proteins

2026-07-14 | Relevance of a Computational Deep-Dive to Characterize the Molecular Biology of a Novel Cd40l Variant

CD40L deficiency is a well-described inborn error of immunity (IEI). The disease is characterized immunologically by impaired class-switching and T cell costimulation. A male infant presented at 8 months of age with recurrent cellulitis. At 11 months, he was admitted for prolonged fever and leukopenia with vomiting and watery diarrhea, periorbital edema, back abscess, increased sIL2R at 50,598 pg/mL (<14,491), and normal CXCL9 at 22 pg/mL with mild to modest increases in IL-18 at 694 pg/mL (<185.4), IL-6 at 226.4 pg/mL (<10), serum amyloid A (SAA) at 1,413 mcg/mL (<373.8), IL-8 at 196 (<10), and IL-10 at 101pg/mL (<10). His IgG and IgA were low at <30 and <10 mg/dL, respectively. He developed Pseudomonas sepsis, palatal ulceration, jejunal perforation requiring repair, Candida peritonitis, persistent neutropenia, CMV, and Parechovirus viremia. Along with the hypogammaglobulinemia, class-switched memory B cells were decreased for age. Flow cytometry was performed for CD40L expression on activated CD4+ T cells along with functional evaluation of ligand binding to a soluble form of the receptor (CD40), using CD40-muIg. There was significantly diminished CD40L expression with essentially absent binding to the receptor. Genetic testing confirmed a diagnosis of CD40L deficiency due to a hemizygous variant in CD40LG, c.674T>C; p.Leu225Ser (NM_000074.2). We had previously evaluated a 4-year-old male with intermittent, non-bloody diarrhea, pneumonia, hypogammaglobulinemia, and significant neutropenia, and identified this novel variant, now also observed in this infant. We utilized advanced computational tools to evaluate the molecular impact of this variant on the structure and function of CD40L. The Leu225Ser variant is located within the trimerization interface of CD40L. Molecular modeling, mutagenesis alanine scanning, and molecular dynamic simulations revealed that the variant causes loss of critical intramolecular time-dependent interactions between hydrophobic molecules that would typically facilitate trimerization of wild-type CD40L for optimal interaction with the CD40 receptor. This analysis of the Leu225Ser variant revealed the molecular basis of the decreased CD40L protein expression (loss of contact to form trimers) and impaired CD40 binding (loss of intramolecular bonds affecting folding and impaired interaction at the trimerization interface). The patient also had immune paralysis due to decreased MHC class II (HLA-DR) expression on CD14+ monocytes, a result of a compensatory anti-inflammatory response syndrome (CARS). Assessment of neutrophil activation and granule markers (CD66b, lactoferrin, myeloperoxidase [MPO], and elastase) revealed low-normal CD66b and lactoferrin with slightly increased MPO and elastase, suggesting a complex and dysfunctional neutrophil response rather than simple activation or deactivation. This phenotype is consistent with the known pathology of CD40L deficiency, in which neutrophils are defective in their ability to respond effectively to infection, leading to chronic inflammation and tissue damage despite persistent signs of granule release. Treatment with rIFNg has been shown to reverse neutrophil dysfunction in X-linked hyper-IgM syndrome (XHIGM) but also restore HLA-DR expression on monocytes and reverse immune paralysis. He is currently being evaluated for hematopoietic cell transplantation (HCT). This case exemplifies the relevance of utilizing a variety of strategies to evaluate novel variants in IEI genes. Further, molecular and computational studies permitted an improved understanding of the impact of the Leu225Ser variant on CD40L protein expression and function.

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2026-02-25 | Teduglutide in Enterocolitis Secondary to Graft-Versus-Host Disease Post-Bone Transplant: Case Report

Background: Gastrointestinal graft-versus-host disease (GVHD) is one of the most severe complications of hematopoietic stem cell transplantation (HSCT), particularly in pediatric patients. It is frequently associated with treatment refractoriness and prolonged dependence on parenteral nutrition. Teduglutide, a GLP-2 analog, has shown promise in intestinal mucosal regeneration, but its use in GVHD remains limited. This case report describes the clinical experience with teduglutide in a pediatric patient with refractory GVHD-associated enterocolitis. Methods: We report the case of a 3-year-old child with primary immunodeficiency (Hyper-IgM Syndrome – CD40L deficiency) who underwent haploidentical HSCT and subsequently developed grade III gastrointestinal GVHD. The patient presented with severe chronic diarrhea, rectal prolapse, extensive intestinal inflammation, and nutritional failure despite standard immunosuppressive therapy. Teduglutide was initiated on a compassionate basis at a dose of 0.9 mg subcutaneously once daily. Results: Following initiation of teduglutide, the patient showed sustained improvement in stool consistency and frequency, reduced signs of intestinal inflammation, nutritional stabilization, and resolution of rectal prolapse episodes. Clinical response was maintained until the patient's death due to pulmonary infectious complications unrelated to gastrointestinal involvement. Conclusions: The positive intestinal response observed in this case supports the potential role of teduglutide as an adjunctive therapy for mucosal recovery in refractory GI-GVHD. Although encouraging, its use in this setting warrants further investigation through controlled studies, particularly in pediatric populations.

