AIM: To define the potential role of programmed death-1/programmed death-ligand (PD-1/PD-L) pathway in different hepatitis B virus (HBV) infection disease status; we examined the expression of PD-1 on antigen specific CD8+ T cells in peripheral blood of patients with chronic hepatitis B (CHB) and acute exacerbation of hepatitis B (AEHB) infection. METHODS: The PD-1 level on CD8+ T lymphocytes and the number of HBV specifi c CD8+ T lymphocytes in patients and healthy controls (HCs) were analyzed by staining with pentameric peptide-human leukocyte antigen2 (HLA2) complexes combined with flow cytometry. Real-time quantitative polymerase chain reaction (PCR) was used to measure the serum HBV-DNA levels. RESULTS: The level of PD-1 expression on total CD8+ T cells in CHB patients (13.86% ± 3.38%) was significantly higher than that in AEHB patients (6.80%± 2.19%, P < 0.01) and healthy individuals (4.63% ± 1.23%, P < 0.01). Compared to AEHB patients (0.81% ± 0.73%), lower frequency of HBV-specific CD8+ T cells was detected in chronic hepatitis B patients (0.37% ± 0.43%, P < 0.05). There was an inverse correlation between the strength of HBV-specific CD8+ T-cell response and the level of PD-1 expression. Besides, there was a significant positive correlation between HBV viral load and the percentage of PD-1 expression on CD8+ T cells in CHB and AEHB subjects (R = 0.541, P < 0.01). However, PD-1 expression was not associated with disease flare-ups as indicated by alanine aminotransferase (ALT) levels (R = 0.066, P > 0.05). CONCLUSION: Our results confirm previous reports that HBV specific CD8+ T-cell response in the peripheral blood is more intense in patients with AEHB than in chronic hepatitis B with persistent viral infection. Moreover, there is a negative correlation between the level of PD-1 and the intensity of virus specific CD8+T cell response. AIM: To define the potential role of programmed death-1 / programmed death-ligand (PD-1 / PD-L) pathway in different hepatitis B virus (HBV) infection disease status; we examined the expression of PD- METHODS: The PD-1 level on CD8 + T lymphocytes and the number of HBV specifi c CD8 + T lymphocytes in patients and real controls (HCs) were analyzed by staining with pentameric peptide-human leukocyte antigen2 (HLA2) complexes combined with flow cytometry. Real-time quantitative polymerase chain reaction (PCR) was used to measure the serum HBV-DNA levels. of PD-1 expression on total CD8 + T cells in CHB patients (13.86% ± 3.38%) were significantly higher than those in AEHB patients (6.80% ± 2.19%, P <0.01) <0.01). Compared to AEHB patients (0.81% ± 0.73%), lower frequency of HBV- The specific CD8 + T cells were detected in chronic hepatitis B patients (0.37% ± 0.43%, P <0.05). , there was a significant positive correlation between HBV viral load and the percentage of PD-1 expression on CD8 + T cells in CHB and AEHB subjects (R = 0.541, P <0.01). However, PD-1 expression was not associated with disease flare -ups as indicated by alanine aminotransferase (ALT) levels (R = 0.066, P> 0.05). CONCLUSION: Our results confirm previous reports that HBV specific CD8 + T-cell response in the peripheral blood is more intense in patients with AEHB than in chronic there is a negative correlation between the level of PD-1 and the intensity of virus specific CD8 + T cell response.