Recombinase-activating gene (RAG)-deficient SCID patients lack B and T lymphocytes due to the inability to rearrange immunoglobulin and T cell receptor genes. The two RAG genes act as a required dimer to initiate gene recombination. Gene therapy is a valid treatment alternative for RAG-SCID patients who lack a suitable bone marrow donor, but developing such therapy for RAG1/2 has proven challenging. Using a clinically approved lentiviral vector with a codon-optimized RAG1 gene, we report here preclinical studies using CD34+ cells from four RAG1-SCID patients. We used in vitro T cell developmental assays and in vivo assays in xenografted NSG mice. The RAG1-SCID patient CD34+ cells transduced with the RAG1 vector and transplanted into NSG mice led to restored human B and T cell development. Together with favorable safety data on integration sites, these results substantiate an ongoing phase I/II clinical trial for RAG1-SCID.

This article presents the report of the session on \"Newborn Screening for Primary Immunodeficiencies-Now What?\" organised during the International Primary Immunodeficiency Congress (IPIC) held in November 2023. This clinical conference was organised by the International Patient Organisation for Primary Immunodeficiencies (IPOPI), the global patient organisation advocating for primary immunodeficiencies (PIDs) in patients. The session aimed at exploring the advances in newborn screening (NBS) for severe combined immunodeficiency, starting with the common practice and inserting the discussion into the wider perspective of genomics whilst taking into consideration the ethical aspects of screening as well as incorporating families and the public into the discussions, so as to ensure that NBS for treatable rare disorders continues to be one of the major public health advances of the 20th century.

OBJECTIVE: 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.
CONCLUSIONS: 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.

Purine nucleoside phosphorylase deficient severe combined immunodeficiency (PNP SCID) is one of the rare autosomal recessive primary immunodeficiency disease, and the data on epidemiology and outcome are limited. We report the successful management of a child with PNP SCID and present a systematic literature review of published case reports, case series, and cohort studies on PNP SCID listed in PubMed, Web of Science, and Scopus from 1975 until March 2022. Forty-one articles were included from the 2432 articles retrieved and included 100 PNP SCID patients worldwide. Most patients presented with recurrent infections, hypogammaglobulinaemia, autoimmune manifestations, and neurological deficits. There were six reported cases of associated malignancies, mainly lymphomas. Twenty-two patients had undergone allogeneic hematopoietic stem cell transplantation with full donor chimerism seen mainly in those receiving matched sibling donors and/or conditioning chemotherapy before the transplant. This research provides a contemporary, comprehensive overview on clinical manifestations, epidemiology, genotype mutations, and transplant outcome of PNP SCID. These data highlight the importance of screening for PNP SCID in cases presented with recurrent infections, hypogammaglobulinaemia, and neurological deficits.

The BCG vaccine, like all other vaccines, is associated with adverse events following immunization (AEFI). Reducing the incidence of AEFI is crucial in reposing confidence in BCG vaccination and reducing hesitancy associated with the vaccine. This requires safety precautions before and during vaccinations, as well as reporting AEFIs after vaccination. This study assessed the adherence of health-care professionals to pre-vaccination precautions and adverse events following immunization (AEFI) reporting practices during BCG vaccination in four hospitals in Ghana. It is hoped that the findings of the study will serve as a baseline to identify gaps for further studies to generate a stronger evidence for policy formulation aimed at improving BCG vaccine safety in Ghana and other tuberculosis endemic countries. A cross-sectional study design was employed, and Statistical Package for Social Sciences, IBM® SPSS version 25 (SPSS Inc. USA) software was used for analysis. Chi-square and binary logistic regression tests were used to test the association between categorical variables and predictors of adherence to pre-BCG vaccination precautions, respectively, and a p-value of <.05 was considered statistically significant. The AEFIs commonly reported by mothers included abscess, injection site pain, injection site redness, fever, rash, muscle weakness, diarrhea, vomiting, coughing and rhinitis. Ninety-three participants (73.2%) were adherent to pre-BCG vaccination precautions. Ninety-two participants (72.4%) informed mothers to report all AEFIs encountered. Adherence to pre-BCG vaccination precautions and AEFI reporting were generally good; however, there is still room for improvement.

Increased susceptibility to develop severe forms of Epstein-Barr virus (EBV) infection in early age is a significant hallmark of an underlying primary immunodeficiency (PID). Here, we present immunologic and genetic evaluations of a 3-year-old child who was born to first-cousins parents and presented with recurrent infections, failure to thrive, and severe EBV-related infection and proliferation. A diagnosis of diffuse large B cell lymphoma was made and the immunological workup was suggestive of T cell immunodeficiency. Unfortunately, the patient succumbed to EBV-related lymphoma. Whole-exome sequencing revealed a novel homozygous mutation, c.991del.C; p. Q331Sfs*6 in the SLP76 gene. The SLP76 protein, a TCR signaling molecule, was recently linked to a human disease of the immune system. In order to examine the effect of this new SLP76 mutation on T cell signaling, a SLP76-deficient Jurkat-derived T cell line was transduced either with wild-type (WT), or with the specific SLP76 mutant, or with a mock vector. Downstream TCR signaling events, including ERK1/2 phosphorylation, CD69 expression, and Ca2 + mobilization, were reduced in cells harboring the reported mutation, linking this novel mutation to the expected immunological outcome. SLP76 deficiency should be added to the growing list of monogenetic diseases that predispose affected individuals to acquire severe and uncontrolled EBV infections and to develop substantial complications. This case further links mutations in the SLP76 gene to a significant human immunodeficiency and extends its clinical phenotype.

