Immune Reconstitution After Gene Therapy Approaches in Patients With X-Linked Severe Combined Immunodeficiency Disease

Preclinical ex vivo IL2RG gene therapy using autologous hematopoietic stem cells as an effective and safe treatment for X-linked severe combined immunodeficiency disease

X-linked severe combined immunodeficiency disease (X-SCID) is a rare inherited disease caused by mutations in the interleukin 2 receptor subunit gamma gene (IL2RG), which encodes the common γ chain protein, a subunit of the receptor for lymphocytes. X-SCID is characterized by profound defects in T-cell, B-cell, and natural killer cell function. Here, we report a Chinese cohort of nine X-SCID patients with six novel IL2RG mutations. Among those, the two adolescent patients with an atypical immunotype were confirmed by further analyzing IL-2-JAK-STAT5 signaling, T cell proliferation, and T cell receptor excision circles (Trecs). Interestingly, Bacillus Calmette-Guérin (BCG) disease occurred commonly in this cohort. Although allogeneic hematopoietic stem-cell transplantation is curative for the disease, it is not available to all patients due to the lack of suitable matched donors. Autologous gene therapy using a self-inactivating lentiviral vector (SIN-LV) technology has provided an alternative therapy for such mono-genetic diseases. Here, we performed the pre-clinical studies to assess our SIN-LV carrying IL2RG on human ED7R cells deficient in IL2RG and CD34+ stem cells derived from the bone marrow of a healthy donor and a patient with X-SCID. This work is done complied with the established "Good Manufacturing Practice" (GMP) used in the clinical trials. In addition, a safety study is performed using the transduced CD34+ cells implanted into the axilla of nude mice in vivo. Overall, our studies have demonstrated the efficiency and safety of SIN-IL2RG-LV, which paves the way for conducting X-SCID gene therapy clinical trials in China in the near future.

Preclinical lentiviral hematopoietic stem cell gene therapy corrects Pompe disease-related muscle and neurological manifestations

Pompe disease, a rare genetic neuromuscular disorder, is caused by a deficiency of acid alpha-glucosidase (GAA), leading to an accumulation of glycogen in lysosomes, and resulting in the progressive development of muscle weakness. The current standard treatment, enzyme replacement therapy (ERT), is not curative and has limitations such as poor penetration into skeletal muscle and both the central and peripheral nervous systems, a risk of immune responses against the recombinant enzyme, and the requirement for high doses and frequent infusions. To overcome these limitations, lentiviral vector-mediated hematopoietic stem and progenitor cell (HSPC) gene therapy has been proposed as a next-generation approach for treating Pompe disease. This study demonstrates the potential of lentiviral HSPC gene therapy to reverse the pathological effects of Pompe disease in a preclinical mouse model. It includes a comprehensive safety assessment via integration site analysis, along with single-cell RNA sequencing analysis of central nervous tissue samples to gain insights into the underlying mechanisms of phenotype correction.

A scalable and cGMP-compatible autologous organotypic cell therapy for Dystrophic Epidermolysis Bullosa

We present Dystrophic Epidermolysis Bullosa Cell Therapy (DEBCT), a scalable platform producing autologous organotypic iPS cell-derived induced skin composite (iSC) grafts for definitive treatment. Clinical-grade manufacturing integrates CRISPR-mediated genetic correction with reprogramming into one step, accelerating derivation of COL7A1-edited iPS cells from patients. Differentiation into epidermal, dermal and melanocyte progenitors is followed by CD49f-enrichment, minimizing maturation heterogeneity. Mouse xenografting of iSCs from four patients with different mutations demonstrates disease modifying activity at 1 month. Next-generation sequencing, biodistribution and tumorigenicity assays establish a favorable safety profile at 1-9 months. Single cell transcriptomics reveals that iSCs are composed of the major skin cell lineages and include prominent holoclone stem cell-like signatures of keratinocytes, and the recently described Gibbin-dependent signature of fibroblasts. The latter correlates with enhanced graftability of iSCs. In conclusion, DEBCT overcomes manufacturing and safety roadblocks and establishes a reproducible, safe, and cGMP-compatible therapeutic approach to heal lesions of DEB patients.

