Thymic output, T-cell diversity, and T-cell function in long-term human SCID chimeras

Ex vivo and in vivo T-cell depletion in allogeneic transplantation: towards less or non-cytotoxic conditioning regimens

INTRODUCTION

Although tremendous progress has been made since the introduction of allogeneic hematopoietic stem cell transplantation (HSCT) decades ago, there are still many obstacles to overcome. A major obstacle is the presence of T-lymphocytes in the recipient and in the donor. Recipient-derived T-lymphocytes not eliminated by the conditioning regimen are a major barrier and can lead to mixed chimerism or to complete rejection of the graft. Donor-derived T-lymphocytes can induce severe acute and chronic Graft-versus-Host Disease (GvHD).

AREAS COVERED

Currently published strategies for in vivo depletion of recipient-derived T-lymphocytes are discussed including the increase of the intensity of the conditioning regimen, the addition of anti-thymocyte globulin (ATG) or the anti-CD52 monoclonal antibody Campath. For the depletion or tolerization of the donor-derived T-lymphocytes, ex vivo-T-cell depletion methods, such as positive selection of CD34+ stem cells, negative depletion of CD3+ or TcRαβ+ T-lymphocytes or the use of post-transplant cyclophosphamide (PTCy) have been developed.

EXPERT COMMENTARY

All these currently used approaches have their disadvantages and new approaches should be investigated. In this review, we discuss current and propose new possible strategies to overcome the HLA barrier by using more specific T-cell directed therapies and/or by the combinations of current methods.

T and NK Cells in IL2RG-Deficient Patient 50 Years After Hematopoietic Stem Cell Transplantation

The first successful European hematopoietic stem cell transplantation (HSCT) was performed in 1968 as treatment in a newborn with IL2RG deficiency using an HLA-identical sibling donor. Because of declining naive T and natural killer (NK) cells, and persistent human papilloma virus (HPV)-induced warts, the patient received a peripheral stem cell boost at the age of 37 years. NK and T cells were assessed before and up to 14 years after the boost by flow cytometry. The boost induced renewed reconstitution of functional NK cells that were 14 years later enriched for CD56dimCD27+ NK cells. T-cell phenotype and T-cell receptor (TCR) repertoire were simultaneously analyzed by including TCR Vβ antibodies in the cytometry panel. Naive T-cell numbers with a diverse TCR Vβ repertoire were increased by the boost. Before and after the boost, clonal expansions with a homogeneous TIGIT and PD-1 phenotype were identified in the CD27− and/or CD28− memory population in the patient, but not in the donor. TRB sequencing was applied on sorted T-cell subsets from blood and on T cells from skin biopsies. Abundant circulating CD8 memory clonotypes with a chronic virus-associated CD57+KLRG1+CX3CR1+ phenotype were also present in warts, but not in healthy skin of the patient, suggesting a link with HPV. In conclusion, we demonstrate in this IL2RG-deficient patient functional NK cells, a diverse and lasting naive T-cell compartment, supported by a stem cell boost, and an oligoclonal memory compartment half a century after HSCT.

Historical perspective and a glance into the antibody-based conditioning regimens: A new era in the horizon?

The hematopoietic cell transplantation practice has changed significantly over the years. More than 1500 centers around the globe are offering transplant for different types of diseases. This growth was driven by improving the efficacy and the safety of the procedure and the ability to use alternate donors. These improvements made the procedure feasible in virtually all patients in need for it. With the availability of novel therapies and targeted agents, we may be witnessing a new transplant-era. These agents may help to circumvent some of the remaining limitations of the procedure and open the doors for new indications. Herein, we review historical transplant milestones, the accomplishments that led to the modern transplant practice and we discuss the idea of minimal-intensity conditioning and the possibility to adopt chemotherapy and radiation-free preparative regimens in the near future.

Matched versus Haploidentical Hematopoietic Stem Cell Transplantation as Treatment Options for Primary Immunodeficiencies in Children

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system with allogeneic hematopoietic stem cell transplantation (HSCT) as the only curative treatment in some of them. In case an HLA-matched donor is not available, HSCT from a haploidentical family donor may be considered. We compared the outcomes of HSCT from HLA-matched unrelated or related donors (MUDs or MRDs) and mismatched related haploidentical donors (MMRDs) in patients with a variety of PIDs in 2 centers. A total of 44 pediatric patients were evaluated. We reviewed the outcomes of 25 children who underwent transplantation with HLA-matched grafts (MRD, n = 13; MUD, n = 12) and 19 patients receiving haploidentical stem cells. Bone marrow (BM) was transplanted in 85% (MRD) and 75% (MUD) of the matched cohort and peripheral blood stem cells (PBSCs) in 15% (MRD), 25% (MUD), and 100% (MMRD). All but 9 patients (MRD, n = 6; MMRD, n = 3) with severe combined immunodeficiency (SCID) received a chemotherapy-based conditioning regimen. Immune reconstitution of T, B, and natural killer cells was comparable for all groups with an advantage of recipients of MRD grafts in early CD4 reconstitution. However, deaths due to viral infections occurred more often in the haploidentical cohort. The disease-free survival was 91.7% (MRD), 66.7% (MUD), and 62.7% (MMRD), respectively. Grade II to IV acute graft-versus-host disease (GVHD) occurred in 15% (MRD), 8% (MUD), and 21% (MMRD) of the patients. Only 1 patient had severe grade IV GVHD in the MRD group, whereas no grade >II GVHD was observed in the MUD or MMRD cohort. These data indicate that in the absence of a suitable HLA-identical family donor, haploidentical HSCT may be a viable option for patients with life-threatening disease and urgent need of HSCT.

Now Is the Time to Use Molecular Gene Testing for the Diagnosis of Primary Immune Deficiencies

The discovery of chromosomes, genes, and DNA in the early 20th century paved the way for the development of techniques to examine the role of these elements in disease pathogenesis. Since the start of the 21st century, genetic testing and particularly next-generation sequencing has allowed for a rapid rate of gene disease associations for a broad range of primary immunodeficiency patients. At the same time, biologic and small molecule-based therapies targeting specific molecular pathways have been developed and are being applied clinically and in research settings to treat genetically defined immunodeficiencies. In recent years, both the American Academy of Allergy Asthma and Immunology and the Clinical Immunology Society have recommended the use of genetic testing for diagnosis, therapy guidance, and genetic counseling in patients with clinical symptoms of primary immunodeficiency.