Newborn screening (NBS) for severe combined immunodeficiency (SCID) can identify infants with non-SCID T cell lymphopenia (TCL). The purpose of this study was to characterize the natural history and genetic findings of infants with non-SCID TCL identified on NBS. We analyzed data from 80 infants with non-SCID TCL in the mid-Atlantic region between 2012 and 2019. 66 patients underwent genetic testing and 41 (51%) had identified genetic variant(s). The most common genetic variants were thymic defects (33%), defects with unknown mechanisms (12%) and bone marrow production defects (5%). The genetic cohort had significantly lower median initial CD3+, CD4+, CD8+ and CD4/CD45RA+ T cell counts compared to the non-genetic cohort. Thirty-six (45%) had either viral, bacterial, or fungal infection; only one patient had an opportunistic infection (vaccine strain VZV infection). Twenty-six (31%) of patients had resolution of TCL during the study period.

Severe combined immunodeficiency (SCID) comprises rare inherited disorders of immunity that require definitive treatment through hematopoietic cell transplantation (HCT) or gene therapy for survival. Despite successes of allogeneic HCT, many SCID patients experience incomplete immune reconstitution, persistent T-cell lymphopenia, and poor long-term outcomes.
We hypothesized that CD4+ T-cell lymphopenia could be associated with a state of T-cell exhaustion in previously transplanted SCID patients.
We analyzed markers of exhaustion in blood samples from 61 SCID patients at a median of 10.4 years after HCT.
Compared to post-HCT SCID patients with normal CD4+ T-cell counts, those with poor T-cell reconstitution showed lower frequency of naive CD45RA+/CCR7+ T cells, recent thymic emigrants, and TCR excision circles. They also had a restricted TCR repertoire, increased expression of inhibitory receptors (PD-1, 2B4, CD160, BTLA, CTLA-4), and increased activation markers (HLA-DR, perforin) on their total and naive CD8+ T cells, suggesting T-cell exhaustion and aberrant activation, respectively. The exhaustion score of CD8+ T cells was inversely correlated with CD4+ T-cell count, recent thymic emigrants, TCR excision circles, and TCR diversity. Exhaustion scores were higher among recipients of unconditioned HCT, especially when further in time from HCT. Patients with fewer CD4+ T cells showed a transcriptional signature of exhaustion.
Recipients of unconditioned HCT for SCID may develop late post-HCT T-cell exhaustion as a result of diminished production of T-lineage cells. Elevated expression of inhibitory receptors on their T cells may be a biomarker of poor long-term T-cell reconstitution.

UNASSIGNED: During the process of generating diverse T and B cell receptor (TCR and BCR, respectively) repertoires, double-strand DNA breaks are produced. Subsequently, these breaks are corrected by a complex system led by the non-homologous end-joining (NHEJ). Pathogenic variants in genes involved in this process, such as the NHEJ1 gene, cause severe combined immunodeficiency syndrome (SCID) along with neurodevelopmental disease and sensitivity to ionizing radiation.
UNASSIGNED: To provide new clinical and immunological insights on NHEJ1 deficiency arising from a newly diagnosed patient with severe immunodeficiency.
UNASSIGNED: A male infant, born to consanguineous parents, suspected of having primary immunodeficiency underwent immunological and genetic workup. This included a thorough assessment of T cell phenotyping and lymphocyte activation by mitogen stimulation tests, whole-exome sequencing (WES), TCR repertoire Vβ repertoire via flow cytometry analysis, and TCR and BCR repertoire analysis via next-generation sequencing (NGS).
UNASSIGNED: Clinical findings included microcephaly, recurrent pneumonia, and failure to thrive. An immune workup revealed lymphopenia, reduced T cell function, and hypogammaglobulinemia. Skewed TCR Vβ repertoire, TCR gamma (TRG) repertoire, and BCR repertoire were determined in the patient. Genetic analysis identified a novel homozygous missense pathogenic variant in XLF/Cernunnos: c.A580Ins.T; p.M194fs. The patient underwent a successful hematopoietic stem cell transplantation (HSCT).
UNASSIGNED: A novel NHEJ1 pathogenic variant is reported in a patient who presented with SCID phenotype that displayed clonally expanded T and B cells. An adjusted HSCT was safe to ensure full T cell immune reconstitution.

Newborn screening for severe combined immunodeficiency (SCID) has not only accelerated diagnosis and improved treatment for affected infants, but also led to identification of novel genes required for human T cell development. A male proband had SCID newborn screening showing very low T cell receptor excision circles (TRECs), a biomarker for thymic output of nascent T cells. He had persistent profound T lymphopenia, but normal numbers of B and natural killer (NK) cells. Despite an allogeneic hematopoietic stem cell transplant from his brother, he failed to develop normal T cells. Targeted resequencing excluded known SCID genes; however, whole exome sequencing (WES) of the proband and parents revealed a maternally inherited X-linked missense mutation in MED14 (MED14V763A), a component of the mediator complex. Morpholino (MO)-mediated loss of MED14 function attenuated T cell development in zebrafish. Moreover, this arrest was rescued by ectopic expression of cDNA encoding the wild type human MED14 ortholog, but not by MED14V763A , suggesting that the variant impaired MED14 function. Modeling of the equivalent mutation in mouse (Med14V769A) did not disrupt T cell development at baseline. However, repopulation of peripheral T cells upon competitive bone marrow transplantation was compromised, consistent with the incomplete T cell reconstitution experienced by the proband upon transplantation with bone marrow from his healthy male sibling, who was found to have the same MED14V763A variant. Suspecting that the variable phenotypic expression between the siblings was influenced by further mutation(s), we sought to identify genetic variants present only in the affected proband. Indeed, WES revealed a mutation in the L1 cell adhesion molecule (L1CAMQ498H); however, introducing that mutation in vivo in mice did not disrupt T cell development. Consequently, immunodeficiency in the proband may depend upon additional, unidentified gene variants.