Megadose CD34(+) cell grafts improve recovery of T cell engraftment but not B cell immunity in patients with severe combined immunodeficiency disease undergoing haplocompatible nonmyeloablative transplantation

Survival After Hematopoietic Stem Cell Transplantation in Severe Combined Immunodeficiency (SCID): A Worldwide Review of the Prognostic Variables

This study aims to perform an extensive review of the literature that evaluates various factors that affect the survival rates of patients with severe combined immunodeficiency (SCID) after hematopoietic stem cell transplantation (HSCT) in developed and developing countries. An extensive search of the literature was made in four different databases (PubMed, Embase, Scopus, and Web of Science). The search was carried out in December 2022 and updated in July 2023, and the terms such as "hematopoietic stem cell transplantation," "bone marrow transplant," "mortality," "opportunistic infections," and "survival" associated with "severe combined immunodeficiency" were sought based on the MeSH terms. The language of the articles was "English," and only articles published from 2000 onwards were selected. Twenty-three articles fulfilled the inclusion criteria for review and data extraction. The data collected corroborates that early HSCT, but above all, HSCT in patients without active infections, is related to better overall survival. The universal implementation of newborn screening for SCID will be a fundamental pillar for enabling most transplants to be carried out in this "ideal scenario" at an early age and free from infection. HSCT with an HLA-identical sibling donor is also associated with better survival rates, but this is the least common scenario. For this reason, transplantation with matched unrelated donors (MUD) and mismatched related donors (mMRD/Haploidentical) appear as alternatives. The results obtained with MUD are improving and show survival rates similar to those of MSD, as well as they do not require manipulation of the graft with expensive technologies. However, they still have high rates of complications after HSCT. Transplants with mMRD/Haplo are performed just in a few large centers because of the high costs of the technology to perform CD3/CD19 depletion and TCRαβ/CD19 depletion or CD34 + selection techniques in vitro. The new possibility of in vivo T cell depletion using post-transplant cyclophosphamide could also be a viable alternative for performing mMRD transplants in centers that do not have this technology, especially in developing countries.

Transplant for non-malignant disorders: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the role of alternative donors, stem cell sources and graft engineering

Hematopoietic stem cell transplantation (HSCT) is curative for many non-malignant disorders. As HSCT and supportive care technologies improve, this life-saving treatment may be offered to more and more patients. With the development of new preparative regimens, expanded alternative donor availability, and graft manipulation techniques, there are many options when choosing the best regimen for patients. Herein the authors review transplant considerations, transplant goals, conditioning regimens, donor choice, and graft manipulation strategies for patients with non-malignant disorders undergoing 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.

Low Exposure Busulfan Conditioning to Achieve Sufficient Multilineage Chimerism in Patients with Severe Combined Immunodeficiency

After allogeneic hematopoietic cell transplantation (HCT), the minimal myeloid chimerism required for full T and B cell reconstitution in patients with severe combined immunodeficiency (SCID) is unknown. We retrospectively reviewed our experience with low-exposure busulfan (cumulative area under the curve, 30 mg·hr/L) in 10 SCID patients undergoing either first or repeat HCT from unrelated or haploidentical donors. The median busulfan dose required to achieve this exposure was 5.9 mg/kg (range, 4.8 to 9.1). With a median follow-up of 4.5 years all patients survived, with 1 requiring an additional HCT. Donor myeloid chimerism was generally >90% at 1 month post-HCT, but in most patients it fell during the next 3 months, such that 1-year median myeloid chimerism was 14% (range, 2% to 100%). Six of 10 patients had full T and B cell reconstitution, despite myeloid chimerism as low as 3%. Three patients have not recovered B cell function at over 2 years post-HCT, 2 of them in the setting of treatment with rituximab for post-HCT autoimmunity. Low-exposure busulfan was well tolerated and achieved sufficient myeloid chimerism for full immune reconstitution in over 50% of patients. However, other factors beyond busulfan exposure may also play critical roles in determining long-term myeloid chimerism and full T and B cell reconstitution.