Strategic infection prevention after genetically modified hematopoietic stem cell therapies: recommendations from the International Society for Cell & Gene Therapy Stem Cell Engineering Committee

There is lack of guidance for immune monitoring and infection prevention after administration of ex vivo genetically modified hematopoietic stem cell therapies (GMHSCT). We reviewed current infection prevention practices as reported by providers experienced with GMHSCTs across North America and Europe, and assessed potential immunologic compromise associated with the therapeutic process of GMHSCTs described to date. Based on these assessments, and with consensus from members of the International Society for Cell & Gene Therapy (ISCT) Stem Cell Engineering Committee, we propose risk-adapted recommendations for immune monitoring, infection surveillance and prophylaxis, and revaccination after receipt of GMHSCTs. Disease-specific and GMHSCT-specific considerations should guide decision making for each therapy.

Advances and challenges in gene therapy strategies for pediatric cancer: a comprehensive update

Pediatric cancers represent a tragic but also promising area for gene therapy. Although conventional treatments have improved survival rates, there is still a need for targeted and less toxic interventions. This article critically analyzes recent advances in gene therapy for pediatric malignancies and discusses the challenges that remain. We explore the innovative vectors and delivery systems that have emerged, such as adeno-associated viruses and non-viral platforms, which show promise in addressing the unique pathophysiology of pediatric tumors. Specifically, we examine the field of chimeric antigen receptor (CAR) T-cell therapies and their adaptation for solid tumors, which historically have been more challenging to treat than hematologic malignancies. We also discuss the genetic and epigenetic complexities inherent to pediatric cancers, such as tumor heterogeneity and the dynamic tumor microenvironment, which pose significant hurdles for gene therapy. Ethical considerations specific to pediatric populations, including consent and long-term follow-up, are also analyzed. Additionally, we scrutinize the translation of research from preclinical models that often fail to mimic pediatric cancer biology to the regulatory landscapes that can either support or hinder innovation. In summary, this article provides an up-to-date overview of gene therapy in pediatric oncology, highlighting both the rapid scientific progress and the substantial obstacles that need to be addressed. Through this lens, we propose a roadmap for future research that prioritizes the safety, efficacy, and complex ethical considerations involved in treating pediatric patients. Our ultimate goal is to move from incremental advancements to transformative therapies.

In vivo selection of anti-HIV-1 gene-modified human hematopoietic stem/progenitor cells to enhance engraftment and HIV-1 inhibition

Hematopoietic stem/progenitor cell (HSPC)-based anti-HIV-1 gene therapy holds great promise to eradicate HIV-1 or to provide long-term remission through a continuous supply of anti-HIV-1 gene-modified cells without ongoing antiretroviral therapy. However, achieving sufficient engraftment levels of anti-HIV gene-modified HSPC to provide therapeutic efficacy has been a major limitation. Here, we report an in vivo selection strategy for anti-HIV-1 gene-modified HSPC by introducing 6-thioguanine (6TG) chemoresistance through knocking down hypoxanthine-guanine phosphoribosyl transferase (HPRT) expression using RNA interference (RNAi). We developed a lentiviral vector capable of co-expressing short hairpin RNA (shRNA) against HPRT alongside two anti-HIV-1 genes: shRNA targeting HIV-1 co-receptor CCR5 and a membrane-anchored HIV-1 fusion inhibitor, C46, for efficient in vivo selection of anti-HIV-1 gene-modified human HSPC. 6TG-mediated preconditioning and in vivo selection significantly enhanced engraftment of HPRT-knockdown anti-HIV-1 gene-modified cells (>2-fold, p < 0.0001) in humanized bone marrow/liver/thymus (huBLT) mice. Viral load was significantly reduced (>1 log fold, p < 0.001) in 6TG-treated HIV-1-infected huBLT mice compared to 6TG-untreated mice. We demonstrated that 6TG-mediated preconditioning and in vivo selection considerably improved engraftment of HPRT-knockdown anti-HIV-1 gene-modified HSPC and repopulation of anti-HIV-1 gene-modified hematopoietic cells in huBLT mice, allowing for efficient HIV-1 inhibition.

