ALBERT

Description: The induction of transplantation tolerance involves a T-cell–mediated process of immune regulation. In clinical transplantation, the use of immunosuppressive drugs that promote or facilitate this process would be highly desirable. Here, we investigated the tolerance-promoting potential of the immunosuppressive drug FK778, currently under development for clinical therapy. Using a human allogeneic in vitro model we showed that, upon T-cell receptor (TCR) triggering, FK778 induced a regulatory phenotype in CD4+CD25− T cells. Purified CD4+CD25− T cells primed in the presence of FK778 showed hyporesponsiveness upon restimulation with alloantigen in the absence of the drug. This anergic state was reversible by exogenous interleukin-2 (IL-2) and was induced independent of naturally occurring CD4+CD25+ regulatory T cells. Pyrimidine restriction was a crucial requirement for the de novo induction of regulatory activity by FK778. The FK778-induced anergic cells showed suppressor activity in a cell-cell contact–dependent manner; were CD25high, CD45RO+, CD27−, and CD62L−; and expressed cytotoxic T-lymphocyte–associated antigen-4 (CTLA-4), glucocorticoid-induced tumor necrosis factor receptor (GITR), and FoxP3. The cells revealed delayed p27kip1 degradation and enhanced phosphorylation of STAT3. In conclusion, the new drug FK778 shows tolerizing potential through the induction of a regulatory T-cell subset in CD4+CD25− T cells.

Description: The generation of immunoregulatory T cells that block the B7(CD86/CD80)-CD28 and/or CD40-CD154 costimulatory pathways has great potential for the induction of long-term transplantation tolerance. In a human polyclonal in vitro model, combined monoclonal antibody (mAb) blocking of the costimulatory ligands CD40 and CD86 lead to allospecific T-cell anergy that cannot be reversed by antigenic rechallenge in the presence of IL-2. Although antigenic restimulation with IL-2 restored the proliferative response, subsequent antigenic restimulation of the restored anergic cells in a tertiary mixed lymphocyte culture still resulted in nonresponsiveness. Importantly, these anergic T cells suppress the response of naive alloreactive T cells in an antigen-specific way via linked recognition. Suppression may partially depend on local IL-10 production, while transforming growth factor–β (TGF-β) did not play a role. Irrespective of the monoclonal antibody combination used, blast formation occurred in a subset of CD4+ cells. These cells were characterized by a sustained CD45RA expression, an increased T-cell receptor density, and a lower level of CD4 expression. A reduced number of CD45RO+/CD8+ T cells was observed whenever anti-CD86 was combined with anti-CD40, which was reflected by an even more attenuated cytotoxic T-cell function. This indicates the importance of CD40-CD154 in the generation of cytotoxic T cells in this transplantation model. We hypothesize that in our model, anergy is induced in the CD4+ T-cell subset, whereby CD8+ cytotoxic effector function is impaired by the lack of both CD40-CD154 signaling and cytokine-mediated help. This costimulatory ligand–directed mAb approach might well be used for the ex vivo generation of antigen-specific immunoregulatory T cells applicable in adoptive immunotherapy.

