Neonatal bone marrow transplantation for severe combined immunodeficiency

Review of Treatment for Adenosine Deaminase Deficiency (ADA) Severe Combined Immunodeficiency (SCID)

Adenosine deaminase deficiency (ADA) is a purine salvage pathway deficiency that results in buildup of toxic metabolites causing death in rapidly dividing cells, especially lymphocytes. The most complete form of ADA leads to severe combined immune deficiency (SCID). Treatment with enzyme replacement therapy (ERT) was developed in the 1970s and became the treatment for ADA SCID by the 1980s. It remains an option for some infants with SCID, and a stopgap measure for others awaiting curative therapy. For some infants with ADA SCID who have matching family donors hematopoietic stem cell transplant (HSCT) is an option for cure. Gene therapy for ADA SCID, approved in some countries and in trials in others, is becoming possible for more infants with this disorder. This review covers the history of ADA SCID, the treatment options to date and particularly the history of the development of gene therapy for ADA SCID and the current state of the risks and benefits of the gene therapy option.

Evaluation of Severe Combined Immunodeficiency and Combined Immunodeficiency Pediatric Patients on the Basis of Cellular Radiosensitivity

Pediatric patients with severe or nonsevere combined immunodeficiency have increased susceptibility to severe, life-threatening infections and, without hematopoietic stem cell transplantation, may fail to thrive. A subset of these patients have the radiosensitive (RS) phenotype, which may necessitate conditioning before hematopoietic stem cell transplantation, and this conditioning includes radiomimetic drugs, which may significantly affect treatment response. To provide statistical criteria for classifying cellular response to ionizing radiation as the measure of functional RS screening, we analyzed the repair capacity and survival of ex vivo irradiated primary skin fibroblasts from five dysmorphic and/or developmentally delayed pediatric patients with severe combined immunodeficiency and combined immunodeficiency. We developed a mathematical framework for the analysis of γ histone 2A isoform X foci kinetics to quantitate DNA-repair capacity, thus establishing crucial criteria for identifying RS. The results, presented in a diagram showing each patient as a point in a 2D RS map, were in agreement with findings from the assessment of cellular RS by clonogenic survival and from the genetic analysis of factors involved in the nonhomologous end-joining repair pathway. We provide recommendations for incorporating into clinical practice the functional assays and genetic analysis used for establishing RS status before conditioning. This knowledge would enable the selection of the most appropriate treatment regimen, reducing the risk for severe therapy-related adverse effects.

Eliminating SCID row: new approaches to SCID

Treatments for patients with SCID by hematopoietic stem cell transplantation (HSCT) have changed this otherwise lethal primary immune deficiency disorder into one with an increasingly good prognosis. SCID has been the paradigm disorder supporting many key advances in the field of HSCT, with first-in-human successes with matched sibling, haploidentical, and matched unrelated donor allogeneic transplantations. Nevertheless, the optimal approaches for HSCT are still being defined, including determining the optimal stem cell sources, the use and types of pretransplantation conditioning, and applications for SCID subtypes associated with radiosensitivity, for patients with active viral infections and for neonates. Alternatively, autologous transplantation after ex vivo gene correction (gene therapy) has been applied successfully to the treatment of adenosine deaminase-deficient SCID and X-linked SCID by vector-mediated gene addition. Gene therapy holds the prospect of avoiding risks of GVHD and would allow each patient to be their own donor. New approaches to gene therapy by gene correction in autologous HSCs using site-specific endonuclease-mediated homology-driven gene repair are under development. With newborn screening becoming more widely adopted to detect SCID patients before they develop complications, the prognosis for SCID is expected to improve further. This chapter reviews recent advances and ongoing controversies in allogeneic and autologous HSCT for SCID.

