Defective expression of the CD40 ligand in X chromosome-linked immunoglobulin deficiency with normal or elevated IgM

A Bacteriophage Cocktail Targeting Yersinia pestis Provides Strong Post-Exposure Protection in a Rat Pneumonic Plague Model

Yersinia pestis , one of the deadliest bacterial pathogens ever known, is responsible for three plague pandemics and several epidemics, with over 200 million deaths during recorded history. Due to high genomic plasticity, Y. pestis is amenable to genetic mutations as well as genetic engineering that can lead to the emergence or intentional development of pan-drug resistant strains. The dissemination of such Y. pestis strains could be catastrophic, with public health consequences far more daunting than those caused by the recent COVID-19 pandemic. Thus, there is an urgent need to develop novel, safe, and effective treatment approaches for managing Y. pestis infections. This includes infections by antigenically distinct strains for which vaccines, none FDA approved yet, may not be effective, and those that cannot be controlled by approved antibiotics. Lytic bacteriophages provide one such alternative approach. In this study, we examined post-exposure efficacy of a bacteriophage cocktail, YPP-401, to combat pneumonic plague caused by Y. pestis CO92. YPP-401 is a four-phage preparation with a 100% lytic activity against a panel of 68 genetically diverse Y. pestis strains. Using a pneumonic plague aerosol challenge model in gender-balanced Brown Norway rats, YPP-401 demonstrated ∼88% protection when delivered 18 hours post-exposure for each of two administration routes (i.e., intraperitoneal and intranasal) in a dose-dependent manner. Our studies suggest that YPP-401 could provide an innovative, safe, and effective approach for managing Y. pestis infections, including those caused by naturally occurring or intentionally developed strains that cannot be managed by vaccines in development and antibiotics.

X-linked hyper IgM syndrome with severe eosinophilia: a case report and review of the literature

Background

Hyper IgM syndromes (HIGMS) are a group of rare primary immunodeficiency disorders. There are limited reports about HIGMS combined with severe eosinophilia.

Case presentation

In this report, we described a 2-year-old boy with chronic cough and symptoms of hypoxia. Lung computed tomography (CT) scan showed that diffuse ground-glass changes and eosinophils in peripheral blood increased significantly. Subsequent tests revealed a notable decrease in serum IgG and IgA. The lymphocyte subgroup classification was basically normal. Pneumocystis jirovecii were detected from the bronchoalveolar lavage fluid (BALF) of the patient by metagenomic next-generation sequencing (mNGS). After treatments of caspofungin combined with sulfamethoxazole, intravenous immunoglobulin (IVIG) replacement and anti-inflammatory steroid, the clinical symptoms and pulmonary imaging noticeably improved. The absolute eosinophil count (AEC) also returned to normal range. X-linked hyper IgM syndrome was confirmed by gene test. Two months after the diagnosis, the patient underwent allogeneic stem cell transplantation (HSCT) and has recovered well.

Conclusions

Children with HIGMS are prone to opportunistic infections such as Pneumocystis jirovecii pneumonia (PJP). Diffuse interstitial lung disease and hypoglobulinemia in a young child predict the diagnosis of a primary immunodeficiency (PID). mNGS has obvious advantages for obtaining etiological diagnosis of children with PIDs. Severe eosinophilia is rarely reported in this kind of PIDs. Considering literature review and the corresponding reaction to steroid, we proposed that eosinophilia in HIGMS might be related to infections. Steroid therapy can quickly relieve eosinophilia but is easy to rebound if the reduction is too fast. Once the diagnosis of HIGMS is confirmed, the earlier the HSCT, the better the prognosis.

System-Level Scenarios for the Elucidation of T Cell-Mediated Germinal Center B Cell Differentiation

Germinal center (GC) reactions are vital to the correct functioning of the adaptive immune system, through formation of high affinity, class switched antibodies. GCs are transient anatomical structures in secondary lymphoid organs where specific B cells, after recognition of antigen and with T cell help, undergo class switching. Subsequently, B cells cycle between zones of proliferation and somatic hypermutation and zones where renewed antigen acquisition and T cell help allows for selection of high affinity B cells (affinity maturation). Eventually GC B cells first differentiate into long-lived memory B cells (MBC) and finally into plasma cells (PC) that partially migrate to the bone marrow to encapsulate into long-lived survival niches. The regulation of GC reactions is a highly dynamically coordinated process that occurs between various cells and molecules that change in their signals. Here, we present a system-level perspective of T cell-mediated GC B cell differentiation, presenting and discussing the experimental and computational efforts on the regulation of the GCs. We aim to integrate Systems Biology with B cell biology, to advance elucidation of the regulation of high-affinity, class switched antibody formation, thus to shed light on the delicate functioning of the adaptive immune system. Specifically, we: i) review experimental findings of internal and external factors driving various GC dynamics, such as GC initiation, maturation and GCBC fate determination; ii) draw comparisons between experimental observations and mathematical modeling investigations; and iii) discuss and reflect on current strategies of modeling efforts, to elucidate B cell behavior during the GC tract. Finally, perspectives are specifically given on to the areas where a Systems Biology approach may be useful to predict novel GCBC-T cell interaction dynamics.

Primary Humoral Immune Deficiencies: Overlooked Mimickers of Chronic Immune-Mediated Gastrointestinal Diseases in Adults

In recent years, the incidence of immune-mediated gastrointestinal disorders, including celiac disease (CeD) and inflammatory bowel disease (IBD), is increasingly growing worldwide. This generates a need to elucidate the conditions that may compromise the diagnosis and treatment of such gastrointestinal disorders. It is well established that primary immunodeficiencies (PIDs) exhibit gastrointestinal manifestations and mimic other diseases, including CeD and IBD. PIDs are often considered pediatric ailments, whereas between 25 and 45% of PIDs are diagnosed in adults. The most common PIDs in adults are the selective immunoglobulin A deficiency (SIgAD) and the common variable immunodeficiency (CVID). A trend to autoimmunity occurs, while gastrointestinal disorders are common in both diseases. Besides, the occurrence of CeD and IBD in SIgAD/CVID patients is significantly higher than in the general population. However, some differences concerning diagnostics and management between enteropathy/colitis in PIDs, as compared to idiopathic forms of CeD/IBD, have been described. There is an ongoing discussion whether CeD and IBD in CVID patients should be considered a true CeD and IBD or just CeD-like and IBD-like diseases. This review addresses the current state of the art of the most common primary immunodeficiencies in adults and co-occurring CeD and IBD.