Description: The reported incidence of deep vein thrombosis (DVT) using routine venography in patients with isolated leg fractures distal to the knee is as high as 40%. However venography is a very sensitive screening test primarily detecting asymptomatic, distal thrombi whose clinical relevance is uncertain. Therefore venography may not be the best outcome measure to assess the clinical burden of symptomatic VTE, or as an endpoint for trials of thromboprophylaxis. We report preliminary results from the first, multicenter, prospective study designed to define the incidence of symptomatic VTE in patients with such fractures. From August 2002 to April 2004, 1808 consecutive patients with fractures of the patella, fibula and foot (treated conservatively or operatively) and tibial fractures (treated non operatively) were screened for entry at 5 hospitals in Ontario, Canada. Patients were enrolled after informed consent was obtained, in person or by telephone, within 96 hours of the injury. Patients with major trauma, active cancer and previous VTE were excluded. Thromboprophylaxis was not allowed. Patients were followed prospectively for 3 months, with telephone calls at 14 days, 6 weeks and 3 months. Education regarding symptoms of DVT and pulmonary embolism (PE) was provided at study entry and patients were asked about specific symptoms at follow up. Suspected DVT and PE were investigated in a standardized manner. At the time of this writing, 826 enrolled patients have completed 3 months of follow up. The mean age was 45 years (range 16 to 93) and 59.5% of this cohort was female. Most injuries were caused by falls (75%), followed by sports injuries (16%), vehicular accidents (5%) and occupational injuries (4%). 15% of patients had other minor injuries. 99% of these fractures were unilateral and 97% were closed. Fractures of the fibula were the commonest (38%), followed by metatarsal (29%), phalanges (13%), calcaneus, talus or tarsal (10%), tibia (10%) and patella (7%). Only 11% of fractures were surgically treated. 88% of patients received a cast or splint for a mean duration of 41 ± 20 days. Four patients received anticoagulant prophylaxis (outside study protocol) for subsequent major surgery for another reason within the study period. Complete follow up was available for 97.5% of this cohort. 2.5 % of patients either withdrew consent for the follow up or could not be contacted despite numerous attempts at follow up. By 3 months, only 7 patients had sustained a symptomatic VTE (2 proximal DVT, 3 calf DVT, 2 PE) with no fatal PE - an incidence of 0.9% (95% C.I. 0.3 to 1.8%). So far, our results provide reassurance that symptomatic and fatal VTE are infrequent complications after these fractures without thromboprophylaxis, and highlight the discrepancy between clinical endpoint studies and studies using venography. They also suggest that routine thromboprophylaxis may not be warranted in these patients. Despite the large sample size, the low event rate does not allow us to define a subgroup of patients who may be at higher risk for VTE.

Description: The advent of imatinib has considerably changed treatment in chronic myeloid leukemia (CML). Although response rate and duration of response with imatinib monotherapy continue to be impressive, the majority of patients (pts) in complete cytogenetic remission (CCR) retain BCR-ABL transcripts as markers of residual disease and potential cause of relapse. In addition rapid evolvement of blast crises from CCR has been reported. Therefore, we designed an investigator-initiated phase IV prospective trial aiming to address the role of imatinib in combination with interferon alpha (IFN) or Ara-C and treatment intensification with high dose imatinib. In July 2002, the German CML-Study Group has activated the four-armed randomized controlled trial comparing imatinib 400 mg/d with imatinib+IFN, imatinib+Ara-C and imatinib after IFN failure in newly diagnosed pts with chronic phase CML. Randomization is stratified according to prognostic risk groups and not biased by consecutive allogeneic stem cell transplantation (SCT). High risk pts are randomly assigned to primary imatinib-based therapies including a 4th treatment arm with imatinib 800 mg/d. The treatment arm imatinib after IFN failure retains the chance of an IFN-induced CCR with 10 year-survival rates of 70–80%. In case of IFN failure pts are crossed over to imatinib. Allogeneic SCT is recommended for all pts with high risk, imatinib failure and EBMT-score 0–1. By August 2004, 429 pts were randomized: imatinib 400 mg/d (n=103), imatinib+IFN (n=130), imatinib+Ara-C (n=108), imatinib after IFN failure (n=84), and imatinib 800 mg/d (n=4). According to the New CML score, 34% of patients were low risk, 56% intermediate risk, and 10% high risk. At baseline, median WBC count was 63/nl (3.5–513), median platelet count was 385/nl (49–2,799) and median hemoglobin was 12.7 g/dl (6.1–16.6). We sought to evaluate results of the first cohort of pts (n=217) with a 〉12 months follow-up, recruited between 7/2002 and 5/2003 (imatinib 400 mg/d, n=52; imatinib+IFN, n=70; imatinib+Ara-C, n=49; imatinib after IFN failure, n=46). Median age was 56 yrs (16–82), 62% of pts were male. Cytogenetic data are available from 117 pts (68%) randomized to primary imatinib-based therapies. At 12 months, 104 pts (89%) achieved a major cytogenetic remission (Ph+

