Perioperative Treatment with Rivaroxaban and Dabigatran on Changes of Coagulation and Platelet Activation Biomarkers following Left Atrial Appendage Closure.

Insufficient data exist regarding the investigation of the impact of novel oral anticoagulants (NOACs) on coagulation activation biomarkers in the context of left atrial appendage closure (LAAC) and device-related thrombosis (DRT). The study was designed to investigate the changes and presence of coagulation activation biomarkers between different antithrombotic strategies following LAAC. A total of 120 nonvalvular atrial fibrillation patients intolerant of long-term anticoagulants, who underwent successful WATCHMAN closure implantation, were enrolled (rivaroxaban, n = 82; dabigatran, n = 38). Blood samples were obtained from left atrium (LA) and left atrial appendage (LAA) during the operation and fasting blood samples on the same day of LAAC and 45 days after discharge. The biochemical indicators, thrombin-antithrombin complex (TAT), soluble P-selectin (sP-selectin), von Willebrand factor (vWF), and CD40 ligand (CD40L), were measured by enzyme-linked immunosorbent assay. The primary endpoints of this study were the efficacy and safety characteristics of different antithrombotic strategies, including DRT incidence, stroke or transient ischemic attack, systemic embolism, and clinical major and nonmajor bleeding complications during the follow-up of 180 days. The results revealed that TAT, vWF, sP-selectin, and CD40L levels in vein were significantly reduced by 2.4% (p = 0.043), 5.0% (p < 0.001), 8.7% (p < 0.001), and 2.5% (p = 0.043) from their baseline levels after rivaroxaban treatment. Conversely, no significant changes were detected in the dabigatran group. Furthermore, the plasma levels of platelet activation biomarkers (CD40L and sP-selectin) in both LA and LAA groups were significantly lower after anticoagulation with rivaroxaban, as compared to dabigatran treatment (CD40L: 554.62 ± 155.54 vs. 445.02 ± 130.04 for LA p = 0.0013, 578.51 ± 156.28 vs. 480.13 ± 164.37 for LAA p = 0.0052; sP-selectin: 2849.07 ± 846.69 vs. 2225.54 ± 799.96 for LA p = 0.0105, 2915.52 ± 1402.40 vs. 2203.41 ± 1061.67 for LAA p = 0.0022). Notably, the present study suggests that rivaroxaban may be more effective in the prevention of DRT for patients undergoing LAAC.

Interruption of CD40 Pathway Improves Efficacy of Transplanted Endothelial Progenitor Cells in Monocrotaline Induced Pulmonary Arterial Hypertension.

BACKGROUND/AIMS: Transplantation of endothelial progenitor cells (EPCs) plays a therapeutic role in pulmonary arterial hypertension (PAH). Meanwhile, recruitment of progenitors has potential inflammatory effects and exaggerates vascular injury. CD40 pathway is identified as a major player in vascular inflammatory events. In this study, we investigated the role of CD40 pathway in regulating early outgrowth EPC functions, and searched for improvements in PAH cell therapy. METHODS: EPCs were isolated from rat bone marrow and cultured for 7 days. After treatment with soluble CD40 ligand (sCD40L) for 24 hours, EPC migration, adhesion, proliferation, paracrine and vasculogenesis functions were tested. Rat PAH model was founded by subcutaneous injection of monocrotaline (MCT). Control EPCs or lentivirus vectors (Lv)-shRNA-CD40 EPCs were infused via tail vein at day 7, 14, and 21 after MCT injection. Therapeutic effects were evaluated at day 28. RESULTS: sCD40L dose-dependently impaired EPC migration, adhesion, proliferation, and vasculogenesis functions. However, paracrine effects of soluble intercellular adhesion molecule-1, vascular endothelial growth factor and interleukin-6 were dose-dependently improved by sCD40L. Control EPC-derived conditioned medium protected endothelial cell in vitro vasculogenesis, while sCD40L-pretreated ones showed detrimental effects. After MCT injection, sCD40L levels in rat serum increased gradually. Other than in vitro results, benefits of both two EPC treatments were obvious, even taken at day 21. Benefits of control EPCs wore off over time, but those of Lv-shRNA-CD40 EPCs were more effective and enduring, as characterized by both ameliorated rat hemodynamic and reversed vascular remodeling. Furthermore, Lv-shRNA-CD40 EPCs integrated into endothelium better, rather than into adventitia and media. CONCLUSION: sCD40L impaired protective effects of EPCs. Traditional EPC treatments were limited in PAH, while interruption of CD40 pathway of transplanted cells could apparently improve the therapeutic efficacy.

