European experience of bone-marrow transplantation for severe combined immunodeficiency

Successful unmanipulated haploidentical bone marrow transplantation from an HLA 2-locus-mismatched mother for Wiskott-Aldrich syndrome after unrelated cord blood stem cell transplantation

The authors describe a boy with Wiskott-Aldrich syndrome (WAS) who was diagnosed immediately after birth using flow cytometric and genetic analysis. At 1 year of age he received unrelated cord blood stem cell transplantation (UCBSCT); however, the sex chromosomes of the peripheral blood mononuclear cells showed that the recipient type was over 70%. This rate gradually increased to over 90% after immunosuppressant therapy was discontinued. Clinical manifestations, including high fever, graft-versus-host disease (GVHD)-like eruptions, and signs of infection recurred. Results of flow cytometric and genetic analysis of mononuclear cells from the boy's mother were normal with no mutation. Three months after UCBSCT, he received an unmanipulated HLA-haploidentical 2-locus-mismatched bone marrow transplant (BMT) from his mother. The prophylaxis against GVHD was tacrolimus and short-term methotrexate. Hematopoietic reconstitution was rapid and fluorescence in situ hybridization analysis revealed sustained engraftment. Grade II acute GVHD developed but improved rapidly with the administration of methylprednisolone. The patient is progressing well and displays complete chimerism 2 years after the BMT. This case suggests that unmanipulated haploidentical BMT from the mother might be feasible not only for malignant disease but also for immunodeficiency disease patients who urgently need stem cell transplants and have no HLA-identical donors.

Retinoic acid may increase the risk of bone marrow transplant nephropathy

Bone marrow transplant nephropathy (BMTN) classically presents more than 100 days after transplantation as an acute nephritis with hypertension, azotaemia and anemia that usually results in end stage renal failure (ESRF). The risk of developing BMTN may be greater with the use of more intensive chemotherapy and higher total body and tumor bed irradiation. Cis-retinoic acid (RA) may further increase the risk of developing BMTN. Here, we report the cases of two children who developed typical clinical and biochemical features of BMTN. They were both treated for stage IV neuroblastoma with chemotherapy, bone marrow transplant (BMT) conditioning that included total body irradiation and RA therapy after BMT, although the patient in case 1 had established renal insufficiency prior to the commencement of RA. Renal biopsy of these children showed classical BMTN histology, and the renal manifestations progressed quickly; the patient in case 1 became dialysis dependent by 1 year post-bone marrow transplant. Recently, RA has been added to the post-BMT therapy in children with stage IV neuroblastoma. The occurrence of BMTN in two children treated with RA in our unit is unlikely to be coincidental. Although RA has been shown to confer a significant survival advantage in this disease, animal studies and a previous case report have suggested it could increase the toxic effects of chemotherapy and renal irradiation. It is likely that RA contributed to the deterioration in renal function in these patients.

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.

Gene therapy for adenosine-deaminase-deficient severe combined immunodeficiency

Adenosine-deaminase-deficient SCID was the first inherited disease to be treated with gene therapy. This life-threatening disorder is characterized by a purine defect that leads to impaired immune functions, recurrent infections and systemic metabolic abnormalities. The early gene therapy trials showed the safety and feasibility of engineering haematopoietic stem cells and peripheral blood lymphocytes using retroviral vectors. However, all patients were maintained on enzyme-replacement therapy, which prevented the evaluation of its efficacy and abolished the selective advantage for gene-corrected cells. It is only recently that the clinical efficacy of gene therapy has been investigated in the absence of enzyme-replacement therapy. Results of these studies showed that gene therapy with peripheral blood lymphocytes allowed correction of the T-cell defect, but provided insufficient systemic detoxification. Gene transfer in bone marrow stem cells, associated with non-myeloablative conditioning, allowed full immunological and metabolic correction of the adenosine-deaminase defect with clinical benefit. These results have important implications for future applications of gene therapy in other blood-borne disorders.

Impact of HLA matching on outcome of hematopoietic stem cell transplantation in children with inherited diseases: a single-center comparative analysis of genoidentical, haploidentical or unrelated donors

SUMMARY

Hematological inherited diseases can be cured by hematopoietic stem cell transplantation (HSCT) from an human leukocyte antigen (HLA)-identical sibling donor (MSD), but the outcome of unrelated donors (URD) or haploidentical donors (HMD) has been a cause of concern. In all, 94 children affected with inherited diseases underwent HSCT at a single center using MSD (group A, n=31), URD (group B, n=23) or HMD (group C, n=40). There was no difference in the rate of engraftment or in the incidence of grades III-IV acute graft-versus-host disease (GVHD) between the groups. Survival rate was 80.6% in group A, 62.5% in group B and 47.5% in group C (P=0.023). In group B, survival rate was 73.7% in the subgroup with zero or one class I mismatch, and 25% in the subgroup with two or more class I mismatches (P=0.04). In group C, survival rate was 83.3% in the 9/10-identical subgroup, 64.3% in the seven or 8/10 subgroup, and 25% in the five or 6/10 subgroup (P=0.0007). Thus, engraftment, incidence of GVHD and survival are similar in recipients of grafts from MSD, URD with 0-1 class I-mismatch, or HMD with at least 7/10 HLA matches. The low success of HSCT using more disparate donors suggests reserving them for patients with very poor prognosis.

MolecularDefects inHumanSevereCombinedImmunodeficiency andApproaches toImmuneReconstitution

Mutations in nine different genes have been found to cause the human severe combined immunodeficiency syndrome. The products of three of the genes--IL-2RG, Jak3, and IL-7R alpha--are components of cytokine receptors, and the products of three more-RAG1, RAG2, and Artemis-are essential for effecting antigen receptor gene rearrangement. Additionally, a deficiency of CD3 delta, a component of the T-cell antigen receptor, results in a near absence of circulating mature CD3+ T cells and a complete lack of gamma/delta T cells. Adenosine deaminase deficiency results in toxic accumulations of metabolites that cause T cell apoptosis. Finally, a deficiency of CD45, a critical regulator of signaling thresholds in immune cells, also causes SCID. Approaches to immune reconstitution have included bone marrow transplantation and gene therapy. Bone marrow transplantation, both HLA identical unfractionated and T cell-depleted HLA haploidentical, has been very successful in effecting immune reconstitution if done in the first 3.5 months of life and without pretransplant chemotherapy. Gene therapy was highly successful in nine infants with X-linked SCID, but the trials have been placed on hold due to the development of a leukemic process in two of the children because of insertional oncogenesis.

