Lipopolysaccharide-responsive Beige-like Anchor Research Articles

Exaggerated follicular helper T-cell responses in patients with LRBA deficiency caused by failure of CTLA4-mediated regulation

LPS-responsive beige-like anchor protein (LRBA) and cytotoxic T lymphocyte-associated antigen 4 (CTLA4) deficiencies give rise to overlapping phenotypes of immune dysregulation and autoimmunity, with dramatically increased frequencies of circulating follicular helper T (cTFH) cells. We sought to determine the mechanisms of cTFH cell dysregulation in patients with LRBA deficiency and the utility of monitoring cTFH cells as a correlate of clinical response to CTLA4-Ig therapy. cTFH cells and other lymphocyte subpopulations were characterized. Functional analyses included invitro follicular helper T (TFH) cell differentiation and cTFH/naive B-cell cocultures. Serum soluble IL-2 receptor α chain levels and invitro immunoglobulin production by cultured B cells were quantified by using ELISA. cTFH cell frequencies in patients with LRBA or CTLA4 deficiency sharply decreased with CTLA4-Ig therapy in parallel with other markers of immune dysregulation, including soluble IL-2 receptor α chain, CD45RO+CD4+ effector T cells, and autoantibodies, and this was predictive of favorable clinical responses. cTFH cells in patients with LRBA deficiency were biased toward a TH1-like cell phenotype, which was partially reversed by CTLA4-Ig therapy. LRBA-sufficient but not LRBA-deficient regulatory T cells suppressed invitro TFH cell differentiation in a CTLA4-dependent manner. LRBA-deficient TFH cells supported invitro antibody production by naive LRBA-sufficient B cells. cTFH cell dysregulation in patients with LRBA deficiency reflects impaired control of TFH cell differentiation because of profoundly decreased CTLA4 expression on regulatory T cells and probably contributes to autoimmunity in patients with this disease. Serial monitoring of cTFH cell frequencies is highly useful in gauging the clinical response of LRBA-deficient patients to CTLA4-Ig therapy.

Treatment of severe forms of LPS-responsive beige-like anchor protein deficiency with allogeneic hematopoietic stem cell transplantation

Treatment of severe forms of LPS-responsive beige-like anchor protein deficiency with allogeneic hematopoietic stem cell transplantation

Consanguineous Siblings with a Novel Mutation in Lipopolysaccharide-Responsive Beige-like Anchor protein (LRBA)

Consanguineous Siblings with a Novel Mutation in Lipopolysaccharide-Responsive Beige-like Anchor protein (LRBA)

Treatment of Infantile Inflammatory Bowel Disease and Autoimmunity by Allogeneic Stem Cell Transplantation in LPS-Responsive Beige-Like Anchor Deficiency.

Inflammatory bowel disease (IBD) in young children can be a clinical manifestation of various primary immunodeficiency syndromes. Poor clinical outcome is associated with poor quality of life and high morbidity from the complications of prolonged immunosuppressive treatment and malabsorption. In 2012, mutations in the lipopolysaccharide-responsive beige-like anchor (LRBA) gene were identified as the cause of an autoimmunity and immunodeficiency syndrome. Since then, several LRBA-deficient patients have been reported with a broad spectrum of clinical manifestations without reliable predictive prognostic markers. Allogeneic hematopoietic stem cell transplantation (alloHSCT) has been performed in a few severely affected patients with complete or partial response. Herein, we present a detailed course of the disease and the transplantation procedure used in a LRBA-deficient patient suffering primarily from infantile IBD with immune enteropathy since the age of 6 weeks, and progressive autoimmunity with major complications following long-term immunosuppressive treatment. At 12 years of age, alloHSCT using bone marrow of a fully matched sibling donor—a healthy heterozygous LRBA mutant carrier—was performed after conditioning with a reduced-intensity regimen. During the 6-year follow-up, we observed a complete remission of enteropathy, autoimmunity, and skin vitiligo, with complete donor chimerism. The genetic diagnosis of LRBA deficiency was made post-alloHSCT by detection of two compound heterozygous mutations, using targeted sequencing of DNA samples extracted from peripheral blood before the transplantation.

The plethora, clinical manifestations and treatment options of autoimmunity in patients with primary immunodeficiency.

