Fatal Enteroviral Encephalitis in a Patient with Common Variable Immunodeficiency Harbouring a Novel Mutation in NFKB2

Clinical, Immunological, and Genetic Features in Patients with NFKB1 and NFKB2 Mutations: a Systematic Review

BACKGROUND

Inborn errors of immunity (IEIs) encompass various diseases with diverse clinical and immunological symptoms. Determining the genotype-phenotype of different variants in IEI entity precisely is challenging, as manifestations can be heterogeneous even in patients with the same mutated gene.

OBJECTIVE

In the present study, we conducted a systematic review of patients recorded with NFKB1 and NFKB2 mutations, two of the most frequent monogenic IEIs.

METHODS

The search for relevant literature was conducted in databases including Web of Science, PubMed, and Scopus. Information encompassing demographic, clinical, immunological, and genetic data was extracted from cases reported with mutations in NFKB1 and NFKB2. The comprehensive features of manifestations in patients were described, and a comparative analysis of primary characteristics was conducted between individuals with NFKB1 loss of function (LOF) and NFKB2 (p52-LOF/IκBδ-gain of function (GOF)) variants.

RESULTS

A total of 397 patients were included in this study, 257 had NFKB1 mutations and 140 had NFKB2 mutations. There were 175 LOF cases in NFKB1 and 122 p52LOF/IκBδGOF cases in NFKB2 pivotal groups with confirmed functional implications. NFKB1LOF and p52LOF/IκBδGOF predominant cases (81.8% and 62.5% respectively) initially presented with a CVID-like phenotype. Patients with NFKB1LOF variants often experienced hematologic autoimmune disorders, whereas p52LOF/IκBδGOF patients were more susceptible to other autoimmune diseases. Viral infections were markedly higher in p52LOF/IκBδGOF cases compared to NFKB1LOF (P-value < 0.001). NFKB2 (p52LOF/IκBδGOF) patients exhibited a greater prevalence of ectodermal dysplasia and pituitary gland involvement than NFKB1LOF patients. Most NFKB1LOF and p52LOF/IκBδGOF cases showed low CD19 + B cells, with p52LOF/IκBδGOF having more cases of this type. Low memory B cells were more common in p52LOF/IκBδGOF patients.

CONCLUSIONS

Patients with NFKB2 mutations, particularly p52LOF/IκBδGOF, are at higher risk of viral infections, pituitary gland involvement, and ectodermal dysplasia compared to patients with NFKB1LOF mutations. Genetic testing is essential to resolve the initial complexity and confusion surrounding clinical and immunological features. Emphasizing the significance of functional assays in determining the probability of correlations between mutations and immunological and clinical characteristics of patients is crucial.

Autoantibodies against type I IFNs in humans with alternative NF-κB pathway deficiency

Patients with autoimmune polyendocrinopathy syndrome type 1 (APS-1) caused by autosomal recessive AIRE deficiency produce autoantibodies that neutralize type I interferons (IFNs)1,2, conferring a predisposition to life-threatening COVID-19 pneumonia3. Here we report that patients with autosomal recessive NIK or RELB deficiency, or a specific type of autosomal-dominant NF-κB2 deficiency, also have neutralizing autoantibodies against type I IFNs and are at higher risk of getting life-threatening COVID-19 pneumonia. In patients with autosomal-dominant NF-κB2 deficiency, these autoantibodies are found only in individuals who are heterozygous for variants associated with both transcription (p52 activity) loss of function (LOF) due to impaired p100 processing to generate p52, and regulatory (IκBδ activity) gain of function (GOF) due to the accumulation of unprocessed p100, therefore increasing the inhibitory activity of IκBδ (hereafter, p52LOF/IκBδGOF). By contrast, neutralizing autoantibodies against type I IFNs are not found in individuals who are heterozygous for NFKB2 variants causing haploinsufficiency of p100 and p52 (hereafter, p52LOF/IκBδLOF) or gain-of-function of p52 (hereafter, p52GOF/IκBδLOF). In contrast to patients with APS-1, patients with disorders of NIK, RELB or NF-κB2 have very few tissue-specific autoantibodies. However, their thymuses have an abnormal structure, with few AIRE-expressing medullary thymic epithelial cells. Human inborn errors of the alternative NF-κB pathway impair the development of AIRE-expressing medullary thymic epithelial cells, thereby underlying the production of autoantibodies against type I IFNs and predisposition to viral diseases.

