Newborn Screening for Primary Immunodeficiency Diseases: History, Current and Future Practice

Consensus of the Italian Primary Immunodeficiency Network on the use and interpretation of genetic testing for diagnosing inborn errors of immunity

BACKGROUND

Inborn errors of immunity (IEIs) comprise more than 500 different rare congenital disorders of the immune system and are characterized by susceptibility to infection and immune dysregulation. The significant overlap of the clinical features among the different forms may lead to diagnostic delay. High-throughput sequencing techniques may allow a timely genetic definition. Guidelines for the use and the interpretation of genetic testing produced by the American College of Medical Genetics and Genomics (ACMG) and the European Society of Human Genetics (ESHG) do not cover specifics for their application to IEIs.

OBJECTIVE

The aim of this consensus study was to define the best approach to genetic testing for IEIs.

METHODS

A panel of experts in the context of the Italian Primary Immunodeficiency Network (IPINet) composed a list of statements that were evaluated by the Delphi method.

RESULTS

The experts recommend that genetic testing for IEIs should be offered to selected patients with warning signs for IEIs and highlight the crucial role of thorough phenotyping and functional tests for the conclusive diagnosis of IEI. Comprehensive educational programs targeted to health care professionals and the public should be developed to increase IEIs awareness and reduce diagnostic delay. Ethical issues should be pondered over the diagnostic advantages of genetic tests requested for diagnostic purposes.

CONCLUSION

Adherence to guidelines on the use and interpretation of genetic tests for diagnosing IEIs should help limit the inappropriate use of these techniques, thereby reducing the risk of misdiagnosis and patient apprehension regarding inconclusive genetic results.

Comprehensive newborn screening for severe combined immunodeficiency, X-linked agammaglobulinemia, and spinal muscular atrophy: the Chinese experience

BACKGROUND

Newborn screening (NBS) for severe combined immunodeficiency (SCID), X-linked agammaglobulinemia (XLA), and spinal muscular atrophy (SMA) enables early diagnosis and intervention, significantly improving patient outcomes. Advances in real-time polymerase chain reaction (PCR) technology have been instrumental in facilitating their inclusion in NBS programs.

METHODS

We employed multiplex real-time PCR to simultaneously detect T-cell receptor excision circles (TRECs), kappa-deleting recombination excision circles (KRECs), and the absence of the survival motor neuron (SMN) 1 gene in dried blood spots from 103,240 newborns in Zhejiang Province, China, between July 2021 and December 2022.

RESULTS

Of all the samples, 122 were requested further evaluation. After flow cytometry evaluation and/or genetic diagnostics, we identified one patient with SCID, two patients with XLA, nine patients with SMA [one of whom also had Wiskott-Aldrich Syndrome (WAS)], and eight patients with other medical conditions. The positive predictive values (PPVs) of NBS for SCID, XLA, and SMA were 2.44%, 2.78%, and 100%, respectively. The estimated prevalence rates in the Chinese population were 1 in 103,240 for SCID, 1 in 51,620 for XLA, and 1 in 11,471 for SMA.

CONCLUSION

This study represents the first large-scale screening in mainland China using a TREC/KREC/SMN1 multiplex assay, providing valuable epidemiological data. Our findings suggest that this multiplex assay is an effective screening method for SCID, XLA, and SMA, potentially supporting the universal implementation of NBS programs across China.

A Non-targeted Proteomics Newborn Screening Platform for Inborn Errors of Immunity

PURPOSE

Newborn screening using dried blood spot (DBS) samples for the targeted measurement of metabolites and nucleic acids has made a substantial contribution to public healthcare by facilitating the detection of neonates with genetic disorders. Here, we investigated the applicability of non-targeted quantitative proteomics analysis to newborn screening for inborn errors of immunity (IEIs).

METHODS

DBS samples from 40 healthy newborns and eight healthy adults were subjected to non-targeted proteomics analysis using liquid chromatography-mass spectrometry after removal of the hydrophilic fraction. Subsequently, DBS samples from 43 IEI patients were analyzed to determine whether patients can be identified by reduced expression of disease-associated proteins.

RESULTS

DBS protein profiling allowed monitoring of levels of proteins encoded by 2912 genes, including 1110 listed in the Online Mendelian Inheritance in Man database, in healthy newborn samples, and was useful in identifying patients with IEIs by detecting reduced levels of disease causative proteins and their interacting proteins, as well as cell-phenotypical alterations.

CONCLUSION

Our results indicate that non-targeted quantitative protein profiling of DBS samples can be used to identify patients with IEIs and develop a novel newborn screening platform for genetic disorders.

Protecting children and adults with primary antibody deficiencies against common and emergent pathogens and non-infectious complications

Prevention and treatment of infections are primary goals of treatment of children and adults with primary immune deficiencies due to decreased antibody production. Approaches to these goals include immunoglobulin replacement therapy, vaccination, and prophylactic treatment with antimicrobials. In this review, the infectious and non-infectious complications of antibody deficiencies will be discussed along with the limited number of studies that support the effective use of the available therapies and to drive the development of new therapies. Some illustrative case studies will be presented and the outlook for additional controlled clinical trials and potential for therapies driven by the underlying disease genetics will be considered.

Dietary intakes and nutritional issues in inborn errors of immunity: a systematic review

Introduction

Inborn errors of immunity (IEI) are characterized by an inherited dysregulation or absence of immune system components that can manifest clinically in complications that predispose an individual to feeding difficulties or impaired swallowing, digestion, and absorption. Treatment side-effects or altered requirements may further impair nutritional status. While adequate nutrition is necessary for optimal growth and immune function, little is known about nutritional intakes in IEI, and best practice nutrition guidelines are limited. This review aimed to synthesize current evidence on the dietary intakes, anthropometry and nutritional biochemistry in individuals with an IEI.

Methods

A systematic review of literature published from database inception to March 2023 was conducted in accordance with the PRISMA guidelines. Articles eligible for inclusion reported anthropometric, biochemical, or dietary intake-related measures in pediatric or adult patients with a diagnosed IEI. Identified articles were screened for eligibility; data was synthesized descriptively.

Results

A total of 4488 studies were retrieved of which 34 were included. Across studies, 2894 IEI individuals were included (age range 4 weeks to 83y), predominantly focusing on ataxia telangiectasia (AT) and common variable immunodeficiency (CVID). A significant association between inadequate energy intakes and IEI was identified (n=6 studies); however, there was significant variability in adequacy of macro- and micronutrients across studies. Patients with IEI were at risk of malnutrition (range 30% to 70%); although anthropometric assessment measures were not consistent across studies. Biochemical assessments found patients were also at risk of micronutrient deficiencies including vitamin D.

