Minor histocompatibility antigen DBY elicits a coordinated B and T cell response after allogeneic stem cell transplantation

Targeting minor histocompatibility antigens in graft versus tumor or graft versus leukemia responses

Allogeneic hematopoietic cell transplantation (alloHCT) represents the only curative therapy for several hematologic malignancies, and shows promise as a nascent treatment modality for select solid tumors. Although the original goal of alloHCT was hematopoietic reconstitution after sub-lethal chemoradiotherapy, recognition of a profound donor lymphocyte-mediated graft-versus-leukemia (GVL) or graft-versus-tumor (GVT) effect has shifted the paradigm from pre-transplant cytoreduction to tumor control via donor lymphocytes. In human leukocyte antigen (HLA)-compatible alloHCT, GVL and GVT reactions are induced primarily by donor T-cell recognition of minor histocompatibility antigens (mHAgs). Here we review the literature regarding mHAg-specific T cells in GVL and GVT reactions, and discuss the prospects of exploiting mHAgs as immunotherapeutic targets.

H-Y antibody development associates with acute rejection in female patients with male kidney transplants

BACKGROUND

Human minor histocompatibility antigens (mHA) and clinically relevant immune responses to them have not been well defined in organ transplantation. We hypothesized that women with male kidney transplants would develop antibodies against H-Y, the mHA encoded on the Y-chromosome, in association with graft rejection.

METHODS

We tested sera from 118 consecutive transplant recipients with kidney biopsies. Antibodies that specifically recognized the recombinant H-Y antigens RPS4Y1 or DDX3Y were detected by IgG enzyme-linked immunosorbent assay and western blotting. Immunogenic epitopes were further identified using overlapping H-Y antigen peptides for both the H-Y proteins.

RESULTS

In the 26 female recipients of male kidneys, H-Y antibody development posttransplant (1) was more frequent (46%) than in other gender combinations (P<0.001), (2) showed strong correlation with acute rejection (P=0.00048), (3) correlated with plasma cell infiltrates in biopsied kidneys (P=0.04), and (4) did not correlate with C4d deposition or donor-specific anti-human leukocyte antigen (HLA) antibodies. Of the two H-Y antigens, RPS4Y1 was more frequently recognized (P=0.005).

CONCLUSION

This first demonstration of a strong association between H-Y antibody development and acute rejection in kidney transplant recipients shows that in solid organ allografts, humoral immune responses against well defined mHA have clear clinical correlates, can be easily monitored, and warrant study for possible effects on long-term graft function.

Are there effective new strategies for the treatment of acute and chronic GvHD?

The molecular biology and pathophysiology underlying graft-versus-host disease (GvHD) remains an area of intensive research. Understanding normal and abnormal developments of both the innate and adaptive immune systems are beginning to provide understanding of the details of relevant pathways. Recent work in gene-expression profiling suggests a critical next step in identifying broader patterns that will stand up to examination in independent data sets and provide a sturdy basis for targeted therapy and preventive measures against GvHD.

Humoral immune responses against the immature laminin receptor protein show prognostic significance in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by a highly variable clinical course. The role of an autologous tumor-specific immune control contributing to the variable length of survival in CLL is poorly understood. We investigated whether humoral immunity specific for the CLL-associated Ag oncofetal Ag/immature laminin receptor (OFA/iLR) has a prognostic value in CLL. Among sera of 67 untreated patients with CLL, 23 (34.3%) had detectable OFA/iLR Abs that were reactive for at least one specific OFA/iLR epitope. Patients with humoral responses compared with patients with nonreactive sera had a longer progression-free survival (p = 0.029). IgG subclass analyses showed a predominant IgG1 and IgG3 response. OFA/iLR Abs were capable of recognizing and selectively killing OFA/iLR-expressing CLL cells in complement-mediated and Ab-dependent cellular cytotoxicity assays. In the analysis of 11 CLL patients after allogeneic hematopoietic stem cell transplantation, 8 showed high values for OFA/iLR Abs that specifically recognized the extracellular domain of the protein, suggesting a potential role of anti-OFA/iLR-directed immune responses to the graft-vs-leukemia effect in CLL. Our data suggest that spontaneous tumor-specific humoral immune responses against OFA/iLR exist in a significant proportion of CLL patients and that superior progression-free survival in those patients could reflect autologous immune control.

Kidney transplantation: mechanisms of rejection and acceptance

We describe the molecular and cellular mechanisms believed to be responsible for the rejection of renal allografts, including acute T cell-mediated rejection, acute antibody-mediated (humoral) rejection, rejection mediated by the innate immune system, and chronic rejection. We present mechanisms of graft acceptance, including accommodation, regulation, and tolerance. Studies in animals have replicated many pathologic features of acute and chronic rejection. We illuminate the pathogenesis of human pathology by reflection from experimental models.

