Analysis of adenoviral attachment to human platelets.

BACKGROUND: Systemic adenoviral (Ad) vector administration is associated with thrombocytopenia. Recently, Ad interaction with mouse platelets emerged as a key player determining liver uptake and platelet clearance. However, whether Ad can activate platelets is controversial. Thus, in vitro analysis of Ad attachment to platelets is of interest. METHODS: We developed a direct flow cytometry assay to specifically detect Ad particles adherent to human platelets. The method was pre-validated in nucleated cells. Blocking assays were employed to specifically inhibit Ad attachment to platelets. Platelet activation was analyzed using annexin v flow cytometry. RESULTS: We found in vitro that Ad binding to human platelets is synergistically enhanced by the combination of platelet activation by thrombin and MnCl2 supplementation. Of note, Ad binding could activate human platelets. Platelets bound Ad displaying an RGD ligand in the fiber knob more efficiently than unmodified Ad. In contrast to a previous report, CAR expression was not detected on human platelets. Integrins appear to mediate Ad binding to platelets, at least partially. Finally, alphaIIbbeta3-deficient platelets from a patient with Glanzmann thrombasthenia could bind Ad 5-fold more efficiently than normal platelets. CONCLUSION: The flow cytometry methodology developed herein allows the quantitative measurement of Ad attachment to platelets and may provide a useful in vitro approach to investigate Ad interaction with platelets.

Prevention of acute graft-vs-host disease by a single low-dose cyclophosphamide injection following allogeneic bone marrow transplantation.

OBJECTIVE: Previously, we documented that conditioning based on donor-specific cell transfusion (DST) and subsequent selective depletion of activated donor-reactive cells by cyclophosphamide (CY) facilitates alloengraftment in a murine transplantation model. Transplantation event represents a strong immunogenic stimulus for host-reactive donor T cells that induce graft-vs-host disease (GVHD). Therefore, in this study, we addressed the question of whether a single posttransplantation CY administration (CY2) can prevent acute GVHD-related mortality without compromising engraftment of allogeneic transplant. MATERIALS AND METHODS: Splenocyte-enriched C57BL/6 bone marrow was transplanted to BALB/c recipients after mild irradiation, and conditioning with DST and 100 mg/kg CY. Following transplantation, recipients were left untreated or given on a specified day a single CY2 injection (50 mg/kg). All animals were monitored for survival, chimerism, and clinical signs of GVHD. Experimental mice that received BCL1 leukemia cells before transplantation were monitored for leukemia-related mortality as well. RESULTS: Animals that received no CY2 after transplantation died of acute GVHD. A single low-dose CY2 treatment within the first 5 days after transplantation prevented mortality in most recipients. However, only CY2 administration on days +1 or +5 preserved chimerism. Most chimeras survived GVHD-free for >200 days. Prolonged persistence of host-reactive T cells in mice (CY2 on day +5) permitted a reduction to be made in engraftment-essential irradiation dose and preserved a strong graft-vs-leukemia effect of transplantation. CONCLUSION: Acute GVHD can be prevented in mice by a single properly timed posttransplantation low-dose CY administration.

Mesenchymal stromal cells lose their immunosuppressive potential after allotransplantation.

OBJECTIVE: The stem cell fraction of mesenchymal stromal cells (MSCs) is capable of self-renewal and under inductive conditions differentiates into bone, cartilage, hematopoietic stroma, and other mesenchymal tissues. Therefore, MSCs represent a promising source for hard tissue repair therapies. MSCs are also immunosuppressive and prevent activation of allogeneic lymphocytes in vitro. Thus it has been suggested that they might be able to engraft in allogeneic recipients and downregulate recipients' immunity. In this study we examined whether MSCs retain their immunomodulating properties in vivo after allotransplantation. MATERIALS AND METHODS: MSCs were propagated from bone marrow (BM), placenta, or umbilical cord tissues. Using a murine parental-into-F1 model of graft-vs-host disease (GVHD) we tried to control GVHD by intravenous transplanting parental or recipient MSCs together with parental lymphocytes (day 0) and on days +7 and +14. MSCs' immunosuppressive potential in vivo was also examined by comparing their ability to construct ectopic bone after local transplantation with osteogenic inductor (demineralized bone matrix) under the kidney capsule of syngeneic and allogeneic recipients. RESULTS: Repeated IV MSC injections failed to reduce GVHD-related recipient mortality. Local implantation of MSCs propagated from BM, placenta or umbilical cord resulted in ectopic bone formation in syngeneic recipients and in transplant rejection by allogeneic mice. CONCLUSION: MSCs lose their immunosuppressive potential in mismatched setting.