Molecular and cellular mechanisms underlying defective antibody responses

Primary immune deficiency is caused by genetic mutations that result in immune dysfunction and subsequent susceptibility to infection. Over the last decade there has been a dramatic increase in the number of genetically defined causes of immune deficiency including those which affect B-cell function. This has not only identified critical nonredundant pathways that control the generation of protective antibody responses but also revealed that immunodeficiency and autoimmunity are often closely linked. Here we explore the molecular and cellular mechanisms of these rare monogenic conditions that disrupt antibody production, which also have implications for understanding the causes of more common polygenic immune dysfunction.

Gastrointestinal Manifestations and Complications of Primary Immunodeficiency Disorders

Gastrointestinal (GI) involvement can be the presenting disease manifestation in patients with primary immunodeficiency disorders (PIDs). Infections and noninfectious diarrhea are frequent manifestations; however, malignancy and inflammatory and autoimmune-related GI diseases are also described. GI symptoms and disease seen in association with PIDs can mimic other diseases but are often resistant to conventional treatments owing to alternate disease mechanisms. Despite the advances in treatments for these conditions, therapy for immunodeficiency-related GI disease is often empiric.

CD40 ligand deficiency: treatment strategies and novel therapeutic perspectives

INTRODUCTION

CD40 ligand (CD40L) deficiency or X-linked Hyper-IgM syndrome is a severe primary immunodeficiency caused by mutations in the CD40L gene. Despite currently available treatments, CD40L-deficient patients remain susceptible to life-threatening infections and have poor long term survival. Areas covered: Here, we discuss clinical and immunological characteristics of CD40L deficiency as well as current therapeutic strategies used for patient management. This review highlights that beyond B cell defects, patients' susceptibility to opportunistic pathogens might be due to impaired T cell and innate immune responses. In this context, we discuss how better knowledge of CD40L function and regulation may result in the development of new treatments. Expert opinion: Despite the introduction of hematopoietic stem-cell transplantation, immunoglobulin replacement, granulocyte colony-stimulating factor (G-CSF) administration, and prophylactic antibiotic therapies, life-threatening infections still cause high morbidity and mortality among CD40L-deficient patients. The reasons for this inadequate response to current therapies remains poorly understood, but recent reports suggest the involvement of CD40L-CD40 interaction in early stages of the innate immune system ontogeny. The development of novel gene therapeutic approaches and the use of redirected immunotherapies represent alternative treatment methods that could offer reduced morbidity and mortality rates for patients with CD40L deficiency.

Hematopoietic stem cell transplantation for CD40 ligand deficiency: Results from an EBMT/ESID-IEWP-SCETIDE-PIDTC study

BACKGROUND

CD40 ligand (CD40L) deficiency, an X-linked primary immunodeficiency, causes recurrent sinopulmonary, Pneumocystis and Cryptosporidium species infections. Long-term survival with supportive therapy is poor. Currently, the only curative treatment is hematopoietic stem cell transplantation (HSCT).

OBJECTIVE

We performed an international collaborative study to improve patients' management, aiming to individualize risk factors and determine optimal HSCT characteristics.

METHODS

We retrospectively collected data on 130 patients who underwent HSCT for CD40L deficiency between 1993-2015. We analyzed outcome and variables' relevance with respect to survival and cure.

RESULTS

Overall survival (OS), event-free survival (EFS), and disease-free survival (DFS) were 78.2%, 58.1%, and 72.3% 5 years after HSCT. Results were better in transplantations performed in 2000 or later and in children less than 10 years old at the time of HSCT. Pre-existing organ damage negatively influenced outcome. Sclerosing cholangitis was the most important risk factor. After 2000, superior OS was achieved with matched donors. Use of myeloablative regimens and HSCT at 2 years or less from diagnosis associated with higher OS and DFS. EFS was best with matched sibling donors, myeloablative conditioning (MAC), and bone marrow-derived stem cells. Most rejections occurred after reduced-intensity or nonmyeloablative conditioning, which associated with poor donor cell engraftment. Mortality occurred mainly early after HSCT, predominantly from infections. Among survivors who ceased immunoglobulin replacement, T-lymphocyte chimerism was 50% or greater donor in 85.2%.

CONCLUSION

HSCT is curative in patients with CD40L deficiency, with improved outcome if performed before organ damage development. MAC is associated with better OS, EFS, and DFS. Prospective studies are required to compare the risks of HSCT with those of lifelong supportive therapy.

A curated collection of transcriptome datasets to investigate the molecular mechanisms of immunoglobulin E-mediated atopic diseases

Prevalence of allergies has reached ~20% of population in developed countries and sensitization rate to one or more allergens among school age children are approaching 50%. However, the combination of the complexity of atopic allergy susceptibility/development and environmental factors has made identification of gene biomarkers challenging. The amount of publicly accessible transcriptomic data presents an unprecedented opportunity for mechanistic discoveries and validation of complex disease signatures across studies. However, this necessitates structured methodologies and visual tools for the interpretation of results. Here, we present a curated collection of transcriptomic datasets relevant to immunoglobin E-mediated atopic diseases (ranging from allergies to primary immunodeficiencies). Thirty-three datasets from the Gene Expression Omnibus, encompassing 1860 transcriptome profiles, were made available on the Gene Expression Browser (GXB), an online and open-source web application that allows for the query, visualization and annotation of metadata. The thematic compositions, disease categories, sample number and platforms of the collection are described. Ranked gene lists and sample grouping are used to facilitate data visualization/interpretation and are available online via GXB (http://ige.gxbsidra.org/dm3/geneBrowser/list). Dataset validation using associated publications showed good concordance in GXB gene expression trend and fold-change.