DDX3Y encodes a class I MHC-restricted H-Y antigen that is expressed in leukemic stem cells

The Y chromosome encodes male-specific minor histocompatibility (H-Y) antigens that stimulate T- and B-lymphocyte responses after sex-mismatched allogeneic hematopoietic cell transplantation (HCT). A CD8(+) cytotoxic T lymphocyte (CTL) clone that recognizes a novel HLA-B*2705-restricted H-Y antigen encoded by the DDX3Y gene was isolated from a male who had received a hematopoietic cell graft from his human leukocyte antigen (HLA)-identical sister. The antigenic peptide is a decamer that differs from the homologous DDX3X-encoded peptide at 4 positions. Expression of DDX3Y and of the H-Y epitope that it encodes was examined by quantitative polymerase chain reaction (PCR) and by CTL recognition assays. Expression of DDX3Y is detected in all myeloid and lymphoid leukemic cells that carry an intact Y chromosome. Moreover, the DDX3Y-encoded H-Y epitope is presented on the surface of both myeloid and lymphoid leukemic cells from male HLA-B*2705(+) patients. DDX3Y-specific CTLs prevent engraftment of human acute leukemia in nonobese diabetic/severe combined immune deficient mice, demonstrating that the DDX3Y-encoded H-Y antigen is also expressed in leukemic stem cells. These results demonstrate that CD8(+) T-cell responses against DDX3Y have the potential to contribute to graft-versus-leukemia (GVL) activity after female into male allogeneic HCT. This study is registered at http://clinicaltrials.gov as NCT00107354.

High levels of B-cell activating factor in patients with active chronic graft-versus-host disease

PURPOSE

Recent studies suggest that donor B cells as well as T cells contribute to immune pathology in patients with chronic graft-versus-host disease (GVHD). B-cell activating factor (BAFF) promotes survival and differentiation of activated B cells. Thus, we tested whether BAFF correlated with chronic GVHD disease activity and time of onset after allogeneic hematopoietic stem cell transplantation (HSCT).

EXPERIMENTAL DESIGN

Patients who had undergone allogeneic HSCT between 1994 and 2005 for hematologic malignancies were studied. ELISA was used to measure plasma BAFF levels and flow cytometry was used to assess BAFF receptor expression on B cells in patients with or without chronic GVHD.

RESULTS

In 104 patients, BAFF levels were significantly higher in patients with active chronic GVHD compared with those without disease (P = 0.02 and 0.0004, respectively). Treatment with high-dose prednisone (>or=30 mg/d) was associated with reduced BAFF levels in patients with active chronic GVHD (P = 0.0005). Serial studies in 24 patients showed that BAFF levels were high in the first 3 months after HSCT but subsequently decreased in 13 patients who never developed chronic GVHD. In contrast, BAFF levels remained elevated in 11 patients who developed chronic GVHD. Six-month BAFF levels >or=10 ng/mL were strongly associated with subsequent development of chronic GVHD (P < 0.0001). Following transplant, plasma BAFF levels correlated inversely with BAFF receptor expression on B cells (P = 0.01), suggesting that soluble BAFF affected B cells through this receptor.

CONCLUSION

These results suggest that elevated BAFF levels contribute to B-cell activation in patients with active chronic GVHD.

Donor leukocyte infusions for the treatment of relapsed acute leukemia after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (SCT) offers the only hope for cure for many adults with acute leukemia. Unfortunately, many patients relapse and die of their disease even after transplantation. Although in some cases, allogeneic SCT is effective because the intensive conditioning therapy eradicates all malignant cells, it has long been recognized that the adoptive transfer of donor immunity plays a critically important role in the induction and maintenance of remission. Recognition of the graft-versus-leukemia (GVL) effect of allogeneic SCT has prompted attempts at remission re-induction by adoptive immunotherapy with donor lymphocyte infusions (DLIs) in patients with relapsed disease after allogeneic SCT. In some cases, DLI-induced remissions are sustained and patients cured when no other treatment modality was effective. This review discusses the rationale, biology, complications and future applications of DLI in acute leukemia patients after allogeneic SCT.

Molecular typing methods for minor histocompatibility antigens

Minor histocompatibility (H) antigens crucially affect the outcome of human leukocyte antigen-matched allogeneic stem cell transplantation. The number of molecularly identified minor H antigens is rapidly increasing. In parallel, clinical implementation of minor H antigens for immunotherapy has gained significant interest. It is therefore timely to type stem cell transplant recipients and their donors for minor H antigens. Here, we summarize all the currently known methodologies for minor H antigen typing on the genomic and on the RNA level.

Minor histocompatibility antigens as targets for immunotherapy using allogeneic immune reactions

Minor histocompatibility antigens (mHag) were originally identified as antigens causing graft rejection or graft-versus-host disease in human leukocyte antigen (HLA)-matched allogeneic transplantation. Molecular identification has revealed most to be major histocompatibility complex (MHC)-bound short peptide fragments encoded by genes which are polymorphic due to single nucleotide polymorphisms (SNP). Genotypic disparity of SNP between transplantation donors and recipients gives rise to mHag as non-self antigens for both the donor and the recipient. Subsequently, mHag have been explored as immunotherapeutic antigens for use against recurring hematological malignancies after allogeneic hematopoietic cell transplantation (HCT), because mHag expressed only on hematopoietic cells are considered to augment graft-versus-leukemia/lymphoma (GVL) effects without increasing the risk of life-threatening graft-versus-host disease (GVHD). Accumulating evidence suggests that T-cell responses to mHag aberrantly expressed on solid tumor cells are also involved in the eradication of sensitive tumors such as renal cell carcinomas following HCT. Over the past decade, the number of putative GVL-directed mHag has increased to a level that covers more than 30% of the Japanese patient population, so that clinical trials may now be executed in the setting of either vaccination or adoptive immunotherapy. As it is expected that immune responses to alloantigens are more powerful than to tumor antigens mostly derived from overexpressed self-proteins, mHag-based immunotherapy may lead to a new treatment modality for high-risk malignancies following allogeneic HCT.

