Long term nucleos(t)ide analogue therapy reduced the extent of HBV DNA integration in chronic hepatitis B patients

Abstract

Background: Integration of HBV DNA into host chromosomes is associated with the development of hepatocellular carcinoma (HCC) in chronic hepatitis B (CHB) patients. Current anti-viral therapeutic agents, in the form of nucleos(t)ide analogue (NUCs), suppress HBV replication and reduce HCC risk. We aimed to study the effect of long-term NUC treatment on the extent of HBV DNA integration in CHB patients. Methods: 28 CHB patients who had received NUC treatment were studied. All had paired liver biopsies collected before treatment (baseline) and one year after treatment. Five of them had a third liver biopsy at 10 years post treatment. HBV DNA integration was detected in the liver DNA using inverse PCR. The extent of HBV DNA integration was expressed as hepatocyte clone size. Results: Of the 28 patients (21 males and 7 females; 14 HBeAg-positive and 14 HBeAg-negative; mean age 40 years), 11 received lamivudine, 7 received telbivudine, and 10 received entecavir. At baseline, all had detectable HBV DNA integration (median hepatocyte clone size: 1.40×105). HBV DNA integration sites were found in all chromosomes except chromosome Y, with integration at chromosomes 1, 2, 6, 16 and 21 being more prevalent. There was no significant association between hepatocyte clone size and patients’ age. Baseline hepatocyte clone size in HBeAg-positive and HBeAg-negative patients were comparable. HBV DNA integration was detectable one year after treatment, with a median hepatocyte clone size decreased to 6.72 × 104 (P = 0.003 compared with baseline) and a mean reduction of 42.5%. Of the 5 patients with liver biopsy at year 10, 3 had undetectable HBV DNA integration. A trend of reduction in hepatocyte clone size in these 5 patients was seen during the course of NUC treatment (baseline vs. 1 year vs. 10 year = 4.54×104 vs. 2.62×104 vs. <1.00×102, P = 0.015). At years 1 and 10, intrahepatic HBV DNA reduced by 1.5 and 3.0 logs respectively, and cccDNA reduced by 0.7 and 2.6 logs respectively. There was no significant correlation between the reduction in clone size and that of intrahepatic HBV DNA and cccDNA. Conclusion: One-year NUC treatment significantly reduced the extent of HBV DNA integration, which was further reduced upon 10 years of treatment. This supports the notion that long term NUC treatment reduces HCC risk through the reduction of HBV DNA integration. Further studies on the cellular/virologic pathways and the degree of integration reduction among different treatment agents and patient subgroups are needed.