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2025-11-20 | Coexistence of familial hemophagocytic lymphohistiocytosis type 3 and X-linked hyper IgM syndrome in a child

Background: Hemophagocytic lymphohistiocytosis (HLH) is a severe, life-threatening hyperinflammatory syndrome characterized by excessive activation of the immune system, leading to symptoms such as fever, multilineage cytopenia, coagulopathy, and multi-organ failure, with a high risk of mortality. Its non-specific clinical presentation often poses a diagnostic challenge, especially when the line between primary and secondary HLH is blurred, as secondary triggers, such as infections, can unmask an underlying genetic condition. The incidence of HLH is elevated in patients with inborn errors of immunity (IEI). Case report: We report the case of a 9-month-old male infant with classic HLH, including prolonged fever, hepatosplenomegaly, thrombocytopenia, elevated ferritin, and hemophagocytosis in the bone marrow aspirate. Notably, the patient also had an opportunistic Aspergillus infection, which is a hallmark of severe immunodeficiency. Genetic analysis revealed a rare co-occurrence of two pathogenic variants: a compound heterozygous c.859-3C>T mutation in UNC13D (causing familial hemophagocytic lymphohistiocytosis type 3) and a recessive c.158_161del mutation in CD40LG (causing hyper-IgM syndrome). The infant was diagnosed with HLH on the background of hyper-IgM syndrome based on HLH-2004 criteria and responded well to a combined treatment of chemotherapy and immunoglobulin replacement therapy. Conclusions: This case highlights the crucial role of comprehensive IEI screening in patients with HLH, particularly those with a history of recurrent or opportunistic infections, to facilitate accurate diagnosis and optimize treatment strategies.

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2024-11-15 | 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.

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2023-07-31 | CD40L Activates Platelet Integrin αIIbβ3 by Binding to the Allosteric Site (Site 2) in a KGD-Independent Manner and HIGM1 Mutations Are Clustered in the Integrin-Binding Sites of CD40L

CD40L is expressed in activated T cells, and it plays a major role in immune response and is a major therapeutic target for inflammation. High IgM syndrome type 1 (HIGM1) is a congenital functional defect in CD40L/CD40 signaling due to defective CD40L. CD40L is also stored in platelet granules and transported to the surface upon platelet activation. Platelet integrin αIIbβ3 is known to bind to fibrinogen and activation of αIIbβ3 is a key event that triggers platelet aggregation. Also, the KGD motif is critical for αIIbβ3 binding and the interaction stabilizes thrombus. Previous studies showed that CD40L binds to and activates integrins αvβ3 and α5β1 and that HIGM1 mutations are clustered in the integrin-binding sites. However, the specifics of CD40L binding to αIIbβ3 were unclear. Here, we show that CD40L binds to αIIbβ3 in a KGD-independent manner using CD40L that lacks the KGD motif. Two HIGM1 mutants, S128E/E129G and L155P, reduced the binding of CD40L to the classical ligand-binding site (site 1) of αIIbβ3, indicating that αIIbβ3 binds to the outer surface of CD40L trimer. Also, CD40L bound to the allosteric site (site 2) of αIIbβ3 and allosterically activated αIIbβ3 without inside-out signaling. Two HIMG1 mutants, K143T and G144E, on the surface of trimeric CD40L suppressed CD40L-induced αIIbβ3 activation. These findings suggest that CD40L binds to αIIbβ3 in a manner different from that of αvβ3 and α5β1 and induces αIIbβ3 activation. HIGM1 mutations are clustered in αIIbβ3 binding sites in CD40L and are predicted to suppress thrombus formation and immune responses through αIIbβ3.

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cell therapies

2026-08-11 | Pulmonary alveolar proteinosis and Pneumocystis jirovecii infection in an infant with hyper-IgM syndrome caused by a novel CD40LG variant: a case report

Background Pulmonary alveolar proteinosis (PAP) is a rare interstitial lung disease. While autoimmunity is the leading cause of PAP in adults, the majority of pediatric cases occur secondary to immunodeficiency and opportunistic infections. Secondary PAP associated with CD40 ligand (CD40L) deficiency is extremely rare, and the underlying pathophysiology remains poorly understood. Case presentation We report the case of a 4-month-old boy admitted due to failure to thrive and severe hypoxemic respiratory failure. Chest computed tomography demonstrated diffuse ground-glass opacities with interlobular septal thickening. Bronchoalveolar lavage yielded clear fluid containing Periodic acid-Schiff-positive material consistent with PAP, and polymerase chain reaction was positive for Pneumocystis jirovecii . An immunologic evaluation showed hypogammaglobulinemia (IgG and IgA), a normal IgM level for his age, an absence of class-switched memory B cells, and significantly reduced CD40L expression on activated T lymphocytes. Targeted genetic testing identified a previously unreported hemizygous CD40LG missense variant [c.137T>C, p.(Leu46Pro)]. Integration of the patient’s immunophenotype, an in silico variant evaluation, and segregation data permitted classification of this variant as likely pathogenic, confirming X-linked hyper-IgM syndrome. The patient improved with ventilatory support, high-dose trimethoprim-sulfamethoxazole, and immunoglobulin replacement therapy. Conclusions Early-onset PAP associated with P. jirovecii infection may reveal CD40L deficiency and should prompt evaluation for primary immunodeficiency. An integrated clinico-immunologic assessment coupled with genetic testing is essential to provide a molecular diagnosis, guide management, and prognostication, and to support timely consideration of curative hematopoietic stem cell transplantation.