Immune reconstitution and survival of 100 SCID patients post-hematopoietic cell transplant: a PIDTC natural history study

The Primary Immune Deficiency Treatment Consortium (PIDTC) is enrolling children with severe combined immunodeficiency (SCID) to a prospective natural history study. We analyzed patients treated with allogeneic hematopoietic cell transplantation (HCT) from 2010 to 2014, including 68 patients with typical SCID and 32 with leaky SCID, Omenn syndrome, or reticular dysgenesis. Most (59%) patients were diagnosed by newborn screening or family history. The 2-year overall survival was 90%, but was 95% for those who were infection-free at HCT vs 81% for those with active infection (P = .009). Other factors, including the diagnosis of typical vs leaky SCID/Omenn syndrome, diagnosis via family history or newborn screening, use of preparative chemotherapy, or the type of donor used, did not impact survival. Although 1-year post-HCT median CD4 counts and freedom from IV immunoglobulin were improved after the use of preparative chemotherapy, other immunologic reconstitution parameters were not affected, and the potential for late sequelae in extremely young infants requires additional evaluation. After a T-cell-replete graft, landmark analysis at day +100 post-HCT revealed that CD3 < 300 cells/μL, CD8 < 50 cells/μL, CD45RA < 10%, or a restricted Vβ T-cell receptor repertoire (<13 of 24 families) were associated with the need for a second HCT or death. In the modern era, active infection continues to pose the greatest threat to survival for SCID patients. Although newborn screening has been effective in diagnosing SCID patients early in life, there is an urgent need to identify validated approaches through prospective trials to ensure that patients proceed to HCT infection free. The trial was registered at www.clinicaltrials.gov as #NCT01186913.

T Cell-Mediated Rejection of Human CD34+ Cells Is Prevented by Costimulatory Blockade in a Xenograft Model

A xenograft model of stem cell rejection was developed by co-transplantating human CD34⁺ and allogeneic CD3⁺ T cells into NOD-scid ɣ-chain^null mice. T cells caused graft failure when transplanted at any CD34/CD3 ratio between 1:50 and 1:.1. Kinetics experiments showed that 2 weeks after transplantation CD34⁺ cells engrafted the marrow and T cells expanded in the spleen. Then, at 4 weeks only memory T cells populated both sites and rejected CD34⁺ cells. Blockade of T cell costimulation was tested by injecting the mice with abatacept (CTLA4-IgG1) from day -1 to +27 (group A), from day -1 to +13 (group B), or from day +14 to +28 (group C). On day +56 groups B and C had rejected the graft, whereas in group A graft failure was completely prevented, although with lower stem cell engraftment than in controls (P = .03). Retransplantation of group A mice with same CD34⁺ cells obtained a complete reconstitution of human myeloid and B cell lineages and excluded latent alloreactivity. In this first xenograft model of stem cell rejection we showed that transplantation of HLA mismatched CD34⁺ cells may be facilitated by treatment with abatacept and late stem cell boost.

T-cell receptor αβ+ and CD19+ cell-depleted haploidentical and mismatched hematopoietic stem cell transplantation in primary immune deficiency

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is used as a therapeutic approach for primary immunodeficiencies (PIDs). The best outcomes have been achieved with HLA-matched donors, but when a matched donor is not available, a haploidentical or mismatched unrelated donor (mMUD) can be useful. Various strategies are used to mitigate the risk of graft-versus-host disease (GvHD) and rejection associated with such transplants.

OBJECTIVE

We sought to evaluate the outcomes of haploidentical or mMUD HSCT after depleting GvHD-causing T-cell receptor (TCR) αβ CD3⁺ cells from the graft.

METHODS

CD3⁺TCRαβ⁺/CD19⁺ depleted grafts were given in conditioned (except 3) children with PIDs. Treosulfan (busulfan in 1 patient), fludarabine, thiotepa, and anti-thymocyte globulin or alemtuzumab conditioning were used in 77% of cases, and all but 4 received GvHD prophylaxis.

RESULTS

Twenty-five patients with 12 types of PIDs received 26 HSCTs. Three underwent transplantation for refractory GvHD that developed after the first cord transplantation. At a median follow-up of 20.8 months (range, 5 month-3.3 years), 21 of 25 patients survived and were cured of underlying immunodeficiency. Overall and event-free survival at 3 years were 83.9% and 80.4%, respectively. Cumulative incidence of grade II to IV acute GvHD was 22% ± 8.7%. No case of visceral or chronic GvHD was seen. Cumulative incidences of graft failure, cytomegalovirus, and/or adenoviral infections and transplant-related mortality at 1 year were 4.2% ± 4.1%, 58.8% ± 9.8%, and 16.1% ± 7.4%, respectively. Patients undergoing transplantation with systemic viral infections had poor survival in comparison with those with absent or resolved infections (33.3% vs 100%).

