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Deficiency of Adenosine Deaminase 2 (DADA2) patients presenting with primary immunodeficiency are at risk of uncontrolled EBV infection and secondary malignancies including EBV-related lymphoproliferative disorders (LPD). This paper describes the first case of EBV related diffuse large B-cell lymphoma in a patient with DADA2 and uncontrolled EBV infection. Consideration should be given to monitoring for EBV viraemia and to preventative EBV specific therapy in DADA2 and patients with at risk primary immunodeficiencies. A type I interferon (IFN) gene signature is associated with DADA2 though its association with immune dysregulation is unclear. [ABSTRACT FROM AUTHOR]

Purpose: Inborn errors of the IL-17A/F-responsive pathway lead to chronic mucocutaneous candidiasis (CMC) as a predominant clinical phenotype, without other significant clinical manifestations apart from mucocutaneous staphylococcal diseases. Among inborn errors affecting IL-17-dependent immunity, autosomal recessive (AR) IL-17RC deficiency is a rare disease with only three kindreds described to date. The lack of an in vitro functional evaluation system of IL17RC variants renders its diagnosis difficult. We sought to characterize a 7-year-old Japanese girl with CMC carrying a novel homozygous duplication variant of IL17RC and establish a simple in vitro system to evaluate the impact of this variant. Methods: Flow cytometry, qPCR, RNA-sequencing, and immunoblotting were conducted, and an IL17RC-knockout cell line was established for functional evaluation. Results: The patient presented with oral and mucocutaneous candidiasis without staphylococcal diseases since the age of 3 months. Genetic analysis showed that the novel duplication variant (Chr3: 9,971,476-9,971,606 dup (+131bp)) involving exon 13 of IL17RC results in a premature stop codon (p.D457Afs*16 or p.D457Afs*17). Our functional evaluation system revealed this duplication to be loss-of-function and enabled discrimination between loss-of-function and neutral IL17RC variants. The lack of response to IL-17A by the patient’s SV40-immortalized fibroblasts was restored by introducing WT-IL17RC, suggesting that the genotype identified is responsible for her clinical phenotype. Conclusions: The clinical and cellular phenotype of the current case of AR IL-17RC deficiency supports a previous report on this rare disorder. Our newly established evaluation system will be useful for the diagnosis of AR IL-17RC deficiency, providing accurate validation of unknown IL17RC variants. [ABSTRACT FROM AUTHOR]

Rare, biallelic loss-of-function mutations in DOCK8 result in a combined immune deficiency characterized by severe and recurrent cutaneous infections, eczema, allergies, and susceptibility to malignancy, as well as impaired humoral and cellular immunity and hyper-IgE. The advent of next-generation sequencing technologies has enabled the rapid molecular diagnosis of rare monogenic diseases, including inborn errors of immunity. These advances have resulted in the implementation of gene-guided treatments, such as hematopoietic stem cell transplant for DOCK8 deficiency. However, putative disease-causing variants revealed by next-generation sequencing need rigorous validation to demonstrate pathogenicity. Here, we report the eventual diagnosis of DOCK8 deficiency in a consanguineous family due to a novel homozygous intronic deletion variant that caused aberrant exon splicing and subsequent loss of expression of DOCK8 protein. Remarkably, the causative variant was not initially detected by clinical whole-genome sequencing but was subsequently identified and validated by combining advanced genomic analysis, RNA-seq, and flow cytometry. This case highlights the need to adopt multipronged confirmatory approaches to definitively solve complex genetic cases that result from variants outside protein-coding exons and conventional splice sites. [ABSTRACT FROM AUTHOR]