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2026-05-05 | Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation in X-Linked Hyper IgM Syndrome: A Multicenter Chinese Cohort Study from CCBMT.

X-linked hyper-IgM syndrome (XHIGM) is a rare immunodeficiency for which allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative option, yet large pediatric Chinese datasets are scarce. We retrospectively analyzed 71 boys with genetically confirmed CD40L deficiency who underwent allogeneic HSCT between 2009 and 2020 at eight centers in China. Median age at HSCT was 3 yr (range, 0.6 to 17), with 74.6% transplanted before age 5. Donors were mismatched unrelated (42.3%), matched unrelated (33.8%), matched sibling (18.3%), and haploidentical (5.6%). Peripheral blood was the predominant stem cell source (67.6%), followed by cord blood (31.0%). Myeloablative conditioning was used in 95.8%. Median times to neutrophil and platelet engraftment were 12 and 14 d, respectively. Primary graft failure occurred in 5.6%. Acute GVHD developed in 60.6% (grade III to IV, 11.3%), and chronic GVHD in 25.4% (none-severe). Cytomegalovirus and EBV-DNAemia occurred in 56.3% and 39.4%, respectively; post-transplant lymphoproliferative disorder developed in 4.2%. Other complications included sinusoidal obstruction syndrome and hemorrhagic cystitis (7.0% each). At last follow-up, 9 patients (12.1%) had died, mainly from infections (8.5%). At a median follow-up of 7.8 yr, the estimated 10-yr overall, disease-free, and GVHD-free survival rates were 85.91%, 64.79%, and 77.14%, respectively. Survival was superior in younger patients, those with lower body weight, and well-matched related or unrelated donors. Immune reconstitution showed early NK recovery with progressive T and B cell restoration over 1 yr. These data support HSCT as effective long-term therapy for XHIGM and highlight benefits of early timing and optimal HLA matching.

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2023-10-26 | Case Report: The impact of severe cryptosporidiosis on the gut microbiota of a pediatric patient with CD40L immunodeficiency

Cryptosporidium parvum is a protozoan parasite and one of the leading causes of gastroenteritis in the world, primarily affecting very young children and immunocompromised patients. While infection is usually self-limiting, it can become chronic and even lethal in these vulnerable populations, in whom Cryptosporidium treatments are generally ineffective, due to their acting in concert with a functioning immune system. Here, we describe a case of chronic cryptosporidiosis in a European child with severe CD40L immunodeficiency infected with Cryptosporidium parvum of the IIa20G1 subgenotype, a lineage which has thus far only ever been described in the Middle East. After years of on-off treatment with conventional and non-conventional anti-parasitic drugs failed to clear parasitosis, we performed targeted metagenomics to observe the bacterial composition of the patient’s gut microbiota (GM), and to evaluate fecal microbiota transplantation (FMT) as a potential treatment option. We found that C. parvum infection led to significant shifts in GM bacterial composition in our patient, with consequent shifts in predicted intestinal functional signatures consistent with a state of persistent inflammation. This, combined with the patient’s poor prognosis and increasing parasitic burden despite many rounds of anti-parasitic drug treatments, made the patient a potential candidate for an experimental FMT procedure. Unfortunately, given the many comorbidities that were precipitated by the patient’s immunodeficiency and chronic C. parvum infection, FMT was postponed in favor of more urgently necessary liver and bone marrow transplants. Tragically, after the first liver transplant failed, the patient lost his life before undergoing FMT and a second liver transplant. With this case report, we present the first description of how cryptosporidiosis can shape the gut microbiota of a pediatric patient with severe immunodeficiency. Finally, we discuss how both our results and the current scientific literature suggest that GM modulations, either by probiotics or FMT, can become novel treatment options for chronic Cryptosporidium infection and its consequent complications, especially in those patients who do not respond to the currently available anti-parasitic therapies.

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2023-02-03 | CD40LG-associated X-linked Hyper-IgM Syndrome (XHIGM) with Pulmonary Alveolar Proteinosis: A Case Report

Abstract Background: D40LG -associated X-linked hyper-IgM syndrome with pulmonary alveolar proteinosis has rarely been reported, and its genotype-phenotypic correlation remains elusive. Case Presentation: We 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 proteinosisto be located within the tumor necrosis factor homology domain. Conclusions: A 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.

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2022-06-28 | Mobilization-based chemotherapy-free engraftment of gene-edited human hematopoietic stem cells.

Hematopoietic stem/progenitor cell gene therapy (HSPC-GT) is proving successful to treat several genetic diseases. HSPCs are mobilized, harvested, genetically corrected ex vivo, and infused, after the administration of toxic myeloablative conditioning to deplete the bone marrow (BM) for the modified cells. We show that mobilizers create an opportunity for seamless engraftment of exogenous cells, which effectively outcompete those mobilized, to repopulate the depleted BM. The competitive advantage results from the rescue during ex vivo culture of a detrimental impact of mobilization on HSPCs and can be further enhanced by the transient overexpression of engraftment effectors exploiting optimized mRNA-based delivery. We show the therapeutic efficacy in a mouse model of hyper IgM syndrome and further developed it in human hematochimeric mice, showing its applicability and versatility when coupled with gene transfer and editing strategies. Overall, our findings provide a potentially valuable strategy paving the way to broader and safer use of HSPC-GT.