Long Term Outcome and Immune Function After Hematopoietic Stem Cell Transplantation for Primary Immunodeficiency

Transplantation techniques for patients with primary immunodeficiencies have improved so that survival from the procedure in many cases is >80%. However, long term complications may arise due to the use or not of conditioning agents. This may result in variable immune reconstitution, the long term effects of chemotherapy, particularly on fertility, and complications relating to the genetic disorder, unresolved by transplantation. For patients with severe combined immunodeficiency (SCID), long term T- and B-lymphocyte immune reconstitution is best achieved after pre-transplant chemotherapy. For patients who receive an unconditioned infusion of donor stem cells, the quality of immune reconstitution depends on the SCID genotype. Long term effects include chemotherapy-induced impaired fertility, and sequelae specific to the genotype. For patients with other primary immunodeficiencies, conditioning is required-sequelae related to direct effects of chemotherapy may be observed. Additional long term effects may be observed due to partial donor chimerism resulting in incomplete eradication of disease, and other geno-specific effects.

Update on Advances in Hematopoietic Cell Transplantation for Primary Immunodeficiency Disorders

Hematopoietic stem cell transplantation (HSCT) in patients with primary immunodeficiency disorders (PIDDs) is being increasingly used as a curative option. Understanding the critical components, such as disease's nature and activity and pre-HSCT and post-HSCT patient care is key to a successful outcome. HSCT should be tailored to the underlying PIDD, as different PIDDs, such as severe combined immune deficiency, Treg dysfunction, and phagocytic disorders, have different transplant approaches. Therefore, successful HSCT in patients with PIDDs requires teamwork between immunologists and transplant physicians. In this article, the authors elaborate on various aspects of PIDD-HSCT and highlight recent advances.

Long-Term Health Outcome and Quality of Life Post-HSCT for IL7Rα-, Artemis-, RAG1- and RAG2-Deficient Severe Combined Immunodeficiency: a Single Center Report

Hematopoietic stem cell transplantation (HSCT) is curative for severe combined immunodeficiency (SCID), but data on long-term impact of pre-HSCT chemotherapy, immune reconstitution and quality of life (QoL) of specific SCID genotypes are limited. We evaluated the long-term immune-reconstitution, health outcome and QoL in IL7Rα SCID, Artemis and RAG1 and 2 SCID survivors > 2 years post-HSCT in our center. Clinical data and immune reconstitution parameters were collated, and patients/families answered PedsQL generic core scale v4.0 questionnaires. Thirty-nine patients with a diagnosis of IL7Rα SCID (17 patients), Artemis SCID (8 patients) and RAG1/2 SCID (13 patients) had undergone HSCT with median age at last follow up for IL7Rα SCID, 14 years (range 4-27) and Artemis and RAG1/2 SCID, 10 years (range 2-18). Many patients have ongoing medical issues at latest follow-up [IL7Rα (73%), Artemis (85%), RAG1/2 (55%)]. Artemis SCID patients experienced more sequela than RAG1/2 SCID. Conditioned recipients with Artemis and RAG SCID had more CD4+ naïve lymphocytes compared to unconditioned recipients. All patients except those of IL7Rα SCID reported lower QoL; further subset group analysis showed parents and Artemis and RAG1/2 survivors without ongoing medical issues reported normal QoL. Conditioned recipients have superior long-term thymopoiesis, chimerism and immunoglobulin-independence. QoL was normal in those who did not have medical issues at long-term follow-up.

Use of Genetic Testing for Primary Immunodeficiency Patients

Genetic testing plays a critical role in diagnosis for many primary immunodeficiency diseases. The goals of this report are to outline some of the challenges that clinical immunologists face routinely in the use of genetic testing for patient care. In addition, we provide a review of the types of genetic testing used in the diagnosis of PID, including their strengths and limitations. We describe the strengths and limitations of different genetic testing approaches for specific clinical contexts that raise concern for specific PID disorders in light of the challenges reported by the clinical immunologist members of the CIS in a recent membership survey. Finally, we delineate the CIS's recommendations for the use of genetic testing in light of these issues.

Long term outcomes of severe combined immunodeficiency: therapy implications

INTRODUCTION

Newborn screening has led to a better understanding of the prevalence of Severe Combined Immunodeficiency (SCID) overall and in terms of specific genotypes. Survival has improved following hematopoietic stem cell transplantation (HCT) with the best outcomes seen following use of a matched sibling donor. However, questions remain regarding the optimal alternative donor source, appropriate use of conditioning and the impact of these decisions on immune reconstitution and other late morbidities. Areas covered: The currently available literature reporting late effects after HCT for SCID and use of alternative therapies including enzyme replacement, alternative donors and gene therapy are reviewed. A literature search was performed on Pubmed and ClinicalTrials.gov using key words 'Severe Combined Immunodeficiency', 'SCID', 'hematopoietic stem cell transplant', 'conditioning', 'gene therapy', 'SCID newborn screening', 'TREC' and 'late effects'. Expert commentary: Newborn screening has dramatically changed the clinical presentation of newborn SCID. While the majority of patients with SCID survive HCT, data regarding late effects in these patients is limited and additional studies focused on genotype specific late effects are needed. Prospective studies aimed at minimizing the use of alkylating agents and reducing late effects beyond survival are needed. Gene therapy is being developed and will likely become a more commonly used treatment that will require separate consideration of survival and late effects.

Defective thymic output in WAS patients is associated with abnormal actin organization

Wiskott-Aldrich syndrome protein (WASp) is a key regulator of the actin cytoskeleton. Defective T - cell function is a major cause for immune deficiency in Wiskott-Aldrich syndrome (WAS) patients. T cells originate in the bone marrow and develop in the thymus, and then migrate to peripheral tissues. TCR excision circles (TRECs) present in thymic output cells stably, which is used as a molecular marker for thymic output. We found that CD8⁺ T naïve cells of classic WAS patients were significantly reduced, and TRECs in patients with classic WAS and X-linked thrombocytopenia (XLT) dramatically decreased compared with that of HCs. TRECs were also reduced in WAS (KO) mice. These suggest that defective thymic output partially accounts for T cell lymphopenia in WAS patients. However, the correlation between the defect of thymic output and actin organization still remains elusive. We found that the subcellular location and the levels of of F-actin were altered in T cells from both WAS and XLT patients compared to that of HCs with or without stimulation. Our study shows that WASp plays a critical role in thymic output, which highly correlates with the subcellular location and level of F-actin in T cells.

Haematopoietic stem cell transplantation for severe combined immunodeficiency: Long-term health outcomes and patient perspectives

AIM

To examine the long-term follow-up and health outcomes of patients who have undergone haematopoietic stem cell transplant (HSCT) for severe combined immunodeficiency (SCID).