Mutations in genes required for T-cell development:IL7R, CD45, IL2RG, JAK3, RAG1, RAG2, ARTEMIS, and ADA and severe combined immunodeficiency: HuGE review

Severe combined immunodeficiency (SCID) is an inherited immune disorder characterized by T-cell lymphopenia (TCLP), a profound lack of cellular (T-cell) and humoral (B-cell) immunity and, in some cases, decreased NK-cell number and function. Affected children develop severe bacterial and viral infections within the first 6 months of life and die before 1 year of age without treatment. Mutations in any of eight known genes: IL2RG, ARTEMIS, RAG1, RAG2, ADA, CD45, JAK3, and IL7R cause SCID. Mutations in unidentified genes may also cause SCID. Population-based genotype and allelic frequencies of these gene defects have not been measured. Some minimal estimates of SCID prevalence are presented. Currently, hematopoietic stem cell transplants are the standard treatment. In clinical trials, gene therapy has been used to reconstitute immune function in patients with IL2RG and ADA defects. The availability of effective therapies, plus the short asymptomatic period after birth, (when stem-cell transplantation is most effective), make SCID a potentially good candidate for newborn screening. Dried blood spots are currently collected from all infants at birth for newborn metabolic screening. Tests for TCLP on dried blood spots could be developed as a screen for SCID. Because SCID may be unrecognized, with infant deaths from infection attributed to other causes, newborn screening is the only way to ascertain true birth prevalence. Validated tests and pilot population studies are necessary to determine newborn screening's potential for identifying infants with SCID.

The role of haploidentical stem cell transplantation in the management of children with haematological disorders

The broader application of stem cell transplantation (SCT) for paediatric diseases has been limited by a lack of human leucocyte antigen (HLA)-matched donors. Virtually all children, however have at least one haploidentical parent who could serve as a donor. Such a donor is immediately available and the considerable costs of additional HLA typing, registry and banking expenditures that are necessary to procure an unrelated donor, could be reduced. Recent technological advances appear to have overcome the historical problems of graft rejection and severe graft versus host disease in the haploidentical setting, and in the latest studies the overall survival for children undergoing haploidentical SCT for leukaemia is now comparable with that following unrelated donor bone marrow or cord blood transplantation. Post-transplant infectious complications and leukaemia relapse remain the most important barriers yet to overcome, and new directions in the use of adoptive cellular immunity appear to be promising in this respect. Haploidentical SCT is now a viable option for those children who do not have an HLA compatible sibling or fully matched unrelated donor. The relative merits of a haploidentical family donor versus mismatched unrelated bone marrow or cord blood donation needs to be assessed in prospective, randomized clinical trials.

Long-term survival and transplantation of haemopoietic stem cells for immunodeficiencies: report of the European experience 1968-99

BACKGROUND

Transplantation of allogeneic haemopoietic stem cells can cure several primary immunodeficiencies. This European report focuses on the long-term results of such procedures done between 1968 and December, 1999, for primary immunodeficiencies.

METHODS

The report includes data from 37 centres in 18 countries, which participated in a European registry for stem-cell transplantation in severe combined immuno deficiencies (SCID) and in other immunodeficiency disorders (non-SCID). 1082 transplants in 919 patients were studied (566 in 475 SCID patients, 512 in 444 non-SCID patients; four procedures excluded owing to insufficient data). Minimum follow-up of 6 months was required.

FINDINGS

In SCID, 3-year survival with sustained engraftment was significantly better after HLA-identical than after mismatched transplantation (77% vs 54%; p=0.002) and survival improved over time. In HLA-mismatched stem-cell transplantation, B(-) SCID had poorer prognosis than B(+) SCID. However, improvement with time occurred in both SCID phenotypes. In non-SCID, 3-year survival after genotypically HLA-matched, phenotypically HLA-matched, HLA-mismatched related, and unrelated-donor transplantation was 71%, 42%, 42%, and 59%, respectively (p=0.0006). Acute graft versus host disease predicted poor prognosis whatever the donor origin except in related HLA-identical transplantation in SCID.

INTERPRETATION

The improvement in survival over time indicates more effective prevention and treatment of disease-related and procedure-related complications--eg, infections and graft versus host disease. An important factor is better prevention of graft versus host disease in the HLA-non-identical setting by use of more efficient methods of T-cell depletion. For non-SCID, stem-cell transplantation can provide a cure, and grafts from unrelated donors are almost as beneficial as those from genetically HLA-identical relatives.

CAMPATH-1M T-cell depleted BMT for SCID: long-term follow-up of 19 children treated 1987-98 in a single center

BACKGROUND

SCID can be cured by BMT. Depletion of mature T cells from BM has enabled HLA non-identical stem-cell transplantation. We report the outcome of 30 patients treated with 37 T-cell depleted BMT procedures using CAMPATH-1M in vitro between 1987-98 in a single center.

METHODS

Immune reconstitution and quality-of-life were assessed in 19 longterm survivors. All but two received pre-transplant conditioning. T- and B-cell chimerism, numbers and function were analyzed during a median follow-up of 5.3 years (range 1.33-12).

RESULTS

The overall engraftment rate was 59%, six children required repeated BMT and the survival rate was 63%. All have donor T cells, 58% normal T-cell numbers and 74% normal T-cell function. Of 17 evaluated, 16 patients (94%) have normal IgM and IgG levels, and production of specific Abs to protein Ags, but only 5/16 (31%) have a good response to pneumococcal polysaccharide. Early and late post-BMT complications were rare and there were no delayed deaths. Only one child continues on long-term i.v. Ig 4-years post-BMT. Eleven children died (37%).

