After washing, the plates were blocked with 1% BSA (Sigma-Aldrich, St. Louis, MO) in PBS for 1 hr at 37°C. Then the plates were washed and dilutions of sera were incubated for 2 hrs at 37°C. Antibodies were detected with a 1/1000 dilution in 1% BSA/PBS of the

required goat anti-species-specific HRP conjugate (IgG H+L: Jackson Immunoresearch Laboratories, West Grove, PA; IgG1, IgG2a: Serotec, Oxford, UK). After each incubation time, the plates were washed six times with PBS/0.05% Tween-20 (Sigma-Aldrich). O-phenylenediamine dihydrochloride (Sigma-Aldrich) and hydrogen peroxide were used to develop the color reaction. The optical density PLX4032 clinical trial (OD) was read at 490 nm after the reaction was stopped with 1 N HCl. An IgG2a monoclonal antibody specific for core protein amino acids 1-120 (Clone 0126, Biogenesis Ltd., Poole, England) and hepatitis C-negative or pre-immune sera were run in parallel with all samples tested as negative control. OD values of at least 2 standard deviations above the mean OD from the pre-immunization sera were considered positive for an HCV-antibody response. IFN-γ intracellular staining CD8+ CTL responses were assessed by measuring the mouse IFN-γ production using intracellular staining. The intracellular

procedures were done according to Caltag Laboratories protocol. Briefly, PBMCs isolated from fresh blood or the splenocytes of immunized mice were cultured in complete RPMI media in the presence of 10 μg/ml brefeldin A (Sigma) and stimulated Torin 1 concentration with core, E1 and E2 protein, core peptides, or vaccinia poly HCV (NIH AIDS, Cat# 9426)

expressing HCV-1 Core, E1, E2, P7 and NS2 truncated. Unstimulated or empty vaccinia stimulated cells were used as a negative control. PMA/ION stimulated cells were used as a positive control. Eighteen hrs after Reverse transcriptase incubation at 37°C, the cells were washed with PBS/2% FCS/0.01% sodium azide and surface-stained for 15 min with PE-labeled monoclonal antibody against mouse CD3+, TC-labeled antibody to mouse CD8+ or CD4+ (Caltag Laboratories, Hornby, ON). The cells were washed as above, fixed and permeabilized using Caltag reagent A and B fixation-permeabilization solutions (Caltag Laboratories). The cells were stained intracellularly with anti-mouse IFN-γ FITC-labeled Ab and incubated for 30 min (in the dark) at 4°C. Following washing, cells were analyzed in a FacScan flow cytometer (Becton Dickinson, Mississauga, ON). An increase of 0.1% of IFN-γ producing cells over the unstimulated control or empty vaccinia virus stimulated cells were considered as positive response to vaccination. IFN-γ ELISPOT The ELISPOT assay was performed according to Mabtech protocol. Briefly, a 96-well microtiter plate was coated with mouse anti-IFN-γ monoclonal antibodies (10 μg/ml in PBS). The cells (250,000/well) were added to the plate with cross bonding stimulants.