Zeynep Yesim Kucuk

Clinical spectrum and features of activated phosphoinositide 3-kinase δ syndrome: A large patient cohort study

Background: Activated phosphoinositide 3‐kinase &dgr; syndrome (APDS) is a recently described combined immunodeficiency resulting from gain‐of‐function mutations in PIK3CD, the gene encoding the catalytic subunit of phosphoinositide 3‐kinase &dgr; (PI3K&dgr;). Objective: We sought to review the clinical, immunologic, histopathologic, and radiologic features of APDS in a large genetically defined international cohort. Methods: We applied a clinical questionnaire and performed review of medical notes, radiology, histopathology, and laboratory investigations of 53 patients with APDS. Results: Recurrent sinopulmonary infections (98%) and nonneoplastic lymphoproliferation (75%) were common, often from childhood. Other significant complications included herpesvirus infections (49%), autoinflammatory disease (34%), and lymphoma (13%). Unexpectedly, neurodevelopmental delay occurred in 19% of the cohort, suggesting a role for PI3K&dgr; in the central nervous system; consistent with this, PI3K&dgr; is broadly expressed in the developing murine central nervous system. Thoracic imaging revealed high rates of mosaic attenuation (90%) and bronchiectasis (60%). Increased IgM levels (78%), IgG deficiency (43%), and CD4 lymphopenia (84%) were significant immunologic features. No immunologic marker reliably predicted clinical severity, which ranged from asymptomatic to death in early childhood. The majority of patients received immunoglobulin replacement and antibiotic prophylaxis, and 5 patients underwent hematopoietic stem cell transplantation. Five patients died from complications of APDS. Conclusion: APDS is a combined immunodeficiency with multiple clinical manifestations, many with incomplete penetrance and others with variable expressivity. The severity of complications in some patients supports consideration of hematopoietic stem cell transplantation for severe childhood disease. Clinical trials of selective PI3K&dgr; inhibitors offer new prospects for APDS treatment.

Rapid desensitization of mice with anti-FcγRIIb/FcγRIII mAb safely prevents IgG-mediated anaphylaxis

BACKGROUND Stimulatory IgG receptors (FcγRs) on bone marrow-derived cells contribute to the pathogenesis of several autoimmune and inflammatory disorders. Monoclonal antibodies that block FcγRs might suppress these diseases, but they can induce anaphylaxis. OBJECTIVE We wanted to determine whether a rapid desensitization approach can safely suppress IgG/FcγR-mediated anaphylaxis. METHODS Mice were injected with serially increasing doses of 2.4G2, a rat mAb that blocks the inhibitory FcγR, FcγRIIb, and the stimulatory receptor, FcγRIII. Rectal temperature was used to detect the development of anaphylaxis. Passive and active IgG-mediated anaphylaxis were evaluated in mice that had been rapidly desensitized with 2.4G2 or mock-desensitized in mice in which monocyte/macrophages, basophils, or neutrophils had been depleted or desensitized and in mice in which FcγRI, FcγRIII, and/or FcγRIV had been deleted or blocked. RESULTS Rapid desensitization with 2.4G2 prevented 2.4G2-induced shock and completely suppressed IgG-mediated anaphylaxis. Rapid desensitization of ovalbumin-sensitized mice with 2.4G2 was safer and more effective than rapid desensitization with ovalbumin. 2.4G2 treatment completely blocked FcγRIII and removed most FcγRI and FcγRIV from nucleated peripheral blood cells. Because IgG(2a)-mediated anaphylaxis was partially FcγRI and FcγRIV dependent, the effects of 2.4G2 on FcγRI and FcγRIV were probably crucial for its complete inhibition of IgG(2a)-mediated anaphylaxis. IgG(2a)-mediated anaphylaxis was partially inhibited by depletion or desensitization of monocyte/macrophages, basophils, or neutrophils. CONCLUSION IgG-mediated anaphylaxis can be induced by ligation of FcγRI, FcγRIII, or FcγRIV on monocycte/macrophages, basophils, or neutrophils and can be safely suppressed by rapid desensitization with anti-FcγRII/RIII mAb. A similar approach may safely suppress other FcγR-dependent immunopathology.

Rapid polyclonal desensitization with antibodies to IgE and FcεRIα.