DISCUSSION

CAMPATH-1M T-cell depleted BMT for SCID resulted in 63% survival. Deaths of 11 children were mainly due to pre-existing infections. Seventeen of 19 long-term survivors have normal immune function and good quality-of-life.

Reconstitution of lymphoid development and function in ZAP-70-deficient mice following gene transfer into bone marrow cells

Mutations in the ZAP-70 protein tyrosine kinase gene result in a severe combined immunodeficiency (SCID) characterized by a selective inability to produce CD8(+) T cells and a signal transduction defect in peripheral CD4(+) cells. Transplantation of genetically modified hematopoietic progenitor cells that express the wild-type ZAP-70 gene may provide significant benefit to some of these infants. The feasibility of stem cell gene correction for human ZAP-70 deficiency was assessed using a ZAP-70 knock-out model. ZAP-70-deficient murine bone marrow progenitor cells were transduced with a retroviral vector expressing the human ZAP-70 gene. Engraftment of these cells in irradiated ZAP-70-deficient animals resulted in the development of mature CD4(+) and CD8(+) T cells. In marked contrast, both populations were absent in ZAP-70(-/-) mice undergoing transplantation with bone marrow progenitor cells transduced with a control vector. Importantly, ZAP-70-reconstituted T cells proliferated in response to T-cell receptor stimulation. Moreover, these ZAP-70-expressing T cells demonstrated a diverse T-cell receptor repertoire as monitored by the relative usage of each T-cell receptor beta chain hypervariable region subfamily. The presence of ZAP-70 in B cells did not affect either lipopolysaccharide- or lipopolysaccharide/interleukin-4-mediated immunoglobulin isotype switching. Altogether, these data indicate that retroviral-mediated gene transfer of the ZAP-70 gene may prove to have a therapeutic benefit for patients with ZAP-70-SCID.

Prenatal T-cell reconstitution after in utero transplantation with fetal liver cells in a patient with X-linked severe combined immunodeficiency

OBJECTIVE

Fetuses with severe combined immunodeficiency may be treated with intrauterine transplantation of fetal hematopoietic stem cells. In previous reports on intrauterine transplantation with T-cell-depleted bone marrow, repeated injections have led to partial immunoreconstitution at birth, with subnormal T-cell counts and a delayed response to mitogens.

STUDY DESIGN

A male fetus with X-linked severe combined immunodeficiency because of a stop mutation in the gene encoding the common gamma chain of cytokine receptors was transplanted in week 14 of gestation with a single injection of 7 x 10(7) cryopreserved nucleated fetal liver cells (9 x 10(8) cells per estimated kilogram fetal weight) into the fetal abdomen. At 24 and 33 weeks of gestational age, fetal blood samples were taken to detect evidence of engraftment. Fetal mixed chimerism was determined using polymerase chain reaction amplification of a variable number of tandem repeats and was verified by genomic HLA class II typing and flow cytometry.

RESULTS

The course of pregnancy, delivery, and the first 18 months of life have been uncomplicated. At week 24 of gestation, donor HLA class II alleles were detected at a low level in the background of the recipient's fetal HLA genotype. The chimeric proportion of donor cells was about 10% at 24 weeks of gestation, increasing to 50% at 33 weeks of gestation. Whereas the T-cell fraction was still markedly reduced in week 24, it increased thereafter and was in the normal range from week 33 of gestation. In vitro response to T-cell mitogens was normal from birth.

CONCLUSION

In utero transplantation of cryopreserved fetal liver cells in week 14 of gestation with a single injection led to complete T- and NK-cell reconstitution at birth. Signs of engraftment were found already in week 24 of gestation. We consider intrauterine transplantation a valuable experimental method and a useful adjunct to postnatal transplantation and gene therapy in the treatment of severe combined immunodeficiency.

Non-myeloablative stem cell transplantation for congenital immunodeficiencies

Allogeneic haematopoietic stem cell transplantation (HSCT) can be a highly successful treatment option for individuals with congenital immunodeficiency states. The strategy for HSCT is varied but in cases where there is preservation of residual T cell function, conditioning regimes have been used and have been based around a combination of busulphan and cyclophosphamide with or without serotherapy. In patients with coexisting organ damage this has resulted in significant morbidity and mortality. We have therefore used a low-intensity conditioning regime for transplantation in this group of immunodeficiency patients. Twenty-one patients with a variety of different immunodeficiencies were treated using the following conditioning regimes: (1) fludarabine/melphalan/ATG or Campath 1H (n=16), (2) fludarabine/cyclophosphamide/Campath 1H (n=1), (3) TBI/CyA/MMF (n=1), (4) fludarabine/melphalan/busulphan/ATG (n=3). In 13 cases matched (n=9) and 1 Ag mismatched (n=4) unrelated donors were used and in eight cases transplants from matched siblings (n=4), 1 Ag mismatched sibling (n=1), matched parent (n=1) and haploidentical parents (n=3) were performed. At a median follow-up of 13 months, 19 of 21 (90%) patients were still alive following the transplant procedure. Despite a T cell replete graft and the use of unrelated donor grafts in the majority of patients studied there was no evidence of significant organ disease. Immune reconstitution in terms of CD3+ and CD4+ T cell recovery and function was equivalent in comparison with a historical cohort. We believe that this low-intensity approach has significant implications for transplantation of individuals with immunodeficiency states with established organ disease.

HLA-haploidentical blood progenitor cell transplantation in osteopetrosis

Infantile osteopetrosis (OP) carries an extremely poor prognosis unless treated early by hematopoietic stem cell transplantation. We explored the use of purified blood progenitor cells from HLA-haploidentical parents in 7 patients lacking suitable matched donors. Blood progenitor cells were purified by positive selection and by additional T-cell depletion using rosette formation. For conditioning, patients received busulfan, thiotepa, and either cyclophosphamide (5 patients) or fludarabine (2 patients). Stable donor engraftment developed in 6 of 7 patients. Graft-versus-host disease was not observed. Three of the 7 patients had no major complications and 4 of 7 had both veno-occlusive disease and respiratory failure. Five of 7 patients survive with complete cure of OP at a median of 4 years. Patients with OP lacking HLA-matched donors can be successfully treated by transplantation of purified blood progenitor cells from HLA-haploidentical donors.

