Severe combined immunodeficiency--an update

Novel Synonymous Variant in IL7R Causes Preferential Expression of the Soluble Isoform

PURPOSE

The interleukin-7 receptor (IL-7R) is primarily expressed on lymphoid cells and plays a crucial role in the development, proliferation, and survival of T cells. Autosomal recessive mutations that disrupt IL-7Rα chain expression give rise to a severe combined immunodeficiency (SCID), which is characterized by lymphopenia and a T-B+NK+ phenotype. The objective here was to diagnose two siblings displaying the T-B+NK+ SCID phenotype as initial clinical genetic testing did not detect any variants in known SCID genes.

METHODS

Whole genome sequencing (WGS) was utilized to identify potential variants causing the SCID phenotype. Splicing prediction tools were employed to assess the deleterious impact of the mutation. Polymerase Chain Reaction (PCR), Sanger sequencing, flow cytometry, and ELISA were then used to validate the pathogenicity of the detected mutation.

RESULTS

We discovered a novel homozygous synonymous mutation in the IL7R gene. Our functional studies indicate that this variant is pathogenic, causing exon 6, which encodes the transmembrane domain, to be preferentially spliced out.

CONCLUSION

In this study, we identified a novel rare synonymous mutation causing a loss of IL-7Rα expression at the cellular membrane. This case demonstrates the value of reanalyzing genetic data based on the clinical phenotype and highlights the significance of functional studies in determining the pathogenicity of genetic variants.

Uncertainties experienced by parents of children diagnosed with severe combined immunodeficiency through newborn screening

Individuals with severe combined immunodeficiency (SCID), a group of rare, genetic conditions, are at risk for life-threatening illnesses unless diagnosed and treated early. Even after early identification through newborn screening, parents of children with SCID embark on a complex journey marked by a variety of informational and emotional support needs. This paper explored the types of uncertainties experienced by parents of a child with SCID diagnosed through newborn screening. We conducted semi-structured interviews with 26 parents to discuss the types of uncertainty experienced, including scientific, practical, personal, and existential. Each interview was recorded, transcribed, and coded. Using deductive and inductive content analysis, we describe the type of uncertainty experienced across each stage of the SCID journey. We found that uncertainties in the SCID journey were chronic and multifaceted. Some uncertainties were more prominent at certain points of the journey whereas others spanned multiple stages. Parents expressed a variety of negative emotional reactions to uncertainty, from anxiety, worry, and fear, to doubt, guilt, or grief, and even anger, frustration, and depression. The results speak to the need for healthcare providers to prepare parents for the SCID journey by providing resources to help manage and cope with uncertainty.

Janus Kinase 3 (JAK3): A Critical Conserved Node in Immunity Disrupted in Immune Cell Cancer and Immunodeficiency

The Janus kinase (JAK) family is a small group of protein tyrosine kinases that represent a central component of intracellular signaling downstream from a myriad of cytokine receptors. The JAK3 family member performs a particularly important role in facilitating signal transduction for a key set of cytokine receptors that are essential for immune cell development and function. Mutations that impact JAK3 activity have been identified in a number of human diseases, including somatic gain-of-function (GOF) mutations associated with immune cell malignancies and germline loss-of-function (LOF) mutations associated with immunodeficiency. The structure, function and impacts of both GOF and LOF mutations of JAK3 are highly conserved, making animal models highly informative. This review details the biology of JAK3 and the impact of its perturbation in immune cell-related diseases, including relevant animal studies.

From variant of uncertain significance to likely pathogenic in two siblings with atypical RAG2 Deficiency: a case report and review of the literature

BACKGROUND

Severe combined immunodeficiencies (SCIDs) are hereditary disorders characterized by impaired T and B cell function, resulting in significant immune system dysfunction. Recombination-activating gene (RAG) mutations account for a substantial proportion of SCID cases. Here, we present two sibling cases of SCID caused by a novel RAG2 gene mutation.

CASE PRESENTATION

The index case was an 8-year-old boy who had a history of recurring infections. After a comprehensive immunological workup, the initial diagnosis of agammaglobulinemia was revised to combined immunodeficiency (CID). The patient underwent hematopoietic stem cell transplantation (HSCT) but succumbed to cytomegalovirus (CMV) infection. His brother, a 4-month-old boy, presented with CMV chorioretinitis. Leaky SCID was diagnosed based on genetic tests and immunological findings. The patient received appropriate treatment and was considered for HSCT. Both siblings had a homozygous RAG2 gene variant, with the first case classified as a variant of uncertain significance (VUS). The presence of the same mutation in the second brother, and the clinical phenotype, supports considering the mutation as likely pathogenic.

CONCLUSIONS

This case report highlights a novel RAG2 gene mutation associated with CID. The classification of a VUS may evolve with accumulating evidence, and additional studies are warranted to establish its pathogenicity. Proper communication between genetic counselors and immunologists, accurate documentation of patient information, increased public awareness, and precise utilization of genetic techniques are essential for optimal patient management.

A novel 268 kb deletion combined with a splicing variant in IL7R causes of severe combined immunodeficiency in a Chinese family: a case report

BACKGROUND

Severe combined immunodeficiency (SCID) is a group of fatal primary immunodeficiencies characterized by the severe impairment of T-cell differentiation. IL7R deficiency is a rare form of SCID that usually presents in the first months of life with severe and opportunistic infections, failure to thrive, and a high risk of mortality unless treated. Although recent improvements in early diagnosis have been achieved through newborn screening, few IL7R-related SCID patients had been reported in the Chinese population.

CASE PRESENTATION

Here, we retrospectively analyzed a case of SCID in a 5-month-old girl with symptoms, including severe T-cell depletion, recurrent fever, oral ulcers, pneumonia, hepatosplenomegaly, bone marrow hemophagocytosis, and bacterial and viral infections. Whole-exome sequencing (WES), quantitative PCR (qPCR), and chromosome microarray analysis (CMA) were performed to identify the patient's genetic etiology. We identified a 268 kb deletion and a splicing variant, c.221 + 1G > A, in the proband. These two variants of IL7R were inherited from the father and mother.

CONCLUSIONS

To our knowledge, this is the first report of whole IL7R gene deletion in combination with a pathogenic splicing variant in a patient with SCID. This deletion also expands the pathogenic variation spectrum of SCID caused by IL7R. The incorporation of exome-based copy number variant analysis makes WES a powerful molecular diagnostic technique for the clinical diagnosis of pediatric patients.

CRISPR-Cas9 engineering of the RAG2 locus via complete coding sequence replacement for therapeutic applications

RAG2-SCID is a primary immunodeficiency caused by mutations in Recombination-activating gene 2 (RAG2), a gene intimately involved in the process of lymphocyte maturation and function. ex-vivo manipulation of a patient's own hematopoietic stem and progenitor cells (HSPCs) using CRISPR-Cas9/rAAV6 gene editing could provide a therapeutic alternative to the only current treatment, allogeneic hematopoietic stem cell transplantation (HSCT). Here we show an innovative RAG2 correction strategy that replaces the entire endogenous coding sequence (CDS) for the purpose of preserving the critical endogenous spatiotemporal gene regulation and locus architecture. Expression of the corrective transgene leads to successful development into CD3+TCRαβ+ and CD3+TCRγδ+ T cells and promotes the establishment of highly diverse TRB and TRG repertoires in an in-vitro T-cell differentiation platform. Thus, our proof-of-concept study holds promise for safer gene therapy techniques of tightly regulated genes.

A novel loss of function mutation in the PHD domain of the RAG2 gene, affecting zinc-binding affinity

BACKGROUND

Severe combined immune deficiencies (SCIDs) are genetically heterogeneous disorders that lead to the absence or malfunction of adaptive immune cells, including T- and B-cells. Pathogenic variants in the RAG2 gene are associated with this disease.