CONCLUSION

CD3⁺TCRαβ⁺ and CD19⁺ cell-depleted haploidentical or mMUD HSCT is a practical and viable alternative for children with a range of PIDs.

Treatment of infants identified as having severe combined immunodeficiency by means of newborn screening

Severe combined immunodeficiency (SCID) is characterized by severely impaired T-cell development and is fatal without treatment. Newborn screening (NBS) for SCID permits identification of affected infants before development of opportunistic infections and other complications. Substantial variation exists between treatment centers with regard to pretransplantation care, and transplantation protocols for NBS identified infants with SCID, as well as infants with other T-lymphopenic disorders detected by using NBS. We developed approaches to management based on the study of infants identified by means of NBS for SCID who received care at the University of California, San Francisco (UCSF). From August 2010 through October 2016, 32 patients with NBS-identified SCID and leaky SCID from California and other states were treated, and 42 patients with NBS-identified non-SCID T-cell lymphopenia were followed. Our center's approach supports successful outcomes; systematic review of our practice provides a framework for diagnosis and management, recognizing that more data will continue to shape best practices.

Transplacental maternal engraftment and posttransplantation graft-versus-host disease in children with severe combined immunodeficiency

BACKGROUND

Graft-versus-host disease (GVHD) is a complication of allogeneic hematopoietic stem cell transplantation (HSCT). Transplacental maternal engraftment (TME), the presence of maternal T cells in peripheral blood before transplantation, is detectable in a significant proportion of patients with severe combined immunodeficiency (SCID). Although the presence of TME is associated with a decreased risk of rejecting a maternal graft, it is unknown whether TME plays a role in development of GVHD after HSCT.

OBJECTIVE

The purpose of this study was to determine whether the presence of pretransplantation TME is associated with posttransplantation GVHD in patients with SCID.

METHODS

This was an institutional retrospective review of 74 patients with SCID undergoing transplantation between 1988 and 2014. The incidence of acute graft-versus-host disease (aGVHD) was compared in patients with versus those without TME. Confounding variables, such as donor type and conditioning regimen, were included in a multivariate regression model.

RESULTS

TME was identified in 35 of 74 children. Post-HSCT aGVHD developed with an incidence of 57.1% versus 17.9% in those without TME (P < .001). In univariate analysis donor type (mother) and GVHD prophylaxis (T-cell depletion) were also significant predictors of aGVHD. In multivariate analysis TME and chemotherapy conditioning were independent risk factors for the development of aGVHD (relative risk, 2.75, P = .006 and relative risk, 1.42, P = .02, respectively).

CONCLUSION

TME independently predicts the development of posttransplantation aGVHD, even when controlling for donor type and conditioning used. The presence of TME should be considered when assessing the risk of aGVHD in patients with SCID and designing the approach for GVHD prophylaxis.

Conditioning with Fludarabine-Busulfan versus Busulfan-Cyclophosphamide Is Associated with Lower aGVHD and Higher Survival but More Extensive and Long Standing Bone Marrow Damage

Acute graft-versus-host disease (aGVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and a major cause of nonrelapse mortality after allo-HSCT. A conditioning regimen plays a pivotal role in the development of aGVHD. To provide a platform for studying aGVHD and evaluating the impact of different conditioning regimens, we established a murine aGVHD model that simulates the clinical situation and can be conditioned with Busulfan-Cyclophosphamide (Bu-Cy) and Fludarabine-Busulfan (Flu-Bu). In our study, BALB/c mice were conditioned with Bu-Cy or Flu-Bu and transplanted with 2 × 10⁷ bone marrow cells and 2 × 10⁷ splenocytes from either allogeneic (C57BL/6) or syngeneic (BALB/c) donors. The allogeneic recipients conditioned with Bu-Cy had shorter survivals (P < 0.05), more severe clinical manifestations, and higher hepatic and intestinal pathology scores, associated with increased INF-γ expression and diminished IL-4 expression in serum, compared to allogeneic recipients conditioned with Flu-Bu. Moreover, higher donor-derived T-cell infiltration and severely impaired B-cell development were seen in the bone marrow of mice, exhibiting aGVHD and conditioned with Flu-Bu. Our study showed that the conditioning regimen with Bu-Cy resulted in more severe aGVHD while the Flu-Bu regimen was associated with more extensive and long standing bone marrow damage.

