Minor histocompatibility antigens and marrow transplantation

Treatment Options in Steroid-Refractory Acute Graft-Versus-Host Disease Following Hematopoietic Stem Cell Transplantation

Objective:

To evaluate the treatment options in steroid-refractory acute graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation.

Data Sources:

Literature was obtained by searching MEDLINE (1966–May 2007) and EMBASE (1980–May 2007).

Study Selection and Data Extraction:

All pertinent clinical trials, retrospective studies, case reports, and compassionate use studies were identified and evaluated for safety and efficacy of the pharmacologic agents.

Data Synthesis:

Steroid-refractory acute GVHD is associated with high rates of morbidity and mortality. Although various pharmacologic agents have been studied in the treatment of steroid-refractory acute GVHD, no treatments have been established as a salvage therapy. Preliminary data on different pharmacologic agents have been identified and evaluated for their efficacy and tolerability in the treatment of steroid-refractory acute GVHD. The effects of the pharmacologic agents varied significantly among patients: severity of the disease, involvement of different organs, and the patient's age seem to be the major factors that affect an individual's response to drug therapy. In addition, the treatments are further challenged by the high incidence of potentially fatal opportunistic infections that occur during the therapy.

Conclusions:

Selection of pharmacologic agents for the treatment of steroid-refractory acute GVHD should be based on the target organs, adverse drug reactions, and economic factors. Further studies with larger sample sizes are warranted to better understand the roles of these agents in the treatment of steroid-refractory acute GVHD.

c-Rel is an essential transcription factor for the development of acute graft-versus-host disease in mice

Transcription factors of the Rel/NF-κB family are known to play different roles in immunity and inflammation, although the putative role of c-Rel in transplant tolerance and graft-versus-host disease (GVHD) remains elusive. We report here that T cells deficient for c-Rel have a dramatically reduced ability to cause acute GVHD after allogeneic bone marrow transplantation using major and minor histocompatibility mismatched murine models. In the study to understand the underlying mechanisms, we found that c-Rel(-/-) T cells had a reduced ability to expand in lymphoid organs and to infiltrate in GVHD target organs in allogeneic recipients. c-Rel(-/-) T cells were defective in the differentiation into Th1 cells after encountering alloantigens, but were enhanced in the differentiation toward Foxp3(+) regulatory T (Treg) cells. Furthermore, c-Rel(-/-) T cells had largely preserved activity to mediate graft-versus-leukemia response. Taken together, our findings indicate that c-Rel plays an essential role in T cells in the induction of acute GVHD, and suggest that c-Rel can be a potential target for therapeutic intervention in allogeneic hematopoietic cell transplantation in the clinic.

The influence of human platelet antigen match on the success of allogeneic peripheral blood progenitor cell transplantation following a reduced-intensity conditioning regimen

BACKGROUND

Allogeneic transplantation in elderly patients requires a dose-reduced conditioning regimen. Owing to reduced-intensity conditioning, host- and donor-type immune responses may affect the early posttransplant period, whereas only later on donor-derived reactions may ensue. Mismatches in the HLA system are known to be detrimental for the outcome of transplantation. Mismatches between donor and recipient for human platelet antigens (HPAs) may also affect the success of transplantation owing to serving as minor histocompatibility antigens and therefore rendering recipients at risk for graft-versus-host disease (GVHD) or graft rejection and inhibition of thrombopoiesis attributed to platelet (PLT) antibodies.

PATIENTS AND METHODS

Therefore, the occurrence of GVHD, incidence of relapse, need of PLT support, and outcome by analysis of 45 donor-recipient pairs for HPA-1, -2, -3, and -5 allotypes and screening for PLT antibodies were evaluated before transplantation and again 1 year thereafter.

RESULTS

Mismatches within the HPA system were not associated with an increased occurrence of transplant-related mortality or GVHD, the onset of thrombopoiesis, the frequency of PLT transfusions, or the incidence of relapse. Neither were settings of homozygous donors versus heterozygous recipients (graft-vs.-host direction) nor homozygous recipients versus heterozygous donors (host-vs.-graft direction) associated with any adverse effects on the outcome of the transplantation.

CONCLUSION

Thus, the HPA match does not affect the outcome of transplantation after reduced-intensity conditioning.

