Cause Of Combined Immunodeficiency Research Articles

Reduced toxicity conditioning and a high CD34+ cell dose can achieve full donor chimerism in DOCK8 deficiency.

Biallelic mutations in the dedicator of cytokinesis 8 (DOCK8) gene were identified as the cause of combined immunodeficiency in 2009. Survival rates without hematopoietic stem cell transplant in patients with DOCK8 deficiency decline from 87% at 10 years to 33% at 30 years. Hematopoietic stem cell transplant is therefore the recommended treatment for cure of DOCK8 deficiency. However, patients with DOCK8 deficiency have multiple infectious comorbidities; hence, they cannot tolerate myeloablative conditioning. Reduced intensity conditioning reduces the risk of transplant-related mortality but increases the possibility of mixed chimerism. Mixed chimerism in children with immunodeficiency increases the risk of autoimmunity and the need for long-term immunoglobulin infusion. Here we have sought to devise a strategy for reducing the possibility of mixed chimerism without increasing the risk of transplant-related mortality. To balance the risk of transplant-related mortality and mixed chimerism, we used treosulfan-based reduced toxicity conditioning with a high CD34+ cell dose and differential T-cell capping for HLA-matched and haploidentical transplants. We are able to report that by using the aforementioned novel strategy, we achieved excellent transplant outcomes in the first cohort of high-risk patients with DOCK8 deficiency from India. High CD34+ cell dose and reduced toxicity conditioning can achieve full donor chimerism in DOCK8 deficiency.

Combined immunodeficiency and impaired PI3K signaling in a patient with biallelic LCP2 variants

Inborn errors affecting components of the T-cell receptor signaling cascade cause combined immunodeficiency with various degrees of severity. Recently, homozygous variants in LCP2 were reported to cause pediatric onset of severe combined immunodeficiency with neutrophil, platelet, and T-and B-cell defects. We sought to unravel the genetic cause of combined immunodeficiency and early-onset immune dysregulation in a 26-year-old man who presented with specific antibody deficiency, autoimmunity, and inflammatory bowel disease since early childhood. The patient was subjected to whole-exome sequencing of genomic DNA and examination of blood neutrophils, platelets, and T and B cells. Expression levels of the Src homology domain 2-containing leukocyte protein of 76 kDa (SLP76) and tonic and ligand-induced PI3K signaling were evaluated by flow-cytometric detection of phosphorylated ribosomal protein S6 in B and T cells. Compound heterozygous missense variants were identified in LCP2, affecting the proline-rich repeat domain of SLP76 (p.P190R and p.R204W). The patient's total B- and T-cell numbers were within the normal range, as was platelet function. However, neutrophil function, numbers of unswitched and class-switched memory B cells, and serum IgA were decreased. Moreover, intracellular SLP76 protein levels were reduced in the patient's B cells, CD4+ and CD8+ T cells, and natural killer cells. Tonic and ligand-induced levels of phosphorylated ribosomal protein S6 and ligand-induced phosphorylated PLCγ1 were decreased in the patient's B cells and CD4+ and CD8+ T cells. Biallelic variants in LCP2 impair neutrophil function and T-cell and B-cell antigen-receptor signaling and can cause combined immunodeficiency with early-onset immune dysregulation, even in the absence of platelet defects.

Muller morphs redefined by a multimorphic IRF4 variant presenting as CID with PCP susceptibility

In their last review, the IUIS reported 40 inborn errors of immunity (IEI) leading to combined immunodeficiency (CID). Yet, the genetic cause of CID in a sizeable percentage of patients remains unknown. We describe seven patients with CID from four continents with similar clinical presentations characterized by severe viral and recurrent respiratory infections, notably by Pneumocystis jirovecii. Two of the patients also suffered from mycobacterial disease. All these seven patients carry the heterozygous mutation T95R in the DNA binding domain of the interferon regulatory factor 4 (IRF4). Leveraging state-of-the-art transcriptomic, molecular, computational, and gene editing technologies, we discovered that IRF4-T95R does not fit into any single category of the Muller morphs but in three of them simultaneously. In fact, we showed that IRF4-T95R causes a unique combination of (i) gain-of-function by binding DNA with higher affinity than IRF4-WT; (ii) loss-of-function since IRF4-T95R fails to induce canonical IRF4 regulated genes, and; (iii) neomorphic functions by inducing the transcription of genes that IRF4-WT does not. These alterations in the transcriptional programming caused by the mutation lead to cellular and humoral immunological abnormalities. Patients’ B cells displayed impaired maturation, defective plasma cell differentiation, and isotype switching, all which resulted in agammaglobulinemia. Their T cells, despite proliferating normally, showed a decreased production of pro-inflammatory cytokines and a reduced capacity to differentiate into TH17 and TFH. Two different knock-in mouse models recapitulated the patients’ phenotypes. Overall, our data show that autosomal dominant IRF4-T95R is a new genetic cause of CID and defines a novel multimorphic molecular mechanism of a disease characterized by gain, loss, and new functions of IRF4.