Radiation-sensitive severe combined immunodeficiency: The arguments for and against conditioning before hematopoietic cell transplantation--what to do?

Defects in DNA cross-link repair 1C (DCLRE1C), protein kinase DNA activated catalytic polypeptide (PRKDC), ligase 4 (LIG4), NHEJ1, and NBS1 involving the nonhomologous end-joining (NHEJ) DNA repair pathway result in radiation-sensitive severe combined immunodeficiency (SCID). Results of hematopoietic cell transplantation for radiation-sensitive SCID suggest that minimizing exposure to alkylating agents and ionizing radiation is important for optimizing survival and minimizing late effects. However, use of preconditioning with alkylating agents is associated with a greater likelihood of full T- and B-cell reconstitution compared with no conditioning or immunosuppression alone. A reduced-intensity regimen using fludarabine and low-dose cyclophosphamide might be effective for patients with LIG4, NHEJ1, and NBS1 defects, although more data are needed to confirm these findings and characterize late effects. For patients with mutations in DCLRE1C (Artemis-deficient SCID), there is no optimal approach that uses standard dose-alkylating agents without significant late effects. Until nonchemotherapy agents, such as anti-CD45 or anti-CD117, become available, options include minimizing exposure to alkylators, such as single-agent low-dose targeted busulfan, or achieving T-cell reconstitution, followed several years later with a conditioning regimen to restore B-cell immunity. Gene therapy for these disorders will eventually remove the issues of rejection and graft-versus-host disease. Prospective multicenter studies are needed to evaluate these approaches in this rare but highly vulnerable patient population.

Hematopoietic Stem Cell Transplantation for Severe Combined Immunodeficiency

Hematopoietic stem cell transplantation (HSCT) is an effective approach for the treatment of severe combined immunodeficiency (SCID). However, SCID is not a homogeneous disease, and the treatment required for successful transplantation varies significantly between SCID subtypes and the degree of HLA mismatch between the best available donor and the patient. Recent studies are beginning to more clearly define this heterogeneity and how outcomes may vary. With a more detailed understanding of SCID, new approaches can be developed to maximize immune reconstitution, while minimizing acute and long-term toxicities associated with chemotherapy conditioning.

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.

A trial of plerixafor adjunctive therapy in allogeneic hematopoietic cell transplantation with minimal conditioning for severe combined immunodeficiency

For infants with SCID, the ideal conditioning regimen before allogeneic HCT would omit cytotoxic chemotherapy to minimize short- and long-term complications. We performed a prospective pilot trial with G-CSF plus plerixafor given to the host to mobilize HSC from their niches. We enrolled six patients who received CD34-selected haploidentical cells and one who received T-replete matched unrelated BM. All patients receiving G-CSF and plerixafor had generally poor CD34(+) cell and Lin(-) CD34(+) CD38(-) CD90(+) CD45RA(-) HSC mobilization, and developed donor T cells, but no donor myeloid or B-cell engraftment. Although well tolerated, G-CSF plus plerixafor alone failed to overcome physical barriers to donor engraftment.

A trial of alemtuzumab adjunctive therapy in allogeneic hematopoietic cell transplantation with minimal conditioning for severe combined immunodeficiency

For infants with SCID the ideal conditioning regimen before allogeneic HCT would omit cytotoxic chemotherapy to minimize short- and long-term complications. We performed a prospective pilot trial with alemtuzumab monotherapy to overcome NK-cell mediated immunologic barriers to engraftment. We enrolled four patients who received CD34-selected haploidentical cells, two of whom failed to engraft donor T cells. The two patients who engrafted had delayed T-cell reconstitution, despite rapid clearance of circulating alemtuzumab. Although well-tolerated, alemtuzumab failed to overcome immunologic barriers to donor engraftment. Furthermore, alemtuzumab may slow T-cell development in patients with SCID in the setting of a T-cell depleted graft.