Discussion

This review identified few studies assessing dietary intakes, anthropometry and nutritional biochemistry in patients with IEI, with considerable heterogeneity across studies. Future longitudinal studies using consistent validated dietary assessment tools and anthropometric measures in diverse IEI patient populations are needed. This review reinforces the need for dietetic input in people with an IEI and the development evidence-based clinical practice guidelines for people with an IEI.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42023412365.

X-linked severe combined immunodeficiency complicated by disseminated bacillus Calmette-Guérin disease caused by a novel pathogenic mutation in exon 3 of the IL2RG gene: a case report and literature review

X-linked severe combined immunodeficiency (X-SCID), caused by mutations in the gamma-chain gene of the interleukin-2 receptor (IL2RG), is a prevalent form of SCID characterized by recurrent and fatal opportunistic infections that occur early in life. The incidence of disseminated bacillus Calmette-Guérin (BCG) disease among children with SCID is much higher than in the general population. Here, we report the case of a 4-month-old male infant who presented with subcutaneous induration, fever, an unhealed BCG vaccination site, and hepatosplenomegaly. Metagenomic next-generation sequencing in blood, and the detection of gastric juice and skin nodule pus all confirmed the infection of Mycobacterium tuberculosis. Lymphocyte subset analysis confirmed the presence of T-B+NK immunodeficiency. Whole-exome and Sanger sequencing revealed a novel microdeletion insertion mutation (c.316_318delinsGTGAT p.Leu106ValfsTer42) in the IL2RG gene, resulting in a rare shift in the amino acid sequence of the coding protein. Consequently, the child was diagnosed with X-SCID caused by a novel mutation in IL2RG, complicated by systemic disseminated BCG disease. Despite receiving systemic anti-infection treatment and four days of hospitalization, the patient died three days after discharge. To the best of our knowledge, this specific IL2RG mutation has not been previously reported. In our systemic review, we outline the efficacy of systemic anti-tuberculosis therapy, hematopoietic stem cell transplantation, and gene therapy in children with SCID and BCG diseases caused by IL2RG gene mutation.

Paving the way in implementation of SCID newborn screening in developing nations: feasibility study and strategies to move forward in Malaysia

Early diagnosis and effective management of Primary immunodeficiency diseases (PIDs), particularly severe combined immunodeficiency (SCID), play a crucial role in minimizing associated morbidities and mortality. Newborn screening (NBS) serves as a valuable tool in facilitating these efforts. Timely detection and diagnosis are essential for swiftly implementing isolation measures and ensuring prompt referral for definitive treatment, such as allogeneic hematopoietic stem cell transplantation. The utilization of comprehensive protocols and screening assays, including T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC), is essential in facilitating early diagnosis of SCID and other PIDs, but their successful application requires clinical expertise and proper implementation strategy. Unfortunately, a notable challenge arises from insufficient funding for the treatment of PIDs. To address these issues, a collaborative approach is imperative, involving advancements in technology, a well-functioning healthcare system, and active engagement from stakeholders. The integration of these elements is essential for overcoming the existing challenges in NBS for PIDs. By fostering synergy between technology providers, healthcare professionals, and governmental stakeholders, we can enhance the efficiency and effectiveness of early diagnosis and intervention, ultimately improving outcomes for individuals with PIDs.

Expanded Newborn Screening for Inborn Errors of Immunity: The Experience of Tuscany

BACKGROUND

Inborn errors of immunity (IEIs) include 485 inherited disorders characterized by an increased susceptibility to life-threatening infectious diseases, autoimmunity, and malignant diseases with a high mortality rate in the first years of life. Severe combined immunodeficiency is the most severe of the IEIs, and its detection should be a primary goal in a newborn screening (NBS) program. The term "actionable" has recently been used for all IEIs with outcomes that can be demonstrably improved through early specialized intervention.

OBJECTIVE

To evaluate the results of the expanded NBS strategy for IEIs in Tuscany Region (Italy), based on T-cell receptor excision circle, kappa recombining excision circle, and tandem mass-based assays.

METHODS

This is a retrospective study collecting data from all infants born in Tuscany from October 10, 2018, to October 10, 2022. Tandem mass assay to identify adenosine deaminase and purine nucleoside phosphorylase deficiency, together with T-cell receptor excision circle and kappa recombining excision circle molecular analysis, was conducted on dried blood spot from the newborns' Guthrie Cards. A new dried blood spot and evaluation by an immunologist were carried out when the results of the first test were outside the diagnostic cutoffs.

RESULTS

A total of 94,319 newborns were evaluated. Referral rates for T-cell recombining excision circles (0.031%) and kappa recombining excision circles (0.074%) in this study are in line with the data available in literature. The results from the expanded NBS strategy revealed an incidence rate of 1 per 9431 affected newborns.

CONCLUSIONS

This work represents the first description of a sustainable and real-life-based expanded NBS program for IEIs with a high diagnostic incidence facilitating prompt management of identified patients.

Newborn screening for inborn errors of immunity: The status worldwide

Background

Newborn screening (NBS) for the early detection of inborn errors of immunity (IEI) has been implemented in a few countries. The objective of this study was to verify the situation and define obstacles to the implementation of NBS worldwide.

Methods

A questionnaire was developed by the Inborn Errors of Immunity Committee of the World Allergy Organization (WAO) with 17 questions regarding NBS for IEI in the physician's workplace, NBS test type, problems hindering NBS implementation, reimbursement for IEI therapy, presence of a national IEI registry, referral centers, molecular diagnosis, hematopoietic stem cell transplantation centers, gene therapy, and immunoglobulin replacement therapy. The survey was sent by email once a week to doctors and others associated with WAO and the main immunology societies worldwide as a Google Form™ to be completed during September and October 2021.

Results

Two hundred twenty-nine questionnaires were completed, of which 216 (94.3%) were completed by physicians. One hundred seventy-six (76.8%) physicians were both allergists and immunologists. The agreement between allergists/immunologists and non-allergists/non-immunologists for the question "Is there NBS for IEI in the country you work in?" was good (κ = 0,64: 95% CI 0.55-0.69). Ninety-eight (42.8%) participants were from Latin America, 35 (15.3%) from North America, 29 (12.6%) from Europe, 18 (7.9%) from Africa, 44 (19.2%) from Asia, and 5 (2.2%) from Oceania. More than half the participants (n = 124, 54.2%) regularly treated patients with IEI, followed by occasional treatment (n = 77, 33.6%), or never (n = 28, 12.2%). Of the respondents, 14.8% reported that their countries performed NBS for IEI, whereas 42.2% reported their countries did not. T-cell receptor excision circles was the most widely used technique in some countries, with 75 (59.9%) for the diagnosis of NBS for IEI, followed by combined use with kappa deleting-recombination excision circles. Only 13 participants (10.3%) underwent neonatal exon screening in their respective countries. Financial and technical issues were among the major obstacles to the implementation of NBS for IEI.

