MODULATION OF IMMUNE-RESPONSES TO HEPATITIS-C VIRUS ENVELOPE E2 PROTEIN FOLLOWING INJECTION OF PLASMID DNA USING SINGLE OR COMBINED DELIVERY ROUTES

Different delivery routes of plasmid DNA may result in the induction o f differential humoral and cellular immunity. We have studied the infl uence of two main routes of plasmid injection, performed intramuscular ly and intraepidermally using a gene gun, for the induction of immune responses specific to hepatitis C virus (HCV) envelope protein E2. Thr ee plasmids expressing different immunogenic domains of E2 (amino acid s [aa] 384-443, aa 504-555, and aa 384-746) were injected into BALB/c mice according to five different protocols using various combinations of intramuscular (i.m.) or intraepidermal (i.e,) primary and booster i njections. Seroconversion rates, antibody titers and isotypes, epitope recognition, and T-helper (Th) release cytokine profiles were analyze d. Antibody titers and epitope recognition were linked to either or bo th the nature of the immunogen expressed and the delivery route chosen . In all cases, the lowest antibody titers were obtained using single i,m.-based protocols. Independently of the antibody titers generated, only some specific i.e.-combined delivery routes induced antibodies ab le to recognize determinants located in the N-terminal of E2 (aa 384-4 11 and aa 411-437) and mimicked by synthetic peptides, By contrast, th e antibody isotypes and the splenic cytokine production identified wer e independent of the plasmids used and the delivery route implemented. All conditions resulted in Th-l like responses suggested by the exclu sive detection of IgG2a and 2b antibodies and the production of interf eron gamma (INF-gamma) but no interleukin-4 (IL-4). Overall, our resul ts suggest that the combination of i,m, and i.e. delivery routes provi des the most efficient way to induce a broad immune response against H CV-E2.