The Broad Clinical Spectrum and Transplant Results of PNP Deficiency.

Purine nucleoside phosphorylase (PNP) is a known yet rare cause of combined immunodeficiency with a heterogeneous clinical presentation. We aim to add to the expanding clinical spectrum of disease, and to summarize the available data on bone marrow transplant for this condition. Data was collected from patient files retrospectively. A review of the literature of hematopoietic stem cell transplantation (HSCT) for PNP deficiency was conducted. Four patients were treated in two centers in Israel. One patient died of EBV-related lymphoma with CNS involvement prior to transplant. The other three patients underwent successful HSCT with good immune reconstitution post-transplant (follow-up 8-108 months) and excellent neurological outcomes. PNP is a variable immunodeficiency and should be considered in various clinical contexts, with or without neurological manifestations. HSCT offers a good treatment option, with excellent clinical outcomes, when preformed in a timely manner.

M292 NUTRITIONAL SUPPLEMENTATION IN PATIENTS WITH COMBINED IMMUNODEFICIENCY SECONDARY TO MTHFD1 DEFICIENCY

MTHFD1 gene mutations result in defects in folate metabolism and are rare causes of combined immunodeficiency. Optimal treatment for affected patients remains to be established.

Combined immunodeficiency and Epstein-Barr virus-induced B cell malignancy in humans with inherited CD70 deficiency.

In this study, we describe four patients from two unrelated families of different ethnicities with a primary immunodeficiency, predominantly manifesting as susceptibility to Epstein-Barr virus (EBV)-related diseases. Three patients presented with EBV-associated Hodgkin's lymphoma and hypogammaglobulinemia; one also had severe varicella infection. The fourth had viral encephalitis during infancy. Homozygous frameshift or in-frame deletions in CD70 in these patients abolished either CD70 surface expression or binding to its cognate receptor CD27. Blood lymphocyte numbers were normal, but the proportions of memory B cells and EBV-specific effector memory CD8+ T cells were reduced. Furthermore, although T cell proliferation was normal, in vitro-generated EBV-specific cytotoxic T cell activity was reduced because of CD70 deficiency. This reflected impaired activation by, rather than effects during killing of, EBV-transformed B cells. Notably, expression of 2B4 and NKG2D, receptors implicated in controlling EBV infection, on memory CD8+ T cells from CD70-deficient individuals was reduced, consistent with their impaired killing of EBV-infected cells. Thus, autosomal recessive CD70 deficiency is a novel cause of combined immunodeficiency and EBV-associated diseases, reminiscent of inherited CD27 deficiency. Overall, human CD70-CD27 interactions therefore play a nonredundant role in T and B cell-mediated immunity, especially for protection against EBV and humoral immunity.

SYK expression endows human ZAP70-deficient CD8 T cells with residual TCR signaling

Autosomal recessive human ZAP70 deficiency is a rare cause of combined immunodeficiency (CID) characterized by defective CD4 T cells and profound CD8 T cell lymphopenia. Herein, we report two novel patients that extend the molecular genetics, the clinical and functional phenotypes associated with the ZAP70 deficiency. The patients presented as infant-onset CID with severe infections caused by varicella zoster virus and live vaccines. Retrospective TCR excision circle newborn screening was normal in both patients. One patient carried a novel non-sense mutation (p.A495fsX75); the other a previously described misense mutation (p.A507V). In contrast to CD4 T cells, the majority of the few CD8 T cells showed expression of the ZAP70-related tyrosine kinase SYK that correlated with residual TCR signaling including calcium flux and degranulation. Our findings highlight the differential requirements of ZAP70 and SYK during thymic development, peripheral homeostasis as well as effector functions of CD4 and CD8 T cells.

A nonsense mutation in IKBKB causes combined immunodeficiency

AbstractIdentification of the molecular etiologies of primary immunodeficiencies has led to important insights into the development and function of the immune system. We report here the cause of combined immunodeficiency in 4 patients from 2 different consanguineous Qatari families with similar clinical and immunologic phenotypes. The patients presented at an early age with fungal, viral, and bacterial infections and hypogammaglobulinemia. Although their B- and T-cell numbers were normal, they had low regulatory T-cell and NK-cell numbers. Moreover, patients' T cells were mostly CD45RA+-naive cells and were defective in activation after T-cell receptor stimulation. All patients contained the same homozygous nonsense mutation in IKBKB (R286X), revealed by whole-exome sequencing with undetectable IKKβ and severely decreased NEMO proteins. Mutant IKKβ(R286X) was unable to complex with IKKα/NEMO. Immortalized patient B cells displayed impaired IκBα phosphorylation and NFκB nuclear translocation. These data indicate that mutated IKBKB is the likely cause of immunodeficiency in these 4 patients.

