hyper-IgM Syndrome Research Articles

Mechanotransduction governs CD40 function and underlies X-linked hyper-IgM syndrome.

B cell maturation depends on cognate interactions between the T and B cells. Upon interaction with CD40 ligand (CD40L) on T cells, CD40 delivers costimulatory signals alongside B cell antigen receptor (BCR) signaling to regulate affinity maturation and antibody class switch. Mutations affecting CD40-CD40L interactions cause abnormal antibody responses in immunodeficiencies known as X-linked hyper-IgM syndrome (X-HIgM). Here, we study the CD40-mediated mechanotransduction in B cells, which likely occurs during their physical contacts with T cells. We found that CD40 forms catch bond with CD40L that lasts longer at larger forces, both B and T cells exert tension on CD40-CD40L bonds, and force enhances CD40 signaling and antibody class switch. X-HIgM CD40L mutations impair catch bond formation, suppress endogenous tension, and reduce force-enhanced CD40 signaling, leading to deficiencies in antibody class switch. Our findings highlight the role of mechanotransduction in CD40 function and provide insights into the mechanisms underlying X-HIgM syndrome.

Immunoglobulin class-switch recombination: Mechanism, regulation, and related diseases.

Maturation of the secondary antibody repertoire requires class-switch recombination (CSR), which switches IgM to other immunoglobulins (Igs), and somatic hypermutation, which promotes the production of high-affinity antibodies. Following immune response or infection within the body, activation of T cell-dependent and T cell-independent antigens triggers the activation of activation-induced cytidine deaminase, initiating the CSR process. CSR has the capacity to modify the functional properties of antibodies, thereby contributing to the adaptive immune response in the organism. Ig CSR defects, characterized by an abnormal relative frequency of Ig isotypes, represent a rare form of primary immunodeficiency. Elucidating the molecular basis of Ig diversification is essential for a better understanding of diseases related to Ig CSR defects and could provide clues for clinical diagnosis and therapeutic approaches. Here, we review the most recent insights on the diversification of five Ig isotypes and choose several classic diseases, including hyper-IgM syndrome, Waldenström macroglobulinemia, hyper-IgD syndrome, selective IgA deficiency, hyper-IgE syndrome, multiple myeloma, and Burkitt lymphoma, to illustrate the mechanism of Ig CSR deficiency. The investigation into the underlying mechanism of Ig CSR holds significant potential for the advancement of increasingly precise diagnostic and therapeutic approaches.

DNA-PK inhibition enhances gene editing efficiency in HSPCs for CRISPR-based treatment of X-linked hyper IgM syndrome

DNA-PK inhibition enhances gene editing efficiency in HSPCs for CRISPR-based treatment of X-linked hyper IgM syndrome

119 Novel CD40 Genetic Variants in an Infant with Hyper-IgM Syndrome and Parental CD40 analysis

119 Novel CD40 Genetic Variants in an Infant with Hyper-IgM Syndrome and Parental CD40 analysis

Dual novel variants in CD40 leading to hyper IgM syndrome: a case report of a school-aged female with new-onset recurrent pneumonia