Hematopoietic Stem Cell Transplantation for Combined Immunodeficiencies, on Behalf of IEWP-EBMT

Combined immunodeficiencies (CIDs) are a clinically and genetically heterogeneous group of primary immunodeficiencies (PIDs) that affect T-lymphocyte immunity with abnormal development or function. As compared to severe combined immune deficiencies (SCID), these patients are usually diagnosed later. They display a broad infectious susceptibility; immune dysregulation manifestations and chronic lymphoproliferation are also frequent. These complications and their specific treatments can lead to persistent damage to several organs. Prognosis of CIDs is worse as compared to other PIDs. The curative treatment is usually hematopoietic stem cell transplantation (HSCT), but difficult questions remain regarding the definitive indication of HSCT and its timing; the final decision depends on a conjunction of factors such as immunological parameters, severity of clinical manifestations, and natural history of the disease, when molecular diagnosis is known. CD40L deficiency, a CID caused by mutations in CD40LG gene, well illustrates the dilemma between HSCT vs. long-term supportive treatment. This disease leads to higher risk of developing infections from bacterial and intracellular pathogens, especially Pneumocystis and Cryptosporidium spp. While supportive care allows improved survival during childhood, organ damages may develop with increasing age, mainly chronic lung disease and biliary tract disease (secondary to Cryptosporidium spp. infection) that may evolve later to sclerosing cholangitis, a severe complication associated with increased mortality. Early HSCT before organ damage development is associated with best survival and cure rate, while HSCT remains a risky therapeutic option for older patients, for those with organ damage, especially severe liver disease, and/or for those with limited or no donor availability. Prospective studies are needed to analyze risks of HSCT compared to those of life-long supportive therapy, including quality of life measures.

The TNF Family of Ligands and Receptors: Communication Modules in the Immune System and Beyond

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies (TNFSF/TNFRSF) include 19 ligands and 29 receptors that play important roles in the modulation of cellular functions. The communication pathways mediated by TNFSF/TNFRSF are essential for numerous developmental, homeostatic, and stimulus-responsive processes in vivo. TNFSF/TNFRSF members regulate cellular differentiation, survival, and programmed death, but their most critical functions pertain to the immune system. Both innate and adaptive immune cells are controlled by TNFSF/TNFRSF members in a manner that is crucial for the coordination of various mechanisms driving either co-stimulation or co-inhibition of the immune response. Dysregulation of these same signaling pathways has been implicated in inflammatory and autoimmune diseases, highlighting the importance of their tight regulation. Investigation of the control of TNFSF/TNFRSF activities has led to the development of therapeutics with the potential to reduce chronic inflammation or promote anti-tumor immunity. The study of TNFSF/TNFRSF proteins has exploded over the last 30 yr, but there remains a need to better understand the fundamental mechanisms underlying the molecular pathways they mediate to design more effective anti-inflammatory and anti-cancer therapies.

The hyper IgM syndromes: Epidemiology, pathogenesis, clinical manifestations, diagnosis and management

Hyper Immunoglobulin M syndrome (HIGM) is a rare primary immunodeficiency disorder characterized by low or absent levels of serum IgG, IgA, IgE and normal or increased levels of serum IgM. Various X-linked and autosomal recessive/dominant mutations have been reported as the underlying cause of the disease. Based on the underlying genetic defect, the affected patients present a variety of clinical manifestations including pulmonary and gastrointestinal complications, autoimmune disorders, hematologic abnormalities, lymphoproliferation and malignancies which could be controlled by multiple relevant therapeutic approaches. Herein, the epidemiology, pathogenesis, clinical manifestations, diagnosis, management, prognosis and treatment in patients with HIGM syndrome have been reviewed.

Class-Switch Recombination (CSR)/Hyper-IgM (HIGM) Syndromes and Phosphoinositide 3-Kinase (PI3K) Defects

Antibody production and function represent an essential part of the immune response, particularly in fighting bacterial and viral infections. Multiple immunological phenotypes can result in dysregulation of the immune system humoral compartment, including class-switch recombination (CSR) defects associated with hyper-IgM (HIGM) syndromes. The CSR/HIGM syndromes are defined by the presence of normal or elevated plasma IgM levels in the context of low levels of switched IgG, IgA, and IgE isotypes. Recently described autosomal dominant gain-of-function (GOF) mutations in PIK3CD and PIK3R1 cause combined immunodeficiencies that can also present as CSR/HIGM defects. These defects, their pathophysiology and derived clinical manifestations are described in depth. Previously reported forms of CSR/HIGM syndromes are briefly reviewed and compared to the phosphoinositide 3-kinase (PI3K) pathway defects. Diseases involving the PI3K pathway represent a distinctive subset of CSR/HIGM syndromes, presenting with their own characteristic clinical and laboratory attributes as well as individual therapeutic approaches.

Clinical and molecular features of X-linked hyper IgM syndrome - An experience from North India

X-linked hyper IgM Syndrome (XLHIGM), the most frequent form of the Hyper IgM syndromes is a primary immune deficiency resulting from a mutation in the CD40 ligand gene (CD40LG). We analyzed the clinical and laboratory features of ten patients with XLHIGM, who were diagnosed at a tertiary care hospital in North India. Most common infections were sinopulmonary infections (80%) and diarrhea (50%). Sclerosing cholangitis and necrotising fasciitis were noted in one patient each. Three novel mutations in CD40LG (c.429_429 delA, p. G144DfsX5; c.500 G > A, p.G167E and c.156 G > C, p.K52 N) were detected. In addition, we found one missense mutation, two splice site mutations and two large deletions, which have been previously reported. Four (4) patients had expired at the time of analysis. We report the first series of XLHIGM from North India where we have documented unique features such as pulmonary alveolar proteinosis and infections with Mycobacterium sp.

Molecular control of B-cell homeostasis in health and malignancy

Altered B-cell homeostasis underlies a wide range of pathologies, from cancers to autoimmunity and immunodeficiency. The molecular safeguards against those disorders, which also allow effective immune responses, are therefore particularly critical. Here, we review recent findings detailing the fine control of B-cell homeostasis, during B-cell development, maturation in the periphery and during activation and differentiation into antibody-producing cells.

