Selective engraftment of donor CD4+25high FOXP3-positive T cells in IPEX syndrome after nonmyeloablative hematopoietic stem cell transplantation

Abstract

Mutations of FoxP3 result in the disturbance of FoxP3 expression and lack of functional CD4 ϩ CD25 high regulatory T cells in humans, causing immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. The only curative approach for IPEX syndrome, which is fatal within the first year of life in many cases, is allogeneic hematopoietic stem cell transplantation (HSCT). We monitored lineage-specific chimerism in a FoxP3-deficient patient after nonmyeloablative HSCT and graft rejection over 6 years. The patient lost donor chimerism in T cells, B cells, NK cells, monocytes, and granulocytes 1 year after transplantation, but remained clinically healthy without immunosuppression. To elucidate the immunologic basis of his continuing remission, we performed detailed lymphocyte subset analyses and detected FoxP3-expressing CD4 ϩ CD25 high T cells, comprising 1% to 2% of the CD4 ϩ T cells (ϳ 10/ L), which were more than 90% donor-derived. The patient is disease-free and shows no signs of autoimmunity, suggesting that stable, selective engraftment of regulatory T cells is possible and associated with cure from IPEX syndrome.HSCT may be a curative approach for IPEX syndrome. 1-3 However, the required levels of donor chimerism and conditioning intensity are unknown. Myeloablative conditioning is associated with substantial transplantation-related mortality, 2-5 whereas nonmyeloablative conditioning carries an increased risk of rejection because of dysregulated effector T-cell function. 6 Here we report a boy with IPEX syndrome who underwent peripheral blood HSCT at the age of 11 months from an unrelated 10/10-matched donor (2 ϫ 10 7 /kg CD34 ϩ , 10 9 /kg CD3 ϩ cells) after nonmyeloablative conditioning according to the local protocol (fludarabine 6 ϫ 30 mg/m 2 ; melphalan 140 mg/ m 2 ; alemtuzumab 5 ϫ 0.2 mg/kg). The post-HSCT course was uncomplicated with complete engraftment on day ϩ12. All IPEX-linked symptoms resolved until day ϩ30. Acute graftversus-host disease (skin, II°) was treated with steroids until day ϩ56; cyclosporin A was tapered 1 year after transplantation. At this time, in vitro responses to vaccine antigens and phytohemagglutinin were normal. Six years posttransplantation the patient remains insulin-dependent due to irreversible islet cell damage but has no active autoimmunity. The clinically healthy boy shows no increased frequency or severity of infections (Table S1; available on the Blood website; see the Supplemental Materials link at the top of the online article). Chimerism was determined in peripheral blood cell subsets regularly (described elsewhere 6 ). Approval was obtained from the St Anna Children's Hospital (Vienna, Austria) Institutional Review Board for these studies. Informed consent was obtained in accordance with the Declaration of Helsinki.After 100% donor cell engraftment, there was a continuous decline throughout the first year to an overall and subset-specific donor chimerism of 5% to 10% (Ϯ 6%; Figure 1A) without any clinical symptoms of relapse. Five-, 5.5-, and ...

Wild-type FOXP3 is selectively active in CD4+CD25hi regulatory T cells of healthy female carriers of different FOXP3 mutations

“…17 Furthermore, the observation that nTregs are present in PBMCs of IPEX patients 10 demonstrates that mut-FOXP3 does not prevent the emergence of nTregs from the thymus, indirectly reinforcing the hypothesis of a peripheral selection of WT-FOXP3 nTregs in carriers. Interestingly, long-term survival of donor-derived nTregs, despite the loss of donor peripheral chimerism in other cell populations, has been demonstrated in an IPEX patient who successfully underwent bone marrow transplantation, 18 further supporting the evidence that nTregs expressing the WT-FOXP3 allele have a selective advantage.…”

Single centre experience of haematopoietic SCT for patients with immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome

“…Overall, 100% donor T-cell chimerism was achieved in two out of five patients, and three have mixed donor chimerism. It has been reported that mixed chimerism, with only donor Treg population, is sufficient to suppress the autoimmune process and resolve enteropathy, 6,8 although it may take a long time because of previous severe gut damage. The patients' complex management was achieved by rigorous multi-disciplinary teamwork emphasizing the importance of managing this group of children in specialized centres.…”

Forkhead box P3:The Peacekeeper of the Immune System

“…Therefore, while the functional impairment of FOXP3-mutated Treg cells is undisputed, the identification of circulating cells with figure. specific demethylation of the Treg-cell-Specific-Demethylated-Region (TSDR) (see below), demonstrated that wild type FOXP3 is dispensable for thymic development of Treg cell precursors in humans [44,55]. The lack of functional FOXP3 impairs Treg peripheral maintenance, as demonstrated by the observation that in healthy female carriers of FOXP3 mutations [102] and in transplanted IPEX patients with low peripheral donor chimerism [48] only Treg cells expressing a wild type FOXP3 are detectable in peripheral blood.…”

“…On the other hand, a non-myeloablative conditioning may increase the risk of a partial chimerism, although we now know that full donor engraftment is not necessary for complete recovery, but rather the engraftment of donor Treg cells is essential to cure the disease [48]. Based on the latter observation, cell/gene therapy approaches designed to selectively restore the Treg cell compartment are currently under investigation by the group of R. Bacchetta at the San Raffaele Scientific Institute of Milan, Italy, as an alternative therapeutic strategy when a suitable donor for HSCT is not available (Passerini et al, manuscript in preparation).…”