Although the association between primary immunodeficiency and autoimmunity is already well-known, it has once again become a topic of debate with the discovery of newly-defined immunodeficiencies. Thus, investigation of the mechanisms of development of autoimmunity in primary immunodefficiency and new target-specific therapeutic options has come to the fore. In this study, we aimed to examine the clinical findings of autoimmunity, autoimmunity varieties, and treatment responses in patients who were genetically diagnosed as having primary immunodeficiency. The files of patients with primary immunodeficiency who had clinical findings of autoimmunity, who were diagnosed genetically, and followed up in our clinic were investigated. The demographic and clinical features of the patients and their medical treatments were evaluated. Findings of autoimmunity were found in 30 patients whose genetic mutations were identified. The mean age at the time of the first symptoms was 8.96±14.64 months, and the mean age of receiving a genetic diagnosis was 82.55±84.71 months. The most common diseases showing findings of autoimmunity included immune dysregulation, polyendocrinopathy, enteropathy X-linked syndrome (16.7%); autoimmune lymphoproliferative syndrome (10%); lipopolysaccharide-responsive beige-like anchor protein deficiency (10%); and DiGeorge syndrome (10%). Twelve (40%) patients showed findings of autoimmunity at the time of first presentation. The most common findings of autoimmunity included inflammatory bowel disease, inflammatory bowel disease-like findings (n=14, 46.7%), immune thrombocytopenic purpura (n=11, 36.7%), and autoimmune hemolytic anemia (n=9, 30.0%). A response to immunosupressive agents was observed in 15 (50%) patients. Ten patients underwent hematopoietic stem cell transplantation. Six patients were lost to follow-up due to a variety of complications. Autoimmunity is frequently observed in patients with primary immunodeficiency. The possibility of primary immunodeficiency should be considered in patients with early-onset manifestations of autoimmunity, and these patients should be carefully monitored in terms of immunodeficiency development. Early diagnosis of primary immunodeficiency may provide favorable outcomes in terms of survival.

LRBA is Essential for Allogeneic Responses in Bone Marrow Transplantation.

The PH-BEACH-WD40 (PBW) protein family members play a role in coordinating receptor signaling and intracellular vesicle trafficking. LPS-Responsive-Beige-like Anchor (LRBA) is a PBW protein whose immune function remains elusive. Here we show that LRBA-null mice are viable, but exhibit compromised rejection of allogeneic, xenogeneic and missing self bone-marrow grafts. Further, we demonstrate that LRBA-null Natural Killer (NK) cells exhibit impaired signaling by the key NK activating receptors, NKp46 and NKG2D. However, induction of IFN-γ by cytokines remains intact, indicating LRBA selectively facilitates signals by receptors for ligands expressed on the surface of NK targets. Surprisingly, LRBA limits immunoregulatory cell numbers in tissues where GvHD is primed or initiated, and consistent with this LRBA-null mice also demonstrate resistance to lethal GvHD. These findings demonstrate that LRBA is redundant for host longevity while being essential for both host and donor-mediated immune responses and thus represents a unique and novel molecular target in transplant immunology.

Deficiency of base excision repair enzyme NEIL3 drives increased predisposition to autoimmunity

Alterations in the apoptosis of immune cells have been associated with autoimmunity. Here, we have identified a homozygous missense mutation in the gene encoding the base excision repair enzyme Nei endonuclease VIII-like 3 (NEIL3) that abolished enzymatic activity in 3 siblings from a consanguineous family. The NEIL3 mutation was associated with fatal recurrent infections, severe autoimmunity, hypogammaglobulinemia, and impaired B cell function in these individuals. The same homozygous NEIL3 mutation was also identified in an asymptomatic individual who exhibited elevated levels of serum autoantibodies and defective peripheral B cell tolerance, but normal B cell function. Further analysis of the patients revealed an absence of LPS-responsive beige-like anchor (LRBA) protein expression, a known cause of immunodeficiency. We next examined the contribution of NEIL3 to the maintenance of self-tolerance in Neil3-/- mice. Although Neil3-/- mice displayed normal B cell function, they exhibited elevated serum levels of autoantibodies and developed nephritis following treatment with poly(I:C) to mimic microbial stimulation. In Neil3-/- mice, splenic T and B cells as well as germinal center B cells from Peyer's patches showed marked increases in apoptosis and cell death, indicating the potential release of self-antigens that favor autoimmunity. These findings demonstrate that deficiency in NEIL3 is associated with increased lymphocyte apoptosis, autoantibodies, and predisposition to autoimmunity.