Clinical Phenotypes of Hyper-IgM Syndromes

The primary immunodeficiency (PID) diseases comprise a heterogeneous group of inherited disorders of immune function. Technical advancements in whole-genome, whole-exome, and RNA-sequencing have seen the explosion of genetic discoveries in the field of PIDs. The present review aims to focus on a group of immunodeficiency disorders associated with elevated levels of IgM (hyper IgM; HIGM) and provides a clinical differential diagnosis. Most patients present for evaluation of immunodeficiency due to recurrent infections, and laboratory studies show either a clear isolated elevation of serum immunoglobulin M (IgM) with low or absent IgG, IgA, and IgE. Alternatively, IgM levels may be normal or moderately elevated while other serum immunoglobulins are reported below the norms for age but not absent. Mechanistically, these disorders are recognized as defects in immunoglobulin (Ig) class switch recombination (CSR). Importantly, to safeguard genetic stability, CSR utilizes elements of the DNA repair machinery including multi-protein complexes involved in mismatch repair (MMR). Therefore, it is not uncommon for defects in the DNA repair machinery, to present with laboratory findings of HIGM. This review will discuss clinical phenotypes associated with congenital defects associated with HIGM. Clinical manifestations, relevant immunologic testing, inheritance pattern, molecular diagnosis, presumed pathogenesis, and OMIM number, when annotated are compiled. Accepted therapeutic options, when available, are reviewed for each condition discussed.

Fifty years later: Emerging functions of IgE antibodies in host defense, immune regulation, and allergic diseases

Fifty years ago, after a long search, IgE emerged as the circulating factor responsible for triggering allergic reactions. Its extremely low concentration in plasma created significant hurdles for scientists working to reveal its identity. We now know that IgE levels are invariably increased in patients affected by atopic conditions and that IgE provides the critical link between the antigen recognition role of the adaptive immune system and the effector functions of mast cells and basophils at mucosal and cutaneous sites of environmental exposure. This review discusses the established mechanisms of action of IgE in pathologic immediate hypersensitivity, as well as its multifaceted roles in protective immunity, control of mast cell homeostasis, and its more recently revealed immunomodulatory functions.

CD40L-Dependent Pathway Is Active at Various Stages of Rheumatoid Arthritis Disease Progression

The inflammatory CD40-CD40L pathway is implicated in various autoimmune diseases, but the activity status of this pathway in various stages of rheumatoid arthritis (RA) progression is unknown. In this study, we used gene signatures of CD40L stimulation derived from human immature dendritic cells and naive B cells to assess the expression of CD40-downstream genes in synovial tissues from anti-citrullinated protein Ab-positive arthralgia, undifferentiated arthritis (UA), early RA, and established RA cohorts in comparison with healthy donors. Interestingly, the expression of CD40LG and active full-length CD40 was increased in the disease tissues, whereas that of a dominant-negative CD40 isoform was decreased. Gene set variation analysis revealed that CD40L-responsive genes in immature dendritic cells and naive B cells were significantly enriched in synovial tissues from UA, early RA, and established RA patients. Additionally, CD40L-induced naive B cell genes were also significantly enriched in synovial tissues from arthralgia patients. In our efforts to characterize downstream mediators of CD40L signaling, we have identified GPR120 and KDM6B as novel components of the pathway. In conclusion, our data suggest that therapeutic CD40-CD40L blocking agents may prove efficacious not only in early and established RA, but also in inhibiting the progression of the disease from arthralgia or UA to RA.

Genome-Edited T Cell Therapies

PURPOSE OF REVIEW

Alternative approaches to conventional drug-based cancer treatments have seen T cell therapies deployed more widely over the last decade. This is largely due to their ability to target and kill specific cell types based on receptor recognition. Introduction of recombinant T cell receptors (TCRs) using viral vectors and HLA-independent T cell therapies using chimeric antigen receptors (CARs) are discussed. This article reviews the tools used for genome editing, with particular emphasis on the applications of site-specific DNA nuclease mediated editing for T cell therapies.

RECENT FINDINGS

Genetic engineering of T cells using TCRs and CARs with redirected antigen-targeting specificity has resulted in clinical success of several immunotherapies. In conjunction, the application of genome editing technologies has resulted in the generation of HLA-independent universal T cells for allogeneic transplantation, improved T cell sustainability through knockout of the checkpoint inhibitor, programmed cell death protein-1 (PD-1), and has shown efficacy as an antiviral therapy through direct targeting of viral genomic sequences and entry receptors.

SUMMARY

The combined use of engineered antigen-targeting moieties and innovative genome editing technologies have recently shown success in a small number of clinical trials targeting HIV and hematological malignancies and are now being incorporated into existing strategies for other immunotherapies.

Long-term outcomes of 176 patients with X-linked hyper-IgM syndrome treated with or without hematopoietic cell transplantation

BACKGROUND

X-linked hyper-IgM syndrome (XHIGM) is a primary immunodeficiency with high morbidity and mortality compared with those seen in healthy subjects. Hematopoietic cell transplantation (HCT) has been considered a curative therapy, but the procedure has inherent complications and might not be available for all patients.

OBJECTIVES

We sought to collect data on the clinical presentation, treatment, and follow-up of a large sample of patients with XHIGM to (1) compare long-term overall survival and general well-being of patients treated with or without HCT along with clinical factors associated with mortality and (2) summarize clinical practice and risk factors in the subgroup of patients treated with HCT.

METHODS

Physicians caring for patients with primary immunodeficiency diseases were identified through the Jeffrey Modell Foundation, United States Immunodeficiency Network, Latin American Society for Immunodeficiency, and Primary Immune Deficiency Treatment Consortium. Data were collected with a Research Electronic Data Capture Web application. Survival from time of diagnosis or transplantation was estimated by using the Kaplan-Meier method compared with log-rank tests and modeled by using proportional hazards regression.

RESULTS

Twenty-eight clinical sites provided data on 189 patients given a diagnosis of XHIGM between 1964 and 2013; 176 had valid follow-up and vital status information. Sixty-seven (38%) patients received HCT. The average follow-up time was 8.5 ± 7.2 years (range, 0.1-36.2 years). No difference in overall survival was observed between patients treated with or without HCT (P = .671). However, risk associated with HCT decreased for diagnosis years 1987-1995; the hazard ratio was significantly less than 1 for diagnosis years 1995-1999. Liver disease was a significant predictor of overall survival (hazard ratio, 4.9; 95% confidence limits, 2.2-10.8; P < .001). Among survivors, those treated with HCT had higher median Karnofsky/Lansky scores than those treated without HCT (P < .001). Among patients receiving HCT, 27 (40%) had graft-versus-host disease, and most deaths occurred within 1 year of transplantation.