Eradication of a dysfunctional HLA-haploidentical T cell system by a second HLA-identical BMT

A 12-year-old boy treated for SCID at 1 month of age by HLA-haploidentical BMT developed a lymphoproliferative disease of unknown etiology at the age of 9 years characterized by sustained, marked elevation of circulating CD8+ donor T cells and by diffuse infiltration of the liver by CD8+ T cells. Because of progressive liver disease, the patient underwent a second BMT from a younger HLA-matched sister. This treatment induced an effective graft-versus-graft reaction and led to complete replacement of the HLA-nonidentical, dysfunctional T cell system, resolution of the hepatopathy and full reconstitution of T and B cell functions.

Bone marrow transplantation for T-B- severe combined immunodeficiency disease in Athabascan-speaking native Americans

A distinct form of autosomal recessive T-B- severe combined immunodeficiency disease occurs with a high frequency among Athabascan-speaking Native Americans (SCIDA), including Navajo and Apache Indians from the southwestern US and Dene Indians from the Canadian Northwest Territories. The SCIDA gene has been linked to markers on chromosome 10p although its identity and role in the pathogenesis of this disease are unknown. We report our experience in treating 18 Navajo and Dene children with SCIDA between 1984 and 1999; 16 underwent bone marrow transplants (BMT). All children were symptomatic within 2 months of birth, had the T-B- NK(+)SCID phenotype and 67% presented with oral and/or genital ulcers. Three children had evidence of maternal engraftment prior to transplant. Two children died shortly after diagnosis. Three children required more than one BMT and 12 are alive with T cell reconstitution at a median follow-up of 7 years. Three children developed normal B cell immunity, two of whom received ablative conditioning therapy with either radiation or busulfan. Three of the four children who died received therapy with either radiation or busulfan and two of eight long-term survivors who were also recipients of cytotoxic chemotherapy have failed to develop secondary teeth. These results demonstrate the efficacy of BMT in treating infants with this distinct form of SCID, although B cell reconstitution remains a problem even with HLA-matched donors. Without conditioning, T cell engraftment is likely when closely HLA-matched donors are used. With T cell depletion of haplocompatible marrow, conditioning with immunosuppressive therapy may be necessary; however, children with SCIDA who were treated with intensive immunosuppressive and myeloablative therapy had a poor outcome.

Mutations in severe combined immune deficiency (SCID) due to JAK3 deficiency

During the last 10 years, an increasing number of genes have been identified whose abnormalities account for primary immunodeficiencies, with defects in development and/or function of the immune system. Among them is the JAK3-gene, encoding for a tyrosine kinase that is functionally coupled to cytokine receptors which share the common gamma chain. Defects of this gene cause an autosomal recessive form of severe combined immunodeficiency with almost absent T-cells and functionally defective B-cells (T(-)B(+) SCID). Herewith, we present molecular information on the first 27 unique mutations identified in the JAK3 gene, including clinical data on all of the 23 affected patients reported so far. A variety of mutations scattered throughout all seven functional domains of the protein, and with different functional effects, have been identified. Availability of a molecular screening test, based on amplification of genomic DNA, facilitates the diagnostic approach, and has permitted recognition that JAK3 deficiency may also be associated with atypical clinical and immunological features. Development of a structural model of the JAK3 kinase domain has allowed characterization of the functional effects of the various mutations. Most importantly, molecular analysis at the JAK3 locus results in improved genetic counseling, allows early prenatal diagnosis, and prompts appropriate treatment (currently based on hematopoietic stem cell transplantation) in affected families.

Cognitive and behavioral abnormalities in adenosine deaminase deficient severe combined immunodeficiency

OBJECTIVE

The objective was to evaluate the cognitive, behavioral, and neurodevelopmental function in patients with adenosine deaminase deficient severe combined immunodeficiency (ADA-SCID) and to compare the findings with those of a case control group of patients without ADA-SCID.

STUDY DESIGN

Case-matched pairs of patients with ADA-SCID (n = 11) and patients without ADA-SCID who had undergone bone marrow transplantation were recruited. Subjects were assessed by age-appropriate standard tests of intelligence, behavior, and neurodevelopment.

RESULTS

Cognitive ability was not significantly different between the 2 groups, but patients with ADA-SCID showed a significant inverse correlation between deoxyadenosinetrisphosphate levels at diagnosis and IQ (P =.048). Behavioral assessment showed that patients with ADA-SCID functioned in the pathologic range on all domains, whereas mean scores for the control group were within normal limits. Behavioral impairment in patients with ADA-SCID also showed a significant positive correlation with age (P =.026).

CONCLUSIONS

Cognitive function in ADA deficiency is adversely affected by the severity of metabolic derangement at the time of diagnosis. In addition, patients with ADA-SCID have significant behavioral abnormalities after transplantation. These defects are not due to the transplant procedure but reflect the systemic nature of ADA deficiency. These findings have important implications for future medical and nonmedical management strategies.

Primary immunodeficiency mutation databases

Primary immunodeficiencies are intrinsic defects of immune systems. Mutations in a large number of cellular functions can lead to impaired immune responses. More than 80 primary immunodeficiencies are known to date. During the last years genes for several of these disorders have been identified. Here, mutation information for 23 genes affected in 14 immunodefects is presented. The proteins produced are employed in widely diverse functions, such as signal transduction, cell surface receptors, nucleotide metabolism, gene diversification, transcription factors, and phagocytosis. Altogether, the genetic defect of 2,140 families has been determined. Diseases with X-chromosomal origin constitute about 70% of all the cases, presumably due to full penetrance and because the single affected allele causes the phenotype. All types of mutations have been identified; missense mutations are the most common mutation type, and truncation is the most common effect on the protein level. Mutational hotspots in many disorders appear in CPG dinucleotides. The mutation data for the majority of diseases are distributed on the Internet with a special database management system, MUTbase. Despite large numbers of mutations, it has not been possible to make genotype-phenotype correlations for many of the diseases.

