Infection kinetics and impact of hepatitis B virus HBeAg negative strains on innate immunity gene expression in humanized mice

Abstract

The HBeAg/precore protein of the hepatitis B virus has been reported to counteract the innate immune response in vitro (Locarnini et al. 2005; Visvanathan et al. 2007; Lang et al. 2011). Nevertheless, the role of HBeAg in the HBV life cycle, in vivo, and its capacity to modulate the expression of antiviral innate signaling pathways remains unclear. Previous studies have described an immune modulatory effect of the HBeAg/precore protein in vitro, such an effect has not yet been demonstrated in vivo. The aim of this study was to elucidate the role of HBeAg/precore protein in HBV infection kinetics, replicative activity and expression of innate immunity genes in vivo in human liver chimeric uPA/SCID/beige mice. UPA/SCID/beige mice were infected with cell culture derived HBV genotype D wild type or its corresponding G1896A precore mutation variant lacking HBeAg expression. Viral titers were evaluated over the course of 12 weeks. Intrahepatic viral parameters as well as transcription levels of innate immune response related genes were determined after 12 weeks of infection. In addition, mice were treated with the TLR1/TLR2 agonist Pam3Cys to evaluate the impact of the HBeAg/precore protein on TLR signaling. Infection kinetics did not differ substantially, although we detected significantly lower amounts of pgRNA/cccDNA/PHH, suggesting higher packaging capacities of the G1896A mutant. In line with previous findings, induction of innate immune response was weak in infected hepatocytes regardless of HBeAg status. Surprisingly the precore protein did not contribute to disrupt infection recognition or transcription of innate immunity related genes in HBV-infected primary human hepatocytes in human liver chimeric uPA/SCID/beige mice. Stimulation of the TLR2 pathway also had a weak impact on PHHs and, consequently, did not affect HBV activity HBV-infected PHHs in immune deficient human liver chimeric mice.