Tropifexor plus cenicriviroc combination versus monotherapy in nonalcoholic steatohepatitis: Results from the phase 2b TANDEM study

BACKGROUND AND AIMS

With distinct mechanisms of action, the combination of tropifexor (TXR) and cenicriviroc (CVC) may provide an effective treatment for NASH. This randomized, multicenter, double-blind, phase 2b study assessed the safety and efficacy of TXR and CVC combination, compared with respective monotherapies.

APPROACH AND RESULTS

Patients (N = 193) were randomized 1:1:1:1 to once-daily TXR 140 μg (TXR 140 ), CVC 150 mg (CVC), TXR 140 μg + CVC 150 mg (TXR 140 + CVC), or TXR 90 μg + CVC 150 mg (TXR 90 + CVC) for 48 weeks. The primary and secondary end points were safety and histological improvement, respectively. Rates of adverse events (AEs) were similar across treatment groups. Pruritus was the most frequently experienced AE, with highest incidence in the TXR 140 group (40.0%). In TXR and combination groups, alanine aminotransferase (ALT) decreased from baseline to 48 weeks (geometric mean change: -21%, TXR 140 ; -16%, TXR 140 + CVC; -13%, TXR 90 + CVC; and +17%, CVC). Reductions in body weight observed at week 24 (mean changes from baseline: TXR 140 , -2.5 kg; TXR 140 + CVC, -1.7 kg; TXR 90 + CVC, -1.0 kg; and CVC, -0.1 kg) were sustained to week 48. At least 1-point improvement in fibrosis stage/steatohepatitis resolution without worsening of fibrosis was observed in 32.3%/25.8%, 31.6%/15.8%, 29.7%/13.5%, and 32.5%/22.5% of patients in the TXR 140 , CVC, TXR 140 + CVC, and TXR 90 + CVC groups, respectively.

CONCLUSIONS

The safety profile of TXR + CVC combination was similar to respective monotherapies, with no new signals. TXR monotherapy showed sustained ALT and body weight decreases. No substantial incremental efficacy was observed with TXR + CVC combination on ALT, body weight, or in histological end points compared with monotherapy.

Tropifexor for nonalcoholic steatohepatitis: an adaptive, randomized, placebo-controlled phase 2a/b trial

The multimodal activities of farnesoid X receptor (FXR) agonists make this class an attractive option to treat nonalcoholic steatohepatitis. The safety and efficacy of tropifexor, an FXR agonist, in a randomized, multicenter, double-blind, three-part adaptive design, phase 2 study, in patients with nonalcoholic steatohepatitis were therefore assessed. In Parts A + B, 198 patients were randomized to receive tropifexor (10-90 μg) or placebo for 12 weeks. In Part C, 152 patients were randomized to receive tropifexor 140 µg, tropifexor 200 µg or placebo (1:1:1) for 48 weeks. The primary endpoints were safety and tolerability to end-of-study, and dose response on alanine aminotransferase (ALT), aspartate aminotransferase (AST) and hepatic fat fraction (HFF) at week 12. Pruritus was the most common adverse event in all groups, with a higher frequency in the 140- and 200-µg tropifexor groups. Decreases from baseline in ALT and HFF were greater with tropifexor versus placebo at week 12, with a relative decrease in least squares mean from baseline observed with all tropifexor doses for ALT (tropifexor 10-90-μg dose groups ranged from -10.7 to -16.5 U l-1 versus placebo (-7.8 U l-1) and tropifexor 140- and 200-μg groups were -18.0 U l-1 and -23.0 U l-1, respectively, versus placebo (-8.3 U l-1)) and % HFF (tropifexor 10-90-μg dose groups ranged from -7.48% to -15.04% versus placebo (-6.19%) and tropifexor 140- and 200-μg groups were -19.07% and -39.41%, respectively, versus placebo (-10.77%)). Decreases in ALT and HFF were sustained up to week 48; however, similar trends in AST with tropifexor at week 12 were not observed. As with other FXR agonists, dose-related pruritus was frequently observed. Clinicaltrials.gov registration: NCT02855164.

Digital pathology with artificial intelligence analyses provides greater insights into treatment-induced fibrosis regression in NASH

BACKGROUND & AIMS

Liver fibrosis is a key prognostic determinant for clinical outcomes in non-alcoholic steatohepatitis (NASH). Current scoring systems have limitations, especially in assessing fibrosis regression. Second harmonic generation/two-photon excitation fluorescence (SHG/TPEF) microscopy with artificial intelligence analyses provides standardized evaluation of NASH features, especially liver fibrosis and collagen fiber quantitation on a continuous scale. This approach was applied to gain in-depth understanding of fibrosis dynamics after treatment with tropifexor (TXR), a non-bile acid farnesoid X receptor agonist in patients participating in the FLIGHT-FXR study (NCT02855164).

