Non-myeloablative stem cell transplantation for congenital immunodeficiencies

Keratinocyte growth factor ameliorates acute graft-versus-host disease in a novel nonmyeloablative haploidentical transplantation model

Allogeneic stem cell transplantations (SCT) are currently being used as a therapy for hematological malignancies, some solid tumors and nonmalignant bone marrow deficiencies. Nevertheless, clinical applicability is limited due to toxicity of conditioning regimens, graft-versus-host disease (GVHD) and the scarcity of HLA-identical family donors. New concepts are based on nonmyeloablative conditioning to reduce toxicity, prevention or amelioration of GVHD and the use of haploidentical donors to increase donor availability. To combine these requirements, we have developed a nonmyeloablative conditioning regimen, consisting of low-dose total body irradiation and cyclophosphamide-based chemotherapy. In a haploidentical F1 --> F1 mouse model, this nonmyeloablative transplantation protocol resulted in stable full donor chimerism, but also in the development of severe GVHD. Administration of keratinocyte growth factor (KGF) reduced GVHD, evident as reduced weight loss and a lesser degree of dermatitis, compared to saline-treated controls. KGF preserved plasma citrulline and tumor necrosis factor-alpha levels, both indicative for reduced injury to the gastrointestinal tract. This was confirmed by histological findings. At 6 months after transplantation, survival rates were significantly higher in KGF-treated animals as compared to phosphate buffered saline-treated controls. These results indicate that KGF preserves gut integrity and might therefore contribute substantially to reduction of lethal GVHD in (nonmyeloablative) haploidentical transplantation.

Campath-1H use in pediatric renal transplantation

Campath-1H is a humanized, monoclonal antibody directed against CD52 determinants on the surface of human B- and T-cells and monocytes. Reports of Campath-1H use as induction in adult renal transplantation have been encouraging with low rejection rates and minimal adverse events. We report four high risk pediatric kidney transplant patients who received Campath-1H for unique indications with variable results. Children ranged in age from 20 months to 16 years. Immunosuppression regimens varied. Three of four patients experienced acute rejection, two of which were C4d positive. Serial flow cytometry was performed on all four patients. The patient who received only Campath-1H has an absolute lymphocyte count that remains less than 50% of baseline at 12-months post-transplant. In addition, in this patient CD3, CD4, CD8 and CD20 remain less than 50% of baseline. From this initial experience using Campath-1H in pediatric renal transplantation we conclude that; (1) the use of Campath-1H does not prevent recurrence of FSGS, (2) as seen in adults, lack of calcineurin inhibition when using Campath-1H may increase the risk of antibody-mediated rejection and (3) prolonged lymphocyte depletion remains even after a single dose of Campath-1H in children.

Unrelated donor marrow transplantation for congenital immunodeficiency and metabolic disease: an update of the experience of the Japan Marrow Donor Program

We retrospectively analyzed the clinical results of 81 patients with congenital genetic diseases who were treated with bone marrow transplantation (BMT) from unrelated donors identified through the Japan Marrow Donor Program. The patients were aged between 1 and 38 years (median, 4 years). Thirty-five patients underwent transplantation for metabolic disease (MD), ie, mucopolysaccharidosis (n = 25), adrenoleukodystrophy (n = 7), and others (n = 3). The remaining 46 patients had Wiskott-Aldrich syndrome (n = 16), hemophagocytic syndrome including the inherited type (n = 9), severe combined immunodeficiency (n = 6), hyper-IgM syndrome (n = 4), Chédiak-Higashi syndrome (n = 3), Kostmann syndrome (n = 3), and others (n = 5). Fifty-two donor-patient pairs were fully matched at HLA-A, HLA-B, and HLA-DRB1 alleles. The remaining 24 patients received allele-mismatched grafts (20 matched at 5 of 6 loci and 4 matched at 4 of 6 loci). Engraftment occurred in 82.4% of the MD group and 90.7% of the other genetic disease (OGD) group; however, 14 patients (18.2%) experienced either early or late graft failure. The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 35.5% - 9.8% in the MD group and 47.3% - 9.5% in the OGD group, and the rate of chronic GVHD was 20% in both groups. Forty-nine patients have survived for 3 to 96 months (median, 20 months). The probabilities of 5-year overall survival and event-free survival were 72.6% - 11.5% and 65.3% - 8.6%, respectively, for MD (n = 35) and 72.5% - 7.3% and 63.6% - 7.3% for OGD (n = 46). Although patient status before BMT and the occurrence of grade III to IV acute GVHD significantly affected outcome, unrelated BMT is a curative therapeutic option for children with congenital genetic diseases who have no HLA-matched family donors.