Conclusions

This pilot study showed that few countries have implemented NBS for IEI, despite the presence of immunology referral centers and the availability of hematopoietic stem cell transplantation and intravenous immunoglobulin replacement therapy. The findings highlight the difficulties, mainly financial and technical, hindering wide application of NBS. Sharing experiences, technologies, and resources at the international level can help overcome these difficulties.

The bidirectional association between premenstrual disorders and perinatal depression: A nationwide register-based study from Sweden

BACKGROUND

Premenstrual disorders (PMDs) and perinatal depression (PND) share symptomology and the timing of symptoms of both conditions coincide with natural hormonal fluctuations, which may indicate a shared etiology. Yet, there is a notable absence of prospective data on the potential bidirectional association between these conditions, which is crucial for guiding clinical management. Using the Swedish nationwide registers with prospectively collected data, we aimed to investigate the bidirectional association between PMDs and PND.

METHODS AND FINDINGS

With 1,803,309 singleton pregnancies of 1,041,419 women recorded in the Swedish Medical Birth Register during 2001 to 2018, we conducted a nested case-control study to examine the risk of PND following PMDs, which is equivalent to a cohort study, and transitioned that design into a matched cohort study with onward follow-up to simulate a prospective study design and examine the risk of PMDs after PND (within the same study population). Incident PND and PMDs were identified through clinical diagnoses or prescribed medications. We randomly selected 10 pregnant women without PND, individually matched to each PND case on maternal age and calendar year using incidence density sampling (N: 84,949: 849,482). We (1) calculated odds ratio (OR) and 95% confidence intervals (CIs) of PMDs using conditional logistic regression in the nested case-control study. Demographic factors (country of birth, educational level, region of residency, and cohabitation status) were adjusted for. We (2) calculated the hazard ratio (HR) and 95% CIs of PMDs subsequent to PND using stratified Cox regression in the matched cohort study. Smoking, BMI, parity, and history of psychiatric disorders were further controlled for, in addition to demographic factors. Pregnancies from full sisters of PND cases were identified for sibling comparison, which contrasts the risk within each set of full sisters discordant on PND. In the nested case-control study, we identified 2,488 PMDs (2.9%) before pregnancy among women with PND and 5,199 (0.6%) among controls. PMDs were associated with a higher risk of subsequent PND (OR 4.76, 95% CI [4.52,5.01]; p < 0.001). In the matched cohort with a mean follow-up of 7.40 years, we identified 4,227 newly diagnosed PMDs among women with PND (incidence rate (IR) 7.6/1,000 person-years) and 21,326 among controls (IR 3.8). Compared to their matched controls, women with PND were at higher risk of subsequent PMDs (HR 1.81, 95% CI [1.74,1.88]; p < 0.001). The bidirectional association was noted for both prenatal and postnatal depression and was stronger among women without history of psychiatric disorders (p for interaction < 0.001). Sibling comparison showed somewhat attenuated, yet statistically significant, bidirectional associations. The main limitation of this study was that our findings, based on clinical diagnoses recorded in registers, may not generalize well to women with mild PMDs or PND.

CONCLUSIONS

In this study, we observed a bidirectional association between PMDs and PND. These findings suggest that a history of PMDs can inform PND susceptibility and vice versa and lend support to the shared etiology between both disorders.

Severe combined immunodeficiency diagnosis and genetic defects

Severe combined immunodeficiency (SCID) is a rare and life-threatening genetic disorder that severely impairs the immune system's ability to defend the body against infections. Often referred to as the "bubble boy" disease, SCID gained widespread recognition due to the case of David Vetter, a young boy who lived in a sterile plastic bubble to protect him from germs. SCID is typically present at birth, and it results from genetic mutations that affect the development and function of immune cells, particularly T cells and B cells. These immune cells are essential for identifying and fighting off infections caused by viruses, bacteria, and fungi. In SCID patients, the immune system is virtually non-existent, leaving them highly susceptible to recurrent, severe infections. There are several forms of SCID, with varying degrees of severity, but all share common features. Newborns with SCID often exhibit symptoms such as chronic diarrhea, thrush, skin rashes, and persistent infections that do not respond to standard treatments. Without prompt diagnosis and intervention, SCID can lead to life-threatening complications and a high risk of mortality. There are over 20 possible affected genes. Treatment options for SCID primarily involve immune reconstitution, with the most well-known approach being hematopoietic stem cell transplantation (HSCT). Alternatively, gene therapy is also available for some forms of SCID. Once treated successfully, SCID patients can lead relatively normal lives, but they may still require vigilant infection control measures and lifelong medical follow-up to manage potential complications. In conclusion, severe combined immunodeficiency is a rare but life-threatening genetic disorder that severely compromises the immune system's function, rendering affected individuals highly vulnerable to infections. Early diagnosis and appropriate treatment are fundamental. With this respect, newborn screening is progressively and dramatically improving the prognosis of SCID.

Gene regulation in inborn errors of immunity: Implications for gene therapy design and efficacy

Inborn errors of immunity (IEI) present a unique paradigm in the realm of gene therapy, emphasizing the need for precision in therapeutic design. As gene therapy transitions from broad-spectrum gene addition to careful modification of specific genes, the enduring safety and effectiveness of these therapies in clinical settings have become crucial. This review discusses the significance of IEIs as foundational models for pioneering and refining precision medicine. We explore the capabilities of gene addition and gene correction platforms in modifying the DNA sequence of primary cells tailored for IEIs. The review uses four specific IEIs to highlight key issues in gene therapy strategies: X-linked agammaglobulinemia (XLA), X-linked chronic granulomatous disease (X-CGD), X-linked hyper IgM syndrome (XHIGM), and immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX). We detail the regulatory intricacies and therapeutic innovations for each disorder, incorporating insights from relevant clinical trials. For most IEIs, regulated expression is a vital aspect of the underlying biology, and we discuss the importance of endogenous regulation in developing gene therapy strategies.

Newborn screening for severe combined immunodeficiency and inborn errors of immunity

PURPOSE OF REVIEW

Severe combined immune deficiency (SCID) is the most devastating genetic disease of the immune system with an unfavorable outcome unless diagnosed early in life. Newborn screening (NBS) programs play a crucial role in facilitating early diagnoses and timely interventions for affected infants.

RECENT FINDINGS

SCID marked the pioneering inborn error of immunity (IEI) to undergo NBS, a milestone achieved 15 years ago through the enumeration of T-cell receptor excision circles (TRECs) extracted from Guthrie cards. This breakthrough has revolutionized our approach to SCID, enabling not only presymptomatic identification and prompt treatments (including hematopoietic stem cell transplantation), but also enhancing our comprehension of the global epidemiology of SCID.

SUMMARY

NBS is continuing to evolve with the advent of novel diagnostic technologies and treatments. Following the successful implementation of SCID-NBS programs, a call for the early identification of additional IEIs is the next step, encompassing a broader spectrum of IEIs, facilitating early diagnoses, and preventing morbidity and mortality.

