Hematopoietic Stem Cell Transplantation for Severe Combined Immunodeficiency Diseases

Monogenic inborn errors of immunity in autoimmune disorders

To estimate the prevalence of monogenic inborn errors of immunity in patients with autoimmune diseases (AID), the study included 56 subjects (male:female ratio: 1.07) with mean age of onset of autoimmunity 7 years (4 months-46 years). 21/56 had polyautoimmunity. 5/56 patients met the JMF criteria for PID. The different AID referred were hematological (42%) > gastrointestinal (GI) (16%) > skin (14%) > endocrine (10%) > rheumatological (8%) > renal (6%) > neurological (2%). 36/56 reported recurrent infections. 27/56 were on polyimmunotherapy. 18/52 (35%) had CD19 lymphopenia, 24/52 (46%) had CD4 lymphopenia, 11/52 (21%) had CD8 lymphopenia, and 14/48 (29%) had NK lymphopenia. 21/50 (42%) had hypogammaglobinemia; 3 of whom were given rituximab. 28/56 were found to have pathogenic variants among PIRD genes. These 28 patients had 42 AID among which hematological was most common (50%) > GI (14%) = skin (14%)> endocrine (9%) > rheumatological (7%) > renal and neurological (2%). Hematological AID was the most common AID (75%) in children with PIRD. Positive predictive value (PPV) of abnormal immunological tests was 50% and sensitivity of 70%. JMF criteria had specificity of 100% in identifying PIRD and sensitivity of 17%. Polyautoimmunity had a PPV of 35% and sensitivity of 40%. 11/28 of these children were offered transplant. 8/28 were started on sirolimus, 2/28 on abatacept, and 3/28 on baricitinib/ruxolitinib after diagnosis. In conclusion, 50% of children with AID have underlying PIRD. LRBA deficiency and STAT1 GOF were the most common PIRD. Age at presentation, number of autoimmunity, routine immunological tests, and JMF criteria are not predictive of underlying PIRD. Early diagnosis with exome sequencing alters the prognosis and opens new therapeutic avenue.

Inborn errors of immunity associated with defects of thymic development

The main function of the thymus is to support the establishment of a wide repertoire of T lymphocytes capable of eliminating foreign pathogens, yet tolerant to self-antigens. Thymocyte development in the thymus is dependent on the interaction with thymic stromal cells, a complex mixture of cells comprising thymic epithelial cells (TEC), mesenchymal and endothelial cells. The exchange of signals between stromal cells and thymocytes is referred to as "thymic cross-talk". Genetic defects affecting either side of this interaction result in defects in thymic development that ultimately lead to a decreased output of T lymphocytes to the periphery. In the present review, we aim at providing a summary of inborn errors of immunity (IEI) characterized by T-cell lymphopenia due to defects of the thymic stroma, or to hematopoietic-intrinsic defects of T-cell development, with a special focus on recently discovered disorders. Additionally, we review the novel diagnostic tools developed to discover and study new genetic causes of IEI due to defects in thymic development. Finally, we discuss therapeutic approaches to correct thymic defects that are currently available, in addition to potential novel therapies that could be applied in the future.

Bayesian Modeling Immune Reconstitution Apply to CD34+ Selected Stem Cell Transplantation for Severe Combined Immunodeficiency

Severe combined immunodeficiencies (SCIDs) correspond to the most severe form of primary immunodeficiency. Allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy are curative treatments, depending on the donor's availability and molecular diagnostics. A partially human leukocyte antigen (HLA)-compatible donor used has been developed for this specific HSCT indication in the absence of a matched donor. However, the CD34+ selected process induces prolonged post-transplant T-cell immunodeficiency. The aim here was to investigate a modeling approach to predict the time course and the extent of CD4+ T-cell immune reconstitution after CD34+ selected transplantation. We performed a Bayesian approach based on the age-related changes in thymic output and the cell proliferation/loss model. For that purpose, we defined specific individual covariates from the data collected from 10 years of clinical practice and then evaluated the model's predicted performances and accuracy. We have shown that this Bayesian modeling approach predicted the time course and extent of CD4+ T-cell immune reconstitution after SCID transplantation.