METHOD

Unstained sections from 198 liver biopsies (paired: baseline and end-of-treatment) from 99 patients with NASH (fibrosis stage F2 or F3) who received placebo (n = 34), TXR 140 μg (n = 37), or TXR 200 μg (n = 28) for 48 weeks were examined. Liver fibrosis (qFibrosis®), hepatic fat (qSteatosis®), and ballooned hepatocytes (qBallooning®) were quantitated using SHG/TPEF microscopy. Changes in septa morphology, collagen fiber parameters, and zonal distribution within liver lobules were also quantitatively assessed.

RESULTS

Digital analyses revealed treatment-associated reductions in overall liver fibrosis (qFibrosis®), unlike conventional microscopy, as well as marked regression in perisinusoidal fibrosis in patients who had either F2 or F3 fibrosis at baseline. Concomitant zonal quantitation of fibrosis and steatosis revealed that patients with greater qSteatosis reduction also have the greatest reduction in perisinusoidal fibrosis. Regressive changes in septa morphology and reduction in septa parameters were observed almost exclusively in F3 patients, who were adjudged as 'unchanged' with conventional scoring.

CONCLUSION

Fibrosis regression following hepatic fat reduction occurs initially in the perisinusoidal regions, around areas of steatosis reduction. Digital pathology provides new insights into treatment-induced fibrosis regression in NASH, which are not captured by current staging systems.

LAY SUMMARY

The degree of liver fibrosis (tissue scarring) in non-alcoholic steatohepatitis (NASH) is the main predictor of negative clinical outcomes. Accurate assessment of the quantity and architecture of liver fibrosis is fundamental for patient enrolment in NASH clinical trials and for determining treatment efficacy. Using digital microscopy with artificial intelligence analyses, the present study demonstrates that this novel approach has greater sensitivity in demonstrating treatment-induced reversal of fibrosis in the liver than current systems. Furthermore, additional details are obtained regarding the pathogenesis of NASH disease and the effects of therapy.

Randomised clinical trial: alisporivir combined with peginterferon and ribavirin in treatment-naïve patients with chronic HCV genotype 1 infection (ESSENTIAL II)

BACKGROUND

Alisporivir (ALV) is an oral, host-targeting agent with pangenotypic anti-hepatitis C virus (HCV) activity and a high barrier to resistance.

AIM

To evaluate efficacy and safety of ALV plus peginterferon-α2a and ribavirin (PR) in treatment-naïve patients with chronic HCV genotype 1 infection.

METHODS

Double-blind, randomised, placebo-controlled, Phase 3 study evaluating ALV 600 mg once daily [response-guided therapy (RGT) for 24 or 48 weeks or 48 weeks fixed duration] or ALV 400 mg twice daily RGT with PR, compared to PR alone. Following a Food and Drug Administration partial clinical hold, ALV/placebo was discontinued and patients completed treatment with PR only. At that time, 87% of patients had received ≥12 weeks and 20% had received ≥24 weeks of ALV/PR triple therapy.

RESULTS

A total of 1081 patients were randomised (12% cirrhosis, 55% CT/TT IL28B). Addition of ALV to PR improved virological response in a dose-dependent fashion. Overall, sustained virological response (SVR12; primary endpoint) was 69% in all ALV groups vs. 53% in PR control. Highest SVR12 (90%) was achieved in patients treated with ALV 400 mg twice daily and PR for >24 weeks. Seven cases of pancreatitis were reported, with similar frequency between ALV/PR and PR control groups (0.6% vs. 0.8% respectively). Adverse events seen more frequently with ALV/PR than with PR alone were anaemia, thrombocytopenia, hyperbilirubinaemia and hypertension.

CONCLUSIONS

Alisporivir, especially the 400 mg twice daily regimen, increased efficacy of PR therapy in treatment-naïve patients with HCV genotype 1 infection. The mechanism of action and pangenotypic activity suggest that alisporivir could be useful in interferon-free combination regimens.

Alisporivir plus ribavirin, interferon free or in combination with pegylated interferon, for hepatitis C virus genotype 2 or 3 infection

Alisporivir is a cyclophilin inhibitor with pan-genotypic anti-hepatitis C virus (HCV) activity and a high barrier to viral resistance. The VITAL-1 study assessed alisporivir as interferon (IFN)-free therapy in treatment-naïve patients infected with HCV genotype 2 or 3. Three hundred forty patients without cirrhosis were randomized to: arm 1, alisporivir (ALV) 1,000 mg once-daily (QD); arm 2, ALV 600 mg QD and ribavirin (RBV); arm 3, ALV 800 mg QD and RBV; arm 4, ALV 600 mg QD and pegylated IFN (Peg-IFN); or arm 5, Peg-IFN and RBV. Patients receiving IFN-free ALV regimens who achieved rapid virological response (RVR) continued the same treatment throughout, whereas those with detectable HCV RNA at week 4 received ALV, RBV, and Peg-IFN from weeks 6 to 24. Overall, 300 patients received ALV-based regimens. In arm 1 to arm 4, the intent-to-treat rates of sustained virological response (SVR) 24 weeks after treatment (SVR24) were from 80% to 85%, compared with 58% (n = 23 of 40) with Peg-IFN/RBV. Per-protocol analysis showed higher SVR24 rates in patients who received ALV/RBV, IFN-free after RVR (92%; n = 56 of 61) than with ALV alone after RVR (72%; n = 13 of 18) or with Peg-IFN/RBV (70%; n = 23 of 33). Both RVRs and SVRs to ALV IFN-free regimens were numerically higher in genotype 3- than in genotype 2-infected patients. Viral breakthrough was infrequent (3%; n = 7 of 258). IFN-free ALV treatment showed markedly better safety/tolerability than IFN-containing regimens.

