TREC/KREC Newborn Screening followed by Next-Generation Sequencing for Severe Combined Immunodeficiency in Japan

Non-conditioned cord blood transplantation for infection control in athymic CHARGE syndrome

OBJECTIVE

CHARGE syndrome is a congenital malformation syndrome caused by heterozygous mutations in the CHD7 gene. Severe combined immunodeficiency (SCID) arises from congenital athymia called CHARGE/complete DiGeorge syndrome. While cultured thymus tissue implantation (CTTI) provides an immunological cure, hematopoietic cell transplantation (HCT) is an alternative option for immuno-reconstitution of affected infants. We aimed to clarify the clinical outcomes of patients with athymic CHARGE syndrome after HCT.

METHODS

We studied the immunological reconstitution and outcomes of four patients who received non-conditioned unrelated donor cord blood transplantation (CBT) at Kyushu University Hospital from 2007 to 2022. The posttransplant outcomes were compared with the outcomes of eight reported patients.

RESULTS

Four index cases received CBT 70-144 days after birth and had no higher than grade II acute graft-versus-host disease. One infant was the first newborn-screened athymic case in Japan. They achieved more than 500/μL naïve T cells with balanced repertoire 1 month post transplant, and survived more than 12 months with home care. Twelve patients including the index cases received HCT at a median 106 days after birth (range: 70-195 days). One-year overall survival rate was significantly higher in patients who underwent non-conditioned HCT than in those who received conditioned HCT (100% vs. 37.5%, p = .02). Nine patients died, and the major cause of death was cardiopulmonary failure.

CONCLUSIONS

Athymic infants achieved a prompt reconstitution of non-skewing naïve T cells after non-conditioned CBT that led to home care in infancy without significant infections. Non-conditioned CBT is a useful bridging therapy for newborn-screened cases toward an immunological cure by CTTI.

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.

Critical diseases in neonates after discharge home from birth hospital: A retrospective study from a tertiary hospital in Japan

INTRODUCTION

To establish actionable neonatal screening during the first month of life, we investigated critical diseases in seemingly healthy newborns discharged from birth hospitals.

METHODS

This retrospective study enrolled previously healthy full-term infants who visited our hospital, a tertiary hospital in Japan, from home between 5 and 28 days after birth from 2009 to 2018. Infants with known perinatal or congenital diseases, positive newborn screening results, or accidental injuries were excluded. Data were collected from electronic medical records, including principal diagnosis, clinical details, and prognosis at 18 months of age.

RESULTS

Ninety-seven (58 %) of 168 eligible neonates were admitted to the hospital, and 71 (42 %) were not. The median admission rate in patients with disease onset at ≤14 days after birth (80 %) was significantly higher than that in patients with disease onset at ≥15 days (42 %). Among 45 patients who received intensive medical care, 5 died and 10 developed neurodevelopmental sequelae. Four of 5 patients died by 100 days. Among 25 diseases treated in intensive care unit, 17 (68 %) diseases had a prevalence of <1 per 2000 live births. The commonly used diagnostic methods were imaging (n = 58, 35 %) and physical examination (n = 34, 20 %).

CONCLUSION

Critical diseases due to rare and heterogeneous causes in ostensibly healthy newborns occurred predominantly in the first two weeks of life. Optimal newborn screening and health check-up protocols may benefit from the wide spectrum of life-threatening diseases occurring in home after birth.

Efficient screening strategies for severe combined immunodeficiencies in newborns

INTRODUCTION

Severe combined immunodeficiency (SCID) is one of the most severe forms of inborn errors of immunity (IEI), affecting both cellular and humoral immunity. Without curative treatment such as hematopoietic stem cell transplantation or gene therapy, affected infants die within the first year of life. Due to the severity of the disease, asymptomatic status early in life, and improved survival in the absence of pretransplant infections, SCID was considered a suitable candidate for newborn screening (NBS).