METHODS

A couple with consanguineous marriage from the Iranian-Azeri-Turkish ethnic group was referred to the genetic lab. Two children of this family died due to SCID disease with symptoms of skin granulomas, lack of developed T- and B-cells, and intact NK cells. To infer their genotypes, DNA samples obtained from the parents were subjected to whole-exome sequencing (WES).

RESULTS

WES data analysis revealed that both parents were carriers of a pathogenic variant, NC_000011.10 (NM_000536.4):c.1268G > C, in the RAG2 gene. This variant was absent in our cohort of 400 healthy individuals from the same ethnic group. To gain insight into the consequence of the variant on the protein function, further analysis was performed by applying bioinformatics tools. This study revealed that the replacement of cysteine with serine at the zinc-binding domain diminished the domain's affinity to zinc ion, resulting in the loss of the mutant protein's ability to bind to the recombination signal sequence (RSS). The formation of the RAG2-RSS complex is vital for T- and B-cell development.

CONCLUSION

The identification of a novel pathogenic variant, c.1268G > C, revealed that this variant in the zinc-binding domain diminished the affinity of the zinc ion to the mutant protein and consequently led to the loss of its ability to bind to the RSS.

Generation of inactivated IL2RG and RAG1 monkeys with severe combined immunodeficiency using base editing

Severe combined immunodeficiency (SCID) encompasses a range of inherited disorders that lead to a profound deterioration of the immune system. Among the pivotal genes associated with SCID, RAG1 and IL2RG play crucial roles. IL2RG is essential for the development, differentiation, and functioning of T, B, and NK cells, while RAG1 critically contributes to adaptive immunity by facilitating V(D)J recombination during the maturation of lymphocytes. Animal models carrying mutations in these genes exhibit notable deficiencies in their immune systems. Non-human primates (NHPs) are exceptionally well-suited models for biomedical research due to their genetic and physiological similarities to humans. Cytosine base editors (CBEs) serve as powerful tools for precisely and effectively modifying single-base mutations in the genome. Their successful implementation has been demonstrated in human cells, mice, and crop species. This study outlines the creation of an immunodeficient monkey model by deactivating both the IL2RG and RAG1 genes using the CBE4max system. The base-edited monkeys exhibited a severely compromised immune system characterized by lymphopenia, atrophy of lymphoid organs, and a deficiency of mature T cells. Furthermore, these base-edited monkeys were capable of hosting and supporting the growth of human breast cancer cells, leading to tumor formation. In summary, we have successfully developed an immunodeficient monkey model with the ability to foster tumor growth using the CBE4max system. These immunodeficiency monkeys show tremendous potential as valuable tools for advancing biomedical and translational research.

Guardians of Immunity: Advances in Primary Immunodeficiency Disorders and Management

Primary immunodeficiency disorders (PIDs) are a heterogeneous group of genetic conditions profoundly impacting immune function. The investigation spans various PID categories, offering insights into their distinct pathogenic mechanisms and clinical manifestations. Within the adaptive immune system, B-cell, T-cell, and combined immunodeficiencies are dissected, emphasizing their critical roles in orchestrating effective immune responses. In the realm of the innate immune system, focus is directed toward phagocytes and complement deficiencies, underscoring the pivotal roles of these components in initial defense against infections. Furthermore, the review delves into disorders of immune dysregulation, encompassing hemophagocytic lymphohistiocytosis (HLH), autoimmune lymphoproliferative syndrome (ALPS), immune dysregulation, polyendocrinopathy, enteropathy, and X-linked(IPEX), and autoimmunity polyendocrinopathy candidiasis-ectodermal dystrophy(APECED), elucidating the intricate interplay between immune tolerance and autoimmunity prevention. Diagnostic strategies for PIDs are explored, highlighting advancements in genetic and molecular techniques that enable precise identification of underlying genetic mutations and alterations in immune function. We have also outlined treatment modalities for PIDs, which often entail a multidisciplinary approach involving immunoglobulin replacement, antimicrobial prophylaxis, and, in select cases, hematopoietic stem cell transplantation. Emerging therapies, including gene therapy, hold promise for targeted interventions. In essence, this review encapsulates the complexity of PIDs, emphasizing the critical importance of early diagnosis and tailored therapeutic interventions. As research advances, a clearer understanding of these disorders emerges, fostering optimism for enhanced patient care and management in the future.

Immune Reconstitution Inflammatory Syndrome After Hematopoietic Stem Cell Transplantation in a FOXN1 -deficient Patient

The FOXN1 gene mutation is a unique disorder that causes the nude severe combined immunodeficiency phenotype. In patients with severe combined immunodeficiency, hematopoietic stem cell transplantation (HSCT) is life-saving if performed earlier. Thymic transplantation is the curative treatment for FOXN1 deficiency because the main pathology is thymic stromal changes. In this report, we describe the clinical features of a Turkish patient with a homozygous FOXN1 mutation treated with HSCT from his human leukocyte antigen-matched sibling. On follow-up, he showed Bacille Calmette Guerin adenitis and was evaluated as having immune reconstitution inflammatory syndrome. By presenting our patient, we aimed to draw attention to the development of HSCT and subsequent immune reconstitution inflammatory syndrome as a treatment option in patients with FOXN1 deficiency.

Severe Combined Immunodeficiency-Classification, Microbiology Association and Treatment

Severe combined immunodeficiency (SCID) is a primary inherited immunodeficiency disease that presents before the age of three months and can be fatal. It is usually due to opportunistic infections caused by bacteria, viruses, fungi, and protozoa resulting in a decrease in number and impairment in the function of T and B cells. Autosomal, X-linked, and sporadic forms exist. Evidence of recurrent opportunistic infections and lymphopenia very early in life should prompt immunological investigation and suspicion of this rare disorder. Adequate stem cell transplantation is the treatment of choice. This review aimed to provide a comprehensive approach to the microorganisms associated with severe combined immunodeficiency (SCID) and its management. We describe SCID as a syndrome and summarize the different microorganisms that affect children and how they can be investigated and treated.

Peripheral control of psychiatric disorders: Focus on OCD. Are we there yet?

"We are all in this together" - we often hear this phrase when we want to flag up a problem that is not for a single individual but concerns us all. A similar reflection has been recently made in the field of mental disorders where brain-centric scientists have started to zoom out their brain-focused graphical representations of the mechanisms regulating psychiatric diseases to include other organs or mediators that did not belong historically to the world of neuroscience. The brain itself - that has long been seen as a master in command secluded in its fortress (the blood brain barrier), has now become a collection of Airbnb(s) where all sorts of cells come in and out and sometimes even rearrange the furniture! Under this new framework of reference, mental disorders have become multisystem pathologies where different biological systems - not just the CNS -contribute 'all together' to the development and severity of the disease. In this narrative review article, we will focus on one of the most popular biological systems that has been shown to influence the functioning of the CNS: the immune system. We will specifically highlight the two main features of the immune system and the CNS that we think are important in the context of mental disorders: plasticity and memory.

A variant of RAG1 gene identified in severe combined immunodeficiency: a case report

BACKGROUND

The recombination-activating gene 1 (RAG1) protein is essential for the V (variable)-D (diversity)-J (joining) recombination process. Mutations in RAG1 have been reported to be associated with several types of immune disorders. Typical clinical features driven by RAG1 variants include persistent infections, severe lymphopenia, and decreased immunoglobulin levels .

CASE PRESENTATION

In this study, a 2-month-24-days-old infant with recurrent fever was admitted to our hospital with multiple infections and absence of T and B lymphocytes. The infant was diagnosed with severe combined immunodeficiency (SCID). A homozygous variation c.2147G>A (NM_000448.2: exonme2: c.2147G>A (p.Arg716Gln)) was identified in the RAG1 gene using whole-exome sequencing and Sanger sequencing. The predicted 3D structure of variant RAG1 indicated altered protein stability. Additionally, decreased expression of variant RAG1 gene was detected at both the mRNA and protein levels.