Newborn Screening

The goal of newborn screening is to identify medical conditions that can cause significant morbidity and/or mortality if not treated early in life. Pediatricians often play a vital role in the initial disclosure of newborn screening results and coordination of confirmatory testing, treatment, and referral to specialty care. The goal of this article is to provide an overview of current newborn screening in the United States, focusing on the various disorders, their manifestations, the newborn screening process, the confirmatory testing, and treatments. Some practical considerations will be discussed as well.

The PID Odyssey 2030: outlooks, unmet needs, hurdles, and opportunities - proceedings from the IPOPI global multi-stakeholders' summit (June 2022)

IPOPI held its first Global Multi-Stakeholders' Summit on 23-24 June 2022 in Cascais, Portugal. This IPOPI initiative was designed to set the stage for a stimulating forward-thinking meeting and brainstorming discussion among stakeholders on the future priorities of the PID community. All participants were actively engaged in the entire Summit, bringing provocative questions to ensure a high level of discussion and engagement, and partnered in identifying the outlooks, unmet needs, hurdles and opportunities of PIDs for 2030. The topics that were covered include diagnosis (e.g., newborn screening [NBS], genomic sequencing- including ethical aspects on the application of genomics on NBS, the role of more accurate and timely diagnostics in impacting personalized management), treatment (e.g., the therapeutic evolution of immunoglobulins in a global environment, new therapies such as targeted therapies, new approaches in curative therapies), the interactions of Primary ID with Secondary ID, Autoinflammatory Diseases and other diseases as the field experiences an incessant evolution, and also the avenues for research in the field of humanities and human sciences such as Patient-Reported Outcome Measures (PROMs), Patient-Reported Experience Measures (PREMs), and Health-Related Quality Of Life (HRQoL). During this meeting, all participants contributed to the drafting of recommendations based on our common understanding of the future opportunities, challenges, and scenarios. As a collection of materials, perspectives and summaries, they are succinct and impactful and may help determine some of the next key steps for the PID community.

Development of a Model for Quantitative Assessment of Newborn Screening in Japan Using the Analytic Hierarchy Process

Whether or not conditions should be included in publicly funded newborn screening (NBS) programs should be discussed according to objective and transparent criteria. Certain criteria have been developed for the introduction of NBS programs in the context of individual countries; however, there are no standard selection criteria for NBS programs in Japan. This study aimed to develop a quantitative scoring model to assess newborn screening that incorporates the views of a variety of stakeholders in Japan. The five recommended eligibility criteria for NBS were stratified based on previous studies and expert opinions, using the analytic hierarchy process. We conducted a cross-sectional, web-based questionnaire targeting a wide range of people involved in NBS to investigate pairwise comparisons of the evaluation items between February and April of 2022. There were 143 respondents. Most of our respondents (44.1%) were physicians. Fifty-eight respondents (40.6%) had been engaged in NBS-related research or work for more than 10 years. The distribution of allocation points was the highest for 'intervention', 'screening test', 'follow-up setting', 'economic evaluation', and 'disease/condition', in that order. The algorithm in this study will guide decision makers in collecting and evaluating objective data, thus enabling transparent discussions to occur.

A multicenter prospective study of next-generation sequencing-based newborn screening for monogenic genetic diseases in China

BACKGROUND

Newborn screening (NBS) is an important and successful public health program that helps improve the long-term clinical outcomes of newborns by providing early diagnosis and treatment of certain inborn diseases. The development of next-generation sequencing (NGS) technology provides new opportunities to expand current newborn screening methodologies.

METHODS

We designed a a newborn genetic screening (NBGS) panel targeting 135 genes associated with 75 inborn disorders by multiplex PCR combined with NGS. With this panel, a large-scale, multicenter, prospective multidisease analysis was conducted on dried blood spot (DBS) profiles from 21,442 neonates nationwide.

RESULTS

We presented the positive detection rate and carrier frequency of diseases and related variants in different regions; and 168 (0.78%) positive cases were detected. Glucose-6-Phosphate Dehydrogenase deficiency (G6PDD) and phenylketonuria (PKU) had higher prevalence rates, which were significantly different in different regions. The positive detection of G6PD variants was quite common in south China, whereas PAH variants were most commonly identified in north China. In addition, NBGS identified 3 cases with DUOX2 variants and one with SLC25A13 variants, which were normal in conventional NBS, but were confirmed later as abnormal in repeated biochemical testing after recall. Eighty percent of high-frequency gene carriers and 60% of high-frequency variant carriers had obvious regional differences. On the premise that there was no significant difference in birth weight and gestational age, the biochemical indicators of SLC22A5 c.1400C > G and ACADSB c.1165A > G carriers were significantly different from those of non-carriers.

CONCLUSIONS

We demonstrated that NBGS is an effective strategy to identify neonates affected with treatable diseases as a supplement to current NBS methods. Our data also showed that the prevalence of diseases has significant regional characteristics, which provides a theoretical basis for screening diseases in different regions.

Genomic-Based Newborn Screening for Inborn Errors of Immunity: Practical and Ethical Considerations

Inborn errors of immunity (IEI) are a group of over 450 genetically distinct conditions associated with significant morbidity and mortality, for which early diagnosis and treatment improve outcomes. Newborn screening for severe combined immunodeficiency (SCID) is currently underway in several countries, utilising a DNA-based technique to quantify T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC). This strategy will only identify those infants with an IEI associated with T and/or B cell lymphopenia. Other severe forms of IEI will not be detected. Up-front, first-tier genomic-based newborn screening has been proposed as a potential approach by which to concurrently screen infants for hundreds of monogenic diseases at birth. Given the clinical, phenotypic and genetic heterogeneity of IEI, a next-generation sequencing-based newborn screening approach would be suitable. There are, however, several ethical, legal and social issues which must be evaluated in detail prior to adopting a genomic-based newborn screening approach, and these are discussed herein in the context of IEI.

Successful TCRαβ/CD19-Depleted Hematopoietic Cell Transplantation for a Patient With Artemis Deficiency

Artemis deficiency is characterized by DNA double-strand breaks repairing dysfunction and increased sensitivity to ionizing radiation and alkylating reagents. We describe the first successful case of T-cell receptor [TCR]αβ/CD19-depleted hematopoietic cell transplantation [HCT] for Artemis deficiency in Japan. A 6-month-old Korean boy was diagnosed with Artemis-deficient severe combined immunodeficiency. He had no human leukocyte antigen (HLA)-matched sibling or unrelated donor. Therefore, TCRαβ/CD19-depleted HCT from his haploidentical mother was performed. Despite mixed chimerism in whole blood, T cells achieved complete donor chimerism 6 months after HCT. TCRαβ/CD19-depleted HCT could be an effective treatment for patients with radiation-sensitive severe combined immunodeficiency.