Power of association test for detecting minor histocompatibility gene causing graft-versus-host disease following bone marrow transplantation [correction]

Incompatibility of minor histocompatibility antigen (mHa) is a major cause of acute graft-versus-host disease (GVHD) following bone marrow transplantation in human leukocyte antigen (HLA)-matched donor-recipient pairs. To avoid acute GVHD, as many mHa genes as possible need to be identified. In this study, we introduce a comparison of two proportions as an association test for detecting mHa genes in HLA-matched pairs with and without GVHD. Assuming multiple mHa loci, each with two alleles, we evaluated the effects of (1). minor allele frequency of the mHa locus of interest (denoted by p), and (2). probability of GVHD developing in a donor-recipient pair being incompatible at an mHa locus (denoted by r) on the powers of association tests for unrelated pairs and for sib pairs. Our results showed that based on a candidate gene approach, an mHa gene with high p and r values can be detected by the association test with a small sample size. Application of the present method to the Japanese population revealed that the association test for unrelated pairs is more suitable for detecting an mHa gene with a high r value than that for sib pairs. The present method will be helpful to researchers who evaluate the power of association study in advance.

The immunogenicity of a new human minor histocompatibility antigen results from differential antigen processing

Minor histocompatibility antigens (mHAgs) present a significant impediment to organ and bone marrow transplantation between HLA-identical donor and recipient pairs. Here we report the identification of a new HLA-A*0201-restricted mHAg, HA-8. Designation of this mHAg as HA-8 is based on the nomenclature of Goulmy (Goulmy, E. 1996. Curr. Opin. Immunol. 8:75-81). This peptide, RTLDKVLEV, is derived from KIAA0020, a gene of unknown function located on chromosome 9. Polymorphic alleles of KIAA0020 encode the alternative sequences PTLDKVLEV and PTLDKVLEL. Genotypic analysis demonstrated that the HA-8-specific cytotoxic T lymphocyte (CTL) clone SKH-13 recognized only cells that expressed the allele encoding R at P1. However, when PTLDKVLEV was pulsed onto cells, or when a minigene encoding this sequence was used to artificially translocate this peptide into the endoplasmic reticulum, it was recognized by CTLs nearly as well as RTLDKVLEV. This indicates that the failure of CTLs to recognize cells expressing the PTLDKVLEV-encoding allele of KIAA0020 is due to a failure of this peptide to be appropriately proteolyzed or transported. Consistent with the latter possibility, PTLDKVLEV and its longer precursors were transported poorly compared with RTLDKVLEV by transporter associated with antigen processing (TAP). These studies identify a new human mHAg and provide the first evidence that minor histocompatibility differences can result from the altered processing of potential antigens rather than differences in interaction with the relevant major histocompatibility complex molecule or T cell receptor.

Strategy for mapping minor histocompatibility genes involved in graft-versus-host disease: a novel application of discordant sib pair methodology

We introduce a novel application for linkage analysis: using bone marrow donor-recipient sib pairs to search for genes influential in graft-versus-host disease (GVHD), a major cause of morbidity and mortality following allogeneic bone marrow transplantation. In particular, we show that transplant sib pairs in which the recipient developed severe GVHD can be used to map genes in the same way as traditional discordant (affected/unaffected) sib pairs (DSPs). For a plausible GVHD model, we demonstrate that the transplant/discordant sib pair analog of the "possible triangle test" [Holmans (1993) Am J Hum Genet 52:362-374] has similar power to that of the simpler "restricted test" proposed by Risch [(1990b) Am J Hum Genet 46:229-241; (1992) Am J Hum Genet 51:673-675]. Moreover, we show that the restricted test has superior power in much of the DSP possible triangle and significantly inferior power in only a small region. Thus, we conclude that the restricted test is preferable for localizing genes with transplant/discordant sib pairs. Finally, we examine the effects of heterogeneity on the power to detect GVHD loci and demonstrate the gain in efficiency by dividing the sample into genetically more homogeneous subgroups.