Introduction: Hyper IgM (HIGM) syndrome is an inborn error of immunity (IEI) that occurs due to defects in immunoglobulin class switch recombination (Ig-CSR). HIGM syndrome typically presents with recurrent infections in early childhood, and is often characterized on investigation with decreased IgG, IgA, and IgE titres, alongside normal or elevated IgM. A common cause of HIGM syndrome is a disruption to the CD40-CD40 ligand (CD40L) interaction that triggers Ig-CSR, of which variants in CD40 are much rarer than those in CD40L. We present a case of an 11-year-old female with HIGM syndrome caused by two novel variants of in the CD40 gene. Aim: To describe a case report of an eleven-year-old female with HIGM syndrome presenting with recurrent pneumonia. Methods: Data was collected retrospectively from the patient’s medical records. Laboratory investigations included quantitative immunoglobulins, quantitative B and T cell subsets, genetic testing using a primary immunodeficiency panel, and a functional assay for CD40 expression. Results: The proband is an 11-year-old female, who presented with recurrent pneumonia, otitis, and septic arthritis. Investigations revealed neutropenia, low IgA, elevated IgM and normal IgG, along with absent vaccine responses. She was identified to harbour two novel variants in CD40: an intronic variant c.52-13A>G p.(?) and a missense variant c.466T>C p.(Ser156Pro). Functional assay indicated low expression of CD40 compared to healthy control, confirming the diagnosis of CD40 deficiency. Conclusion: Class switch defects, such as CD40 deficiency, are rare but significant diagnoses within the spectrum of IEI. This case demonstrates that despite the absence of some clinical red flags for immunodeficiency in infancy, IEIs remain an important consideration in pediatric patients regardless of age. Increasing clinical awareness of IEI will lead to earlier diagnoses, initiation of appropriate treatment, and prevention of potential complications. Statement of novelty: We describe a patient with a late presentation of hyper IgM syndrome due to two novel variants in the CD40 gene, thus expanding the spectrum of CD40 gene variants.

Antibody Response Before and After the Booster Dose of Inactivated Corona Vaccine in Antibody Deficient Patients.

Patients with inborn errors of immunity (IEI) are among the high-risk groups regarding COVID-19. Receiving booster doses (third and fourth) in addition to the standard doses is recommended in these patients. This study investigated the antibody response before and after a booster dose of Sinopharm vaccine in IEI patients. Thirty patients (>12 years) with antibody deficiencies, referred to Imam Khomeini Hospital and Children's Medical Center in Tehran, were enrolled in this prospective cross-sectional study. All patients were fully vaccinated with the BBIBP-CorV vaccine (2 doses of Sinopharm). Initial measurements of anti-receptor-binding domain (anti-RBD) and anti-nucleocapsid (anti-N) IgG antibody responses were conducted by enzyme-linked immunosorbent assay (ELISA). Subsequently, all patients received a booster dose of the vaccine. Four to six weeks after booster injection, the levels of antibodies were re-evaluated. Twenty patients with common variable immunodeficiency (CVID), 7 cases with agammaglobulinemia and 3 patients with hyper IgM syndrome were studied. Anti-RBD IgG and anti-N IgG antibodies increased in all patients after the booster. Our results indicated the need of receiving booster doses of the COVID-19 vaccine in patients with antibody deficiencies, even for enhancing humoral immune response specially in patients with CVID.

A novel hemizygous CD40L mutation of X-linked hyper IgM syndromes and compound heterozygous DOCK8 mutations of hyper IgE syndromes in two Chinese families.

X-linked hyper-immunoglobulin M (X-HIGM) syndrome and autosomal recessive hyper-immunoglobulin E syndrome (HIES) are rare inborn errors of immunity characterized by recurrent infections due to immune system impairment. In this study, we identified a novel hemizygous CD40 ligand (CD40L) mutation and compound heterozygous dedicator of cytokinesis-8 (DOCK8) mutations in two Han Chinese families with X-HIGM and HIES, respectively. We aimed to investigate the association between their genotypes and phenotypes. Genomic DNA was extracted from peripheral blood samples obtained from the families. Whole exome sequencing and Sanger sequencing were performed to identify and verify pathogenic variants in the two families. Clinical analyses of the probands were also performed. A novel hemizygous mutation of CD40L in exon 2 (c.257delA) was identified in the first proband, resulting in the substitution of glycine with glutamic acid at codon 86 of the protein. This leads to premature termination of translation at downstream codon 9 (p.E86Gfs*9). Sanger sequencing confirmed that the variant was inherited from the mother. The second proband carried two novel compound heterozygous mutations in DOCK8: one at exon 14 (c.1546C > G) inherited from the father, and the other at intron 41 (c.5355 + 6C > T; splicing) inherited from the mother. This study enhances our understanding of the pathogenetic mutation spectrum of CD40L and DOCK8 genes, facilitating the prenatal diagnosis of X-HIGM and HIES and enabling timely treatment of patients.