Positive Newborn Screening for Severe Combined Immunodeficiency: What Should the Pediatrician Do?

Severe combined immunodeficiency (SCID) is a group of diseases characterized by low T-cell count and impaired T-cell function, resulting in severe cellular and humoral immune defects. If not diagnosed and treated promptly, infants affected by this condition can develop severe infections which will result in death. Delayed treatment can markedly reduce the survival outcome of infants with SCID. T-cell receptor excision circle (TREC) levels are measured on newborn screening to promptly identify infants with SCID. It is important for primary care providers and pediatricians to understand the approach to managing infants with positive TREC-based newborn screening as they may be the first contact for infants with SCID. Primary care providers should be familiar with providing anticipatory guidance to the family in regard to protective isolation, measures to minimize the risk of infection, and the coordination of care with the SCID coordinating center team of specialists. In this article, we use case-based scenarios to review the principles of TREC-based newborn screening, the genetics and subtypes of SCID, and management for an infant with a positive TREC-based newborn screen.

FOXN1 Gene Considerations in Severe Combined Immunodeficiency Treatment in Children

Forkheadbox N1 (FOXN1) gene mutation in humans is a rare cause of thymic hypoplasia and T cell immunodeficiency. This gene is the master transcriptional regulator of thymic epithelial cells and disruptions have been described in consequence to a variety of antepartum complications. FOXN1 mutation-mediated immune deficiency is typically associated with severe combined immunodeficiency and alopecia universalis (SCID/NUDE phenotypes) with homozygous alterations in human animal models. Less common, however, FOXN1 alterations can occur in a heterozygous form and provide a distinct phenotype of severe combined immunodeficiency (SCID) without alopecia. Here, we present one such case of a Caucasian child born with heterozygous FOXN1 mutation, first presenting with undetectable T cell levels at newborn screen. He was confirmed to have FOXN1 immunodeficiency in the heterozygous form through genetic testing. Early identification and initiation of appropriate interventions are crucial to reduce mortality from opportunistic pathogens associated with immunodeficiency. Furthermore, we need to appreciate the less common presentations of established diseases among young patients.

Candidate genes and sequence variants for susceptibility to mycobacterial infection identified by whole-exome sequencing

Inborn errors of immunity are known to influence susceptibility to mycobacterial infections. The aim of this study was to characterize the genetic profile of nine patients with mycobacterial infections (eight with BCGitis and one with disseminated tuberculosis) from the Republic of Moldova using whole-exome sequencing. In total, 12 variants in eight genes known to be associated with Mendelian Susceptibility to Mycobacterial Disease (MSMD) were detected in six out of nine patients examined. In particular, a novel splice site mutation c.373–2A>C in STAT1 gene was found and functionally confirmed in a patient with disseminated tuberculosis. Trio analysis was possible for seven out of nine patients, and resulted in 23 candidate variants in 15 novel genes. Four of these genes - GBP2, HEATR3, PPP1R9B and KDM6A were further prioritized, considering their elevated expression in immune-related tissues. Compound heterozygosity was found in GBP2 in a single patient, comprising a maternally inherited missense variant c.412G>A/p.(Ala138Thr) predicted to be deleterious and a paternally inherited intronic mutation c.1149+14T>C. Functional studies demonstrated that the intronic mutation affects splicing and the level of transcript. Finally, we analyzed pathogenicity of variant combinations in gene pairs and identified five patients with putative oligogenic inheritance. In summary, our study expands the spectrum of genetic variation contributing to susceptibility to mycobacterial infections in children and provides insight into the complex/oligogenic disease-causing mode.

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.

VIPPID: a gene-specific single nucleotide variant pathogenicity prediction tool for primary immunodeficiency diseases

Distinguishing pathogenic variants from non-pathogenic ones remains a major challenge in clinical genetic testing of primary immunodeficiency (PID) patients. Most of the existing mutation pathogenicity prediction tools treat all mutations as homogeneous entities, ignoring the differences in characteristics of different genes, and use the same model for genes in different diseases. In this study, we developed a single nucleotide variant (SNV) pathogenicity prediction tool, Variant Impact Predictor for PIDs (VIPPID; https://mylab.shinyapps.io/VIPPID/), which was tailored for PIDs genes and used a specific model for each of the most prevalent PID known genes. It employed a Conditional Inference Forest model and utilized information of 85 features of SNVs and scores from 20 existing prediction tools. Evaluation of VIPPID showed that it had superior performance (area under the curve = 0.91) over non-specific conventional tools. In addition, we also showed that the gene-specific model outperformed the non-gene-specific models. Our study demonstrated that disease-specific and gene-specific models can improve SNV pathogenicity prediction performance. This observation supports the notion that each feature of mutations in the model can be potentially used, in a new algorithm, to investigate the characteristics and function of the encoded proteins.

Genetic Counselling: the biomedical bridge between molecular diagnosis and precision treatment

Background

Since the development of genomics, we are able to understand backgrounds of differential pathogenicity of metabolic disorders. Molecular diagnosis has become inevitable for metabolic, neuro-psychiatric and genetic disorders due to highly overlapping pathophysiological symptoms. The present lacuna between clinical prescription and molecular diagnosis is very prominent and can only be filled up through experts who can function as the bridge in between.

Main body

In this present review, the authors tried to focus on the role of genetic counselors in disease diagnosis as well as scopes of disease biology in utilizing the expertise of genetic professional for precision treatments of patients. We summarized four major disease areas, Cancer management, Obstetrics and Gynecology, Newborn Screening and Rare Genetic Disorders, where molecular diagnosis and genetic counseling can highly support the clinicians in precision treatment of the patients. Idiopathic reproductive failures, clinically overlapping neuro-psychiatric disorders, chromosomal aberrations in progressing tumors, rare genetic disorders all the disease areas can find out fruitful intervention when enlightened with molecular diagnosis and genetic counseling. Though, genetic counseling is commonly practiced in intervening reproductive problems, newborn screening and cancer, still the scope of genetic counselor in successfully intervening multiple rare genetic diseases as well as common hereditary life style disorders, remain extremely high.

Conclusion

The liaison between clinicians and geneticists, specifically clinical prescription and genetic diagnosis is one of the key demands of present age, which can be successfully fulfilled by the genetic counselors. For these reasons, genetic counseling is predicted as the biomedical career of future due to being in the vital position for successful implementation of precision medicine.

