Expanding the PRAAS spectrum: De novo mutations of immunoproteasome subunit ß-type 10 in six infants with SCID-Omenn syndrome.

Mutations in proteasome ß-subunits or their chaperone and regulatory proteins are associated with proteasome-associated autoinflammatory disorders (PRAAS). We studied six unrelated infants with three de novo heterozygous missense variants in PSMB10, encoding the proteasome ß2i-subunit. Individuals presented with T-B-NK± severe combined immunodeficiency (SCID) and clinical features suggestive of Omenn syndrome, including diarrhea, alopecia, and desquamating erythematous rash. Remaining T cells had limited T cell receptor repertoires, a skewed memory phenotype, and an elevated CD4/CD8 ratio. Bone marrow examination indicated severely impaired B cell maturation with limited V(D)J recombination. All infants received an allogeneic stem cell transplant and exhibited a variety of severe inflammatory complications thereafter, with 2 peri-transplant and 2 delayed deaths. The single long-term transplant survivor showed evidence for genetic rescue through revertant mosaicism overlapping the affected PSMB10 locus. The identified variants (c.166G>C [p.Asp56His] and c.601G>A/c.601G>C [p.Gly201Arg]) were predicted in silico to profoundly disrupt 20S immunoproteasome structure through impaired ß-ring/ß-ring interaction. Our identification of PSMB10 mutations as a cause of SCID-Omenn syndrome reinforces the connection between PRAAS-related diseases and SCID.

Genotype-Phenotype Correlations in Chronic Granulomatous Disease: Insights From a Large National Cohort.

Neutrophils are the first line of defense against invading pathogens. Neutrophils execute and modulate immune responses by generating reactive oxygen species (ROS). Chronic Granulomatous Disease (CGD) is a primary immune deficiency disorder of phagocytes, caused by inherited mutations in the genes of the NADPH oxidase enzyme. These mutations lead to failure of ROS generation followed by recurrent bacterial and fungal infections, frequently associated with hyper-inflammatory manifestations. We report a multi-center cumulative experience in diagnosing and treating patients with CGD. From 1986 to 2021, 2,918 patients suffering from frequent infections were referred for neutrophil evaluation. Among them, 110 patients were diagnosed with CGD, 56 of Jewish ancestry, 48 of Arabic ancestry and 6 non-Jewish/non-Arabic. As opposed to other Western countries, the autosomal recessive (AR) CGD subtypes were predominant in Israel (71/110 patients). Thirty-nine patients had X-linked CGD, in most patients associated with severe infections (clinical severity score ≥3) and poor outcomes, presenting at a significantly earlier age than AR-CGD subtypes. The full spectrum of infections and hyper-inflammatory manifestations are described. Six patients had hypomorphic mutations with significantly milder phenotype, clinical severity score ≤2, and better outcomes. Hematopoietic stem cell transplantation was implemented in 39/110 patients (35.5%). Successful engraftment was achieved in 92%, with 82% long-term survival and 71% full clinical recovery. CGD is a complex disorder requiring a multi-professional team. Early identification of the genetic mutation is essential for prompt diagnosis, suitable management and prevention.

[CHARACTERIZATION OF THE ADAPTIVE IMMUNE REPERTOIRE USING NEXT GENERATION SEQUENCING: RECENT DISCOVERIES IN THE FIELD OF PRIMARY IMMUNODEFICIENCY, AND THE UPCOMING FUTURE].

INTRODUCTION: A powerful adaptive immune system, which includes cellular (T lymphocytes) and humoral (B lymphocytes) immunity, depends on its ability to recognize and protect against millions of different foreign antigens. It does so through an enormous diverse array of T-cell and B-cell receptors, collectively referred to as the adaptive immune repertoire. Using high-throughput sequencing as next generation sequencing (NGS) led to multiple breakthroughs in the field of molecular medicine. It has increased our ability to characterize the immune repertoire in primary immunodeficiency (PID) and to identify defects in diversification processes among other parameters as well. Human inborn errors of immunity represent a unique genotype-phenotype model that enable the study of critical genes' and proteins' role in disease and health. Recent studies regarding immune repertoire profiling of PID allowed us to better define genotype-phenotype correlations in diseases with wide clinical spectrum, the underlining patho-mechanism causing the specific genetic disease, the common features of similar diseases as well as the unique molecular signature for each genetic disease. Immune repertoire knowledge is an integral part of PID research, and aids in improving diagnosis and designing personalized treatment. Nevertheless, NGS has created some challenges that emphasize the need for technologies such as cloud-based platforms like Kusto, enabling scalable data analysis and the incorporation of artificial intelligence techniques.

Combined Immunodeficiency Caused by a Novel Nonsense Mutation in LCK.

Mutations affecting T-cell receptor (TCR) signaling typically cause combined immunodeficiency (CID) due to varying degrees of disturbed T-cell homeostasis and differentiation. Here, we describe two cousins with CID due to a novel nonsense mutation in LCK and investigate the effect of this novel nonsense mutation on TCR signaling, T-cell function, and differentiation. Patients underwent clinical, genetic, and immunological investigations. The effect was addressed in primary cells and LCK-deficient T-cell lines after expression of mutated LCK. RESULTS: Both patients primarily presented with infections in early infancy. The LCK mutation led to reduced expression of a truncated LCK protein lacking a substantial part of the kinase domain and two critical regulatory tyrosine residues. T cells were oligoclonal, and especially naïve CD4 and CD8 T-cell counts were reduced, but regulatory and memory including circulating follicular helper T cells were less severely affected. A diagnostic hallmark of this immunodeficiency is the reduced surface expression of CD4. Despite severely impaired TCR signaling mTOR activation was partially preserved in patients' T cells. LCK-deficient T-cell lines reconstituted with mutant LCK corroborated partially preserved signaling. Despite detectable differentiation of memory and effector T cells, their function was severely disturbed. NK cell cytotoxicity was unaffected. Residual TCR signaling in LCK deficiency allows for reduced, but detectable T-cell differentiation, while T-cell function is severely disturbed. Our findings expand the previous report on one single patient on the central role of LCK in human T-cell development and function.

Helper T cell immunity in humans with inherited CD4 deficiency.

CD4+ T cells are vital for host defense and immune regulation. However, the fundamental role of CD4 itself remains enigmatic. We report seven patients aged 5-61 years from five families of four ancestries with autosomal recessive CD4 deficiency and a range of infections, including recalcitrant warts and Whipple's disease. All patients are homozygous for rare deleterious CD4 variants impacting expression of the canonical CD4 isoform. A shorter expressed isoform that interacts with LCK, but not HLA class II, is affected by only one variant. All patients lack CD4+ T cells and have increased numbers of TCRαß+CD4-CD8- T cells, which phenotypically and transcriptionally resemble conventional Th cells. Finally, patient CD4-CD8- αß T cells exhibit intact responses to HLA class II-restricted antigens and promote B cell differentiation in vitro. Thus, compensatory development of Th cells enables patients with inherited CD4 deficiency to acquire effective cellular and humoral immunity against an unexpectedly large range of pathogens. Nevertheless, CD4 is indispensable for protective immunity against at least human papillomaviruses and Trophyrema whipplei.

Evolution of Gene Therapy for Inborn Errors of Immunity.

This Viewpoint reviews the history and current state of gene therapy for inborn errors of immunity.