Disseminated Coccidioidomycosis as the First Presentation of a C-Terminal NFKB2 Pathogenic Variant: A Case Report and Review of the Literature

INTRODUCTION

Although most cases of coccidioidomycosis are subclinical or self-limited respiratory disease, 1% lead to extrathoracic dissemination and become fatal, especially in patients with an associated immunodeficiency. Up to 30%-50% of patients with defects in cell-mediated immunity, those with AIDS and recipients of solid-organ transplants, may develop disseminated coccidioidomycosis (DC). Within the primary immunodeficiencies, an uncommon group is caused by C-terminal NFKB2 pathogenic variants.

MATERIALS AND METHODS

We performed a literature search of core databases. Written informed consent for the study and for publication was obtained.

CASE PRESENTATION

A 7-year-old Mexican girl, eldest of 3 sisters, no relevant family history, and a history of recurrent upper respiratory infections and alopecia totalis was admitted with DC involving pulmonary, soft tissue, skin, bone and joint compromise. The immunodeficiency assessment showed low IgM and NK cells. We found an NFKB2 de novo heterozygous nonsense mutation of c.2611C>T (p.Gln871*). She was treated with liposomal amphotericin B and itraconazole with surgical debridement. The clinical phenotype of this primary immunodeficiency is characterized by antibody deficiency and associated broncho-pulmonary predisposition to infection, but moreover also opportunistic infections and autoimmunity, most recognizable alopecia and adrenocorticotropic hormone-deficiency. After 1 year of her discharge, she continues under surveillance with antifungal therapy with itraconazole and replacement intravenous immunoglobulin until today.

CONCLUSION

This is the first case report of DC in a patient with an NFKB2 pathogenic variant and it illustrates the importance of screening for primary immunodeficiencies in patients with disseminated fungal infections.

Inborn errors of TLR3- or MDA5-dependent type I IFN immunity in children with enterovirus rhombencephalitis

Enterovirus (EV) infection rarely results in life-threatening infection of the central nervous system. We report two unrelated children with EV30 and EV71 rhombencephalitis. One patient carries compound heterozygous TLR3 variants (loss-of-function F322fs2* and hypomorphic D280N), and the other is homozygous for an IFIH1 variant (loss-of-function c.1641+1G>C). Their fibroblasts respond poorly to extracellular (TLR3) or intracellular (MDA5) poly(I:C) stimulation. The baseline (TLR3) and EV-responsive (MDA5) levels of IFN-β in the patients’ fibroblasts are low. EV growth is enhanced at early and late time points of infection in TLR3- and MDA5-deficient fibroblasts, respectively. Treatment with exogenous IFN-α2b before infection renders both cell lines resistant to EV30 and EV71, whereas post-infection treatment with IFN-α2b rescues viral susceptibility fully only in MDA5-deficient fibroblasts. Finally, the poly(I:C) and viral phenotypes of fibroblasts are rescued by the expression of WT TLR3 or MDA5. Human TLR3 and MDA5 are critical for cell-intrinsic immunity to EV, via the control of baseline and virus-induced type I IFN production, respectively.

Characteristics and therapy of enteroviral encephalitis: case report and systematic literature review

OBJECTIVES

Enterovirus (EV) is a frequent cause of encephalitis. The optimal therapeutic approach remains a matter of debate. We present the case of an immunosuppressed patient with EV encephalitis treated successfully with intravenous immunoglobulin (IVIG) and report the results of a systematic review on the characteristics of EV encephalitis, as well as the safety and efficacy of IVIG therapy.

