Low-dose cyclosporine A in a patient with X-linked immune dysregulation, polyendocrinopathy and enteropathy

The transcription factor FoxP3 can fold into two dimerization states with divergent implications for regulatory T cell function and immune homeostasis

FoxP3 is an essential transcription factor (TF) for immunologic homeostasis, but how it utilizes the common forkhead DNA-binding domain (DBD) to perform its unique function remains poorly understood. We here demonstrated that unlike other known forkhead TFs, FoxP3 formed a head-to-head dimer using a unique linker (Runx1-binding region [RBR]) preceding the forkhead domain. Head-to-head dimerization conferred distinct DNA-binding specificity and created a docking site for the cofactor Runx1. RBR was also important for proper folding of the forkhead domain, as truncation of RBR induced domain-swap dimerization of forkhead, which was previously considered the physiological form of FoxP3. Rather, swap-dimerization impaired FoxP3 function, as demonstrated with the disease-causing mutation R337Q, whereas a swap-suppressive mutation largely rescued R337Q-mediated functional impairment. Altogether, our findings suggest that FoxP3 can fold into two distinct dimerization states: head-to-head dimerization representing functional specialization of an ancient DBD and swap dimerization associated with impaired functions.

The diagnostic approach to monogenic very early onset inflammatory bowel disease

Patients with a diverse spectrum of rare genetic disorders can present with inflammatory bowel disease (monogenic IBD). Patients with these disorders often develop symptoms during infancy or early childhood, along with endoscopic or histological features of Crohn's disease, ulcerative colitis, or IBD unclassified. Defects in interleukin-10 signaling have a Mendelian inheritance pattern with complete penetrance of intestinal inflammation. Several genetic defects that disturb intestinal epithelial barrier function or affect innate and adaptive immune function have incomplete penetrance of the IBD-like phenotype. Several of these monogenic conditions do not respond to conventional therapy and are associated with high morbidity and mortality. Due to the broad spectrum of these extremely rare diseases, a correct diagnosis is frequently a challenge and often delayed. In many cases, these diseases cannot be categorized based on standard histological and immunologic features of IBD. Genetic analysis is required to identify the cause of the disorder and offer the patient appropriate treatment options, which include medical therapy, surgery, or allogeneic hematopoietic stem cell transplantation. In addition, diagnosis based on genetic analysis can lead to genetic counseling for family members of patients. We describe key intestinal, extraintestinal, and laboratory features of 50 genetic variants associated with IBD-like intestinal inflammation. In addition, we provide approaches for identifying patients likely to have these disorders. We also discuss classic approaches to identify these variants in patients, starting with phenotypic and functional assessments that lead to analysis of candidate genes. As a complementary approach, we discuss parallel genetic screening using next-generation sequencing followed by functional confirmation of genetic defects.

Selective expansion of donor-derived regulatory T cells after allogeneic bone marrow transplantation in a patient with IPEX syndrome

IPEX syndrome is a rare and fatal disorder caused by absence of regulatory T cells (Tregs) due to congenital mutations in the Forkhead box protein 3 gene. Here, we report a patient with IPEX syndrome treated with RIC followed by allogeneic BMT from an HLA-matched sibling donor. We could achieve engraftment and regimen-related toxicity was well tolerated. Although the patient was in mixed chimera and the ratio of donor cells in whole peripheral blood remained relatively low, selective and sustained expansion of Tregs determined as CD4+CD25+Foxp3+ cells was observed. Improvement in clinical symptoms was correlated with expansion of donor-derived Tregs and disappearance of anti-villin autoantibody, which was involved in the pathogenesis of gastrointestinal symptoms in IPEX syndrome. This clinical observation suggests that donor-derived Tregs have selective growth advantage in patients with IPEX syndrome even in mixed chimera after allogeneic BMT and contribute to the control of clinical symptoms caused by the defect of Tregs.

FOXP3: genetic and epigenetic implications for autoimmunity

FOXP3 plays an essential role in the maintenance of self-tolerance and, thus, in preventing autoimmune diseases. Inactivating mutations of FOXP3 cause immunodysregulation, polyendocrinopathy, and enteropathy, X-linked syndrome. FOXP3-expressing regulatory T cells attenuate autoimmunity as well as immunity against cancer and infection. More recent studies demonstrated that FOXP3 is an epithelial cell-intrinsic tumor suppressor for breast, prostate, ovary and other cancers. Corresponding to its broad function, FOXP3 regulates a broad spectrum of target genes. While it is now well established that FOXP3 binds to and regulates thousands of target genes in mouse and human genomes, the fundamental mechanisms of its broad impact on gene expression remain to be established. FOXP3 is known to both activate and repress target genes by epigenetically regulating histone modifications of target promoters. In this review, we first focus on germline mutations found in the FOXP3 gene among IPEX patients, then outline possible molecular mechanisms by which FOXP3 epigenetically regulates its targets. Finally, we discuss clinical implications of the function of FOXP3 as an epigenetic modifier. Accumulating results reveal an intriguing functional convergence between FOXP3 and inhibitors of histone deacetylases. The essential epigenetic function of FOXP3 provides a foundation for experimental therapies against autoimmune diseases.