BACKGROUND Rapid desensitization, a procedure in which persons allergic to an antigen are treated at short intervals with increasing doses of that antigen until they tolerate a large dose, is an effective, but risky, way to induce temporary tolerance. OBJECTIVE We wanted to determine whether this approach can be adapted to suppress all IgE-mediated allergies in mice by injecting serially increasing doses of monoclonal antibodies (mAbs) to IgE or FcεRIα. METHODS Active and passive models of antigen- and anti-IgE mAb-induced IgE-mediated anaphylaxis were used. Mice were desensitized with serially increasing doses of anti-IgE mAb, anti-FcεRIα mAb, or antigen. Development of shock (hypothermia), histamine and mast cell protease release, cytokine secretion, calcium flux, and changes in cell number and FcεRI and IgE expression were evaluated. RESULTS Rapid desensitization with anti-IgE mAb suppressed IgE-mediated immediate hypersensitivity; however, some mice developed mild anaphylaxis during desensitization. Rapid desensitization with anti-FcεRIα mAb that only binds FcεRI that is not occupied by IgE suppressed both active and passive IgE-mediated anaphylaxis without inducing disease. It quickly, but temporarily, suppressed IgE-mediated anaphylaxis by decreasing mast cell signaling through FcεRI, then slowly induced longer lasting mast cell unresponsiveness by removing membrane FcεRI. Rapid desensitization with anti-FcεRIα mAb was safer and longer lasting than rapid desensitization with antigen. CONCLUSION A rapid desensitization approach with anti-FcεRIα mAb safely desensitizes mice to IgE-mediated anaphylaxis by inducing mast cell anergy and later removing all mast cell IgE. Rapid desensitization with an anti-human FcεRIα mAb may be able to prevent human IgE-mediated anaphylaxis.

Induction and suppression of allergic diarrhea and systemic anaphylaxis in a murine model of food allergy.

BACKGROUND The clinical manifestations of food allergy include diarrhea and systemic anaphylaxis (shock), which can occur together or by themselves in different subjects. Although ingested food antigens need to be absorbed to induce shock, it is not known whether they need to be absorbed to induce diarrhea. OBJECTIVE We sought to identify mechanisms that determine whether food allergy induces diarrhea versus shock and determine whether diarrhea requires absorption of ingested antigens. METHODS These issues were studied in mice in active, passive, and hybrid immunization models. The active model was used to determine the allergic diarrhea susceptibility of J chain- and polymeric immunoglobulin receptor-deficient mice, which are unable to secrete IgA. The hybrid model was used to determine whether intravenously administered antigen-specific IgG antibody, which is not secreted into the gut, can protect against allergic diarrhea, as well as shock. RESULTS Shock, but not diarrhea, was induced in naive mice by using intravenous IgE anti-trinitrophenyl (TNP) antibody, followed by oral TNP-BSA, whereas both were induced in mice presensitized with intraperitoneal ovalbumin/alum plus oral ovalbumin. More TNP-BSA was required to induce shock than diarrhea in presensitized mice, and intravenous IgG anti-TNP antibody, which is not secreted into the gut, protected these mice against both diarrhea and shock. Consistent with this, chicken ovalbumin-immunized J chain- and polymeric immunoglobulin receptor-deficient mice, which have high serum IgA levels but little intestinal IgA, resisted diarrhea induction. CONCLUSION Intestinal immunity and oral antigen dose determine whether diarrhea, systemic anaphylaxis, or both are induced, and ingested antigen must be absorbed to induce either response.

Outcome of hematopoietic cell transplantation for DNA double-strand break repair disorders

Background: Rare DNA breakage repair disorders predispose to infection and lymphoreticular malignancies. Hematopoietic cell transplantation (HCT) is curative, but coadministered chemotherapy or radiotherapy is damaging because of systemic radiosensitivity. We collected HCT outcome data for Nijmegen breakage syndrome, DNA ligase IV deficiency, Cernunnos–XRCC4‐like factor (Cernunnos‐XLF) deficiency, and ataxia‐telangiectasia (AT). Methods: Data from 38 centers worldwide, including indication, donor, conditioning regimen, graft‐versus‐host disease, and outcome, were analyzed. Conditioning was classified as myeloablative conditioning (MAC) if it contained radiotherapy or alkylators and reduced‐intensity conditioning (RIC) if no alkylators and/or 150 mg/m2 fludarabine or less and 40 mg/kg cyclophosphamide or less were used. Results: Fifty‐five new, 14 updated, and 18 previously published patients were analyzed. Median age at HCT was 48 months (range, 1.5‐552 months). Twenty‐nine patients underwent transplantation for infection, 21 had malignancy, 13 had bone marrow failure, 13 received pre‐emptive transplantation, 5 had multiple indications, and 6 had no information. Twenty‐two received MAC, 59 received RIC, and 4 were infused; information was unavailable for 2 patients. Seventy‐three of 77 patients with DNA ligase IV deficiency, Cernunnos‐XLF deficiency, or Nijmegen breakage syndrome received conditioning. Survival was 53 (69%) of 77 and was worse for those receiving MAC than for those receiving RIC (P = .006). Most deaths occurred early after transplantation, suggesting poor tolerance of conditioning. Survival in patients with AT was 25%. Forty‐one (49%) of 83 patients experienced acute GvHD, which was less frequent in those receiving RIC compared with those receiving MAC (26/56 [46%] vs 12/21 [57%], P = .45). Median follow‐up was 35 months (range, 2‐168 months). No secondary malignancies were reported during 15 years of follow‐up. Growth and developmental delay remained after HCT; immune‐mediated complications resolved. Conclusion: RIC HCT resolves DNA repair disorder–associated immunodeficiency. Long‐term follow‐up is required for secondary malignancy surveillance. Routine HCT for AT is not recommended.