Present experience with Campath-1H in organ transplantation and its potential use in pediatric recipients

Campath-1H is a humanized monoclonal antibody directed at CD52 expressed on lymphocytes and other cells of the immune system. It has been tested extensively in lymphoid malignancies, autoimmune diseases including rheumatoid arthritis, multiple sclerosis, and organ transplantation. Although its use in children has been limited to date, so far it appears to be well tolerated in children. Currently, studies are being implemented to further assess its safety and efficacy in pediatric organ transplantation. Immune cell depletion using Campath-1H appears to be particularly useful in organ transplantation in that lower doses of maintenance immunosuppressive drugs are needed. This feature is particularly attractive in children.

An international study examining therapeutic options used in treatment of Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome is a rare immunodeficiency characterized by thrombocytopenia, eczema, recurrent infections, autoimmunity, and an increased incidence of malignancy. Clinical severity is highly variable. As a first step toward the development of therapeutic guidelines, an international study to evaluate current treatment strategies was undertaken. A total of 73 centers from 24 countries participated. These centers provide care for 507 patients with Wiskott-Aldrich syndrome. Treatment strategies were strikingly variable in both small and large centers. Most options were used in at least some patients in the majority of centers, indicating that treatment is individualized; however, there were some clear trends. Most centers use intravenous gammaglobulin and prophylactic antibiotics in the majority of patients. Splenectomy was used more sparingly. Stem cell transplant was more likely to be used in centers providing care for 10 or more patients. Studies that better define prognostic markers and optimal therapy are needed.

In vitro susceptibility of CD4+ and CD8+ T cell subsets to fludarabine

Administration of the adenosine analogue fludarabine (FLU) in vivo induces a profound and prolonged T lymphopenia which mainly affects CD4(+) cells. To better understand the mechanistic basis underlying this preferential depletion, we analyzed the in vitro susceptibility of T cell subsets to FLU-induced apoptosis. Contrasting with observations in vivo, our results showed that treatment of peripheral blood mononuclear cells with FLU induced a higher level of apoptosis in CD8(+) than in CD4(+) T lymphocytes. This increased sensitivity of CD8(+) T cells to FLU was observed in samples from both, healthy donors and B cell chronic lymphocytic leukemia patients, and resulted in higher CD4:CD8 ratios in FLU-treated than in untreated cultures (P<0.01). Expression of factors involved in FLU transport and metabolism was then evaluated by quantitative real time-PCR in normal T cell subsets. It was found that mRNA levels of human equilibrative nucleoside transporter-1 nucleoside transporter were higher whereas deoxycytidine kinase and IMP/GMP selective 5'-nucleotidase mRNA levels were lower in CD4(+) cells. However the dCK/cN-II ratio was 2-fold greater in CD8(+) than in CD4(+) T lymphocytes, which could account for the higher apoptosis levels observed in the CD8(+) subset. These results favor the view that decreased CD4:CD8 ratios in FLU-treated patients should be attributed to differences in cell recovery and/or homing between T cell subsets.