Immunomodulation and immune reconstitution in chronic lymphocytic leukemia.

Over the past decade, there have been significant advances in our understanding of the pathogenesis of chronic lymphocytic leukemia (CLL), which has been accompanied by an explosion in treatment options. Although the combination of fludarabine, cyclophosphamide, and rituximab is the current frontline treatment of choice for fit patients, targeted therapies such ibrutinib, idelalisib, and ABT-199 are showing great promise in clinical trials. However, none of these drugs seems curative, and allogeneic hematopoietic stem cell transplantation remains the only strategy that produces durable clinical remissions in otherwise poor-risk disease. Immune reconstitution remains an enticing prospect in CLL, as malignant B cells should be particularly susceptible to a T cell-mediated attack. It has recently been demonstrated that the T-cell defect in CLL can be effectively overcome by both lenalidomide treatment and by adoptive transfer of chimeric antigen receptor T cells. A variety of other immunotherapies are in development, including CLL vaccines, CD40 ligand therapies, and monoclonal antibody immune checkpoint blockade. This review explores the nature of the immune defect in CLL and summarizes the recent developments in the immunotherapeutic field.

Novel treatments for immune thrombocytopenia.

Primary immune thrombocytopenia (ITP) is caused by platelet autoantibodies and T-cell dysregulation. Both platelets and their precursor megakaryocytes may be targeted leading to platelet destruction and underproduction. Current treatments for ITP are inadequate since they do not reverse the disease process and generally do not result in durable remissions. In addition, many treatments are limited by side effects including infection and potentially thrombosis. Novel agents that are currently in development target certain key steps in the disease process, including: (1) the interaction between T-cell and antigen presenting cells (CD40-CD154 interaction); (2) the binding of the Fc portion of platelet autoantibodies to Fc-receptors on macrophages (soluble Fc-RIIb); and (3) the signaling pathways leading to platelet phagocytosis by macrophages (Syk inhibition). Other strategies have been to augment platelet production by simulating thrombopoiesis or by neutralizing physiological inhibitors of megakaryopoiesis. Targeted therapies in ITP have the potential to improve disease morbidity and mortality while limiting systemic side effects. Before these agents can be used in practice, additional clinical studies are needed with rational study outcomes including platelet count, bleeding and quality of life. An individualized treatment strategy is needed for patients since ITP is a distinctly heterogeneous disease.

Immunotherapeutic strategies including transplantation: eradication of disease.

Although there have been recent advances with targeted therapies in chronic lymphocytic leukemia (CLL), chemoimmunotherapy remains the treatment of choice; however, this approach is not curative. A key feature of CLL is that it induces a state of immunosuppression, causing increased susceptibility to infections and failure of an antitumor immune response, often worsened by the immunosuppressive effect of treatment. Because of its improved specificity, immunotherapy potentially offers a way out of this dilemma. Allogeneic stem cell transplantation remains the only curative option, but is hampered by the toxicity of GVHD. After many years of promise but little reward, many other immunotherapeutic approaches are now in transition to the clinical setting. Clinical trials including CLL vaccines, CXCR4 antagonists, and adoptive cellular immunotherapies such as chimeric antigen receptor-modified T cells, CD40 ligand gene therapy, and the immunomodulatory drug lenalidomide are ongoing. Results to date suggest that immunotherapeutic approaches for the treatment of CLL might finally be fulfilling their promise.

Partial immune reconstitution of X-linked hyper IgM syndrome with recombinant CD40 ligand.