Description: Genetic modification of dendritic-cell (DC) function is an attractive approach to treat disease, either using mature DCs (mDCs) to immunize patients, or immature DCs (iDCs) to induce tolerance. Viral vectors are efficient at transducing DCs, and we have investigated the effect of transduction with a variety of viral vectors on the phenotype and function of DCs. Adenovirus (Ad), human immunodeficiency virus (HIV), equine anemia virus (EIAV), and Moloney murine leukemia virus (MMLV) all up-regulate costimulatory molecules and major histocompatibility complex (MHC) class II expression on DCs, as well as, in the case of Ad and lentiviral vectors, inducing production of Th1 and proinflammatory cytokines. Following transduction there is activation of double-stranded (ds) RNA-triggered pathways resulting in interferon (IFN) α/β production. In addition, the function of virally infected DCs is altered; iDCs have an increased, and mDCs a decreased, ability to stimulate a mixed lymphocyte reaction (MLR). Viral transduction of mDCs results in up-regulation of the indoleamine 2,3-dioxygenase (IDO) enzyme, which down-regulates T-cell responsiveness. Inhibition of IDO restores the ability of mDCs to stimulate an MLR, indicating that IDO is responsible for the modulation of mDC function. These data have important implications for the use of viral vectors in the transduction of DCs.

Description: Clinical responses of solid tumors after allogeneic human leukocyte antigen-matched stem cell transplantation (SCT) often coincide with severe graft-versus-host disease (GVHD). Targeting minor histocompatibility antigens (mHags) with hematopoiesis- and cancer-restricted expression, for example, HA-1, may allow boosting the antitumor effect of allogeneic SCT without risking severe GVHD. The mHag HA-1 is aberrantly expressed in cancers of most entities. However, an estimated 30% to 40% of solid tumors do not express HA-1 (ie, are HA-1neg) and cannot be targeted by HA-1–specific immunotherapy. Here, we investigated the transcriptional regulation of HA-1 gene expression in cancer. We found that DNA hypermethylation in the HA-1 promoter region is closely associated with the absence of HA-1 gene expression in solid tumor cell lines. Moreover, we detected HA-1 promoter hypermethylation in primary cancers. The hypomethylating agent 5-aza-2′-deoxycytidine induced HA-1 expression only in HA-1neg tumor cells and sensitized them for recognition by HA-1–specific cytotoxic T lymphocytes. Contrarily, the histone deacetylation inhibitor trichostatin A induced HA-1 expression both in some HA-1neg tumor cell lines and in normal nonhematopoietic cells. Our data suggest that promoter hypermethylation contributes to the HA-1 gene regulation in tumors. Hypomethylating drugs might extend the safe applicability of HA-1 as an immunotherapeutic target on solid tumors after allogeneic SCT.

Description: The humanized anti-CD74 monoclonal antibody (mAb) hLL1 is under evaluation as a therapeutic agent. The effects of hLL1—at times in comparison with the CD20 mAb rituximab—were assessed on non-Hodgkin lymphoma (NHL) and multiple myeloma (MM) cell lines and in tumor-bearing SCID mice. In vitro, hLL1 caused growth inhibition and induction of apoptosis in B-cell lines when cross-linked with an antihuman immunoglobulin G (IgG) second antibody. The sensitivity profile of the cell lines was different for hLL1 and rituximab, and antiproliferative activity was augmented when the 2 mAbs were combined. Unlike rituximab, hLL1 did not induce antibody-dependent cellular cytotoxicity or complement-mediated cytotoxicity. In xenograft models of NHL and MM, treatment with hLL1 yielded significant survival benefits without cross-linking agents. Efficacy was greater in the MM model, in which median survival time was increased more than 4.5-fold. Thus, hLL1 has therapeutic potential as a naked mAb for B-cell malignancies because of high antigen expression on malignant cells, specifically MM, with limited expression on normal tissue, and because of its antiproliferative activity. Further, hLL1 may be a therapeutic candidate for rituximab-resistant disease because the 2 antibodies apparently act through distinct mechanisms and exhibit different expression and sensitivity profiles, and activity can be augmented when the mAbs are combined.