A Novel Heterozygous Variant in AICDA Impairs Ig Class Switching and Somatic Hypermutation in Human B Cells and is Associated with Autosomal Dominant HIGM2 Syndrome

B cells and their secreted antibodies are fundamental for host-defense against pathogens. The generation of high-affinity class switched antibodies results from both somatic hypermutation (SHM) of the immunoglobulin (Ig) variable region genes of the B-cell receptor and class switch recombination (CSR) which alters the Ig heavy chain constant region. Both of these processes are initiated by the enzyme activation-induced cytidine deaminase (AID), encoded by AICDA. Deleterious variants in AICDA are causal of hyper-IgM syndrome type 2 (HIGM2), a B-cell intrinsic primary immunodeficiency characterised by recurrent infections and low serum IgG and IgA levels. Biallelic variants affecting exons 2, 3 or 4 of AICDA have been identified that impair both CSR and SHM in patients with autosomal recessive HIGM2. Interestingly, B cells from patients with autosomal dominant HIGM2, caused by heterozygous variants (V186X, R190X) located in AICDA exon 5 encoding the nuclear export signal (NES) domain, show abolished CSR but variable SHM. We herein report the immunological and functional phenotype of two related patients presenting with common variable immunodeficiency who were found to have a novel heterozygous variant in AICDA (L189X). This variant led to a truncated AID protein lacking the last 10 amino acids of the NES at the C-terminal domain. Interestingly, patients’ B cells carrying the L189X variant exhibited not only greatly impaired CSR but also SHM in vivo, as well as CSR and production of IgG and IgA in vitro. Our findings demonstrate that the NES domain of AID can be essential for SHM, as well as for CSR, thereby refining the correlation between AICDA genotype and SHM phenotype as well as broadening our understanding of the pathophysiology of HIGM disorders.

Gene regulation in inborn errors of immunity: Implications for gene therapy design and efficacy.

Inborn errors of immunity (IEI) present a unique paradigm in the realm of gene therapy, emphasizing the need for precision in therapeutic design. As gene therapy transitions from broad-spectrum gene addition to careful modification of specific genes, the enduring safety and effectiveness of these therapies in clinical settings have become crucial. This review discusses the significance of IEIs as foundational models for pioneering and refining precision medicine. We explore the capabilities of gene addition and gene correction platforms in modifying the DNA sequence of primary cells tailored for IEIs. The review uses four specific IEIs to highlight key issues in gene therapy strategies: X-linked agammaglobulinemia (XLA), X-linked chronic granulomatous disease (X-CGD), X-linked hyper IgM syndrome (XHIGM), and immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX). We detail the regulatory intricacies and therapeutic innovations for each disorder, incorporating insights from relevant clinical trials. For most IEIs, regulated expression is a vital aspect of the underlying biology, and we discuss the importance of endogenous regulation in developing gene therapy strategies.

Prolonged pediatric intensive care unit (PICU) admission, challenges in diagnosis and treatment in a child with hyper IgM syndrome in a tertiary hospital in Tanzania: a case report

Prolonged pediatric intensive care unit (PICU) admission, challenges in diagnosis and treatment in a child with hyper IgM syndrome in a tertiary hospital in Tanzania: a case report

Use of Metagenomic Next-Generation Sequencing in the Identification of Pneumocystis Jiroveci Pneumonia in a Previously Healthy Infant Diagnosed With X-Linked Hyper-IgM Syndrome

This case describes a four-month-old male who was admitted to the pediatric intensive care unit for acute respiratory failure in the setting of a co-infection requiring increased ventilatory support. Immunodeficiency workup demonstrated poor vaccination response and low immunoglobulin titers. mNGS via Karius® test was positive for Pneumocystis jiroveci (PJP), Parvovirus, and Bocavirus. The patient was successfully treated with trimethoprim-sulfamethoxazole and prednisone. Genetic workup via Invitae panel confirmed that the patient had X-linked Hyper-IgM Syndrome. Use of mNGS can help with early identification of pathogens that conventional testing does not detect, even in patients not already identified as immunocompromised.