X-linked hyper IgM syndrome (XHM) is a combined immune deficiency disorder caused by genetic alterations in CD40 ligand. The purpose of this study was to investigate the safety and efficacy of recombinant CD40 ligand (rCD40L) in the treatment of the disease. Three children were administered rCD40L subcutaneously 3 times per week at 0.03 mg/kg for 22 weeks, and after a 12-week drug-free interval, the dose was increased to 0.05 mg/kg for an additional 22 weeks of treatment. Although specific antibody responses to T cell-dependent antigens was lacking, administration of rCD40 resulted in acquisition of the capacity to mount cutaneous delayed type hypersensitivity reactions that disappeared during the drug-free interval as well as the postbiologic follow-up period. With rCD40L treatment, patient T cells developed a new capacity to respond to T-cell mitogens with synthesis of IFN-γ and TNF-α. Intracellular cytokine staining studies showed that both CD4(+) and CD8(+) T cells participated in this response. Finally, CD40L therapy was associated with changes in lymph node size and architecture based on comparison of biopsies taken before and after therapy. This clinical study showed that rCD40L is capable of improving T cell-immune function in patients with XHM.

Recombinant monomeric CD40 ligand for delivering polymer particles to dendritic cells.

Dendritic cells (DCs) are considered the most efficient antigen-presenting cells and are therefore ideal targets for in vivo delivery of antigen for vaccines. We are investigating the strategy of using CD40 ligand (CD40L) as a targeting moiety because this protein has the potential to not only target DCs, but also stimulate cell maturation, leading to more potent immune responses. We have shown that a recombinant, monomeric CD40 ligand fusion protein conjugated to polystyrene micro- and nanoparticles led to significantly enhanced uptake by DCs in vitro. This enhancement was observed for particles of both sizes and in both a murine DC cell line and primary DCs. The uptake appeared to be specifically mediated by CD40L binding to CD40 expressed on DCs. Enhanced uptake of nanoparticles in draining lymph nodes of mice was not observed, however, 48 hours after subcutaneous injection. These findings suggest that CD40 ligand may be a potentially useful targeting moiety for delivery of particulate vaccines to DCs, and that further optimization of both CD40L and the polymer carriers is necessary to achieve efficacy in vivo.

The therapeutic potential of SA-sCD40L in the orthotopic model of superficial bladder cancer.

BACKGROUND: Intravesical administration is an important treatment against superficial bladder cancer and CD40L is essential for the protective anti-tumor immunity. In situ gene therapy with CD40L was demonstrated to successfully inhibit tumor cell growth in the orthotopic mouse model of bladder cancer. In the present study, we prepared streptavidin (SA)-tagged sCD40L and developed a novel immunotherapy for superficial bladder cancer based on the strong interaction between streptavidin and biotin. MATERIAL AND METHODS: The SA-sCD40L fusion protein was expressed in E. coli and purified on the Ni-NTA column. After refolding with dialysis, the bi-function of the fusion protein was determined by flow cytometric analysis for streptaidin-mediated surface modification of MB49 bladder cancer cells and a mouse B cell CD40L-dependent proliferation assay. The mouse orthotopic model of MB49 superficial bladder cancer was used to evaluate the efficacy of SA-sCD40L immunotherapy. RESULTS: The SA-sCD40L fusion protein exhibited both full biotin-binding property and CD40L bioactivity. After intravesical instillation, the SA-sCD40L bi-functional fusion protein was durably immobilized on the biotinylated mucosal surface of bladder wall for up to four days. The SA-sCD40L treatment significantly prolonged the survival of MB49 tumor-bearing mice and cured 50% of mice with MB49 superficial bladder cancer without significant adverse effects. In addition, more tumor-infiltrating CD4(+)or CD8(+) T cells were observed in SA-sCD40L-treated group. CONCLUSION: Intravesical immobilization of SA-sCD40L elicited a strong and long-lasting immunity against the MB49 bladder cancer.

A phase I study of immune gene therapy for patients with CLL using a membrane-stable, humanized CD154.

Ligation of CD40 on chronic lymphocytic leukemia (CLL) cells induces phenotypic and biochemical changes that facilitate CLL cell-T cell interactions and enhances the sensitivity of CLL cells to clearance by adaptive and innate immune-effector mechanisms. CLL cells can be transduced to express CD40 ligand (CD154) using a replication-defective adenovirus vector, thereby cross-linking CD40 on transduced and non-transduced, bystander CLL cells. In a previous study, patients received infusions of autologous CLL cells, transduced to express murine CD154 (mCD154), which induced anti-leukemic immune responses, but also anti-mCD154 antibodies. In this study, we report a phase I study, in which patients were infused with 1 × 10(8), 3 × 10(8) or 1 × 10(9) autologous CLL cells transduced ex vivo to express ISF35, a humanized, membrane-stable CD154. Infusions were well tolerated and consistently followed by reductions in blood lymphocyte counts and lymphadenopathy. After infusion, circulating CLL cells had enhanced or de novo expression of CD95, DR5, p73 and Bid, which enhanced their susceptibility to death-receptor-mediated or drug-induced apoptosis, including CLL cells with deletions at 17p13.1 (del(17p)). Two patients who had CLL with del(17p) had subsequent chemoimmunotherapy and responded well to treatment. In summary, infusions of autologous, ISF35-transduced CLL cells were well tolerated, had biological and clinical activity, and might enhance the susceptibility of CLL cells with del(17p) to chemoimmunotherapy.

