LRBA Deficiency Research Articles

Arf1-dependent LRBA recruitment to Rab4 endosomes is required for endolysosome homeostasis.

Deleterious mutations in the lipopolysaccharide responsive beige-like anchor protein (LRBA) gene cause severe childhood immune dysregulation. The complexity of the symptoms involving multiple organs and the broad range of unpredictable clinical manifestations of LRBA deficiency complicate the choice of therapeutic interventions. Although LRBA has been linked to Rab11-dependent trafficking of the immune checkpoint protein CTLA-4, its precise cellular role remains elusive. We show that LRBA, however, only slightly colocalizes with Rab11. Instead, LRBA is recruited by members of the small GTPase Arf protein family to the TGN and to Rab4+ endosomes, where it controls intracellular traffic. In patient-derived fibroblasts, loss of LRBA led to defects in the endosomal pathway promoting the accumulation of enlarged endolysosomes and lysosome secretion. Thus, LRBA appears to regulate flow through the endosomal system on Rab4+ endosomes. Our data strongly suggest functions of LRBA beyond CTLA-4 trafficking and provide a conceptual framework to develop new therapies for LRBA deficiency.

Successful Haematopoietic Stem Cell Transplantation for LRBA Deficiency with Fludarabine, Treosulfan, and Thiotepa-Based Conditioning

LRBA deficiency is an inborn error of immunity defined by autoimmunity, lymphoproliferation, recurrent infections, cytopenia, and inflammatory bowel disease. Despite recent advances in managing this disease with targeted biologic therapy, haematopoietic stem cell transplant (HSCT) remains the only cure. However, great variability exists between protocols used to transplant patients with LRBA deficiency. We describe a cohort of seven patients with LRBA deficiency who underwent HSCT using a myeloablative, reduced toxicity regime of fludarabine, treosulfan, and thiotepa at two transplantation centres from 2016 to 2019. Data were collected both retrospectively and prospectively, measuring time to engraftment, infectious complications, incidence of graft versus host disease, and post-transplantation chimerism. Six of seven patients survived transplantation, and four of six surviving patients achieving treatment-free survival. We thus recommend that HSCT with fludarabine, treosulfan, and thiotepa-based conditioning be considered in patients with LRBA deficiency.

Analysis of LRBA pathogenic variants and the association with functional protein domains and clinical presentation

AbstractLRBA is a cytoplasmic protein that is ubiquitously distributed. Almost all LRBA domains have a scaffolding function. In 2012, it was reported that homozygous variants in LRBA are associated with early‐onset hypogammaglobulinemia. Since its discovery, more than 100 pathogenic variants have been reported. This review focuses on the variants reported in LRBA and their possible associations with clinical phenotypes. In this work LRBA deficiency cases reported more than 11 years ago have been revised. A database was constructed to analyze the type of variants, age at onset, clinical diagnosis, infections, autoimmune diseases, and cellular and immunoglobulin levels. The review of cases from 2012 to 2023 showed that LRBA deficiency was commonly diagnosed in patients with a clinical diagnosis of Common Variable Immunodeficiency, followed by enteropathy, neonatal diabetes mellitus, ALPS, and X‐linked‐like syndrome. Most cases show early onset of presentation at <6 years of age. Most cases lack protein expression, whereas hypogammaglobulinemia is observed in half of the cases, and IgG and IgA levels are isotypes reported at low levels. Patients with elevated IgG levels exhibited more than one autoimmune manifestation. Patients carrying pathogenic variants leading to a premature stop codon show a severe phenotype as they have an earlier onset of disease presentation, severe autoimmune manifestations, premature death, and low B cells and regulatory T cell levels. Missense variants were more common in patients with low IgG levels and cytopenia. This work lead to the conclusion that the type of variant in LRBA has association with disease severity, which leads to a premature stop codon being the ones that correlates with severe disease.

LRBA, a BEACH protein mutated in human immune deficiency, is widely expressed in epithelia, exocrine and endocrine glands, and neurons

Mutations in LRBA, a BEACH domain protein, cause severe immune deficiency in humans. LRBA is expressed in many tissues and organs according to biochemical analysis, but little is known about its cellular and subcellular localization, and its deficiency phenotype outside the immune system. By LacZ histochemistry of Lrba gene-trap mice, we performed a comprehensive survey of LRBA expression in numerous tissues, detecting it in many if not all epithelia, in exocrine and endocrine cells, and in subpopulations of neurons. Immunofluorescence microscopy of the exocrine and endocrine pancreas, salivary glands, and intestinal segments, confirmed these patterns of cellular expression and provided information on the subcellular localizations of the LRBA protein. Immuno-electron microscopy demonstrated that in neurons and endocrine cells, which co-express LRBA and its closest relative, neurobeachin, both proteins display partial association with endomembranes in complementary, rather than overlapping, subcellular distributions. Prominent manifestations of human LRBA deficiency, such as inflammatory bowel disease or endocrinopathies, are believed to be primarily due to immune dysregulation. However, as essentially all affected tissues also express LRBA, it is possible that LRBA deficiency enhances their vulnerability and contributes to the pathogenesis.