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antibodies

2026-08-24 | Progressive multifocal leukoencephalopathy in a 15-year-old boy with X-linked hyper-IgM syndrome: a case report

Progressive multifocal leukoencephalopathy (PML) is a rare and potentially fatal infection caused by JC polyomavirus, primarily affecting individuals with impaired cellular immunity. We report a 15-year-old boy with genetically confirmed X-linked hyper-IgM syndrome due to a pathogenic CD40LG variant. Despite regular intravenous immunoglobulin replacement therapy and antimicrobial prophylaxis, he developed concurrent Pneumocystis jirovecii pneumonia and COVID-19. Approximately 2 months after recovery from the pulmonary infections, he developed progressive visual impairment, diplopia, impaired concentration, and mild generalized weakness. Brain magnetic resonance imaging revealed extensive bilateral temporo-parieto-occipital white-matter lesions. Cerebrospinal fluid polymerase chain reaction was positive for JC polyomavirus DNA, confirming the diagnosis of PML; HIV testing was negative. In the absence of an established antiviral therapy, a single intravenous dose of pembrolizumab (80 mg) was administered as an experimental immune-based intervention. Three weeks later, the patient developed rapidly progressive generalized muscle weakness and respiratory failure requiring intensive care and mechanical ventilation. Despite intensive supportive treatment, he subsequently died. The precise cause of this deterioration could not be conclusively established, and a multifactorial process involving progression of PML and treatment-related or critical-illness complications could not be excluded. PML should be considered in patients with X-linked hyper-IgM syndrome who develop new neurological manifestations. Pembrolizumab remains an experimental intervention in this setting, with uncertain efficacy and safety in primary immunodeficiency.

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2026-05-01 | Thriving Without Transplant: A Case of X-Linked Hyper-IgM Syndrome with Near-Normal Quality of Life on IVIG

Introduction Hyper-IgM syndrome (HIGM) is a rare primary immunodeficiency characterized by impaired immunoglobulin class-switch recombination, most commonly due to mutations in the CD40 ligand (CD40L) gene. Affected patients typically present in early childhood with recurrent sinopulmonary infections and are at risk for opportunistic infections, chronic lung disease, and immune dysregulation. Hematopoietic stem cell transplantation (HSCT) is considered curative but carries significant risks. Long-term outcomes with immunoglobulin replacement therapy alone in selected patients remain an area of clinical interest. Case Report We present a male patient with X-linked HIGM (CD40L Thr254Met mutation) diagnosed at age 6 years. He initially developed recurrent otitis media by 1 year of age, followed by recurrent bacterial pneumonias and chronic sinusitis. Notably, he had no history of opportunistic infections. Initial immunologic evaluation revealed elevated IgM (431 mg/dL), markedly low IgG and IgA, and undetectable IgE levels. He was started on intravenous immunoglobulin (IVIG) replacement therapy in 2011, resulting in significant clinical improvement and resolution of recurrent infections. He is currently 21 years of age, his immunoglobulin levels demonstrated therapeutic IgG (1,542 mg/dL), persistently low IgA (<5 mg/dL), and improved IgM (170 mg/dL). Over the subsequent years, he experienced only two mild, self-limited upper respiratory infections and was described by his family as healthier than most peers. He remained compliant with IVIG therapy (30 g every 3 weeks) and reported excellent quality of life. A minor gastrointestinal concern consisting of intermittent passage of small amounts of mucus-like stool with flatus was reported but was infrequent, nonprogressive, and without systemic symptoms. Physical examination was unremarkable. Given his stable clinical course, lack of opportunistic infections, and excellent response to IVIG, HSCT was previously discussed but deferred in favor of continued immunoglobulin replacement. Discussion This case highlights the potential for excellent long-term clinical stability in selected patients with X-linked HIGM managed with IVIG alone. While HSCT remains the definitive therapy, careful patient selection is critical, particularly in those with mild phenotypes and excellent infection control. This case supports an individualized approach to management, emphasizing quality of life, treatment response, and shared decision-making in rare primary immunodeficiencies.

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2026-04-10 | A Case Report of X-Linked Hyper-IgM Syndrome Associated with the CD40LG Variant: Successful Management with Immunoglobulin G Replacement Therapy

Background: X-linked hyper-IgM syndrome (X-HIGM) is a rare primary immunodeficiency disorder characterized by recurrent infections, hypogammaglobulinemia, and elevated IgM levels. The condition results from mutations in the CD40LG gene, which encodes CD40 ligand, a protein essential for B cell activation and immunoglobulin class switching. This study presents a clinical case of X-HIGM in a young child and highlights the effectiveness of immunoglobulin G replacement therapy in managing the disease.Methods: Whole-exome sequencing and Sanger sequencing were performed to identify the genetic cause of the patient’s recurrent infections. A hemizygous c.409+1_409+19del mutation was identified in the CD40LG gene, confirming the diagnosis of X-HIGM. Immunoglobulin G replacement therapy was administered to manage the patient’s condition.Result: Peripheral immunoglobulins confirmed the clinical observations, with low IgG and A but strikingly high IgM levels. Recurrent otitis media and pneumonia were common in early childhood. The genetic testing performed afterward confirmed that the mutation was present in the two affected siblings. This favorable clinical response with a decrease in the frequency of infections and the stability of the IgG levels over the time suggests that IgRT may have a long-term effective role in the management of a rare primary immunodeficiency. It also stresses the need for genetic workup for diagnosis, family counselling, and management of rare immunodeficiency syndromes.Conclusion: This case highlights the need for early diagnosis and treatment of X-HIGM. IgG replacement therapy is an effective option when stem cell transplantation is not possible or suitable.Keywords:Hyper-IgM syndrome, Primary immunodeficiency, Young children, Immunoglobulin G replacement therapy, CD40LG