Minor antigen h60-mediated aplastic anemia is ameliorated by immunosuppression and the infusion of regulatory T cells

Human bone marrow (BM) failure mediated by the immune system can be modeled in mice. In the present study, infusion of lymph node (LN) cells from C57BL/6 mice into C.B10-H2(b)/LilMcd (C.B10) recipients that are mismatched at multiple minor histocompatibility Ags, including the immunodominant Ag H60, produced fatal aplastic anemia. Declining blood counts correlated with marked expansion and activation of CD8 T cells specific for the immunodominant minor histocompatibility Ag H60. Infusion of LN cells from H60-matched donors did not produce BM failure in C.B10 mice, whereas isolated H60-specific CTL were cytotoxic for normal C.B10 BM cells in vitro. Treatment with the immunosuppressive drug cyclosporine abolished H60-specific T cell expansion and rescued animals from fatal pancytopenia. The development of BM failure was associated with a significant increase in activated CD4+CD25+ T cells that did not express intracellular FoxP3, whereas inclusion of normal CD4+CD25+ regulatory T cells in combination with C57BL/6 LN cells aborted H60-specific T cell expansion and prevented BM destruction. Thus, a single minor histocompatibility Ag H60 mismatch can trigger an immune response leading to massive BM destruction. Immunosuppressive drug treatment or enhancement of regulatory T cell function abrogated this pathophysiology and protected animals from the development of BM failure.

Risk assessment in haematopoietic stem cell transplantation: minor histocompatibility antigens

Minor histocompatibility (H) antigens are key molecules in graft-versus-host disease (GvHD) and the graft-versus-tumour effect after allogeneic stem-cell transplantation (SCT). Today, molecular typing methods allow an easy assessment of differences in minor H antigens between patient and donors, so that the GvHD risk in individual patients can be estimated. However, the large number of minor H antigens prevents matching for them to avoid GvHD. Interestingly, mismatching for minor H antigens might improve the outcome of allogeneic SCT. Some minor H antigens are expressed mainly by malignant cells and can therefore serve as excellent targets for cancer immunotherapy. Thus, mismatching for tumour-expressed minor H antigens allows boosting of the curative effect of allogeneic SCT. Current research is elucidating the impact of e.g. donor immunization, immunodominance, or functional expression of minor H antigens on the extent of the GvH response.

Indications of anti-HY immunity in recurrent placental abruption

PROBLEM

Placental abruption is a potential life-threatening condition for both the fetus and the mother, being significantly more common in pregnancies with male fetuses. The pathogenesis of placental abruption remains unknown. However, some recent reports point toward a maternal immune response against the fetus as a possible mechanism. No data exist concerning special characteristics of patients suffering recurrent placental abruptions.

METHOD OF STUDY

Identification of all patients with recurrent placental abruption in a retrospective review of 881 consecutive Caucasian women seen in our tertiary centre for recurrent pregnancy losses between 1986 and 2005. The HLA, DRB1, DRB3, 4, 5 and DQB1 genotypes of patients were compared with relevant controls.

RESULTS

Eight patients were identified with recurrent placental abruption. The patients had a total of 22 abruptions; 18 (82%) in which the fetus died. Seven patients (88%) had first-born boys, and 15 abruptions (68%) involved male fetuses. All patients with a first-born boy, except one, had HLA-class II alleles known to restrict CD4+ T-cell responses against male-specific minor histocompatibility (HY)-antigens (HLA-DRB1*15, HLA-DRB3*0301 and HLA-DQB1*05). Haplotypes with these HLA-alleles constituted 64% of the patients' haplotypes compared to 28% of those of the controls (p=0.009). Furthermore, 43% of the patients were homozygous for these haplotypes compared to 5% of controls (p=0.023).

CONCLUSION

We have found that recurrent placental abruption is exclusively almost preceded by the birth of a boy and the majority of patients have HLA-class II known to restrict CD4 T-cell reactions against HY-antigens. This indicates that maternal immunological responses against HY-antigens play a role in recurrent placental abruption.

Serum from mice immunized in the context of Treg inhibition identifies DEK as a neuroblastoma tumor antigen

BACKGROUND

We have developed a cell-based vaccine that features the expression of both CD80 and CD86 on the surface of a murine neuroblastoma cell line. The cellular immunity induced by this vaccine is enhanced by treatment with antibody that interferes with T-regulatory cell (Treg) function and we report here that immunization combined with interfering with Treg function also produces a profound serological effect. Serum from mice immunized with our cell-based vaccine in the context of Treg blockade was used to screen a cDNA expression library constructed from the parental neuroblastoma tumor cell line, AGN2a.