CONCLUSION

No difference in survival was observed between patients treated with or without HCT across all diagnosis years (1964-2013). However, survivors treated with HCT experienced somewhat greater well-being, and hazards associated with HCT decreased, reaching levels of significantly less risk in the late 1990s. Among patients treated with HCT, treatment at an early age is associated with improved survival. Optimism remains guarded as additional evidence accumulates.

X-linked Hyper IgM Syndrome Presenting as Pulmonary Alveolar Proteinosis

PURPOSE

X-linked hyper IgM syndrome (XHIGM) is a combined immunodeficiency caused by mutations in the CD40 ligand (CD40L) gene that typically results in decreased or absent CD40L expression on activated T cells, leading to defective class switching and somatic hypermutation. We describe an infant who presented with respiratory failure due to pulmonary alveolar proteinosis (PAP) with a novel damaging missense mutation in the CD40L gene.

METHODS

Whole exome sequencing (WES) was used to identify a mutation in the CD40L gene. CD40L expression and function were determined by flow cytometry.

RESULTS

A 5-month-old previously-healthy male presented with respiratory failure and diffuse pulmonary ground glass opacities on CT scan of the chest. Laboratory evaluation revealed an undetectable IgG, normal IgA, and elevated IgM. A bronchoalveolar lavage demonstrated pulmonary alveolar proteinosis. WES demonstrated a c.608G > C mutation in the CD40L gene resulting in p.R203T. Flow cytometry demonstrated normal CD40L expression on activated T cells but absent binding of CD40-Ig to CD40L on activated patient T cells.

CONCLUSIONS

The clinical manifestations of XHIGM in our patient had several unique features, including the presentation with PAP, normal serum IgA, and expression of non-functional CD40L on activated T cells. To our knowledge, this is the first published case of PAP in a patient with XHIGM.

Regulated expression of murine CD40L by a lentiviral vector transcriptionally targeted through its endogenous promoter

BACKGROUND

Targeted lentiviral vectors may contribute to circumventing genotoxicity associated with uncontrolled transcription of therapeutic genes. Some vectors replacing strong viral sequences for gene promoters such as β-globin, CD4, CD19 or Igκ were able to drive tissue-specific expression of the transgene. Gene therapy, however, faces even greater hurdles when the therapeutic transgene is subject to strict regulatory mechanisms. This is the case of the CD40LG gene, which encodes for the CD154 (also known as CD40L) molecule, transiently expressed upon activation on CD4(+) T cells. Mutations in this gene cause the X-linked hyper IgM syndrome (HIGM1) in humans because the interaction of CD40L with its ligand CD40 triggers signals that are critical for the immunobiology of B lymphocytes.

METHODS

We developed a lentiviral vector containing the murine Cd40lg cDNA under the control of its endogenous promoter.

RESULTS

The CD4(+) BW5147 T cells transduced with the pCd40lg-Cd40lg lentiviral vector express CD40L only upon stimulation. The intensity of the expression correlates with the number of vector integrations per cell and detected molecules rapidly decay after removing the stimulating agent. The tissue-specific, activation-dependent and reversible expression of CD40L fully mimics the physiological induction and disappearance of the molecule from the surface of murine T lymphocytes. The functional activity of the regulated lentiviral vector is demonstrated by the ability of transduced BW5147 cells to promote the proliferation of purified B cell splenocytes.

CONCLUSIONS

We have developed a fine-regulated lentiviral vector that can be a model for expressing molecules subject to stringent regulatory mechanisms.

Hyper IgM Syndrome: a Report from the USIDNET Registry

PURPOSE

The United States Immunodeficiency Network (USIDNET) patient registry was used to characterize the presentation, genetics, phenotypes, and treatment of patients with Hyper IgM Syndrome (HIGM).

METHODS

The USIDNET Registry was queried for HIGM patient data collected from October 1992 to July 2015. Data fields included demographics, criteria for diagnosis, pedigree analysis, mutations, clinical features, treatment and transplant records, laboratory findings, and mortality.

RESULTS

Fifty-two physicians entered data from 145 patients of ages 2 months to 62 years (median 12 years); 131 were males. Using patients' age at last entry, data from 2072 patient years are included. Mutations were recorded for 85 subjects; 82 were in CD40LG. Eighteen subjects had non-X-linked HIGM. 40 % had a normal serum IgM and 15 %, normal IgA. Infections were reported for 91 %, with pulmonary, ear, and sinus infections being the most common. 42 % had Pneumocystis jirovecii pneumonia; 6 % had Cryptosporidium. 41 % had neutropenia. 78 % experienced non-infectious complications: chronic diarrhea (n = 22), aphthous ulcers (n = 28), and neoplasms (n = 8) including colon cancer, adrenal adenoma, liver adenocarcinoma, pancreatic carcinoid, acute myeloid leukemia, hepatoma, and, in a female with an autosomal dominant gain of function mutation in PIK3CD, an ovarian dysgerminoma. Thirteen patients had a hematopoietic marrow or stem cell transplant; three had solid organ transplants. Thirteen were known to have died (median age = 14 years).

CONCLUSIONS

Analysis of the USIDNET Registry provides data on the common clinical features of this rare syndrome, and in contrast with previously published data, demonstrates longer survival times and reduced gastrointestinal manifestations.

Regulation of IgE Responses by γδ T Cells

Immunoglobulin E (IgE) antibodies play a crucial role in host defense against parasite infections. However, inappropriate IgE responses are also involved in the pathogenesis of allergic diseases. The generation of IgE antibodies is a tightly controlled process regulated by multiple transcription factors, cytokines, and immune cells including γδ T cells. Accumulating evidence demonstrates that γδ T cells play a critical role in regulating IgE responses; however, both IgE-enhancing and IgE-suppressive effects are suggested for these cells in different experimental systems. In this review, we examine the available evidence and discuss the role of γδ T cells in IgE regulation both in the context of antigen-induced immune responses and in the state of partial immunodeficiency.