CONCLUSIONS

Our study identified a novel homozygous variant in RAG1 gene that causes SCID. This finding expands the variant spectrum of RAG1 in SCID and provides further evidence for the clinical diagnosis of SCID.

Multiplex HDR for disease and correction modeling of SCID by CRISPR genome editing in human HSPCs

Severe combined immunodeficiency (SCID) is a group of disorders caused by mutations in genes involved in the process of lymphocyte maturation and function. CRISPR-Cas9 gene editing of the patient's own hematopoietic stem and progenitor cells (HSPCs) ex vivo could provide a therapeutic alternative to allogeneic hematopoietic stem cell transplantation, the current gold standard for treatment of SCID. To eliminate the need for scarce patient samples, we engineered genotypes in healthy donor (HD)-derived CD34⁺ HSPCs using CRISPR-Cas9/rAAV6 gene-editing, to model both SCID and the therapeutic outcomes of gene-editing therapies for SCID via multiplexed homology-directed repair (HDR). First, we developed a SCID disease model via biallelic knockout of genes critical to the development of lymphocytes; and second, we established a knockin/knockout strategy to develop a proof-of-concept single-allelic gene correction. Based on these results, we performed gene correction of RAG2-SCID patient-derived CD34⁺ HSPCs that successfully developed into CD3⁺ T cells with diverse TCR repertoires in an in vitro T cell differentiation platform. In summary, we present a strategy to determine the optimal configuration for CRISPR-Cas9 gene correction of SCID using HD-derived CD34⁺ HSPCs, and the feasibility of translating this gene correction approach in patient-derived CD34⁺ HSPCs.

Newborn screening for severe combined immunodeficiency: The results of the first pilot TREC and KREC study in Ukraine with involving of 10,350 neonates

Severe combined immunodeficiency (SCID) is a group of inborn errors of immunity (IEI) characterized by severe T- and/or B-lymphopenia. At birth, there are usually no clinical signs of the disease, but in the first year of life, often in the first months the disease manifests with severe infections. Timely diagnosis and treatment play a crucial role in patient survival. In Ukraine, the expansion of hemostatic stem cell transplantation and the development of a registry of bone marrow donors in the last few years have created opportunities for early correction of IEI and improving the quality and life expectancy of children with SCID. For the first time in Ukraine, we initiated a pilot study on newborn screening for severe combined immunodeficiency and T-cell lymphopenia by determining T cell receptor excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs). The analysis of TREC and KREC was performed by real-time polymerase chain reaction (RT-PCR) followed by analysis of melting curves in neonatal dry blood spots (DBS). The DBS samples were collected between May 2020 and January 2022. In total, 10,350 newborns were screened. Sixty-five blood DNA samples were used for control: 25 from patients with ataxia-telangiectasia, 37 - from patients with Nijmegen breakage syndrome, 1 – with X-linked agammaglobulinemia, 2 – with SCID (JAK3 deficiency and DCLRE1C deficiency). Retest from the first DBS was provided in 5.8% of patients. New sample test was needed in 73 (0.7%) of newborns. Referral to confirm or rule out the diagnosis was used in 3 cases, including one urgent abnormal value. CID (T^lowB+NK+) was confirmed in a patient with the urgent abnormal value. The results of a pilot study in Ukraine are compared to other studies (the referral rate 1: 3,450). Approbation of the method on DNA samples of children with ataxia-telangiectasia and Nijmegen syndrome showed a high sensitivity of TRECs (a total of 95.2% with cut-off 2000 copies per 10⁶ cells) for the detection of these diseases. Thus, the tested method has shown its effectiveness for the detection of T- and B-lymphopenia and can be used for implementation of newborn screening for SCID in Ukraine.

Diagnosis and Treatment of a Patient With Severe Combined Immunodeficiency Due to a Novel Homozygous Mutation in the IL-7Rα Chain

The interleukin-7 receptor (IL-7R) is expressed on lymphoid cells and plays an important role in the development, homeostasis, survival, and proliferation of T cells. Bi-allelic mutations in the IL-7Rα chain abolish T cell development and function resulting in severe combined immunodeficiency disease. In this manuscript, we investigate a 1 year-old patient born to consanguineous parents, who suffered from autoimmune hemolytic anemia since birth associated with recurrent severe infections. Flow cytometric analysis of the patient’s peripheral blood demonstrated elevated numbers of B and NK cells, decreased numbers of T cells, defective thymic output, a predominance of memory T cells, and absent T cell proliferation. Next Generation Sequencing identified a novel homozygous pathogenic mutation in IL7RA (c.379G>A) that resulted in aberrant IL7RA RNA splicing and absent IL-7Rα expression. The patient was successfully transplanted using her HLA-matched relative as donor. One year after transplant, the patient is clinically stable with normal reconstitution of donor T cells that express IL-7Rα, a significant increase in the percentages of recent thymic emigrant and peripheral T cells, normalization of naïve and memory T cells, and restoration of her T cell’s proliferative response. Therefore, using genetic and functional approaches, we identified a novel deleterious mutation in IL-7Rα that results in T^-B⁺NK⁺ phenotype, and report successful hematopoietic stem cell transplantation of the patient. This represents the first bedside-to-bench-and-back case entirely performed on a patient with severe combined immunodeficiency at the American University of Beirut Medical Center.

Case Report: Mutations in JAK3 causing severe combined immunodeficiency complicated by disseminated Bacille Calmette-Guérin disease and Pneumocystis pneumonia

BACKGROUND

As a form of severe combined immunodeficiency (SCID), Janus kinase 3 (JAK3) deficiency can be fatal during severe infections in children, especially after inoculation of live-attenuated vaccines. We report a unique case of JAK3 deficiency with two compound heterozygous JAK3 mutations complicated by disseminated Bacille Calmette-Guérin (BCG) disease and Pneumocystis pneumonia.

CASE DESCRIPTION

A 5-month-old Chinese girl presented with recurring fever and productive cough after BCG vaccination and ineffective antibiotic treatment. Chest CT demonstrated bilateral infiltrations, enlarged mediastinal and axillary lymph nodes, and hypoplasia of the thymus. Mycobacterium tuberculosis and Pneumocystis jirovecii were detected from blood samples by sequencing. Acid-fast bacilli were also found from the sputum aspirate and gastric aspirate. Lymphocyte subset analyses indicated T-B+NK- immunodeficiency, and gene sequencing identified two heterozygous missense mutations (one unreported globally) in the Janus homology 7 (JH7) domain of JAK3. The patient received rifampicin, isoniazid, ethambutol, and trimethoprim/sulfamethoxazole and was discharged after improvements but against advice.

OUTCOME

The patient died at 13 months of age due to severe infections and hepatic damage.

DISCUSSION

SCID should be recognized before inoculation of live-attenuated vaccines in children. Newborn screening for SCID is advocated. Further investigations are needed to better understand the pathogenicity of the variants and molecular mechanism of the JH7 domain of JAK3.