Partial correction of immunodeficiency by lentiviral vector gene therapy in mouse models carrying Rag1 hypomorphic mutations

Introduction

Recombination activating genes (RAG) 1 and 2 defects are the most frequent form of severe combined immunodeficiency (SCID). Patients with residual RAG activity have a spectrum of clinical manifestations ranging from Omenn syndrome to delayed-onset combined immunodeficiency, often associated with granulomas and/or autoimmunity (CID-G/AI). Lentiviral vector (LV) gene therapy (GT) has been proposed as an alternative treatment to the standard hematopoietic stem cell transplant and a clinical trial for RAG1 SCID patients recently started. However, GT in patients with hypomorphic RAG mutations poses additional risks, because of the residual endogenous RAG1 expression and the general state of immune dysregulation and associated inflammation.

Methods

In this study, we assessed the efficacy of GT in 2 hypomorphic Rag1 murine models (Rag1F971L/F971L and Rag1R972Q/R972Q), exploiting the same LV used in the clinical trial encoding RAG1 under control of the MND promoter.

Results and discussion

Starting 6 weeks after transplant, GT-treated mice showed a decrease in proportion of myeloid cells and a concomitant increase of B, T and total white blood cells. However, counts remained lower than in mice transplanted with WT Lin- cells. At euthanasia, we observed a general redistribution of immune subsets in tissues, with the appearance of mature recirculating B cells in the bone marrow. In the thymus, we demonstrated correction of the block at double negative stage, with a modest improvement in the cortical/medullary ratio. Analysis of antigenspecific IgM and IgG serum levels after in vivo challenge showed an amelioration of antibody responses, suggesting that the partial immune correction could confer a clinical benefit. Notably, no overt signs of autoimmunity were detected, with B-cell activating factor decreasing to normal levels and autoantibodies remaining stable after GT. On the other hand, thymic enlargement was frequently observed, although not due to vector integration and insertional mutagenesis. In conclusion, our work shows that GT could partially alleviate the combined immunodeficiency of hypomorphic RAG1 patients and that extensive efficacy and safety studies with alternative models are required before commencing RAG gene therapy in thesehighly complex patients.

Novel extragenic genomic safe harbors for precise therapeutic T-cell engineering

Cell therapies that rely on engineered immune cells can be enhanced by achieving uniform and controlled transgene expression in order to maximize T-cell function and achieve predictable patient responses. Although they are effective, current genetic engineering strategies that use γ-retroviral, lentiviral, and transposon-based vectors to integrate transgenes, unavoidably produce variegated transgene expression in addition to posing a risk of insertional mutagenesis. In the setting of chimeric antigen receptor (CAR) therapy, inconsistent and random CAR expression may result in tonic signaling, T-cell exhaustion, and variable T-cell persistence. Here, we report and validate an algorithm for the identification of extragenic genomic safe harbors (GSH) that can be efficiently targeted for DNA integration and can support sustained and predictable CAR expression in human peripheral blood T cells. The algorithm is based on 7 criteria established to minimize genotoxicity by directing transgene integration away from functionally important genomic elements, maximize efficient CRISPR/Cas9-mediated targeting, and avert transgene silencing over time. T cells engineered to express a CD19 CAR at GSH6, which meets all 7 criteria, are curative at low cell dose in a mouse model of acute lymphoblastic leukemia, matching the potency of CAR T cells engineered at the TRAC locus and effectively resisting tumor rechallenge 100 days after their infusion. The identification of functional extragenic GSHs thus expands the human genome available for therapeutic precision engineering.