PU.1 Expression in T Follicular Helper Cells Limits CD40L-Dependent Germinal Center B Cell Development

PU.1 is an ETS family transcription factor that is important for the development of multiple hematopoietic cell lineages. Previous work demonstrated a critical role for PU.1 in promoting Th9 development and in limiting Th2 cytokine production. Whether PU.1 has functions in other Th lineages is not clear. In this study, we examined the effects of ectopic expression of PU.1 in CD4(+) T cells and observed decreased expression of genes involved with the function of T follicular helper (Tfh) cells, including Il21 and Tnfsf5 (encoding CD40L). T cells from conditional mutant mice that lack expression of PU.1 in T cells (Sfpi1(lck-/-)) demonstrated increased production of CD40L and IL-21 in vitro. Following adjuvant-dependent or adjuvant-independent immunization, we observed that Sfpi1(lck-/-) mice had increased numbers of Tfh cells, increased germinal center B cells (GCB cells), and increased Ab production in vivo. This correlated with increased expression of IL-21 and CD40L in Tfh cells from Sfpi1(lck-/-) mice compared with control mice. Finally, although blockade of IL-21 did not affect GCB cells in Sfpi1(lck-/-) mice, anti-CD40L treatment of immunized Sfpi1(lck-/-) mice decreased GCB cell numbers and Ag-specific Ig concentrations. Together, these data indicate an inhibitory role for PU.1 in the function of Tfh cells, germinal centers, and Tfh-dependent humoral immunity.

Hematopoietic stem cell transplant for hyper-IgM syndrome due to CD40L defects: A single-center experience

HIGMI is a disease with a high risk for morbidity and mortality. HSCT has been shown to be a curative option. This study retrospectively reviewed and analyzed data from five patients who received HSCT at King Faisal Specialist Hospital & Research Centre (KFSH&RC) in Riyadh, Saudi Arabia, between 2005 and 2013. Five patients with HIGMI syndrome underwent HSCT at a median age of 41 months (range, 9-72 months). The median time from diagnosis to transplantation was 30 months (range, 5-58 months). For all five patients, the donors were HLA-identical siblings. In three patients, the conditioning regimen was composed of BU and CY. Fludarabine and melphalan with either ATG or alemtuzumab was used in two patients. For GVHD prophylaxis, cyclosporine was used in two patients, and the combination of cyclosporine and MTX was used in three patients. The survival rate was 100%, with a median follow-up of 69 months (range, 13-100 months). All patients engrafted. Two patients developed acute GVHD. Four patients showed complete immune recovery with positive CD40L expression in activated T cells and discontinued IVIG replacement. HSCT in early stage from an HLA-matched sibling donor is potentially effective at curing the disease.

A brief history of T cell help to B cells

In celebration of the 50th anniversary of the discovery of B cells, I take a look back at the history of T cell help to B cells, which was discovered 47 years ago. In addition, I summarize and categorize the distinct molecules that are expressed by CD4(+) T cells that constitute 'help' to B cells, and particularly the molecules expressed by T follicular helper (TFH) cells, which are the specialized providers of help to B cells.

Role of sphingosine kinase 1 and sphingosine-1-phosphate in CD40 signaling and IgE class switching

The tumor necrosis factor (TNF) receptor family member CD40 plays an essential role in the activation of antigen-presenting cells, B cell maturation, and immunoglobulin (Ig) class switching critical for adaptive immunity. Although the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) and the kinase that produces it, sphingosine kinase 1 (SphK1), have long been implicated in the actions of TNF mediated by engagement of TNFR1, nothing is yet known of their role in CD40-mediated events. We have now found that ligation of CD40 activates and translocates SphK1 to the plasma membrane, leading to generation of S1P. SphK1 inhibition in human tonsil B cells, as well as inhibition or deletion of SphK1 in mouse splenic B cells, significantly reduced CD40-mediated Ig class switching and plasma cell differentiation ex vivo. Optimal activation of downstream CD40 signaling pathways, including NF-κB, p38, and JNK, also required SphK1. In mice treated with a SphK1 inhibitor or in SphK1(-/-) mice, isotype switching to antigen-specific IgE was decreased in vivo by 70 and 55%, respectively. Our results indicate that SphK1 is important for CD40-mediated B cell activation and regulation of humoral responses and suggest that targeting SphK1 might be a useful therapeutic approach to control antigen-specific IgE production.

ICON: the early diagnosis of congenital immunodeficiencies

Primary immunodeficiencies are intrinsic defects in the immune system that result in a predisposition to infection and are frequently accompanied by a propensity to autoimmunity and/or immunedysregulation. Primary immunodeficiencies can be divided into innate immunodeficiencies, phagocytic deficiencies, complement deficiencies, disorders of T cells and B cells (combined immunodeficiencies), antibody deficiencies and immunodeficiencies associated with syndromes. Diseases of immune dysregulation and autoinflammatory disorder are many times also included although the immunodeficiency in these disorders are often secondary to the autoimmunity or immune dysregulation and/or secondary immunosuppression used to control these disorders. Congenital primary immunodeficiencies typically manifest early in life although delayed onset are increasingly recognized. The early diagnosis of congenital immunodeficiencies is essential for optimal management and improved outcomes. In this International Consensus (ICON) document, we provide the salient features of the most common congenital immunodeficiencies.

Toward a Molecular Understanding of Adaptive Immunity: A Chronology, Part III

Early reports on T cell antigen receptor (TCR) signaling uncovered a rapid increase in intracellular calcium concentration and the activation of calcium-dependent protein kinase as necessary for T cell activation. Cytolytic T cell clones were instrumental in the discovery of intracellular cytolytic granules, and the isolation of the perforin and granzyme molecules as the molecular effectors of cell-mediated lysis of target cells via apoptosis. Cytolytic T cell clones and TCR cDNA clones were also instrumental for the generation of TCR transgenic animals, which provided definitive evidence for negative selection of self-reactive immature thymocytes. In addition, studies of TCR complex signaling of immature thymocytes compared with mature T cells were consistent with the interpretation that negative selection occurs as a consequence of the incapacity of immature cells to produce IL-2, resulting in cytokine deprivation apoptosis. By comparison, taking advantage of cloned TCRs derived from T cell clones reactive with male-specific molecules, using TCR transgenic mice it was possible to document positive selection of female thymocytes when the male-specific molecules were absent. Focusing on the molecular mechanisms of T cell "help" for the generation of antibody-forming cells following the path opened by the elucidation of the IL-2 molecule, several groups were successful in the identification, isolation, and characterization of three new interleukin molecules (IL-4, IL-5, and IL-6) that promote the proliferation and differentiation of B cells. In addition, the identification of a B cell surface molecule (CD40) that augmented B cell antigen receptor-stimulated proliferation and differentiation led to the discovery of a T cell activation surface molecule that proved to be the CD40-ligand, thus finally providing a molecular explanation for "linked or cognate" recognition when T cells and B cells interact physically. Accordingly, the decade after the generation of the first T cell clones saw the elucidation of the molecular mechanisms of T cell cytotoxicity and T cell help, thereby expanding the number of molecules responsible for adaptive T cell immunity.