NK Cells from RAG- or DCLRE1C-Deficient Patients Inhibit HCMV

The recombination-activating genes (RAGs) and the DNA cross-link repair 1C gene (DCLRE1C) encode the enzymes RAG1, RAG2 and Artemis. They are critical components of the V(D)J recombination machinery. V(D)J recombination is well known as a prerequisite for the development and antigen diversity of T and B cells. New findings suggested that RAG deficiency impacts the cellular fitness and function of murine NK cells. It is not known whether NK cells from severe combined immunodeficiency (SCID) patients with defective RAGs or DCLRE1C (RAGs⁻/DCLRE1C⁻-NK) are active against virus infections. Here, we evaluated the anti-HCMV activity of RAGs⁻/DCLRE1C⁻-NK cells. NK cells from six SCID patients were functional in inhibiting HCMV transmission between cells in vitro. We also investigated the expansion of HCMV-induced NK cell subset in the RAG- or DCLRE1C-deficient patients. A dynamic expansion of NKG2C⁺ NK cells in one RAG-2-deficient patient was observed post HCMV acute infection. Our study firstly reveals the antiviral activity of human RAGs⁻/ DCLRE1C⁻-NK cells.

Lentiviral Gene Therapy Combined with Low-Dose Busulfan in Infants with SCID-X1

BACKGROUND

Allogeneic hematopoietic stem-cell transplantation for X-linked severe combined immunodeficiency (SCID-X1) often fails to reconstitute immunity associated with T cells, B cells, and natural killer (NK) cells when matched sibling donors are unavailable unless high-dose chemotherapy is given. In previous studies, autologous gene therapy with γ-retroviral vectors failed to reconstitute B-cell and NK-cell immunity and was complicated by vector-related leukemia.

METHODS

We performed a dual-center, phase 1-2 safety and efficacy study of a lentiviral vector to transfer IL2RG complementary DNA to bone marrow stem cells after low-exposure, targeted busulfan conditioning in eight infants with newly diagnosed SCID-X1.

RESULTS

Eight infants with SCID-X1 were followed for a median of 16.4 months. Bone marrow harvest, busulfan conditioning, and cell infusion had no unexpected side effects. In seven infants, the numbers of CD3+, CD4+, and naive CD4+ T cells and NK cells normalized by 3 to 4 months after infusion and were accompanied by vector marking in T cells, B cells, NK cells, myeloid cells, and bone marrow progenitors. The eighth infant had an insufficient T-cell count initially, but T cells developed in this infant after a boost of gene-corrected cells without busulfan conditioning. Previous infections cleared in all infants, and all continued to grow normally. IgM levels normalized in seven of the eight infants, of whom four discontinued intravenous immune globulin supplementation; three of these four infants had a response to vaccines. Vector insertion-site analysis was performed in seven infants and showed polyclonal patterns without clonal dominance in all seven.

CONCLUSIONS

Lentiviral vector gene therapy combined with low-exposure, targeted busulfan conditioning in infants with newly diagnosed SCID-X1 had low-grade acute toxic effects and resulted in multilineage engraftment of transduced cells, reconstitution of functional T cells and B cells, and normalization of NK-cell counts during a median follow-up of 16 months. (Funded by the American Lebanese Syrian Associated Charities and others; LVXSCID-ND ClinicalTrials.gov number, NCT01512888.).

Genome editing: A perspective on the application of CRISPR/Cas9 to study human diseases (Review)

Genome editing reemerged in 2012 with the development of CRISPR/Cas9 technology, which is a genetic manipulation tool derived from the defense system of certain bacteria against viruses and plasmids. This method is easy to apply and has been used in a wide variety of experimental models, including cell lines, laboratory animals, plants, and even in human clinical trials. The CRISPR/Cas9 system consists of directing the Cas9 nuclease to create a site-directed double-strand DNA break using a small RNA molecule as a guide. A process that allows a permanent modification of the genomic target sequence can repair the damage caused to DNA. In the present study, the basic principles of the CRISPR/Cas9 system are reviewed, as well as the strategies and modifications of the enzyme Cas9 to eliminate the off-target cuts, and the different applications of CRISPR/Cas9 as a system for visualization and gene expression activation or suppression. In addition, the review emphasizes on the potential application of this system in the treatment of different diseases, such as pulmonary, gastrointestinal, hematologic, immune system, viral, autoimmune and inflammatory diseases, and cancer.

Foxp3+ regulatory T cells maintain the bone marrow microenvironment for B cell lymphopoiesis

Foxp3⁺ regulatory T cells (Treg cells) modulate the immune system and maintain self-tolerance, but whether they affect haematopoiesis or haematopoietic stem cell (HSC)-mediated reconstitution after transplantation is unclear. Here we show that B-cell lymphopoiesis is impaired in Treg-depleted mice, yet this reduced B-cell lymphopoiesis is rescued by adoptive transfer of affected HSCs or bone marrow cells into Treg-competent recipients. B-cell reconstitution is abrogated in both syngeneic and allogeneic transplantation using Treg-depleted mice as recipients. Treg cells can control physiological IL-7 production that is indispensable for normal B-cell lymphopoiesis and is mainly sustained by a subpopulation of ICAM1⁺ perivascular stromal cells. Our study demonstrates that Treg cells are important for B-cell differentiation from HSCs by maintaining immunological homoeostasis in the bone marrow microenvironment, both in physiological conditions and after bone marrow transplantation.