Atypical Manifestation of LPS-Responsive Beige-Like Anchor Deficiency Syndrome as an Autoimmune Endocrine Disorder without Enteropathy and Immunodeficiency

Monogenic primary immunodeficiency syndromes can affect one or more endocrine organs by autoimmunity during childhood. Clinical manifestations include type 1 diabetes mellitus, hypothyroidism, adrenal insufficiency, and vitiligo. Lipopolysaccharide (LPS)-responsive beige-like anchor protein (LRBA) deficiency was described in 2012 as a novel primary immunodeficiency, predominantly causing immune dysregulation and early onset enteropathy. We describe the heterogeneous clinical course of LRBA deficiency in two siblings, mimicking an autoimmune polyendocrine disorder in one of them in presence of the same underlying genetic mutation. The third child of consanguineous Egyptian parents (Patient 1) presented at 6 months of age with intractable enteropathy and failure to thrive. Later on, he developed symptoms of adrenal insufficiency, autoimmune hemolytic anemia, thrombocytopenia, and infectious complications due to immunosuppressive treatment. The severe enteropathy was non-responsive to the standard treatment and led to death at the age of 22 years. His younger sister (Patient 2) presented at the age of 12 to the endocrinology department with decompensated hypothyroidism, perioral vitiligo, delayed pubertal development, and growth failure without enteropathy and immunodeficiency. Using whole exome sequencing, we identified a homozygous frameshift mutation (c.6862delT, p.Y2288MfsX29) in the LRBA gene in both siblings. To our knowledge, our patient (Patient 2) is the first case of LRBA deficiency described with predominant endocrine phenotype without immunodeficiency and enteropathy. LRBA deficiency should be considered as underlying disease in pediatric patients presenting with autoimmune endocrine symptoms. The same genetic mutation can manifest with a broad phenotypic spectrum without genotype–phenotype correlation. The awareness for disease symptoms among non-immunologists might be a key to early diagnosis. Further functional studies in LRBA deficiency are necessary to provide detailed information on the origin of autoimmunity in order to develop reliable predictive biomarkers for affected patients.

LRBA is essential for allogeneic responses in bone marrow transplantation

Abstract Members of the PH-BEACH-WD40 repeat gene family (PBW) play a role in coordinating receptor signaling and intracellular vesicle trafficking. LPS-Responsive Beige-like Anchor (LRBA) is a PBW protein whose immune function has not been defined. Here we show that LRBA−/− mice are viable with normal and healthful life span, but exhibit compromised rejection of allogeneic, xenogeneic and missing self bone marrow grafts. Further we demonstrate that LRBA−/− Natural Killer (NK) cells exhibit impaired signaling by the key NK activating receptors, NKp46 and NKG2D. However, induction of γ-IFN by co-culture with IL12 and IL18 remains intact, indicating LRBA selectively facilitates signals by receptors for ligands expressed on the surface of NK targets. Surprisingly, LRBA limits immunoregulatory cell numbers in tissues where Graft versus Host Disease (GvHD) is primed or initiated, and consistent with this LRBA−/− mice demonstrate resistance to lethal GvHD. These findings demonstrate that LRBA is redundant for host longevity while being essential for both host and donor-mediated immune responses in allogeneic transplantation and thus represent a unique and novel molecular target in transplant immunology.

Infancy-Onset T1DM, Short Stature, and Severe Immunodysregulation in Two Siblings With a Homozygous LRBA Mutation.

Type 1 diabetes mellitus (T1DM) is caused by autoimmunity against pancreatic β-cells. Although a significant number of T1DM patients have or will develop further autoimmune disorders during their lifetime, coexisting severe immunodysregulation is rare. Presuming autosomal-recessive inheritance in a complex immunodysregulation disorder including T1DM and short stature in two siblings, we performed whole-exome sequencing. Two Libyan siblings born to consanguineous parents were presented to our diabetology department at ages 12 and 5 years, respectively. Apart from T1DM diagnosed at age 2 years, patient 1 suffered from chronic restrictive lung disease, mild enteropathy, hypogammaglobulinemia, and GH deficiency. Fluorescence-activated cell sorting analysis revealed B-cell deficiency. In addition, CD4(+)/CD25(+) and CD25(high)/FoxP3(+) cells were diminished, whereas an unusual CD25(-)/FoxP3(+) population was detectable. The younger brother, patient 2, also developed T1DM during infancy. Although his enteropathy was more severe and electrolyte derangements repeatedly led to hospitalization, he did not have significant pulmonary problems. IgG levels and B-lymphocytes were within normal ranges. By whole-exome sequencing we identified a homozygous truncating mutation (c.2445_2447del(C)3ins(C)2, p.P816Lfs*4) in the lipopolysaccharide-responsive beige-like anchor (LRBA) gene in both siblings. The diagnosis of LRBA deficiency was confirmed by a fluorescence-activated cell sorting-based immunoassay showing the absence of LRBA protein in phytohemagglutinin-stimulated peripheral blood mononuclear cells. We identified a novel truncating LRBA mutation in two siblings with T1DM, short stature, and severe immunodysregulation. LRBA mutations have previously been reported to cause multiorgan autoimmunity and immunodysfunction. In light of the variable phenotypes reported so far in LRBA-mutant individuals, LRBA deficiency should be considered in all patients presenting with T1DM and signs of severe immunodysregulation.