A 3D rotary renal and mesenchymal stem cell culture model unveils cell death mechanisms induced by matrix deficiency and low shear stress.

BACKGROUND: In epithelial and endothelial cells, detachment from the matrix results in anoikis, a form of apoptosis, whereas stromal and cancer cells are often anchorage independent. The classical anoikis model is based on static 3D epithelial cell culture conditions (STCK). METHODS: We characterized a new model of renal, stromal and mesenchymal stem cell (MSC) matrix deprivation, based on slow rotation cell culture conditions (ROCK). This model induces anoikis using a low shear stress, laminar flow. The mechanism of cell death was determined via FACS (fluorescence-activated cell sorting) analysis for annexin V and propidium iodide uptake and via DNA laddering. RESULTS: While only renal epithelial cells progressively died in STCK, the ROCK model could induce apoptosis in stromal and transformed cells; cell survival decreased in ROCK versus STCK to 40%, 52%, 62% and 7% in human fibroblast, rat MSC, renal cell carcinoma (RCC) and human melanoma cell lines, respectively. Furthermore, while ROCK induced primarily apoptosis in renal epithelial cells, necrosis was more prevalent in transformed and cancer cells [necrosis/apoptosis ratio of 72.7% in CaKi-1 RCC cells versus 4.3% in MDCK (Madin-Darby canine kidney) cells]. The ROCK-mediated shift to necrosis in RCC cells was further accentuated 3.4-fold by H(2)O(2)-mediated oxidative stress while in adherent HK-2 renal epithelial cells, oxidative stress enhanced apoptosis. ROCK conditions could also unveil a similar pattern in the LZ100 rat MSC line where in ROCK 44% less apoptosis was observed versus STCK and 45% less apoptosis versus monolayer conditions. Apoptosis in response to oxidative stress was also attenuated in the rat MSC line in ROCK, thereby highlighting rat MSC transformation. CONCLUSIONS: The ROCK matrix-deficiency cell culture model may provide a valuable insight into the mechanism of renal and MSC cell death in response to matrix deprivation.

Prevention of diabetes in nonobese diabetic mice by nonmyeloablative allogeneic bone marrow transplantation.

OBJECTIVE: Autoimmune diabetes in nonobese diabetic (NOD) mice can be prevented by allogeneic bone marrow transplantation (BMT) from diabetes-resistant murine strains. Donor-specific tolerance can also be induced by BMT; however, clinical application of nonmyeloablative conditioning prior to BMT may be essential for reducing transplant-related toxicity and mortality. In this study, we have attempted to treat autoimmunity using a new nonmyeloablative regimen for BMT. MATERIALS AND METHODS: Naïve NOD were irradiated with 650 cGy and injected intravenously (i.v.) with splenocytes from overtly diabetic NOD mice for induction of diabetes mellitus. Three days later, experimental mice received allogeneic C57BL/6 or (C57BL/6 x BALB/c) F1 bone marrow (BM) cells i.v. for intentional activation of donor-reactive cells, and 24 hours later intraperitoneal injection of cyclophosphamide (CY) for selective depletion of alloreactive cells. In order to induce chimerism, recipients were given a second IV inoculum of donor BM 1 day after CY. RESULTS: Our method of nonmyeloablative BMT converted recipients to full or to mixed chimeras and prevented development of diabetes. Although NOD mice treated with 200 mg/kg CY died of graft-vs-host disease (GVHD), we observed diabetes-free survival for >300 days in 90% of C57BL/6 --> NOD BM chimeras treated with 60 mg/kg CY. CONCLUSION: Our data show that allogeneic BMT after reduced-intensity conditioning based on deletion of activated donor-reactive host cells by means low-dose CY results in prevention of autoimmune diabetes by converting recipients to stable, GVHD-free BM chimeras.