First report of the Hyper-IgM syndrome Registry of the Latin American Society for Immunodeficiencies: novel mutations, unique infections, and outcomes

Hyper-IgM (HIGM) syndrome is a heterogeneous group of disorders characterized by normal or elevated serum IgM levels associated with absent or decreased IgG, IgA and IgE. Here we summarize data from the HIGM syndrome Registry of the Latin American Society for Immunodeficiencies (LASID). Of the 58 patients from 51 families reported to the registry with the clinical phenotype of HIGM syndrome, molecular defects were identified in 37 patients thus far. We retrospectively analyzed the clinical, immunological and molecular data from these 37 patients. CD40 ligand (CD40L) deficiency was found in 35 patients from 25 families and activation-induced cytidine deaminase (AID) deficiency in 2 unrelated patients. Five previously unreported mutations were identified in the CD40L gene (CD40LG). Respiratory tract infections, mainly pneumonia, were the most frequent clinical manifestation. Previously undescribed fungal and opportunistic infections were observed in CD40L-deficient patients but not in the two patients with AID deficiency. These include the first cases of pneumonia caused by Mycoplasma pneumoniae, Serratia marcescens or Aspergillus sp. and diarrhea caused by Microsporidium sp. or Isospora belli. Except for four CD40L-deficient patients who died from complications of presumptive central nervous system infections or sepsis, all patients reported in this study are alive. Four CD40L-deficient patients underwent successful bone marrow transplantation. This report characterizes the clinical and genetic spectrum of HIGM syndrome in Latin America and expands the understanding of the genotype and phenotype of this syndrome in tropical areas.

Gene hunting in the genomic era: approaches to diagnostic dilemmas in patients with primary immunodeficiencies

There are more than 180 different genetic causes of primary immunodeficiencies identified to date. Approaches for identifying causative mutations can be broadly classified into 3 strategies: (1) educated guesses based on known signaling pathways essential for immune cell development and function, (2) similarity of clinical phenotypes to mouse models, and (3) unbiased genetic approaches. Next-generation DNA sequencing permits efficient sequencing of whole genomes or exomes but also requires strategies for filtering vast amounts of data. Recent studies have identified ways to solve difficult cases, such as diseases with autosomal dominant inheritance, incomplete penetrance, or mutations in noncoding regions. This review focuses on recently identified primary immunodeficiencies to illustrate the strategies, technologies, and potential pitfalls in finding novel causes of these diseases.

Clinical features and genetic analysis of Taiwanese patients with the hyper IgM syndrome phenotype

OBJECTIVES

Hyper IgM syndrome (HIGM), characterized by recurrent infections, low serum IgG and IgA, normal or elevated IgM, defective class switch recombination and somatic hypermutation, are heterogeneous disorders with at least 6 distinct molecular defects, including the CD40 ligand (CD40L) and the nuclear factor κB essential modulator (NEMO, also known as IKKγ) genes (both X-linked), the CD40, activation-induced cytidine deaminase (AICDA or AID), uracil-DNA glycosylase genes (autosomal recessive) and IκBα (IKBA) (autosomal dominant). Our objective was to determine the molecular basis and clinical features of Taiwanese patients with the HIGM phenotype.

METHODS

Clinical manifestations and candidate genes were analyzed in a nationwide population-based study.

RESULTS

Among 14 patients (12 unrelated families) since 2003, 10 patents were identified (8 families) with CD40L mutations, including 2 novel deletions of "A" nucleotide (Del 347A and Del 366A), both frameshift and stop at the 127th location; 1 novel AID deletion mutation lack of the 37thAsp and 38th Ser; 1 ataxia-telangiectasia mutation; and 1 deletion of chromosome 1q42. An adult-onset patient with mutant (Thr254Met)CD40L had approximately 30% detectable affinity and therefore less severity. Memory B cells decreased in patients with CD40L and activation-induced cytidine deaminase mutations. Three mortalities encompassed renal cell carcinoma in 1 patient with (Tyr169Asn)CD40L, pneumothorax in 1 with (Tyr140Stop)CD40L and pneumonia after chemotherapy in an ataxia-telangiectasia patient. One patient without detectable genetic defects but normal lymphocyte proliferation resembled the mild form of common variable immune deficiency phenotype.

CONCLUSIONS

In contrast to those with AICDA mutation, small chromosome 1 q42 deletion and unknown genetic defect, the majority (10/14; 71.4%) with CD40L mutations except (Thr254Met) and an ataxia-telangiectasia patient had the severe form of HIGM phenotype.

Pneumocystis jiroveci pneumonia revealing de novo mutation causing X-linked hyper-IgM syndrome in an infant male. The first case reported from French Guiana

BACKGROUND

The X-linked hyper-IgM (XHIM) syndrome is a rare form of primary immunodeficiency disorder characterized by hypogammaglobulinemia and impaired cell immunity.

OBSERVATION

We report history of Guianese family affected by XHIM syndrome. The eldest boy died at 7 months from pneumonia. The 5-month-old youngest boy presented with a potentially fatal episode of Pneumocystis jiroveci pneumonia. The diagnosis was done in the Pediatric Unit of Immunohematology of Hopital Necker in Paris.

CONCLUSIONS

This report points to the importance of diagnosis of XHIM to allow early treatment to minimize serious infections and to detect carriers in XHIM families for genetic counseling.