Stem cell transplants for patients with X-linked agammaglobulinemia

Six young patients with X-linked agammaglobulinemia and proven mutations in Btk were treated with cord blood or bone marrow transplants from HLA-matched siblings. Complete blood counts, serum chemistries, serum immunoglobulin concentrations, lymphocyte cell surface markers, and physical findings were evaluated at 3- to 5-day intervals for the first 2 weeks after transplant and then every 3 to 6 months. The first three patients were not given any preparative regimen or antirejection drugs and at 24 to 42 months posttransplant these patients have shown no benefit or harm related to the transplants. The second three patients were not given a preparative regimen but were treated with cyclosporine A (70 days) and mycophenolate mophetil (28 days) after transplant. Two of these patients have developed normal sized, nontender cervical lymph nodes 3 to 12 months after transplant but none of the three patients have shown an increase in serum IgM or an increase in the number of peripheral blood B cells. It is likely that successful engraftment will require more aggressive immunosupressive medications.

Reconstitution of B cell function in murine models of immunodeficiency

Murine models of immunodeficiency were used to evaluate strategies that might allow B cell engraftment in patients with X-linked agammaglobulinemia. Mice with defects in Btk or mu heavy chain were given 2.5 x 10(6) bone marrow cells from wild-type congenic donors. In the absence of any preparative regimen or immunosuppression, Btk-deficient mice on the CBA background developed normal concentrations of serum IgM and IgG3 by 12 weeks posttransplant. By contrast, mu heavy chain-deficient mice on the C57BL/6 background required some immunosuppression to achieve engraftment. Treatment of these mice with anti-T-cell antibodies 2 and 4 days prior to transplant resulted in normal concentrations of serum immunoglobulins by 6 weeks posttransplant. These pretreated mice had only 10% of the normal number of splenic B cells and they had no evidence of donor T cell engraftment. These results suggest that myelotoxic drugs may not be needed to achieve B cell engraftment in B-cell-deficient subjects.

27. Transplantation immunology: organ and bone marrow

The discovery of the human MHC in 1967 launched the field of organ and tissue transplantation. More than 800,000 such transplants have been performed during this time. Although matching of donor and recipient for MHC antigens was shown to be of great importance and continues to be so, the development of pharmacologic agents and antilymphocyte antibodies that interfere with the process of graft rejection has had a crucial role in the success of organ transplantation during the past 2 decades. Enormous progress has been made in understanding the immunologic mechanisms of graft rejection and of graft-versus-host disease. The roles of antibodies, antigen-presenting cells, helper and cytotoxic T cells, immune cell surface molecules, and signaling mechanisms and the cytokines they release have been clarified. This understanding is leading to the development of newer immunosuppressive agents targeting various components of the rejection process. Combinations of these agents work synergistically, leading to lower doses and reduced toxicity. Similarly, the development of effective T-cell depletion techniques has been of great importance for bone marrow transplantation when an HLA-identical sibling is not available. The major obstacle to the performance of solid organ transplantation currently is the shortage of donor organs.

Infectious risks and outcomes after stem cell transplantation: are nonmyeloablative transplants changing the picture?

PURPOSE OF REVIEW

Opportunistic infections contribute to morbidity and mortality after myeloablative allogeneic stem cell transplantation. The development of nonmyeloablative or toxicity-reduced conditioning regimens for allogeneic hematopoietic stem cell transplantation might change this picture significantly. These regimens are in general highly immunosuppressive, but effects on myelopoiesis and mucosal toxicities are usually reduced compared with myeloablative hematopoietic stem cell transplantation conditioning regimens. This review summarizes the infectious risks associated with each type of hematopoietic stem cell transplantation conditioning regimen, and presents the results of early clinical studies.

RECENT FINDINGS

Although the data are preliminary, the results of recent studies suggest that nonmyeloablative conditioning regimens may decrease the risks of bacterial infections associated with mucosal damage and persistent neutropenia; however, risks for late viral and fungal infections persist during severe graft versus host disease. Results of several case reports and series emphasize that therapeutic outcomes of infections may be improved in patients who receive nonmyeloablative conditioning regimens.

SUMMARY

Infectious risks and outcomes after hematopoietic stem cell transplantation appear to be in evolution given the introduction of alternative, nonmyeloablative conditioning regimens. Although infections remain a prominent cause of transplant-related mortality, the timing and types of infections may differ. Further studies are necessary to define appropriate preventative strategies, and to determine whether patients with ongoing infections might benefit from nonmyeloablative hematopoietic stem cell transplantation.