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.).

Establishing diagnostic criteria for severe combined immunodeficiency disease (SCID), leaky SCID, and Omenn syndrome: the Primary Immune Deficiency Treatment Consortium experience

BACKGROUND

The approach to the diagnosis of severe combined immunodeficiency disease (SCID) and related disorders varies among institutions and countries.

OBJECTIVES

The Primary Immune Deficiency Treatment Consortium attempted to develop a uniform set of criteria for diagnosing SCID and related disorders and has evaluated the results as part of a retrospective study of SCID in North America.

METHODS

Clinical records from 2000 through 2009 at 27 centers in North America were collected on 332 children treated with hematopoietic stem cell transplantation (HCT), enzyme replacement therapy, or gene therapy for SCID and related disorders. Eligibility for inclusion in the study and classification into disease groups were established by using set criteria and applied by an expert review group.

RESULTS

Two hundred eighty-five (86%) of the patients were determined to be eligible, and 47 (14%) were not eligible. Of the 285 eligible patients, 84% were classified as having typical SCID; 13% were classified as having leaky SCID, Omenn syndrome, or reticular dysgenesis; and 3% had a history of enzyme replacement or gene therapy. Detection of a genotype predicting an SCID phenotype was accepted for eligibility. Reasons for noneligibility were failure to demonstrate either impaired lymphocyte proliferation or maternal T-cell engraftment. Overall (n = 332) rates of testing were as follows: proliferation to PHA, 77%; maternal engraftment, 35%; and genotype, 79% (mutation identified in 62%).

CONCLUSION

Lack of complete laboratory evaluation of patients before HCT presents a significant barrier to definitive diagnosis of SCID and related disorders and prevented inclusion of subjects in our observational HCT study. This lesson is critical for patient care, as well as the design of future prospective treatment studies for such children because a well-defined and consistent study population is important for precision in outcomes analysis.

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.

Haploidentical related-donor hematopoietic cell transplantation in children using megadoses of CliniMACs-selected CD34(+) cells and a fixed CD3(+) dose

We conducted a prospective phase II trial utilizing the CliniMACs system to perform CD34(+)-cell selection of PBSCs from haploidentical donors to evaluate engraftment and hematoimmunological reconstitution. In total, 21 children with hematological malignancies or nonmalignant conditions underwent conditioning with 1200 cGy TBI, thiotepa, fludarabine and Thymoglobulin. Patients received megadoses of CD34(+) cells (median: 22 × 10(6)/kg) with a fixed dose of 3 × 10(4)/kg CD3(+) cells/kg, and engraftment occurred in 90% with prompt recovery of neutrophils and platelets. Grade II acute GVHD (aGVHD) was seen in 32% (95% confidence interval (CI), 15-54%) of evaluable patients, there was no grade III-IV aGVHD, and chronic extensive GVHD was seen in 35% (95% CI, 17-59%) of patients. The estimated 2-year EFS was 62% (95% CI, 48-83%) with a median survivor follow-up of 49 months (range: 18-119 months). Patients with nonmalignant diseases had an estimated 2-year EFS of 100% (95% CI, 56-100%) and patients with malignancies in remission had an estimated 2-year EFS of 56% (95% CI, 22-89%). Megadose CD34(+) cells with a fixed CD3(+) cell dose from haploidentical related donors resulted in good outcomes for pediatric patients with nonmalignant diseases and those with malignant diseases transplanted in remission.

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.

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

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

Genotype, phenotype, and outcomes of nine patients with T-B+NK+ SCID

There are few reports of clinical presentation, genotype, and HCT outcomes for patients with T-B+NK+ SCID. Between 1981 and 2007, eight of 84 patients with SCID who received and/or were followed after HCT at UCSF had the T-B+NK+ phenotype. One additional patient with T-B+NK+ SCID was identified as the sibling of a patient treated at UCSF. Chart reviews were performed. Molecular analyses of IL7R, IL2RG, JAK3, and the genes encoding the CD3 T-cell receptor components δ (CD3D), ε (CD3E), and ζ (CD3Z) were carried out. IL7R mutations were documented in four patients and CD3D mutations in two others. Three patients had no defects found. Only two of nine patients had an HLA-matched related HCT donor. Both survived, and neither developed GVHD. Five of seven recipients of haploidentical grafts survived. Although the majority of reported cases of T-B+NK+ SCID are caused by defects in IL7R, CD3 complex defects were also found in this series and should be considered when evaluating patients with T-B+NK+ SCID. Additional genes, mutations in which account for T-B+NK+ SCID, remain to be found. Better approaches to early diagnosis and HCT treatment are needed for patients lacking an HLA-matched related donor.

