HBV DNA Integration and Clonal Hepatocyte Expansion in Chronic Hepatitis B Patients Considered Immune Tolerant

Abstract

Background & Aims: Chronic hepatitis B virus (HBV) infection is characterized clinically by progression through disease phases. The first, labeled immune tolerant (IT), is perceived to lack disease activity. Here, we examined HBV-DNA integration, clonal hepatocyte expansion, HBV antigen expression and HBV-specific immunity in patients considered IT to assess whether this designation is appropriate, or if pathological changes may be present. Methods: HBV-DNA integration, clonal hepatocyte expansion, HBsAg and HBcAg expression were studied in liver tissue from CHB patients, (age 14–39 years; median=24.5). These included 9 HBeAg(+) IT patients. Ten HBeAg(+) and 7 HBeAg(−) age-matched patients with active disease served as controls. HBV-specific T cells were quantified in paired peripheral blood lymphocytes. Results: HBV antigen expression differed between the patient groups. However, unexpectedly high numbers of HBV-DNA integrations, randomly distributed across most chromosomes, were detectable in all patient groups. Patients considered IT also displayed significant clonal hepatocyte expansion, potentially in response to active HBV-specific T cell immunity. HBV-specific T cell responses were also confirmed in the periphery of these patients. Conclusions: A high level of HBV DNA integration and clonal hepatocyte expansion in patients considered IT suggests that events in hepatocarcinogenesis are underway even in the early stages of CHB. The concept that the IT phase is devoid of markers of disease progression and is immunologically inert is unsupported; instead, we propose that high replicative low inflammatory (HRLI) CHB more accurately reflects this early disease phase. The timing of therapeutic intervention to minimize further genetic damage to the hepatocyte population should be reconsidered.