Reduced memory B-cell populations in boys with B-cell dysfunction after bone marrow transplantation for X-linked severe combined immunodeficiency

X-linked severe combined immunodeficiency (XSCID) is a lethal disease resulting in death in infancy. In many instances, haploidentical bone marrow transplantation (BMT) offers reconstitution of T-cell immunity alone, with residual hypogammaglobulinaemia. The exact nature of B-cell dysfunction in these patients is unclear, although differentiation arrest of the B cells is a potential explanation. To ascertain the differentiation status of peripheral blood B lymphocytes from XSCID patients after BMT, the surface expression of CD19, CD10, CD34, CD5, serum immunoglogulin (sIg)M, sIgD, sIgG and CD27 on these B cells was investigated using three-colour flow cytometry. CD27 is a marker of memory B cells. Populations of CD19+IgM-D- B cells, CD19+IgM-only, CD19+IgG+CD27+ and CD19+IgM+ CD27+ B cells were found to be diminished in the XSCID patients after BMT with persistent hypogammaglobulinaemia, compared with both post-BMT patients with B-cell function and age-matched normal controls. This indicated the lack of CD19+IgM-D- B cells, which represent Ig isotype-switched B cells, as well as CD19+IgM-only and CD19+IgG+CD27+ or CD19+IgM+CD27+ memory B-cell populations. Interaction between CD27 and its ligand CD70 has been shown to induce IgG and IgM production by CD27+ B cells. Therefore, the lack of CD27/70 interaction is a probable explanation for the hypogammaglobulinaemia in these patients after BMT.

Diagnosis of severe combined immunodeficiency

Early diagnosis of severe combined immunodeficiency (SCID) is important to enable prompt referral to a supraregional centre for bone marrow transplantation before the occurrence of end organ damage secondary to infective complications. This review outlines clinical, microbiological, and immunopathological clues that aid the diagnosis of SCID and emphasises the multidisciplinary approach needed to diagnose and treat these infants.

T-cell immunodeficiencies

T-cell immune defects include most inherited immunodeficiencies diagnosed in childhood. Most cellular immunodeficiencies have associated humoral defects with variable clinical and laboratory features. The underlying gene defects are now known for most inherited T-cell immune defects, and mutation analysis is quickly becoming an integral part of evaluation and diagnosis. Detailed discussion of disease genotype-phenotype correlation with families is critical to medical management and long-term prognosis.

Stem-cell transplantation for inherited immunodeficiency disorders

For patients with well-characterized, rapidly fatal, nonmalignant immunodeficiency disorders, such as SCID, the decision to proceed with allogeneic SCT is clear-cut. For patients with many other disorders, this decision can be extremely difficult. Disorders such as LAD or CGD have a variable natural history. Each patient must be considered individually, with the risk for SCT-related morbidity and mortality carefully weighed against that of the underlying disease. Significant advances during the past 10 years have made SCT a much safer procedure. Use of nonmyeloablative conditioning regimens as a means of reducing toxicity of high-dose chemotherapy and irradiation hold great promise. Highly immunosuppressive, nonchemotherapeutic agents that inhibit graft rejection or GVHD by blocking the critical costimulatory component of the T-cell receptor-antigen interaction are beginning to emerge and may be ideal for SCT of nonmalignant diseases. Therefore, the risk-benefit equation must be reassessed each year as the severity of patients' disorders is better defined and techniques of SCT improve.

The potential for therapy of immune disorders with gene therapy

Several hurdles remain before gene therapy will be a part of mainstream medical therapy; however, the preliminary report of success in HSC correction in patients with XSCID provides hope that gene therapy will become a reality.

Self-selection by genetically modified committed lymphocyte precursors reverses the phenotype of JAK3-deficient mice without myeloablation

Janus kinase 3 (JAK3) is an essential component of cytokine receptor signal transduction pathways required for normal lymphocyte development and function. JAK3 deficiency in both mice and humans results in severe combined immunodeficiency (SCID) and increased susceptibility to opportunistic infections. We have previously shown that JAK3 gene transfer into irradiated recipients could restore immune function. However, since this toxic conditioning would be undesirable for infants in a clinical application, we have tested whether immune function could be restored in nonmyeloablated JAK3-deficient (-/-) mice. Murine JAK3 retroviral vectors were transduced into hematopoietic stem cells from the livers of newborn JAK3(-/-) mice. These cells were then injected intraperitoneally into nonirradiated JAK3(-/-) neonates. Transduced cells were detectable in these mice at time points 4 to 6 months after injection and resulted in significant correction of T and B lymphocyte numbers and circulating immunoglobulin (Ig) levels. After immune challenge with a dose of influenza A virus that was lethal to nonmanipulated JAK3(-/-) mice, mice injected with transduced cells showed development of circulating virus-specific IgG and enhanced survival. This work shows that the large selective advantage for JAK3-corrected lymphoid cells may be sufficient to overcome the need for myeloablative conditioning in JAK3 gene therapy protocols.

Respiratory viral infections in primary immune deficiencies: significance and relevance to clinical outcome in a single BMT unit

Respiratory viral infections are major causes of morbidity and mortality in children with SCID and other primary immunodeficiencies who require BMT. Twenty-two of 73 (30%) such children were admitted with respiratory viral infections, of whom 13/22 (59%) died. All viruses were detected in nasopharyngeal aspirate (NPA). Virus was only found in BAL in those with LRTI. Eleven of 22 (50%) had paramyxovirus infections, all with severe viral pneumonitis which worsened post BMT. Five of 11 (45.5%) survived overall. All 11 received aerosolised ribavirin; five of 11 received additional inhaled immunoglobulin and corticosteroid. Three of 5 (60%) survived compared with two of six (33.3%) not thus treated. Three of 22 (13.6%) had adenoviruses; one died of disseminated disease, including pneumonia despite intravenous ribavirin. Eleven patients had rhinovirus detected; nine of 11 (82%) were asymptomatic or coryzal and survived. Two patients with additional severe lung pathologies had LRT rhinovirus and died. All patients received intravenous immunoglobulin. No treatments resulted in viral clearance without successful T cell engraftment. Respiratory viruses, particularly paramyxoviruses and adenoviruses are common, significant pathogens in these patients, significantly worsening outcome of BMT. NPA is an ideal specimen for diagnosis and monitoring of infection. Aggressive treatments may reduce viral replication and damage. Nebulised immunoglobulin and corticosteroid in LRTI may improve respiratory function and outcome.

