Cellular and cytokine effectors of acute graft versus host disease

Graft-versus-host-disease (GVHD) is the major complication of allogeneic Bone Marrow Transplant (BMT) and Older BMT recipients are at greater risk for acute graft-versus-host-disease. Using well-characterized murine BMT models we have explored the mechanisms of increased GVHD in older recipients. GVHD mortality and morbidity, as well as pathologic and biochemical indices were all worse in old recipients. Donor T cell responses were significantly increased in old recipients both in vivo and in vitro when stimulated by antigen-presenting cells (APCs) from old mice. In a haploidential GVHD model, CD4+ donor T cells mediated more severe GVHD in old mice. We confirmed the role of aged APCs in GVHD using B6D2FI BM chimeras created with either old or young BM. APCs from these mice also stimulated greater responses from allogeneic cells in vitro. We also evaluated whether alloantigen expression on host target epithelium is essential for tissue damage induced by GVHD in mouse models. In bone marrow chimeras recipients in which either MHC II or MHC I alloantigen was expressed only on APCs, we found that acute GVHD does not require alloantigen expression on host target epithelium and that neutralization of tumor necrosis factor-alpha and interleukin-1 prevents acute GVHD. These results suggest new strategies for the prevention and treatment of this toxic complication of BMT.

Acute graft-versus-host disease does not require alloantigen expression on host epithelium

Alloantigen expression on host antigen-presenting cells (APCs) is essential to initiate graft-versus-host disease (GvHD); therefore, alloantigen expression on host target epithelium is also thought to be essential for tissue damage. We tested this hypothesis in mouse models of GvHD using bone-marrow chimeras in which either major histocompatibility complex class I or class II alloantigen was expressed only on APCs. We found that acute GvHD does not require alloantigen expression on host target epithelium and that neutralization of tumor necrosis factor-alpha and interleukin-1 prevents acute GvHD. These results pertain particularly to CD4-mediated GvHD but also apply, at least in part, to CD8-mediated GvHD. These results challenge current paradigms about the antigen specificity of GvHD effector mechanisms and confirm the central roles of both host APCs and inflammatory cytokines in acute GvHD.

Graft-versus-host disease in the absence of the spleen after allogeneic bone marrow transplantation

BACKGROUND

The spleen is considered to be an important secondary lymphoid organ where acute graft-versus-host disease (GVHD) is initiated by donor T cells that recognize host alloantigens after allogeneic bone-marrow transplantation (BMT). The influence of splenectomy on the development of GVHD prior to BMT has yet to be determined.

METHODS

The mortality and severity of murine GVHD of unsplenectomized, splenectomized, and sham-operated recipients of allogeneic BMT were compared in a blinded fashion. Serum levels of interferon (IFN)-gamma were measured 7 days after BMT, as an index of systemic donor T-cell responses.

RESULTS

Mortality and morbidity of acute GVHD were not significantly affected by splenectomy in a major histocompatibility complex (MHC)-mismatched, CD4-driven murine GVHD model and a minor histocompatibility antigen (MiHA)-mismatched, CD8-driven GVHD model. Serum levels of IFN-gamma also were not different between the groups.

CONCLUSION

GVHD can readily develop after allogeneic BMT, even in the absence of the spleen, in these mouse models.

Enhanced allostimulatory activity of host antigen-presenting cells in old mice intensifies acute graft-versus-host disease

Older bone marrow transplantation (BMT) recipients are at heightened risk for acute graft-versus-host disease (GVHD) after allogeneic BMT, but the causes of this association are poorly understood. Using well-characterized murine BMT models we have explored the mechanisms of increased GVHD in older mice. GVHD mortality, morbidity, and pathologic and biochemical indices were all worse in old recipients. Donor T cell responses were significantly increased in old recipients both in vivo and in vitro when stimulated by antigen-presenting cells (APCs) from old mice, which also secreted more TNF-alpha and IL-12 after LPS stimulation. In a B6 --> B6D2F1 model, CD4(+) donor T cells but not CD8(+) T cells mediated more severe GVHD in old mice. We confirmed the role of aged APCs in GVHD using B6D2F1 BM chimeras created with either old or young BM. Four months after chimera creation, allogeneic BMT from B6 donors caused significantly worse GVHD in old BM chimeras. APCs from these mice also stimulated greater responses from allogeneic cells in vitro. These data demonstrate a hitherto unsuspected mechanism of amplified donor T cell responses by aged allogeneic host APCs that increases acute GVHD in aged recipients in this BMT model.

Pilot study of iodine-131-metaiodobenzylguanidine in combination with myeloablative chemotherapy and autologous stem-cell support for the treatment of neuroblastoma

PURPOSE

The survival for children with relapsed or metastatic neuroblastoma remains poor. More effective regimens with acceptable toxicity are required to improve prognosis. Iodine-131-metaiodobenzylguanidine ((131)I-MIBG) selectively targets radiation to catecholamine-producing cells, including neuroblastoma cells. A pilot study was performed to examine the feasibility of a novel regimen combining (131)I-MIBG and myeloablative chemotherapy with autologous stem-cell rescue.

PATIENTS AND METHODS

Twelve patients with neuroblastoma were treated after relapse (five patients) or after induction therapy (seven patients). Eight patients had metastatic and four had localized disease at the time of therapy. All patients received (131)I-MIBG 12 mCi/kg on day -21, followed by carboplatin (1,500 mg/m(2)), etoposide (800 mg/m(2)), and melphalan (210 mg/m(2)) administered from day -7 to day -4. Autologous peripheral-blood stem cells or bone marrow were infused on day 0. Engraftment, toxicity, and response rates were evaluated.