Depletion of donor-reactive cells as a new concept for improvement of mismatched bone marrow engraftment using reduced-intensity conditioning.

OBJECTIVE: New nonmyeloablative strategies to improve acceptance of mismatched bone marrow (BM) may compensate for the inadequate supply of compatible grafts. Recently we proposed to facilitate engraftment of mismatched BM by selective depletion of activated donor-reactive host cells with cyclophosphamide (CY). Here we have compared engraftment of allogeneic BM after depletion of antigen-activated host lymphocytes by CY, with BM engraftment following general immunosuppression by the same CY dose. MATERIALS AND METHODS: Naive or mildly irradiated BALB/c mice were primed with C57BL/6 BM cells (day 0), treated with CY in order to deplete activated T cells (day 1), and transplanted with a second C57BL/6 BM inoculum (day 2) in order to achieve BM engraftment. Alternatively, mice received an equal dose of donor BM cells in a single injection one day after the same CY dose. Treated animals were repeatedly tested for persistence of donor cells in the blood. RESULTS: Depletion of alloantigen-primed lymphocytes by 200 mg/kg CY provided stable GVHD-free engraftment of allogeneic BM in nonirradiated mice, while immunosuppressive treatment with the same CY dose alone resulted in BM rejection. Low-dose irradiation before priming with donor BM allowed the tolerance-inducing CY dose to be reduced to 100 mg/kg. Alloantigen-primed lymphocyte depletion (APLD) by a reduced CY dose resulted in engraftment of donor BM after a significantly lower irradiation dose than treatment with irradiation and CY alone. CONCLUSION: Our results demonstrate that conditioning that focuses on APLD has a definite advantage over general immunosuppression with CY and radiation therapy.

Nonmyeloablative allogeneic bone marrow transplantation as immunotherapy for hematologic malignancies and metastatic solid tumors in preclinical models.

OBJECTIVE: We previously demonstrated that a combination of mild total lymphoid irradiation (TLI) with selective depletion of the host's donor-reactive cells allows for stable and graft-vs-host disease (GVHD)-free engraftment of allogeneic bone marrow (BM). In this study, we investigated the efficacy of this nonmyeloablative strategy for BM transplantation (BMT) as immunotherapy for minimal residual disease. MATERIALS AND METHODS: BALB/c mice inoculated with leukemia (BCL1) or breast carcinoma (4T1) cells were conditioned for BMT with TLI (200 cGy) followed by priming with donor (C57BL/6) BM cells on day 1, and by injection with 200 mg/kg cyclophosphamide on day 2. After conditioning (day 3), recipients were transplanted with BM cells from the same donor. Treated animals were monitored for 230 days for survival, development of leukemia/solid tumor, and GVHD. RESULTS: BMT converted the mice to complete chimeras and prevented development of leukemia in 90% of recipients and locally growing breast carcinoma in 40% of the mice. Immunization of donors of the second BM with 4T1 cells prevented development of breast carcinoma in 80% of 4T1 inoculated mice. Fewer animals treated for malignancy by nonmyeloablative BMT died of GVHD than those treated by myeloablative BMT. However, late GVHD-related mortality in mice treated for leukemia was higher than after nonmyeloablative BMT to naive recipients (p < 0.00001). Infusion of host-type anti-donor immune lymphocytes 8 days after BMT improved the survival of recipients treated for leukemia without affecting engraftment and the graft-vs-leukemia potential of donor BM. CONCLUSIONS: Effective eradication of malignant cells can be achieved following allogeneic BMT after nonmyeloablative conditioning.

CD40 ligand-specific antibodies synergize with cyclophosphamide to promote long-term transplantation tolerance across MHC barriers but inhibit graft-vs-leukemia effects of transplanted cells.