Central nervous system manifestations of LRBA deficiency: case report of two siblings and literature review

BackgroundLPS-responsive beige-like anchor protein (LRBA) deficiency is a primary immunodeficiency disease (PID) characterized by a regulatory T cell defect resulting in immune dysregulation and autoimmunity. We present two siblings born to consanguineous parents of North African descent with LRBA deficiency and central nervous system (CNS) manifestations. As no concise overview of these manifestations is available in literature, we compared our patient’s presentation with a reviewed synthesis of the available literature.Case presentationsThe younger brother presented with enteropathy at age 1.5 years, and subsequently developed Evans syndrome and diabetes mellitus. These autoimmune manifestations led to the genetic diagnosis of LRBA deficiency through whole exome sequencing with PID gene panel. At 11 years old, he had two tonic–clonic seizures. Brain MRI showed multiple FLAIR-hyperintense lesions and a T2-hyperintense lesion of the cervical medulla. His sister presented with immune cytopenia at age 9 years, and developed diffuse lymphadenopathy and interstitial lung disease. Genetic testing confirmed the same mutation as her brother. At age 13 years, a brain MRI showed multiple T2-FLAIR-hyperintense lesions. She received an allogeneic hematopoietic stem cell transplantation (allo-HSCT) 3 months later. Follow-up MRI showed regression of these lesions.ConclusionsNeurological disease is documented in up to 25% of patients with LRBA deficiency. Manifestations range from cerebral granulomas to acute disseminating encephalomyelitis, but detailed descriptions of neurological and imaging phenotypes are lacking. LRBA deficiency amongst other PIDs should be part of the differential diagnosis in patients with inflammatory brain lesions. We strongly advocate for a more detailed description of CNS manifestations in patients with LRBA deficiency, when possible with MR imaging. This will aid clinical decision concerning both anti-infectious and anti-inflammatory therapy and in considering the indication for allo-HSCT.

Monogenic inborn errors of immunity in autoimmune disorders.

To estimate the prevalence of monogenic inborn errors of immunity in patients with autoimmune diseases (AID), the study included 56 subjects (male:female ratio: 1.07) with mean age of onset of autoimmunity 7 years (4 months-46 years). 21/56 had polyautoimmunity. 5/56 patients met the JMF criteria for PID. The different AID referred were hematological (42%) > gastrointestinal (GI) (16%) > skin (14%) > endocrine (10%) > rheumatological (8%) > renal (6%) > neurological (2%). 36/56 reported recurrent infections. 27/56 were on polyimmunotherapy. 18/52 (35%) had CD19 lymphopenia, 24/52 (46%) had CD4 lymphopenia, 11/52 (21%) had CD8 lymphopenia, and 14/48 (29%) had NK lymphopenia. 21/50 (42%) had hypogammaglobinemia; 3 of whom were given rituximab. 28/56 were found to have pathogenic variants among PIRD genes. These 28 patients had 42 AID among which hematological was most common (50%) > GI (14%) =skin (14%)> endocrine (9%) >rheumatological (7%) > renal and neurological (2%). Hematological AID was the most common AID (75%) in children with PIRD. Positive predictive value (PPV) of abnormal immunological tests was 50% and sensitivity of 70%. JMF criteria had specificity of 100% in identifying PIRD and sensitivity of 17%. Polyautoimmunity had a PPV of 35% and sensitivity of 40%. 11/28 of these children were offered transplant. 8/28 were started on sirolimus, 2/28 on abatacept, and 3/28 on baricitinib/ruxolitinib after diagnosis. In conclusion, 50% of children with AID have underlying PIRD. LRBA deficiency and STAT1 GOF were the most common PIRD. Age at presentation, number of autoimmunity, routine immunological tests, and JMF criteria are not predictive of underlying PIRD. Early diagnosis with exome sequencing alters the prognosis and opens new therapeutic avenue.