Implementation of TREC/KREC detection protocol for newborn SCID screening in Bulgaria: a pilot study

Neonatal screening for inborn errors of immunity (IEI), based on quantification of T-cell-receptor- excision circles (TRECs) and kappa-deleting recombination-excision circles (KRECs) from dried blood spots (DBS), allows early diagnosis and improved outcomes for the affected children. Determination of TREC/KREC levels from prospectively collected newborns' Guthrie cards and from DBS samples of patients with confirmed IEI was done using a commercial kit. Retrospective assessment of flow cytometry evaluation of TREC/KREC correspondence with lymphocyte subpopulations and evaluation of the correlations between TREC and KREC with immune cells, based on the data from patients with suspected or confirmed immune disorders, were conducted. 2,228 Guthrie cards were tested, 1276 for TREC only and 952 for both TREC and KREC. Eight newborns (0.36%) were TREC positive and 10 (1.05%) had KREC below the cut-off. The re-testing rate was 1.88%. Retrospective analysis demonstrated that the TREC/KREC assay identifies 100% of severe combined immune deficiencies (SCID) cases when DBS were collected at birth. Correlation analysis showed moderate significant correlations between TREC and the absolute numbers of CD4 cells (r = 0.634, p < 0.01) and total T cells (r = 0.536, p < 0.01). The ability of KREC levels to predict abnormal absolute (AUC of 0.772) and relative (AUC 0.731) levels of B cells was demonstrated.

Analysis of the TREC and KREC Levels in the Dried Blood Spots of Healthy Newborns with Different Gestational Ages and Weights

Inborn errors of immunity can be detected by evaluating circular DNA (cDNA) fragments of T- and B-cell receptors (TREC and KREC) resulting from the receptor gene rearrangement in T and B cells. Maturation and activation of the fetal immune system is known to proceed gradually according to the gestational age, which highlights the importance of the immune status in premature infants at different gestational ages. In this article, we evaluated TREC and KREC levels in infants of various gestational ages by real-time PCR with taking into account the newborn’s weight and sex. The 95% confidence intervals for TREC and KREC levels (expressed in the number of cDNA copies per 105 cells) were established for different gestational groups. The importance of studying immune system development in newborns is informed by the discovered dependence of the level of naive markers on the gestational stage in the early neonatal period.

VPMBench: a test bench for variant prioritization methods

Background

Clinical diagnostics of whole-exome and whole-genome sequencing data requires geneticists to consider thousands of genetic variants for each patient. Various variant prioritization methods have been developed over the last years to aid clinicians in identifying variants that are likely disease-causing. Each time a new method is developed, its effectiveness must be evaluated and compared to other approaches based on the most recently available evaluation data. Doing so in an unbiased, systematic, and replicable manner requires significant effort.

Results

The open-source test bench “VPMBench” automates the evaluation of variant prioritization methods. VPMBench introduces a standardized interface for prioritization methods and provides a plugin system that makes it easy to evaluate new methods. It supports different input data formats and custom output data preparation. VPMBench exploits declaratively specified information about the methods, e.g., the variants supported by the methods. Plugins may also be provided in a technology-agnostic manner via containerization.

Conclusions

VPMBench significantly simplifies the evaluation of both custom and published variant prioritization methods. As we expect variant prioritization methods to become ever more critical with the advent of whole-genome sequencing in clinical diagnostics, such tool support is crucial to facilitate methodological research.

Future Perspectives of Newborn Screening for Inborn Errors of Immunity

Newborn screening (NBS) programs continue to expand due to innovations in both test methods and treatment options. Since the introduction of the T-cell receptor excision circle (TREC) assay 15 years ago, many countries have adopted screening for severe combined immunodeficiency (SCID) in their NBS program. SCID became the first inborn error of immunity (IEI) in population-based screening and at the same time the TREC assay became the first high-throughput DNA-based test in NBS laboratories. In addition to SCID, there are many other IEI that could benefit from early diagnosis and intervention by preventing severe infections, immune dysregulation, and autoimmunity, if a suitable NBS test was available. Advances in technologies such as KREC analysis, epigenetic immune cell counting, protein profiling, and genomic techniques such as next-generation sequencing (NGS) and whole-genome sequencing (WGS) could allow early detection of various IEI shortly after birth. In the next years, the role of these technical advances as well as ethical, social, and legal implications, logistics and cost will have to be carefully examined before different IEI can be considered as suitable candidates for inclusion in NBS programs.

Second Tier Testing to Reduce the Number of Non-actionable Secondary Findings and False-Positive Referrals in Newborn Screening for Severe Combined Immunodeficiency

PURPOSE

Newborn screening (NBS) for severe combined immunodeficiency (SCID) is based on the detection of T-cell receptor excision circles (TRECs). TRECs are a sensitive biomarker for T-cell lymphopenia, but not specific for SCID. This creates a palette of secondary findings associated with low T-cells that require follow-up and treatment or are non-actionable. The high rate of (non-actionable) secondary findings and false-positive referrals raises questions about the harm-benefit-ratio of SCID screening, as referrals are associated with high emotional impact and anxiety for parents.

METHODS

An alternative quantitative TREC PCR with different primers was performed on NBS cards of referred newborns (N = 56) and epigenetic immune cell counting was used as for relative quantification of CD3 + T-cells (N = 59). Retrospective data was used to determine the reduction in referrals with a lower TREC cutoff value or an adjusted screening algorithm.

RESULTS

When analyzed with a second PCR with different primers, 45% of the referrals (25/56) had TREC levels above cutoff, including four false-positive cases in which two SNPs were identified. With epigenetic qPCR, 41% (24/59) of the referrals were within the range of the relative CD3 + T-cell counts of the healthy controls. Lowering the TREC cutoff value or adjusting the screening algorithm led to lower referral rates but did not prevent all false-positive referrals.

CONCLUSIONS

Second tier tests and adjustments of cutoff values or screening algorithms all have the potential to reduce the number of non-actionable secondary findings in NBS for SCID, although second tier tests are more effective in preventing false-positive referrals.

NBAS Variants Are Associated with Quantitative and Qualitative NK and B Cell Deficiency

PURPOSE

Biallelic pathogenic NBAS variants manifest as a multisystem disorder with heterogeneous clinical phenotypes such as recurrent acute liver failure, growth retardation, and susceptibility to infections. This study explores how NBAS-associated disease affects cells of the innate and adaptive immune system.

METHODS

Clinical and laboratory parameters were combined with functional multi-parametric immunophenotyping methods in fifteen NBAS-deficient patients to discover possible alterations in their immune system.

RESULTS

Our study revealed reduced absolute numbers of mature CD56dim natural killer (NK) cells. Notably, the residual NK cell population in NBAS-deficient patients exerted a lower potential for activation and degranulation in response to K562 target cells, suggesting an NK cell-intrinsic role for NBAS in the release of cytotoxic granules. NBAS-deficient NK cell activation and degranulation was normalized upon pre-activation by IL-2 in vitro, suggesting that functional impairment was reversible. In addition, we observed a reduced number of naïve B cells in the peripheral blood associated with hypogammaglobulinemia.

CONCLUSION

In summary, we demonstrate that pathogenic biallelic variants in NBAS are associated with dysfunctional NK cells as well as impaired adaptive humoral immunity.