Reticular Dysgenesis: A Rare Immunodeficiency in a Neonate With Cytopenias and Bacterial Sepsis

Severe combined immunodeficiency (SCID) consists of a group of disorders defined by abnormal B and T cell development that typically results in death within the first year of life if undiagnosed or untreated. Reticular dysgenesis (RD) is a rare but especially severe form of SCID that is caused by adenylate kinase 2 deficiency and is characterized not only by lymphopenia but also by profound neutropenia. RD predisposes patients to viral and fungal infections typical of SCID as well as serious bacterial infections atypical in the neonatal period in other SCID types. RD is also associated with sensorineural hearing loss not typically seen in other forms of SCID. Without rapid diagnosis and curative hematopoietic stem cell transplantation, RD is fatal within days to months due to overwhelming bacterial infection. The inclusion of the T cell receptor excision circle assay nationally in 2017 on the newborn screen has facilitated diagnosis of SCID in the neonatal period. This case reports on a male infant with RD who presented after preterm birth with severe cytopenias and a gastrointestinal anomaly and ultimately developed severe bacterial sepsis. Postmortem bone marrow evaluation and panel-based gene sequencing identifying 2 novel variants in the adenylate kinase 2 gene provided confirmation for a diagnosis of RD. This case emphasizes the importance of thorough diagnostic evaluation, including the newborn screen, in neonates and infants with persistent and unexplained cytopenias. Prompt hematology and/or immunology referral is advised for disease management and to facilitate hematopoietic stem cell transplantation to optimize long-term survival.

Recent advances in lentiviral vectors for gene therapy

Lentiviral vectors (LVs), derived from human immunodeficiency virus, are powerful tools for modifying the genes of eukaryotic cells such as hematopoietic stem cells and neural cells. With the extensive and in-depth studies on this gene therapy vehicle over the past two decades, LVs have been widely used in both research and clinical trials. For instance, third-generation and self-inactive LVs have been used to introduce a gene with therapeutic potential into the host genome and achieve targeted delivery into specific tissue. When LVs are employed in leukemia, the transduced T cells recognize and kill the tumor B cells; in β-thalassemia, the transduced CD34⁺ cells express normal β-globin; in adenosine deaminase-deficient severe combined immunodeficiency, the autologous CD34⁺ cells express adenosine deaminase and realize immune reconstitution. Overall, LVs can perform significant roles in the treatment of primary immunodeficiency diseases, hemoglobinopathies, B cell leukemia, and neurodegenerative diseases. In this review, we discuss the recent developments and therapeutic applications of LVs. The safe and efficient LVs show great promise as a tool for human gene therapy.

Autoimmunity in Primary Immunodeficiency Disorders: An Updated Review on Pathogenic and Clinical Implications

During the last years, studies investigating the intriguing association between immunodeficiency and autoimmunity led to the discovery of new monogenic disorders, the improvement in the knowledge of the pathogenesis of autoimmunity, and the introduction of targeted treatments. Autoimmunity is observed with particular frequency in patients with primary antibody deficiencies, such as common variable immunodeficiency (CVID) and selective IgA deficiency, but combined immunodeficiency disorders (CIDs) and disorders of innate immunity have also been associated with autoimmunity. Among CIDs, the highest incidence of autoimmunity is described in patients with autoimmune polyendocrine syndrome 1, LRBA, and CTLA-4 deficiency, and in patients with STAT-related disorders. The pathogenesis of autoimmunity in patients with immunodeficiency is far to be fully elucidated. However, altered germ center reactions, impaired central and peripheral lymphocyte negative selection, uncontrolled lymphocyte proliferation, ineffective cytoskeletal function, innate immune defects, and defective clearance of the infectious agents play an important role. In this paper, we review the main immunodeficiencies associated with autoimmunity, focusing on the pathogenic mechanisms responsible for autoimmunity in each condition and on the therapeutic strategies. Moreover, we provide a diagnostic algorithm for the diagnosis of PIDs in patients with autoimmunity.

Normal IgH Repertoire Diversity in an Infant with ADA Deficiency After Gene Therapy

PURPOSE

Adenosine deaminase (ADA) deficiency causes severe combined immunodeficiency (SCID) through an accumulation of toxic metabolites within lymphocytes. Recently, ADA deficiency has been successfully treated using lentiviral-transduced autologous CD34+ cells carrying the ADA gene. T and B cell function appears to be fully restored, but in many patients' B cell numbers remain low, and assessments of the immunoglobulin heavy (IgHV) repertoire following gene therapy are lacking.

METHODS

We performed deep sequencing of IgHV repertoire in peripheral blood lymphocytes from a child following lentivirus-based gene therapy for ADA deficiency and compared to the IgHV repertoire in healthy infants and adults.

RESULTS

After gene therapy, Ig diversity increased over time as evidenced by V, D, and J gene usage, N-additions, CDR3 length, extent of somatic hypermutation, and Ig class switching. There was the emergence of predominant IgHM, IgHG, and IgHA CDR3 lengths after gene therapy indicating successful oligoclonal expansion in response to antigens. This provides proof of concept for the feasibility and utility of molecular monitoring in following B cell reconstitution following gene therapy for ADA deficiency.

CONCLUSION

Based on deep sequencing, gene therapy resulted in an IgHV repertoire with molecular diversity similar to healthy infants.

Immune Response in Pneumocystis Infections According to the Host Immune System Status

The host immune response is critical in Pneumocystis pneumonia (PCP). Immunocompetent hosts can eliminate the fungus without symptoms, while immunodeficient hosts develop PCP with an unsuitable excessive inflammatory response leading to lung damage. From studies based on rodent models or clinical studies, this review aimed to better understand the pathophysiology of Pneumocystis infection by analysing the role of immune cells, mostly lymphocytes, according to the immune status of the infected host. Hence, this review first describes the immune physiological response in infected immunocompetent hosts that are able to eliminate the fungus. The objective of the second part is to identify the immune elements required for the control of the fungus, focusing on specific immune deficiencies. Finally, the third part concentrates on the effect of the different immune elements in immunocompromised subjects during PCP, to better understand which cells are detrimental, and which, on the contrary, are beneficial once the disease has started. This work highlights that the immune response associated with a favourable outcome of the infection may differ according to the immune status of the host. In the case of immunocompetency, a close communication between B cells and TCD4 within tertiary lymphocyte structures appears critical to activate M2 macrophages without much inflammation. Conversely, in the case of immunodeficiency, a pro-inflammatory response including Th1 CD4, cytotoxic CD8, NK cells, and IFNγ release seems beneficial for M1 macrophage activation, despite the impact of inflammation on lung tissue.

Lymphadenopathy at the crossroad between immunodeficiency and autoinflammation: An intriguing challenge

Lymphadenopathies can be part of the clinical spectrum of several primary immunodeficiencies, including diseases with immune dysregulation and autoinflammatory disorders, as the clinical expression of benign polyclonal lymphoproliferation, granulomatous disease or lymphoid malignancy. Lymphadenopathy poses a significant diagnostic dilemma when it represents the first sign of a disorder of the immune system, leading to a consequently delayed diagnosis. Additionally, the finding of lymphadenopathy in a patient with diagnosed immunodeficiency raises the question of the differential diagnosis between benign lymphoproliferation and malignancies. Lymphadenopathies are evidenced in 15–20% of the patients with common variable immunodeficiency, while in other antibody deficiencies the prevalence is lower. They are also evidenced in different combined immunodeficiency disorders, including Omenn syndrome, which presents in the first months of life. Interestingly, in the activated phosphoinositide 3‐kinase delta syndrome, autoimmune lymphoproliferative syndrome, Epstein–Barr virus (EBV)‐related lymphoproliferative disorders and regulatory T cell disorders, lymphadenopathy is one of the leading signs of the entire clinical picture. Among autoinflammatory diseases, the highest prevalence of lymphadenopathies is observed in patients with periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) and hyper‐immunoglobulin (Ig)D syndrome. The mechanisms underlying lymphoproliferation in the different disorders of the immune system are multiple and not completely elucidated. The advances in genetic techniques provide the opportunity of identifying new monogenic disorders, allowing genotype–phenotype correlations to be made and to provide adequate follow‐up and treatment in the single diseases. In this work, we provide an overview of the most relevant immune disorders associated with lymphadenopathy, focusing on their diagnostic and prognostic implications.