METHODS

Through a structured questionnaire, we examined follow-up arrangements and long-term health outcomes in 22 children who have had a successful HSCT for SCID during the period of 1984-2012 at the Sydney Children's Hospital, Sydney, Australia.

RESULTS

Most children considered themselves healthy and 'cured' from SCID. Whilst many children enjoy relatively good bio-social health outcomes, specific negative health outcomes and absenteeism from school were perceived negatively. Two-thirds of children see their general practitioner or specialist regularly; however, there did not appear to be consistency with the nature of this follow-up.

CONCLUSION

The findings from our study highlight the complex bio-psychosocial health needs of post-HSCT SCID children and encourage SCID centres to consider a multidisciplinary approach to their follow-up. Further studies into the determinants of patients' perceptions of their health are needed.

Recommendations for Screening and Management of Late Effects in Patients with Severe Combined Immunodeficiency after Allogenic Hematopoietic Cell Transplantation: A Consensus Statement from the Second Pediatric Blood and Marrow Transplant Consortium International Conference on Late Effects after Pediatric HCT

Severe combined immunodeficiency (SCID) is effectively treated with hematopoietic cell transplantation (HCT), with overall survival approaching 90% in contemporary reports. However, survivors are at risk for developing late complications because of the variable durability of high-quality immune function, underlying genotype of SCID, comorbidities due to infections in the pretransplantation and post-transplantation periods, and use of conditioning before transplantation. An international group of transplantation experts was convened in 2016 to review the current knowledge of late effects seen in SCID patients after HCT and to develop recommendations for screening and monitoring for late effects. This report provides recommendations for screening and management of pediatric and adult SCID patients treated with HCT.

Clonal and constricted T cell repertoire in Common Variable Immune Deficiency

We used high throughput sequencing to examine the structure and composition of the T cell receptor β chain in Common Variable Immune Deficiency (CVID). TCRβ CDR3 regions were amplified and sequenced from genomic DNA of 44 adult CVID subjects and 22 healthy adults, using a high-throughput multiplex PCR. CVID TCRs had significantly less junctional diversity, fewer n-nucleotide insertions and deletions, and completely lacked a population of highly modified TCRs, with 13 or more V-gene nucleotide deletions, seen in healthy controls. The CVID CDR3 sequences were significantly more clonal than control DNA, and displayed unique V gene usage. Despite reduced junctional diversity, increased clonality and similar infectious exposures, DNA of CVID subjects shared fewer TCR sequences as compared to controls. These abnormalities are pervasive, found in out-of-frame sequences and thus independent of selection and were not associated with specific clinical complications. These data support an inherent T cell defect in CVID.

Current Knowledge and Priorities for Future Research in Late Effects after Hematopoietic Stem Cell Transplantation (HCT) for Severe Combined Immunodeficiency Patients: A Consensus Statement from the Second Pediatric Blood and Marrow Transplant Consortium International Conference on Late Effects after Pediatric HCT

Severe combined immunodeficiency (SCID) is 1 of the most common indications for pediatric hematopoietic cell transplantation (HCT) in patients with primary immunodeficiency. Historically, SCID was diagnosed in infants who presented with opportunistic infections within the first year of life. With newborn screening (NBS) for SCID in most of the United States, the majority of infants with SCID are now diagnosed and treated in the first 3.5 months of life; however, in the rest of the world, the lack of NBS means that most infants with SCID still present with infections. The average survival for SCID patients who have undergone transplantation currently is >70% at 3 years after transplantation, although this can vary significantly based on multiple factors, including age and infection status at the time of transplantation, type of donor source utilized, manipulation of graft before transplantation, graft-versus-host disease prophylaxis, type of conditioning (if any) utilized, and underlying genotype of SCID. In at least 1 study of SCID patients who received no conditioning, long-term survival was 77% at 8.7 years (range out to 26 years) after transplantation. Although a majority of patients with SCID will engraft T cells without any conditioning therapy, depending on genotype, donor source, HLA match, and presence of circulating maternal cells, a sizable percentage of these will fail to achieve full immune reconstitution. Without conditioning, T cell reconstitution typically occurs, although not always fully, whereas B cell engraftment does not, leaving some molecular types of SCID patients with intrinsically defective B cells, in most cases, dependent on regular infusions of immunoglobulin. Because of this, many centers have used conditioning with alkylating agents including busulfan or melphalan known to open marrow niches in attempts to achieve B cell reconstitution. Thus, it is imperative that we understand the potential late effects of these agents in this patient population. There are also nonimmunologic risks associated with HCT for SCID that appear to be dependent upon the genotype of the patient. In this report, we have evaluated the published data on late effects and attempted to summarize the known risks associated with conditioning and alternative donor sources. These data, while informative, are also a clear demonstration that there is still much to be learned from the SCID population in terms of their post-HCT outcomes. This paper will summarize current findings and recommend further research in areas considered high priority. Specific guidelines regarding a recommended approach to long-term follow-up, including laboratory and clinical monitoring, will be forthcoming in a subsequent paper.

Clinical and imaging considerations in primary immunodeficiency disorders: an update

Primary immunodeficiencies are a group of genetically determined disorders with diverse presentations. The purpose of this review is to provide a practical and brief description of a select number of these diseases and to discuss the important role the radiologist can have in making an early diagnosis and in detecting and following disease complications. The role of diagnostic imaging and informed performance and interpretation are vital in the diagnosis, surveillance and management of all primary immunodeficiency disorders.

Severe combined immunodeficiencies and related disorders

Severe combined immunodeficiencies (SCIDs) comprise a group of rare, monogenic diseases that are characterized by an early onset and a profound block in the development of T lymphocytes. Given that adaptive immunity is abrogated, patients with SCID are prone to recurrent infections caused by both non-opportunistic and opportunistic pathogens, leading to early death unless immunity can be restored. Several molecular defects causing SCIDs have been identified, along with many other defects causing profound, albeit incomplete, T cell immunodeficiencies; the latter are referred to as atypical SCIDs or combined immunodeficiencies. The pathophysiology of many of these conditions has now been characterized. Early, accurate and precise diagnosis combined with the ongoing implementation of newborn screening have enabled major advances in the care of infants with SCID, including better outcomes of allogeneic haematopoietic stem cell transplantation. Gene therapy is also becoming an effective option. Further advances and a progressive extension of the indications for gene therapy can be expected in the future. The assessment of long-term outcomes of patients with SCID is now a major challenge, with a view to evaluating the quality and sustainability of immune restoration, the risks of sequelae and the ability to relieve the non-haematopoietic syndromic manifestations that accompany some of these conditions.