Hematopoietic stem cell transplantation for CD3δ deficiency

BACKGROUND

CD3δ deficiency is a fatal form of severe combined immunodeficiency that can be cured by hematopoietic stem cell transplantation (HSCT). The presence of a thymus loaded with T-cell progenitors in patients with CD3δ deficiency may require special considerations in choosing the regimen of conditioning and the type of HSCT.

OBJECTIVES

To study the outcome of CD3δ deficiency by using various modalities of stem cell transplantation.

METHODS

We analyzed data on 13 patients with CD3δ deficiency who underwent HSCT in 7 centers. HSCT was performed by using different sources of donor stem cells as well as various conditioning regimens.

RESULTS

One patient received stem cells from a matched related donor and survived after a second transplant, needing substantial conditioning in order to engraft. Only 2 of 7 other patients who received a mismatched related donor transplant survived; 2 of them had no conditioning, whereas the others received various combinations of conditioning regimens. Engraftment of T cells in the survivors appears incomplete. Three other patients who received stem cells from a matched unrelated donor survived and enjoyed full immune reconstitution. Two patients received unrelated cord blood without conditioning. One of them has had a partial but stable engraftment, whereas the other engrafted well but is only 12 months after HSCT. We also report here for the first time that patients with CD3δ deficiency can present with typical features of Omenn syndrome.

CONCLUSIONS

HSCT is a successful treatment for patients with CD3δ deficiency. The small number of patients in this report prevents definitive statements on the importance of survival factors, but several are suggested: (1) HLA-matched donor transplants are associated with superior reconstitution and survival than are mismatched donor transplants; (2) substantial conditioning appears necessary; and (3) early diagnosis and absence of opportunistic infections may affect outcome.

Radiosensitive severe combined immunodeficiency disease

Inherited defects in components of the nonhomologous end-joining DNA repair mechanism produce a T-B-NK+ severe combined immunodeficiency disease (SCID) characterized by heightened sensitivity to ionizing radiation. Patients with the radiosensitive form of SCID may also have increased short- and long-term sensitivity to the alkylator-based chemotherapy regimens that are traditionally used for conditioning before allogeneic hematopoietic cell transplantation (HCT). Known causes of radiosensitive SCID include deficiencies of Artemis, DNA ligase IV, DNA-dependent protein kinase catalytic subunit, and Cernunnos-XLF, all of which have been treated with HCT. Because of these patients' sensitivity to certain forms of chemotherapy, the approach to donor selection and the type of conditioning regimen used for a patient with radiosensitive SCID requires careful consideration. Significantly more research needs to be done to determine the long-term outcomes of patients with radiosensitive SCID after HCT and to discover novel nontoxic approaches to HCT that might benefit those patients with intrinsic radiosensitivity and chemosensitivity as well as potentially all patients undergoing an HCT.

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

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

B-cell function in severe combined immunodeficiency after stem cell or gene therapy: a review

Although bone marrow transplantation has resulted in life-saving T-cell reconstitution in infants with severe combined immunodeficiency (SCID), correction of B-cell function has been more problematic. This review examines B-cell reconstitution results presented in 19 reports from the United States and Europe on posttransplantation immune reconstitution in patients with SCID over the past 2 decades. The analysis considered whether pretransplantation conditioning regimens were used, the overall survival rate, the percentage with donor B-cell chimerism, the percentage with B-cell function, and the percentage of survivors requiring immunoglobulin replacement. The survival rates were higher at those centers that did not use pretransplantation conditioning or posttransplantation graft-versus-host disease prophylaxis. The percentage of survivors with B-cell chimerism, function, or both was higher and the percentage requiring immunoglobulin replacement was lower at those centers that used pretransplantation conditioning. However, there were substantial numbers of patients requiring immunoglobulin replacement at all centers. Thus pretransplantation conditioning does not guarantee that B-cell function will develop. Because most infants with SCID either present with serious infections or are given diagnoses as newborns, one must decide whether there is justification for using agents that compromise innate immunity and have intrinsic toxicities to gain B-cell immune reconstitution.