Omenn syndrome caused by a novel homozygous mutation in recombination activating gene 1

Omenn syndrome (OS) is a type of severe combined immunodeficiency (SCID) that is distinguished by, lymphadenopathy, hepatosplenomegaly, erythroderma, alopecia with normal to elevated T-cell counts, eosinophilia, and elevated serum IgE levels. Recombination activation gene (RAG) 1 or RAG2 mutations that result in partial V(D)J recombination activity are known to be the main cause of OS. Other genes (DCLRE1C, LIG4, IL7RA, common gamma chain, ADA, RMRP, and CHD7) have also been linked to OS, although with low frequency. Here, we report a two-month-old Moroccan girl from consanguineous marriage with chronic diarrhea, recurrent and opportunistic infections, failure to thrive, desquamative erythroderma, hepatosplenomegaly, and axillary lymphadenitis. The immunological assessment showed normal lymphocyte and NK cell counts but an absence of B cells, agammaglobulinemia contrasting with a high level of IgE. On the other hand, Sanger sequencing of RAG1 and RAG2 exon 2 regions revealed a new homozygous deleterious mutation in the RAG1 gene. This c.1184C > T mutation caused a change from Proline to Leucine at position 395 of the protein, leading to a partial loss of function. Early and rapid diagnosis of the disease may facilitate urgent life-saving treatment.

Combined immunodeficiencies

OBJECTIVES

Inborn Errors of Immunity (IEI), also known as primary immunodeficiencies, correspond to a heterogeneous group of congenital diseases that primarily affect immune response components. The main clinical manifestations comprise increased susceptibility to infections, autoimmunity, inflammation, allergies and malignancies. The aim of this article is to review the literature on combined immunodeficiencies (CIDs) focusing on the diagnosis and treatment and the particularities of the clinical management of these patients.

SOURCE OF DATA

Critical integrative review, aimed to present articles related to primary immunodeficiencies combined with a searchin the PubMed and SciELO databases, with evaluation of publications from the last twenty years that were essential for the construction of knowledge on this group of diseases.

SUMMARY OF DATA

We highlight the main characteristics of CIDs, dividing them according to their pathophysiological mechanisms, such as defects in the development of T cells, TCR signaling, co-stimulatory pathways, cytokine signaling, adhesion, migration and organization of the cytoskeleton, apoptosis pathways, DNA replication and repair and metabolic pathways. In CIDs, clinical manifestations vary widely, from sinopulmonary bacterial infections and diarrhea to opportunistic infections, caused by mycobacteria and fungi. Neonatal screening makes it possible to suspect these diseases before clinical manifestations appear.

CONCLUSIONS

The CIDs or IEI constitute a complex group of genetic diseases with T-cell involvement. Neonatal screening for these diseases has improved the prognosis of these patients, especially in severe ones, known as SCIDs.

Severe Combined Immunodeficiency Disorder due to a Novel Mutation in Recombination Activation Gene 2: About 2 Cases

Severe combined immunodeficiency (SCID) comprises a heterogeneous group of inherited immunologic disorders with profound defects in cellular and humoral immunity. SCID is the most severe PID and constitutes a pediatric emergency. Affected children are highly susceptible to bacterial, viral, fungal, and opportunistic infections with life-threatening in the absence of hematopoietic stem cell transplantation. We report here two cases of SCID. The first case is a girl diagnosed with SCID at birth based on her family history and lymphocyte subpopulation typing. The second case is a 4-month-old boy with a history of recurrent opportunistic infections, BCGitis, and failure to thrive, and the immunology workup confirms a SCID phenotype. The genetic study in the two cases revealed a novel mutation in the RAG2 gene, c.826G > A (p.Gly276Ser), in a homozygous state. The novel mutation in the RAG2 gene identified in our study may help the early diagnosis of SCID.

Clinical and Immunological Features of 96 Moroccan Children with SCID Phenotype: Two Decades' Experience

Severe combined immunodeficiency (SCID) is a heterogeneous group of primary immunodeficiency diseases (PIDs) characterized by a lack of autologous T lymphocytes. This severe PID is rare, but has a higher prevalence in populations with high rates of consanguinity. The epidemiological, clinical, and immunological features of SCIDs in Moroccan patients have never been reported. The aim of this study was to provide a clinical and immunological description of SCID in Morocco and to assess changes in the care of SCID patients over time. This cross-sectional retrospective study included 96 Moroccan patients referred to the national PID reference center at Casablanca Children's Hospital for SCID over two decades, from 1998 to 2019. The case definition for this study was age < 2 years, with a clinical phenotype suggestive of SCID, and lymphopenia, with very low numbers of autologous T cells, according to the IUIS Inborn Errors of Immunity classification. Our sample included 50 male patients, and 66% of the patients were born to consanguineous parents. The median age at onset and diagnosis were 3.3 and 6.5 months, respectively. The clinical manifestations commonly observed in these patients were recurrent respiratory tract infection (82%), chronic diarrhea (69%), oral candidiasis (61%), and failure to thrive (65%). The distribution of SCID phenotypes was as follows: T-B-NK+ in 44.5%, T-B-NK- in 32%, T-B+NK- in 18.5%, and T-B+NK+ in 5%. An Omenn syndrome phenotype was observed in 15 patients. SCID was fatal in 84% in the patients in our cohort, due to the difficulties involved in obtaining urgent access to hematopoietic stem cell transplantation, which, nevertheless, saved 16% of the patients. The autosomal recessive forms of the clinical and immunological phenotypes of SCID, including the T-B-NK+ phenotype in particular, were more frequent than those in Western countries. A marked improvement in the early detection of SCID cases over the last decade was noted. Despite recent progress in SCID diagnosis, additional efforts are required, for genetic confirmation and particularly for HSCT.

Inherited SLP76 deficiency in humans causes severe combined immunodeficiency, neutrophil and platelet defects

The T cell receptor (TCR) signaling pathway is an ensemble of numerous proteins that are crucial for an adequate immune response. Disruption of any protein involved in this pathway leads to severe immunodeficiency and unfavorable clinical outcomes. Here, we describe an infant with severe immunodeficiency who was found to have novel biallelic mutations in SLP76. SLP76 is a key protein involved in TCR signaling and in other hematopoietic pathways. Previous studies of this protein were performed using Jurkat-derived human leukemic T cell lines and SLP76-deficient mice. Our current study links this gene, for the first time, to a human immunodeficiency characterized by early-onset life-threatening infections, combined T and B cell immunodeficiency, severe neutrophil defects, and impaired platelet aggregation. Hereby, we characterized aspects of the patient's immune phenotype, modeled them with an SLP76-deficient Jurkat-derived T cell line, and rescued some consequences using ectopic expression of wild-type SLP76. Understanding human diseases due to SLP76 deficiency is helpful in explaining the mixed T cell and neutrophil defects, providing a guide for exploring human SLP76 biology.

Consensus of the Italian Primary Immunodeficiency Network on transition management from pediatric to adult care in patients affected with childhood-onset inborn errors of immunity

Medical advances have dramatically improved the long-term prognosis of children and adolescents with inborn errors of immunity (IEIs). Transfer of the medical care of individuals with pediatric IEIs to adult facilities is also a complex task because of the large number of distinct disorders, which requires involvement of patients and both pediatric and adult care providers. To date, there is no consensus on the optimal pathway of the transitional care process and no specific data are available in the literature regarding patients with IEIs. We aimed to develop a consensus statement on the transition process to adult health care services for patients with IEIs. Physicians from major Italian Primary Immunodeficiency Network centers formulated and answered questions after examining the currently published literature on the transition from childhood to adulthood. The authors voted on each recommendation. The most frequent IEIs sharing common main clinical problems requiring full attention during the transitional phase were categorized into different groups of clinically related disorders. For each group of clinically related disorders, physicians from major Italian Primary Immunodeficiency Network institutions focused on selected clinical issues representing the clinical hallmark during early adulthood.