High-throughput sequencing reveals an altered T cell repertoire in X-linked agammaglobulinemia

To examine the T cell receptor structure in the absence of B cells, the TCR β CDR3 was sequenced from DNA of 15 X-linked agammaglobulinemia (XLA) subjects and 18 male controls, using the Illumina HiSeq platform and the ImmunoSEQ analyzer. V gene usage and the V-J combinations, derived from both productive and non-productive sequences, were significantly different between XLA samples and controls. Although the CDR3 length was similar for XLA and control samples, the CDR3 region of the XLA T cell receptor contained significantly fewer deletions and insertions in V, D, and J gene segments, differences intrinsic to the V(D)J recombination process and not due to peripheral T cell selection. XLA CDR3s demonstrated fewer charged amino acid residues, more sharing of CDR3 sequences, and almost completely lacked a population of highly modified Vβ gene segments found in control DNA, suggesting both a skewed and contracted T cell repertoire in XLA.

A prospective outcome study of patients with profound combined immunodeficiency (P-CID)

This is a prospective outcome study of patients with profound combined immunodeficiency (P-CID) (study number DRKS00000497).

Combined immunodeficiencies (CID) are a heterogeneous group of inherited immune disorders with impaired T-cell development and (or) function manifesting through increased susceptibility to infections and (or) immune dysregulation. They can be delineated from severe CID (SCID) by their manifestation beyond the first year of life. Profound CID (P-CID) is a potentially life-threatening form of CID, in which stem cell transplant (SCT) is a relevant consideration at diagnosis.

The primary objective of the study is to provide natural history data on patients with P-CID, irrespective of whether they undergo hematopoietic stem cell transplant (HSCT) or not. The goals are to determine survival, the frequency of severe events, and quality of life (QOL) 5 years after study inclusion.

The secondary objective is to develop a risk model for P-CID patients. The model is developed from a set of clinical and laboratory parameters obtained at diagnosis, at study inclusion, and yearly thereafter.

The tertiary objectives of this study are to determine the effects of donor, recipient, and treatment factors on the outcome of HSCT. The goal is to determine the quality of engraftment and immunological reconstitution and to determine the effects of these parameters on clinical outcome.

The main hypothesis is that P-CID patients undergoing early HSCT have a better 5-year survival rate than patients who undergo late HSCT or are not transplanted.

This is a prospective multi-centre international cohort study (observational study).

Enrolled patients will be evaluated and treated according to local institutional protocols. They will receive comparable baseline and follow-up evaluations across all participating centres, irrespective of the therapeutic strategy at the individual site.

There will be at least 6 study visits (scheduled yearly) for all patients. Because of the variable history prior to study inclusion, a morbidity score is determined for each patient at study visit 1. For those patients undergoing HSCT, an additional 6 month post-HSCT visit will be scheduled. The study visits will document immunological parameters, severe events including major infections, and major manifestations of immune dysregulation, severe transplant-related events, and QOL.

Long-lasting production of new T and B cells and T-cell repertoire diversity in patients with primary immunodeficiency who had undergone stem cell transplantation: a single-centre experience

Levels of Kappa-deleting recombination excision circles (KRECs), T-cell receptor excision circles (TRECs), and T-cell repertoire diversity were evaluated in 1038 samples of 124 children with primary immunodeficiency, of whom 102 (54 with severe combined immunodeficiency and 48 with other types of immunodeficiency) underwent hematopoietic stem cell transplantation. Twenty-two not transplanted patients with primary immunodeficiency were used as controls. Only data of patients from whom at least five samples were sent to the clinical laboratory for routine monitoring of lymphocyte reconstitutions were included in the analysis. The mean time of the follow-up was 8 years. The long-lasting posttransplantation kinetics of KREC and TREC production occurred similarly in patients with severe combined immunodeficiency and with other types of immunodeficiency and, in both groups, the T-cell reconstitution was more efficient than in nontransplanted children. Although thymic output decreased in older transplanted patients, the degree of T-cell repertoire diversity, after an initial increase, remained stable during the observation period. However, the presence of graft-versus-host disease and ablative conditioning seemed to play a role in the time-related shaping of T-cell repertoire. Overall, our data suggest that long-term B- and T-cell reconstitution was equally achieved in children with severe combined immunodeficiency and with other types of primary immunodeficiency.

Comparison of outcomes of hematopoietic stem cell transplantation without chemotherapy conditioning by using matched sibling and unrelated donors for treatment of severe combined immunodeficiency

BACKGROUND

Patients with severe combined immunodeficiency disease who have matched sibling donors (MSDs) can proceed to hematopoietic cell transplantation (HCT) without conditioning chemotherapy.

OBJECTIVE

We sought to determine whether the results of HCT without chemotherapy-based conditioning from matched unrelated donors (URDs), either from volunteer adults or umbilical cord blood, are comparable with those from MSDs.

METHODS

We performed a multicenter survey of severe combined immunodeficiency transplantation centers in North America, Europe, and Australia to compile retrospective data on patients who have undergone unconditioned HCT from either URDs (n = 37) or MSDs (n = 66).

RESULTS

Most patients undergoing URD HCT (92%) achieved donor T-cell engraftment compared with 97% for those with MSDs; however, estimated 5-year overall and event-free survival were worse for URD recipients (71% and 60%, respectively) compared with MSD recipients (92% and 89%, respectively; P < .01 for both). URD recipients who received pre-HCT serotherapy had similar 5-year overall survival (100%) to MSD recipients. The incidences of grade II to IV acute and chronic graft-versus-host disease were higher in URD (50% and 39%, respectively) compared with MSD (22% and 5%, respectively) recipients (P < .01 for both). In the surviving patients there was no difference in T-cell reconstitution at the last follow-up between the URD and MSD recipients; however, MSD recipients were more likely to achieve B-cell reconstitution (72% vs 17%, P < .001).

CONCLUSION

Unconditioned URD HCT achieves excellent rates of donor T-cell engraftment similar to that seen in MSD recipients, and reconstitution rates are adequate. However, only a minority will have myeloid and B-cell reconstitution, and attention must be paid to graft-versus-host disease prophylaxis. This approach might be safer in children ineligible for intense regimens to spare the potential complications of chemotherapy.

Transplantation outcomes for severe combined immunodeficiency, 2000-2009

BACKGROUND

The Primary Immune Deficiency Treatment Consortium was formed to analyze the results of hematopoietic-cell transplantation in children with severe combined immunodeficiency (SCID) and other primary immunodeficiencies. Factors associated with a good transplantation outcome need to be identified in order to design safer and more effective curative therapy, particularly for children with SCID diagnosed at birth.