ZAP70 interaction with 13 mRNAs as a potential immunotherapeutic target for endometrial cancer

For advanced, refractory endometrial cancer (EC), it is advisable to find effective immunotherapeutic targets. In the present study, genes affecting the immune status of uterine corpus endometrial carcinoma (UCEC) samples within The Cancer Genome Atlas were explored by weighted correlation network analysis and differential gene expression analysis. The protein function and immune correlation of 14 key genes, including ζ-chain-associated protein kinase 70 (ZAP70), were analyzed. Based on the expression levels of key genes, the patients with UCEC were divided into two groups using consensus clustering, low expression (group 1) and high expression (group 2). Next, the functions of differentially expressed genes (DEGs) between the two groups were identified using Gene Ontology enrichment analysis, Kyoto Encyclopedia of Genes and Genomes analysis and Gene Set Enrichment Analysis. The immune status of the patients in the two groups was evaluated using immune infiltration score and the expression levels of targets of immune checkpoint inhibitors. The role of ZAP70 in the prognosis of patients with UCEC and the differences in ZAP70 expression between EC tissues and healthy intimal tissues were determined by reverse transcription-quantitative PCR and immunohistochemistry. The present study found strong correlations between key genes, including ZAP70, LCK, FOXP3, TIGIT, CTLA4, ICOS, CD5, IL2RG, PDCD1, TNFRSF4, CD27, CCR7, GZMB, CXCL9. From the enrichment analyses, it was found that the functions of these DEGs were related to T cells. Patients in group 2 had stronger immune infiltration and higher immune checkpoints expression compared with those in group 1. ZAP70 was expressed at higher levels in EC tissues compared with in normal tissues, and may act as a protective factor in EC. In conclusion, ZAP70 interaction with 13 mRNAs may affect the immune status of patients with EC and may be a potential target for immunotherapy.

Personalized hematopoietic stem cell transplantation for inborn errors of immunity

Patients with inborn errors of immunity (IEI) have been transplanted for more than 50 years. Many long-term survivors have ongoing medical issues showing the need for further improvements in how hematopoietic stem cell transplantation (HSCT) is performed if patients in the future are to have a normal quality of life. Precise genetic diagnosis enables early treatment before recurrent infection, autoimmunity and organ impairment occur. Newborn screening for severe combined immunodeficiency (SCID) is established in many countries. For newly described disorders the decision to transplant is not straight-forward. Specific biologic therapies are effective for some diseases and can be used as a bridge to HSCT to improve outcome. Developments in reduced toxicity conditioning and methods of T-cell depletion for mismatched donors have made transplant an option for all eligible patients. Further refinements in conditioning plus precise graft composition and additional cellular therapy are emerging as techniques to personalize the approach to HSCT for each patient.

A scalable, GMP-compatible, autologous organotypic cell therapy for Dystrophic Epidermolysis Bullosa

Background

Gene editing in induced pluripotent stem (iPS) cells has been hailed to enable new cell therapies for various monogenetic diseases including dystrophic epidermolysis bullosa (DEB). However, manufacturing, efficacy and safety roadblocks have limited the development of genetically corrected, autologous iPS cell-based therapies.

Methods

We developed Dystrophic Epidermolysis Bullosa Cell Therapy (DEBCT), a new generation GMP-compatible (cGMP), reproducible, and scalable platform to produce autologous clinical-grade iPS cell-derived organotypic induced skin composite (iSC) grafts to treat incurable wounds of patients lacking type VII collagen (C7). DEBCT uses a combined high-efficiency reprogramming and CRISPR-based genetic correction single step to generate genome scar-free, COL7A1 corrected clonal iPS cells from primary patient fibroblasts. Validated iPS cells are converted into epidermal, dermal and melanocyte progenitors with a novel 2D organoid differentiation protocol, followed by CD49f enrichment and expansion to minimize maturation heterogeneity. iSC product characterization by single cell transcriptomics was followed by mouse xenografting for disease correcting activity at 1 month and toxicology analysis at 1-6 months. Culture-acquired mutations, potential CRISPR-off targets, and cancer-driver variants were evaluated by targeted and whole genome sequencing.