Improving cellular therapy for primary immune deficiency diseases: recognition, diagnosis, and management

More than 20 North American academic centers account for the majority of hematopoietic stem cell transplantation (HCT) procedures for primary immunodeficiency diseases (PIDs), with smaller numbers performed at additional sites. Given the importance of a timely diagnosis of these rare diseases and the diversity of practice sites, there is a need for guidance as to best practices in management of patients with PIDs before, during, and in follow-up for definitive treatment. In this conference report of immune deficiency experts and HCT physicians who care for patients with PIDs, we present expert guidance for (1) PID diagnoses that are indications for HCT, including severe combined immunodeficiency disease (SCID), combined immunodeficiency disease, and other non-SCID diseases; (2) the critical importance of a high degree of suspicion of the primary care physician and timeliness of diagnosis for PIDs; (3) the need for rapid referral to an immune deficiency expert, center with experience in HCT, or both for patients with PIDs; (4) medical management of a child with suspicion of SCID/combined immunodeficiency disease while confirming the diagnosis, including infectious disease management and workup; (5) the posttransplantation follow-up visit schedule; (6) antimicrobial prophylaxis after transplantation, including gamma globulin administration; and (7) important indications for return to the transplantation center after discharge. Finally, we discuss the role of high-quality databases in treatment of PIDs and HCT as an element of the infrastructure that will be needed for productive multicenter clinical trials in these rare diseases.

Clinical and immunologic outcomes following haplocompatible donor lymphocyte infusions

We retrospectively analyzed the characteristics of 16 consecutive pediatric patients who received one or more G-CSF-mobilized donor lymphocyte infusions (DLI) following a T-cell-depleted haplocompatible hematopoietic SCT (HSCT) to enhance immune recovery and/or treat an infection. The median time from HSCT to administration of first DLI was 12 weeks and the median dose of DLI administered was 3 x 10(4)/kg (range, 2.5-6 x 10(4)/kg). The incidence of Grade I-II acute GVHD was 19% (95% confidence interval (CI), 6-44%), and there were no cases of Grade III-IV acute GVHD. Chronic GVHD developed in 13% (95% CI, 2-37%) of patients. In surviving patients who did not undergo a second stem cell infusion, T-cell numbers and function increased to a protective level in a median of 3 months (range, 2-12.5 months) following the first DLI administration. In patients given DLI for treatment of an infection, 75% (95% CI, 46-92%) cleared their infection after a median of 9 weeks (range, 1-27 weeks). In patients with CMV infection, the development of CMV-specific T cells was observed following DLI. The 1-year overall survival following haplocompatible DLI was 71% (95% CI, 59-83%), with a median follow-up of 16 months from the first DLI.

Allogeneic hematopoietic cell transplantation for primary immune deficiency diseases: current status and critical needs

Allogeneic hematopoietic cell transplantation (HCT) has been used for 40 years to ameliorate or cure primary immune deficiency (PID) diseases, including severe combined immunodeficiency (SCID) and non-SCID PID. There is a critical need for evaluation of the North American experience of different HCT approaches for these diseases to identify best practices and plan future investigative clinical trials. Our survey of incidence and prevalence of PID in North American practice sites indicates that such studies are feasible. A conference of experts in HCT treatment of PID has recommended (1) a comprehensive cross-sectional and retrospective analysis of HCT survivors with SCID; (2) a prospective study of patients with SCID receiving HCT, with comparable baseline and follow-up testing across participating centers; (3) a pilot study of newborn screening for SCID to identify affected infants before compromise by infection; and (4) studies of the natural history of disease in patients who do or do not receive HCT for the non-SCID diseases of Wiskott-Aldrich syndrome and chronic granulomatous disease. To accomplish these goals, collaboration by a consortium of institutions in North America is proposed. Participation of immunologists and HCT physicians having interest in PID and experts in laboratory methods, clinical outcomes assessment, databases, and analysis will be required for the success of these studies.