On

day 7, cells transduced with the vector ID-LV-G2α showed typical DC morphology similar to SmartDCs generated with the ID-LV-G24 vector, but the cells were conspicuously smaller ( Fig. 1a). We named these cells “self-differentiated myeloid-derived lentivirus-induced DCs”, or SmyleDCs. Selleckchem VE821 The number of immunophenotypically stable iDCs recovered 14 days after transduction was approximately 12% of the number of monocytes used for transduction, which probably reflects the LV transduction efficiency leading to selective advantage of autonomously differentiated DCs ( Fig. 1b). Measurement of the transgenic cytokines that accumulated in the cell supernatant of SmyleDC and SmartDC cultures demonstrated that the levels of GM-CSF (1–2 ng/ml) were constant and comparable between the two cultures ( Fig. 1c). However, whereas the levels of IFN-α remained stable (4–6 ng/ml) from days 7 to 14, IL-4 levels substantially decreased ( Fig. 1c). The more persistent co-expression of both transgenes by SmyleDCs may explain the slightly higher stability of SmyleDCs in vitro. In addition to the cytokines expressed due to the lentiviral gene delivery, we also evaluated if other cytokines were endogenously produced by iDCs. Analyses of ten cytokines accumulated in the cell culture medium were performed by bead array (Fig. 1d). Cytokines detectable in SmyleDC and SmartDC

cultures were IFN-γ, IL-2, IL-5, IL-6, IL-8 (the later is a chemotactic factor and was produced at significantly higher levels by SmyleDCs than by SmartDCs). TNF-α, IL-1β and IL-10 were not detectable. The mixed pattern Trichostatin A clinical trial of the cytokines indicated that several types of immune effectors (CTL, Th1, Th2, NK, whatever B cells, neutrophils, eosinophils) could be potentially stimulated by iDCs. Flow cytometry analyses of class II Major Histocompatibility

Complex (MHCII or HLA-DR for humans) and of co-stimulatory ligands such as CD80 and CD86 provide important correlates of the DC differentiation and functional status. Immunophenotypic analyses of SmyleDCs and SmartDCs showed high frequencies (70%) of cells expressing these immunorelevant DC markers at day 7 of culture, which further increased for HLA-DR and CD86 on day 14 (CD80 expression decreased slightly) (Figs. 2a, b, S4a and b). As expected, CD14, a monocyte marker, was down-regulated throughout the culture. SmyleDCs showed significantly lower expression of CD209 (also known as dendritic cell specific ICAM 3-Grabbing non-integrin, DC-SIGN) than SmartDCs. As IL-4 is involved in up-regulation of CD209 in conventional DCs generated with GM-CSF/IL-4, this recapitulates previous findings described for DCs cultured in the presence of GM-CSF/IFN-α [27]. CD123 (IL-3 receptor) which is a putative plasmacytoid DC (pDC) marker, was expressed at low levels (7%), indicating that, despite expression of IFN-α, SmyleDCs maintained essentially myeloid DC characteristics (Figs. 2a, b, S4a and b).