Allogeneic hematopoietic transplantation for chronic lymphocytic leukemia and lymphoma: potential for nonablative preparative regimens

There is increasing interest in the use of allogeneic blood and marrow transplants for chronic lymphocytic leukemia (CLL) and lymphomas. Numerous studies indicate efficacy in patients with advanced disease and demonstrate existence of a potent graft-versus-malignancy effect against these disorders. Allogeneic transplantation is most effective in CLL and low-grade lymphomas, but precise indications and timing of allogeneic transplants in these indolent disorders are not well defined. Allotransplantation is an effective, potentially curative approach, albeit with substantial risks; it is indicated in selected categories of patients. Allogeneic transplants are also promising for mantle cell lymphoma. In large-cell lymphoma, relapses are reduced in allogeneic compared with autologous transplants, but the benefit of allotransplantation has been offset by increased risk of treatment-related complications, and its indications are controversial. A promising new strategy is the use of less toxic, nonmyeloablative preparative regimens to achieve engraftment and allow development of graft-versus-malignancy effects that can produce durable remission in selected categories of lymphoid malignancies.

Graft-vs.-malignancy with allogeneic blood stem cell transplantation: a potential primary treatment modality

The high-dose chemotherapy and radiation typically used as the preparative regimen for bone marrow transplantation produces considerable morbidity and mortality. An alternative strategy is to utilize a low-dose, non-myeloablative, preparative regimen designed not to eradicate the malignancy, but to provide sufficient immunosuppression to achieve engraftment of an allogeneic hematopoietic graft and allow subsequent development of a graft-vs.-malignancy effect. We studied this approach in patients who were ineligible for standard myeloablative preparative regimens because of advanced age or comorbidities and demonstrated that purine analog (fludarabine or 2-CDA) containing non-myeloablative chemotherapy allows engraftment of HLA-compatible hematopoietic progenitor cells, and extended remissions were observed in approximately half of chemosensitive patients with recurrent AML or CML. Patients with CLL or lymphoma have been effectively treated using a non-myeloablative regimen of fludarabine/cyclophosphamide of fludarabine, cytarabine, cisplatin. This chemotherapy is known to be non-myeloablative and mixed chimerism was anticipated. All patients with engraftment have responded and 67% have achieved complete remission. Maximal responses are slow to develop and occur gradually over a period of several months to one year. Long-term efficacy must still be determined and controlled trials are necessary comparing this approach with alternative therapies as well as standard transplantation regimens.

Allogeneic hematopoietic transplantation as adoptive immunotherapy. Induction of graft-versus-malignancy as primary therapy

An immune-mediated graft-versus-malignancy effect is important to prevent relapse after allogeneic bone marrow transplant for a range of hematologic malignancies and potentially some solid tumors. Graft-versus-leukemia (GVL) effects as seen in response to donor lymphocyte infusions have been most prominent against indolent malignancies including chronic myelogenous leukemia, chronic lymphocytic leukemia, and low-grade lymphoma. Acute myelogenous leukemia and multiple myeloma may also respond. An alternative strategy for allogeneic transplantation is to avoid the toxicity of high-dose chemoradiotherapy and use a relatively nontoxic, nonablative preparative regimen to achieve engraftment, allowing subsequent infusion of additional donor lymphocytes to mediate GVL. Fludarabine-based nonablative chemotherapy agents, using standard dose combinations, produce moderate myelosuppression but are sufficiently immunosuppressive to allow engraftment of an allogeneic hematopoietic transplant and generation of graft-versus-malignancy effects.

A second unrelated bone marrow transplant: successful quantitative monitoring of mixed chimerism using a highly discriminative PCR-STR system

A second bone marrow transplant (BMT) might be considered as an option in patients with leukaemia with graft failure after BMT. We report the successful treatment of a patient with graft failure by a second stem cell transplant from another unrelated donor. We evaluated the usefulness of an unrelated donor as the source of the second BMT in this clinical setting. In addition to this, a penta PCR-STR system was tested and shown to be sensitive for monitoring of marrow engraftment. The conditioning regimen for the first transplantation consisted of busulfan and cyclophosphamide while anti-thymocyte globulin and CY were used for the second BMT. The patient successfully engrafted at day +11 after second BMT.

