Clinical and functional spectrum of RAC2-related immunodeficiency.

ABSTRACT: Mutations in the small Rho-family guanosine triphosphate hydrolase RAC2, critical for actin cytoskeleton remodeling and intracellular signal transduction, are associated with neonatal severe combined immunodeficiency (SCID), infantile neutrophilic disorder resembling leukocyte adhesion deficiency (LAD), and later-onset combined immune deficiency (CID). We investigated 54 patients (23 previously reported) from 37 families yielding 15 novel RAC2 missense mutations, including one present only in homozygosity. Data were collected from referring physicians and literature reports with updated clinical information. Patients were grouped by presentation: neonatal SCID (n = 5), infantile LAD-like disease (n = 5), or CID (n = 44). Disease correlated to RAC2 activity: constitutively active RAS-like mutations caused neonatal SCID, dominant-negative mutations caused LAD-like disease, whereas dominant-activating mutations caused CID. Significant T- and B-lymphopenia with low immunoglobulins were seen in most patients; myeloid abnormalities included neutropenia, altered oxidative burst, impaired neutrophil migration, and visible neutrophil macropinosomes. Among 42 patients with CID with clinical data, upper and lower respiratory infections and viral infections were common. Twenty-three distinct RAC2 mutations, including 15 novel variants, were identified. Using heterologous expression systems, we assessed downstream effector functions including superoxide production, p21-activated kinase 1 binding, AKT activation, and protein stability. Confocal microscopy showed altered actin assembly evidenced by membrane ruffling and macropinosomes. Altered protein localization and aggregation were observed. All tested RAC2 mutant proteins exhibited aberrant function; no single assay was sufficient to determine functional consequence. Most mutants produced elevated superoxide; mutations unable to support superoxide formation were associated with bacterial infections. RAC2 mutations cause a spectrum of immune dysfunction, ranging from early onset SCID to later-onset combined immunodeficiencies depending on RAC2 activity. This trial was registered at www.clinicaltrials.gov as #NCT00001355 and #NCT00001467.

NOX2 deficiency enhances priming and activation of the NLRP3 inflammasome.

BACKGROUND: Nicotinamide adenine dinucleotide phosphate oxidase complex 2 (NOX2) deficiency, or chronic granulomatous disease (CGD), is an inborn error of immunity associated with increased susceptibility to infection and inflammatory manifestations. The pathophysiologic mechanism leading to the increased inflammatory response in CGD remains elusive. OBJECTIVE: We investigated the pathophysiologic mechanisms leading to NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation in NOX2 deficiency. METHODS: We used NOX2-deficient human primary and CRISPR-engineered macrophages to show that NOX2 deficiency enhances the inflammatory response mainly by modulating the 2 steps of NLRP3 inflammasome activation: its transcriptional priming and its posttranslational triggering. RESULTS: At the transcriptional level, NOX2-deficient phagocytes display increased priming of the NLRP3 inflammasome, as evidenced by increased transcription of NLRP3 and IL-1ß through an IL-1ß-dependent stimulation of the nuclear factor kappa-light-chain enhancer of activated B cells (aka NF-κB) pathway. At the posttranslational level, the absence of NOX2 triggers the NLRP3 inflammasome activation by increased K+ efflux and excessive release of mitochondrial DNA due to mitochondrial damage. Furthermore, NLRP3-driven pyroptosis in NOX2-deficient phagocytes further enhances NLRP3 activation by increasing K+ efflux. CONCLUSION: Our results unveil the role of NOX2 as a repressor of the inflammatory response at both transcriptional and posttranslational levels and pave the way for a more targeted approach to treating CGD patients with inflammatory manifestations.

Chronic granulomatous disease presenting at age 52 with fulminant mulch pneumonitis.

Chronic granulomatous disease should be considered in adults of any age in the presence of refractory and/or atypical or fulminant pulmonary infections. This case of new large deletions in NCF1 was presented with mulch pneumonitis without a significant history of infections.

Rituximab-induced hypogammaglobulinemia and infection risk in pediatric patients.

BACKGROUND: Rituximab is a B-cell depleting agent used in B-cell malignancies and autoimmune diseases. A subset of adult patients may develop prolonged and symptomatic hypogammaglobulinemia following rituximab treatment. However, this phenomenon has not been well delineated in the pediatric population. OBJECTIVES: This study sought to determine the prevalence, risk factors, and clinical significance of hypogammaglobulinemia following rituximab therapy in children. METHODS: This was a multicenter, retrospective cohort study that extracted clinical and immunological data from pediatric patients who received rituximab. RESULTS: The cohort comprised 207 patients (median age, 12.0 years). Compared to baseline values, there was a significant increase in hypogammaglobulinemia post-rituximab therapy, with an increase in prevalence of hypo-IgG (28.7%-42.6%; P = .009), hypo-IgA (11.1%-20.4%; P = .02), and hypo-IgM (20.0%-62.0%; P < .0001). Additionally, low IgG levels at any time post-rituximab therapy were associated with a higher risk of serious infections (34.4% vs 18.9%; odds ratio, 2.3; 95% CI, 1.1-4.8; P = .03). Persistent IgG hypogammaglobulinemia was observed in 27 of 101 evaluable patients (26.7%). Significant risk factors for persistent IgG hypogammaglobulinemia included low IgG and IgA levels pre-rituximab therapy. Nine patients (4.3%) within the study were subsequently diagnosed with a primary immunodeficiency, 7 of which received rituximab for autoimmune cytopenias. CONCLUSIONS: Hypogammaglobulinemia post-rituximab treatment is frequently diagnosed within the pediatric population. Low IgG levels are associated with a significant increase in serious infections, and underlying primary immunodeficiencies are relatively common in children receiving rituximab, thus highlighting the importance of immunologic monitoring both before and after rituximab therapy.