Interstitial cystitis caused by immune dysregulation in LRBA deficiency: one among the rare urological manifestations in inborn errors of immunity

Inborn errors of immunity (IEI) rarely present with associated urological manifestations. Chronic cystitis and urethritis caused by ureaplasma and mycoplasma infection in hypogammaglobulinemia may result in bladder fibrosis. Papovaviridae such as BK or JC, can cause hemorrhagic cystitis in patients with T cell defects. Bladder granulomtata and urethral strictures can occur in chronic granulomatous disease. This is the first reported case of severe lymphocytic interstitial cystitis in a patient with lipopolysaccharide-responsive beige-like anchor protein (LRBA) deficiency. LRBA deficiency is known to impair CTLA-4 recycling, leading to decreased Treg cell function. A 13 year old male refugee presented with chronic recurrent debilitating suprapubic pain and dysuria, which progressed to extreme urinary frequency. He had a prior history of recurrent aseptic urinary tract infections, and one episode of gross hematuria. Extensive infectious investigations of urine (bacterial, mycobacterial cultures; viral PCRs), blood, and stool (Schistosoma) failed to isolate a pathogen. Bladder biopsy was positive for EBV by PCR but blood remained EBV-negative. Urinalysis showed microscopic hematuria while urodynamic studies were normal, and cystoscopy showed bladder and urethral irritation. Pathology confirmed lymphocytic interstitial cystitis, with primarily T cell infiltration. Immunological investigations revealed low IgG, IgA and IgM levels, B lymphopenia (1%), with low class-switched memory B cell development (3%) and absent response to protein and polysaccharide vaccine antigens. There were no signs of autoimmunity. Parents are consanguineous, and a sibling was likewise diagnosed with LRBA deficiency. Sanger sequencing of DNA confirmed the same homozygous family mutation in the LRBA gene, a likely pathogenic splice donor variant, c.2258+2T>G. The patient was started on immunoglobulin replacement. Trials of analgesics including NSAIDs, gabapentin, and morphine, and immunosuppression with corticosteroids and sirolimus, were unsuccessful in reducing urinary symptoms. Physiotherapy and antispasmodics were introduced when pelvic-floor dyssynergia with rectal pain developed. Subsequently-presenting enteropathy was managed with Abatacept (CTLA-4 IgG1 fusion protein), ultimately improving bladder symptoms after several months of therapy. Patient has since undergone HSCT and is now free of urinary tract symptoms. LRBA deficiency presents with hypogammaglobulinemia, infections, and immune dysregulation presenting with lymphocytic infiltration of non-lymphoid organs. This report highlights the phenotypic diversity of this disease.

Normal LRBA expression in a patient with LRBA deficiency: Understanding the clinical test

An 11-year-old girl presented as a new immunology patient with a history of celiac disease, inflammatory bowel disease, asthma, chronic bilateral otitis, autoimmune hemolytic anemia, and chronic splenomegaly. In addition, she had generalized lymphadenopathies and chronic lung disease (bronchiectasis, ground glass infiltrates, and nodular opacities). Relevant laboratory findings included anemia, neutropenia, elevated ESR (62), positive ANAs (1:320), poor antibody responses and hypogammaglobulinemia, slightly elevated αβ+double negative T-cells (1.6%) and serum soluble CD25 levels (9560 pg/mL). Parents are consanguineous and genetic testing reveals a homozygous pathogenic variant in LRBA (c.5980C>T). This is a novel defect predicted to cause a premature translational stop signal (p. Arg1994*), resulting in an absent or disrupted protein. The patient responded favorably to abatacept and subcutaneous IgG replacement with resolution of lymphadenopathies, organomegaly and cytopenias, improvement of infections and gastrointestinal symptoms, and decrease in inflammatory markers and serum soluble CD25 levels. Unexpectedly, during her evaluation, flow cytometry to assess intracellular LRBA using a polyclonal rabbit antibody (Sigma-Aldrich) showed protein expression in 100% of T-cells and 99% of B-cells. Since the patient’s clinical and genetic findings and her response to abatacept indicated LRBA deficiency, we reassessed LRBA expression using a different assay with an anti-LRBA monoclonal antibody recognizing the protein N-terminal (Clone 2D4.1, Milipore). This assay showed essentially absent expression of LRBA in T-cells (1.7% in CD4+ and 11.5% in CD8+), B-cells (3.6%), and NK-cells (0.8%), fitting with both our genetic findings and clinical phenotype. Hence, assays detecting LRBA expression may have discrepant results and understanding the technicalities of how they are performed is critical for their interpretation and avoiding potential pitfalls. For instance, it is possible that epitopes targeted by a polyclonal antibody could still be identified on a mutated LRBA protein, yielding normal protein phenotyping levels in LRBA deficient patients. Presence of protein also does not equate to functional protein but a validated functional clinical test for LRBA is yet unavailable. In conclusion, this case underscores the importance of using genetic and functional data in the context of the clinical phenotype for IEI diagnosis.