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2024-02-15 | Immunoglobulin replacement therapies in inborn errors of immunity: a review

Immunoglobulins (Ig) were used as a therapeutic modality for the first time in a patient with X-linked agammaglobulinemia in 1952 by Colonel Ogden Bruton, decades before the molecular mechanisms causing the disease were unraveled. In many autoimmune and inflammatory illnesses, human immunoglobulin has been employed as a significant immunomodulatory and immunosuppressive drug. In patients with inborn errors of immunity (IEI), immunoglobulin remains a cornerstone of management. IEIs are notable causes of recurrent infections and autoimmunity due to inheritable single-gene defects in genes encoding for different components of the immune system. As there is decreased immunoglobulin production in IEIs with antibody defects, immunoglobulin replacement is the mainstay of therapy in these disorders. Although serum immunoglobulin levels may not be low in combined immune defects, immunoglobulin replacement is still necessary in these disorders due to a deficiency of functional antibodies and qualitative defects of immunoglobulins. Commercial immunoglobulin preparations are generated from plasma donated by thousands of donors. Immunoglobulin preparations are usually available in two forms: intravenous and subcutaneous immunoglobulins. In the developed world, both intravenous immunoglobulin (IVIg) and subcutaneous immunoglobulin (SCIg) are available, and SCIg is preferred over IVIg for replacement therapy in patients with IEIs. In developing countries, IVIg remains the mainstay of replacement therapy. The rate of adverse events has significantly reduced over the last few years due to advancements in the production process. In this review article, we discuss different aspects of the use of Ig (indications, dosing, mechanism of action, route, adverse effects) in patients with IEIs.

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2022-07-08 | Exome sequencing contributes to identify comorbidities in a rare case of infant ARDS induced by the CD40LG mutation

Abstract Background Acute respiratory distress syndrome (ARDS) causes significant mortality in young children with certain diseases. Early diagnosis and treatment can reduce infant mortality. Here, we report a rare case of exome sequencing in the early diagnosis of immunodeficiency in an infant. Case presentation A four-month-old full-term male infant presented with severe shortness of breath, hypoxemia, and unexplained parenchymal lung lesions. A series of examinations were performed to search for potential culprit viruses but negative results were obtained with the only exception being the rhinovirus that tested positive. The child’s family history revealed he had a brother who died of severe infection at the age of two years. We performed an exome sequencing analysis and a mutation analysis of CD40LG to obtain genetic data on the patient. Besides, we used flow cytometry to measure the CD40LG expression levels of activated T cells. A retrospective review of all the CD40LG mutant-induced X-linked hyper IgM syndromes (XHIGM) had been conducted to assess the differences between clinical and genetic molecular features. Finally, a regular intravenous immunoglobulin (IVIG) regimen led to steady breathing, the correction of hypoxemia, and a progressive improvement of lung CT scans. During follow-up, the patient received an IVIG regimen and his CT images improved. Moreover, his parents took advantage of pre-implantation genetic testing with in vitro fertilization to have a healthy twin offspring who did not carry such a mutation according to the early exome sequencing for the proband. Compared with other CD40LG mutant cases in our center, this proband displayed a normal plasma immunoglobulin level and he should be the youngest infant to have a molecular diagnosis of XHIGM. Conclusion Usually, XHIGM would not be suspected with a normal plasma immunoglobulin concentration. However, as we could not identify a potential comorbidity or risk factor, exome sequencing helps target this patient's real facts. Thus, this case report calls for exome sequencing to be performed in the case of unexplained infections when immunodeficiency is suspected after general immunological tests, especially for cases with a contributive family history among infants as the maternal transfused immunoglobulin might mask immune deficiency.

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small molecules

2026-09-25 | Sequential transplantation of allogeneic hematopoietic stem cells and liver in x-linked hyper-IgM syndrome: the role of CMV prophylaxis with letermovir

X-linked hyper-IgM syndrome (XHIM) is a rare inborn error of immunity caused by CD40 ligand deficiency, resulting in combined humoral and cellular immune dysfunction with susceptibility to opportunistic infections, particularly Cryptosporidium-associated sclerosing cholangitis. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment, yet outcomes worsen significantly once advanced liver disease develops. We report the clinical course of a 19-year-old patient with XHIM who underwent HSCT from an 8/10 HLA-mismatched unrelated donor because of progressive sclerosing cholangitis. Early after transplantation, he developed severe cholestasis and persistent fever. Cryptosporidium parvum infection poorly responsive to antimicrobial therapy was diagnosed and resolved only after immunosuppression tapering, paralleling T-cell immune recovery. Despite successful engraftment, progressive cholangiopathy required liver transplantation 6 months after HSCT. Given the high CMV risk and severe cytopenias, letermovir prophylaxis was administered for 100 days post-transplantation. After discontinuation, recurrent CMV reactivations occurred and resolved only following further immunosuppression tapering and subsequent T-cell immune reconstitution. At 3-year follow-up, the patient was clinically well, with full donor chimerism, stable liver function, sustained immune recovery allowing discontinuation of immunoglobulin replacement therapy. This case highlights the importance of early HSCT in XHIM, the central role of immune reconstitution in opportunistic infection control, and the potential utility of extended letermovir prophylaxis in high-risk liver transplant recipients.

