Effects of lamivudine on the hepatitis B virus specific CD8⁺ cytotoxic T lymphocyte responses via peptide-MHC tetrameric complexes assay

Lamivudine, an oral nucleoside analogue, inhibits hepatitis B virus (HBV) replication. It has been shown to be able to restore T cell responsiveness and to induce a type 1 T helper cell (Th 1) immunity in chronic HBV patients. To further examine the effects of lamivudine on cytotoxic T lmphocyte (CTL) responses, two HBV antigenic peptide-HLA-A2 tetrameric complexes containing peptides derived from HBV core protein (residues 18-27; FLPSDFFPSV) and polymerase (residue 551-559; YMDDVVLGA) were constructed. These two tetramers were used to serially determine the frequency of HBV antigen-specific CD8⁺ T cells before and during the treatment of lamivudine. The specificity of these tetramers was confirmed by (a) nonstaining of CD8⁺ T cells from HLA-A2-negative HBV patients, (b) having variable frequency data in the different teteramer measurement, and (c) showing peptide-specific CTL activity in the sorted tetramer-stanining CD8⁺T cells. Low frequency of HBV-specific CTLs was measured for both tetramers before lamivudine treatment. However, the number of CD8⁺ T cells specific for HBV core 18-27 increased significantly during lamivudine treatment. In contrast, relatively lower frequency of HBV pol 551-559 specific CD8⁺ T cells was persistently measured after lamivudine treatment. These results indicated that the lamivudine treatment could enhance HBV specific CTL responses.