The extended phenotype of LPS-responsive beige-like anchor protein (LRBA) deficiency

LPS-responsive beige-like anchor protein (LRBA) deficiency is a primary immunodeficiency caused by biallelic mutations in LRBA that abolish LRBA protein expression. We sought to report the extended phenotype of LRBA deficiency in a cohort of 22 LRBA-deficient patients. Clinical criteria, protein detection, and genetic sequencing were applied to diagnose LRBA deficiency. Ninety-three patients met the inclusion criteria and were considered to have possible LRBA deficiency. Twenty-four patients did not express LRBA protein and were labeled as having probable LRBA deficiency, whereas 22 were genetically confirmed as having definitive LRBA deficiency, with biallelic mutations in LRBA. Seventeen of these were novel and included homozygous or compound heterozygous mutations. Immune dysregulation (95%), organomegaly (86%), recurrent infections (71%), and hypogammaglobulinemia (57%) were the main clinical complications observed in LRBA-deficient patients. Although 81% of LRBA-deficient patients had normal T-cell counts, 73% had reduced regulatory T (Treg) cell numbers. Most LRBA-deficient patients had low B-cell subset counts, mainly in switched memory Bcells (80%) and plasmablasts (92%), with a defective specific antibody response in 67%. Of the 22 patients, 3 are deceased, 2 were treated successfully with hematopoietic stem cell transplantation, 7 are receiving immunoglobulin replacement, and 15 are receiving immunosuppressive treatment with systemic corticosteroids alone or in combination with steroid-sparing agents. This report describes the largest cohort of patients with LRBA deficiency and offers guidelines for physicians to identify LRBA deficiency, supporting appropriate clinical management.

What makes children outgrow food allergy?

What makes children outgrow food allergy?

Lipopolysaccharide-Responsive Beige-like Anchor Is Required for Both Activation and Deactivation of NFkB

The molecular mechanisms why mutations of the lipopolysaccharide-responsive beige-like anchor (LRBA) paradoxically cause both autoimmunity and common variable immunodeficiency (CVID) are unknown. LRBA regulates vesicle trafficking and signal transduction required for the regulation and function of many immune molecules. It is hypothesized that LRBA deficiency attenuates both activation and deactivation of nuclear factor kappa beta (NFkB) resulting in immunodeficiency and autoimmunity.

Long-term remission after allogeneic hematopoietic stem cell transplantation in LPS-responsive beige-like anchor (LRBA) deficiency

Long-term remission after allogeneic hematopoietic stem cell transplantation in LPS-responsive beige-like anchor (LRBA) deficiency

Common variable immunodeficiency (CVID): new genetic insight and unanswered questions.

Common variable immunodeficiency (CVID): new genetic insight and unanswered questions.

Regulatory T-cell deficiency and immune dysregulation, polyendocrinopathy, enteropathy, X-linked–like disorder caused by loss-of-function mutations in LRBA

A number of heritable immune dysregulatory diseases result from defects affecting regulatory T (Treg) cell development, function, or both. They include immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, which is caused by mutations in forkhead box P3 (FOXP3), and IPEX-like disorders caused by mutations in IL-2 receptor α (IL2RA), signal transducer and activator of transcription 5b (STAT5b), and signal transducer and activator of transcription 1 (STAT1). However, the genetic defects underlying many cases of IPEX-like disorders remain unknown. We sought to identify the genetic abnormalities in patients with idiopathic IPEX-like disorders. We performed whole-exome and targeted gene sequencing and phenotypic and functional analyses of Treg cells. A child who presented with an IPEX-like syndrome and severe Treg cell deficiency was found to harbor a nonsense mutation in the gene encoding LPS-responsive beige-like anchor (LRBA), which was previously implicated as a cause of common variable immunodeficiency with autoimmunity. Analysis of subjects with LRBA deficiency revealed marked Treg cell depletion; profoundly decreased expression of canonical Treg cell markers, including FOXP3, CD25, Helios, and cytotoxic Tlymphocyte-associated antigen 4; and impaired Treg cell-mediated suppression. There was skewing in favor of memory Tcells and intense autoantibody production, with marked expansion of T follicular helper and contraction of T follicular regulatory cells. Whereas the frequency of recent thymic emigrants and the differentiation of induced Treg cells were normal, LRBA-deficient T cells exhibited increased apoptosis and reduced activities of the metabolic sensors mammalian target of rapamycin complexes 1 and 2. LRBA deficiency is a novel cause of IPEX-like syndrome and Treg cell deficiency associated with metabolic dysfunction and increased apoptosis of Treg cells.