METHODS

We collected data retrospectively from 240 infants with SCID who had received transplants at 25 centers during a 10-year period (2000 through 2009).

RESULTS

Survival at 5 years, freedom from immunoglobulin substitution, and CD3+ T-cell and IgA recovery were more likely among recipients of grafts from matched sibling donors than among recipients of grafts from alternative donors. However, the survival rate was high regardless of donor type among infants who received transplants at 3.5 months of age or younger (94%) and among older infants without prior infection (90%) or with infection that had resolved (82%). Among actively infected infants without a matched sibling donor, survival was best among recipients of haploidentical T-cell-depleted transplants in the absence of any pretransplantation conditioning. Among survivors, reduced-intensity or myeloablative pretransplantation conditioning was associated with an increased likelihood of a CD3+ T-cell count of more than 1000 per cubic millimeter, freedom from immunoglobulin substitution, and IgA recovery but did not significantly affect CD4+ T-cell recovery or recovery of phytohemagglutinin-induced T-cell proliferation. The genetic subtype of SCID affected the quality of CD3+ T-cell recovery but not survival.

CONCLUSIONS

Transplants from donors other than matched siblings were associated with excellent survival among infants with SCID identified before the onset of infection. All available graft sources are expected to lead to excellent survival among asymptomatic infants. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

How I treat severe combined immunodeficiency

Severe combined immunodeficiency (SCID) arises from different genetic defects associated with lymphocyte development and function and presents with severe infections. Allogeneic hematopoietic stem cell transplantation is an extremely effective way of restoring immunity in these individuals. Numerous multicenter studies have identified the factors determining successful outcome, and survival for SCID has shown great improvement. Advances in understanding the genetic basis of disease also mean that we increasingly tailor transplant protocols to the specific SCID form. Wherever possible, we attempt to transplant SCID patients without the use of cytoreductive conditioning, but it is clear that this is only successful for specific SCID forms and, although survival is good, in specific patients there are ongoing humoral defects. We aim to use matched related and unrelated donors (including cord blood) whenever possible and have limited the use of mismatched haploidentical donors. The development of autologous hematopoietic stem cell gene therapy provides another treatment of the X-linked and adenosine deaminase–deficient forms of SCID, and we discuss how we have integrated gene therapy into our treatment strategy. These developments together with the advent of universal newborn screening for SCID should allow for a highly favorable outcome for this otherwise lethal condition.

Primary Immune Deficiency Treatment Consortium (PIDTC) report

The Primary Immune Deficiency Treatment Consortium (PIDTC) is a network of 33 centers in North America that study the treatment of rare and severe primary immunodeficiency diseases. Current protocols address the natural history of patients treated for severe combined immunodeficiency (SCID), Wiskott-Aldrich syndrome, and chronic granulomatous disease through retrospective, prospective, and cross-sectional studies. The PIDTC additionally seeks to encourage training of junior investigators, establish partnerships with European and other International colleagues, work with patient advocacy groups to promote community awareness, and conduct pilot demonstration projects. Future goals include the conduct of prospective treatment studies to determine optimal therapies for primary immunodeficiency diseases. To date, the PIDTC has funded 2 pilot projects: newborn screening for SCID in Navajo Native Americans and B-cell reconstitution in patients with SCID after hematopoietic stem cell transplantation. Ten junior investigators have received grant awards. The PIDTC Annual Scientific Workshop has brought together consortium members, outside speakers, patient advocacy groups, and young investigators and trainees to report progress of the protocols and discuss common interests and goals, including new scientific developments and future directions of clinical research. Here we report the progress of the PIDTC to date, highlights of the first 2 PIDTC workshops, and consideration of future consortium objectives.

The natural history of children with severe combined immunodeficiency: baseline features of the first fifty patients of the primary immune deficiency treatment consortium prospective study 6901

The Primary Immune Deficiency Treatment Consortium (PIDTC) consists of 33 centers in North America. We hypothesized that the analysis of uniform data on patients with severe combined immunodeficiency (SCID) enrolled in a prospective protocol will identify variables that contribute to optimal outcomes following treatment. We report baseline clinical, immunologic, and genetic features of the first 50 patients enrolled, and the initial therapies administered, reflecting current practice in the diagnosis and treatment of both typical (n = 37) and atypical forms (n = 13) of SCID. From August 2010 to May 2012, patients with suspected SCID underwent evaluation and therapy per local center practices. Diagnostic information was reviewed by the PIDTC eligibility review panel, and hematopoietic cell transplantation (HCT) details were obtained from the Center for International Blood and Marrow Transplant Research. Most patients (92 %) had mutations in a known SCID gene. Half of the patients were diagnosed by newborn screening or family history, were younger than those diagnosed by clinical signs (median 15 vs. 181 days; P = <0.0001), and went to HCT at a median of 67 days vs. 214 days of life (P = <0.0001). Most patients (92 %) were treated with HCT within 1-2 months of diagnosis. Three patients were treated with gene therapy and 1 with enzyme replacement. The PIDTC plans to enroll over 250 such patients and analyze short and long-term outcomes for factors beneficial or deleterious to survival, clinical outcome, and T- and B-cell reconstitution, and which biomarkers are predictive of these outcomes.

Unresolved issues in hematopoietic stem cell transplantation for severe combined immunodeficiency: need for safer conditioning and reduced late effects

In this review we discuss recent outcomes of hematopoietic cell transplantation (HCT) for patients with severe combined immunodeficiency (SCID), including survival, T- and B-cell reconstitution, and late effects, particularly those related to genotype, use of conditioning regimen, and use of alternative donors. We identify the following issues that require additional data, which can be obtained through cooperative studies: outcomes of patients with SCID who did not receive conditioning before alternative donor HCT; outcomes of patients with SCID who did not receive graft-versus-host disease prophylaxis after T cell-replete HCT; late effects of HCT for patients with SCID, including neurocognitive outcomes, growth, and development; and their relationship to genotype and use of alkylating agents for conditioning. Careful follow-up of outcomes of all newborns receiving diagnoses based on newborn screening programs for SCID is essential because data are scarce on the effects of conditioning regimens in very young patients. A consensus on the definition of T- and B-cell recovery, criteria for additional "boosts," pharmacokinetic data of chemotherapy agents used in young children, and uniformity of the use of various chemotherapy agents are needed to compare results among institutions. Finally, development of new nontoxic conditioning regimens for HCT that can be safely used in very young children is required.

