TNFα and IFNγ positive T-cells with the phenotype Ki67+ and Bcl-2-low post HCV challenge for animals V-91A025, V-0712, R-4x0300, R-4x0329 and R-4x0352. A) Frequency of TNF-α and IFN-γ positive CD8+ T-cells that are Ki-67+ and Bcl2low. B) Frequency of TNF-α and IFN-γ positive CD4+ T-cells that are Ki-67+ and Bcl2low. For detection of HCV-specific proliferating cells PBMCs were stimulated with HCV peptide pools representing NS3, NS5A, and NS5B. Brefeldin (10ug/mL) was added after 18 hours in order to arrest cytokine release and incubation was continued for a total of 24 hours. Stimulated cells were then stained with monoclonal antibodies specific to the following: CD3-Alexa 700, CD4-Pacific Blue, CD8-APC-Cy7, HLA-DR-PE-Cy7, CD38-PE-Cy5, TNFα-APC, IFNγ- APC, Ki-67-FITC, Bcl2-PE.