Findings

iPS cell-derived iSC grafts were reproducibly generated from four recessive DEB patients with different pathogenic mutations. Organotypic iSC grafts onto immune-compromised mice developed into stable stratified skin with functional C7 restoration. Single cell transcriptomic characterization of iSCs revealed prominent holoclone stem cell signatures in keratinocytes and the recently described Gibbin-dependent signature in dermal fibroblasts. The latter correlated with enhanced graftability. Multiple orthogonal sequencing and subsequent computational approaches identified random and non-oncogenic mutations introduced by the manufacturing process. Toxicology revealed no detectable tumors after 3-6 months in DEBCT-treated mice.

Interpretation

DEBCT successfully overcomes previous roadblocks and represents a robust, scalable, and safe cGMP manufacturing platform for production of a CRISPR-corrected autologous organotypic skin graft to heal DEB patient wounds.

Lentiviral Gene Therapy for Artemis-Deficient SCID

BACKGROUND

The DNA-repair enzyme Artemis is essential for rearrangement of T- and B-cell receptors. Mutations in DCLRE1C, which encodes Artemis, cause Artemis-deficient severe combined immunodeficiency (ART-SCID), which is poorly responsive to allogeneic hematopoietic-cell transplantation.

METHODS

We carried out a phase 1-2 clinical study of the transfusion of autologous CD34+ cells, transfected with a lentiviral vector containing DCLRE1C, in 10 infants with newly diagnosed ART-SCID. We followed them for a median of 31.2 months.

RESULTS

Marrow harvest, busulfan conditioning, and lentiviral-transduced CD34+ cell infusion produced the expected grade 3 or 4 adverse events. All the procedures met prespecified criteria for feasibility at 42 days after infusion. Gene-marked T cells were detected at 6 to 16 weeks after infusion in all the patients. Five of 6 patients who were followed for at least 24 months had T-cell immune reconstitution at a median of 12 months. The diversity of T-cell receptor β chains normalized by 6 to 12 months. Four patients who were followed for at least 24 months had sufficient B-cell numbers, IgM concentration, or IgM isohemagglutinin titers to permit discontinuation of IgG infusions. Three of these 4 patients had normal immunization responses, and the fourth has started immunizations. Vector insertion sites showed no evidence of clonal expansion. One patient who presented with cytomegalovirus infection received a second infusion of gene-corrected cells to achieve T-cell immunity sufficient for viral clearance. Autoimmune hemolytic anemia developed in 4 patients 4 to 11 months after infusion; this condition resolved after reconstitution of T-cell immunity. All 10 patients were healthy at the time of this report.

CONCLUSIONS

Infusion of lentiviral gene-corrected autologous CD34+ cells, preceded by pharmacologically targeted low-exposure busulfan, in infants with newly diagnosed ART-SCID resulted in genetically corrected and functional T and B cells. (Funded by the California Institute for Regenerative Medicine and the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT03538899.).

Challenges in Gene Therapy for Somatic Reverted Mosaicism in X-Linked Combined Immunodeficiency by CRISPR/Cas9 and Prime Editing