Very Early-Onset Inflammatory Manifestations of X-Linked Chronic Granulomatous Disease.

Chronic granulomatous disease (CGD) is a rare primary immune deficiency caused by mutations in genes coding for components of the nicotinamide adenine dinucleotide phosphate oxidase, characterized by severe and recurrent bacterial and fungal infections, together with inflammatory complications. Dysregulation of inflammatory responses are often present in this disease and may lead to granulomatous lesions, most often affecting the gastrointestinal (GI) and urinary tracts. Treatment of inflammatory complications usually includes corticosteroids, whereas antimicrobial prophylaxis is used for infection prevention. Curative treatment of both infectious susceptibility and inflammatory disease can be achieved by hematopoietic stem cell transplantation. We report herein three patients with the same mutation of the CYBB gene who presented with very early-onset and severe GI manifestations of X-linked CGD. The most severely affected patient had evidence of antenatal inflammatory involvement of the GI and urinary tracts. Extreme hyperleukocytosis with eosinophilia and high inflammatory markers were observed in all three patients. A Mycobacterium avium lung infection and an unidentified fungal lung infection occurred in two patients both during their first year of life, which is indicative of the severity of the disease. All three patients underwent bone marrow transplantation and recovered fully from their initial symptoms. To our knowledge, these are the first reports of patients with such an early-onset and severe inflammatory manifestations of CGD.

Recurrent Respiratory Infections Revealing CD8α Deficiency.

CD8A encodes the CD8α chain of the dimeric CD8 protein, a critical coreceptor of cytotoxic T cells. We report here the comprehensive immunological evaluation of a child with a CD8A missense mutation, providing evidence that CD8 deficiency increases susceptibility to recurrent respiratory infections without interfering with the TCR-mediated proliferation of T cells. These observations expand the known phenotypes associated with CD8 deficiency.

Faster T-cell development following gene therapy compared with haploidentical HSCT in the treatment of SCID-X1.

During the last decade, gene therapy via ex vivo gene transfer into autologous hematopoietic stem cells has emerged as a convincing therapy for severe combined immunodeficiency caused by ILR2G mutation (SCID-X1) despite the occurrence of genotoxicity caused by the integration of first-generation retroviral vectors. However, the place of gene therapy among the therapeutic armamentarium remains to be defined. We retrospectively analyze and compare clinical outcomes and immune reconstitution in 13 consecutive SCID-X1 patients having undergone haploidentical hematopoietic stem cell transplantation (HSCT) and 14 SCID-X1 patients treated with gene therapy over the same period at a single center level: the Necker Children's Hospital (Paris, France). Our results show a clear advantage in terms of T-cell development of gene therapy over HSCT with a mismatched donor. Patients treated with gene therapy display a faster T-cell reconstitution and a better long-term thymic output. Interestingly, this advantage of gene therapy vs haploidentical HSCT seems to be independent of the existence of clinical graft-versus-host disease in the latter condition. If data of safety are confirmed over the long term, gene therapy for SCID-X1 appears to be an equal, if not superior, alternative to haploidentical HSCT.

Rotavirus vaccine virus shedding, viremia and clearance in infants with severe combined immune deficiency.

We report for the first time Rotarix vaccine-acquired rotavirus infections with viremia in 2 infants vaccinated before being diagnosed with severe combined immune deficiency. Monitoring the first infant revealed that persistent rotavirus infection resolved after complete immune reconstitution was achieved by gene therapy.

CD45RA depletion in HLA-mismatched allogeneic hematopoietic stem cell transplantation for primary combined immunodeficiency: A preliminary study.

BACKGROUND: Combined immunodeficiencies (CIDs) form a heterogeneous group of inherited conditions that affect the development, function, or both of T cells. The treatment of CIDs with allogeneic hematopoietic stem cell transplantation (HSCT) is complicated by a high incidence of life-threatening infections and an increased risk of graft-versus-host disease (GVHD). OBJECTIVE: In view of the growing evidence that alloreactivity is mainly derived from human naive T cells, the selective depletion of naive T cells from allografts might constitute a way of reducing alloreactivity while maintaining memory T-cell responsiveness to pathogens. METHODS: Five consecutive patients with CIDs and chronic viral infections underwent an allogeneic, HLA-mismatched HSCT. Given the patients' infection status and the potential risk of severe GVHD in the mismatched setting, the CD34(-) fraction of the allograft was depleted of naive T cells by using magnetic CD45RA beads. RESULTS: Engraftment occurred in 4 of the 5 patients. No severe GVHD occurred. In the 4 engrafted patients viral infections were cleared within 2 months of the HSCT, and both cellular and humoral immunity were re-established within a year of the HSCT. An early T-cell response against viral pathogens was documented in 2 patients. CONCLUSION: The present pilot study shows that clinical-grade depletion of naive T cells from an allograft through the use of magnetic CD45RA beads seems to be a feasible and efficacious option for the treatment of patients with CIDs at high risk of GVHD, infection, or both in an HLA-mismatched setting.