Diagnosis of radiosensitive severe combined immunodeficiency disease (RS-SCID) by Comet Assay, management of bone marrow transplantation

BACKGROUND AND OBJECTIVE

Severe combined immunodeficiency disease (SCID) is a rare inherited severe immunodeficiency, in which functions of T cells and B cells are impaired. SCID is inherited either in X-linked recessive, or autosomal recessive forms, and is either radiosensitive or radioresistant. Artemis (DCLRE1C gene), DNA ligase IV, DNA-PKC, and Cernunnos/XLF proteins are regarded as NHEJ (Non-Homologous End-Joining) proteins that are involved in the repair process of double-strand DNA breaks and their mutations would lead to cellular radiosensitivity. Diagnostic radiosensitivity assays are important for the management of clinical BMT (Bone Marrow Transplantation) conditions, such as what conditioning agents and doses should be used.

MATERIALS AND METHODS

In this study, five SCID patients and healthy controls were examined. Skin fibroblasts were cultured. After X-irradiation, cells either underwent clonogenic assay or incubated to allow DNA repair and examined by the alkaline comet assay. Finally, DCLRE1C, RAG-1, and RAG-2 genes sequenced.

RESULTS

By clonogenic assay, three patients were detected as radiosensitive with possible mutations in NHEJ genes such as DCLRE1C gene. The percentage of DNA in the tail measured by comet assay, in all three patients, was significantly different from the two other patients and the control group (p-value < 0.05). By using Sanger sequencing, a mutation in DCLRE1C gene was detected in one of the radiosensitive patients and two mutations in RAG-1, and RAG-2 genes were detected in the two radioresistant patients.

CONCLUSION

Our findings suggest that comet assay is a fast technique for the diagnosis of the radiosensitive form of SCID and is very suitable for the timely diagnosis of RS-SCID before BMT.

Increasing CRISPR Efficiency and Measuring Its Specificity in HSPCs Using a Clinically Relevant System

Genome editing of human cluster of differentiation 34⁺ (CD34⁺) hematopoietic stem and progenitor cells (HSPCs) holds great therapeutic potential. This study aimed to optimize on-target, ex vivo genome editing using the CRISPR-Cas9 system in CD34⁺ HSPCs and to create a clear workflow for precise identification of off-target effects. Modified synthetic guide RNAs (gRNAs), either 2-part gRNA or single-guide RNA (sgRNA), were delivered to CD34⁺ HSPCs as part of ribonucleoprotein (RNP) complexes, targeting therapeutically relevant genes. The addition of an Alt-R electroporation enhancer (EE), a short, single-stranded oligodeoxynucleotide (ssODN), significantly increased editing efficiency in CD34⁺ HSPCs. Notably, similar editing improvement was observed when excess gRNA over Cas9 protein was used, providing a DNA-free alternative suitable for therapeutic applications. Furthermore, we demonstrated that sgRNA may be preferable over 2-part gRNA in a locus-specific manner. Finally, we present a clear experimental framework suitable for the unbiased identification of bona fide off-target sites by Genome-Wide, Unbiased Identification of Double-Strand Breaks (DSBs) Enabled by Sequencing (GUIDE-seq), as well as subsequent editing quantification in CD34⁺ HSPCs using rhAmpSeq. These findings may facilitate the implementation of genome editing in CD34⁺ HSPCs for research and therapy and can be adapted for other hematopoietic cells.

Primary Immunodeficiency Diseases and Bacillus Calmette-Guérin (BCG)-Vaccine-Derived Complications: A Systematic Review

BACKGROUND

Bacillus Calmette-Guérin (BCG) vaccine is a live attenuated bacterial vaccine derived from Mycobacterium bovis, which is mostly administered to neonates in regions where tuberculosis is endemic. Adverse reactions after BCG vaccination are rare; however, immunocompromised individuals and in particular patients with primary immunodeficiencies (PIDs) are prone to develop vaccine-derived complications.

OBJECTIVE

To systematically review demographic, clinical, immunologic, and genetic data of PIDs that present with BCG vaccine complications. Moreover, we performed a meta-analysis aiming to determine the BCG-vaccine complications rate for patients with PID.

METHODS

We conducted electronic searches on Embase, Web of Science, PubMed, and Scopus (1966 to September 2018) introducing terms related to PIDs, BCG vaccination, and BCG vaccine complications. Studies with human subjects with confirmed PID, BCG vaccination history, and vaccine-associated complications (VACs) were included.

RESULTS

A total of 46 PIDs associated with BCG-VAC were identified. Severe combined immunodeficiency was the most common (466 cases) and also showed the highest BCG-related mortality. Most BCG infection cases in patients with PID were reported from Iran (n = 219 [18.8%]). The overall frequency of BCG-VAC in the included 1691 PID cases was 41.5% (95% CI, 29.9-53.2; I² = 98.3%), based on the results of the random-effect method used in this meta-analysis. Patients with Mendelian susceptibility to mycobacterial diseases had the highest frequency of BCG-VACs with a pooled frequency of 90.6% (95% CI, 79.7-1.0; I² = 81.1%).

CONCLUSIONS

Several PID entities are susceptible to BCG-VACs. Systemic neonatal PID screening programs may help to prevent a substantial amount of BCG vaccination complications.

[Ichtyosiform erythroderma revealing a severe combined immunodeficiency]

BACKGROUND

Severe combined immunodeficiency (SCID) is a the most severe form of primary immunodeficiency and is highly heterogeneous. We report an atypical form of SCID revealed by exfoliative erythroderma.

PATIENTS AND METHODS

A 3-month-old boy, born to consanguineous parents, was admitted to the dermatology department with exfoliative erythroderma associated with eczematous patches and alopecia of the scalp, eyelashes, and eyebrows, but with no lymphadenopathy or hepatosplenomegaly. He displayed chronic diarrhea and recurrent infection since birth. A complete blood count showed marked leukocytosis with eosinophilia and lymphocytosis. These clinical and biological findings improved partly with topical steroids. The patient no longer had erythroderma and showed regrowth of hair, eyelashes and eyebrows. The subsequent CBC showed less marked eosinophilia with mild lymphopenia and no leukocytosis. Immunoglobulin levels were undetectable. Primary immunodeficiency was discussed. Immunological investigations concluded on a diagnosis of T-B-NK+ SCID. Mutation analysis revealed a homozygous c.1338C>G (pCys446Trp) mutation in the RAG2 gene. Hematopoietic stem cell transplantation is planned in the near future.

CONCLUSION

This case illustrates atypical T-B-NK+ SCID revealed by severe exfoliative erythroderma in a 3-month-old boy with RAG2 gene mutation. Neonatal erythroderma must be considered a warning sign of primary immunodeficiency requiring immediate immunological phenotyping as well as genetic testing for a definitive diagnosis.

Approaches to patients with variants in RAG genes: from diagnosis to timely treatment

Introduction: Patients with primary immunodeficiency secondary to abnormal recombinase activating genes (RAG) can present with broad clinical phenotypes ranging from early severe infections to autoimmune complications and inflammation. Immunological phenotype may also vary from T^-B^- severe combined immunodeficiency to combined immunodeficiency or antibody deficiencies with near-normal T and B cell counts and even preserved specific antibody response to pathogens. It is not uncommon that RAG variants of uncertain significance are identified by serendipity during a broad genetic screening process and pathogenic RAG variants are increasingly recognized among all age groups, including adults. Establishing the pathogenicity and clinical relevance of novel RAG variants can be challenging since RAG genes are highly polymorphic. This review paper aims to summarize clinical phenotypes of RAG deficiencies and provide practical guidance for confirming the direct link between specific RAG variants and clinical disease. Lastly, we will review the current understanding of treatment option for patients with varying severity of RAG deficiencies. Area covered: This review discusses the different phenotypes and immunological aspects of RAG deficiencies, the diagnosis dilemma facing clinicians, and an overview of current and advancement in treatments. Expert opinion: A careful analysis of immunological and clinical data and their correlation with genetic findings helps to determine the significance of the genetic polymorphism. Advances in functional assays, as well as anti-cytokine antibodies, make it easier to resolve the diagnostic dilemma.

