Clinical and Immunological Phenotype of Patients With Primary Immunodeficiency Due to Damaging Mutations in NFKB2

Abstract

Non-canonical NF-κB-pathway signaling is integral in immunoregulation. Heterozygous mutations in NFKB2 have recently been established as a molecular cause of common variable immunodeficiency (CVID) and DAVID-syndrome, a rare condition combining deficiency of anterior pituitary hormone with CVID. Here, we investigate 15 previously unreported patients with primary immunodeficiency (PID) from eleven unrelated families with heterozygous NFKB2-mutations including eight patients with the common p.Arg853* nonsense mutation and five patients harboring unique novel C-terminal truncating mutations. In addition, we describe the clinical phenotype of two patients with proximal truncating mutations. Cohort analysis extended to all 35 previously published NFKB2-cases revealed occurrence of early-onset PID in 46/50 patients (mean age of onset 5.9 years, median 4.0 years). ACTH-deficiency occurred in 44%. Three mutation carriers have deceased, four developed malignancies. Only two mutation carriers were clinically asymptomatic. In contrast to typical CVID, most patients suffered from early-onset and severe disease manifestations, including clinical signs of T cell dysfunction e.g., chronic-viral or opportunistic infections. In addition, 80% of patients suffered from (predominately T cell mediated) autoimmune (AI) phenomena (alopecia > various lymphocytic organ-infiltration > diarrhea > arthritis > AI-cytopenia). Unlike in other forms of CVID, auto-antibodies or lymphoproliferation were not common hallmarks of disease. Immunophenotyping showed largely normal or even increased quantities of naïve and memory CD4+ or CD8+ T-cells and normal T-cell proliferation. NK-cell number and function were also normal. In contrast, impaired B-cell differentiation and hypogammaglobinemia were consistent features of NFKB2-associated disease. In addition, an array of lymphocyte subpopulations, such as regulatory T cell, Th17-, cTFH-, NKT-, and MAIT-cell numbers were decreased. We conclude that heterozygous damaging mutations in NFKB2 represent a distinct PID entity exceeding the usual clinical spectrum of CVID. Impairment of the non-canonical NF-κB pathways affects function and differentiation of numerous lymphocyte-subpopulations and thus causes a heterogeneous, more severe form of PID phenotype with early-onset. Further characteristic features are multifaceted, primarily T cell-mediated autoimmunity, such as alopecia, lymphocytic organ infiltration, and in addition frequently ACTH-deficiency.

A Nonsense N –Terminus NFKB2 Mutation Leading to Haploinsufficiency in a Patient with a Predominantly Antibody Deficiency

“…While NFKB2 C-terminus LOF mutations are associated with reduced p52 expression and nuclear translocation due to the failure of phosphorylation and processing of C-terminusmutated p100; GOF mutations show decreased levels of p100 due to truncated mutant expression leading to increased nuclear translocation of RelB/GOF mutant complexes that in its turn increase the activation of downstream pathways [6]. Moreover, while C-terminal LOF mutations are almost fully penetrant (1/43 asymptomatic) and endocrine defects are common (21/43), GOF and haploinsufficiency mutations are not fully penetrant (1 (or 2)/5 asymptomatic for GOF and 2/3 for haploinsufficiency) and endocrine defects have not been described in neither of these allelic variants [4][5][6]. It is likely that the C-terminus NFKB2 mutants exert a dominant negative effect on NF-kB signaling by preventing nuclear translocation of associated NF-κB members, that in its turn results in an almost fully penetrant disease.…”

“…Human NFKB2 gene defects have been shown to be associated with B cell dysregulation in patients with common variable immunodeficiency (CVID) or combined immunodeficiency (CID) [4]. CVID with endocrinopathy and ectodermal dysplasia and CID phenotypes have been associated with NFKB2 C-terminus loss-of-function (LOF) mutations, which disrupt the phosphorylation and block the processing of p100 to p52, resulting in cytoplasmic retention of mutant p100 and reduction of p52 expression and nuclear translocation [4,5].…”

“…Human NFKB2 gene defects have been shown to be associated with B cell dysregulation in patients with common variable immunodeficiency (CVID) or combined immunodeficiency (CID) [4]. CVID with endocrinopathy and ectodermal dysplasia and CID phenotypes have been associated with NFKB2 C-terminus loss-of-function (LOF) mutations, which disrupt the phosphorylation and block the processing of p100 to p52, resulting in cytoplasmic retention of mutant p100 and reduction of p52 expression and nuclear translocation [4,5]. More recently, our group reported NFKB2 gain-of-function (GOF) mutations in CID patients with B cell lymphopenia, hypogammaglobulinemia, and multiple severe infections (i.e., Pneumocystis jirovecii pneumonitis, EBV, and CVM viremia, among others) with incomplete penetrance [6].…”

Plasma protein profiling reflects TH1-driven immune dysregulation in common variable immunodeficiency

“…Interestingly NFKB2 and NFKB1 haploinsufficiency have been associated with CVIDlike disease. 41,42 In addition to distinguishing the subgroups of patients with CVID, the plasma protein profiling also revealed aberrant expression that differed between the whole CVID group and the controls. A novel finding was the increased level of the B-cellattracting chemokine CXCL13 in patients with CVID.…”

Flow Cytometry-Based Protocols for the Analysis of Human Plasma Cell Differentiation

“…The recent developments of next-generation sequencing (NGS) methods, such as whole-exome sequencing (WES) and whole-genome sequencing (WGS), have led to the discovery of mutations in many other genes associated with primary immunodeficiencies ( 25 , 29 , 30 ). For example, mutations in several components of the NF-κB and the PI3K signaling pathways, which are activated after BCR signaling, were identified ( 31 – 41 ). Recently, mutations in IRF4 causing complete deficiency or haploinsufficiency have been linked to severe immune defects and predisposition to develop Whipple's disease as a result of infection with Tropheryma whipplei bacteria ( 42 , 43 ).…”