RESULTS

Serum from mice vaccinated in the context of Treg blockade identified a number of potentially oncogenic transcripts that may serve as important immune targets in a tumor-derived cDNA library screen. This novel approach identified far more candidates than could be seen with serum derived from vaccine-treated only, Treg-depleted only, or tumor-bearing mice. The most commonly identified tumor-associated antigen, using serum from immunized and Treg-depleted mice, was the DEK oncogene. Altered expression of the DEK oncogene has been implicated in a number of human cancers. Importantly, we were able to demonstrate that the DEK oncogene also induces a T cell response.

CONCLUSION

The use of post-vaccine immune serum in this report differs from previous approaches where serum collected at the time of cancer onset or diagnosis and was used for tumor antigen identification. We hypothesize that the use of diagnostic serum samples may be inadequate for the clinical translation of this approach, and that identification of protective immunogenic tumor antigens may require the use of serum from post-treatment or vaccinated subjects. The identification of DEK as a tumor-associated antigen capable of eliciting a T cell response validates our experimental approach and argues for the antigens we have identified here to be evaluated as targets of effector immunity and as vaccine candidates.

Altered Toll-like receptor 9 responses in circulating B cells at the onset of extensive chronic graft-versus-host disease

B cells appear to play a role in chronic graft-versus-host disease (cGVHD) as shown in murine models and the success of anti-CD20 B cell antibody treatment in humans. Recent studies have shown that immunostimulatory microbial CpG-DNA splenic responses were enhanced in murine GVHD. We hypothesized that CpG-induced B cell responses are increased in human cGVHD. Newly diagnosed cGVHD patients enrolled on the COG protocol ASCT0031 were divided into early (3-8 months postblood and marrow transplant [BMT]) and late (> or =9 months post-BMT) onset groups and compared to time-matched control BMT patients. A significantly greater percentage of phosphorothioate (PS)-modified CpG stimulated B cells from cGVHD patients demonstrated an increased expression of CD86 compared to controls (P = .0004). This response had a significant correlation between B cell TLR9 expression (r(2) = 0.65; P = .002) and CD86 upregulation using the entirely TLR9-dependent native phosphodiester CpG (P = .003). The PS-modified CpG response at 2 months after initiation of cGVHD therapy demonstrated a trend toward predicting therapeutic response at 9 months post-BMT (P = .07). These findings suggest that an increased number of B cells, primed for a TLR9 response, may play a role in the pathophysiology of cGVHD.

Minor histocompatibility antigen DDX3Y induces HLA-DQ5-restricted T cell responses with limited TCR-Vbeta usage both in vivo and in vitro

In vitro stimulation of human female T cells with male HLA-identical dendritic cells resulted in the generation of HLA-DQB1*0501/0502-restricted minor histocompatibility H-Y antigen-specific CD4(+) T cell clones. Two clones generated from different HLA-identical pairs were analyzed. Use of HLA-DQ5-expressing female Epstein-Barr virus transformed B lymphoblastoid cell lines transfected with various H-Y genes and loaded with overlapping peptides demonstrated that both T cell clones are specific for a peptide encoded by DDX3Y. Previously, an HLA-DQ5-restricted T cell clone specific for the same peptide was isolated from a patient with graft-versus-host disease. Thus, we compared the T cell receptor (TCR) rearrangements of the 2 in vitro generated T cell clones and the ex vivo isolated T cell clone. All 3 clones shared the same TCRBV5-4* gene segment and 2 of 3 clones also used similar TCR-Valpha segments. Our results suggest that T cells recognizing the HLA-DQ5/DDX3Y T cell epitope might be characterized by a relatively limited TCR-beta repertoire. The differences in the junctional TCR-beta region had no effect on the antigen specificity, but altered the capacity of the TCR to distinguish the HLA-DQ5/DDX3Y complex from its allelic counterpart. The results also demonstrate that in vitro stimulation of T cells with allogeneic HLA-identical dendritic cells may facilitate the characterization of in vivo, potentially relevant HLA class II-restricted minor H epitopes.

Donor leukocyte infusions in myeloid malignancies: new strategies

Donor leukocyte infusion (DLI) provides direct and potent graft-versus-leukemia (GVL) activity to treat relapse after allogeneic stem-cell transplantation. DLI is dramatically effective for relapsed chronic myelogenous leukemia (CML), but has been less effective for relapse of other myeloid malignancies. Nevertheless, most recipients of DLI for relapsed CML, and many patients with relapsed acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS), will experience prolonged remissions and probable cure. Graft-versus-host disease remains the major complication of DLI. New strategies for GVL induction explore novel dosing regimens and both methods of enhancing GVL activity of donor T cells and of minimizing toxicity from graft-versus-host disease. Ultimately, the identification of the effector cells and target antigens for GVL induction will lead to the use of tumor-specific adoptive immunotherapy to both prevent and treat relapse with minimal toxicity. Although many issues remain unsettled, the potential to harness the graft-versus-leukemia activity of allogeneic donor cells provides a powerful new paradigm for the immunotherapy of cancer.

A uniform genomic minor histocompatibility antigen typing methodology and database designed to facilitate clinical applications

BACKGROUND

Minor Histocompatibility (H) antigen mismatches significantly influence the outcome of HLA-matched allogeneic stem cell transplantation. The molecular identification of human H antigens is increasing rapidly. In parallel, clinical application of minor H antigen typing has gained interest. So far, relevant and simple tools to analyze the minor H antigens in a quick and reliable way are lacking.

