Therapeutic DNA vaccine coding interleukin-15 and epitopes can enhance cellular immune response in chronic hepatitis C patients in vitro
Purpose: It is well known that the immune responses are impaired in chronic hepatitis C(CHC) patients by various mechanisms. To overcome severe immune tolerance in CHC patients, activation of immune system should be recommended by not only antigenic epitope but also stimulating factor. In the previous study, we have selected 10 CTL epitopes from hepatitis C virus(HCV) protein and constructed them into pVAX vector for clinical purpose with human IL-15 gene. In this study, DNA vaccines have been evaluated their efficacy in inducing cellular immunity from patients' PBMCs by expressing the genes on dendritic cell. Materials and Methods: Human IL-15 and epitope gene have been cloned into single plasmid together or into dual plasmid vector separately. Dendritic cells were derived and maturated from CHC patients' monocytes and transfected with DNA vaccine vector by electorporation. Epitope-specific CTL responses were measured by counting the IFN-γ secreting cells among CD8+ T cells by ELISPOT analysis and flow cytometry after in vitro culture for 5 days. Result: DNA vaccine coding epitope and IL-15 recruited strong CTL responses after in vitro stimulation, while mock DNA vaccine vector didn't induce the epitope-specific IFN-γ secretion from CD8+ T cells. The increase of IFN-γ secretion accompanied with increase of 4-1BB expression and granzyme B contents on CD8+ T cells. Interestingly, single construction of DNA vaccine vector shows bigger immune responses than dual construction of that. Conclusion: These result indicated that DNA vaccine coding epitope and IL-15 could recruit cellular immunity CHC patient in vitro, and shows a possibility of new therapeutics to overcome immune suppression for chronic hepatitis caused by HCV.