Umbilical cord blood transplantation in severe T-cell immunodeficiency disorders: two-year experience

Hematopoietic stem cell transplantation is the treatment of choice for severe primary T-cell immunodeficiencies. When an HLA-identical sibling as the donor is not available, an alternative donor stem cell source is needed. In primary T-cell immunodeficiencies, T-cell-depleted HLA-haploidentical bone marrow transplantation has been particularly successful in reconstituting the immune system in many but not all of the severe T-cell immune deficiency disorders. This study reports the use of umbilical cord blood (UCB) stem cell transplantation in severe T-cell immune deficiency. Umbilical cord blood was evaluated as a stem cell source for immune reconstitution in children with severe primary T-cell immunodeficiency disorders, such as severe combined immunodeficiency syndrome (SCID), reticular dysgenesis, thymic dysplasia, combined immunodeficiency disease (CID), and Wiskott-Aldrich syndrome (WAS) when a matched sibling donor was unavailable. From 1/96 through 5/98, eight children received unrelated cord blood stem cell transplantation following a preparative regimen for the treatment of combined immunodeficiency diseases. The patients ranged in age from 2 weeks to 8 years. The cord blood units were 3/6 HLA antigen matches in two children. 4/6 in four children, and 5/6 in two child, with molecular HLA-DR mismatch in three of the children. The average time for neutrophil engraftment (absolute neutrophil count >500/mm3) was 12 days (range 10-15 days) and the average time for platelet engraftment (platelet count >20,000/mm3) was 36 days (range 24-50 days). A patient with reticular dysgenesis failed to engraft following her first transplant, but fully engrafted after a second unrelated donor cord blood transplantation. Five of six patients exhibited grade I graft-versus-host disease (GvHD). while one child had grade IV skin and gut GvHD. Immunologic reconstitution demonstrated that cord blood stem cell transplantation resulted in consistent and stable T-, B- and natural killer (NK) cell development. The kinetics of development were such that T-cell development occurred between 60 to 100 days. Initial T-cell engraftment consisted predominantly of CD45RO+, CD3+, and CD4+ T cells, and at 12 to 24 months changed to CD45RA+, CD3+, and CD4+ T cells, indicating de novo maturation of T cells. NK cell development occurred at approximately 180 days. B cells engrafted early, and study of functional B-cell antibody responses revealed that five of six patients in whom intravenous immune globulin has been discontinued have low detectable antibody responses to tetanus and diphtheria toxoid immunizations at 18 to 24 months posttransplantation. Unrelated umbilical donor cord blood is an alternative source of stem cells for transplantation in children with severe T-cell immune deficiency disorders when a suitable HLA-matched donor is not available and when a T-depleted haploidentical preparation is not beneficial. Benefits of UCB include rapid and reliable recovery of immune function, low risk of GvHD, and low viral transmission rate.

A practical approach to evaluating and treating neutropenia in the neonatal intensive care unit

Neutropenia is a relatively common problem in the NICU, recognized in as many as 8% of patients at some time during their hospital stay. In most instances, neutropenia among NICU patients is of short duration and has little influence on outcome. In other cases it is prolonged and severe, and constitutes a serious antimicrobial defense deficiency. When a neonatologist discovers a low blood neutrophil count, choices must be made regarding further evaluation and treatment. The authors hope that the information provided in this article is useful in making these choices.

Nonmyeloablative stem cell transplantation for congenital immunodeficiencies

The optimal approach for stem cell transplantation in children with immunodeficiency has yet to be determined. Conditioning therapy is necessary for reliable engraftment and full immune reconstitution; however, the beneficial effect of cytoreductive conditioning is counterbalanced by increased short- and long-term treatment-related toxicity. Whether bone marrow transplantation with a nonmyeloablative preparative regimen was sufficient for the establishment of donor immune reconstitution, with the resultant correction of disease phenotype, was investigated. Eight patients with severe immunodeficiency states underwent T-cell replete bone marrow transplantation from a human leukocyte antigen-matched unrelated (n = 6) or sibling (n = 2) donor with nonmyeloablative conditioning using a fludarabine–melphalan–anti-lymphocyte globulin-based regimen. All patients had severe organ dysfunction that precluded transplantation with conventional conditioning. All patients were engrafted with predominantly donor hematopoiesis, and the duration of neutropenia was brief. Significant acute graft-versus-host disease (GVHD) did not develop, but one patient had limited chronic GVHD. One patient died of disease recurrence, and 3 have stable, mixed chimerism. At a median follow-up of 1 year, all patients have had good recovery of CD3+ T-cell numbers, and 6 of 7 evaluable patients have normal phytohemagglutinin stimulation indices. The rate of immune reconstitution is comparable with that of historical controls undergoing standard myeloablative protocols. Two patients with CD40 ligand deficiency now show significant expression, and a patient with adenosine deaminase deficiency has improved deoxy adenosine triphosphate metabolites. In summary, it has been demonstrated that nonmyeloablative stem cell transplantation permits rapid engraftment from both sibling and unrelated donors with minimal toxicity even in the presence of severe organ dysfunction. If long-term immune reconstitution of patients treated with this protocol is demonstrated, it is believed this approach might offer significant advantages compared with standard protocols by combining adequate immune reconstitution with reduced short- and long-term toxicity.