Immune dysregulation, polyendocrinopathy, enteropathy, x-linked syndrome: a paradigm of immunodeficiency with autoimmunity

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare monogenic primary immunodeficiency (PID) due to mutations of FOXP3, a key transcription factor for naturally occurring (n) regulatory T (Treg) cells. The dysfunction of Treg cells is the main pathogenic event leading to the multi-organ autoimmunity that characterizes IPEX syndrome, a paradigm of genetically determined PID with autoimmunity. IPEX has a severe early onset and can become rapidly fatal within the first year of life regardless of the type and site of the mutation. The initial presenting symptoms are severe enteritis and/or type-1 diabetes mellitus, alone or in combination with eczema and elevated serum IgE. Other autoimmune symptoms, such as hypothyroidism, cytopenia, hepatitis, nephropathy, arthritis, and alopecia can develop in patients who survive the initial acute phase. The current therapeutic options for IPEX patients are limited. Supportive and replacement therapies combined with pharmacological immunosuppression are required to control symptoms at onset. However, these procedures can allow only a reduction of the clinical manifestations without a permanent control of the disease. The only known effective cure for IPEX syndrome is hematopoietic stem cell transplantation, but it is always limited by the availability of a suitable donor and the lack of specific guidelines for bone marrow transplant in the context of this disease. This review aims to summarize the clinical histories and genomic mutations of the IPEX patients described in the literature to date. We will focus on the clinical and immunological features that allow differential diagnosis of IPEX syndrome and distinguish it from other PID with autoimmunity. The efficacy of the current therapies will be reviewed, and possible innovative approaches, based on the latest highlights of the pathogenesis to treat this severe primary autoimmune disease of childhood, will be discussed.

IPEX syndrome: Case report

INTRODUCTION IPEX syndrome, namely, a hereditary (X-linked) immunodysregulation with autoimmune polyendocrinopathy and enteropathy, as the basic manifestations, presents a rare and exceptionally severe disease. It develops due to gene mutation responsible for the synthesis of a specific protein (FOXP3), which, by differentiation and activation of regular T-lymphocytic CD4+CD25+, has the key role in the induction and maintenance of the peripheral tolerance of one's own tissue. CASE OUTLINE We present a male infant with classic clinical features of IPEX syndrome, which manifested by the end of the first month after birth, first with type 1 diabetes mellitus and chronic diarrhoea followed by dehydration and disordered development, and then with facial eczema and laboratory signs of thyroiditis without thyroid dysfunction (antithyreoglobulin antibodies 1:5500, antimicrosomal antibodies 1:40). In addition, plasma IgE level was high (517 IU/l), while antibodies to tissue transglutaminase were mildly increased (IgA 7.5 U/ml), and anti-smooth muscle and anti-DNA antibodies were absent. Based on the typical clinical features, as well as the laboratory findings, IPEX syndrome was diagnosed, which was further confirmed by proved IVS7+5G>A mutations in the FOXP3 gene. Therapy with insulin and Pronison, combined with parenteral and semielementary nutrition resulted in the patient's clinical improvement. At the age of 9 months, despite Pronison and hypoallergenic nutrition, the child had a relapse of severe and persistent diarrhoeal disorder followed by dehydration, weight loss and deterioration of general condition. Beside the complete parenteral nutrition, as well as other measures, azathioprine was introduced into the treatment, but without the desired effect. At the age of 12.5 months, due to bacteraemia and disseminated intravascular coagulation as complications, the patient ended lethally. CONCLUSION IPEX syndrome should be kept in mind in all the cases of associated type 1 diabetes mellitus and chronic diarrhoea in male neonates or infants. Although treatment results have still been modest, it is quite certain they will be far better in the near future.

Renal biopsy findings in children receiving long-term treatment with cyclosporine a given as a single daily dose

Long-term treatment of childhood nephrotic syndrome (NS) and rheumatic diseases with cyclosporine A (CsA) given as a single daily dose may yield better results and allow safer use of the drug than the conventional twice-daily dosing. However, the safety of such long-term treatment from the histological standpoint remains to be established. Posttreatment renal biopsy was conducted in a total of eight children (5 with minimal change NS, 2 with focal segmental glomerulosclerosis and 1 with X-linked immune dysregulation, polyendocrinopathy and enteropathy) receiving CsA as a single daily dose, after a mean treatment duration of 20 months (9-36 months). The initial daily dose of CsA (Neoral) was 2.0 mg/kg, given as a single daily dose before breakfast. The dose was subsequently adjusted to achieve a peak (between 1 and 2 hrs post-dosing, C1-C2) blood level of around 800 ng/ml. The mean daily CsA dose, mean C1-C2 blood level, and mean trough blood level in the subjects were 1.9 +/- 0.6 mg/kg, 803.8 +/- 117.2 ng/ml and 36.1 +/- 12.7 ng/ml, respectively. The result revealed no evidence of CsA-related nephrotoxicity, including arteriopathy, striped interstitial fibrosis or tubular atrophy, in any of the study participants. Also, no significant changes were observed in the mean estimated glomerular filtration rate as compared to the pretreatment values (127.6 +/- 14.9 ml/min/1.73 m(2) vs 115.6 +/- 22.8 ml/min/1.73 m(2), and except for mild hypertrichosis, no significant adverse effects of CsA were observed. These findings lend further support to the safety of long-term low-dose CsA treatment (median treatment duration in this study, 20 months), with the drug administered as a single daily dose while maintaining a peak (C1-C2) blood level of around 800 ng/ml.