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Summary. Previous clinical studies have demonstrated an association between the hepatitis B e antigen and Toll-like receptor (TLR) expression and signalling. Therefore, the aim of this study was to develop an in vitro assay to measure the effect of hepatitis B virus proteins, including the precore protein, on signalling mediated by members of the Toll-like/interleukin 1 (TIR) superfamily, by measuring NF-κB promoter activity. The basal level of NF-κB reporter activity was measured in three hepatocyte cell lines (Huh7, HepG2 and PH5CH8) and one kidney cell line (HEK293) using a luciferase assay. All cell lines were virtually refractory to stimulation with lipopolysaccharide; however, PH5CH8 cells had a robust activation of NF-κB in response to IL-1β stimulation, with ∼40-fold higher activation than the unstimulated control, a higher degree of activation than that observed in either Huh7 and HepG2, or HEK293 and HEK293-TLR2 cells. In PH5CH8 cells transfected with pCI expression constructs and stimulated with IL-1β, we showed that the precursor form of the precore protein, p25, inhibits NF-κB activation by up to 30% and the cytosolic form, p22, inhibits NF-κB activation by 70%. The core protein, p21, which shares significant homology with the precore protein except for a 10-amino acid extension at the N-terminus, had no effect on NF-κB activation. We hypothesize that the inhibition of IL-1β-mediated NF-κB activation by the precore protein may be a mechanism that allows the virus to persist, suggesting a role for the pool of precore protein that remains intracellular.

Summary. Hepatitis B virus (HBV) infection is a major cause of liver-related morbidity and mortality. Toll-like receptors (TLRs) have recently been recognized to play an important role in the pathogenesis of chronic hepatitis B (CH-B). Furthermore, manipulation of TLR signalling pathways shows potential as an antiviral therapeutic strategy. Whether hepatocytes themselves possess intact TLR signalling pathways remains controversial. It is critical that cell culture models be developed to allow investigation of the interaction between HBV and the TLR signalling pathways. We have screened three hepatocyte cell lines for the integrity of pro-inflammatory responses and antiviral cytokines following stimulation with interleukin-1 (IL-1) and different TLR ligands. We observed that Huh-7, HepG2 and PH5CH8 cells selectively responded to IL-1 and TLR2 ligands, leading to the activation of NF-κB. In addition, the PH5CH8 cell lines were able to induce type 1 interferon (IFN) via both TLR3 and RIG-I following stimulation with poly I:C, HepG2 cells mounted an IFN response via RIG-I only, whereas Huh-7 cells were unresponsive. We conclude that the hepatocyte cell lines investigated display a repertoire of TLR signalling, albeit limited, suggesting that hepatocytes may themselves play an active role in innate immune responses to viruses such as HBV. Furthermore, particular hepatoma cell lines are suitable for investigating the interaction between HBV and hepatocyte-expressed pattern recognition receptors.

Patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB) have suppressed TLR2 expression, function and cytokine production. The aim of this study was to explore the importance of hepatitis B virus (HBV) genotype in innate immune responses and investigate whether Toll-like receptor (TLR) expression/function has potential roles as predictive biomarkers of successful therapy with pegylated interferon (Peg-IFN) therapy of HBeAg seroconversion in HBeAg-positive patients. We showed that as early as 4 weeks after initiation of Peg-IFN, future HBeAg seroconverters had significantly elevated levels of TLR2 expression on monocytes. TLR2-associated IL-6 production at baseline and week 4 of therapy and TLR4 IL-6 production at week 4 were also markedly elevated in HBeAg seroconverters. HBV genotype also influenced treatment response, with genotypes A and B more likely to seroconvert than D. We were able to demonstrate that these differences were due in part to the interaction of the specific HBeAg proteins with TLR pathway adaptor molecules, and these interactions were genotype dependent. HBeAg-mediated modulation of TLR signalling was also observed in Huh7 cells, following stimulation with Pam3Cys. Importantly, the addition of IFN-α to TLR2-stimulated cells cotransfected with an HBeAg expression plasmid reversed HBeAg-mediated suppression of hepatocytes. These findings demonstrate that patients with an activated inflammatory response are much more likely to respond to IFN therapy, with TLR responses showing promise as potential biomarkers of HBeAg seroconversion in this setting. Furthermore, our findings suggest there is differential genotype-specific HBeAg suppression of innate signalling pathways which may account for some of the clinical differences observed across the CHB spectrum.

SUMMARY The impact of mutations in the precore and basal core promoter (BCP) regions of the hepatitis B virus on the course of chronic liver disease is not well established. We sought to examine the relationship of these characteristics to the clinical expression of liver disease in patients infected with genotype D chronic hepatitis B (CHB). BCP and precore mutations in 110 patients with genotype D1 CHB were determined and correlated with clinical phenotype. Of 110 patients, 95 (86.5%) were HBeAg-negative. Compared with HBeAg-positive subjects, HBeAg-negative patients were over a decade older and had lower viral loads (3.70 +/- 0.98 vs 5.77 +/- 0.69 log copies/ml, P < 0.001). The double mutation A1762T-G1764A was more prevalent in patients with advanced liver disease (AdLD) and was associated with higher alanine aminotransferase and viral load. After adjusting for age, there was a more than fourfold increase in the risk of AdLD with this mutation (OR = 4.4; 95% CI: 1.13-16.92, P < 0.03). Conversely, the G1757A substitution was associated with protection, being 90% less frequent among patients with AdLD (P = 0.001). The results indicate that in genotype D CHB, the presence of the A1762T-G1764A mutation was associated with more aggressive liver disease while the G1757A substitution was associated with protection from advanced disease.