Use of V(D)J recombination excision circles to identify T- and B-cell defects and to monitor the treatment in primary and acquired immunodeficiencies

T-cell receptor excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs) are circular DNA segments generated in T and B cells during their maturation in the thymus and bone marrow. These circularized DNA elements persist in the cells, are unable to replicate, and are diluted as a result of cell division, thus are considered markers of new lymphocyte output. The quantification of TRECs and KRECs, which can be reliably performed using singleplex or duplex real-time quantitative PCR, provides novel information in the management of T- and B-cell immunity-related diseases. In primary immunodeficiencies, when combined with flow cytometric analysis of T- and B-cell subpopulations, the measure of TRECs and KRECs has contributed to an improved characterization of the diseases, to the identification of patients’ subgroups, and to the monitoring of stem cell transplantation and enzyme replacement therapy. For the same diseases, the TREC and KREC assays, introduced in the newborn screening program, allow early disease identification and may lead to discovery of new genetic defects. TREC and KREC levels can also been used as a surrogate marker of lymphocyte output in acquired immunodeficiencies. The low number of TRECs, which has in fact been extensively documented in untreated HIV-infected subjects, has been shown to increase following antiretroviral therapy. Differently, KREC number, which is in the normal range in these patients, has been shown to decrease following long-lasting therapy. Whether changes of KREC levels have relevance in the biology and in the clinical aspects of primary and acquired immunodeficiencies remains to be firmly established.

T-cell Receptor and K-deleting Recombination Excision Circles in Newborn Screening of T- and B-cell Defects: Review of the Literature and Future Challenges

Since its introduction as a public health programme in the United States in the early 1960s, newborn blood screening (NBS) has evolved from the detection of phenylalanine levels on filter paper to the application of DNA-based technologies to identify T-cell lymphopenia in infants with severe combined immunodeficiency. This latter use of NBS has required the development of an assay for T-cell lymphopenia based on the quantification of T-cell receptor excision circles (TRECs) that could be performed on dried blood spots routinely collected from newborn infants. The TREC-based NBS was developed six years ago, and there have already been 7 successful pilot studies since then. Similarly, efforts are now being made to establish a screen for B-cell defects, in particular agammaglobulinaemia, taking advantage of the introduction of the method for the quantification of K-deleting recombination excision circles (KRECs). A further achievement of NBS could be the simultaneous recognition of T- and B-cell defects using the combined quantification of TRECs and KRECs from Guthrie card blood spots. This approach may help the early identification of infants with T- and B-cell deficiencies so that they can then be referred to specialised paediatric centres, where a precise diagnosis of severe combined immunodeficiency and agammaglobulinaemia can be performed, and where then they can immediately receive specific therapy. Simultaneous TREC and KREC quantification should also allow classification of patients into subgroups and help identify children with less serious primary immunodeficiencies. This would help avoid the opportunistic infections and frequent hospitalisations that result from a late or lack of diagnosis.

The long quest for neonatal screening for severe combined immunodeficiency

Early recognition of severe combined immunodeficiency (SCID) is a pediatric emergency because a diagnosis before live vaccines or nonirradiated blood products are given and before development of infections permits lifesaving unfractionated HLA-identical or T cell-depleted haploidentical hematopoietic stem cell transplantation, enzyme replacement therapy, or gene therapy. The need for newborn screening for this condition has been recognized for the past 15 years. However, implementation of screening required development of an assay for T-cell lymphopenia that could be performed on dried bloodspots routinely collected from newborn infants for the past 48 years. This was accomplished 6 years ago, and there have already been 7 successful pilot studies. A recommendation to add SCID to the routine newborn-screening panel was approved by the Secretary's Advisory Committee on Heritable Disorders of Newborns and Children in 2010 and was soon after approved by the Secretary of Health and Human Services. It is important for allergists, immunologists, and other health care providers to take an active role in promoting newborn screening for SCID and other T-lymphocyte abnormalities in their states. Even more important will be their roles in establishing accurate diagnoses for infants with positive screen results and in ensuring that they are given the best possible treatment.

Transplantation of hematopoietic stem cells and long-term survival for primary immunodeficiencies in Europe: entering a new century, do we do better?

BACKGROUND

Hematopoietic stem cell transplantation remains the only treatment for most patients with severe combined immunodeficiencies (SCIDs) or other primary immunodeficiencies (non-SCID PIDs).