Sphingosine-1-phosphate receptors control B-cell migration through signaling components associated with primary immunodeficiencies, chronic lymphocytic leukemia, and multiple sclerosis

Five different G protein-coupled sphingosine-1-phosphate (S1P) receptors (S1P1-S1P5) regulate a variety of physiologic and pathophysiologic processes, including lymphocyte circulation, multiple sclerosis (MS), and cancer. Although B-lymphocyte circulation plays an important role in these processes and is essential for normal immune responses, little is known about S1P receptors in human B cells. To explore their function and signaling, we studied B-cell lines and primary B cells from control subjects, patients with leukemia, patients with S1P receptor inhibitor-treated MS, and patients with primary immunodeficiencies. S1P receptor expression was analyzed by using multicolor immunofluorescence microscopy and quantitative PCR. Transwell assays were used to study cell migration. S1P receptor internalization was visualized by means of time-lapse imaging with fluorescent S1P receptor fusion proteins expressed by using lentiviral gene transfer. B-lymphocyte subsets were characterized by means of flow cytometry and immunofluorescence microscopy. Showing that different B-cell populations express different combinations of S1P receptors, we found that S1P1 promotes migration, whereas S1P4 modulates and S1P2 inhibits S1P1 signals. Expression of CD69 in activated B lymphocytes and B cells from patients with chronic lymphocytic leukemia inhibited S1P-induced migration. Studying B-cell lines, normal B lymphocytes, and B cells from patients with primary immunodeficiencies, we identified Bruton tyrosine kinase, β-arrestin 2, LPS-responsive beige-like anchor protein, dedicator of cytokinesis 8, and Wiskott-Aldrich syndrome protein as critical signaling components downstream of S1P1. Thus S1P receptor signaling regulates human B-cell circulation and might be a factor contributing to the pathology of MS, chronic lymphocytic leukemia, and primaryimmunodeficiencies.

LRBA Subcellular Localization: Evidence Of The LRBA's Role In Vesicle Trafficking From The Golgi To Cell Membrane and Endocytosis

Mutation or deletion of lipopolysaccharide responsive beige-like anchor (LRBA) gene causes common variable immunodeficiency, autoimmunity and chronic inflammation. However, the underlying molecular mechanism by which this occurs is unknown. LRBA is similar in structure to the lysosomal trafficking regulator gene. Therefore, it is hypothesized that LRBA may function as a regulator of vesicle trafficking. Its subcellular localization may help to decipher its function.

LRBA Causes Immunodeficiency and Autoimmunity By Deregulating NFkB-Mediated Multiple Immune Effectors Critical For B Cell Activation

The absence of lipopolysaccharide-responsive beige-like anchor (LRBA) gene causes common variable immunodeficiency (CVID), autoimmunity and chronic inflammation. It is the only CVID gene that regulates vesicle trafficking and signal transduction, required for the regulation and function of many immune molecules. It is hypothesized that LRBA deficiency causes these medical conditions by deregulating NFkB-mediated multiple immune effectors critical for B cell activation.

LPS-responsive beige-like anchor (LRBA) gene mutation in a family with inflammatory bowel disease and combined immunodeficiency

Clinical immunology has traditionally relied on accurate phenotyping of the patient's immune dysfunction for the identification of a candidate gene or genes for sequencing and molecular confirmation. Although this is also true for other branches of medicine, the marked variability in immune-related phenotypes and the highly complex network of molecules that confer normal host immunity are challenges that clinical immunologists often face in their quest to establish a specific genetic diagnosis. We sought to identify the underlying genetic cause in a consanguineous family with chronic inflammatory bowel disease-like disorder and combined immunodeficiency. We performed exome sequencing followed by autozygome filtration. A truncating mutation in LPS-responsive beige-like anchor (LRBA), which abolished protein expression, was identified as the most likely candidate variant in this family. The combined exome sequencing and autozygosity mapping approach is a powerful tool in the study of atypical immune dysfunctions. We identify LRBA as a novel immunodeficiency candidate gene the precise role of which in the immune system requires future studies.