Visual demonstration of hepatitis C virus-specific memory CD8(+) T-cell expansion in patients with acute hepatitis C.

Hepatitis C virus (HCV)-specific CD8(+) T cells in peripheral blood mononuclear cells (PBMCs) from patients infected with HCV were quantitatively analyzed by flow cytometry using an HLA-B*3501-HCV epitope tetrameric complex. In chronic hepatitis C, tetramer(+)CD8(+) T cells were detected at frequencies ranging from 0.05% to 0.12% of total CD8(+) T cells. The number of tetramer(+)CD8(+) T cells in acute phase PBMCs from patients with acute hepatitis C was about 3 to 5 times higher than in recovery phase PBMCs from the same patients and in PBMCs from patients with chronic hepatitis C. Expanding tetramer(+)CD8(+) T cells in PBMCs from patients with acute hepatitis C express a CD28(+)CD45RA(-) memory T-cell phenotype. In contrast, tetramer(+)CD8(+) T cells in PBMCs from patients with chronic hepatitis C did not predominantly express this phenotype. These tetramer(+)CD8(+) T cells did not have perforin in their cytoplasma. The present study visually showed that a high number of circulating HCV-specific CD8(+) T cells in acute phase PBMCs from patients with acute hepatitis C are mostly memory T cells.