Optimization of in vitro cultivation strategies for human adipocyte derived stem cells.

With adipose-derived stem cells being in the focus of research in regenerative medicine, the need arises for fast reliable cultivation protocols. We have tested the cultivation of human adipose-derived stem cells in endothelial cell growth medium prior to induction and differentiation, against the long-established use of DMEM/F12 medium-based cultivation protocols. We found that cultivation in endothelial cell growth medium not only accelerates growth before induction and differentiation, but also allows shorter induction and differentiation times than those following precultivation with DMEM/F12 medium with regard to the formation of mature adipocytes and to the viability undifferentiated cells. These results were first observed morphologically but could be confirmed by performing adiponectin ELISA and cell proliferation assays.

Ex vivo generation of cytotoxic T lymphocytes specific for one or two distinct viruses for the prophylaxis of patients receiving an allogeneic bone marrow transplant.

Human adenovirus (AdV) infection and EBV-lymphoproliferative disease (LPD) are serious complications following allogeneic stem cell transplantation. In the healthy individual these viruses cause minor, self-limiting diseases but in the immunocompromised patient they are responsible for significant morbidity and mortality. The limitations of anti-viral drugs and a better understanding of the cellular immune response to viral pathogens have prompted interest in developing adoptive immunotherapy for transplant patients. Ex vivo expanded cytotoxic T lymphocytes (CTLs) specific for EBV have been used effectively both as prophylaxis against EBV-LPD and as treatment of established EBV+ lymphoma. To generate CTLs specific for AdV, we infected immature dendritic cells with virus, in the presence of lipid, and subsequently used these cells to stimulate PBMNCs. Cytotoxicity assays showed that the resulting CTLs specifically lysed AdV-expressing targets and that this was mediated predominantly by CD4+ T cells. To generate CTLs specific for both AdV and EBV, we developed a CD40 ligand co-culture system to infect B-lymphoblastoid cell lines (LCLs) with high efficiency. PBMNCs from healthy AdV-seropositive donors were stimulated weekly with autologous AdV+-LCLs. Chromium release assays demonstrated that the resultant CTLs had specificity against both EBV and AdV and that this was mediated by both CD4+ and CD8+ T cells. Our findings have potential implications for post-transplant AdV and EBV immunotherapy in recipients of allogeneic stem cell transplants.

Leukemic dendritic cells generated in the presence of FLT3 ligand have the capacity to stimulate an autologous leukemia-specific cytotoxic T cell response from patients with acute myeloid leukemia.

It has been proposed that adoptive immunotherapy, for the treatment of relapsed AML, with cytotoxic T lymphocytes which show a relative specificity for the leukemic cells may have the advantage of maximizing the beneficial anti-leukemic effect whilst minimizing the probability of graft-versus-host disease. In this study we differentiated peripheral blood AML cells in vitro into functional dendritic cells (DCs), as demonstrated by cell morphology, immunophenotype and functional activity, in the presence of GM-CSF, IL-4, TNF-alpha and FLT3 ligand. Such DCs could be differentiated from 77% of AML patients, irrespective of their FAB classification and clinical status and, in all cases tested, the DCs were shown to derive from the leukemic clone by FISH analysis. Importantly, from >60% of AML patients, autologous T lymphocytes stimulated with these in vitro generated leukemic DCs displayed specific cytotoxic activity against AML blasts but low reactivity against autologous non-leukemic targets and HLA-matched normal PBMNCs therefore suggesting that the CTLs were AML-specific. The use of FLT3 ligand in our system resulted in a significantly higher number of leukemic DCs as compared to cultures from which FLT3 ligand was omitted which is obviously advantageous if large numbers of specific CTLs are to be generated in the shortest possible time.

Interferon alpha in combination with GM-CSF induces the differentiation of leukaemic antigen-presenting cells that have the capacity to stimulate a specific anti-leukaemic cytotoxic T-cell response from patients with chronic myeloid leukaemia.

Although interferon alpha (IFN-alpha) is able to induce haematological remission in 60-80% of patients with chronic myeloid leukaemia (CML) in early chronic phase, major cytogenetic remissions are only achievable in 30-40%. Recent clinical data suggest that the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) to IFN-alpha therapy can significantly improve the cytogenetic response in some patients, although the mechanism remains unknown. We hypothesized that the combination of GM-CSF and IFN-alpha induces the differentiation of dendritic cells, which subsequently stimulates a specific anti-leukaemic response. Monocytes from CML patients were cultured in GM-CSF and interleukin (IL)-4 (GM/IL-4)or in GM-CSF and IFN-alpha (GM/IFN-alpha). After 7 d, the number of cells exhibiting typical antigen-presenting cell (APC) morphology was equal in both groups, and fluorescence in situ hybridization (FISH) analysis confirmed that the APCs generated with GM/IFN-alpha were of leukaemic origin. Phenotypically, both sets of APCs expressed typical surface markers; however, CD86, CD83, CD11c, HLA-ABC and HLA-DR expression was significantly higher in the GM/IFN-alpha APCs, whereas CD1a expression was significantly lower. In mixed lymphocyte reactions (MLR), GM/IFN-alpha APCs stimulated the proliferation of allogeneic T cells significantly better than GM/IL-4 APCs. However, both groups of APCs stimulated autologous T-cell proliferation equally. Finally, we assessed the ability of GM/IFN-alpha APCs to induce a leukaemia-specific cytotoxic T-cell response. Some samples generated cytotoxic T lymphocytes (CTLs) that specifically lysed bcr-abl-positive target cells. These data show that the combination of GM-CSF and IFN-alpha, when used in vitro, induces the differentiation of malignant APCs with potent T-cell stimulatory capacity. Although there is no in vivo evidence to support these findings, it is possible that, when administered to CML patients, GM-CSF in combination with IFN-alpha results in the generation of highly stimulatory leukaemic APCs.