METHODOLOGY AND FINDINGS

We developed a uniform PCR with sequence-specific primers (PCR-SSP) for 10 different autosomal minor H antigens and H-Y. This genomic minor H antigen typing methodology allows easy incorporation in the routine HLA typing procedures. DNA from previously typed EBV-LCL was used to validate the methodology. To facilitate easy interpretation for clinical purposes, a minor H database named dbMinor (http://www.lumc.nl/dbminor) was developed. Input of the minor H antigen typing results subsequently provides all relevant information for a given patient/donor pair and additional information on the putative graft-versus-host, graft-versus-tumor and host-versus-graft reactivities.

SIGNIFICANCE

A simple, uniform and rapid methodology was developed enabling determination of minor H antigen genotypes of all currently identified minor H antigens. A dbMinor database was developed to interpret the genomic typing for its potential clinical relevance. The combination of the minor H antigen genomic typing methodology with the online dbMinor database and applications facilitates the clinical application of minor H antigens anti-tumor targets after stem cell transplantation.

Allorecognition of an HLA-A*01 Aberrant Allele by an HLA Identical Family Member Carrying the HLA-A*0101 Allele

We identified and characterized an HLA-A1 aberrant allele (A*0118N) resulting from a novel molecular mechanism; this allele was present in an unusually informative family with a near identical parental HLA haplotype (c d) differing only by one nucleotide substitution in one HLA-A allele, A*0118N, of the maternal HLA haplotype (c) and not of the paternal HLA haplotype (a). Although serologic HLA typing showed a "blank," DNA molecular HLA typing detected a HLA-A*0118N allele. Sequence based typing identified the substitution of guanine by cytosine at the nucleotide position 215, which resulted in the replacement of arginine by proline at position 48 of the HLA-A1 H chain. The loss of surface protein expression was also found by FACS analysis. Isoelectric-focusing analysis detected a HLA-A H chain with a unique isoelectric-focusing pattern, which does not associate with the L chain (beta(2)-microglobulin). These results suggest that the residue 48-containing interaction site on the alpha(1) domain plays a critical role in the association between HLA class I H chain and beta(2)-microglobulin. Functional studies showed that the T cells of the propositus (HLA haplotypes c d) carrying this null allele recognized its wild-type counterpart, HLA-A*010101, in her HLA-identical son that carries the HLA-A*0101 heterodimer. This is the first example of the generation of cytotoxic T cells in the absence of proliferation of CD4(+) T cells (mixed lymphocyte culture) and the description of an aberrant allele, A*0118N, that may behave as a minor histocompatibility Ag, with implications in allorecognition by cytolytic T cells in solid organ and stem cell transplantation.

Beyond HLA: the significance of genomic variation for allogeneic hematopoietic stem cell transplantation

The last 2 years have seen much excitement in the field of genetics with the identification of a formerly unappreciated level of “structural variation” within the normal human genome. Genetic structural variants include deletions, duplications, and inversions in addition to the recently discovered, copy number variants. Single nucleotide polymorphisms are the most extensively evaluated variant within the genome to date. Combining our knowledge from these studies with our rapidly accumulating understanding of structural variants, it is apparent that the extent of genetic dissimilarity between any 2 individuals is considerable and much greater than that which was previously recognized. Clearly, this more diverse view of the genome has significant implications for allogeneic hematopoietic stem cell transplantation, not least in the generation of transplant antigens but also in terms of individual susceptibility to transplant-related toxicities. With advances in DNA sequencing technology we now have the capacity to perform genome-wide analysis in a high throughput fashion, permitting a detailed genetic analysis of patient and donor prior to transplantation. Understanding the significance of this additional genetic information and applying it in a clinically meaningful way will be one of the challenges faced by transplant clinicians in the future.

Rituximab for steroid-refractory chronic graft-versus-host disease

B cells may be implicated in the pathophysiology of chronic graft-versus-host disease (GVHD), as evidenced by antibody production against sex-mismatched, Y chromosome-encoded minor HLA antigens in association with chronic GVHD. We therefore designed a phase 1/2 study of anti-B-cell therapy with rituximab in steroid-refractory chronic GVHD. Twenty-one patients were treated with 38 cycles of rituximab. Rituximab was tolerated well, and toxicity was limited to infectious events. The clinical response rate was 70%, including 2 patients with complete responses. Responses were limited to patients with cutaneous and musculoskeletal manifestations of chronic GVHD and were durable through 1 year after therapy. The median dose of prednisone among treated subjects fell from 40 mg/day to 10 mg/day, 1 year after rituximab therapy (P < .001). A chronic GVHD symptom score improved in the majority of treated patients. Antibody titers against Y chromosome-encoded minor HLA antigens fell and remained low, whereas titers against infectious antigens (EBV, tetanus) remained stable or rose during the treatment period. We conclude that specific anti-B-cell therapy with rituximab may be beneficial for patients with steroidrefractory chronic GVHD. This trial was registered at www.clinicaltrials.gov as #NCT00136396.

