Immunoregulation And Effect Of Anti-HBc In Chronic HBV Infection

Background and AimsChronic HBV infected(CHB)patients need long-term antiviral therapy,mainly due to the dissatisfied effect of antiviral drugs and the compromised immune systems of patients.Previous studies had found that baseline HBV DNA load,quantification of HBsAg and HBeAg were good predictors related to the outcome of interferons(IFNs)and nucleos(t)ide analogues(NAs)therapy,but they were indicators of viral load.Recently,many researchers had found that the baseline hepatitis B core antibody(Anti-HBc)level could predict the efficacy of IFNs and NAs therapy.Anti-HBc is the specific antibody against HBcAg.The elevation of Anti-HBc in patients with chronic HBV infection and its relationship with HBcAg expression have not been clarified.And it is unknown whether anti-HBc is only a biomarker reflected anti-HBV immune response or it also plays a role in controlling HBV.Therefore,we aimed to discover the subtypes and linear epitopes of Anti-HBc.Then the correlations between Anti-HBc and HBV-specific T cells and B cells were studied in vitro and in mouse model.Finally the direct effects of Anti-HBc in suppressing HBV replication were explored in vitro.MethodsFirstly,114 treatment-naive CHB patients,62 patients with liver biopsy,41 patients treated with telbivudine,6 patients with previous HBV infection,and 8 healthy donors were enrolled.HBV mouse model was established with rAAV8-HBV1.3 by tail vein injection and acetaminophen(APAP)was used to induce hepatitis in mice.Quantitative levels of Anti-HBc and intrahepatic HBcAg were detected by ELISA and immunohistochemical staining.GEO database(GSE65359)was analyzed using GE02R and differentially expressed genes between CHB patients in different phases were shown.Then,the phenotype and function of lymphocytes in peripheral blood,liver and spleen were tested by flow cytometry.Areas under the receiver operator characteristic curve(AUROC)were calculated for analyzing the predictive value of Anti-HBc in telbivudine-treated cohort patients.Results1.Characteristics of Anti-HBc in CHB patients during different phases of infection:1.1 Quantitative levels of Anti-HBc were high in CHB patients.And higher levels of Anti-HBc were found in hepatitis patients compared to inactive carriers;1.2 In hepatitis patients,IgM and IgG1 Anti-HBc were significantly increased;1.3 Multiple linear epitopes of Anti-HBc were detected in hepatitis patients.2.Increased levels of HBcAg released from liver is the main cause of serum Anti-HBc elevation:2.1 Intrahepatic HBcAg tended to be expressed from nucleus to cytoplasm during hepatitis activity.Meantime,serum Anti-HBc level were significantly increased in patients with cytoplasmic expression of HBcAg.In addition,strong correlations were found between intrahepatic HBcAg expressions and levels of Anti-HBc.2.2 In HBV mouse model bearing rAAV8-HBV1.35 serum ALT and HBCrAg were significantly increased at day 1 after APAP injection,while Anti-HBc levels peaked at day 4.3.Serum Anti-HBc levels mirrored frequencies and functions of HBV-specific B cells and CD8+ T cells:3.1 Serum Anti-HBc levels were correlated with frequencies of HBcAg-specific B cells,which could strongly present HBcAg to T cells and promote T cells proliferation.3.2 Serum Anti-HBc levels were correlated with frequencies of effector CD8+ T cells and HBV core-specific CD8+T cell;4.Anti-HBc is a good predictor for anti-viral threapy:4.1 Levels of IgG1 and IgG3 Anti-HBc exhibited higher AUROC in telbivudine-treated patients than levels of total Anti-HBc in predicting virological response in week 52 and ALT normalization in week 24.4.2 Anti-HBc directly inhibit the secretion of HBsAg and HBeAg in HepG2.2.15 cells,and mediated the activation of complement system to lyse HepG2.2.15 cells.ConclusionsLevels of Anti-HBc especially IgM and IgG1 subtypes were significantly increased and multiple linear epitopes of Anti-HBc were observed in hepatitis patients with chronic HBV infection.Furthermore,HBcAg released from damaged hepatocytes resulted in boost of Anti-HBc.T cells and B cells were strongly stimulated by HBcAg,so Anti-HBc level refeccted anti-HBV immune response,which was one of the reason for its predictive value.Anti-HBc also directly suppressed HBV replication in vitro.Finally,we found that levels of IgGl and IgG3 Anti-HBc exhibited higher predictive value than levels of total Anti-HBc.