Immunological features in pediatric patients with recurrent and severe infection: Identification of Primary Immunodeficiency Diseases in Merida, Venezuela

INTRODUCTION AND OBJECTIVES

Primary immunodeficiency diseases (PIDs) are disorders associated mainly with recurrent and severe infection and an increase in susceptibility to autoimmune conditions and cancer. In Venezuela, PIDs are underdiagnosed and there is usually a delay in their diagnosis. Hence there are no data concerning the frequency and type of PIDs that occur. The aim of this study was to identify and quantify the types of PIDs that occur in Merida, a population within Venezuela.

PATIENTS OR MATERIALS AND METHODS

Following an informative program designed to alert local health professionals to the warning signs for PIDs, patients with a history of recurrent infections were referred to the Instituto de Inmunologia Clinica, Universidad de Los Andes.

RESULTS AND CONCLUSIONS

During the three-year period January 2014 to January 2017, thirty-two cases of PIDs were identified in pediatric patients, and 17 different types of PIDs, were identified. Predominantly antibody deficiencies were most frequent (40.6%), followed by immunodeficiencies affecting cellular and humoral immunity (21.8%), congenital defects of phagocyte (18.7%), CID with associated or syndromic features (9.3%), defects in intrinsic and innate immunity (6.4%) and diseases of immune dysregulation (3.2%). These results have important implications not only to the future approach for management of patients in our regions, but add important knowledge concerning PIDs in Latin America and worldwide.

Quantification of T-Cell and B-Cell Replication History in Aging, Immunodeficiency, and Newborn Screening

Quantification of T-cell receptor excision circles (TRECs) has impacted on human T-cell research, but interpretations on T-cell replication have been limited due to the lack of a genomic coding joint. We here overcome this limitation with multiplex TRG rearrangement quantification (detecting ~0.98 alleles per TCRαβ+ T cell) and the HSB-2 cell line with a retrovirally introduced TREC construct. We uncovered <5 cell divisions in naive and >10 cell divisions in effector memory T-cell subsets. Furthermore, we show that TREC dilution with age in healthy adults results mainly from increased T cell replication history. This proliferation was significantly increased in patients with predominantly antibody deficiency. Finally, Guthrie cards of neonates with Down syndrome have fewer T and B cells than controls, with similar T-cell and slightly higher B-cell replication. Thus, combined analysis of TRG coding joints and TREC signal joints can be utilized to quantify in vivo T-cell replication, and has direct applications for research into aging, immunodeficiency, and newborn screening.

[Ectopic thymic tissue and ectopic thymic tumors]

Ectopic thymic tissue outside its core position in the antero-superior mediastinum is quite common owing to the complexity of embryonal thymus development, whereby reported prevalence values (1 to 90%) are heavily dependent on the method of investigation and the intensity of the workup. The debated prevalence and relevance of ectopic thymic tissue and its accessibility underlie the ongoing discussion whether modern, minimally invasive thymectomy strategies can match the proven benefit of the radical transsternal thymectomy procedure for the treatment of Myasthenia gravis. In this context, the following article covers the etiology, prevalence, and location of normal-looking, reactive, and neoplastic ectopic thymic tissue. Furthermore, ectopic tissues and tumors inside or adjacent to the thymus are mentioned.

Clinical, Immunological, and Molecular Features of Typical and Atypical Severe Combined Immunodeficiency: Report of the Italian Primary Immunodeficiency Network

Severe combined immunodeficiencies (SCIDs) are a group of inborn errors of the immune system, usually associated with severe or life-threatening infections. Due to the variability of clinical phenotypes, the diagnostic complexity and the heterogeneity of the genetic basis, they are often difficult to recognize, leading to a significant diagnostic delay (DD). Aim of this study is to define presenting signs and natural history of SCID in a large cohort of patients, prior to hematopoietic stem cell or gene therapies. To this purpose, we conducted a 30-year retro-prospective multicenter study within the Italian Primary Immunodeficiency Network. One hundred eleven patients, diagnosed as typical or atypical SCID according to the European Society for Immune Deficiencies criteria, were included. Patients were subsequently classified based on the genetic alteration, pathogenic mechanism and immunological classification. A positive relationship between the age at onset and the DD was found. SCID patients with later onset were identified only in the last decade of observation. Syndromic SCIDs represented 28% of the cohort. Eight percent of the subjects were diagnosed in Intensive Care Units. Fifty-three percent had an atypical phenotype and most of them exhibited a discordant genotype-immunophenotype. Pre-treatment mortality was higher in atypical and syndromic patients. Our study broadens the knowledge of clinical and laboratory manifestations and genotype/phenotype correlation in patients with SCID and may facilitate the diagnosis of both typical and atypical forms of the disease in countries where newborn screening programs have not yet been implemented.

Considerations for hematopoietic stem cell transplantation in primary immunodeficiency disorders

Primary immunodeficiency disorders (PIDs) result from inborn errors in immunity. Susceptibility to infections and oftentimes severe autoimmunity pose life-threatening risks to patients with these disorders. Hematopoietic cell transplant (HCT) remains the only curative option for many. Severe combined immunodeficiency disorders (SCID) most commonly present at the time of birth and typically require emergent HCT in the first few weeks of life. HCT poses an unusual challenge for PIDs. Donor source and conditioning regimen often impact the outcome of immune reconstitution after HCT in PIDs. The use of matched or unmatched, as well as related versus unrelated donor has resulted in variable outcomes for different subsets of PIDs. Additionally, there is significant variability in the success of engraftment even for a single patient’s lymphocyte subpopulations. While certain cell lines do well without a conditioning regimen, others will not reconstitute unless conditioning is used. The decision to proceed with a conditioning regimen in an already immunocompromised host is further complicated by the fact that alkylating agents should be avoided in radiosensitive PIDs. This manuscript reviews some of the unique elements of HCT in PIDs and evidence-based approaches to transplant in patients with these rare and challenging disorders.

[Advances in newborn screening and immune system reconstitution of severe combined immunodeficiency]

Severe combined immunodeficiency disease (SCID) is a group of rare congenital diseases characterized by severe deficiencies in T lymphocyte counts and/or function. The recurrent, persistent and severe infections are its clinical manifestations. Neonatal screening and immune system reconstruction would improve the prognosis of SCID children. Newborn screening programs based on T-cell receptor excision circles (TRECs) quantitative detection have been carried out in clinical practice, however, the methods still have some limitations. Other new methods such as mass spectrometry and T lymphocyte-specific biomarker assays are still under investigation. Hematopoietic stem cell transplantation and gene therapy are the two main methods for reconstructing immune function in SCID children. Through improving the success rate of transplantation and the long-term safety and stability of viral vectors, some achievements have been made by many centers already. However, large-scale prospective studies are needed for evaluation of the long-term efficacy. In this article, the recent progress in newborn screening and immune reconstitution of SCID is reviewed.

