in 7/48 patients in aGVHD group, but 0/44 in non-GVHD group (P = 0.041). The incidence of grade III-IV aGVHD in patients with IL7R gene heterozygous mutations was significantly higher than that without IL7R gene heterozygous mutations. (5/7 vs. 7/41, P=0.007). Among the patients with IL7R gene heterozygous mutations in aGVHD group, 5/7 patients (71.4%) had grade III-IV aGVHD. Three of them with grade III aGVHD had the same heterozygous mutation site: c.c1241t; p.t414m and rest 2 patients with grade IV aGVHD had the same heterozygous mutation site: c.g314a; p. S105n. Our preliminary results have shown that IL7R gene heterozygous mutations in recipients have significantly increased the risk of overall aGVHD and severe aGVHD after allo-HSCT in the patients with hematological malignancies. Larger sample size is needed to address this issue. Disclosures No relevant conflicts of interest to declare.

Association of Multiple Sclerosis Phenotypes with Single Nucleotide Polymorphisms of IL7R, LAG3, and CD40 Genes in a Jordanian Population: A Genotype-Phenotype Study

It is thought that genetic variations play a vital role in the Multiple Sclerosis (MS) etiology. However, the role of genetic factors that influence the clinical features of MS remains unclear. We investigated the correlation between 21 single nucleotide polymorphisms within three genes (IL7R, LAG3, and CD40) and MS clinical characteristics in the Jordanian population. Blood samples and clinical phenotypic data were collected from 218 Arab Jordanian MS patients, vitamin D was measured, genomic DNA was extracted, and genotyping of the candidate genes’ polymorphisms were analyzed using the Sequenom MassARRAY® system. The association of these single nucleotide polymorphisms (SNPs) with MS was performed using a Chi-square, Fisher exact test, and one-way ANOVA. We found a significant association between vitamin D deficiency and three SNPs of the IL7R gene, namely rs987107 (P-value = 0.047), rs3194051 (P-value = 0.03), and rs1494571 (P-value = 0.036), in addition to two SNPs of CD40, namely rs1883832 and rs6074022 (P-value = 0.049 for both). rs3194051 of the IL7R gene (P-value = 0.003) and rs1922452 of the LAG3 gene (P-value = 0.028) were strongly associated with comorbidity. The number of relapses before drug onset was found to be correlated with IL7R SNPs rs969128 (P-value = 0.04) and rs1494555 (P-value = 0.027), whereas the expanded disability status scale (EDSS) was associated with rs1494555 polymorphism of IL7R gene (P-value = 0.026). Current findings indicate important correlations between certain SNPs and the risk of various phenotypes of multiple sclerosis in the Jordanian community. Therefore, this will not only contribute to the understanding of MS, but will also assist with the development of personalized treatment procedures.

The chromatin accessibility signature of human immune aging stems from CD8+ T cells

Aging is linked to deficiencies in immune responses and increased systemic inflammation. To unravel the regulatory programs behind these changes, we applied systems immunology approaches and profiled chromatin accessibility and the transcriptome in PBMCs and purified monocytes, B cells, and T cells. Analysis of samples from 77 young and elderly donors revealed a novel and robust aging signature in PBMCs, with simultaneous systematic chromatin closing at promoters and enhancers associated with T cell signaling and a potentially stochastic chromatin opening mostly found at quiescent and repressed sites. Combined analyses of chromatin accessibility and the transcriptome uncovered immune molecules activated/inactivated with aging and identified the silencing of the IL7R gene and the IL-7 signaling pathway genes as potential biomarkers. This signature is borne by memory CD8+ T cells, which exhibited an aging-related loss in binding of NF-κB and STAT factors. Thus, our study provides a unique and comprehensive approach to identifying candidate biomarkers and provides mechanistic insights into aging-associated immunodeficiency.