Late diagnosis of X-linked hyper-IgM syndrome presenting as community-acquired Pseudomonas aeruginosa pneumonia-related septic shock.

Late diagnosis of X-linked hyper-IgM syndrome presenting as community-acquired Pseudomonas aeruginosa pneumonia-related septic shock.

Two cases of successful sirolimus treatment for patients with activated phosphoinositide 3-kinase δ syndrome 1

BackgroundActivated phosphoinositide3-kinase (PI3K) δ syndrome 1 (APDS1) is a novel inborn errors of immunity (IEIs) caused by heterozygous gain of function mutations in PI3Kδ catalytic p110δ (PIK3CD). APDS1 has a spectrum of clinical manifestations. Recurrent respiratory infections, lymphoproliferation, hepatosplenomegaly, hyper-IgM syndrome and autoimmunity are the common symptoms of this disease.Case PresentationPatient 1 presented with recurrent respiratory infections, hepatosplenomegaly and hyper-IgM syndrome. Patient 2 developed early onset systemic lupus erythematosus (SLE)-like disease with resistant thrombocytopenia. c.3061 G > A and c.2314G > A variants in the PIK3CD gene were detected by whole exome sequencing in two patients respectively. c.2314G > A variant in PIK3CD gene of patient 2 is a newly report. After genetic diagnosis, two patients received sirolimus treatment and sirolimus alleviated clinical manifestations, including hepatosplenomegaly in patient 1 and thrombocytopenia in patient 2.ConclusionGenetics diagnosis should be considered in patients with complicated clinical manifestations with no or insufficient response to the conventional therapies. If whole exome sequencing suggests a variant in PIK3CD gene, sirolimus may relieve hepatosplenomegaly and resistant thrombocytopenia. This is the first report of c.2314G > A variant in PIK3CD gene.

Advanced computational analysis of CD40LG variants in atypical X-linked hyper-IgM syndrome

X-Linked Hyper-IgM Syndrome is caused by pathogenic variants in CD40LG. Three patients with atypical clinical and immunological features were identified with variants in CD40LG requiring further characterization. Flow cytometry was used to evaluate CD40L protein expression and binding capacity to a surrogate receptor, CD40-muIg. Though functional anomalies were observed, there was still a lack of clarity regarding the underlying mechanism. We developed structural models for wild-type and the three variants of CD40L protein observed in these patients (p. Lys143Asn, Leu225Ser and Met36Arg) to evaluate structural alterations by molecular mechanic calculations, and assess protein movement by molecular dynamic simulations. These studies demonstrate that functional analysis of variants of unknown significance in CD40LG can be supplemented by advanced computational analysis in atypical clinical contexts. These studies in combination identify the deleterious effects of these variants and potential mechanisms for protein dysfunction.

Assessment of Enterovirus Excretion and Identification of VDPVs in Patients with Primary Immunodeficiency in India: Outcome of ICMR-WHO Collaborative Study Phase-I.

The emergence of vaccine-derived polioviruses (VDPVs) in patients with Primary Immunodeficiency (PID) is a threat to the polio-eradication program. In a first of its kind pilot study for successful screening and identification of VDPV excretion among patients with PID in India, enteroviruses were assessed in stool specimens of 154 PID patients across India in a period of two years. A total of 21.42% of patients were tested positive for enteroviruses, 2.59% tested positive for polioviruses (PV), whereas 18.83% of patients were positive for non-polio enteroviruses (NPEV). A male child of 3 years and 6 months of age diagnosed with Hyper IgM syndrome was detected positive for type1 VDPV (iVDPV1) with 1.6% nucleotide divergence from the parent Sabin strain. E21 (19.4%), E14 (9%), E11 (9%), E16 (7.5%), and CVA2 (7.5%) were the five most frequently observed NPEV types in PID patients. Patients with combined immunodeficiency were at a higher risk for enterovirus infection as compared to antibody deficiency. The high susceptibility of PID patients to enterovirus infection emphasizes the need for enhanced surveillance of these patients until the use of OPV is stopped. The expansion of PID surveillance and integration with a national program will facilitate early detection and follow-up of iVDPV excretion to mitigate the risk for iVDPV spread.