Nonmyeloablative stem cell transplantation for congenital immunodeficiencies

The optimal approach for stem cell transplantation in children with immunodeficiency has yet to be determined. Conditioning therapy is necessary for reliable engraftment and full immune reconstitution; however, the beneficial effect of cytoreductive conditioning is counterbalanced by increased short- and long-term treatment-related toxicity. Whether bone marrow transplantation with a nonmyeloablative preparative regimen was sufficient for the establishment of donor immune reconstitution, with the resultant correction of disease phenotype, was investigated. Eight patients with severe immunodeficiency states underwent T-cell replete bone marrow transplantation from a human leukocyte antigen-matched unrelated (n = 6) or sibling (n = 2) donor with nonmyeloablative conditioning using a fludarabine–melphalan–anti-lymphocyte globulin-based regimen. All patients had severe organ dysfunction that precluded transplantation with conventional conditioning. All patients were engrafted with predominantly donor hematopoiesis, and the duration of neutropenia was brief. Significant acute graft-versus-host disease (GVHD) did not develop, but one patient had limited chronic GVHD. One patient died of disease recurrence, and 3 have stable, mixed chimerism. At a median follow-up of 1 year, all patients have had good recovery of CD3+ T-cell numbers, and 6 of 7 evaluable patients have normal phytohemagglutinin stimulation indices. The rate of immune reconstitution is comparable with that of historical controls undergoing standard myeloablative protocols. Two patients with CD40 ligand deficiency now show significant expression, and a patient with adenosine deaminase deficiency has improved deoxy adenosine triphosphate metabolites. In summary, it has been demonstrated that nonmyeloablative stem cell transplantation permits rapid engraftment from both sibling and unrelated donors with minimal toxicity even in the presence of severe organ dysfunction. If long-term immune reconstitution of patients treated with this protocol is demonstrated, it is believed this approach might offer significant advantages compared with standard protocols by combining adequate immune reconstitution with reduced short- and long-term toxicity.

Retrovirus-mediated transduction of primary ZAP-70-deficient human T cells results in the selective growth advantage of gene-corrected cells: implications for gene therapy

Humans lacking the ZAP-70 protein tyrosine kinase present with an absence of CD8+ T cells and defective CD4+ T cells in the periphery. This severe combined immunodeficiency is fatal unless treated by allogeneic bone marrow transplantation. However, in the absence of suitable marrow donors, the development of alternative forms of therapy is desirable. Because lymphocytes are long-lived, it is possible that introduction of the wild-type ZAP-70 gene into CD4+ ZAP-70-deficient T cells will restore their immune function in vivo. Initial investigations evaluating the feasibility of gene therapy for ZAP-70 deficiency were performed using HTL V-I-transformed lymphocytes. Although transformation was useful in circumventing problems associated with the maintenance of ZAP-70-deficient T cells and low gene transfer levels, the presence of HTL V-I precluded any biological studies. Here, we investigated a retrovirus-mediated approach for the correction of primary T cells derived from two ZAP-70-deficient patients. Upon introduction of the wild-type ZAP-70 gene, TCR-induced MAPK activation, IL-2 secretion and proliferation were restored to approximately normal levels. Importantly, this gain-of-function was associated with a selective growth advantage of gene-corrected cells, thereby indicating the feasibility of a gene therapy-based strategy.

Association of natural killer cell depletion with induction of mixed chimerism and allograft tolerance in non-human primates

BACKGROUND

Nonmyeloablative T cell depletion followed by donor bone marrow infusion has proved to be an effective approach to induction of mixed chimerism and tolerance of organ allografts in non-human primates. To help define the mechanisms involved we have compared T cell depletion with ATG versus anti-CD2 monoclonal antibody with respect to establishment of mixed chimerism and induction of tolerance.

METHOD

Both nonmyeloablative regimens included low dose total body irradiation (1.5 Gy x 2), thymic irradiation (7 Gy), splenectomy and kidney plus donor bone marrow transplantation, followed by a 4-week posttransplant course of cyclosporine. In addition, the ATG group (13 recipients) received antithymocyte globulin, although the LOCD2b group (10 recipients) were treated with an anti-CD2 monoclonal antibody (LOCD2b).

RESULTS

In the ATG group, 11 of 13 monkeys developed multilineage chimerism and 9 survived for more than 100 days without kidney allograft rejection. In contrast, 0/10 monkeys in the LOCD2b group developed chimerism, 5 died of infection and 5 suffered progressive rejection; only 1 recipient survived beyond 100 days. Sequential monitoring of peripheral blood mononuclear cells revealed greater T cell (CD3+) depletion in the LOCD2b-treated animals compared to those receiving ATG. However, NK cells (CD16+CD8+) were significantly more depleted in the ATG group and NK function remained abrogated longer after ATG than LOCD2b treatment (3 weeks vs. <5 days).

CONCLUSION

Despite excellent T cell depletion by LoCD2b, ATG was more effective in inducing chimerism and tolerance. This difference correlated with anti-NK activity of the two reagents. These data suggest that NK cells may also resist engraftment of allogeneic bone marrow cells in this model.

In vitro and in vivo studies with human carrier erythrocytes loaded with polyethylene glycol-conjugated and native adenosine deaminase

Polyethylene glycol-conjugated adenosine deaminase (pegademase) is used for enzyme replacement therapy for patients with severe combined immunodeficiency caused by adenosine deaminase deficiency. The entrapment of pegademase within human energy-replete carrier erythrocytes using a hypo-osmotic dialysis procedure was investigated with the objective of prolonging the in vivo circulatory half-life of the enzyme and maintaining therapeutic blood levels. Native unmodified adenosine deaminase (ADA) was similarly studied. The efficiency of pegademase entrapment was low (9%) whereas the entrapment of native unmodified ADA was substantial (50%), suggesting that the polyethylene glycol side-chains were impeding intracellular entrapment. The biochemical characteristics and the osmotic fragility of these carrier erythrocytes were not adversely affected by the entrapment of either pegademase or native ADA. In vivo survival studies of pegademase-loaded 51Cr-labelled carrier erythrocytes in an ADA-deficient adult patient showed a mean cell half-life of 16 d. Carrier erythrocyte-entrapped pegademase and native ADA had in vivo half-lives of 20 and 12.5 d, respectively, demonstrating that entrapment prolongs the half-life over that of plasma pegademase, which has a circulating half-life of 3-6 d. These results provide the basis for a more extensive clinical evaluation of carrier erythrocyte-entrapped native adenosine deaminase therapy.