Hematopoietic stem cell transplantation in 29 patients hemizygous for hypomorphic IKBKG/NEMO mutations

X-linked recessive ectodermal dysplasia with immunodeficiency is a rare primary immunodeficiency caused by hypomorphic mutations of the IKBKG gene encoding the nuclear factor κB essential modulator (NEMO) protein. This condition displays enormous allelic, immunological, and clinical heterogeneity, and therapeutic decisions are difficult because NEMO operates in both hematopoietic and nonhematopoietic cells. Hematopoietic stem cell transplantation (HSCT) is potentially life-saving, but the small number of case reports available suggests it has been reserved for only the most severe cases. Here, we report the health status before HSCT, transplantation outcome, and clinical follow-up for a series of 29 patients from unrelated kindreds from 11 countries. Between them, these patients carry 23 different hypomorphic IKBKG mutations. HSCT was performed from HLA-identical related donors (n = 7), HLA-matched unrelated donors (n = 12), HLA-mismatched unrelated donors (n = 8), and HLA-haploidentical related donors (n = 2). Engraftment was documented in 24 patients, and graft-versus-host disease in 13 patients. Up to 7 patients died 0.2 to 12 months after HSCT. The global survival rate after HSCT among NEMO-deficient children was 74% at a median follow-up after HSCT of 57 months (range, 4-108 months). Preexisting mycobacterial infection and colitis were associated with poor HSCT outcome. The underlying mutation does not appear to have any influence, as patients with the same mutation had different outcomes. Transplantation did not appear to cure colitis, possibly as a result of cell-intrinsic disorders of the epithelial barrier. Overall, HSCT can cure most clinical features of patients with a variety of IKBKG mutations.

CTP Synthase 1 Deficiency in Successfully Transplanted Siblings with Combined Immune Deficiency and Chronic Active EBV Infection

To the editor: Cytidine 5’ triphosphate (CTP) is an important precursor for DNA, RNA, phospholipid synthesis, and protein sialylation, needed for cell proliferation and function. CTP is produced either via de novo synthesis or a salvage pathway, both of which depend on CTP synthases (CTPS). The mammalian CTPS isozymes, CTPS1 and CTPS2, share 74 % amino acid identity [1]. Although their respective roles are not fully understood, CTPS have a unique ability to bind to four nucleotides (ATP, UTP, GTP, and CTP) and sense intracellular concentrations of these nucleotides and glutamine. Control of CTP synthesis appears to be strictly regulated, as suggested by the fact that the cellular concentration of CTP is the lowest [2]. Human lymphocytes dramatically increase CTP levels following mitogenic stimulation, indicating that CTP synthase activity is an important step for DNA synthesis in lymphocytes [3]. This important role of CTPS was recently highlighted, showing homozygous loss-of-function mutations in CTPS1 in patients of British ancestry [4]. The original study included eight patients from six unrelated families from Northern England, with a shared clinical phenotype of combined immune deficiency (CID) characterized by recurrent infections, due to Epstein-Barr virus (EBV) and Varicella Zoster virus (VZV), and encapsulated bacterial infections. The authors reported defective T cell proliferation in response to activation by antigens, anti-CD3 or anti-CD3/CD28, with weak or no impact on TCR-mediated cytokine production, and CD8 degranulation, respectively. Six of eight patients were reported to have undergone hematopoietic stem cell transplantation (SCT); however, their transplant and posttransplant courses were not discussed. No similar cases have been published since the original description. Here, we report two sisters with homozygous CTPS1 mutations, identified by exome sequencing. Similar to the previously published cases [4], these siblings, born to a nonconsanguineous family, whose ancestors emigrated from Northern England, suffered from recurrent sino-pulmonary and viral infections, due to VZV and EBV. Both have undergone SCT for chronic active EBV infection and CID and currently are in excellent health, 10 and 11 years post-transplant. Both patients’ immunological and SCT data are summarized in Table 1. The index patient, patient 1 (Pt1) presented at the age of 3 with a history of recurrent sino-pulmonary infections and recalcitrant varicella. At the age of 18 months, she developed vesicular lesions on her legs, following administration of the varicella vaccine. One month later, she developed generalized varicella, with VZV isolated from a typical lesion and from blood. Although this acute episode improved with acyclovir, as the months ensued, she suffered from recalcitrant vesicular eruptions, including one episode with corneal involvement and presumed varicella hepatitis. At 2 years of age, Pt1 developed left-sided paralysis with CT/MRI/MRA findings consistent with a stroke, from which she recovered completely. At that time, EBV serology demonstrated primary acute infection. No spinal fluid or blood viral PCR studies were performed. At 3 years of age, due to recurrent pneumonia, bronchoscopy was performed, which yielded Bordetella bronchiseptica. There was no evidence of bronchiectasis on high-resolution chest CT (HRCT). Laboratory assessment, prior to referral, * Zeynep Yesim Kucuk zeynep.kucuk@cchmc.org