AREAS COVERED

Many countries have introduced SCID screening based on T-cell receptor excision circle (TREC) detection in their NBS programs. Screening an entire population is a radical departure from previous paradigms in the field of immunology. Efficient screening strategies are cost-efficient and balance high sensitivity while preventing high numbers of referrals. NBS for SCID is accompanied by (actionable) secondary findings, but many NBS programs have optimized their screening strategy by adjusting algorithms or including second-tier tests. Harmonization of screening terminology is of great importance for international shared learning.

EXPERT OPINION

The expansion of NBS is driven by the development of new test modalities and treatment options. In the near future, other techniques such as next-generation sequencing will pave the way for NBS of other IEI. Exciting times await for population-based screening programs.

Clinical and Genetic Characterization of Patients with Artemis Deficiency in Japan

PURPOSE

Artemis is an exonuclease essential for V(D)J recombination and repair of DNA double-stranded breaks. Pathogenic variants in DCLRE1C encoding Artemis cause T^-B^-NK⁺ severe combined immunodeficiency (SCID), and patients with Artemis-deficient SCID (ART-SCID) require definitive therapy with allogeneic hematopoietic cell transplantation (HCT). Here we describe the clinical and genetic characteristics of patients with ART-SCID who were diagnosed in Japan from 2003 to 2022.

METHODS

Clinical data of ART-SCID patients who were diagnosed between 2003 and 2022 in Japan were collected from their physicians using a questionnaire.

RESULTS

ART-SCID diagnosis was made in eight patients from seven families with severe infections within 6 months of life. Two patients had missense variants, five patients had large genomic deletions, and one patient was compound heterozygous for a missense variant and large genomic deletion. All eight underwent allogeneic HCT within 4 months after the diagnosis, 7 receiving a conditioning regimen containing alkylating agents, and one patient without conditioning due to uncontrolled infection. Two patients with poor performance status (PS) died of complications 410 days and 32 days post-HCT, respectively. Of the six surviving patients with a median follow-up time of 8.3 (0.5-17.9) years, three patients had growth retardation. The patients with PS of 0-2 showed a tendency for better overall survival than those with PS 3-4.

CONCLUSION

Large deletions were the most common genetic cause of ART-SCID in Japan. To improve HCT outcome, early diagnosis with newborn screening for SCID is urgently needed.

Human thymus in health and disease: Recent advances in diagnosis and biology

The thymus is the crucial tissue where thymocytes develop from hematopoietic precursors that originate from the bone marrow and differentiate to generate a repertoire of mature T cells able to respond to foreign antigens while remaining tolerant to self-antigens. Until recently, most of the knowledge on thymus biology and its cellular and molecular complexity have been obtained through studies in animal models, because of the difficulty to gain access to thymic tissue in humans and the lack of in vitro models able to faithfully recapitulate the thymic microenvironment. This review focuses on recent advances in the understanding of human thymus biology in health and disease obtained through the use of innovative experimental techniques (eg. single cell RNA sequencing, scRNAseq), diagnostic tools (eg. next generation sequencing), and in vitro models of T-cell differentiation (artificial thymic organoids) and thymus development (eg. thymic epithelial cell differentiation from embryonic stem cells or induced pluripotent stem cells).

The modern face of newborn screening

Newborn screening (NBS) has been developed for years to identify newborns with severe but treatable conditions. Taiwan's NBS system, after the initial setup for a total coverage of newborns in 1990s, was later optimized to ensure the timely return of results in infants with abnormal results. Advancements in techniques such as Tandem mass spectrometry enable the screening into a multiplex format and increase the conditions to be screened. Furthermore, advances in therapies, such as enzyme replacement therapy, stem cell transplantation, and gene therapy, significantly expand the needs for newborn screening. Advances in genomics and biomarkers discovery improve the test accuracy with the assistance of second-tier tests, and have the potential to be the first-tier test in the future. Therefore, challenge of NBS now is the knowledge gap, including the evidence of the long-term clinical benefits in large cohorts especially in conditions with new therapies, phenotypic variations and the corresponding management of some screened diseases, and cost-effectiveness of extended NBS programs. A short-term and a long-term follow-up program should be implemented to gather those outcomes better especially in the genomic era. Ethical and psychosocial issues are also potentially encountered frequently. Essential education and better informed consent should be considered fundamental to parallel those new tests into future NBS.