A special report: histocompatibility testing guidelines for hematopoietic stem cell transplantation using volunteer donors. Quality Assurance and Donor Registries Working Groups of the World Marrow Donor Association

The World Marrow Donor Association has formulated guidelines for establishing the extent and quality of histocompatibility testing for unrelated donor registries, umbilical cord blood banks, and transplant centers involved in international exchange of hematopoietic stem cells for allogeneic transplantation. Registry and cord blood bank guidelines suggest that, at a minimum, initial HLA typing should be performed for three HLA loci, HLA-A, -B, and -DR, at low resolution/split antigen level. DNA-based testing methods should be utilized for HLA-DR typing. DNA-based testing for HLA-A and -B should replace serologic testing of new volunteer donors and cord blood units as robust protocols and reagents become available to the laboratories. Transplant center guidelines for typing of patient, family and to confirm the HLA types of potential unrelated donors should include, at the minimum, typing HLA-A, B, and -DR loci using primarily DNA-based testing methods at allele level resolution for DRB1 and low resolution/split antigen level for HLA-A and -B. It is strongly recommended that the typing of a patient and the selected donor be performed using the same set of reagents, methodology, and interpretation criteria with fresh tissue samples to ensure HLA identity. Guidelines for laboratory accreditation, approaches to quality assurance and quality control for HLA testing, and suggestions for the format of the HLA database of donor types are also outlined.

CD34 positive blood cells for allogeneic progenitor and stem cell transplantation

The transplantation of allogeneic peripheral blood progenitor cells (PBPC) provides complete and sustained hematopoietic and lymphopoietic engraftment. In healthy donors, large amounts of PBPC can be mobilized with hematopoietic growth factors. However, the high content of immunocompetent T-cells in apheresis products may expose recipients of allogeneic PBPC to an elevated risk of acute and chronic graft-versus-host disease. Thus, the use of appropriate T-cell reduction, but not depletion might reduce this risk. The hazards of graft rejection and a higher relapse rate can be avoided by maintaining a portion of the T-cells in the graft. The positive selection of CD34+ cells from peripheral blood preparations simultaneously provides an approximately 1000-fold reduction of T-cells. These purified CD34+ cells containing committed and pluripotent stem cells are suitable for allogeneic transplantation and can be used in the following instances: 1. As hematopoietic stem and progenitor cell transplantation instead of bone marrow cells, from HLA-identical family donors; 2. for increasing the stem cell numbers from HLA-mismatched or three HLA-loci different family donors in order to reduce the incidence of rejection but without increasing the T-cell number; 3. boosting of poor marrow graft function with stem cells from the same family donors; 4. transplantation from volunteer matched unrelated donors; 5. split transplantation of CD34+ and T-cells; 6. addition of ex vivo expanded CD34+ cells to blood cell or bone marrow transplantation; 7. generation of antigen specific immune effector cells and antigen presenting cells for cell therapy.

[Transplantation of hematopoietic stem cells. I: Definitions, principle indications, complications]

The transplantation of hematopoietic and lymphopoetic stem and progenitor cells has become a standard procedure for the treatment of many malignant diseases. Autologous stem cells are derived from the patient himself, allogeneic cells from an HLA-identical or HLA-compatible family or unrelated donor. Hematopoietic stem cells can be obtained from bone marrow, blood and fetal cord blood. After 3 to 5 days treatment, the granulocyte-colony stimulating factor (G-CSF) mobilizes stem- and progenitor cells from the marrow into the blood. This method is now standard in autologous transplantation and is increasingly preferred in allogeneic transplantation. The time to hematopoietic recovery is shorter with blood stem cells than with bone marrow cells. With myeloablative high dose therapy followed by stem cell transplantation, long term disease free survival is possible in many cases and great proportions of patients can be cured (see part II). Improvements of supportive care have reduced toxicity of treatment substantially, however severe complications still occur at oropharynx, gastrointestinal tract, liver, lung, skin, kidney, urinary tract and nervous system. After allogeneic transplantation immunocompetent donor cells can react with the recipients tissue. In HLA-identical donor and recipients differences in the minor histocompatibility antigens account for this graft-versus-host-reaction (GvH), which is mainly mediated by transplanted T-cells. The GvH-reaction can affect skin, liver, gut and other organs and cause clinically relevant GvH-disease (GvHD). The GvHD is more severe in HLA-mismatched or unrelated transplantations. Immunodeficiency and organ dysfunction due to GvHD may predispose infections and impair the outcome of transplantation. Unrelated cord blood stem cells may have a minor risk of inducing acute GvHD, as stem and T-cells are immature. After allogeneic stem cell transplantation, the relapse rate of leukemia or lymphoma is significantly reduced by immunoreactive cells:graft-versus-tumor (GvT) or graft-versus-leukemia effect (GvL).