Minor histocompatibility antigens: from transplantation problems to therapy of cancer

The idea of transferring healthy marrow for the therapeutic treatment of the various diseases of the blood and of the immune system made a significant contribution to controlling diseases and to advancing modern clinical sciences. The first series of bone marrow transplantations in the 1960s were confronted with severe complications. It became clear that matching for the human leukocyte antigen (HLA) system between donor and recipient significantly improved the clinical results. Nonetheless, an unacceptable percentage of severe complications remained that is mainly attributable to non-HLA histocompatibility systems, i.e., minor histocompatibility antigens. Observations in the 1970s that minor histocompatibility antigens cause serious problems in human bone marrow transplantation laid the basis for their use as curative antigens in stem cell transplantation to date. Thus, the allo-immune T cell activities caused by minor histocompatibililty antigen disparities between HLA-matched donor and recipient can now be applied for the benefit of the transplant patient.

Shared biology of GVHD and GVT effects: Potential methods of separation

The difficult separation of clinical graft-versus-tumor (GVT) effects from graft-versus-host disease (GVHD) reflects their shared biology. Experimental approaches to mediate GVT effects while limiting GVHD include: (1) allograft T cell depletion followed by immune enhancement; (2) modulation of T cell dose or T cell subset composition; (3) donor lymphocyte infusion; (4) reduced-intensity host preparation; (5) modulation of Th1/Th2 and Tc1/Tc2 cell balance; (6) cytokine therapy or neutralization; (7) T regulatory cell therapy; (8) co-stimulatory pathway modulation; (9) chemokine pathway modulation; (10) induction of antigen-specific T cells; (11) alloreactive NK cell therapy; and (12) targeted pharmaceutical inhibition of proteosome, mammalian target of rapamycin, and histone deacetylase pathways. Clearly, a multitude of approaches exist that hold promise for separating GVT effects from GVHD. Future success in this endeavor will require a strong commitment towards translational research and continued advances in cell, vaccine, cytokine, monoclonal antibody, and targeted molecular therapy.

Chronic graft-versus-host disease

PURPOSE OF REVIEW

Chronic graft-versus-host disease is an important cause of late morbidity and mortality after allogeneic stem cell transplantation. With the renewed interest in its pathophysiology and treatment, this review discusses recent clinical and laboratory advances in this disease. Advances in pathophysiology, the relationship between chronic graft-versus-host disease and relapse incidence, and recent developments in the prophylaxis, initial therapy, and therapy for refractory disease are discussed.

RECENT FINDINGS

A better understanding of the pathophysiology of chronic graft-versus-host disease, including the potential role of a coordinated B-cell and T-cell response, is demonstrated. Corticosteroids and cyclosporine or tacrolimus remain the standard as initial therapy. This combination is effective in the majority of affected patients, although therapy is often required for longer than 1 year. Although no strategy has been demonstrated to be effective in specifically preventing chronic graft-versus-host disease, several drugs have recently been demonstrated to be effective therapeutic agents for steroid-refractory disease. Agents such as mycophenolate mofetil, sirolimus, and rituximab have demonstrated response rates of greater than 60% in patients with steroid-refractory disease.

SUMMARY

Renewed interest and understanding of chronic graft-versus-host disease have led to novel treatment strategies for steroid-refractory disease. A focus on the initial therapy and prophylaxis against chronic graft-versus-host disease is now warranted.

Possible involvement of allogeneic antigens recognised by donor-derived CD4 cytotoxic T cells in selective GVL effects after stem cell transplantation of patients with haematological malignancy

Cytotoxic T lymphocyte (CTL) lines specific for allogeneic antigens were generated by in vitro stimulation of donor-derived peripheral blood mononuclear cells obtained from patients who received human leucocyte antigen (HLA)-matched allogeneic haematopoietic stem cell transplantation (HSCT). One of the allogeneic antigen-specific CD4+ CTL lines, CTL-A, generated from a patient with T cell acute lymphoblastic leukaemia, recognised HLA-DPB1*0501-positive Epstein-Barr virus-immortalised human B cell line (EBV-B cells), phytohaemagglutinin blasts and leukaemia cells, but not interferon-gamma (IFN-gamma) treated HLA-DPB1*0501-positive fibroblasts, indicating that this CD4+ T-cell line recognised a minor histocompatibility antigen (mHa) that is preferentially expressed in haematopoietic cells in an HLA-DPB1*0501-restricted manner. The other CD4+ CTL line, CTL-B, generated from a patient with chronic myeloid leukaemia, recognised mismatched HLA-DQB1*0303 on EBV-B cells and phytohaemagglutinin (PHA) blasts. Interestingly, this CTL line did not recognise IFN-gamma-treated recipient's skin fibroblasts, as HLA-DQ was merely upregulated even after IFN-gamma stimulation in non-haematopoietic cells including fibroblasts, endothelial cells and hepatocytes. These results suggest that these CD4 positive CTLs, specific for mismatch HLA-DQ and mHa that are preferentially expressed on haematopoietic cells, may play an important role in induction of selective graft-versus-leukaemia effect without development of graft-versus-host disease after allogeneic HSCT.