OBJECTIVES: We previously demonstrated that allogeneic bone marrow transplantation (BMT) after low-dose total lymphoid irradiation (200 cGy) and depletion of donor-reactive cells with cyclophosphamide (Cy) converted recipients to graft-vs-host disease (GVHD)-free chimeras tolerant to donor skin grafts. BMT also generated strong graft-vs-leukemia (GVL) response. However, clinical application of the protocol was hampered by the requirement for a relatively high dose of Cy (200 mg/kg). In this study we have tried to minimize the Cy dose by a concomitant blockade of CD40-CD40L interaction. MATERIALS AND METHODS: Mildly irradiated BALB/c mice were primed with C57BL/6 BM cells (BM(1)) and skin graft on day 0, injected with Cy (200 mg/kg or less) on day 1, and transplanted with a second C57BL/6 BM cell inoculum (BM(2)) on day 2. CD40L-specific antibody (MR1) was given with BM(1), BM(2), and 2 days later. Treated animals were monitored for survival, chimerism, and skin allograft rejection. The GVL potential of transplanted cells was examined in mice inoculated with BCL1 leukemia cells before irradiation. RESULTS: Blocking CD40-CD40L interaction with MR1 mAb allowed the reduction of a tolerance-generating Cy dose by 50%. Unfortunately, adding MR1 to the protocol reduced the GVL potential of the transplanted cells. Neither low-dose Cy nor antibodies alone could downregulate donor or recipient immune response. CONCLUSIONS: CD40L-specific antibodies synergize with Cy to induce bilateral transplantation tolerance. Therefore, their use may be beneficial for safer allogeneic BMT for nonmalignant indications. However, due to MR1-associated reduction of GVL effects, MR1 should be considered with caution as conditioning for BMT for leukemia-bearing recipients.

Visualization of immune response kinetics in full allogeneic chimeras.

BACKGROUND: Donor Lymphocyte Infusion (DLI) is a well-recognized tool for augmentation of the anti-leukemia effect after mismatched bone marrow transplantation. Experimental results show, however, that DLI efficacy is strongly dependent on the number of donor hematopoietic cells persisting in recipient after transplantation. It is strong in mixed chimeras and relatively weak in full chimeras (FC) that replace host antigen-presenting cells by donor antigen-presenting cells. In this study we applied a new in vivo cytotoxicity monitoring method for evaluation of the changes in FC anti-host immunity after co-transplantation of donor and host hematopoietic cells together. METHOD: Full hematopoietic chimeras and naïve control mice were transplanted with a mixture of equivalent numbers of donor and recipient or donor and third party splenocytes labeled by a cell-permeable fluorescent dye CFDA-SE. The animals were sacrificed at various time points, and their splenocyte suspensions were prepared, depleted of red blood cells, stained with allophycocyanin-labeled anti-H2(b) antibodies, and analyzed using fluorescence-activated cell sorting. The immune response was assessed according to the percentage of single positive CFDA-SE(+)/ H2(b-) cells of all CFDA-SE(+) cells. RESULTS: FC grafted with splenocytes from similar FC mixed with splenocytes from naïve host-type or third-party-type mice rejected host cells within 14 days, and third-party cells within 7 days. NK cell depletion in vivo had no influence on host cell rejection kinetics. Co-infusion of host-type splenocytes with splenocytes obtained from naïve donor-type mice resulted in significant acceleration of host cell rejection (10 days). Naïve mice rejected the same amount of allogeneic lymphocytes within 3 days. CONCLUSIONS: Proposed method provides a simple and sensitive tool to evaluate in vivo post-transplant cytotoxicity in different experimental settings. The method demonstrates that FC is specifically deficient in their ability to reject host lymphocytes even when antigen-presenting host cells are provided. DLI improve anti-host immune response in FC but can not restore it to the level observed in naïve donor-type mice.

A novel dynamic matrix detachment model reveals a shift from apoptosis to necrosis in melanoma cells.