METHODS

A systematic review was conducted using the PubMed, Cochrane Database, BIOSIS Previews, and ClinicalTrials.gov databases to identify all reports on patients with EV encephalitis as of December 31, 2020. The main outcomes assessed were the efficacy and safety of the respective therapeutic approach.

RESULTS

A total of 73 articles were included: one prospective trial, one retrospective and prospective case series, one purely retrospective case series, and 70 case reports. The case reports included a total of 101 patients. Immunosuppressed patients were at higher risk of contracting EV encephalitis and experiencing a fatal course. Hypogammaglobulinaemia particularly predisposes to EV disease, even with a moderate reduction in serum IgG levels. IVIG therapy in the immunosuppressed may confer a survival advantage.

CONCLUSIONS

IVIG therapy is rarely associated with severe adverse events and may be considered in immunosuppressed patients with EV encephalitis. Future trials should investigate the optimal IVIG dosing and route of application, the benefit of antibody-enriched IVIG preparations, and the serum immunoglobulin level that should trigger prophylactic replacement.

Peripheral B Cell Deficiency and Predisposition to Viral Infections: The Paradigm of Immune Deficiencies

In the era of COVID-19, understanding how our immune system responds to viral infections is more pertinent than ever. Immunodeficiencies with very low or absent B cells offer a valuable model to study the role of humoral immunity against these types of infection. This review looks at the available evidence on viral infections in patients with B cell alymphocytosis, in particular those with X-linked agammaglobulinemia (XLA), Good’s syndrome, post monoclonal-antibody therapy and certain patients with Common Variable Immune Deficiency (CVID). Viral infections are not as infrequent as previously thought in these conditions and individuals with very low circulating B cells seem to be predisposed to an adverse outcome. Particularly in the case of SARS-CoV2 infection, mounting evidence suggests that peripheral B cell alymphocytosis is linked to a poor prognosis.

Nfkb2 variants reveal a p100-degradation threshold that defines autoimmune susceptibility

NF-κB2/p100 (p100) is an inhibitor of κB (IκB) protein that is partially degraded to produce the NF-κB2/p52 (p52) transcription factor. Heterozygous NFKB2 mutations cause a human syndrome of immunodeficiency and autoimmunity, but whether autoimmunity arises from insufficiency of p52 or IκB function of mutated p100 is unclear. Here, we studied mice bearing mutations in the p100 degron, a domain that harbors most of the clinically recognized mutations and is required for signal-dependent p100 degradation. Distinct mutations caused graded increases in p100-degradation resistance. Severe p100-degradation resistance, due to inheritance of one highly degradation-resistant allele or two subclinical alleles, caused thymic medullary hypoplasia and autoimmune disease, whereas the absence of p100 and p52 did not. We inferred a similar mechanism occurs in humans, as the T cell receptor repertoires of affected humans and mice contained a hydrophobic signature of increased self-reactivity. Autoimmunity in autosomal dominant NFKB2 syndrome arises largely from defects in nonhematopoietic cells caused by the IκB function of degradation-resistant p100.

There is no gene for CVID - novel monogenetic causes for primary antibody deficiency