Effects of gene transfer CTLA4Ig and anti-CD40L monoclonal antibody on islet xenograft rejection in mice.

Blockade of a costimulatory pathway by adenovirus-mediated cytotoxic T lymphocyte associated antigen 4 immunoglobulin (CTLA4-Ig) gene transfer and anti-CD40L mAb(MR1) have been reported to enhance graft survival in several experimental transplantation models. In this study, we investigated the effects of gene transfer of CTLA4Ig and MR1 on islet xenograft rejection in mice. Recombinant adenovirus AdCTLA4Ig was constructed to express CTLA4Ig. Islet grafts from adult male DA rats transferred with AdCTLA4Ig were transplanted to streptozocin-induced diabetic Balb/c mice. The diabetic mice were treated with MR1 after transplantation. We evaluated the islet xenograft mean survival time as well as changes in interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) levels in transplanted mice. The mean survival of islet xenografts in the MR1 treatment group was 34.9 +/- 5.62 days, in the AdCTLA4Ig treatment group it was 56.5 +/- 10.64 days, and in the AdCTLA4Ig plus MR1 treatment group it was 112.9 +/- 19.26 days, all significantly prolonged compared with an untreated group (8.1 +/- 0.83 days). Within 1 week after transplantation the levels of IL-2 and TNF-alpha showed sharp increases in the untreated group, being significantly higher than those observed prior to transplantation. In conclusion, using both AdCTLA4Ig and MR1 can improve the islet xenograft survival. The beneficial effects of the combined use of the 2 reagents were superior to either 1 alone, possibly related to down-regulated expression of Th1 cell-related cytokines.

Soluble CD40 ligand impairs the function of peripheral blood angiogenic outgrowth cells and increases neointimal formation after arterial injury.

BACKGROUND: Recent work has revealed an essential involvement of soluble CD40 ligand (sCD40L) in inflammation and atherosclerosis. We investigated whether sCD40L functionally affects peripheral blood-derived angiogenic early outgrowth cells (EOCs) and neointimal remodeling after arterial injury. METHODS AND RESULTS: Besides myeloid and endothelial markers, cultured human EOCs strongly expressed CD40 mRNA and protein. EOC adhesion to fibronectin, fibrinogen, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 under flow conditions, as well as their transmigration toward stromal cell-derived factor-1alpha, was dose-dependently reduced after preincubation with recombinant human sCD40L for 24 hours. Integrin expression was unaffected by sCD40L, implying that integrin adhesiveness was attenuated. Surface-immobilized CD40L supported much lower adhesion of EOCs than fibronectin. Treatment of EOCs with sCD40L increased superoxide anion production and decreased viability and proliferation. Notably, CD40(-/-) mice displayed reduced neointima and improved re-endothelialization after carotid wire injury compared with wild-type mice, and therapeutic infusion of control EOCs but not EOCs pretreated with sCD40L attenuated neointimal growth after wire injury in nude mice. Furthermore, neointimal growth was more markedly diminished by infusion of spleen-derived CD40(-/-) mouse EOCs than by that of wild-type EOCs. Preincubation of wild-type EOCs but not CD40(-/-) EOCs with sCD40L before their infusion markedly aggravated neointimal formation. Treatment with sCD40L attenuated luminal incorporation of EOCs and accelerated neointimal progression. CONCLUSIONS: Endothelial dysfunction due to persistently elevated plasma levels of sCD40L may be attributable to an impairment of EOC function. Hence, in the context of arterial injury, therapeutic blockade of sCD40L may provide a novel strategy for accelerating endothelial regeneration and attenuating neointimal remodeling.