Effector cells derived from host CD8 memory T cells mediate rapid resistance against minor histocompatibility antigen-mismatched allogeneic marrow grafts without participation of perforin, Fas ligand, and the simultaneous inhibition of 3 tumor necrosis factor family effector pathways

Reduced-intensity conditioning regimens for transplant recipients have heightened awareness of immunologic resistance to allogeneic bone marrow transplants (BMT). Although T cell-mediated cytotoxicity has been assumed to play a role in the resistance against donor allogeneic hematopoietic stem and progenitor cell grafts, several studies have reported relatively unimpaired resistance by recipients who lack perforin, Fas ligand (FasL), and other cytotoxic mediators. This study compared the early kinetics of T cell-mediated resistance in B6 (H2b) cytotoxically normal versus deficient recipients after transplantation with major histocompatibility complex-matched, minor histocompatibility antigen (MiHA)-mismatched allogeneic marrow grafts. Wild-type B6 or cytotoxic double-deficient perforin-/-/gld+/+ (B6-cdd) mice were sensitized against major histocompatibility complex-matched BALB.B or C3H.SW (H2b) MiHA and transplanted with a high dose (1 x 10(7)) of T cell-depleted bone marrow. CD8 T memory cells were shown to be present in recipients before BMT, and anti-CD8 monoclonal antibody infusion abolished resistance, thus demonstrating that CD8 T cells are the host effector population. Donor-committed and high proliferative potential progenitor numbers were markedly diminished by 48 hours after transplantation in both wild-type B6 and B6-cdd anti-donor MiHA-sensitized recipients. These observations indicate that the resistance pathway used in the cytotoxic deficient mice was both potent and rapidly induced--consistent with a CD8 memory T-cell response. To examine the role of Tumor necrosis factor-like weak inducer of apoptosis (TWEAK)- and TL1A-mediated cytotoxicity in this strong resistance, newly generated monoclonal antibodies specific for these ligands were administered to B6-cdd recipients sensitized to donor antigens. Recipients of syngeneic B6-gfp bone marrow exhibited significant donor colony-forming unit numbers after BMT. In contrast, low or absent colony-forming unit levels were detected in allogeneic recipients, including those that lacked perforin and FasL and that received anti-TWEAK, anti-tumor necrosis factor-related apoptosis-inducing ligand, and anti-TL1A monoclonal antibodies. These findings extend previous observations by demonstrating the existence of a rapidly effected resistance pathway mediated by memory CD8 effector T cells independent of the 2 major pathways of cytotoxicity. Together with previous findings, these results support the notion that effector cells derived from memory CD8 T-cell populations can mediate strong resistance against donor allogeneic MiHA-disparate hematopoietic engraftment by using a mechanism that is independent of the contribution of perforin, FasL, and the known death ligand receptor pathways.

The sentinel within: exploiting the immune system for cancer biomarkers

The release of proteins from tumors triggers an immune response in cancer patients. These tumor antigens arise from several mechanisms including tumor-specific alterations in protein expression, mutation, folding, degradation, or intracellular localization. Responses to most tumor antigens are rarely observed in healthy individuals, making the response itself a biomarker that betrays the presence of underlying cancer. Antibody immune responses show promise as clinical biomarkers because antibodies have long half-lives in serum, are easy to measure, and are stable in blood samples. However, our understanding of the specificity and the impact of the immune response in early stages of cancer is limited. The immune response to cancer, whether endogenous or driven by vaccines, involves highly specific T lymphocytes (which target tumor-derived peptides bound to self-MHC proteins) and B lymphocytes (which generate antibodies to tumor-derived proteins). T cell target antigens have been identified either by expression cloning from tumor cDNA libraries, or by prediction based on patterns of antigen expression ("reverse immunology"). B cell targets have been similarly identified using the antibodies in patient sera to screen cDNA libraries derived from tumor cell lines. This review focuses on the application of recent advances in proteomics for the identification of tumor antigens. These advances are opening the door for targeted vaccine development, and for using immune response signatures as biomarkers for cancer diagnosis and monitoring.

A class II-restricted cytotoxic T-cell clone recognizes a human minor histocompatibility antigen with a restricted tissue distribution

Following a human leucocyte antigen (HLA)-identical allogeneic stem cell transplantation (allo-SCT), minor histocompatibility antigens (mHags) play an important role in the induction of graft-versus-leukaemia (GvL) and graft-versus-myeloma (GvM). Many mHags show ubiquitous tissue expression and are associated with GvL and graft-versus-host disease. Here we describe a cytotoxic CD4(+) T lymphocyte line and a cytotoxic, CD4(+) T cell clone (CTC), 3AB11, which recognized a tissue-restricted mHag. This CTC was isolated from a multiple myeloma patient with clinical GvM following an HLA-matched allo-SCT. CTC 3AB11 was activated in a HLA-DP*0401 restricted fashion and the antigen was expressed by 27% of HLA-DP*0401 positive Epstein-Barr virus (EBV)-transformed B-cell lines (EBV-B). Tissue distribution analysis of antigen 3AB11 showed it to be expressed by patient-derived EBV-transformed B cell lines (EBVp), the myeloma plasma cell-line UM9 and monocytes. It was weakly expressed by peripheral blood-derived phytohaemagglutinin-induced T-cell blasts and absent on CD40L stimulated peripheral B (CD40L B) cells and stromal cells. The relatively high prevalence of the HLA class II-restricted 3AB11 antigen, together with its apparent haematopoietic-restricted expression, makes it an antigen of interest for cellular immunotherapy.