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2026-07-07 | Allogeneic hematopoietic cell transplantation with reduced-toxicity conditioning for X-linked hyper-IgM syndrome.

X-linked hyper-IgM syndrome (XHIGM) is an inborn error of immunity caused by variants in the CD40LG gene, leading to disrupted T-cell function and impaired immunoglobulin class-switch recombination. Supportive care alone is linked to unfavorable outcomes, necessitating allogeneic hematopoietic cell transplantation (HCT) as a curative option. Although myeloablative conditioning is recommended for HCT, concerns remain regarding its toxicity. We reviewed ten patients with XHIGM who underwent HCT using reduced-toxicity conditioning (RTC) at our institution between 2010 and 2024. All patients underwent HCT by 5 years of age (range: 2-5 years; median: 3 years). Donor sources included unrelated bone marrow, unrelated cord blood, and haploidentical-related donors. Conditioning primarily consisted of fludarabine and busulfan (target area under the curve: 60-65 mg/L·h), with low-dose total body irradiation (TBI) administered in five patients. Two patients experienced graft failure, requiring a second transplantation, and one died from post-transplant complications. The remaining nine patients survived. The 5-year overall survival rate was 88.9%; the 5-year graft-versus-host disease-free, relapse-free, and second transplantation-free survival rate was 67.5%. The addition of low-dose TBI to fludarabine/busulfan was associated with favorable long-term donor chimerism, although this finding should be considered hypothesis-generating. RTC may represent a feasible conditioning strategy for XHIGM.

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2026-04-26 | The Intertwining Between Arthritis and Inborn Errors of Immunity

Immune dysregulation is being increasingly recognized as a prominent feature of a wide range inborn errors of immunity (IEIs) with different molecular backgrounds. Among the manifestations of immune dysregulation, inflammatory arthritis has emerged as an important yet underrecognized complication that may occur across multiple IEI categories, including humoral immunodeficiencies (such as X-linked agammaglobulinemia, hyper-IgM syndrome, common variable immunodeficiency, and others), complement deficiencies, disorders of immune dysregulation (STAT3 gain of function mutation, CTLA4 and LRBA haploinsufficiency), and combined immunodeficiencies. In some patients, arthritis may represent the first or predominant clinical manifestation, resulting in a diagnostic challenge in the rheumatologic setting. The pathogenesis of arthritis in IEIs reflects different immunological mechanisms, including the defective clearance of immune complexes, dysregulated B- and T-cell responses, impaired regulatory T-cell function, and aberrant cytokine signaling. Clinically, IEI-associated arthritis may mimic classical rheumatologic conditions such as juvenile idiopathic arthritis, rheumatoid arthritis, or other connective tissue diseases, although distinctive immunological and histopathological features are often present. Recognizing arthritis as a potential manifestation of IEIs has important clinical implications. The presence of specific "red flags", including treatment refractoriness, recurrent infections, or additional signs of immune dysregulation (other autoimmune diseases, atopy, lymphoproliferation, enteropathy), should prompt targeted immunological evaluation. While management often relies on conventional immunosuppressive therapies, advances in the molecular characterization of IEIs are increasingly enabling the use of targeted treatments directed at the underlying pathogenic mechanisms. This paper provides an overview of the current knowledge of arthritis associated with IEIs, highlighting diagnostic challenges, underlying immunopathogenic mechanisms, and emerging therapeutic perspectives.

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2024-07-27 | DNA-PK inhibition enhances gene editing efficiency in HSPCs for CRISPR-based treatment of X-linked hyper IgM syndrome

Targeted gene editing to restore CD40L expression via homology-directed repair (HDR) in CD34+ hematopoietic stem and progenitor cells (HSPCs) represents a potential long-term therapy for X-linked hyper IgM syndrome. However, clinical translation of HSPC editing is limited by inefficient long-term engraftment of HDR-edited HSPCs. Here, we ameliorate this issue by employing a small-molecule inhibitor of DNA-PKcs, AZD7648, to bias DNA repair mechanisms to facilitate HDR upon CRISPR SpCas9-based gene editing. Using AZD7648 treatment and a clinically relevant HSPC source, mobilized peripheral blood CD34+ cells, we achieve ∼60% HDR efficiency at the CD40LG locus and enhanced engraftment of HDR-edited HSPCs in primary and secondary xenotransplants. Specifically, we observed a 1.6-fold increase of HDR-edited long-term HSPCs in primary transplant recipients without disturbing chimerism levels or differentiation capacity. As CD40L is primarily expressed in T cells, we demonstrate T cell differentiation from HDR-edited HSPCs in vivo and in artificial thymic organoid cultures, and endogenously regulated CD40L expression following activation of in-vivo-derived CD4+ T cells. Our combined findings demonstrate HDR editing at the CD40LG locus at potentially clinically beneficial levels. More broadly, these data support using DNA-PKcs inhibition with AZD7648 as a simple and efficacious addition to HSPC editing platforms. Targeted gene editing to restore CD40L expression via homology-directed repair (HDR) in CD34+ hematopoietic stem and progenitor cells (HSPCs) represents a potential long-term therapy for X-linked hyper IgM syndrome. However, clinical translation of HSPC editing is limited by inefficient long-term engraftment of HDR-edited HSPCs. Here, we ameliorate this issue by employing a small-molecule inhibitor of DNA-PKcs, AZD7648, to bias DNA repair mechanisms to facilitate HDR upon CRISPR SpCas9-based gene editing. Using AZD7648 treatment and a clinically relevant HSPC source, mobilized peripheral blood CD34+ cells, we achieve ∼60% HDR efficiency at the CD40LG locus and enhanced engraftment of HDR-edited HSPCs in primary and secondary xenotransplants. Specifically, we observed a 1.6-fold increase of HDR-edited long-term HSPCs in primary transplant recipients without disturbing chimerism levels or differentiation capacity. As CD40L is primarily expressed in T cells, we demonstrate T cell differentiation from HDR-edited HSPCs in vivo and in artificial thymic organoid cultures, and endogenously regulated CD40L expression following activation of in-vivo-derived CD4+ T cells. Our combined findings demonstrate HDR editing at the CD40LG locus at potentially clinically beneficial levels. More broadly, these data support using DNA-PKcs inhibition with AZD7648 as a simple and efficacious addition to HSPC editing platforms.