B-cell reconstitution for SCID: should a conditioning regimen be used in SCID treatment?

Bone marrow transplantation has resulted in life-saving sustained T-cell reconstitution in many infants with severe combined immunodeficiency (SCID), but correction of B-cell function has been more problematic. At the annual meeting of the Primary Immunodeficiency Treatment Consortium held in Boston, Massachusetts, on April 27, 2012, a debate was held regarding the use of pretransplantation conditioning versus no pretransplantation conditioning in an effort to address this problem. Reviews of the literature were made by both debaters, and there was agreement that there was a higher rate of B-cell chimerism and a lower number of patients who required ongoing immunoglobulin replacement therapy in centers that used pretransplantation conditioning. However, there were still patients who required immunoglobulin replacement in those centers, and therefore pretransplantation conditioning did not guarantee development of B-cell function. Dr Rebecca H. Buckley presented data on B-cell function according to the molecular defect of the patient, and showed that patients with IL-7 receptor α, ADA, and CD3 chain gene mutations can have normal B-cell function after transplantation with only host B cells. Dr Elie Haddad presented a statistical analysis of B-cell function in published reports and showed that only a conditioning regimen that contained busulfan was significantly associated with better B-cell function after transplantation. The question is whether the risk of immediate and long-term toxicity with use of busulfan is justified, particularly in patients with SCID with DNA repair defects and in very young newborns with SCID who will be detected by using newborn screening.

Molecular measurement of T cell receptor excision circles

This chapter provides protocols necessary for quantifying human, mouse, and nonhuman primate signal joint T cell receptor excision circles (sjTRECs) produced during T cell receptor alpha (TCRA) gene rearrangement. These non-replicated episomal circles of DNA are generated by the recombination process used to produce antigen-specific T cell receptors. The number of sjTRECs per mg of thymus tissue or per 100,000 lysed cells has been shown to be a molecular marker of thymopoiesis and naïve T cells. This technology is beneficial to investigators interested in quantitating the level of naïve T cell production occurring under various circumstances in a variety of systems, and complements traditional phenotypic analyses of thymopoiesis. This chapter specifically describes procedures required for rapid detection and quantitation of sjTRECs in thymus tissue or isolated cells using real-time quantitative polymerase chain reaction (PCR). The sjTREC assay system comprises species-specific forward and reverse primers for amplification of a unique site on the T cell receptor δ (TCRD) sjTREC, a fluorescently labeled (FAM/ZEN/IABkFQ) species-specific real-time probe, and a species-specific sjTREC DNA plasmid standard for quantitation.

Post-transplantation B cell function in different molecular types of SCID

PURPOSE

Severe combined immunodeficiency (SCID) is a syndrome of diverse genetic cause characterized by profound deficiencies of T, B and sometimes NK cell function. Non-ablative HLA-identical or rigorously T cell-depleted haploidentical parental bone marrow transplantation (BMT) results in thymus-dependent genetically donor T cell development in the recipients, leading to a high rate of long-term survival. However, the development of B cell function has been more problematic. We report here results of analyses of B cell function in 125 SCID recipients prior to and long-term after non-ablative BMT, according to their molecular type.

METHODS

Studies included blood immunoglobulin measurements; antibody titers to standard vaccines, blood group antigens and bacteriophage Φ X 174; flow cytometry to examine for markers of immaturity, memory, switched memory B cells and BAFF receptor expression; B cell chimerism; B cell spectratyping; and B cell proliferation.

RESULTS

The results showed that B cell chimerism was not required for normal B cell function in IL7Rα-Def, ADA-Def and CD3-Def SCIDs. In X-linked-SCID, Jak3-Def SCID and those with V-D-J recombination defects, donor B cell chimerism was necessary for B cell function to develop.

CONCLUSION

The most important factor determining whether B cell function develops in SCID T cell chimeras is the underlying molecular defect. In some types, host B cells function normally. In those molecular types where host B cell function did not develop, donor B cell chimerism was necessary to achieve B cell function. 236 words.

Immune recovery in adult patients after myeloablative dual umbilical cord blood, matched sibling, and matched unrelated donor hematopoietic cell transplantation

Immunologic reconstitution after allogeneic hematopoietic cell transplantation is a critical component of successful outcome. Umbilical cord blood (UCB) transplantation in adult recipients is associated with slow and often inadequate immune recovery. We characterized the kinetics and extent of immune recovery in 95 adult recipients after a dual UCB (n = 29) and matched sibling donor (n = 33) or matched unrelated donor (n = 33) transplantation. All patients were treated with myeloablative conditioning. There were no differences in the immune recovery profile of matched sibling donor and matched unrelated donor recipients. Significantly lower levels of CD3+, CD4+, and CD8+ T cells were observed in UCB recipients until 6 months after transplantation. Lower levels of regulatory T cells persisted until 1 year after transplantation. Thymopoiesis as measured by TCR rearrangement excision circle was comparable among all recipients by 6 months after transplantation. In a subset of patients 1 year after transplantation with similar levels of circulating T cells and TCR rearrangement excision circle, there was no difference in TCR diversity. Compared to HLA-identical matched sibling donor and matched unrelated donor adult hematopoietic cell transplantation recipients, quantitative lymphoid recovery in UCB transplantation recipients is slower in the first 3 months, but these differences disappeared by 6 to 12 months after transplantation.

Pre-existing T- and B-cell defects in one progressive multifocal leukoencephalopathy patient

Progressive multifocal leukoencephalopathy (PML) usually occurs in patients with severe immunosuppression, hematological malignancies, chronic inflammatory conditions or receiving organ transplant. Recently, PML has also been observed in patients treated with monoclonal antibodies. By taking advantage of the availability of samples from a multiple sclerosis (MS) patient treated with natalizumab, the antibody anti-α4 integrin, who developed PML and was monitored starting before therapy initiation, we investigated the fate of T and B lymphocytes in the onset of PML. Real-time PCR was used to measure new T- and B-cell production by means of T-cell receptor excision circle (TREC) and K-deleting recombination excision circle (KREC) analysis and to quantify transcripts for CD34, terminal-deoxynucleotidyltransferase, and V pre-B lymphocyte gene 1. T- and B-cell subsets and T-cell heterogeneity were measured by flow cytometry and spectratyping. The data were compared to those of untreated and natalizumab-treated MS patients and healthy donors. Before therapy, a patient who developed PML had a low TREC and KREC number; TRECs remained low, while KRECs and pre-B lymphocyte gene 1 transcripts peaked at 6 months of therapy and then decreased at PML diagnosis. Flow cytometry confirmed the deficient number of newly produced T lymphocytes, counterbalanced by an increase in TEMRA cells. The percentage of naive B cells increased by approximately 70% after 6 months of therapy, but B lymphocyte number remained low for the entire treatment period. T-cell heterogeneity and immunoglobulins were reduced.