Description: Acute graft-versus-host disease (aGvHD) remains a major complication in recipients of hematopoietic cell allografts and is associated with poor outcome. Salvage treatment is difficult after failure of steroids. OKT3 muromonab is a monoclonal murine IgG2a antibody directed against the CD3 antigen on T-lymphocytes that has proven effective in transplant settings both of solid organs and bone marrow. Here we report on the results of OKT3 treatment in 43 patients who had received stem-cell or bone marrow allografts for hematologic malignancies and subsequently been diagnosed with steroid-resistant aGvHD. Overall, 48 treatment cycles of OKT3 (5 mg intravenous injection once daily) were administered for acute GvHD of grades II (n = 12), III (n = 27) and IV (n = 9). Mean duration of OKT3 therapy was 9 (range, 1 –16) days. Twenty cycles of OKT3 were administered as second line and 28 as third-plus line (third line, n = 14; fourth line, n = 14) treatment regimens. Side effects were mild to moderate, comprising fever, dyspnea, tachycardia, and vomiting. Thirty of 42 evaluable patients responded to therapy for an overall response rate of 69 %. Complete remissions were seen in 6 (11.9 %) and partial remissions in 24 patients (57.1 %). Response to treatment was 88.8 % for skin GvHD; 53.3 % for gut aGvHD; and 8.7 % for liver involvement. Recurrent or progressive acute GvHD was observed in 23 patients (54.8 %) after a median of 9 (range, 1 – 58) days. Pharmacokinetic studies of monoclonal antibody OKT3 were performed in 17 patients, 16 of whom achieved at least a partial remission. Treatment duration was 〉 5 days in 16 patients. Adequate plasma levels (〉 1000 ng/ml) were observed in 13 patients after a median of 6 (1 – 11) days on treatment. OKT3 concentration became undetectable at a median of merely 4 (3 – 11) days after discontinuation of therapy. Survival at 100 days from transplantation was 58.1 % and at one year, 25.5 % with the most important causes of death being infectious complications (44.7%) and GvHD (33.2%). Patients treated with OKT3 earlier in the course of aGVHD showed a trend to better survival: 35% of patients with 2nd-line therapy were alive at one year from transplantation, compared to 17.4% with 3rd- plus line treatment (p=0.21). There was also a trend to a better one-year survival for patients with grade II (33% of patients alive) when compared to grade III/IV aGvHD (16% of patients alive; p=0.24). Thus, a significant proportion of patients with corticosteroid-resistant acute GvHD showed a response to salvage treatment with OKT3. More effective antimicrobial prophylaxis and treatment are mandatory to overcome considerable treatment-related mortality in those high-risk patients.

Description: The Wilms’ tumor antigen (WT1) is overexpressed in almost all leukemias and in several solid tumors. Overexpression of WT1 blocks the normal differentiation and enhances proliferation of hematopoietic progenitor cells. WT1 is also used in the detection of minimal residual disease. Using WT1-specific MHC class I tetramers, we were able to detect ex vivo low numbers of WT1-specific CD8+ T cells in the peripheral blood or bone marrow of leukemia patients, but not of healthy donors. In one particular donor we could detect up to 24% WT1 tetramer positive cells at the time of diagnosis. WT1 tetramer positive cells were present in all types of leukemia, except for CLL, and also in patients with MDS. Because WT1 plays an important role in leukemogenesis, it could serve as an antigenic target for dendritic cell-based immunotherapy. We used the mRNA electroporation strategy that allows presentation of multiple WT1 epitopes by MHC class I molecules, irrespective of the HLA haplotype. Monocyte-derived DC (Mo-DC) were electroporated with in vitro transcribed WT1 mRNA. RT-PCR and Western blot analysis showed that WT1 RNA and protein, respectively, was present for up to 5 days in WT1-electroporated DC, but not in mock- or EGFP mRNA-electroporated Mo-DC. Importantly, using a CD8+ T cell clone that secretes IFN-gamma upon recognizing the HLA-A2 immunodominant WT1126–134 epitope, we showed that WT1 mRNA-electroporated Mo-DC processed the WT1 protein via the MHC class I pathway and presented the WT1 epitope to the T cells in an HLA- and antigen-specific manner. Since Mo-DCs are a non-expandable source of antigen-presenting cells, we also used proliferating CD40-activated B (CD40-B) cells as inducers for WT1-specific T cell immunity. CD40-B cells were expanded to high numbers from a limited amount of peripheral blood and subsequently electroporated with WT1 mRNA. In T cell clone activation experiments, WT1 mRNA-electroporated CD40-B cells were as efficient as Mo-DC in presenting the WT1 epitope in a MHC class I-restricted manner. Based on these results, we are currently focusing on the in vitro (re)activation of autologous WT1-specific cytotoxic T cells of leukemia patients using WT1-loaded autologous Mo-DC or CD40-B cells and on the immunological parameters to break immune tolerance against the WT1 tumor self antigen.

Description: Key Points The majority of suppressive Tregs in human secondary lymphoid organs are activated, produce cytokines, and proliferate. Human lymphoid organs may provide a platform for in vivo expansion of infused Tregs and subsequent tissue-directed homing.