A homozygous mucosa-associated lymphoid tissue 1 (MALT1) mutation in a family with combined immunodeficiency

Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbers of T and B lymphocytes but with deficient cellular and humoral immunity. Most cases are sporadic, but autosomal recessive inheritance has been described. In most cases, the cause of CID remains unknown. We wanted to identify the genetic cause of CID in 2 siblings, the products of a first-cousin marriage, who experienced recurrent bacterial and candidal infections with bronchiectasis, growth delay, and early death. We performed immunologic, genetic, and biochemical studies in the 2 siblings, their family members, and healthy controls. Reconstitution studies were performed with T cells from mucosa-associated lymphoid tissue lymphoma-translocation gene 1-deficient (Malt1(-/-)) mice. The numbers of circulating T and B lymphocytes were normal, but T-cell proliferation to antigens and antibody responses to vaccination were severely impaired in both patients. Whole genome sequencing of 1 patient and her parents, followed by DNA sequencing of family members and healthy controls, showed the presence in both patients of a homozygous missense mutation in MALT1 that resulted in loss of protein expression. Analysis of T cells that were available on one of the patients showed severely impaired IκBα degradation and IL-2 production after activation, 2 events that depend on MALT1. In contrast to wild-type human MALT1, the patients' MALT1 mutant failed to correct defective nuclear factor-κB activation and IL-2 production in MALT1-deficient mouse T cells. An autosomal recessive form of CID is associated with homozygous mutations in MALT1. If future patients are found to be similarly affected, they should be considered as candidates for allogeneic hematopoietic cell transplantation.

Successful umbilical cord blood stem cell transplantation in a patient with Rothmund–Thomson syndrome and combined immunodeficiency

The ATP-dependent DNA helicase Q4 (RECQL4) belongs to a family of conserved RECQ helicases that are felt to be important in maintaining chromosomal integrity (Kitao et al., 1998, Genomics: 54 (3): 443-452). Deletions in the RECQL4 gene located on chromosome 8 region q24.3 have been associated with Rothmund-Thomson syndrome (RTS, OMIM 268400), a condition characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts and an increased risk of malignancy. We present a patient with a molecularly confirmed diagnosis of RTS with two unique genetic alterations in RECQL4 (IVS16-2A>T and IVS2+27_51del25), who at the age of 7 months nearly succumbed to Pneumocystis carinii pneumonia. Evaluation of his immune system demonstrated a T- B+ NK- phenotype with agammaglobulinemia consistent with combined immunodeficiency (CID). Studies to evaluate for known genetic causes of CID were not revealing. The patient received an umbilical cord blood (UCB) transplant with complete immune reconstitution. This report represents the first description of a CID phenotype and UCB transplantation in a patient with RTS.

DEFECTIVE EXPRESSION OF HLA-DR ANTIGENS (DR-Ag): ANOTHER CAUSE OF CHRONIC DIARRHEA

Defective expression of DR-Ag on mononuclear cells has been recently described as a new cause of combined immuno-deficiency, with chronic diarrhea and failure to thrive as main features. We were interested in relating these symptoms with an eventual defect of DR-Ag expression on enterocyte membranes, in 17 patients. 15 had diarrhea, starting between 1 and 6 months in 8, later on in 7, becoming chronic afterwards in all cases. Documented malabsorption was demonstrated in only 4. Candidiosis was noted in 16 and cryptosporidiosis in 3. Intestinal biopsies were performed in 10 patients : villous atrophy was partial in 8, subtotal in 2; intestinal IgA plasmocytes were absent in 4, strongly decreased in 3 out of 7. In 5 patients cryostat sections were incubated with various monoclonal antibodies directed against DR-Ag and lymphocyte subpopulations. In contrast to controls and coeliac patients, no enterocyte staining was visible either in the crypts or the villi. In 4 patients a strong epithelium and lamina propria infiltration of cytotoxic/suppressor lymphocytes was noted. In conclusion, chronic diarrhea, nearly constant in this disease, might be related more often to the near complete lack of immunological reactivity towards exogenous antigens than to the intestinal lesions observed. It is remarkable that the latter occured even though enterocytes did not express DR-Ag.