The utility of HLA-DR+CD38high expression in quantifying the amplitude of T cell activation in HLH and immune dysregulation disorders

IntroductionIdentifying T-cell activation, the hallmark of multiple hyperinflammatory diseases like HLH and immune dysregulation disorders (IDS) like LRBA deficiency, is critical for diagnosis, management, and monitoring treatment response for patients with immune activation driven disease processes. Soluble Interleukin 2 Receptor (sIL2R) is an established systemic marker for T-cell activation but the clinical availability of sIL2R testing is limited. sIL2R is also not a reliable marker of T-cell activation in patients with eosinophilia or T-cell lymphoma. A recent study by Chaturvedi et.al has demonstrated the utility of flow-based T-cell activation assessment in differentiating HLH from sepsis. However, its utility in defining and quantifying T-cell activation across the hyperinflammatory spectrum and its correlation with sIL2R has not yet been established. MethodsA total of 125 samples were collected either at disease onset (n = 81) or at follow-up (n = 44) from 85 human subjects. Paired plasma sIL2R and T-cell activation markers were prospectively evaluated in patients with suspected HLH (n = 79) or IDS (n = 46). Flow cytometry-based T-cell activation was evaluated in different T-cell sub-compartments by the coexpression of HLA-DR and CD38 surface markers. ResultsEvaluation of T-cell activation measured by HLADR+CD38high in healthy controls (HCs) and different hyperinflammatory/ immune regulatory disorders revealed that HCs have less than 8% of T-cell activation in CD8 + Teffector memory (TEM) and less than 4% for activation in the CD4+ TEM compartments. In patients with suspected hyperinflammatory/ immune regulatory disorders, we identified significant correlation of direct T-cell activation with plasma sIL2R level in different T-cell subsets, CD3 (r = 0.44, p < 0.0001), CD4 (r = 0.41, p < 0.0001), CD8 (r = 0.45, p < 0.001), CD4 TEM (Teffector memory) (r = 0.53, p < 0.001), and CD8 TEM (r = 0.53, p < 0.0001).The strongest correlation between HLADR+CD38high with sIL2R level was noted in CD4+ TEM and CD8+ TEM compartments (Figure 1). [Display omitted] [Display omitted] ConclusionsFlow cytometry-based direct assessment of HLADR+ CD38high in T cells subsets can reliably quantify T-cell activation and strongly correlate with sIL2R level across a spectrum of different hyperinflammatory and immune dysregulation disorders.

Mild COVID-19 outcomes in adults with inborn errors of immunity: a single-center experience

Currently, 640 million cases of coronavirus disease 2019 (COVID-19) and 6.6 million deaths have been reported world-wide. Risk factors for severe COVID-19 are known, including those with compromised immunity. Among patients with inborn errors of immunity (IEI), early reports of severe outcomes lead to strict masking and social distancing measures. While this resulted in relatively low infection rates among those with IEI, real-world data describing the clinical course of COVID-19 in this patient population have remained limited. We performed a retrospective study of adult IEI patients followed by our center in which a positive test (rapid antigen or PCR) for COVID-19 was determined between November 2021-November 2022. Medical charts were reviewed, and patient interviews conducted. All patients provided informed consent. Twenty-nine patients were enrolled (22 females, 7 males), aged between 18–69 years (median: 20–29 years). The cohort included those with antibody deficiencies (41.37%), combined immunodeficiencies (34.48%; HIES, CARD11, STAT1-GOF), immune dysregulation disorders (20.69%; LRBA deficiency, AIRE deficiency) and phagocyte defect (3.45%; CGD). The duration of symptoms ranged between 3 days-4 weeks (median: < 1 week). Upper respiratory symptoms (including sore throat, congestion) were reported in 97% while fever was present in 41% of patients. Prior to infection, 14 (48%) patients had underlying asthma or bronchiectasis - 2 subsequently experienced shortness of breath and were treated with inhalers or Sotrovimab, respectively. No treatment was required in 65.5% of cases. The remaining received Paxlovid (10.3%), Sotrovimab (13.79%), or antibiotics (10.3%). Of the 2 patients with STAT1-GOF, one tested positive during a repeat episode of febrile neutropenia which required hospitalization. No other patients were hospitalized or needed ICU admission. No deaths were recorded. In light of these favourable outcomes, patients with IEI can gradually and safely return to normal activities.