Although performed in a single patient, all results showed that an immune deficit, together with an increase in newly produced B cells a few months after therapy initiation, may predispose the patient to PML. These findings indicate the TREC/KREC assay is a potential tool to identify patients at risk of developing PML and may provide insights into the immunological involvement of monoclonal antibody-associated therapies.

A Markov model to analyze cost-effectiveness of screening for severe combined immunodeficiency (SCID)

OBJECTIVE

To evaluate the cost-effectiveness of universal neonatal screening for T cell lymphocytopenia in enhancing quality of life and life expectancy for children with severe combined immunodeficiency (SCID).

METHODS

Decision trees were created and analyzed to estimate the cost, life years, and quality adjusted life years (QALYs) across a population when universal screening for lack of T cells is used to detect SCID, as implemented in five states, compared to detection based on recognizing symptoms and signs of disease. Terminal values of each tree limb were derived through Markov models simulating the natural history of three cohorts: unaffected subjects; those diagnosed with SCID as neonates (early diagnosis); and those diagnosed after becoming symptomatic and arousing clinical suspicion (late diagnosis). Models considered the costs of screening and of care including hematopoietic cell transplantation for affected individuals. Key decision variables were derived from the literature and from a survey of families with children affected by SCID, which was used to describe the clinical history and healthcare utilization for affected subjects. Sensitivity analyses were conducted to explore the influence of these decision variables.

RESULTS

Over a 70-year time horizon, the average cost per infant was $8.89 without screening and $14.33 with universal screening. The model predicted that universal screening in the U.S. would cost approximately $22.4 million/year with a gain of 880 life years and 802 QALYs. Sensitivity analyses showed that screening test specificity and disease incidence were critical driving forces affecting the incremental cost-effectiveness ratio (ICER). Assuming a SCID incidence of 1/75,000 births and test specificity and sensitivity each at 0.99, screening remained cost-effective up to a maximum cost of $15 per infant screened.

CONCLUSION

At our current estimated screening cost of $4.22/infant, universal screening for SCID would be a cost effective means to improve quality and duration of life for children with SCID.

T cell and B Cell immunity can be reconstituted with mismatched hematopoietic stem cell transplantation without alkylator therapy in artemis-deficient mice using anti-natural killer cell antibody and photochemically treated sensitized donor T cells

Children with Artemis-deficient T(-)B(-)NK(+) severe combined immunodeficiency are at high risk for graft rejection from natural killer (NK) cells and toxicity from increased sensitivity to the alkylating agents used in mismatched hematopoietic stem cell transplantation (HSCT). We evaluated the use of a nonalkylating agent regimen before HSCT in Artemis-deficient (mArt(-/-)) C57Bl/6 (B6) mice to open marrow niches and achieve long-term multilineage engraftment with full T cell and B cell immune reconstitution. We found that partial depletion of both recipient NK cells using anti-NK1.1 monoclonal antibody and donor T cells sensitized to recipient splenocytes was necessary. BALB/c-sensitized T cells (STCs) were photochemically treated (PCT) with psoralen and UVA light to inhibit proliferation, reduce the risk of graft-versus-host disease (GVHD), and target host hematopoietic stem cells (HSCs). A dose of 4 × 10(5) PCT STCs coinjected with 1 × 10(5) lineage-depleted c-kit(+) BALB/c HSCs resulted in 43.9% ± 3.3% CD4(+) and 10.9% ± 1.2% CD8(+) donor T cells in blood, 29% ± 7.8% and 21.7% ± 4.0 donor B220(+) IgM(+) in spleen and bone marrow, and 15.0% ± 3.6% donor Gran-1(+) cells in bone marrow at 6 months post-HSCT versus 0.02% ± 0.01%, 0.13% ± 0.10%, 0.53% ± 0.16%, 0.49% ± 0.09%, and 0.20% ± 0.06%, respectively, in controls who did not receive PCT STCs. We found that STCs target host HSCs and that PCT STCs are detectable only up to 24 hours after infusion, in contrast to non-photochemically treated STCs, which proliferate resulting in fatal GVHD. Increased mortality in the groups receiving 4-6 × 10(5) PCT STCs was associated with evidence of GVHD, particularly in the recipients of 6 × 10(5) cells. These results demonstrate that blocking NK cell-mediated resistance and making niches in bone marrow are both essential to achieving multilineage engraftment of mismatched donor cells and T cell and B cell reconstitution, even though GVHD is not completely eliminated.

Transplantation of hematopoietic stem cells in human severe combined immunodeficiency: longterm outcomes

Severe combined immunodeficiency (SCID) is a syndrome of diverse genetic cause characterized by profound deficiencies of T- and B-cell function and, in some types, also of NK cells and function. Mutations in thirteen different genes have been found to cause this condition, which is uniformly fatal in the first 2 years of life unless immune reconstitution can be accomplished. In the 42 years since the first bone marrow transplant was given in 1968, the standard treatment for all forms of SCID has been allogeneic bone marrow transplantation. Both HLA-identical unfractionated and T-cell-depleted HLA-haploidentical bone marrow transplants have been very successful in effecting immune reconstitution, especially if performed in the first 3.5 months of life and without pre-transplant chemotherapy. This paper summarizes the longterm outcome, according to molecular type, of 166 consecutive SCID infants given non-conditioned related donor bone marrow transplants at this institution over the past 28.3 years and reviews published reports of longterm outcomes of transplants in SCID performed at other centers.

The long and the short of telomeres in bone marrow recipient SCID patients

Telomeres are noncoding DNA regions at the end of the chromosomes that are crucial for genome stability. Since telomere length decreases with cell division, they can be used as a signature of cell proliferation history. T-cell reconstitution in severe combined immunodeficiency (SCID) subjects, recipients of T-cell-depleted, allogeneic-related bone marrow cells, is due to the development and maturation of donor T-cell precursors in the infant's vestigial thymus and to homeostatic proliferation of mature T cells in the peripheral organs. Since T-cell function, thymic output, and T-cell clonal diversity are maintained long term in these patients, we investigated whether donor T-cell engraftment resulted in increased telomere shortening. Our study of seven SCID patients, following successful bone marrow transplantation, demonstrates that the patients' peripheral T cells did not exhibit greater than normal telomere shortening.

