Impact of Early Viral Kinetics on T-Cell Reactivity during Antiviral Therapy in Chronic Hepatitis B

Background The patterns of hepatitis B viral dynamics during different antiviral therapies and the associated changes in HBV-specific T-cell reactivity are not well defined. Methods We investigated the impact of early viral load decline on virus-specific T-cell reactivity in 30 hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B randomized to monotherapy with adefovir dipivoxil (ADV) or in combination with emtricitabine (ADV/FTC). Viral kinetics were analysed by mathematical modelling. T-cell reactivity to HBV core and/or surface antigens and natural killer T cell frequency were tested longitudinally, baseline to week 48, using EliSPOT assays and/or flow cytometry. Results Mathematical modelling of early HBV kinetics identified two subsets of patients: 11 fast responders (undetectable viraemia by week 12; eight on ADV/FTC three on ADV) and 19 slow responders who remained viremic (six on ADV/FTC 13 on ADV). The rate of infected hepatocyte loss was higher in fast than in slow responders ( P=0.0007), and correlated inversely with pre-treatment levels of intrahepatic covalently closed circular HBV DNA. The frequency of HBV core-specific CD4 + T-cells increased significantly only in fast responders, peaking between week 16 and 24, while the HBV surface-specific CD4 + T-cells increased in both subsets. These changes in CD4 + T-cell reactivity were transient however, and no increase in HBV-specific CD8 + T-cells was observed. By week 48, HBeAg seroconversion occurred only in 3/30 (10%) patients. Conclusions Early viraemia clearance facilitates recovery of virus-specific CD4 + T-cell reactivity, but appears insufficient to establish clinically relevant antiviral immunity.