Cationic liposome-mediated transfection of CD40 ligand gene inhibits hepatic tumor growth of hepatocellular carcinoma in mice.

OBJECTIVE: To evaluate the efficacy of cationic liposome-mediated CD40 ligand (CD40L) gene therapy for hepatocellular carcinoma. METHODS: 1x10(6) of parental H22 cells or H22 cells transfected with the expression vector containing murine CD40L cDNA encoding the entire coding region (pcDNA3.1(+)-mCD40L) were inoculated subcutaneously into the left flanks of syngenic BALB/C mice. The tumor-bearing mice (tumor nodules 10 mm in maximal diameter) received the treatment of the intratumoral injection of pcDNA3.1(+)-mCD40L/Transfectam, pcDNA3.1(+), or phosphate-buffered saline (PBS), or no treatment. The mice were monitored for tumor growth weekly. We examined mCD40L messenger ribonucleic acid (mRNA) expression by reverse transcription polymerase chain reaction (RT-PCR) and the histologic changes in tumors at two weeks after intratumoral injection using immunohistochemical staining of tumor tissues. RESULTS: All mice inoculated with parental H22 cells developed a tumor subcutaneously, and the tumor size increased progressively within three weeks. However, the mice receiving H22-CD40L cells exhibited complete regression of the tumor two weeks after tumor cell inoculation. The tumor-bearing animals with the treatment of pcDNA3.1(+) or PBS, or without treatment had progressive tumor growth, while those mice treated with pcDNA3.1(+)-mCD40L exhibited a significant inhibition of tumor growth. RT-PCR analysis showed that 783-bp fragments corresponding to the mCD40L mRNA were amplified only from pcDNA3.1(+)-mCD40L treated tumors. The tumor samples from pcDNA3.1(+)-mCD40L-treated mice showed significant lymphocyte infiltration, apoptotic bodies, and confluent necrosis in the tumor tissues. CONCLUSION: The tumorigenicity of CD40L-expressing cells was abrogated when the cells were implanted subcutaneously. In vivo gene therapy of established liver tumor nodules in mice by the intratumoral injection of pcDNA3.1(+)-mCD40L led to significant tumor inhibition. There was mCD40L mRNA expression in the tissues from pcDNA3.1(+)-mCD40L-treated tumors. The intratumoral injection of pcDNA3.1(+)-mCD40L induced a strong inflammatory, mainly lymphocytic infiltration of the tumor, and increased the necrotic rate of the neoplastic cells.

Expression of CD40 in ovarian cancer and adenovirus-mediated CD40 ligand therapy on ovarian cancer in vitro.

AIMS AND BACKGROUND: To test the expression level of CD40 on ovarian cancer tissues and its correlation to clinicopathological features of patients and to evaluate the therapeutic effectiveness of adenovirus-mediated CD40 ligand on ovarian cancer in vitro. MATERIAL AND METHODS: The expression of CD40 on paraffin-embedded ovarian cancer tissues (n=58) and normal ovarian tissues (n=15) was tested by immunohistochemistry, and CD40 expression on ovarian cancer cells derived from fresh surgical specimens was tested by flow cytometry analysis. The apoptosis-inducing effects of adenovirus-mediated CD40 ligand therapy on ovarian cancer cells derived from fresh surgical specimens were analyzed by flow cytometry analysis and TUNEL assay. RESULTS: CD40 expression was detected in 60.3% (35/58) of paraffin-embedded ovarian cancer tissues and 73.3% (11/15) of fresh ovarian cancer tissues, but not in normal ovarian tissues (n=15). CD40 expression was significantly correlated with FIGO stage of ovarian cancer. Adenovirus-mediated CD40 ligand therapy induced significant apoptosis effects on ovarian cancer cells derived from fresh surgical specimens in vitro compared to null adenovirus vector and phosphate-buffered saline. CONCLUSIONS: Our results suggested the therapeutic potential of adenovirus-mediated CD40 ligand on ovarian cancer, especially on the late stage of ovarian cancer.

Efficient adenovector CD40 ligand immunotherapy of canine malignant melanoma.