Complement multiplex testing: Concept, promises and pitfalls

Complement is a complex system. This complexity becomes more obvious when looking at complement analysis in health and disease, where one presentation can require a number of measurements to understand the full role of this cascade in the disease. The current state of clinical testing requires multiple tests to cover the whole of the complement cascade. There is a clear potential for multiplex testing to help address this need for comprehensive analysis of the state of complement deficiency, activation or inhibition. Fortunately, there are a number of potential methods for multiplex analysis, each with advantages and disadvantages that need to be considered in light of the intricacy of the complement cascade and its interconnection to other systems. Despite the complexities of such methods several groups have started utilizing multiplex analysis for research and even for diagnostic testing. The potential methods, current successes, and the type of testing that needs to be streamlined are reviewed in this text.

Modern diagnostic capabilities of neonatal screening for primary immunodeficiencies in newborns

Population screening of newborns is an extremely important and informative diagnostic approach that allows early identification of babies who are predisposed to the development of a number of serious diseases. Some of these diseases are known and have effective treatment methods. Neonatal screening enables the early diagnosis and subsequent timely initiation of therapy. This helps to prevent serious complications and reduce the percentage of disability and deaths among newborns and young children. Primary immunodeficiency diseases and primary immunodeficiency syndrome (PIDS) are a heterogeneous group of diseases and conditions based on impaired immune system function associated with developmental defects and characterized by various combinations of recurrent infections, development of autoimmune and lymphoproliferative syndromes (genetic defects in apoptosis, gene mutation Fas receptor or ligand), granulomatous process, and malignant neoplasms. Most of these diseases manifest in infancy and lead to serious illness, disability, and high mortality rates. Until recently, it was impossible to identify children with PIDS before the onset of the first clinical symptoms, which are usually accompanied by complications in the form of severe coinfections of a viral-bacterial-fungal etiology. Modern advances in medical laboratory technology have allowed the identification of children with severe PIDS, manifested by T- and/or B-cell lymphopenia and other disorders of the immune system. This review discusses the main existing strategies and directions used in PIDS screening programs for newborns, including approaches to screening based on excision of T-cell receptors and kappa-recombination excision circles, as well as the potential role and place of next-generation sequencing technology to increase the diagnostic accuracy of these diseases.

Clean up by aisle 2: roles for IL-2 receptors in host defense and tolerance

Although IL-2 was first recognized as growth factor for T cells, it is now also appreciated to be a key regulator of T cells through its effects on regulatory T cells (Treg). The IL-2 receptor (IL-2R) subunits' different (i) ligand affinities, (ii) dimerization or trimerization relationships with other cytokine subunits, (iii) expression across multiple cell types, and (iv) downstream signaling effects, largely dictate cellular tolerance and antimicrobial processes. Defects in IL-2Rγ result in profound and almost universally fatal immune deficiency, unless treated with hematopoietic stem cell transplantation (HSCT). Defects in IL-2Rα and IL-2Rβ result in more limited infection susceptibility, particularly to herpesviruses. However, the most prominent clinical symptomatology for IL-2Rα and IL-2Rβ defects include multi-organ autoimmunity and inflammation, consistent with the critical role of IL-2 in establishing and maintaining immune tolerance. Here, we review how we have arrived at our current understanding of the complex roles of IL-2/2R in host defense and tolerance focusing on the insights gained from human clinical immunology.

Newborn screening system: Safety, technology, advocacy

Newborn screening (NBS) is more than 50 years old and has proven to be a powerful and successful public health system. NBS must be regarded as a system and not simply as a test. We need to work as a community to improve the culture of safety for the NBS system and thereby to reduce the risk of babies being missed by the NBS system. Adding new technologies will not prevent system failures; that will require adherence to the culture of safety. Some have argued that every newborn should have their genome sequenced at birth and this sequencing could be part of NBS. However, NBS has depended on biomarker phenotypes throughout its history and our understanding of the relationships between genotype and phenotype is imperfect. Therefore, we should avoid being seduced by genomic sequencing technology and continue to focus on phenotypic biomarkers in NBS.

TREC/KREC levels in children with ataxia-telangiectasia

The aim of the study was to determine the TREC/KREC levels in the patients diagnosed with ataxia-telangiectasia (AT) and to establish their informative value for early diagnosis of this pathology. TRECs and KREC assay was performed using real-time polymerase chain reaction on the DNA of 25 patients diagnosed with AT aged 3 to 14 years and of 173 healthy individuals of the control group aged 1 to 12 years. Clinical and laboratory characteristics of patients were ascertained using their medical records. In the patients with AT, the mean level of TRECs was 542.84 per 10⁶ cells, ranging from 4 to 4720, while mean level of KRECs was 1317.64 per 10⁶ cells, ranging from 146 to 9300. In 84% of the patients, TREC levels were less than 1000, which was significantly lower than in the control group, while KREC levels were reduced in 48% of the patients. A correlation was found between the levels of TREC and the absolute values of CD4 (r = 0.5455). Measurement of TREC/KREC levels opens new opportunities for early AT detection in children as a part of the newborn screening. Reduced time to diagnosis will allow to carry out timely in-depth immunological and genetic testing, prevent the development of severe infections, and improve quality of life.

Implementation of SCID Screening in Denmark

Screening for SCID was added to the Danish Neonatal Screening Program in February 2020. The screening uses a RealtimePCR kit and we here present the results and experiences with the validation of the kit and the first 10 months of screening.

The New "Wholly Trinity" in the Diagnosis and Management of Inborn Errors of Immunity

The field of immunology has a rich and diverse history, and the study of inborn errors of immunity (IEIs) represents both the "cake" and the "icing on top of the cake," as it has enabled significant advances in our understanding of the human immune system. This explosion of knowledge has been facilitated by a unique partnership, a triumvirate formed by the physician who gathers detailed immunological and clinical phenotypic information from, and shares results with, the patient; the laboratory scientist/immunologist who performs diagnostic testing, as well as advanced functional correlative studies; and the genomics scientist/genetic counselor, who conducts and interprets varied genetic analyses, all of which are essential for dissecting constitutional genetic disorders. Although the basic principles of clinical care have not changed in recent years, the practice of clinical immunology has changed to reflect the prodigious advances in diagnostics, genomics, and therapeutics. An "omic/tics"-centric approach to IEI reflects the tremendous strides made in the field in the new millennium with recognition of new disorders, characterization of the molecular underpinnings, and development and implementation of personalized treatment strategies. This review brings renewed attention to bear on the indispensable "trinity" of phenotypic, genomic, and immunological analyses in the diagnosis, management, and treatment of IEIs.