OBJECTIVE

To analyze the long-term outcome of patients with SCID and non-SCID PID from European centers treated between 1968 and 2005.

METHODS

The product-limit method estimated cumulative survival; the log-rank test compared survival between groups. A Cox proportional-hazard model evaluated the impact of independent predictors on patient survival.

RESULTS

In patients with SCID, survival with genoidentical donors (n = 25) from 2000 to 2005 was 90%. Survival using a mismatched relative (n = 96) has improved (66%), similar to that using an unrelated donor (n = 46; 69%; P = .005). Transplantation after year 1995, a younger age, B(+) phenotype, genoidentical and phenoidentical donors, absence of respiratory impairment, or viral infection before transplantation were associated with better prognosis on multivariate analysis. For non-SCID PID, in contrast with patients with SCID, we confirm that, in the 2000 to 2005 period, using an unrelated donor (n = 124) gave a 3-year survival rate similar to a genoidentical donor (n = 73), 79% for both. Survival was 76% in phenoidentical transplants (n = 23) and worse in mismatched related donor transplants (n = 47; 46%; P = .016).

CONCLUSION

This is the largest cohort study of such patients with the longest follow-up. Specific issues arise for different patient groups. Patients with B-SCID have worse survival than other patients with SCID, despite improvements in each group. For non-SCID PID, survival is worse than SCID, although more conditions are now treated. Individual disease categories now need to be analyzed so that disease-specific prognosis may be better understood and the best treatments planned.

Systematic evidence review of newborn screening and treatment of severe combined immunodeficiency

CONTEXT

Severe combined immunodeficiency (SCID) is a group of disorders that leads to early childhood death as a result of severe infections. Recent research has addressed potential newborn screening for SCID.

OBJECTIVE

To conduct a systematic review of the evidence for newborn screening for SCID, including test characteristics, treatment efficacy, and cost-effectiveness.

METHODS

We searched Medline and the OVID In-Process & Other Non-Indexed Citations databases. We excluded articles if they were reviews, editorials or other opinion pieces, or case series of fewer than 4 patients or if they contained only adult subjects or nonhuman data. The remaining articles were systematically evaluated, and data were abstracted by 2 independent reviewers using standardized tools. For topics that lacked published evidence, we interviewed experts in the field.

RESULTS

The initial search resulted in 719 articles. Twenty-six met inclusion criteria. The results of several small studies suggested that screening for SCID is possible. Interviews revealed that 2 states have begun pilot screening programs. Evidence from large case series indicates that children receiving early stem-cell transplant for SCID have improved outcomes compared with children who were treated later. There is some inconclusive evidence regarding the need for donor-recipient matching and use of pretransplant chemotherapy. Few data on the cost-effectiveness of a SCID-screening program.

CONCLUSIONS

Evidence indicates the benefits of early treatment of SCID and the possibility of population-based newborn screening. Better information on optimal treatment and the costs of treatment and screening would benefit policy makers deciding among competing health care priorities.

Bone marrow transplantation for primary immunodeficiency diseases

Advances in immunology have led to a breathtaking expansion of recognized primary immunodeficiency diseases (PID) with over 120 disease-related genes identified. In North America alone more than 1000 children have received allogeneic blood or marrow transplant over the past 30 years, with the majority surviving long term. This review presents results and highlights challenges and notable advances, including novel less toxic conditioning regimens, to transplant the more common and severe forms of PID. HLA-matched sibling donors remain the ideal option, however, advances in living donor unrelated HSCT and banked umbilical cord blood grafts provide hope for all children with severe PID.