Monogenic inborn errors of immunity in autoimmune disorders

To estimate the prevalence of monogenic inborn errors of immunity in patients with autoimmune diseases. This was a retrospective and prospective cohort study. The study included 56 subjects (Male:Female ratio: 1.07) with mean age of onset of autoimmunity of 7 years (4months-46 years). 21/57 (37.5%) had polyautoimmunity. 5/56 patients met the JMF criteria for PID. The different AID referred were hematological (42%) > GI (16%) > Skin (14%) > Endocrine (10%) > Rheumatological (8%) > Renal (6%) > Neurological (2%). 36/57 (63%) reported recurrent infections. 27/56 were on polytherapy, 46 had received steroids. 18/52 (35%) had CD19 lymphopenia, 24/52(46%) had CD4 lymphopenia, 11/52(21%) had CD8 lymphopenia, 14/48 (29%) had NK lymphopenia. 20/50 (42%) had hypogammaglobinemia. 28/56 (50%) were found to have pathogenic variants among PIRD genes (LRBA:6, STAT1 GOF: 3, CTLA4: 2, ACP5: 2, 1 each with NFKB1, NLRP12, CARD11 GOF, STAT3 GOF, RTEL1, NCF2, ATM, RAG1, BTK, IL12RB1, CR2 and CD55 microdeletion/CHAPEL, FOXP3, PIK3CD, CD40L, ADA2). These 28 patients had 41 autoimmune diseases. Hematological AID was most common (50%)>GI (16%)>Endocrine (9%)>Skin (11%)>Rheumatological (7%)>Renal and neurological (1%). Hematological AID is most common manifestation in almost 75% of children with PIRD. Positive predictive value of abnormal immunological tests was 50% and sensitivity of 70%. JMF criteria had specificity of 100% in identifying PIRD but sensitivity was only 17%. Polyautoimmunity had a positive predictive value of 35% and sensitivity of only 40%. Avg age at initial presentation with autoimmunity in patients with underlying PIRD was 7.4 years vs 6.4 years in those without PIRD. 11/28 of these children were offered transplant out of whom 4 have successful transplants. 8/28 were started on sirolimus, 2/28 on abatacept, 3/28 on baracitinib, 2/29 on ruxolitinib after diagnosis that led to steroid withdrawal. 4 have died. Conclusion: 50% of children with AID have underlying PIRD. LRBA deficiency and STAT1 GOF were the most common PIRD. Age at presentation, number of autoimmunity, routine immunological tests and JMF criteria are not predictive of underlying PIRD. Early diagnosis with exome sequencing alters the prognosis and opens new therapeutic avenue.

Expandig Lentiviral Vectors cargo capacity with protein trans-splicing

In the last decades Lentiviral vectors (LVs) have been widely used as vehicles to stably transfer and express genes in mammalian cells in the context of monogenic diseases in both dividing and non-dividing or slowlyproliferating cells, as human CD34+ stem cells (CD34+ HSCs). However LVs cargo capacity, limited to around 8 kilobases (kb), prevents their application for the treatment of conditions requiring the delivery of larger DNA sequences and the stable expression of the transgene in actively proliferating cells. Recent studies have shown that protein trans-splicing is a powerful means to ably reconstitute large full-length proteins upon coinfection of a host cell with different vectors, each expressing a split-intein flanked portion of the full lenght- protein. The aim of our study is to translate the same technology to the platform of LVs. As proof-of-principle developed lentiviral expression plasmids (pLenti), each encoding either the N- or the C-terminal half of the EGFP reporter protein fused to the N- and C-terminal halves of the DnaE split-inteins from Nostoc punctiforme, under the control of EF1A promoter. We co-transfected HEK293 cells and we demonstrated the reconstitution of a functional full-lenght protein of the proper size. We are currently generating LVs from these pLenti that we will use to infect both lineage-negative cells from mouse bone marrow and CD34+ HSCs in order to assess if the platform of LVs is as efficient as AAVs. This system will be helpful to develop a gene therapy approach for specific inborn errors of immunity, including LRBA deficiency and Ataxia Telangiectasia, caused by mutations in genes larger than 8 kb.

Role of Protein Kinase A Activation in the Immune System with an Emphasis on Lipopolysaccharide-Responsive and Beige-like Anchor Protein in B Cells

Cyclic AMP-dependent protein kinase A (PKA) is a ubiquitous enzymatic complex that is involved in a broad spectrum of intracellular receptor signaling. The activity of PKA depends on A-kinase anchoring proteins (AKAPs) that attach to PKAs close to their substrates to control signaling. Although the relevance of PKA-AKAP signaling in the immune system is evident in T cells, its relevance in B and other immune cells remains relatively unclear. In the last decade, lipopolysaccharide-responsive and beige-like anchor protein (LRBA) has emerged as an AKAP that is ubiquitously expressed in B and T cells, specifically after activation. A deficiency of LRBA leads to immune dysregulation and immunodeficiency. The cellular mechanisms regulated by LRBA have not yet been investigated. Therefore, this review summarizes the functions of PKA in immunity and provides the most recent information regarding LRBA deficiency to deepen our understanding of immune regulation and immunological diseases.