A modified γ-retrovirus vector for X-linked severe combined immunodeficiency.

BACKGROUND: In previous clinical trials involving children with X-linked severe combined immunodeficiency (SCID-X1), a Moloney murine leukemia virus-based γ-retrovirus vector expressing interleukin-2 receptor γ-chain (γc) complementary DNA successfully restored immunity in most patients but resulted in vector-induced leukemia through enhancer-mediated mutagenesis in 25% of patients. We assessed the efficacy and safety of a self-inactivating retrovirus for the treatment of SCID-X1. METHODS: We enrolled nine boys with SCID-X1 in parallel trials in Europe and the United States to evaluate treatment with a self-inactivating (SIN) γ-retrovirus vector containing deletions in viral enhancer sequences expressing γc (SIN-γc). RESULTS: All patients received bone marrow-derived CD34+ cells transduced with the SIN-γc vector, without preparative conditioning. After 12.1 to 38.7 months of follow-up, eight of the nine children were still alive. One patient died from an overwhelming adenoviral infection before reconstitution with genetically modified T cells. Of the remaining eight patients, seven had recovery of peripheral-blood T cells that were functional and led to resolution of infections. The patients remained healthy thereafter. The kinetics of CD3+ T-cell recovery was not significantly different from that observed in previous trials. Assessment of insertion sites in peripheral blood from patients in the current trial as compared with those in previous trials revealed significantly less clustering of insertion sites within LMO2, MECOM, and other lymphoid proto-oncogenes in our patients. CONCLUSIONS: This modified γ-retrovirus vector was found to retain efficacy in the treatment of SCID-X1. The long-term effect of this therapy on leukemogenesis remains unknown. (Funded by the National Institutes of Health and others; ClinicalTrials.gov numbers, NCT01410019, NCT01175239, and NCT01129544.).

The BLNK adaptor protein has a nonredundant role in human B-cell differentiation.

BACKGROUND: Expression of the pre-B-cell receptor (pre-BCR) by pre-BII cells constitutes a crucial checkpoint in B-cell differentiation. Mutations that affect the pre-B-cell receptor result in early B-cell differentiation blockades that lead to primary B-cell immunodeficiencies. BLNK adaptor protein has a key role in the pre-B-cell receptor signaling cascade, as illustrated by the abnormal B-cell development in the 4 patients with BLNK gene defects reported to date. However, the BLNK protein's precise function in human B-cell differentiation has not been completely specified. METHODS: B-cell development, including IgVH and Vk chain repertoires analysis, was studied in the bone marrow of a new case of BLNK deficiency in vitro and in vivo. RESULTS: Here, we report on a patient with agammaglobulinemia, with a total absence of circulating B cells. We detected a homozygous mutation in BLNK, which leads to the complete abrogation of BLNK protein expression. In the bone marrow, we identified a severe differentiation blockade at the pre-BI- to pre-BII-cell transition. IgVH gene rearrangements and selection of the IgH repertoire were normal, whereas the patient's pre-BI cells showed very restricted usage of the IgVκ repertoire. Complementation of bone marrow progenitors from the patient with the BLNK gene and transplantation into NOD/SCID/γcko mice allowed the complete restoration of B-cell differentiation and a normal usage of the IgVκ genes.

Temporal and spatial compartmentalization of drug-resistant cytomegalovirus (CMV) in a child with CMV meningoencephalitis: implications for sampling in molecular diagnosis.

We describe a case of antiviral-resistant cytomegalovirus meningoencephalitis occurring after hematopoietic stem cell transplantation. Antiviral-resistant cytomegalovirus was identified in blood 16 months earlier. However, wild-type cytomegalovirus was evidenced in blood when the meningoencephalitis was diagnosed. Treatment of meningoencephalitis should be adapted to all previously identified resistance mutations in any compartment.

Prevalence and clinical impact of norovirus fecal shedding in children with inherited immune deficiencies.

We report the first prospective study describing the prevalence and clinical consequences of norovirus infection in hospitalized children with primary immunodeficiencies. Fecal samples from 62 children were systematically screened for virus. Norovirus was the most frequent pathogen (11 of 24 positive samples) found in both combined and humoral immunocompromised children. Norovirus shedding was associated with gastrointestinal symptoms and concomitant viremia in 54.5% and 25% of cases, respectively. Norovirus excretion was prolonged: 57.1% of fecal samples were still positive after a median of 9.5-months follow-up. Further large longitudinal studies are needed to evaluate the clinical consequences of norovirus shedding in patients with primary immunodeficiencies.