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Update on the treatment of primary immunodeficiencies

A general review of advances in the treatment of Primary Immunodeficiencies (PID) has been performed. Treatment with immunoglobulins is indicated in cases of humoral immunodeficiencies and in selected cases of combined immunodeficiencies. The use of intramuscular immunoglobulins in the treatment of PID was abandoned after obtaining the intravenous immunoglobulins, since these are much more effective and have fewer adverse effects. Now subcutaneous immunoglobulins are also available. Immunoglobulins help to keep the patients free of symptoms and infections as these substances are able to neutralise infectious agents, modulate and promote the immune response and favour phagocytosis. Adverse effects have been reported in 5-15 % of patients receiving IVIg, and patients with deficiencies of subclasses of IgG with IgA deficiency and/or anti-IgA antibodies are at risk of severe reactions. No severe adverse effects of subcutaneous immuneglobulins have been reported and the medication can be self-administered. The efficacy and safety of IVIg and SCIg are similar and SCIg administered at home is associated with better quality of life. Stem Cell Transplantation (SCT) in Primary Immunodeficiencies is aimed at restoring the number and/or function of lymphocytes or phagocytes. Matched, related or unrelated donors, or related haploidentical donors are selected. HLA class II mismatched unrelated donors are avoided owing to the risk of severe graft versus host disease (GVHD). Stem cells are obtained from bone marrow, cord blood or peripheral blood. Prophylactic immunossupression (as well as donor T lymphocyte depletion in haploidentical and unrelated donors) is performed to avoid or minimize GVHD. Less toxic "reduced intensity" protocols now exist for pre-transplantation conditioning, indicated to avoid graft rejection if there is residual T-lymphocyte immunity in the host. In the majority of Severe Combined Immunodeficiencies (SCID), SCT results in T lymphocytes graft and the antibody immunodeficiency persists in many cases. The results are better the earlier it is performed, with the absence of previous infections, and with the degree of matching. The patient must be maintained in a laminar flow room with broad anti-infectious prophylaxis and with the intravenous administration of gammaglobulin for a variable period. Many other complications can be expected. Gene therapy. Patients with PID are ideal candidates, as they are monogenic, the haematopoietic cells are easily obtained and virus replication is easy within them. Vectors (viruses) "infect" the stem cells of the patient's bone marrow, producing the transfection of the wild (healthy) gene in these cells. Encouraging results have been achieved in X-linked SCID as there are a number of patients who are considered "cured", although neoplastic processes have occurred due to the activation of proto-oncogenes close to the point of insertion of the external gene, using retroviruses as vectors; there are now trials with adenovirus, physical methods (direct injection...) and chemical methods (viral modification, artificial viruses...). Gene therapy has also been performed in patients with Chronic Granulomatous Disease and trials will improve in the future with changes in protocols used in oncology and infectious diseases.

Nursing care of the premature infant with severe combined immunodeficiency disease

Diagnosis and treatment of severe combined immunodeficiency disease (SCID) is documented in fetuses, term infants, and older children; however, there is very little information on its diagnosis and treatment in premature infants. When Duke University Medical Center's first preterm infant with a known SCID history was delivered, in June 1999, there was no defined protocol for the infant's nursing care. Although many of the guidelines for nursing care of the premature infant population (< or = 36 weeks) apply, there are important considerations for preterm infants with an SCID diagnosis. This article provides background on SCID and identifies those special considerations--namely, multidisciplinary communication, infection prevention, thorough physical assessments, and parental support.

T-cell-depleted CD34+ cell transplantation from an HLA-mismatched donor in a low-birthweight infant with X-linked severe combined immunodeficiency

The best strategy of hematopoietic stem cell (HSC) transplantation for low-birthweight (LBW) infants with severe combined immunodeficiency (SCID) remains to be determined. To avoid the toxicity of drugs used for the transplantation and the risk of graft-versus-host disease (GVHD), the authors performed allogeneic bone marrow HSC transplantation with a combination of CD34 selection and T-cell depletion in a LBW infant with X-linked SCID. The authors analyzed the process of T-cell reconstitution after the transplantation in this patient. The patient was born at 30 weeks and 2 days' gestational age via cesarean section. He was diagnosed as having SCID at birth. The patient received a transplant of 1 million CD34+ cells/kg body weight. Immunologic reconstitution was investigated by means of phenotypic analysis of T cells and genetic analysis of coding joint T-cell receptor rearrangement excision circle expression. Increases in donor-derived NK cells and T cells were observed 2 and 3 months after the transplantation, respectively. The patient had no infectious complications or GVHD despite the presence of SCID and prematurity-associated immunodeficiency. Analysis of T-cell regeneration pathways revealed that T cells reconstituted mainly via the thymus-dependent pathway. T-cell-depleted CD34+ cell transplantation would be a safe and useful therapy for LBW infants with SCID.