HLA-DR+ CD38high Expression in T Cells Is Excellent in Quantifying the Amplitude of T-Cell Activation in a Spectrum of Hyperinflammatory Disorders Including HLH

Introduction: T cell activation is the hallmark of several hyperinflammatory states such as HLH and immune dysregulation disorders like LRBA deficiency. Identifying T-cell activation and quantifying the amplitude of T-cell activation is critical for diagnosis, management, and monitoring treatment response in patients with hyperinflammatory and immune regulatory disorders. Soluble Interleukin 2 Receptor (sIL2R) is one of the established systemic T-cell activation markers for diagnosing and monitoring HLH and other hyperinflammatory disorders. However, the clinical availability of sIL2R testing is limited, and it may not be a reliable marker of T-cell activation in patients with eosinophilia and T-cell lymphoma. A recent study by Chaturvedi et.al has demonstrated the utility of flow-based T-cell activation assessment in differentiating HLH from sepsis. However, its utility in defining and quantifying T-cell activation across the hyperinflammatory spectrum and its correlation with sIL2R has not yet been established. Methods: A total of 125 samples were collected either at disease onset (n = 81) or at follow-up (n = 44) from 85 human subjects. Paired plasma sIL2R and T-cell activation markers were prospectively evaluated in patients with suspected HLH (n = 79) or immune dysregulation disorders (n = 46). Out of 85 patients, 21 patients were diagnosed with either primary HLH (p-HLH), Epstein-Barr virus infection-associated HLH (EBV-HLH), malignancy-associated HLH (m-HLH), or macrophage activation syndrome (MAS). The rest of the patients were diagnosed with either sepsis, multisystem inflammatory syndrome in children (MIS-C), hyperinflammatory conditions, hepatitis, or acute liver failure. Flow cytometry-based T-cell activation was evaluated in different T-cell sub-compartments by the co-expression of HLA-DR and CD38 surface markers. Plasma sIL2R levels and CXCL9 (a chemokine driven by IFN-g) were determined independently in CLIA certified clinical diagnostic laboratory. Research personnel who analyzed the flow cytometry data were blinded to the corresponding sIL2R test results and clinical diagnosis. Longitudinal follow-up was performed for a subset of patients with HLH or immune dysregulation with evidence of T-cell activation. We also evaluated T-cell activation in 30 healthy controls (HC) to establish a reference range. In addition, the correlation between T-cell activation markers with plasma levels of sIL2R and CXCL9 was also investigated. Results: Evaluation of T-cell activation measured by HLADR+CD38high in HCs and different hyperinflammatory/ immune regulatory disorders revealed that HCs have less than 8% of T-cell activation in CD8+ T effector memory (TEM) and less than 4% for activation in the CD4+ TEM compartments. In patients with suspected hyperinflammatory/ immune regulatory disorders, we identified significant correlation of direct T-cell activation with plasma sIL2R level in different T-cell subsets, CD3 (r = 0.44, p < 0.0001), CD4 (r = 0.41, p < 0.0001), CD8 (r = 0.45, p <0.001), CD4 TEM (T effector memory) (r =0.53, p < 0.001), and CD8 TEM (r =0.53, p < 0.0001). The strongest correlation between HLADR+CD38high with sIL2R level was noted in CD4+ TEM and CD8+ TEM compartments (Figure 1). The correlation is even more robust at disease onset (r = 0.69, p <0.0001 for CD4+ TEM and r = 0.64, p < 0.0001 for CD8+ TEM). However, at follow up, only activation in CD8+ TEM correlated with sIL2R levels (r = 0.4, p = 0.0069). Moreover, T-cell activation in CD8+ TEM correlated well with CXCL9 and ferritin levels. Among the cohort of patients with the confirmed final diagnosis, we found that both p-HLH and EBV-HLH have CD8+ TEM activation > 70%, whereas MAS and m-HLH have a median T cell activation of 37.8% (10.5-67) and 48.1% (4.9-80.6) respectively. Immune dysregulation patients had T-cell activation range from 8.0 to 46.0 % and sepsis group has 0% to 10.8% (Figure 2). A similar trend was also validated using corresponding plasma sIL2R levels in different hyperinflammatory states. Conclusions: Flow cytometry-based direct assessment of HLADR+CD38high in T cells subsets can reliably quantify T-cell activation and strongly correlate with sIL2R level across a spectrum of different hyperinflammatory and immune dysregulations disorders. If validated, this could be used as a real-time assessment of T-cell activation at disease onset and monitoring response to therapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Hematopoietic stem cell Transplantation in Children with very Early Onset Inflammatory Bowel Disease Secondary to Monogenic Disorders of immune-dysregulation.