Treg cells suppress peripheral immune responses, but their function in haematopoiesis is unclear. Here the authors show they modulate the bone marrow microenvironment to sustain haematopoietic stem cell-driven generation of mature B cells.

Primary immunodeficiencies in the Netherlands: national patient data demonstrate the increased risk of malignancy

PURPOSE

To analyze the data of the national registry of all Dutch primary immune deficiency (PID) patients, according to the European Society for Immunodeficiencies (ESID) definitions.

RESULTS

In the Netherlands, 745 patients had been registered between 2009 and 2012. An overall prevalence of 4.0 per 100,000 inhabitants was calculated. The most prevalent PID was 'predominantly antibody disorder (PAD)' (60.4%). In total, 118 transplantations were reported, mostly hematopoietic stem cell transplantations (HSCT). Almost 10% of the PID patients suffered from a malignancy, in particular 'lymphoma' and 'skin cancer'. Compared to the general Dutch population, the relative risk of developing any malignancy was 2.3-fold increased, with a >10-fold increase for some solid tumors (thymus, endocrine organs) and hematological disease (lymphoma, leukemia), varying per disease category.

CONCLUSIONS

The incidence rate and characteristics of PID in the Netherlands are similar to those in other European countries. Compared to the general population, PID patients carry an increased risk to develop a malignancy.

Therapeutic management of primary immunodeficiency in older patients

Primary immunodeficiency disease (PID) has traditionally been viewed as a group of illnesses seen in the paediatric age group. New advances in diagnosis and treatment have led to an increase in the number of elderly PID patients. However, there is lack of research evidence on which to base clinical management in this group of patients. Management decisions often have to be based therefore on extrapolations from other patient cohorts or from younger patients. Data from the European Society for Immunodeficiencies demonstrates that the vast majority of elderly patients suffer from predominantly antibody deficiency syndromes. We review the management of PID disease in the elderly, with a focus on antibody deficiency disease.

Patients with primary immunodeficiencies in pediatric intensive care unit: outcomes and mortality-related risk factors

PURPOSES

The aims of this study were to review the frequency, characteristics, and the clinical course of primary immunodeficiency (PID) patients admitted to pediatric intensive care unit (PICU) and attempt to identify factors related with mortality that might predict a poor outcome.

METHODS

We performed a retrospective review of children with PID aged 1 month to 18 years and admitted to PICU from January 2002 to January 2012 in our tertiary teaching children's hospital.

RESULTS

There were a total of 51 patients accounting for 71 admissions to the PICU. The most common diagnosis was severe combined immunodeficiency. Respiratory problems were the leading cause for admission. A total of 20 patients received hematopoietic stem cell transplantation. Immune reconstitution was achieved in 9 (45 %) patients and eight of them did survive. In all 56 % of all admission episodes resulted in survival. Risk factors for mortality included requirement of mechanical ventilation (P < .001), number of organ system failure (P = .013), need for renal replacement therapy (P < .001), use of inotropes (P < .001), higher Pediatric Logistic Organ Dysfunction (PELOD) score (P = .005), and length of PICU stay (P < .001).

CONCLUSIONS

This is the first study regarding the outcome and mortality-related risk factors for PID patients requiring PICU admission. We suggest that PICU management is as important as early diagnosis and treatment for these patients. Prediction of those at risk for poorer outcome might be beneficial for accurate intensive care management and survival.

Chimerism in children with primary immunodeficiencies is influenced by number of activating killer cell immunoglobulin-like receptor genes in the donor and/or killer cell immunoglobulin-like receptor ligand mismatch

BACKGROUND

Stem cell transplantation (SCT) is a curative treatment for children with primary immunodeficiencies.

METHODS

The present retrospective analysis describes the long-term outcomes at a median follow-up of 9 years of 29 patients with immunodeficiency after SCT; 5 sibling and 24 alternative donor transplantations. T-cell engraftment emphazed on thymic dependent signal-joint T-cell receptor excision circles (sjTREC) generation and donor chimerism in relation to killer cell immunoglobulin-like receptor genes and their ligands.