Anchorage-independence is a hallmark of invasive cancer. The setback of the classical poly-HEMA static matrix detachment (SMD) anoikis model is the absence of dynamic fluid circulation, resulting in cell aggregates. We addressed this problem by developing a novel 3D cell culture dynamic matrix detachment (DMD) model with a turbulent-free laminar flow, yielding a very low shear stress. In this study, we focused on melanoma cells where apoptosis was evaluated both via annexin V flow cytometry and caspase cleavage. The DMD model was superior to SMD in the induction of melanoma cell death and in revealing a shift from apoptosis to necrotic cell death, as evident by failure to activate caspase 9 and a decrease in annexin V stain. Combination of DMD with cisplatin could further accentuate necrotic cell death in cisplatin-resistant melanoma cells. Thus, the DMD model may be a useful matrix deprivation model to identify necrotic vs. apoptotic cell death pathways.

Pancreatic acinar and islet cell infection by low-dose SV40 administration.

OBJECTIVES: Viral vector uptake into the pancreas is rare. The few viral vectors reported to transduce in vivo pancreatic islets after systemic injection required additional physical measures, such as direct pancreatic injection or hepatic vessel clamping. Because pancreatic islet uptake of the human polyomavirus family member BK virus was previously reported in hamsters after systemic administration, we hypothesized that SV40, a polyomavirus member remarkably similar to BK virus, may also infect the pancreas. METHODS: We injected intravenously a low dose of SV40, unaided by any other physical or chemical means, and evaluated viral uptake by pancreatic islets and pancreatic exocrine tissue via polymerase chain reaction, Western blot, electron microscopy, immunofluorescent microscopy, and protein A-gold immunocytochemistry. RESULTS: Pancreatic uptake of SV40 was comparable to other major organs (ie, liver and spleen). SV40 viral particles were detected in both pancreatic islets and acini. In pancreatic islets, all islet cell types were infected by SV40, albeit the infection rate of glucagon-producing alpha cells surpassed beta- and delta-islet cells. Low-dose SV40 administration was not sufficient to induce heterologous gene expression in the pancreas. CONCLUSIONS: Our study shows that pancreatic islet and acinar cell uptake of SV40 is feasible with a single, low-dose intravenous injection. However, this dose did not result in gene delivery into the murine pancreas.

Depletion of alloantigen-primed lymphocytes overcomes resistance to allogeneic bone marrow in mildly conditioned recipients.

OBJECTIVE: Successful implantation of allogeneic bone marrow (BM) cells after nonmyeloablative conditioning would allow to compensate for the inadequate supply of compatible grafts and to reduce mortality of graft-vs.-host disease (GVHD). Recently, we proposed to facilitate engraftment of mismatched BM by conditioning for alloantigen-primed lymphocyte depletion (APLD) with cyclophosphamide (CY). Here we summarize the experimental results obtained by this approach. MATERIALS AND METHODS: Naive or mildly irradiated BALB/c mice were primed with C57BL/6 BM cells (day 0), treated with CY (day 1) to deplete alloantigen-primed lymphocytes, and given a second C57BL/6 BM transplant (day 2) for engraftment. Recipients were repeatedly tested for chimerism in the blood and followed for GVHD and survival. The protocol was also tested for inducing tolerance to donor tissue and organ allografts, and for treatment of leukemia, breast cancer, and autoimmune diabetes in NOD mice. RESULTS: APLD by 200 mg/kg CY provided engraftment of allogeneic BM from the same donor in 100% mildly irradiated recipients. Eighty percent chimeras remained GVHD-free more 200 days. All chimeras accepted permanently donor skin grafts and donor hematopoietic stromal progenitors. Allogeneic BM transplantation (BMT) after APLD had a strong therapeutic potential in BALB/c mice harboring malignant cells and in autoimmune NOD recipients. Tolerance-inducing CY dose could be reduced to 100 mg/kg. Conditioning for APLD resulted in engraftment of allogeneic BM after a significantly lower radiation dose than treatment with radiation and CY alone. CONCLUSION: Our results demonstrate that conditioning for APLD has a definite advantage over general immunosuppression with CY and radiation therapy.