Cutaneous canine melanomas are usually benign in contrast to human malignant melanoma. However, the canine oropharyngeal, uveal, and mucocutaneous neoplasms are aggressive and have metastatic potential. Surgery and to a lesser extent radiotherapy and chemotherapy are widely adopted treatments but are seldom curative in advanced stages. The similarities between human and canine melanoma make spontaneous canine melanoma an excellent disease model for exploring novel therapies. Herein, we report the first 2 adenovector CD40L immunogene (AdCD40L) treatments of aggressive canine malignant melanoma. Case no. 1 was an advanced stage III oral melanoma that was cured from malignant melanoma with 2 intratumor AdCD40L injections before cytoreductive surgery. After treatment, the tumor tissue was infiltrated with T lymphocytes and B lymphocytes suggesting immune activation. This dog survived 401 days after the first round of gene therapy and was free of melanoma at autopsy. Case no. 2 had a conjunctival malignant melanoma with a rapid progression. This case was treated with 6 AdCD40L injections over 60 days. One hundred and twenty days after start of gene therapy and 60 days after the last injection, the tumor had regressed dramatically, and the dog had a minimal tumor mass and no signs of progression or metastasis. Our results indicate that AdCD40L immunogene therapy is beneficial in canine malignant melanoma and could be considered for human malignant melanoma as well.

Allogenic mixed chimerism induced by nonlymphoablative regimen including donor BMT with low-dose TBI and anti-CD40L cured proliferative glomerulonephritis in lupus mice.

Allogeneic mixed chimerism achieved by low-dose total body irradiation (TBI) and anti-CD40L monoclonal antibody (mAb) with donor bone marrow transplantation (BMT) and host T cell depletion overcomes both allo- and autoimmunity. We investigated whether a similar regimen without T cell depletion cured diffuse proliferative glomerulonephritis. Male BXSB mice (H-2b) were injected with 20 x 10(6) BALB/c (H-2d) BM cells. When indicated, 3 Gy TBI on day -1 and anti-CD40LmAb (2 mg) on day 0 of BMT was given. Skin grafting was performed 1 day after BMT. BXSB mice were divided into four groups--I: BMT with TBI and anti-CD40LmAb; II: TBI; III: TBI and anti-CD40LmAb; and IV: no treatment. Chimerism in peripheral blood was analyzed. The kidney was examined histologically. TBI with anti-CD40LmAb and BMT allowed induction of multilineage mixed chimerism and donor-specific tolerance to skin grafts without graft-versus-host disease (GVHD). There was significant decrease in glomerular PAS-positive material deposition score, glomerular cell numbers, IgG, and C3 deposition in chimeric mice. All chimeric mice survived. Allogeneic mixed chimerism induced by a less toxic, nonlymphoablative regimen achieved allograft tolerance and cured glomerulonephritis in BXSB lupus mice.

Novel agents and strategies for treatment of p53-defective chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is a common leukemia with a highly variable natural history. A subset of patients with high-risk CLL rapidly progress to develop symptomatic disease requiring treatment. Over-represented in this group are those who have a deletion of 17p13.1, the chromosomal location of the tumor suppressor gene P53. Of all prognostic factors examined in CLL, del(17p13.1) has a superior predictive value for poor response to conventional therapy. In this article we review the current published data on prognostic factors relevant to treatment in CLL. We next provide therapeutic recommendations for patients with del(17p13.1) that are available to oncologists in general practice. Chemoimmunotherapy, alemtuzumab, or high-dose corticosteroids are all effective as initial therapy for these patients, but progression is generally rapid. If allogeneic immune therapy is to be considered, it should be approached as part of initial or first salvage therapy. The investigational agent flavopiridol has also demonstrated clinical activity in this subset of patients. Identification of small molecules and new treatment approaches for patients with del(17p13.1) is a major focus of several investigators. Selection of therapy based on high-risk genomic features represents an appropriate treatment approach supported by currently available published data.

Gene therapy and active immune therapy of hematologic malignancies.

Gene therapy for patients with hematologic malignancies, particularly chronic lymphocytic leukemia (CLL), have focused on transducing primary leukemia cells with a virus vector to express immune-stimulating genes which can induce and propagate a productive and clinically significant immune response against the malignant cells. A variety of replication-defective vectors has been studied to transduce genes for cytokines and function-associated surface molecules. Active vaccines have been developed in vitro, and their activity has been confirmed in clinical trials. Ongoing work aims to optimize this strategy and to identify the appropriate and optimal patient groups in which to apply vaccine therapy. Clinical trials also have provided insight into unexpected alternative mechanisms through which these strategies might provide a clinical benefit.