RESULTS

All children except two were reconstituted successfully from grafted material, including 9 and 18 cases of mixed chimerism (MC) and complete chimerism (CC), respectively. Univariate analyses showed that the number of activating KIR genes or HLA-C1/C2 ligand mismatches (P = .048) and possibly transplantation from an alternative donor (P = .054) facilitated CC development. Multivariate analysis showed that the presence of donor KIR haplotype B or incompatibility within C1/C2 ligands (relative risk, 6.1; 95% confidence interval, 1.08-34.69; P = .025) were significantly associated with the development of CC.

CONCLUSIONS

These results suggested that the donor-activating KIR gene repertoire affected successful engraftment.

HLA-haploidentical transplantations for primary immunodeficiencies: a single-center experience

SCID is characterized by profound deficiencies of T and B lymphocytes. HSCT is the only curative treatment for children with SCID. The clinical characteristics and outcome of 30 HLA-haploidentical transplantations in 18 patients (15 SCID, two Omenn syndrome, and one MHC Class II deficiency) are reported here. The age of patients at diagnosis ranged from one and half to nine months (median: four months). The median time was one month between the diagnosis and the time of the initial transplantation. Infused CD34+ stem cell dose was ranged between 7 and 94.2 × 10(6) /kg. Nine of 18 patients were found to be positive for CMV antigenemia at diagnosis; therefore, none of them received a conditioning regimen. The most common complication was graft failure (61%), so repeated transplantations (two to four) were performed in seven patients. The mean time of lymphoid engraftment was 17.5 days (median: 16, range: 11-29 days). Ten of 15 SCID (67%) patients survived with a stable complete donor chimerism. However, all three non-SCID patients died. In conclusion, in the absence of a matched family donor, HLA-haploidentical transplantation from parental donors represents a readily available treatment option especially for patients with SCID, offering a high chance of cure.

Artemis splice defects cause atypical SCID and can be restored in vitro by an antisense oligonucleotide

Artemis deficiency is known to result in classical T-B- severe combined immunodeficiency (SCID) in case of Artemis null mutations, or Omenn's syndrome in case of hypomorphic mutations in the Artemis gene. We describe two unrelated patients with a relatively mild clinical T-B- SCID phenotype, caused by different homozygous Artemis splice-site mutations. The splice-site mutations concern either dysfunction of a 5' splice-site or an intronic point mutation creating a novel 3' splice-site, resulting in mutated Artemis protein with residual activity or low levels of wild type (WT) Artemis transcripts. During the first 10 years of life, the patients suffered from recurrent infections necessitating antibiotic prophylaxis and intravenous immunoglobulins. Both mutations resulted in increased ionizing radiation sensitivity and insufficient variable, diversity and joining (V(D)J) recombination, causing B-lymphopenia and exhaustion of the naive T-cell compartment. The patient with the novel 3' splice-site had progressive granulomatous skin lesions, which disappeared after stem cell transplantation (SCT). We showed that an alternative approach to SCT can, in principle, be used in this case; an antisense oligonucleotide (AON) covering the intronic mutation restored WT Artemis transcript levels and non-homologous end-joining pathway activity in the patient fibroblasts.

Key players for T-cell regeneration

PURPOSE OF REVIEW

The thymus provides a unique and essential microenvironment for T-cell precursors to develop into mature functionally competent T lymphocytes. Ageing causes architectural changes in the thymus resulting in a loss of thymic epithelial space required for thymopoiesis - a process known as thymic involution. Additionally, cytoablative regimens used to treat malignancies also destroy thymic architecture. The net result of both processes is diminished thymic output and function that may lead to impaired immunity. Thus, immunocompromised individuals would benefit from strategies aimed at enhancing T-cell reconstitution.

RECENT FINDINGS

Here we discuss strategies such as the use of sex steroid ablation, keratinocyte growth factor, interleukin-7, and in-vitro-generated progenitor T cells as candidates for restoring T-cell immunity. Using various animal models of ageing or hematopoietic stem cell transplantation, these strategies have been shown to restore thymic architecture and cellularity, resulting in increased output and T-cell function in the periphery.

SUMMARY

These candidate approaches are currently being tested in clinical trials, with preliminary evidence showing encouraging effects on T-cell reconstitution. Nevertheless, although these strategies show clear promise in animal models, and in early human trials, further data are needed to determine their efficacy in patients.

Haploidentical bone marrow transplantation in primary immune deficiency: stem cell selection and manipulation

Since the early 1980s T-cell depletion has allowed haploidentical bone marrow transplantation to be performed in patients with primary immunodeficiency for whom a matched sibling donor was not available, without causing severe graft versus host disease (GVHD). This review article presents the available data in the literature on survival, GVHD, and immune reconstitution in different categories of patients, with special emphasis on the impact of different T-cell depletion methods.