As conventional CD8 T cells possess cytotoxic function that is essential in the host defense against viral infection, we decipher the cytotoxic capacity in CCR4+CD8+ T cells in CHB patients by analyzing CD107a expression and perforin and granzyme B production after performing 10 days of PBMC culture in the presence of HBs overlapping peptides and IL-2. This evidence concerns the gene PRF1 and viral infectious disease.