Expanding the clinical and genetic spectrum of human CD40L deficiency: the occurrence of paracoccidioidomycosis and other unusual infections in Brazilian patients

CD40 ligand (CD40L) deficiency or X-linked hyper-IgM syndrome (X-HIGM) is a well-described primary immunodeficiency in which Pneumocystis jiroveci pneumonia is a common clinical feature. We have identified an unusual high incidence of fungal infections and other not yet described infections in a cohort of 11 X-HIGM patients from nine unrelated Brazilian families. Among these, we describe the first case of paracoccidioidomycosis (PCM) in X-HIGM. The molecular genetic analysis of CD40L was performed by gene sequencing and evaluation of CD40L protein expression. Nine of these 11 patients (82%) had fungal infections. These included fungal species common to CD40L deficiency (P. jiroveci and Candida albicans) as well as Paracoccidioides brasiliensis. One patient presented with PCM at age 11 years and is now doing well at 18 years of age. Additionally, one patient presented with a simultaneous infection with Klebsiella and Acinetobacter, and one with condyloma caused by human papilloma virus. Molecular analysis revealed four previously described CD40L mutations, two novel missense mutations (c.433 T > G and c.476 G > C) resulting in the absence of CD40L protein expression by activated CD4(+) cells and one novel insertion (c.484_485insAA) within the TNFH domain leading to a frame shift and premature stop codon. These observations demonstrated that the susceptibility to fungal infections in X-HIGM extends beyond those typically associated with X-HIGM (P. jiroveci and C. albicans) and that these patients need to be monitored for those pathogens.

Dendritic cells from X-linked hyper-IgM patients present impaired responses to Candida albicans and Paracoccidioides brasiliensis

BACKGROUND

Patients with X-linked hyper-IgM syndrome (X-HIGM) due to CD40 ligand (CD40L) mutations are susceptible to fungal pathogens; however, the underlying susceptibility mechanisms remain poorly understood.

OBJECTIVE

To determine whether monocyte-derived dendritic cells (DCs) from patients with X-HIGM exhibit normal responses to fungal pathogens.

METHODS

DCs from patients and controls were evaluated for the expression of costimulatory (CD80 and CD86) and MHC class II molecules and for their ability to produce IL-12 and IL-10 in response to Candida albicans and Paracoccidioides brasiliensis. We also evaluated the ability of C albicans- and P brasiliensis-pulsed mature DCs to induce autologous T-cell proliferation, generation of T helper (T(H)) 17 cells, and production of IFN-γ, TGF-β, IL-4, IL-5, and IL-17.

RESULTS

Immature DCs from patients with X-HIGM showed reduced expression of CD80, CD86, and HLA-DR, which could be reversed by exogenous trimeric soluble CD40L. Most important, mature DCs from patients with X-HIGM differentiated by coculturing DCs with fungi secreted minimal amounts of IL-12 but substantial amounts of IL-10 compared with mature DCs from normal individuals. Coculture of mature DCs from X-HIGM patients with autologous T cells led to low IFN-γ production, whereas IL-4 and IL-5 production was increased. T-cell proliferation and IL-17 secretion were normal. Finally, in vitro incubation with soluble CD40L reversed the decreased IL-12 production and the skewed T(H)2 pattern response.

CONCLUSION

Absence of CD40L during monocyte/DC differentiation leads to functional DC abnormalities, which may contribute to the susceptibility to fungal infections in patients with X-HIGM.

HOIL-1L interacting protein (HOIP) is essential for CD40 signaling

CD40 is a cell surface receptor important in the activation of antigen-presenting cells during immune responses. In macrophages and dendritic cells, engagement of CD40 by its ligand CD154 provides signals critical for anti-microbial and T cell-mediated immune responses, respectively. In B cells, CD40 signaling has a major role in regulating cell proliferation, antibody production, and memory B cell development. CD40 engagement results in the formation of a receptor-associated complex that mediates activation of NF-κB, stress-activated protein kinases, and other signaling molecules. However, the mechanisms that link CD40 to these signaling events have been only partially characterized. Known components of the CD40 signaling complex include members of the TNF receptor-associated factor (TRAF) family of proteins. We previously showed that the TRAF family member TRAF2 mediates recruitment of HOIL-1L-interacting protein (HOIP) to the cytoplasmic domain of CD40, suggesting that HOIP has a role in the CD40 signaling pathway. To determine the role of HOIP in CD40 signaling, we used somatic cell gene targeting to generate mouse B cell lines deficient in HOIP. We found that the CD40-induced upregulation of CD80 and activation of germline immunoglobulin epsilon transcription were defective in HOIP-deficient cells. We also found that the CD40-mediated activation of NF-κB and c-Jun kinase was impaired. Recruitment of IκB kinase proteins to the CD40 signaling complex was undetectable in HOIP-deficient cells, potentially explaining the defect in NF-κB activation. Restoration of HOIP expression reversed the defects in cellular activation and signaling. These results reveal HOIP as a key component of the CD40 signaling pathway.

Toll-like receptor 9, transmembrane activator and calcium-modulating cyclophilin ligand interactor, and CD40 synergize in causing B-cell activation

BACKGROUND

B cells receive activating signals from T cells through CD40, from microbial DNA through Toll-like receptor (TLR) 9, and from dendritic cells through transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI). TLR9 and CD40 ligation augment TACI-driven B-cell activation, but only the mechanism of synergy between CD40 and TACI has been explored. Synergy between CD40 and TLR9 in B-cell activation is controversial.

OBJECTIVE

We sought to examine the mechanisms by which TLR9 modulates CD40- and TACI-mediated activation of B cells and to determine whether all 3 receptors synergize to activate B cells.

METHODS

Naive murine B cells and human PBMCs were stimulated with combinations of anti-CD40, CpG, and a proliferation inducing ligand in the presence of IL-4. Proliferation was measured by means of tritiated thymidine incorporation. Immunoglobulin production was measured by means of ELISA. Class-switch recombination (CSR) was examined by measuring mRNA for germline transcripts, activation-induced cytidine deaminase (AICDA), and mature immunoglobulin transcripts. Plasma cell differentiation was examined by using syndecan-1/CD138 staining and mRNA expression of B lymphocyte-induced maturation protein 1 (Blimp-1).

RESULTS

TLR9 synergized with CD40 and TACI in driving CSR and inducing IgG(1) and IgE secretion by naive murine B cells and synergized with TACI in driving B-cell proliferation and plasma cell differentiation. All 3 receptors synergized together in driving murine B-cell proliferation, CSR, plasma cell differentiation, and IgG(1) and IgE secretion. TLR9 synergized with CD40 and TACI in driving IgG secretion in IL-4-stimulated human B cells.

CONCLUSION

Signals from TLR9, TACI, and CD40 are integrated to promote B-cell activation and differentiation.