Differential effects of granulocyte colony-stimulating factor on marrow- and blood-derived hematopoietic and immune cell populations in healthy human donors

A recent phase III trial comparing granulocyte colony-stimulating factor (G-CSF)-stimulated bone marrow (G-BM) and G-CSF-mobilized peripheral blood (G-PB) in matched sibling allograft recipients showed that G-BM produced a similar hematologic recovery but a reduced incidence of extensive chronic graft-versus-host disease, indicating differences in the cell populations infused. As a first step toward identifying these differences, we treated a group of healthy adult humans with 4 daily doses of G-CSF 10 microg/kg and monitored the effects on various hematopoietic and immune cell types in the PB and BM over 12 days. G-CSF treatment caused rapid and large but transient increases in the number of circulating CD34+ cells, colony-forming cells, and long-term culture-initiating cells and in the short-term repopulating activity detectable in nonobese diabetic/severe combined immunodeficiency/beta2-microglobulin-null mice. Similar but generally less marked changes occurred in the same cell populations in the BM. G-CSF also caused transient perturbations in some immune cell types in both PB and BM: these included a greater increase in the frequency of naive B cells and CD123+ dendritic cells in the BM. The rapidity of the effects of G-CSF on the early progenitor activity of the BM provides a rationale for the apparent equivalence in rates of hematologic recovery obtained with G-BM and G-PB allotransplants. Accompanying effects on immune cell populations are consistent with a greater ability of G-BM to promote tolerance in allogeneic recipients, and this could contribute to a lower rate of chronic graft-versus-host disease.

B Cell Allogeneic Responses after Hematopoietic Cell Transplantation: Is It Time to Address this Issue?

To date, B cell responses have retained less attention than T, natural killer or dendritic cell responses in the alloreactive conflict after allogeneic hematopoietic cell transplantation (HCT). Here, we discuss recent clinical and experimental data supporting a role of allogeneic B cell responses in graft-host interactions after HCT. We report results in a murine model of reduced intensity conditioning transplantation (RICT) showing that host B cells can be involved in chronic graft-versus-host disease occurrence. We also describe the control of antidonor alloresponses by intravenous simultaneous infusion of apoptotic cells with allogeneic hematopoietic grafts.

A novel HLA-A*3303-restricted minor histocompatibility antigen encoded by an unconventional open reading frame of human TMSB4Y gene

Female-to-male hemopoietic stem cell transplantation (HSCT) elicits T cell responses against male-specific minor histocompatibility (H-Y) Ags encoded by the Y chromosome. All previously identified H-Y Ags are encoded by conventional open reading frames, but we report in this study the identification of a novel H-Y Ag encoded in the 5'-untranslated region of the TMSB4Y gene. An HLA-A*3303-restricted CD8(+) CTL clone was isolated from a male patient after an HSCT from his HLA-identical sister. Using a panel of cell lines carrying Y chromosome terminal deletions, a narrow region controlling the susceptibility of these target cells to CTL recognition was localized. Minigene transfection and epitope reconstitution assays identified an 11-mer peptide, EVLLRPGLHFR, designated TMSB4Y/A33, whose first amino acid was located 405 bp upstream of the TMSB4Y initiation codon. Analysis of the precursor frequency of CTL specific for recipient minor histocompatibility Ags in post-HSCT peripheral blood T cells revealed that a significant fraction of the total donor CTL response in this patient was directed against the TMSB4Y epitope. Tetramer analysis continued to detect TMSB4Y/A33-specific CD8(+) T cells at least up to 700 days post-HSCT. This finding underscores the in vivo immunological relevance of minor histocompatibility Ags derived from unconventional open reading frame products.

Antibody responses to H-Y minor histocompatibility antigens correlate with chronic graft-versus-host disease and disease remission

Minor histocompatibility antigens (mHAs) are known targets of donor T cells after allogeneic hematopoietic stem cell transplantation (HSCT). In contrast, B-cell responses to mHAs have not been extensively characterized and the clinical significance of antibodies to mHAs is unknown. We tested 121 patients who underwent HSCT and 134 healthy donors for immunoglobulin G (IgG) antibodies against 5 mHAs encoded by genes on the Y chromosome (DBY, UTY, ZFY, RPS4Y, and EIF1AY). Antibodies to at least one H-Y protein developed in 52% of male patients with female donors compared with 8.7% of male patients with male donors (P < .0001), and in 41.4% of healthy females compared with 7.8% of healthy males (P < .0001). H-Y antibodies develop 4 to 12 months after transplantation and persist for long periods. The clinical significance of H-Y antibodies was characterized in 75 male patients with hematologic malignancies who received stem cells from female donors (F --> M HSCT). The presence of H-Y antibodies correlated with chronic graft-versus-host disease (GVHD) by univariate (odds ratio [OR] = 15.5; P < .0001) and multivariable logistic regression analysis (OR = 56.5; P < .0001). Antibody response to Y-chromosome encoded histocompatibility antigens (H-Y antigens) was also associated with maintenance of disease remission (P < .0001). B cells may provide a new target for immune intervention in chronic GVHD.