Variants in MAGT1 have been identified as the cause of an immune deficiency termed X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection and neoplasia (XMEN) disease. Here, we describe 2 cases of XMEN disease due to novel mutations in MAGT1, one of whom presented with classical features of XMEN disease and another who presented with a novel phenotype including probable CNS vasculitis, HHV-8 negative multicentric Castelman disease and severe molluscum contagiosum, thus highlighting the clinical diversity that may be seen in this condition. Peripheral blood immunophenotyping of these 2 patients, together with an additional 4 XMEN patients, revealed reduced NKG2D expression, impaired CD28 expression on CD8+ T cells, CD4+ T cell lymphopenia, an inverted CD4:CD8 ratio and decreased memory B cells. In addition, we showed for the first time alterations to the CD8+ T cell memory compartment, reduced CD56hi NK cells, MAIT and iNKT cells, as well as compromised differentiation of naïve CD4+ T cells into IL-21-producing Tfh-type cells in vitro. Both patients were treated with supplemental magnesium with limited benefit. However, one patient has undergone allogeneic haematopoietic stem cell transplant, with full donor chimerism and immune reconstitution. These results expand our understanding of the clinical and immunological phenotype in XMEN disease, adding to the current literature, which we further discuss here. [ABSTRACT FROM AUTHOR]

Advanced genomic technologies such as whole exome or whole genome sequencing have improved diagnoses and disease outcomes for individuals with genetic diseases. Yet, variants of unknown significance (VUS) require rigorous validation to establish disease causality or modification, or to exclude them from further analysis. Here, we describe a young individual of Polynesian ancestry who in the first 13 mo of life presented with SARS-CoV-2 pneumonia, severe enterovirus meningitis and adenovirus gastroenteritis, and severe adverse reaction to MMR vaccination. Genomic analysis identified a previously reported pathogenic homozygous variant in IFNAR1 (c.1156G > T, p.Glu386* LOF), which is common in Western Polynesia. Moreover, a new and putatively deleterious canonical splice site variant in DOCK8 was also found in homozygosity (c.3234 + 2T > C). This DOCK8 variant is common in Polynesians and other under-represented ancestries in large genomic databases. Despite in silico bioinformatic predictions, extensive in vitro and ex vivo analysis revealed the DOCK8 variant likely be neutral. Thus, our study reports a novel case of IFNAR1 deficiency, but also highlights the importance of functional validation of VUS, including those predicted to be deleterious, and the pressing need to expand our knowledge of the genomic architecture and landscape of under-represented populations and ancestries., (© 2024. The Author(s).)

B cells and their secreted antibodies are fundamental for host-defense against pathogens. The generation of high-affinity class switched antibodies results from both somatic hypermutation (SHM) of the immunoglobulin (Ig) variable region genes of the B-cell receptor and class switch recombination (CSR) which alters the Ig heavy chain constant region. Both of these processes are initiated by the enzyme activation-induced cytidine deaminase (AID), encoded by AICDA. Deleterious variants in AICDA are causal of hyper-IgM syndrome type 2 (HIGM2), a B-cell intrinsic primary immunodeficiency characterised by recurrent infections and low serum IgG and IgA levels. Biallelic variants affecting exons 2, 3 or 4 of AICDA have been identified that impair both CSR and SHM in patients with autosomal recessive HIGM2. Interestingly, B cells from patients with autosomal dominant HIGM2, caused by heterozygous variants (V186X, R190X) located in AICDA exon 5 encoding the nuclear export signal (NES) domain, show abolished CSR but variable SHM. We herein report the immunological and functional phenotype of two related patients presenting with common variable immunodeficiency who were found to have a novel heterozygous variant in AICDA (L189X). This variant led to a truncated AID protein lacking the last 10 amino acids of the NES at the C-terminal domain. Interestingly, patients' B cells carrying the L189X variant exhibited not only greatly impaired CSR but also SHM in vivo, as well as CSR and production of IgG and IgA in vitro. Our findings demonstrate that the NES domain of AID can be essential for SHM, as well as for CSR, thereby refining the correlation between AICDA genotype and SHM phenotype as well as broadening our understanding of the pathophysiology of HIGM disorders., (© 2024. The Author(s).)