Elevated levels of enteric IgA in an unimmunised mouse model of Hyper IgM syndrome derived from gut-associated secondary lymph organs even in the absence of germinal centres.

Patients with Human Hyper IgM syndromes (HIGM) developed pulmonary and gastrointestinal infections since infancy and most patients have mutations in the CD40 ligand (CD40L) gene. Most HIGM patients compared to healthy subjects have higher/similar IgM and lower IgG, and IgA serum concentrations but gut antibody concentrations are unknown. CD40L on activated T-cells interacts with CD40 on B-cells, essential for the formation of germinal centres (GCs) inside secondary lymphoid organs (SLOs), where high-affinity antibodies, long-lived antibody-secreting plasma cells, and memory B-cells, are produced. C57BL6-CD40 ligand deficient mice (C57BL6-cd40l -/-), are a model of HIGM, because serum immunoglobulin concentrations parallel levels observed in HIGM patients and have higher faecal IgA concentrations. In mice, TGFβ and other cytokines induce IgA production. To compare and evaluate B-cell populations and IgA-producing plasma cells in peritoneal lavage, non-gut-associated SLOs, spleen/inguinal lymph nodes (ILN), and gut-associated SLOs, mesenteric lymph nodes (MLN)/Peyer´s patches (PP) of unimmunised C57BL6-cd40l -/- and C57BL6-wild-type (WT)mice. Peritoneal lavages, spleens, ILN, MLN, and PP from 8-10 weeks old C57BL6-cd40l -/- and WT mice, were obtained. Organ cryosections were analysed by immunofluorescence and B-cell populations and IgA-positive plasma cell suspensions by flow cytometry. In unimmunised WT mice, GCs were only observed in the gut-associated SLOs, but GCs were absent in all C57BL6-cd40l -/- SLOs. PP and MLN of C57BL6-cd40l -/- mice exhibited a significantly higher number of IgA-producing cells than WT mice. In the spleen and ILN of C57BL6-cd40l- /- mice IgA-producing cells significantly decreased, while IgM-positive plasma cells increased. C57BL6-cd40l -/- B-1 cells were more abundant in all analysed SLOs, whereas in WT mice most B-1 cells were contained within the peritoneal cavity. C57BL6-cd40l -/- B-cells in MLN expressed a higher TGFβ receptor-1 than WT mice. Mouse strains small intestine microvilli (MV), have a similar frequency of IgA-positive cells. Together our results confirm the role of PP and MLN as gut inductive sites, whose characteristic features are to initiate an IgA preferential immune response production in these anatomical sites even in the absence of GCs. IgA antibodies play a pivotal role in neutralising, eliminating, and regulating potential pathogens and microorganisms in the gut.

A Case Report of Hyper-IgM Syndrome Patient with Normal Serum IgA Level

Hyper IgM syndromes are a group of disorders characterized by defective T and B cell interactions resulting in the lack of Immunoglobulin class switching. The most common hyper IgM syndrome is CD40 ligand (CD40L) deficiency. Patients with CD40L deficiency present with recurrent infection, neutropenia, and autoimmunity. These patients typically have absent serum IgA and IgG due to the class switch defect. Here we present a case of CD40L deficiency who presented with oral ulcers, failure to thrive, and recurrent fever. His laboratory evaluation was notable for intermittent neutropenia, elevated IgM (397mg/dl), normal IgA (78mg/dl) and low IgG (51mg/dl). Antibody responses to tetanus and measles were undetectable despite full vaccination. Whole exome sequencing showed a likely pathologic variant in CD40LG (c.674 T>C, p.L225S). This case highlights the importance of considering the diagnosis of hyper IgM syndrome in the appropriate clinical setting, even if the patient has a normal serum IgA level.