Follow-up Study of a Child with Severe Combined Immune Deficiency

We present the results of 7-year follow-up of a patient with primary immunodeficiency, such as severe combined immune deficiency, X-linked variant. The child has been ill from 11 month of age. He was taken to the Regional Infectious Disease Hospital in Irkutsk by sanitary aviation in extremely serious condition, which threatened his life. At 1 year 2 months he was transferred to Irkutsk State Regional Children’s Clinical Hospital due to deterioration of the general condition, prolonged fever, expressed by hypoxemia. At 1 year 3 months he was diagnosed with primary immunodeficiency, X-linked severe combined immune deficiency, persistent CMV infection in the department of clinical immunology of the Republican Children’s Clinical Hospital in Moscow. The diagnosis was confirmed by molecular genetic method (mutation с.664С˃Т was detected in exon 5 of the IL2RG gene in the hemizygotic state). At 1 year 9 months, haploidentical transplantation of hematopoietic stem cells from the father was performed. According to the chimerism, immune transplant rejection was observed after 1.5 months. At 2 years 11 months, the boy successfully underwent allogeneic bone marrow transplantation from an unrelated donor in the Children’s Oncology and Hematology Hospital of the University Hospital Freiburg (Germany). The child is being regularly observed in Irkutsk State Regional Children’s Clinical Hospital. He suffers from respiratory infections 4–5 times a year in a mild form. He corresponds to peers in physical and psychomotor development.

Family-Based Next-Generation Sequencing Study Identifies an IL2RG Variant in an Infant with Primary Immunodeficiency

Primary immunodeficiencies (PIDs) are a rare and heterogeneous group of inherited genetic disorders that are characterized by an absent or impaired immune system. In this report, we describe the use of next-generation sequencing to investigate a male infant with clinical and immunological manifestations suggestive of a PID. Whole-exome sequencing of the infant along with his parents revealed a novel nucleotide variant (cytosine to adenine substitution at nucleotide position 252) in the coding region of the interleukin 2 receptor subunit gamma (IL2RG) gene. The mother was found to be a carrier. These findings are consistent with a diagnosis of X-linked severe combined immunodeficiency and represent the first such reported mutation in an Indian family. This mutation leads to an asparagine to lysine substitution (p.Asn84Lys) located in the extracellular domain of IL2RG, which is predicted to be pathogenic. Our study demonstrates the power of next-generation sequencing in identifying potential causative mutations to enable accurate clinical diagnosis, prenatal screening, and carrier female detection in PID patients. We believe that this approach, which is not a current routine in clinical practice, will become a mainstream component of individualized medicine in the near future.

Inmunodeficiencia combinada severa (SCID) en Neiva, Colombia. Reporte de caso

Introducción. Las inmunodeficiencias primarias son enfermedades genéticas del sistema inmune que incrementan la susceptibilidad a infecciones. Una de las formas más graves en niños es la inmunodeficiencia combinada severa.Presentación del caso. Se presenta el caso de un niño que fue diagnosticado con inmunodeficiencia combinada severa; este era un paciente masculino de ocho meses que presentó cuadro clínico consistente en múltiples hospitalizaciones debido a infección por citomegalovirus, endocarditis por Candida albicans e infección recurrente de las vías urinarias por Pseudomonas aeruginosa.El perfil inmunológico mostró disminución del número absoluto de células CD3+ y CD19+, lo que permitió realizar el diagnóstico de inmunodeficiencia combinada severa instaurándose manejo; sin embargo, el niño no se recuperó y falleció.Conclusiones. Las inmunodeficiencias primarias son patologías que requieren una intervención oportuna que permita brindar un mejor pronóstico a los pacientes.

Exploration of the therapeutic aspects of Lck: A kinase target in inflammatory mediated pathological conditions

Lck, a non-receptor src family kinase, plays a vital role in various cellular processes such as cell cycle control, cell adhesion, motility, proliferation and differentiation. As a 56 KDa protein, Lck phosphorylates tyrosine residues of various proteins such as ZAP-70, ITK and protein kinase C. The structure of Lck is comprised of three domains, one SH3 in tandem with a SH2 domain at the amino terminal and the kinase domain at the carboxy terminal. Physiologically, Lck is involved in the development, function and differentiation of T-cells. Additionally, Lck regulates neurite outgrowth and maintains long-term synaptic plasticity in neurons. Given a major role of Lck in cytokine production and T cell signaling, alteration in expression and activity of Lck may result in various diseased conditions like cancer, asthma, diabetes, rheumatoid arthritis, psoriasis, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, atherosclerosis etc. This article provides evidence and information establishing Lck as one of the therapeutic targets in various inflammation mediated pathophysiological conditions.

Otolaryngological features in a cohort of patients affected with 22q11.2 deletion syndrome: A monocentric survey

Otorhinolaryngologic manifestations are common in 22q11.2 deletion syndrome (22q11.2DS), but poorly described. This study aimed to better define the ear-nose-throat (ENT) phenotype of 22q11.2DS patients, in the attempt to best detect subjects requiring subspecialist intervention. We enrolled 25 patients affected with 22q11.2DS. Anatomic and functional ENT findings were investigated using clinical, laboratory, and instrumental data. Immunophenotype and frequency of infections were evaluated. Univariate and multivariate analyses were performed. ENT anomalies were found in 88% of patients, and in 20% congenital palate defects required surgery. Adenoid or palatine tonsil hypertrophy was noted in 80% and 48%. Forty-eight percent of subjects had rhinolalia/phonia, severe in half of these. We also found nasal regurgitation or laryngeal penetration/aspiration in 20% and 16%, respectively. Instrumental exams revealed a mild conductive hearing loss in 32% (bilateral in most cases), tympanometric anomalies in 28%, and swallowing abnormalities in 16%. Statistical univariate analysis showed a direct association between rhinolalia/phonia and episodes of laryngeal aspiration (p = .016) and between tympanometric anomalies and increased adenoid volume (p = .044). No association between episodes of food aspiration and palatal anomalies was found. Moreover, no statistically significant association was observed between the number of airway infections and the ENT findings. This study contributes to better define the ENT phenotype in patients with 22q11.2DS, helpful to prevent potential complications. Furthermore, the identification of a subcategory of patients may allow the early adoption of specific speech therapy programs to improve the clinical outcome of 22q11.2DS patients.

Newborn screening using TREC/KREC assay for severe T and B cell lymphopenia in Iran

T-cell receptor excision circles (TRECs) and κ-deleting recombination excision circles (KRECs) are recently used for detection of T or B cell lymphopenia in neonates based on region-specific cutoff levels. Here, we report cutoffs for TREC and KREC copies useful for newborn screening and/or diagnosis of primary immunodeficiency diseases (PID) in Iran. DNA was extracted from a single 3.2 mm punch of dried blood spots collected from 2160 anonymized newborns referred to two major referral health centres between 2014 and 2016. For refinement of the cutoffs, 51 patients with a definite diagnosis of severe combined immunodeficiency, X-linked agammaglobulinaemia and combined immunodeficiency, including ataxia telangiectasia, human phosphoglucomutase 3 and Janus kinase-3 deficiency, as well as 47 healthy controls were included. Samples from patients with an X-linked hyper-IgM-syndrome, Wiskott-Aldrich syndrome and DNA ligase 4 deficiency were considered as disease controls. Triplex-quantitative real-time PCR was used. Cutoffs were calculated as TRECs < 11 and KRECs < 6 copies with an ACTB > 700 copies with sensitivity of 100% for TREC and 97% for KREC. Among thirty anonymized newborn samples (1.5%) with abnormal results for TREC and/or KREC, only twenty-one available cases were retested and shown to be in the normal range except for three samples (0.15%). All of the patients with a definitive diagnosis were correctly identified based on our established TREC/KREC copy numbers. Determining cutoffs for TREC/KREC is essential for correctly identifying children with PID in newborn screening. Early diagnosis of PID patients enables appropriate measures and therapies like stem cell transplantation.