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2024-01-02 | MCT1-governed pyruvate metabolism is essential for antibody class-switch recombination through H3K27 acetylation

Abstract Monocarboxylate transporter 1 (MCT1) exhibits essential roles in cellular metabolism and energy supply. Although MCT1 is highly expressed in activated B cells, it is not clear how MCT1-governed monocarboxylates transportation is functionally coupled to antibody production during the glucose metabolism. Here, we report that B cell-lineage deficiency of MCT1 significantly influences the class-switch recombination (CSR), rendering impaired IgG antibody responses in Mct1 f/f Mb1 Cre mice after immunization. Metabolic flux reveals that glucose metabolism is significantly reprogrammed from glycolysis to oxidative phosphorylation in Mct1 -deficient B cells upon activation. Consistently, activation-induced cytidine deaminase (AID), is severely suppressed in Mct1 -deficient B cells due to the decreased level of pyruvate metabolite. Mechanistically, MCT1 is required to maintain the optimal concentration of pyruvate to secure the sufficient acetylation of H3K27 for the elevated transcription of AID in activated B cells. Clinically, we found that MCT1 expression levels are significantly upregulated in systemic lupus erythematosus patients, and Mct1 deficiency can alleviate the symptoms of bm12-induced murine lupus model. Collectively, these results demonstrate that MCT1-mediated pyruvate metabolism is required for IgG antibody CSR through an epigenetic dependent AID transcription, revealing MCT1 as a potential target for vaccine development and SLE disease treatment.

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2026-05-01 | A First-in-Human Base Edit Gene Therapy for CD40L Deficiency X-Linked Hyper IgM (XHIGM) Syndrome

CD40L-deficient X-linked hyper IgM (XHIGM) syndrome is characterized by defective B cell class switching, deficiency of immunoglobulins G, A, and E, plus other immune abnormalities due to disrupted CD40L–CD40 interaction. Allogeneic hematopoietic stem cell (HSC) transplant can cure XHIGM but requires myeloablative conditioning and risks graft versus host disease (GVHD), posing a high mortality risk. We developed ex vivo base editing (BE) of autologous HSC and T cells to treat a 37-year-old man (P1) diagnosed late in life with a CD40LG c.C>T p.Q220X mutation in a single-patient Investigational New Drug application targeting his mutation (IND32000; NIH protocol 002385). Preclinical studies achieved >90% gene correction of P1 HSC and T cells with base editor ABE8e SpWT/A5 guide, devoid of significant unintended off-target edits. BE-HSC was intended as a definitive transplant to achieve long-term hematopoietic and immune reconstitution, whereas the BE-T cells were designed to serve as a transient bridge therapy of functional T cells during the period preceding differentiation of T cells from the BE-HSC graft. P1 presented pre-gene therapy with sclerosing cholangitis, cryptosporidium infection, nodular regenerative hyperplasia, portal hypertension, bronchiectasis, and lacked HLA-matched donors. Autologous BE-HSC transplant was given after low-dose busulfan conditioning together with prophylactic defibrotide to mitigate chemo-related veno-occlusive disease. The original treatment schema was alemtuzumab (days −21, −20, −19), busulfan 6mg/kg total (days −3, −2) with prophylactic defibrotide, BE-HSC (day 0), and BE-T on day +14 and as indicated for lymphopenia and/or infection. Following alemtuzumab, P1’s baseline abnormal liver function tests (LFTs) worsened (transaminases approximately doubled, bilirubin increased ∼18-fold) with persistent detection of previously undetectable cryptosporidium. We paused busulfan and BE-HSC and administered BE-T products, which corrected LFTs sufficiently to allow uneventful busulfan conditioning and BE-HSC product infusion. Post-treatment at months 1 and 2, blood studies confirmed robust engraftment with normal wild-type alleles in myeloid cells (>90%) and increasing levels in natural killer (>60%), B (>40%), and T (27%) cells and with first-time detection of class-switched IgG+ B cells. This innovative, dual-product strategy provides immediate, on-demand immune protection through infusion of functional BE-T cells, effectively bridging patients through the critical pre-engraftment period and until BE-HSC achieves durable, multilineage reconstitution.