Crohn's-like Enteritis in X-Linked Agammaglobulinemia: A Case Series and Systematic Review

BACKGROUND

X-linked agammaglobulinemia (XLA) is an inherited primary immunodeficiency that usually manifests clinically with recurrent sinopulmonary infections. Gastrointestinal manifestations are mostly driven by acute infections and disturbed mucosal immunity, but there is a notable prevalence of inflammatory bowel disease (IBD). Differentiating between XLA-associated enteritis, which can originate from recurrent infections, and IBD can be diagnostically and therapeutically challenging.

OBJECTIVE

This study presents a critical appraisal of the clinical, radiological, endoscopic, and histological features associated with XLA-associated Crohn disease (CD)-like enteritis.

METHODS

We report 3 cases and performed a systematic review of the literature describing the diagnoses and outcomes.

RESULTS

An XLA-related enteropathy presented in adolescence with an ileocolonic CD-like phenotype without perianal disease. Abdominal pain, noninfectious diarrhea, and weight loss were the most common symptoms. Imaging and endoscopic findings closely resemble CD. However, histologically, it presents without nodular lymphoid hyperplasia and only 2 studies reported the presence of granulomas. In addition, in XLA-associated enteritis, immunohistochemistry showed the absence or marked reduction in B cells and plasma cells.

CONCLUSIONS

An XLA-associated enteritis is a distinct pathological process that presents clinically in a manner similar to ileocolonic CD. It is important to evaluate for infectious diarrhea, which is common in XLA and can mimic IBD clinically. Complete multidisciplinary evaluation is, therefore, recommended for XLA patients with persistent gastrointestinal symptoms. Although more research is needed, therapeutic selection for XLA-associated enteritis is like that of IBD, and the possible risk of drug interactions and complications from increasing immunosuppression should be considered.

Targeted genome editing for the correction or alleviation of primary Immunodeficiencies

Primary immunodeficiencies (PID) are a growing list of unique disorders that result in a failure of the innate/adaptive immune systems to fully respond to disease or infection. PIDs are classified into five broad categories; B cell disorders, combined B and T cell disorders, phagocytic disorders, complement disorders, and disorders with recurrent fevers and inflammation. Many of these disorders, such as X-SCID, WAS, and CGD lead to early death in children if intervention is not implemented. At present, the predominant method of curative therapy remains an allogeneic transplant from a healthy donor, however many complications and limitations exist with his therapy such as availability of donors, graft vs host disease, graft rejection, and infection. More recently, gene therapy using viral based complementation vectors have successfully been implemented to functionally correct patient cells in an autologous transplant, but these methods carry significant risks, including insertional mutagenesis, and provide non-physiological gene expression. For these reasons, gene-editing reagents such as targeted nucleases, base editors (BE), and prime editors (PE) are being explored. The BE and PE tools, sometimes referred to as digital editors, are of very high interest as they provide both enhanced molecular specificity and do not rely on DNA repair pathways after DSBs to change individual base pairs or directly replace DNA sequences responsible for pathogenic phenotypes. With this in mind the purpose of this chapter is to highlight some of the most common PIDs found within the human population, discuss successes and shortcomings of previous intervention strategies, and highlight how the next generation of gene-editing tools may be deployed to directly repair the underlying genetic causes of this class of disease.

Primary immunodeficiency-related genes in neonatal intensive care unit patients with various genetic immune abnormalities: a multicentre study in China

Objectives

The present phenotype-based disease classification causes ambiguity in diagnosing and determining timely, effective treatment options for primary immunodeficiency (PID). In this study, we aimed to examine the characteristics of early-onset PID and proposed a JAK-STATopathy subgroup based on their molecular defects.

Methods

We reviewed 72 patients (< 100 days) retrospectively. These patients exhibited various immune-related phenotypes and received a definitive molecular diagnosis by next-generation sequencing (NGS)-based tests. We evaluated the PID-causing genes and clinical parameters. We assessed the genes that shared the JAK-STAT signalling pathway. We also examined the potential high risks related to the 180-day death rate.

Results

We identified PID disorders in 25 patients (34.72%, 25/72). The 180-day mortality was 26.39% (19/72). Early onset of disease (cut-off value of 3.5 days of age) was associated with a high 180-day death rate (P = 0.009). Combined immunodeficiency with associated or syndromic features comprised the most common PID class (60.00%, 15/25). Patients who presented life-threatening infections were most likely to exhibit PID (odds ratio [OR] = 2.864; 95% confidence interval [CI]: 1.047-7.836). Twelve out of 72 patients shared JAK-STAT pathway defects. Seven JAK-STATopathy patients were categorised as PID. They were admitted to NICUs as immunological emergencies. Most of them experienced severe infections and thrombocytopenia, with 4 succumbing to an early death.

Conclusions

This study confirmed that NGS can be utilised as an aetiological diagnostic method of complex immune-related conditions in early life. Through the classification of PID as pathway-based subtypes, we see an opportunity to dissect the heterogeneity and to direct targeted therapies.

An appraisal of the Wilson & Jungner criteria in the context of genomic-based newborn screening for inborn errors of immunity

Wilson and Jungner's recommendations for population-based screening have been used to guide decisions regarding candidate disease inclusion in newborn screening programs for the past 50 years. The advent of genomic-based technologies, including next-generation sequencing and its potential application to newborn screening, along with a changing landscape in terms of modern clinical practice and ethical, social, and legal considerations has led to a call for review of these criteria. Inborn errors of immunity (IEI) are a heterogeneous group of more than 450 genetically determined disorders of immunity, which are associated with significant morbidity and mortality, particularly where diagnosis and treatment are delayed. We argue that in addition to screening for severe combined immunodeficiency disease, which has already been initiated in several countries, other clinically significant IEI should be screened for at birth. Because of disease heterogeneity and identifiable genetic targets, a next-generation sequencing-based screening approach would be most suitable. A combination of worldwide experience and technological advances has improved our ability to diagnose and effectively treat patients with IEI. Considering IEI in the context of updated recommendations for population-based screening supports their potential inclusion as disease targets in newborn screening programs.

Gut Microbiota-Host Interactions in Inborn Errors of Immunity

Inborn errors of immunity (IEI) are a group of disorders that are mostly caused by genetic mutations affecting immune host defense and immune regulation. Although IEI present with a wide spectrum of clinical features, in about one third of them various degrees of gastrointestinal (GI) involvement have been described and for some IEI the GI manifestations represent the main and peculiar clinical feature. The microbiome plays critical roles in the education and function of the host's innate and adaptive immune system, and imbalances in microbiota-immunity interactions can contribute to intestinal pathogenesis. Microbial dysbiosis combined to the impairment of immunosurveillance and immune dysfunction in IEI, may favor mucosal permeability and lead to inflammation. Here we review how immune homeostasis between commensals and the host is established in the gut, and how these mechanisms can be disrupted in the context of primary immunodeficiencies. Additionally, we highlight key aspects of the first studies on gut microbiome in patients affected by IEI and discuss how gut microbiome could be harnessed as a therapeutic approach in these diseases.