CD40LG-associated X-linked Hyper-IgM Syndrome (XHIGM) with pulmonary alveolar proteinosis: a case report

BackgroundD40LG-associated X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis has rarely been reported, and its genotype-phenotypic correlation remains elusive.Case presentationWe describe a five-month-old boy with CD40LG mutation (c.516T > A, p.Tyr172Ter) X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis as the first manifestation. The patient completely recovered after immunotherapy and allogeneic hematopoietic stem cell transplantation. In addition, four previously reported patients with CD40LG mutation with pulmonary alveolar proteinosis were also analyzed. All of these patients presented with early onset of pulmonary infections and a good response to immunotherapy. The structural model of CD40LG indicated that all mutations caused the X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis to be located within the tumor necrosis factor homology domain.ConclusionsA case was presented, and the characteristics of four cases of CD40LG-associated X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis were summarized. The variant locations may explain the phenotypic heterogeneity of patients with the CD40LG mutation.

AIDμS double knockout mice but not AID single knockout mice are highly susceptible to PneumocystisInfection

Abstract Pneumocystispneumonia can be a life-threatening disease to individuals who are immunocompromised due to infection, such as HIV, receiving immunotherapy drugs including corticosteroids or due to genetic defect such as hyper IgM syndrome. B cells are important to the defense and clearance of Pneumocystisinfection; however, the exact role has yet to be elucidated. Prior studies have demonstrated that B cell antigen presentation and priming of CD4 +T cells plays a major role in Pneumocystisclearance, while passive transfer of immune serum can prevent Pneumocystisinfection in mice. To better understand the B cell role in control and clearance of Pneumocystisinfection, using a natural exposure model, we compared the kinetics of Pneumocystis murinainfection in activation-induced cytidine deaminase (AID −/−), AIDμS −/−double knockout, and wild-type C57BL/6 mice. By 5 – 6 weeks post initial exposure all three murine strains were infected with Pneumocystis murina, detected by qPCR of the single copy gene dihydrofolate reductase (DHFR). However, after 10 weeks of infection only the AIDμS −/−double knockout mice continued to have high levels of Pneumocystisinfection. These data suggests that deficiency of B cells to class switch, such as in the AID −/−strain, is not in itself enough to confer increased susceptibility to Pneumocystis. However, in combination with μS deficiency, which inhibits the secretion of antibodies, it is enough to debilitate the immune response resulting in uncontrolled Pneumocystisinfection. Intramural Research Program of the NIH Clinical Center

CD40LG genotype does not correlate with clinical phenotype in X-linked hyper-IgM syndrome

IntroductionCD40 ligand is expressed on follicular helper T cells and binds to CD40 on B cells and antigen presenting cells (APC). The CD40L-CD40 interaction is integral to germinal center formation, immunoglobulin class switching and affinity maturation, as well as APC mediated cytokine secretion required for an effective T cell response. Patients with mutations in the CD40LG gene develop X-linked Hyper-IgM (XHIGM) syndrome characterized by recurrent sinopulmonary, opportunistic infections, liver disease and malignancy. Early studies identified no clear genotype/phenotype correlation; but a milder phenotype has been reported associated with certain variants such as T254M. PurposeTo understand if specific genetic mutations in CD40LG correlate with disease severity we developed a clinical severity scoring system and retrospectively analyzed the relationship between severity and genotype in 109 individuals with XHIGM. ResultsThe majority of reported mutations were missense (41%), splice site (27%), nonsense (13%) or deletion (13%) mutations. There was not a statistically significant difference in severity or survival among mutation type groups. We identified 10 unrelated individuals with amino acid substitution T254M and found a range of clinical phenotypes from mild disease with late onset to early manifestations, liver disease and death due to cholangiocarcinoma. ConclusionOur data confirms the lack of genotype/phenotype correlation in XHIGM and suggest the need to develop a clinical scoring system that would allow for better understanding of an individual prognostic outcome.