Background: Very early-onset inflammatory bowel disease (VEOIBD) is defined as IBD in children under six years of age. We present outcome data of hematopoietic stem cell transplantation (HSCT) in the above children. Patients and methods: We performed a retrospective study in children under six years of age who underwent HSCT for VEOIBD with an identified monogenic disorder from December 2012 to December 2020. Results: Of the 25 children included, the underlying diagnosis was IL10R deficiency (n = 4), Wiskott-Aldrich syndrome (n = 4), Leukocyte adhesion defect (n = 4), Hyper IgM syndrome (n = 3), Chronic granulomatous disease (n = 2), and one each with XIAP deficiency, severe congenital neutropenia, Omenn syndrome, Hyper IgE syndrome, Griscelli syndrome, MHC Class II deficiency, LRBA deficiency, and IPEX syndrome. Donors included a matched family donor in 10(40%); a matched unrelated donor in 8 (32%), haploidentical in 7 (28%) (T depleted 16%, T replete with post-transplant cyclophosphamide12%). Conditioning was myeloablative in 84% ofHSCTs. We documented engraftment in 22 (88%) children, primary graft failure in 2 children (8%), mixed chimerism in 6 (24%) children with mortality in 4/6 children. Children with a sustained chimerism of > 95% did not have recurrence of any features of IBD. Overall survival was 64%, with a median follow-up of 55 months. Mixed chimerism was associated with a significantly increased risk of mortality (p-value = 0.001). Conclusions: VEOIBD caused by monogenic disorders can be offered HSCT. Early recognition, optimal supportive care, and complete chimerism are essential components to achieving survival.

The ABACHAI clinical trial protocol: Safety and efficacy of abatacept (s.c.) in patients with CTLA-4 insufficiency or LRBA deficiency: A non controlled phase 2 clinical trial

BackgroundCytotoxic T-lymphocyte-associated protein 4 (CTLA-4) insufficiency and lipopolysaccharide-responsive and beige-like anchor protein (LRBA) deficiency are both complex immune dysregulation syndromes with an underlying regulatory T cell dysfunction due to the lack of CTLA-4 protein. As anticipated, the clinical phenotypes of CTLA-4 insufficiency and LRBA deficiency are similar. Main manifestations include hypogammaglobulinemia, lymphoproliferation, autoimmune cytopenia, immune-mediated respiratory, gastrointestinal, neurological, and skin involvement, which can be severe and disabling. The rationale of this clinical trial is to improve clinical outcomes of affected patients by substituting the deficient CTLA-4 by administration of CTLA4-Ig (abatacept) as a causative personalized treatment. ObjectivesOur objective is to assess the safety and efficacy of abatacept for patients with CTLA-4 insufficiency or LRBA deficiency. The study will also investigate how treatment with abatacept affects the patients’ quality of life. Methods/Design: ABACHAI is a phase IIa prospective, non-randomized, open-label, single arm multi-center trial. Altogether 20 adult patients will be treated with abatacept 125 mg s.c. on a weekly basis for 12 months, including (1) patients already pretreated with abatacept, and (2) patients not pretreated, starting with abatacept therapy at the baseline study visit. For the evaluation of drug safety infection control during the trial, for efficacy, the CHAI-Morbidity Score will be used. Trial registrationThe trial is registered in the German Clinical Trials Register (Deutsches Register Klinischer Studien, DRKS) with the identity number DRKS00017736, registered: 6 July 2020, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00017736.

Regulatory B cells in patients suffering from inborn errors of immunity with severe immune dysregulation

BackgroundImmune dysregulation as a result of an inborn error of immunity (IEI) leads to the complicated symptoms of refractory multi-organ immune dysregulation. B lymphocytes with immune regulatory capacity (Breg) are activated by environmental triggers and act as regulators of the immune response as observed in several autoimmune diseases. ObjectiveWe sought to investigate the Breg profile and the CD21low expressing B cells of patients with LRBA deficiency (N = 6) and non-LRBA deficiency IEI (N = 13) with overlapping clinical symptoms of immune dysregulation. Normal values for Breg subpopulations were obtained from patients age-matched healthy cohorts (N = 48). Furthermore, we investigated the impact of abatacept treatment in LRBA deficient patients receiving biweekly abatacept (N = 5). MethodsUsing a flow cytometric approach with a pre-formulated antibody panel in peripheral blood samples, Breg subsets including plasmablasts (CD27+CD38hi), transitional B cells (CD24hiCD38hi), and B10 cells (CD24hiCD27+), and additionally the CD21low B cells (CD21lowCD38low) were analyzed. Breg function was assessed by the interleukin-10 expression within the CD19+ population. Additionally, B cell cytokines were measured in cell culture supernatants. ResultsWe observe significant alterations of B cell/Breg subpopulations in the LRBA deficient cohort including a severe lack of memory B cells (P = 0.031) and B10 cells (P = 0.031) as well as a tendency towards higher CD21low B cells (P = 0.063). Within the non-LRBA deficient cohort, we observe a significant expansion of the plasmablasts (P = 0.012), and a tendency towards elevated levels of CD21low expressing B cells (P = 0.063). The treatment with abatacept ameliorated disease symptoms in the LRBA deficient cohort and led to an effective decrease in CD21low B cells over time (P = 0.021). Furthermore, there was a significantly increased level of B cell-activating factor (BAFF; P = 0.02) and lower IL-12p70 secretion upon stimulation (P = 0.020) in the LRBA cohort. ConclusionAberrant maturation of Breg subsets and the pathological expansion of CD21low B cells in patients with IEI may have therapeutic implications. Patients suffering from LRBA deficiency show a lack of memory B cells, insufficient expansion of B10 cells, increased BAFF levels as well as an increase in circulating CD21low B cells. Abatacept treatment results in a steady decrease in CD21low B cells.