Allogeneic stem cell transplantation for treatment of immunodeficiency

Primary immunodeficiencies constitute a group of highly complex congenital disorders commonly characterized by an extremely poor prognosis. Allogeneic hematopoietic stem cell transplantation has the potential to establish a permanently functioning immune system and represents a curative approach in many of these disorders. In this review several aspects of stem cell transplantation are presented, with an emphasis on the mechanism of immune reconstitution in severe combined immunodeficiency diseases. In this disorder transplant modalities vary, and also include transplantation without cytoreductive conditioning. Clinical results are summarized based on recent analysis performed in large patient cohorts, which have shown steady improvements and have led to a marked change in the prognosis of patients with primary immunodeficiencies.

Cell-based therapies for birth defects: a role for adult stem cell plasticity?

Cell therapy can offer a reasonable approach to the treatment of specific birth defects, particularly those for which hematopoietic stem cells (HSCs) can be used to restore (even partially) the number of cells, protein levels, or enzyme activity. Relatively few clinical experiences have been published on this subject, but when a natural selective advantage exists for the cell graft, a degree of "rescue" is possible. Strategies have been developed to confer a selective advantage through genetic engineering of donor cells, and this approach may prove valuable in the treatment of birth defects, as it is in hematological malignancy. Stem cell (SC) plasticity, or transdifferentiation, may offer another route for delivery of cells to established or developing organs. A wide variety of studies support the concept that adult tissue-specific SCs can, if displaced from their normal niche to another, be reprogrammed to produce cell types appropriate to their new environment. Clinical observations reveal that persistent tissue microchimerism develops not only in blood lineages after transfusion, but also in thyroid follicular epithelium via transplacental exchange. In addition, hepatic and renal parenchyma also become chimeric following allografts or bone marrow transplantation (BMT). Experimental models indicate that a renal glomerulosclerosis phenotype can be transferred by grafting whole BM, and that a severe liver disorder in fah-/- mice can be overcome by grafting HSCs and then exerting a selection pressure. It may be possible in the future to exploit the ability of adult SCs to contribute to diverse tissues; however, our understanding of the processes involved is at a very early stage.

X-linked severe combined immunodeficiency

Severe combined immunodeficiency is one of the most common causes of primary immunodeficiencies in humans. Molecular biological techniques have allowed new, therapeutically useful treatments for these diseases to be introduced into clinical practice. This review will focus on the molecular basis and new treatments for X-linked severe combined immunodeficiency.

Primary immunodeficiency diseases: dissectors of the immune system

The past 50 years have seen enormous progress in this field. An unknown concept until 1952, there are now more than 100 different primary immunodeficiency syndromes in the world's literature. Each novel syndrome has shed new insight into the workings of the immune system, dissecting its multiple parts into unique functioning components. This has been especially true over the past decade, as the molecular bases of approximately 40 of these diseases have been identified in rapid succession. Advances in the treatment of these diseases have also been impressive. Antibody replacement has been improved greatly by the development of human immunoglobulin preparations that can be safely administered by the intravenous route, and cytokine and humanized anticytokine therapies are now possible through recombinant technologies. The ability to achieve life-saving immune reconstitution of patients with lethal severe combined immunodeficiency by administering rigorously T-cell-depleted allogeneic related haploidentical bone marrow stem cells has extended this option to virtually all such infants, if diagnosed before untreatable infections develop. Finally, the past 3 years have witnessed the first truly successful gene therapy. The impressive results in X-linked severe combined immunodeficiency offer hope that this approach can be extended to many more diseases in the future.