'There is no gene for fate' (citation from the movie 'GATTACA') - and there is no gene for CVID. Common Variable ImmunoDeficiency (CVID) is the most prevalent primary immunodeficiency in humans. CVID is characterized by an increased susceptibility to infections, hypogammaglobulinemia, reduced switched memory B cell numbers in peripheral blood and a defective response to vaccination, often complicated by autoimmune and autoinflammatory conditions. However, as soon as a genetic diagnosis has been made in a patient with CVID, the diagnosis must be changed to the respective genetic cause (www.esid.org). Therefore, there are genetic causes for primary antibody deficiencies, but not for CVID. Primary antibody deficiencies (PADs) are a heterogeneous group of disorders. Several attempts have been made to gain further insights into the pathogenesis of PAD, using unbiased approaches such as whole exome or genome sequencing. Today, in just about 35% of cases with PAD, monogenic mutations (including those in the gene TNFRSF13B) can be identified in a set of 68 genes [1^•]. These mutations occur either sporadically or are inherited and do explain an often complex phenotype. In our review, we not only discuss gene defects identified in PAD patients previously diagnosed with CVID and/or CVID-like disorders such as IKZF1, CTNNBL1, TNFSF13 and BACH2, but also genetic defects which were initially described in non-CVID patients but have later also been observed in patients with PAD such as PLCG2, PIK3CG, PMS2, RNF31, KMT2D, STAT3. We also included interesting genetic defects in which the pathophysiology suggests a close relation to other known defects of the adaptive immune response, such as DEF6, SAMD9 and SAMD9L, and hence a CVID-like phenotype may be observed in the future. However, alternative mechanisms most likely add to the development of an antibody-deficient phenotype, such as polygenic origins, epigenetic changes, and/or environmental factors.

Multiplexed Functional Assessment of Genetic Variants in CARD11

Genetic testing has increased the number of variants identified in disease genes, but the diagnostic utility is limited by lack of understanding variant function. CARD11 encodes an adaptor protein that expresses dominant-negative and gain-of-function variants associated with distinct immunodeficiencies. Here, we used a "cloning-free" saturation genome editing approach in a diploid cell line to simultaneously score 2,542 variants for decreased or increased function in the region of CARD11 associated with immunodeficiency. We also described an exon-skipping mechanism for CARD11 dominant-negative activity. The classification of reported clinical variants was sensitive (94.6%) and specific (88.9%), which rendered the data immediately useful for interpretation of seven coding and splicing variants implicated in immunodeficiency found in our clinic. This approach is generalizable for variant interpretation in many other clinically actionable genes, in any relevant cell type.

Endocrine Disorders Are Prominent Clinical Features in Patients With Primary Antibody Deficiencies

Background: Primary antibody deficiencies (PADs) and anterior pituitary dysfunction are both rare conditions. However, recent studies have remarkably reported the occurrence of anterior pituitary dysfunction in PAD patients. Methods: In this cross-sectional, single-center study we evaluated the prevalence of endocrine disorders in adult PAD patients. Our study focused on common variable immunodeficiency (CVID), immunoglobulin G (IgG) subclass deficiency (IgGSD), and specific anti-polysaccharide antibody deficiency (SPAD). We assessed hormone levels, performed provocative tests and genetic testing in a subset of patients by direct sequencing of the nuclear factor kappa beta subunit 2 (NFKB2) gene and primary immunodeficiency (PID) gene panel testing by whole exome sequencing (WES). Results: Our results demonstrated that one out of 24 IgGSD/SPAD patients had secondary hypothyroidism and three out of 9 men with IgGSD/SPAD had secondary hypogonadism. Premature ovarian failure was observed in four out of 9 women with CVID and primary testicular failure in one out of 15 men with CVID. In two out of 26 CVID patients we found partial adrenal insufficiency (AI) and in one out of 18 patients with IgGSD/SPAD secondary AI was found. Moreover, in one out of 23 patients with CVID and in two out of 17 patients with IgGSD/SPAD severe growth hormone deficiency (GHD) was found, while one patient with IgGSD/SPAD showed mild GHD. Combined endocrine disorders were detected in two women with CVID (either partial secondary AI or autoimmune thyroiditis with primary hypogonadism) and in three men with IgGSD/SPAD (two with either mild GHD or secondary hypothyroidism combined with secondary hypogonadism, and one man with secondary AI and severe GHD). Genetic testing in a subset of patients did not reveal pathogenic variants in NFKB2 or other known PID-associated genes. Conclusion: This is the first study to describe a high prevalence of both anterior pituitary and end-organ endocrine dysfunction in adult PAD patients. As these endocrine disorders may cause considerable health burden, assessment of endocrine axes should be considered in PAD patients.