NRG mice injected into the skin with SmyleDCs and SmartDCs and analyzed by non-invasive optical imaging analyses showed gradual disappearance of the iDCs within 1 month after administration. Mice maintained in observation for up to 100 find more days post-injection showed no signs of disease. In summary, the results obtained with ID-LVs, were remarkably similar to previous observations using IC-LVs for genetically

programming iDCs [10]. Thus, as a logical progression, the two types of safety-enhanced ID-LVs were further compared regarding their capabilities to induce DCs with different immunologic properties (Table 1). The combination of recombinant signaling pathway GM-CSF/IFN-α has been extensively compared with GM-CSF/IL-4 for

generation of DCs [37], [38], [39] and [40]. In their work for the development of therapeutic DC vaccines against hepatitis C virus (HCV), Santini and collaborators proposed that IFN-α-DCs were “directly licensed” or more readily matured for cross-presenting low amounts of viral antigens by mechanisms likely involving the expression of IL-12 [39]. Our results comparing the autonomous ID-LV expression of GM-CSF/IFN-α with GM-CSF/IL-4 confirms some of the previous findings obtained with the recombinant cytokines, although in terms of expression of relevant immunologic markers and inflammatory cytokines the Histone demethylase two types of iDCs were remarkably similar (Table 1). Recent work in our laboratory analyzing the RNA expression pattern of conventional IL-4-DCs versus SmartDCs showed for the later up-regulation of several downstream genes involved with interferon regulatory circuits (Sundarasetty et al., in preparation), explaining the convergence of SmartDCs with SmyleDCs. The SmyleDC immunophenotypic characterization corroborated with previous findings that DCs grown in

the presence of IFN-α (instead of IL-4) lacked expression of CD209 (DC-SIGN). These results was expected, as DC-SIGN expression is dependent on the IL-4 cytokine but negatively regulated by IFN-α [41]. DC-SIGN is known to bind to several types of viruses and although its function might be related to T cell activation, pathogens seem to use this route to “hijack” DCs and modulate them [42]. Thus, since DC-SIGN is a potential target for the capture of DCs by pathogens, its down-regulation in a cell vaccine might be a positive hallmark enabling them to escape pathogen infection. It was previously reported that DCs generated in the presence of IFN-α displayed NK-like cytotoxicity and a mature immunephenotype [43]. SmyleDCs were not able to lyse K562 cells directly, but modestly stimulated NK cells in vitro ( Fig. S4a).