Long-term outcome and lineage-specific chimerism in 194 patients with Wiskott-Aldrich syndrome treated by hematopoietic cell transplantation in the period 1980-2009: an international collaborative study

In this retrospective collaborative study, we have analyzed long-term outcome and donor cell engraftment in 194 patients with Wiskott-Aldrich syndrome (WAS) who have been treated by hematopoietic cell transplantation (HCT) in the period 1980- 2009. Overall survival was 84.0% and was even higher (89.1% 5-year survival) for those who received HCT since the year 2000, reflecting recent improvement of outcome after transplantation from mismatched family donors and for patients who received HCT from an unrelated donor at older than 5 years. Patients who went to transplantation in better clinical conditions had a lower rate of post-HCT complications. Retrospective analysis of lineage-specific donor cell engraftment showed that stable full donor chimerism was attained by 72.3% of the patients who survived for at least 1 year after HCT. Mixed chimerism was associated with an increased risk of incomplete reconstitution of lymphocyte count and post-HCT autoimmunity, and myeloid donor cell chimerism < 50% was associated with persistent thrombocytopenia. These observations indicate continuous improvement of outcome after HCT for WAS and may have important implications for the development of novel protocols aiming to obtain full correction of the disease and reduce post-HCT complications.

Early vs. delayed diagnosis of severe combined immunodeficiency: a family perspective survey

Infants affected with severe combined immunodeficiency (SCID) are susceptible to severe and recurrent infections and do not survive unless provided with immune reconstituting treatments. In the absence of population-based newborn screening, infants with SCID who do not have an affected older relative are ascertained only after they have developed infections. However, only limited data are available from the perspective of patients and families to indicate what proportion of SCID cases might benefit from earlier detection by pre-symptomatic screening, whether adequate treatment facilities are available, and how screening could improve SCID treatment outcomes. A survey of parents of children with SCID evaluated family history, pre- and post-diagnosis events, outcomes, and impact of SCID on families. Affected infants diagnosed with SCID as neonates had better survival, demonstrating the potential benefit of universal newborn screening.

More than just infections: an update on primary immune deficiencies

PURPOSE OF REVIEW

The general pediatrician should be empowered to utilize continuity of care for the recognition of unusual or severe patterns of infection. With the burgeoning field of genetics, primary immune deficiencies (PIDs) can be diagnosed and treated earlier to provide better outcomes for patients and families. Improved treatment modalities have redefined expectations for many infants born with PIDs.

RECENT FINDINGS

The prevalence of PIDs increases as researchers discover novel immunodeficiency syndromes and as clinicians increasingly recognize and diagnose nuanced presentations of immunodeficiency. Novel immunodeficiency syndromes associated with mutations in DOCK8, CARD9, and PRKDC recently have been described. For the first time in the United States, newborns from an entire state were screened for lymphopenia, allowing potentially life-saving early diagnosis of the most severe forms of PID before the onset of symptoms. Hematopoietic stem cell transplantation (HSCT) and gene therapy continue to be evaluated as curative treatments with increasing success rates for some of the most severe PIDs.

SUMMARY

The field of PID continues to expand and advancements have been made in earlier diagnosis and screening. Comparative effectiveness research into treatment modalities offered to patients with PID is leading to a better understanding of optimal therapies for specific PIDs. In the meantime, the advocacy efforts of established and emerging PID networks promote excellence in clinical recognition and treatment of PIDs in children.

Why newborn screening for severe combined immunodeficiency is essential: a case report

Physicians caring for infants in the first months of life need to know the normal ranges for absolute lymphocyte counts (ALCs) during that age. Any ALC <2500/microL is potentially pathogenic in early infancy and should be evaluated. We report the case of a 4-month-old white girl with a 2-month history of an oral ulcer, intermittent fever, recurrent otitis, decreased appetite, weight loss, and a new respiratory illness with hypoxemia. She had been in an in-home day care since birth. The patient's primary care physician had seen her frequently and obtained blood counts, but her persistent lymphopenia had not been appreciated. The infant was ultimately diagnosed with T(-)B(-)NK(+) (lacking both B and T lymphocytes and having primarily natural killer [NK] cells), recombinase-activating gene 2 (RAG2)-deficient severe combined immunodeficiency (SCID). However, because she had already developed 2 difficult-to-treat viral infections (parainfluenza 3 and adenovirus), she did not survive long enough to receive a bone marrow transplant. Newborn screening would not only have made the diagnosis at birth but would have led to measures to protect her from becoming infected before she could receive a transplant. Newborn screening would also reveal the true incidence of SCID and define the range of conditions characterized by severely impaired T-cell development. Until screening for SCID and other T-cell defects becomes available for all neonates (either by quantifying T-cell receptor excision circles in Guthrie spots or using other tests that quantify T cells), all pediatricians should know the normal range for ALCs according to age. Recognition of the characteristic lymphopenia of SCID can facilitate early diagnosis.

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.

Efficacy of gene therapy for X-linked severe combined immunodeficiency

BACKGROUND

The outcomes of gene therapy to correct congenital immunodeficiencies are unknown. We reviewed long-term outcomes after gene therapy in nine patients with X-linked severe combined immunodeficiency (SCID-X1), which is characterized by the absence of the cytokine receptor common gamma chain.

METHODS

The nine patients, who lacked an HLA-identical donor, underwent ex vivo retrovirus-mediated transfer of gamma chain to autologous CD34+ bone marrow cells between 1999 and 2002. We assessed clinical events and immune function on long-term follow-up.

RESULTS

Eight patients were alive after a median follow-up period of 9 years (range, 8 to 11). Gene therapy was initially successful at correcting immune dysfunction in eight of the nine patients. However, acute leukemia developed in four patients, and one died. Transduced T cells were detected for up to 10.7 years after gene therapy. Seven patients, including the three survivors of leukemia, had sustained immune reconstitution; three patients required immunoglobulin-replacement therapy. Sustained thymopoiesis was established by the persistent presence of naive T cells, even after chemotherapy in three patients. The T-cell-receptor repertoire was diverse in all patients. Transduced B cells were not detected. Correction of the immunodeficiency improved the patients' health.

CONCLUSIONS

After nearly 10 years of follow-up, gene therapy was shown to have corrected the immunodeficiency associated with SCID-X1. Gene therapy may be an option for patients who do not have an HLA-identical donor for hematopoietic stem-cell transplantation and for whom the risks are deemed acceptable. This treatment is associated with a risk of acute leukemia. (Funded by INSERM and others.)