Long-term follow-up of IPEX syndrome patients after different therapeutic strategies: An international multicenter retrospective study

Background: Immunodysregulation polyendocrinopathy enteropathy x‐linked (IPEX) syndrome is a monogenic autoimmune disease caused by FOXP3 mutations. Because it is a rare disease, the natural history and response to treatments, including allogeneic hematopoietic stem cell transplantation (HSCT) and immunosuppression (IS), have not been thoroughly examined. Objective: This analysis sought to evaluate disease onset, progression, and long‐term outcome of the 2 main treatments in long‐term IPEX survivors. Methods: Clinical histories of 96 patients with a genetically proven IPEX syndrome were collected from 38 institutions worldwide and retrospectively analyzed. To investigate possible factors suitable to predict the outcome, an organ involvement (OI) scoring system was developed. Results: We confirm neonatal onset with enteropathy, type 1 diabetes, and eczema. In addition, we found less common manifestations in delayed onset patients or during disease evolution. There is no correlation between the site of mutation and the disease course or outcome, and the same genotype can present with variable phenotypes. HSCT patients (n = 58) had a median follow‐up of 2.7 years (range, 1 week‐15 years). Patients receiving chronic IS (n = 34) had a median follow‐up of 4 years (range, 2 months‐25 years). The overall survival after HSCT was 73.2% (95% CI, 59.4–83.0) and after IS was 65.1% (95% CI, 62.8–95.8). The pretreatment OI score was the only significant predictor of overall survival after transplant (P = .035) but not under IS. Conclusions: Patients receiving chronic IS were hampered by disease recurrence or complications, impacting long‐term disease‐free survival. When performed in patients with a low OI score, HSCT resulted in disease resolution with better quality of life, independent of age, donor source, or conditioning regimen.

Gimap5-dependent inactivation of GSK3β is required for CD4 + T cell homeostasis and prevention of immune pathology

GTPase of immunity-associated protein 5 (Gimap5) is linked with lymphocyte survival, autoimmunity, and colitis, but its mechanisms of action are unclear. Here, we show that Gimap5 is essential for the inactivation of glycogen synthase kinase-3β (GSK3β) following T cell activation. In the absence of Gimap5, constitutive GSK3β activity constrains c-Myc induction and NFATc1 nuclear import, thereby limiting productive CD4+ T cell proliferation. Additionally, Gimap5 facilitates Ser389 phosphorylation and nuclear translocation of GSK3β, thereby limiting DNA damage in CD4+ T cells. Importantly, pharmacological inhibition and genetic targeting of GSK3β can override Gimap5 deficiency in CD4+ T cells and ameliorates immunopathology in mice. Finally, we show that a human patient with a GIMAP5 loss-of-function mutation has lymphopenia and impaired T cell proliferation in vitro that can be rescued with GSK3 inhibitors. Given that the expression of Gimap5 is lymphocyte-restricted, we propose that its control of GSK3β is an important checkpoint in lymphocyte proliferation.Loss of function GIMAP5 mutation is associated with lymphopenia, but how it mediates T cell homeostasis is unclear. Here the authors study Gimap5−/− mice and a patient with GIMAP5 deficiency to show how this GTPAse negatively regulates GSK3β activity to prevent DNA damage and cell death.

Persistent Enteropathy in a Toddler with a Novel FOXP3 Mutation and Normal FOXP3 Protein Expression

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is caused by mutations in the FOXP3 gene. Patients usually present with a clinical triad of intractable diarrhea, diabetes, and eczema. In this patient, FOXP3 protein expression was normal, but FOXP3 Sanger sequencing confirmed the clinical suspicion of IPEX by detecting a previously unreported missense variant. Early recognition of IPEX is important, because hematopoietic stem cell transplantation can be curative.