CD40 and its ligand in atherosclerosis.

CD40-CD40 ligand (CD40L) interactions play a central role in the development and progression of atherosclerosis. In the late 1990s, we and others have shown that complete inhibition of the CD40L signaling pathway resulted in a decrease in atherosclerosis and in the induction of a stable atherosclerotic plaque phenotype. These stable plaques contained high amounts of collagen and vascular smooth muscle cells, whereas the amount of macrophages and T lymphocytes was low. Because clinical complications of atherosclerosis are mostly the result of plaque rupture, induction of plaque stability would significantly reduce the morbidity and mortality of atherosclerosis and thus validates inhibition of the CD40L system as a therapeutic target for atherosclerosis. However, long-term inhibition of this system probably compromises the immune system of the patient. Therefore, it is desirable to target either the downstream signaling modulators of the CD40-CD40L system that are associated with atherosclerosis, or target the CD40-CD40L system in a local, cell type-specific way. This is likely to induce plaque stabilization with limited systemic side effects, and a significant reduction of cardiovascular disease.

CD40L - a multipotent molecule for tumor therapy.

CD40L-based therapy is currently under intensive investigation for its potent anti-tumor effects in experimental animal models of cancer as well as in Phase I clinical trials. CD40L is one of the strongest inducers of Th1 responses although it stimulates both innate and adaptive immunity. The molecule is normally expressed by activated immune cells such as T helper cells that act on dendritic cells to induce their maturation and capability of activating tumor-reactive T cells. Moreover, recent findings implicate that CD40L stimulation abrogates the suppressive effect of T regulatory cells. Interestingly, while being an activator of immune cells, CD40L has been shown to directly induce apoptosis in tumor cells by mechanisms only beginning to emerge. These two major effector mechanisms synergize to combat tumor growth. Optimal use of this multipotent molecule might therefore result in effective immunotherapy of cancer. CD40L can be administered to patients as soluble protein trimers. To achieve membrane-bound expression, viral vectors can be used to transfer CD40L cDNA into 1) tumor cells ex vivo for creating CD40L-expressing tumor vaccines, 2) ex vivo cultured dendritic cells for cell therapy, and 3) tumor nodules in situ. CD40L substitutes such as CD40-directed agonistic antibodies have been evaluated with interesting results in experimental models. In this survey, different types and mechanisms of CD40L-based therapy will be discussed from bench to bedside.

A phase-I trial using a universal GM-CSF-producing and CD40L-expressing bystander cell line (GM.CD40L) in the formulation of autologous tumor cell-based vaccines for cancer patients with stage IV disease.

BACKGROUND: Significant antitumor T-cell responses are generated in vitro when human lymphocytes are stimulated with autologous tumor cells in the presence of bystander cells transfected with CD40L and GM-CSF. Our goal was to test this bystander-based vaccine strategy in vivo in cancer patients with stage IV disease. METHODS: Patients received three intradermal vaccine injections (irradiated autologous tumor cells plus GM.CD40L bystander cells) at 28-day intervals. Patients with no disease progression received three additional vaccines at 4, 12, and 24 months. Patients were monitored for toxicity, tumor response, and tumor-specific immune responses. RESULTS: Twenty-one patients received at least three vaccine injections, with no toxicity attributable to the vaccine. Immunohistochemistry of vaccine injection site biopsies with CD1a and CD86 antibodies confirmed recruitment and activation of dendritic cells. There was no tumor regression after vaccination, but many patients had stable disease, including six of ten melanoma patients. Four patients developed tumor-specific T-cell responses on ELISPOT testing. One patient, who had stable disease for 24 months, demonstrated an increase in MART-1-specific T-cells by tetramer analysis after re-immunization; biopsy of the tumor that progressed 2 years after the onset of vaccination revealed a massive peritumoral and intratumoral T-cell infiltrate. CONCLUSIONS: Vaccination of cancer patients with autologous tumor cells and GM.CD40L bystander cells (engineered to express GM-CSF and CD40L) is safe, can recruit and activate dendritic cells, and can elicit tumor-specific T-cell responses. Phase-II trials are underway to evaluate the impact of bystander-based vaccines on melanoma and mantle cell lymphoma.