X-linked severe combined immunodeficiency (X-SCID) is a primary immunodeficiency that is caused by mutations in the interleukin-2 receptor gamma (IL2RG) gene. Some patients present atypical X-SCID with mild clinical symptoms due to somatic revertant mosaicism. CRISPR/Cas9 and prime editing are two advanced genome editing tools that paved the way for treating immune deficiency diseases. Prime editing overcomes the limitations of the CRISPR/Cas9 system, as it does not need to induce double-strand breaks (DSBs) or exogenous donor DNA templates to modify the genome. Here, we applied CRISPR/Cas9 with single-stranded oligodeoxynucleotides (ssODNs) and prime editing methods to generate an in vitro model of the disease in K-562 cells and healthy donors' T cells for the c. 458T>C point mutation in the IL2RG gene, which also resulted in a useful way to optimize the gene correction approach for subsequent experiments in patients' cells. Both methods proved to be successful and were able to induce the mutation of up to 31% of treated K-562 cells and 26% of treated T cells. We also applied similar strategies to correct the IL2RG c. 458T>C mutation in patient T cells that carry the mutation with revertant somatic mosaicism. However, both methods failed to increase the frequency of the wild-type sequence in the mosaic T cells of patients due to limited in vitro proliferation of mutant cells and the presence of somatic reversion. To the best of our knowledge, this is the first attempt to treat mosaic cells from atypical X-SCID patients employing CRISPR/Cas9 and prime editing. We showed that prime editing can be applied to the formation of specific-point IL2RG mutations without inducing nonspecific on-target modifications. We hypothesize that the feasibility of the nucleotide substitution of the IL2RG gene using gene therapy, especially prime editing, could provide an alternative strategy to treat X-SCID patients without revertant mutations, and further technological improvements need to be developed to correct somatic mosaicism mutations.

Precision medicine: The use of tailored therapy in primary immunodeficiencies

Primary immunodeficiencies (PID) are rare, complex diseases that can be characterised by a spectrum of phenotypes, from increased susceptibility to infections to autoimmunity, allergy, auto-inflammatory diseases and predisposition to malignancy. With the introduction of genetic testing in these patients and wider use of next-Generation sequencing techniques, a higher number of pathogenic genetic variants and conditions have been identified, allowing the development of new, targeted treatments in PID. The concept of precision medicine, that aims to tailor the medical interventions to each patient, allows to perform more precise diagnosis and more importantly the use of treatments directed to a specific defect, with the objective to cure or achieve long-term remission, minimising the number and type of side effects. This approach takes particular importance in PID, considering the nature of causative defects, disease severity, short- and long-term complications of disease but also of the available treatments, with impact in life-expectancy and quality of life. In this review we revisit how this approach can or is already being implemented in PID and provide a summary of the most relevant treatments applied to specific diseases.

Transplantation of human cells into Interleukin-2 receptor gamma gene knockout pigs under several conditions

INTRODUCTION

Previously, we performed gene knockout (KO) of interleukin-2 receptor gamma (IL2RG) in porcine fetal fibroblasts using zinc finger nuclease-encoding mRNAs, subsequently generating IL2RG KO pigs using these cells through somatic cell nuclear transfer. The IL2RG KO pigs lacked a thymus and were deficient in T lymphocytes and natural killer cells, similar to human X-linked severe combined immunodeficiency (SCID) patients. The present study aimed to evaluate whether pigs can support the growth of xenografted human cells and have the potential to be an effective animal model.

METHODS

The IL2RG XKOY pigs used in this study were obtained by mating IL2RG XKOX females with wild-type boars. This permitted the routine production of IL2RG KO pigs via natural breeding without complicated somatic cell cloning procedures; therefore, a sufficient number of pigs could be prepared. We transplanted human HeLa S3 cells expressing the tandem dimer tomato into the ears and pancreas of IL2RG KO pigs. Additionally, a newly developed method for the aseptic rearing of SCID pigs was used in case of necessity.

RESULTS

Tumors from the transplanted cells quickly developed in all pigs and were verified by histology and immunohistochemistry. We also transplanted these cells into the pancreas of designated pathogen-free pigs housed in novel biocontainment facilities, and large tumors were confirmed.

CONCLUSIONS

IL2RG KO pigs have the potential to become useful animal models in a variety of translational biology fields.

A great disturbance in the force: IL-2 receptor defects disrupt immune homeostasis

PURPOSE OF REVIEW

The current review highlights how inborn errors of immunity (IEI) due to IL-2 receptor (IL-2R) subunit defects may result in children presenting with a wide variety of infectious and inflammatory presentations beyond typical X-linked severe combined immune deficiency (X-SCID) associated with IL-2Rγ.