RESULTS

The (131)I-MIBG infusion and myeloablative chemotherapy were both well tolerated. Grade 2 to 3 oral mucositis was the predominant nonhematopoietic toxicity, occurring in all patients. The median times to neutrophil (> or = 0.5 x 10(3)/microL) and platelet (> or = 20 x 10(3)/microL) engraftment were 10 and 28 days, respectively. For the eight patients treated with metastatic disease, three achieved complete response and two had partial responses by day 100 after transplantation.

CONCLUSION

Treatment with (131)I-MIBG in combination with myeloablative chemotherapy and hematopoietic stem-cell rescue is feasible with acceptable toxicity. Future study is warranted to examine the efficacy of this novel therapy.

Flt3 ligand therapy for recipients of allogeneic bone marrow transplants expands host CD8 alpha(+) dendritic cells and reduces experimental acute graft-versus-host disease

Recent evidence suggests that dendritic cells (DCs) can regulate and amplify immune responses. Flt3 ligand (FL)-derived DC function was tested as a stimulator of allogeneic lymphocytes in vitro and in vivo. Treatment of mice with FL dramatically expanded DC number, but DCs isolated from FL-treated mice (FL DCs) were poor stimulators of allogeneic T-cell responses in vitro. Further activation of FL DCs did not restore their stimulatory ability, and FL DCs did not suppress the stimulation of the allogeneic T cells by normal DCs. FL treatment significantly increased the CD8 alpha(+) DC subset, which appeared to be the reason for their poor stimulatory capacity. These observations were confirmed in vivo using a mouse model of acute graft-versus-host disease (GVHD) wherein host DCs play a critical role. FL treatment of recipients before allogeneic bone marrow transplantation dramatically suppressed donor T-cell responses to host antigens, thereby reducing GVHD mortality (P <.01). These data represent a novel strategy that alters host DCs and reduces acute GVHD.

A phase I/II double-blind, placebo-controlled study of recombinant human interleukin-11 for mucositis and acute GVHD prevention in allogeneic stem cell transplantation

Interleukin-11 (IL-11) decreases cytokine release and increases survival in murine BMT models. In these systems, it reduces gut permeability, partially polarizes T cells to a Th2 phenotype, down-regulates IL-12, prevents mucositis, and accelerates recovery of oral and bowel mucosa. We conducted a randomized double-blind pilot study of rhIL-11 administered with cyclosporine/MTX prophylaxis after cytoxan/TBI conditioning and allogeneic stem cell transplantation for hematologic malignancies. Patients received rhIL-11, 50 microg/kg subcutaneously daily or placebo in a 3:1 ratio. Treatment was administered prior to the start of conditioning and continued up to 21 days. The study was designed to assess safety with stopping rules for cardiac arrhythmias and mortality. Although projected to accrue 20 patients, only 13 patients (10 IL-11, three placebo) were enrolled because the early stopping rule for mortality was triggered. Of 10 evaluable patients who received IL-11, four died by day 40 and one died on day 85. Deaths were attributable to transplant-related toxicity. One of three placebo recipients died of suicide, the other two are alive. Patients receiving IL-11 had severe fluid retention and early mortality, making it impossible to determine whether IL-11 given in this schedule can reduce the rate of GVHD. Grade B-D acute GVHD occurred in two of eight evaluable patients on IL-11 and one of three patients on placebo. The primary adverse events of the study were severe fluid retention resistant to diuresis (average weight gain 9 +/- 4%) and multiorgan failure in five of 10 evaluable patients. The use of IL-11 as GVHD prophylaxis in allogeneic transplantation cannot be recommended as administered in this trial.

Donor leukocyte infusion from immunized donors increases tumor vaccine efficacy after allogeneic bone marrow transplantation

Donor T cells play a critical role in mediating both harmful graft-versus-host disease (GVHD) and beneficial graft-versus-tumor effect after allogeneic bone marrow transplantation (BMT). We have recently demonstrated a novel treatment strategy to stimulate specific antitumor activity with preservation of tolerance to host antigens after T cell-depleted allogeneic BMT by vaccination of recipients with irradiated B16 melanoma cells engineered to secrete granulocyte-macrophage colony-stimulating factor. In this murine system, donor leukocyte infusion from a donor immunized with the recipient-derived B16 vaccines enhanced clinical activity of tumor vaccines without exacerbating GVHD. CD4(+) T cells are essential for this enhancement. In vitro analysis of splenocytes from donor leukocyte infusion donor mice demonstrated that immunization of donors with the recipient-derived B16 vaccines elicited potent T-cell proliferation and cytokine responses specific to B16 antigens. These results demonstrate that immunization of donors with recipient-derived tumor vaccines preferentially induces tumor-specific T-cell responses and that vaccination of both donors and recipients can generate potent antitumor immunity without exacerbating GVHD. This strategy has important implications to prevent recurrence of malignancies after BMT.

Understanding the alloresponse: new approaches to graft-versus-host disease prevention

Graft-versus-host disease (GVHD) has been the primary limitation to the wider application of allogeneic bone marrow transplantation (BMT). GVHD occurs when donor T cells react to host antigens on antigen-presenting cells (APCs) and attack host tissues, with sequential activation of donor T cells and monocytes/macrophages. The net effects of dysregulated cytokine production in this complex system are the severe inflammatory manifestations that we recognize as clinical acute GVHD. Long-term outcomes are also adversely affected by chronic GVHD, which has distinctive clinical and pathologic manifestations that mimic autoimmune disease, although its exact pathogenesis remains ambiguous. The ultimate goal for preventing GVHD is the induction of specific tolerance to host antigens, thereby maintaining favorable aspects of donor immunity. Tolerance may be achieved by costimulatory blockade, deletion of activated cells, suppression by regulatory T cells, and immune deviation. This report will focus on these mechanisms as they relate to the pathophysiology of acute GVHD.