Selective elimination of alloreactivity in vitro and in vivo while sparing other T-cell-mediated immune responses.

Selective elimination of alloreactive cells was carried out in the set-up of T-cell-mediated immunotherapy in an effort to gain the benefits of hematopoietic allogeneic transplantation while reducing the risk of GVHD. Low MW chemical compounds were screened for their effect on T-cell-mediated immune responses of murine- and human-derived lymphocytes. Selected compounds were further tested in secondary MLR assays in which sensitization to alloantigens was carried out in vitro, in the presence or absence of a given compound, followed by exposure to related and unrelated alloantigens or T-cell mitogenic stimulation.

Immunotherapy in high-risk chemotherapy-resistant patients with metastatic solid tumors and hematological malignancies using intentionally mismatched donor lymphocytes activated with rIL-2: a phase I study.

The feasibility and safety of immunotherapy mediated by intentionally mismatched rIL-2 activated killer lymphocytes (IMAK) with no prior stem cell engraftment was investigated in patients with advanced chemotherapy-resistant hematological malignancies and metastatic solid tumors. Our goals were to maximize anti-cancer activity by using intentionally mismatched donor lymphocytes; amplify killing of target cancer cells by rIL-2 activation of killer cells in vitro and in vivo, and avoid the risk of graft-versus-host disease (GVHD) by anticipated rejection of alloreactive donor lymphocytes. Conditioning consisted of 5 days of fludarabine 25 mg/m(2) or a single dose of cyclophosphamide 1,000 mg/m(2), 2 subcutaneous injections of alpha interferon (IFN) 3 x 10(6) and COX2 inhibitors, followed by administration of IMAK (65 +/- 5 CD3(+)CD56(-); 17 +/- 5 CD3(-)CD56(+)) in conjunction with low dose subcutaneous rIL-2 (6 x 10(6) IU/m(2)/day) for 5 days for continuous activation of alloreactive donor lymphocytes prior to their anticipated rejection.

Immunoregulation of GVHD by triggering the innate immune system with CpG.

Stimulation of Toll-like receptors by oligodeoxynucleotide sequences containing a CpG motif provides signals capable of triggering the innate and adaptive immune systems, thereby leading either to stimulation or suppression of immunoreactivities. Similar immunoregulatory capabilities are necessary for achieving the fine balance between engraftment and graft-versus-host disease required in the setup of allogeneic cell therapy. Ligation of CpG to its Toll-like receptors can be accomplished by treatment of the host or pretransplant treatment of the donor in vivo.

Induction of graft-versus-leukemia (GVL) effect without graft-versus-host disease (GVHD) by pretransplant donor treatment with immunomodulators.

Pretransplant donor treatment with immunomodulators such as complete Freund's adjuvant (CFA) or oligodeoxynucleotide sequences expressing CpG motifs (CpG), was applied in sublethally irradiated host mice inoculated with murine models of mammary carcinoma (4T1) or B cell leukemia (BCL1). Spleen cells or IL-2 activated splenocytes (lymphokine activated killer [LAK]) derived from donor mice treated with CpG emulsified in incomplete Freund's adjuvant (IFA), (CpG + IFA) did not cause graft-versus-host disease (GVHD), but were not efficient enough to induce a significant graft-versus-tumor (GVT) response against 4T1 cells. In contrast, an efficient graft-versus-leukemia (GVL) effect was evident in BCL1-bearing mice inoculated with spleen cells from donors pretreated with CFA or CpG + IFA.

CpG-induced myeloid CD11b+Gr-1+ cells efficiently suppress T cell-mediated immunoreactivity and graft-versus-host disease in a murine model of allogeneic cell therapy.

Transplantation of mismatched allografts in irradiated recipients results in lethal graft- versus-host disease (GVHD). In our study, pretransplantation donor treatment with CpG, administered either alone or emulsified in incomplete Freund's adjuvant, efficiently prevented GVHD in sublethally irradiated recipients of haploidentical (H-2(b) into H-2(b/d)) and fully mismatched (H-2(b) into H-2(d)) allografts. CpG treatment of donor mice caused an accumulation of double-positive CD11bGr-1 cells in their blood and spleens, whereas treatment with CpG+IFA resulted in an even greater accumulation of these cells.