RECENT FINDINGS

Newborn screening has made diagnosis of typical SCID presenting with severe infections less common. Instead, infants are typically diagnosed in the first days of life when they appear healthy. Although earlier diagnosis has improved clinical outcomes for X-SCID, atypical SCID or other IEI not detected on newborn screening may present with more limited infectious presentations and/or profound immune dysregulation. Early management to prevent/control infections and reduce inflammatory complications is important for optimal outcomes of definitive therapies. Hematopoietic stem cell transplant (HSCT) is curative for IL-2Rα, IL-2Rβ, and IL-2Rγ defects, but gene therapy may yield comparable results for X-SCID.

SUMMARY

Defects in IL-2R subunits present with infectious and inflammatory phenotypes that should raise clinician's concern for IEI. Immunophenotyping may support the suspicion for diagnosis, but ultimately genetic studies will confirm the diagnosis and enable family counseling. Management of infectious and inflammatory complications will determine the success of gene therapy or HSCT.

Case Report: Preimplantation Genetic Testing for X-Linked Severe Combined Immune Deficiency Caused by IL2RG Gene Variant

Preimplantation genetic testing (PGT) has been increasingly used to prevent rare inherited diseases. In this study, we report a case where PGT was used to prevent the transmission of disease-caused variant in a SCID-X1 (OMIM:300400) family. SCID-X1 is an X-linked recessive inherited disease whose major clinical manifestation of immune deficiency is the significant reduction in the number of T-cells and natural killer cells. This family gave birth to a boy who was a hemizygous proband whose IL2RG gene was mutated (c.315T > A, p(Tyr105*), NM_000206.3, CM962677). In this case, Sanger sequencing for mutated allele and linkage analysis based on single-nucleotide polymorphism (SNP) haplotype via next-generation sequencing were performed simultaneously. After PGT for monogenic disorder, we detected the aneuploidy and copy number variation (CNV) for normal and female carrier embryos. Four embryos (E02, E09, E10, and E11) were confirmed without CNVs and inherited variants at the IL2RG gene. Embryo E02 (ranking 4BB) has been transferred after considering the embryo growth rate, morphology, and PGT results. Prenatal genetic diagnosis was used to detect amniotic fluid cells, showing that this fetus did not carry the variant of the IL2RG gene (c.315T > A). Ultimately, a healthy girl who had not carried disease-causing variants of SCID-X1 confirmed by prenatal diagnosis was born, further verifying our successful application of PGT in preventing mutated allele transmission for this SCID family.

Advanced Therapy Medicinal Products' Translation in Europe: A Developers' Perspective

Advanced Therapy Medicinal Products (ATMPs) comprising cell, gene, and tissue-engineered therapies have demonstrated enormous therapeutic benefits. However, their development is complex to be managed efficiently within currently existing regulatory frameworks. Legislation and regulation requirements for ATMPs must strike a balance between the patient safety while promoting innovations to optimize exploitation of these novel therapeutics. This paradox highlights the importance of on-going dynamic dialogue between all stakeholders and regulatory science to facilitate the development of pragmatic ATMP regulatory guidelines.

Pediatric immune deficiencies: current treatment approaches

PURPOSE OF REVIEW

To summarize the currently available definitive therapies for patients with inborn errors of immunity (IEIs) with a strong focus on recent advances in allogeneic hematopoietic cell transplantation (HCT) and gene therapy, including the use of alternative donors, graft manipulation techniques, less toxic approaches for pretransplant conditioning and gene transfer using autologous hematopoietic stem cells.

RECENT FINDINGS

In the absence of a matched sibling or a matched related donor, therapeutic alternatives for patients with IEIs include alternative donor transplantation or autologous gene therapy, which is only available for selected IEIs. In recent years, several groups have published their experience with haploidentical hematopoietic cell transplantation (HHCT) using different T-cell depletion strategies. Overall survival and event free survival results, although variable among centers, are encouraging. Preliminary results from autologous gene therapy trials with safer vectors and low-dose busulfan conditioning have shown reproducible and successful results. Both strategies have become valid therapeutic options for patients with IEIs. A new promising and less toxic conditioning regimen strategy is also discussed.