Very-Early Onset Chronic Active Colitis with Heterozygous Variants in LRBA1 and CARD11, a Case of “Immune TOR-Opathies”

Background A small subset of cases of inflammatory bowel disease (IBD) occurs as a result of single gene defects, and typically occurs in young or very young pediatric patients, referred to as “monogenic very-early onset IBD (VEO-IBD)”. The gene variants leading to monogenic VEO-IBD are often associated with primary immunodeficiency syndromes. Case report A six year-old girl presented to our gastroenterology clinic with LRBA deficiency with a heterozygous mutation at c.1399 A > G, p Met467Val, histopathologic chronic active colitis without granulomas and clinical chronic colitis. Her gastrointestinal symptoms began at age 5 with bloody diarrhea, abdominal pain and weight loss. Whole exome sequencing revealed a CARD11 heterozygous de novo mutation (c.220 + 1G > A). She was in clinical remission on only abatacept. Discussion We present a case of monogenic VEO-IBD associated with two heterozygous variants in LRBA1 and CARD11, both considered as key players in the newly proposed “immune TOR-opathies”.

LRBA Deficiency Can Lead to Lethal Colitis That Is Diminished by SHIP1 Agonism.

Humans homozygous for inactivating LRBA (lipopolysaccharide (LPS)-responsive beige-like anchor) mutations or with compound heterozygous mutations exhibit a spectrum of immune-related pathologies including inflammatory bowel disease (IBD). The cause of this pathology remains undefined. Here we show that disruption of the colon epithelial barrier in LRBA-deficient mice by dextran sulfate sodium (DSS) consumption leads to severe and uniformly lethal colitis. Analysis of bone marrow (BM) chimeras showed that susceptibility to lethal colitis is primarily due to LRBA deficiency in the immune compartment and not the gut epithelium. Further dissection of the immune defect in LRBA-deficient hosts showed that LRBA is essential for the expression of CTLA4 by Treg cells and IL22 and IL17 expression by ILC3 cells in the large intestine when the gut epithelium is compromised by DSS. We further show that SHIP1 agonism partially abrogates the severity and lethality of DSS-mediated colitis. Our findings indicate that enteropathy induced by LRBA deficiency has multiple causes and that SHIP1 agonism can partially abrogate the inflammatory milieu in the gut of LRBA-deficient hosts.

Understanding the Mechanism of Diabetes Mellitus in a LRBA-Deficient Patient.

Simple SummaryDeficiency of lipopolysaccharide responsive beige like anchoring protein (LRBA) has been reported to cause immunological complications that can be fatal in children. Diabetes mellitus (DM) has been reported in some patients with LRBA deficiency. However, the underlying mechanism of the DM is not known. The current study provides potential novel insights into the underlying mechanism of DM in a LRBA-deficient patient. Additionally, in mouse pancreatic β-cells, we show that LRBA plays a role in the dynamics of insulin secretion and biosynthesis.The scope of this study is to show that DM in a LRBA-deficient patient with a stop codon mutation (c.3999 G > A) was not mediated through autoimmunity. We have evaluated the ability of the proband’s T cells to be activated by assessing their CTLA-4 expression. A nonsignificant difference was seen in the CTLA-4 expression on CD3+ T cells compared to the healthy control at basal level and after stimulation with PMA/ionomycin. Blood transcriptomic analysis have shown a remarkable increase in abundance of transcripts related to CD71+ erythroid cells. There were no differences in the expression of modules related to autoimmunity diseases between the proband and pooled healthy controls. In addition, our novel findings show that siRNA knockdown of LRBA in mouse pancreatic β-cells leads reduced cellular proinsulin, insulin and consequently insulin secretion, without change in cell viability in cultured MIN6 cells.