CORE MUTATIONS IN THE HBEAG-NEGATIVE STAGE ARE KEY DETERMINANTS OF HEPATITIS B VIRUS REPLICATION

Introduction and Objectives

The natural history of chronic HBV infection is characterized by distinct stages resulting from virus-host interactions. In this context, a late and pivotal event is HBeAg seroconversion, marked by the abrogation of HBeAg expression, a significant reduction in viral load, and the accumulation of mutations throughout the genome. While HBeAg abrogation is associated with mutations in the BCP and preCore regions, these mutations do not, per se, account for the observed reduction in viral load. Our aim was to unravel, at the molecular level, the drivers involved in the HBV replication rate.

Materials and Methods

Full-lenght HBV genome obtained from plasma samples of one HBeAg-positive patient and three HBeAg-negative patients was extracted, amplified and cloned. The replicative capacity and HBsAg antigen expresion of these clones and the chimeras obtained through core gene exchanges was evaluated in vitro.

Results

The incorporation of the wild-type (WT) core protein into HBeAg-negative genomes restored all viral replication intermediates (cccDNA, pgRNA, rcDNA, and capsid-associated DNA) to levels comparable to those of the WT virus and vice versa (Figure 1). Furthermore, a regulatory role of mutations in the core protein was observed in the modulation of HBsAg expression and secretion (Figure 2).

Conclusions

HBV viral load is a critical factor in the progression of chronic hepatitis B and its associated adverse outcomes. Mutations identified subsequent to HBeAg seroconversion are frequently found within the core region, and these mutations demonstrate a strong association with both HBV-DNA replication capacity and HBsAg expression levels.