A DNA microarray-based analysis of immune-stimulatory and transcriptional responses of dendritic cells to KALA-modified nanoparticles

Technologies for the transfection of antigen-encoding genes into the dendritic cells, and subsequent immune-activation are both prerequisites for a successful DNA vaccine. We herein report on the density-dependent enhancement of transgene expression by the simple modification by stearyl-conjugated KALA, an α-helical peptide (STR-KALA), onto a lipid envelope-type nanoparticle (the R8-MEND, an octaarginine-modified multifunctional envelope-type nano device). The enhanced transgene expression in the KALA-modified R8-MEND (R8/KALA-MEND) cannot be explained by cellular uptake and nuclear delivery efficacy. Thus, the post-nuclear delivery process (i.e. transcription), but not intracellular trafficking processes attributed the enhanced transfection efficacy. Microarray analyses revealed that transfection with the R8/KALA-MEND resulted in a greater perturbation in host genes expression in comparison with the R8-MEND and that this effect was time-dependent. Further pathway analyses in the category of transcription-related genes and a gene ontology analysis indicated that the R8/KALA-MEND stimulated the expression of transcription factors that are closely related to immune-activation (i.e. NF- kB and STAT). Inhibition of the transfection efficacy by blockage of the STAT pathways revealed that the enhanced transcription activity is the result of immune-stimulation. Collectively, the R8/KALA-MEND mounts a "switch-on" function that triggers signal transduction forward to the immune-stimulation analogous to an adjuvant, and consequently elicits active transcription.