SUMMARY

Definitive therapies for IEIs with HCT and gene therapy are in stage of evolution, not only to refine their efficacy and safety but also their reach to a larger number of patients.

Development and clinical translation of ex vivo gene therapy

Retroviral gene therapy has emerged as a promising therapeutic modality for multiple inherited and acquired human diseases. The capability of delivering curative treatment or mediating therapeutic benefits for a long-term period following a single application fundamentally distinguishes this medical intervention from traditional medicine and various lentiviral/γ-retroviral vector-mediated gene therapy products have been approved for clinical use. Continued advances in retroviral vector engineering, genomic editing, synthetic biology and immunology will broaden the medical applications of gene therapy and improve the efficacy and safety of the treatments based on genetic correction and alteration. This review will summarize the advent and clinical translation of ex vivo gene therapy, with the focus on the milestones during the exploitation of genetically engineered hematopoietic stem cells (HSCs) tackling a variety of pathological conditions which led to marketing approval. Finally, current statue and future prospects of gene editing as an alternative therapeutic approach are also discussed.

DAP10 Predicted the Outcome of Pediatric B-Cell Acute Lymphoblastic Leukemia and Was Associated with the T-Cell Exhaustion

B-cell acute lymphoblastic leukemia is the most common malignant tumor in children. About 10–15% of patients will relapse with a 5-year OS of 57.5% for the past 20 years. As tumor microenvironment plays an important role in the disease process, many types of immunotherapy are approached. New immunotherapies including CAR-T cells have been developed for refractory B-ALL treatment. However, CAR-T treatment faces several problems, including loss of the target antigen and in vivo T-cell persistence. Here, we analyzed the tumor microenvironment of pediatric B-ALL patients in TARGET database. Using Cox analysis and PPI network, we finally sorted out the DAP10 gene. We found that DAP10 was hardly expressed in leukemic B cells. DAP10 was downregulated in B-ALL compared with normal individuals, and low expression level of DAP10 predicted poor survival. Furthermore, we found the tumor microenvironment was different in DAP10 high and low expression children. The CD8+ T cells might be hard to activate and more likely to suffer from exhaustion in DAP10 lowly expressed children. In conclusion, our results showed that DAP10 was a well biomarker to indicate the prognosis and tumor microenvironment in pediatric B-ALL. The treatment strategy of immunotherapy for the leukemic children with DAP10 lowly expressed should be adjusted if needed.

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.

Case Report: Interleukin-2 Receptor Common Gamma Chain Defect Presented as a Hyper-IgE Syndrome

X-linked severe combined immunodeficiency (X-SCID) is caused by mutations of IL2RG, the gene encoding the interleukin common gamma chain (IL-2Rγ or γc) of cytokine receptors for interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Hypomorphic mutations of IL2RG may cause combined immunodeficiencies with atypical clinical and immunological presentations. Here, we report a clinical, immunological, and functional characterization of a missense mutation in exon 1 (c.115G>A; p. Asp39Asn) of IL2RG in a 7-year-old boy. The patient suffered from recurrent sinopulmonary infections and refractory eczema. His total lymphocyte counts have remained normal despite skewed T cell subsets, with a pronounced serum IgE elevation. Surface expression of IL-2Rγ was reduced on his lymphocytes. Signal transducer and activator of transcription (STAT) phosphorylation in response to IL-2, IL-4, and IL-7 showed a partially preserved receptor function. T-cell proliferation in response to mitogens and anti-CD3/anti-CD28 monoclonal antibodies was significantly reduced. Further analysis revealed a decreased percentage of CD4⁺ T cells capable of secreting IFN-γ, but not IL-4 or IL-17. Studies on the functional consequences of IL-2Rγ variants are important to get more insight into the pathogenesis of atypical phenotypes which may lay the ground for novel therapeutic strategies.