Programmed death 1 and programmed death ligand 1 expressions in patients with chronic hepatitis B.

BACKGROUND: The role of programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) in persistent HBV infection is controversial. Increasing PD-1 and PD-L1 expression has been found in hepatitis B patients during immune clearance phase, but not in HBV-tolerant patients. We investigated PD-1 and PD-L1 expression and inflammation in chronic hepatitis B. METHODS: Twenty patients with chronic hepatitis B participated in this study. Fifteen patients were in the immune clearance phase, and 5 were in the immune inactive phase. Circulating HBV-specific T cells were analyzed by flow cytometric detection of major histocompatibility complex (MHC) class I peptide complexes, known as pentamers. Intra-hepatic PD-1 and PD-L1 expressions were analyzed by immunostaining. RESULTS: The frequency of pentamers, including core 18-27 (1.88%+/-0.36%), env 335-343 (1.85%+/-0.37%), and pol 575-583 (1.56%+/-0.29%) was 8.30-, 7.71- and 8.48-fold greater during immune clearance phase than those during the immune inactive phase. In addition, more than 70% of circulating pentamers were PD-1 positive. During immune clearance phase, the numbers of intra-hepatic PD-1 and PD-L1 positive cells were 108+/-23/HPF and 97+/-20/HPF respectively, in contrast, there was a paucity of PD-1 and PD-L1 positive cells in the immune inactive phase. The numbers of intra-hepatic PD-1 and PD-L1 positive cells were positively correlated with serum alanine aminotransferase and the number of intra-hepatic CD8+ T cells. Immunofluorescence showed that almost all of the intra-hepatic CD8+ T cells were PD-1 and CCR6 positive. These cells aggregated around macrophage inflammatory protein-3 alpha (MIP3alpha) positive cells and mixed with PD-L1 positive cells. CONCLUSIONS: PD-1 and PD-L1 expressions were significantly correlated with inflammation. CCR6 and PD-1 co-expressed in the same cells; these cells were increased both in circulation and the inflamed liver and aggregated around MIP3alpha positive cells. The mixture of CCR6 and PD-1, MIP3alpha and PD-L1 positive cells created immune response compartments which played an important role in specific immune response in HBV immune clearance.

Study of human B7 homolog 1 expression in patients with hepatitis B virus infection.

AIM: To further investigate the role of human B7 homolog 1 (B7-H1) in the mechanism of persistent hepatitis B virus (HBV) infection. METHODS: Peripheral and intra-hepatic B7-H1 expression were compared by flow cytometry and immunochemical staining between two 2 distinct groups, one being chronic HBV tolerance patients (CHB-T) and the other being acute hepatitis B patients (AHB). B7-H1 mRNA expression level was also compared by real time polymerase chain reaction between CHB-T and AHB patients. The location of intra-hepatic B7-H1 and CD40 expression were analyzed by immunofluorescence. The levels of B7-H1 and CD40 expression on cultured myeloid dendritic cells (mDCs) with or without hepatitis B surface antigen (HBsAg) treatment were analyzed dynamically by flow cytometry. Intracellular interferon-γ (IFN-γ) staining and the stimulatory capacity of mDC of cultured mDC with or without HBsAg treatment were also compared by flow cytometry. RESULTS: Peripheral B7-H1 expression on mDCs was increased significantly in AHB compared to CHB-T patients (P < 0.05). In the liver tissues from CHB-T patients, B7-H1 positive cells were almost absent despite a persistently elevated serum HBsAg load. In contrast, there were indeed increased B7-H1-positive cells in situ in the liver tissue from AHB. In vitro analysis showed the parallel upregulation of B7-H1 and CD40 on CD11c+ mDCs after the onset of stimulation. Addition of recombinant hepatitis B surface antigen (rHBsAg) significantly decreased CD40 expression (P < 0.05 at 16 h, 20 h and 24 h time points). B7-H1 expression was also inhibited by rHBsAg, and the inhibition rate of CD40 was greater than that of B7-H1. This preferential inhibition of CD40 expression on mDCs by rHBsAg resulted in the dysfunction of mDCs and T cells in the mixed leucocyte reaction (MLR) system. With rHBsAg pretreatment, in a carboxyfluorescein diacetate succinimidyl ester (CFSE) labeled MLR system at a ratio of 1:5 responder cell-stimulator cell (R/S), the CFSE(dim) percentage of T cells decreased from 85.1% to 25.4% and decreased from 30.3% to 12.0% at 1:10 R/S. IFN-γ production by CD8+ T cells, in the MLR system, was reduced significantly by HBsAg pretreatment. At ratios of 1:5 R/S, the percentage of IFN-γ and CD8 dual positive T cells decreased from 55.2% ± 5.3% to 15.1% ± 3.1% (P < 0.001), and decreased from 35.0% ± 5.1% to 7.3% ± 2.7% at ratios of 1:10 R/S (P < 0.001). CONCLUSION: B7-H1 is not a signature of immune dysfunction, but an inflammation marker. HBsAg regulate immune response by tipping the balance between B7-H1 and CD40.