Disseminated BCG infection following bone marrow transplantation for X-linked severe combined immunodeficiency

An 8-month-old boy with X-linked severe combined immunodeficiency (XSCID) developed disseminated bacille Calmette-Guerin (BCG) infection following BCG vaccination at birth. He initially presented with an abscess at the site of BCG vaccination and was begun on three-drug antituberculous treatment (rifampicin, isoniazid, and pyrazinimide). Dissemination was subclinical prior to a human leukocyte antigen (HLA)-identical bone marrow transplant (BMT) from his sister, following which he presented with an acute erythroderma. A skin biopsy specimen revealed granulomas with epithelial histiocytes and giant cells in the reticular dermis, and numerous acid-fast bacilli (AFB) were present on Ziehl-Nielsen stain. A diagnosis of disseminated BCG disease was made. Despite the addition of a fourth antituberculous agent, ethambutol, he did not recover and developed numerous skin abscesses over the following weeks. Examination of pus from these lesions demonstrated numerous AFB. Clarithromycin was added as a fifth antituberculous agent. Despite five-drug antituberculous therapy and monthly intravenous immunoglobulin infusions, recurrent abscesses containing AFB developed intermittently until 7 months posttransplant. At follow-up 1 year post-BMT he showed good general physical improvement. All abscesses had healed with scarring, and no further skin lesions had occurred.

Matched unrelated bone marrow transplantation for combined immunodeficiency

Bone marrow transplantation (BMT) from siblings is the treatment of choice for severe combined immunodeficiency (SCID). The objective of this study was to evaluate the efficiency of BMT from matched unrelated donors (MUD) in congenital immunodeficiencies when a sibling donor is unavailable. Sixteen consecutive patients with SCID (n = 9) and CID (n= 7), were referred for an unrelated donor search. Acceptable donors were found for all patients. Fifteen patients received busulfan and cyclophosphamide pretransplant conditioning. One patient had an early loss of graft and was reconditioned using cyclophosphamide and total body irradiation. The graft-versus-host disease (GVHD) prophylaxis used was methylprednisolone, cyclosporin A with or without methotrexate. Neutrophil engraftment was rapid and was achieved in all patients within a mean of 15.4 days. Only 13 episodes of fever were recorded shortly after BMT. GVHD of grade II or more was apparent in 2/9 (22%) of SCID patients and in 4/7 (57%) of CID patients. Overall survival was 75% with a mean follow-up of 47.4 months (range 18-101). Six out of nine SCID patients (67%) and 6/7 (86%) of CID patients are alive and well. Eleven patients had normal humoral immunity, and cell-mediated immunity as measured by flow cytometry and mitogenic responses, was intact in all patients. Intradermal candida skin test was positive in 9/10 patients tested. We conclude that BMT from MUD results in rapid engraftment and is therefore associated with a low rate of infection contributing to the improved survival rate. The protocol used is especially favorable for patients with combined immunodeficiency.

Unsuspected Pneumocystis carinii pneumonia at presentation of severe primary immunodeficiency

BACKGROUND

Pneumocystis carinii is an important pathogen in immunodeficiency but may be an unrecognised cause of respiratory compromise.

OBJECTIVES

To ascertain the incidence of P carinii pneumonia (PCP) at presentation of severe combined immunodeficiency (SCID), whether it had been diagnosed, and the effect of treatment on outcome.

SETTING

The supraregional paediatric bone marrow transplant unit for primary immunodeficiencies at Newcastle General Hospital.

METHODS

Retrospective case note review of infants referred with a diagnosis of SCID from 1992 to 1998.

RESULTS

Ten of 50 infants had PCP at presentation; only one was diagnosed before transfer. Eight were diagnosed by bronchoalveolar lavage and two by lung biopsy. In only one was P carinii identified in nasopharyngeal secretions. Five required ventilation for respiratory failure but all were successfully treated with co-trimoxazole and methylprednisolone with or without nebulised budesonide. Nine survived to bone marrow transplantation and four are long term survivors after bone marrow transplantation; no deaths were related to PCP.

CONCLUSIONS

PCP is a common presenting feature of SCID but is rarely recognised. Bronchoalveolar lavage or lung biopsy are needed for diagnosis. Treatment with co-trimoxazole is highly successful.

Long-Term Chimerism and B-Cell Function After Bone Marrow Transplantation in Patients With Severe Combined Immunodeficiency With B Cells: A Single-Center Study of 22 Patients

We retrospectively analyzed the B-cell function and leukocyte chimerism of 22 patients with severe combined immunodeficiency with B cells (B+ SCID) who survived more than 2 years after bone marrow transplantation (BMT) to determine the possible consequences of BMT procedures, leukocyte chimerism, and SCID molecular deficit on B-cell function outcome. Circulating T cells were of donor origin in all patients. In recipients of HLA-identical BMT (n = 5), monocytes were of host origin in 5 and B cells were of host origin in 4 and of mixed origin in 1. In recipients of HLA haploidentical T-cell–depleted BMT (n = 17), B cells and monocytes were of host origin in 14 and of donor origin in 3. Engraftment of B cells was found to be associated with normal B-cell function. In contrast, 10 of 18 patients with host B cells still require Ig substitution. Conditioning regimen (ie, 8 mg/kg busulfan and 200 mg/kg cyclophosphamide) was shown neither to promote B-cell and monocyte engraftment nor to affect B-cell function. Eight patients with B cells of host origin had normal B-cell function. Evidence for functional host B cells was further provided in 3 informative cases by Ig allotype determination and by the detection, in 5 studied cases, of host CD27+ memory B cells as in age-matched controls. These results strongly suggest that, in some transplanted patients, host B cells can cooperate with donor T cells to fully mature in Ig-producing cells.