Figure 4. Detectable frequencies of HCV-specific peripheral T lymphocytes are induced by immunization. Cytokine production, by intracellular cytokine staining, following antigen-matched peptide stimulation revealed HCV-specific T cells in peripheral blood 2 wk PIR, compared with baseline, by flow cytometric analysis. CD3+/CD4+/CD8- (Th1) or CD3+/CD8+/CD4- (CTL) cells were counted as cytokine-positive if they produced one or more of IFNγ, TNFα, or IL-2. Total cytokines responses are represented as stacked responses to demonstrate breadth across multiple antigens (■, NS3/4A; ■, NS4B; ■, NS5A; ■, NS5B).