Programmed death-1 expression is associated with the disease status in hepatitis B virus infection

AIM： TO define the potential role of programmed death-i/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 （CriB） and acute exacerbation of hepatitis B （AEHB） infection. METHODS： The PD-1 level on CD8＋ T lymphocytes and the number of HBV specific 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 CriB 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 wlth 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.