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2026-01-03 | Sensitive and unbiased genome-wide profiling of base-editor-induced off-target activity using CHANGE-seq-BE.

Detection of the off-target effects of base editors is important for identifying their safety risks but current methods for understanding their global activities have limitations in terms of sensitivity or bias by computationally selecting a subset of sites for experimental analysis. We present CHANGE-seq-BE, a method to assess the guide RNA-dependent off-target profile of both adenine and cytosine base editors that is simultaneously sensitive and unbiased. CHANGE-seq-BE relies on selective sequencing of base-editor-modified genomic DNA in vitro and provides comprehensive identification of genome-wide off-target mutations. We found that 98.8% of validated off-target sites were unique to ABE8e adenine base editors compared to Cas9 nuclease, suggesting substantially higher off-target activity of the former. We further applied CHANGE-seq-BE to support genotoxicity studies in an emergency investigational new drug application for customized adenine base editor treatment for a person with CD40L-deficient X-linked hyper IgM syndrome. Our results emphasize the importance of using a base-editor-specific method for identifying off-target activity.

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2025-07-01 | The RNA Binding Protein Bcas2 is Required for Antibody Class Switch in Activated-B Cells.

In children, hyper-IgM syndrome type 1 (HIGM1) is a type of severe antibody disorder, the pathogenesis of which remains unclear. The antibody diversity is partially determined by the alternative splicing (AS) in the germline, which is mainly regulated by RNA-binding proteins, including Breast cancer amplified sequence 2 (Bcas2). However, the effect of Bcas2 on AS and antibody production in activated B cells, the main immune cell type in the germline, remains unknown. To fill this gap, we created a conditional knockout (cKO, B cell-specific AID-Cre Bcas2 fl/fl) mouse model and performed integrated mechanistic analysis on alternative splicing (AS) and CSR in B cells through the RNA-sequencing approach, cross-linking immunoprecipitation and sequencing (CLIP-seq) analysis, and interactome proteomics. The results demonstrate that Bcas2-cKO significantly decreased CSR in activated B cells without inhibiting the B cell development. Mechanistically, Bcas2 interacts with SRSF7 at a conservative circular domain, forming a complex to regulate the AS of genes involved in the post-switch transcription, thereby causing broad-spectrum changes in antibody production. Importantly, we identified GAAGAA as the binding motif of Bcas2 to RNAs and revealed its essential role in the regulation of Bcas2-dependent AS and CSR. In addition, we detected a mutation of at the 3'UTR of Bcas2 gene in children with HIGM1 and observed similar patterns of AS events and CSR in the patient that were discovered in the Bcas2-cKO B cells. Combined, our study elucidates the mechanism by which Bcas2-mediated AS affects CSR, offering potential insights into the clinical implications of Bcas2 in HIGM1.

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2023-11-02 | Unbiased assessment of genome integrity and purging of adverse outcomes at the target locus upon editing of CD4+ T‐cells for the treatment of Hyper IgM1

Hyper IgM1 is an X-linked combined immunodeficiency caused by CD40LG mutations, potentially treatable with CD4+ T-cell gene editing with Cas9 and a "one-size-fits-most" corrective template. Contrary to established gene therapies, there is limited data on the genomic alterations following long-range gene editing, and no consensus on the relevant assays. We developed drop-off digital PCR assays for unbiased detection of large on-target deletions and found them at high frequency upon editing. Large deletions were also common upon editing different loci and cell types and using alternative Cas9 and template delivery methods. In CD40LG edited T cells, on-target deletions were counter-selected in culture and further purged by enrichment for edited cells using a selector coupled to gene correction. We then validated the sensitivity of optical genome mapping for unbiased detection of genome wide rearrangements and uncovered on-target trapping of one or more vector copies, which do not compromise functionality, upon editing using an integrase defective lentiviral donor template. No other recurring events were detected. Edited patient cells showed faithful reconstitution of CD40LG regulated expression and function with a satisfactory safety profile. Large deletions and donor template integrations should be anticipated and accounted for when designing and testing similar gene editing strategies.

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2021-10-25 | Modeling, optimization, and comparable efficacy of T cell and hematopoietic stem cell gene editing for treating hyper-IgM syndrome.

Precise correction of the CD40LG gene in T cells and hematopoietic stem/progenitor cells (HSPC) holds promise for treating X-linked hyper-IgM Syndrome (HIGM1), but its actual therapeutic potential remains elusive. Here, we developed a one-size-fits-all editing strategy for effective T-cell correction, selection, and depletion and investigated the therapeutic potential of T-cell and HSPC therapies in the HIGM1 mouse model. Edited patients' derived CD4 T cells restored physiologically regulated CD40L expression and contact-dependent B-cell helper function. Adoptive transfer of wild-type T cells into conditioned HIGM1 mice rescued antigen-specific IgG responses and protected mice from a disease-relevant pathogen. We then obtained ~ 25% CD40LG editing in long-term repopulating human HSPC. Transplanting such proportion of wild-type HSPC in HIGM1 mice rescued immune functions similarly to T-cell therapy. Overall, our findings suggest that autologous edited T cells can provide immediate and substantial benefits to HIGM1 patients and position T-cell ahead of HSPC gene therapy because of easier translation, lower safety concerns and potentially comparable clinical benefits.

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