CONCLUSIONS

ALV plus RBV represents an effective IFN-free option for a proportion of patients with HCV genotype 2 or 3 infections, with high SVR rates for patients with early viral clearance. Further investigations of ALV in IFN-free combination regimens with direct-acting antiviral drugs deserve exploration in future trials.

Alisporivir inhibition of hepatocyte cyclophilins reduces HBV replication and hepatitis B surface antigen production

BACKGROUND & AIMS

Cyclophilins are host factors required for hepatitis C virus replication. Cyclophilin inhibitors such as alisporivir have shown strong anti-hepatitis C virus activity in vitro and in clinical studies. However, little is known about whether hepatocyte cyclophilins are involved in the hepatitis B virus (HBV) life cycle. We investigated the effects of 2 cyclophilin inhibitors (alisporivir and NIM811) on HBV replication and hepatitis B surface antigen (HBsAg) production in cell lines.

METHODS

Liver-derived cell lines producing full-length HBV and HBsAg particles, owing to stable (HepG2215) or transient (HuH-7) transfection, or infected with HBV (HepaRG cells; Invitrogen [Carlsbad, CA]), were incubated with alisporivir or NIM811 alone, or alisporivir in combination with a direct antiviral (telbivudine). The roles of individual cyclophilins in drug response was evaluated by small interfering RNA knockdown of cyclophilin (CYP)A, CYPC, or CYPD in HepG2215 cells, or CYPA knockdown in HuH-7 cells. The kinetics of antiviral activity were assessed based on levels of HBV DNA and HBsAg and Southern blot analysis.

RESULTS

In HepG2215, HuH-7, and HepaRG cells, alisporivir reduced intracellular and secreted HBV DNA, in a dose-dependent manner. Knockdown of CYPA, CYPC, or CYPD (reduced by 80%) significantly reduced levels of HBV DNA and secreted HBsAg. Knockdown of CYPA significantly reduced secretion of HBsAg, leading to accumulation of intracellular HBsAg; the addition of alisporivir greatly reduced levels of HBsAg in these cells. The combination of alisporivir and telbivudine had greater antiviral effects than those of telbivudine or alisporivir alone.

CONCLUSIONS

Alisporivir inhibition of cyclophilins in hepatocyte cell lines reduces replication of HBV DNA and HBsAg production and secretion. These effects are potentiated in combination with direct antiviral agents that target HBV-DNA polymerase.

Cyclophilin inhibition as potential therapy for liver diseases

The cyclophilins are a group of proteins with peptidyl-prolyl isomerase enzymatic activity, localised in different cellular compartments and involved in a variety of functions related to cell metabolism and energy homeostasis, having enhanced expression in inflammation or malignancy. Cyclophilin A (CypA), the most abundantly expressed cyclophilin, is present mainly in the cytoplasm and is a host factor involved in the life cycle of multiple viruses. The extracellular fractions of CypA and CypB are potent pro-inflammatory mediators. CypD, located in mitochondria, is a key regulator of mitochondrial permeability transition pores, and is critical for necrotic cell death. Cyclosporines are the prototype cyclophilin inhibitors. Cyclic peptides, which bind and inhibit cyclophilins without having immunosuppressive properties, have been generated by chemical modifications of cyclosporin A. In addition, cyclophilin inhibitors that are structurally different from cyclosporines have been synthesized. The involvement of cyclophilins in the pathogenesis of different liver diseases has been established using both in vitro and in vivo investigations, thus indicating that cyclophilin inhibition may be of therapeutic benefit. This review summarises the evidence for potential therapeutic applications of non-immunosuppressive cyclophilin inhibitors, alone or in combination with other agents, in virus-induced liver diseases like hepatitis C, B or Delta, liver inflammation and fibrosis, acetaminophen-induced liver toxicity and hepatocellular carcinoma.

Early Viral Kinetics with Telbivudine, Tenofovir or Combination of Both in Immunotolerant Patients with Hepatitis B e Antigen-Positive Chronic Hepatitis B

Introduction

Viral kinetics has proved useful in understanding antiviral potency, determining antiviral profiles and optimizing treatment strategy.

Methods

This was a randomized, open-label study comparing the viral kinetics in 46 hepatitis B e antigen-positive patients during 12-week treatment with telbivudine monotherapy, tenofovir monotherapy or the combination of telbivudine plus tenofovir. A standard biphasic mathematical model was used to compare hepatitis B virus (HBV) DNA decay parameters.

Results

Forty-six patients received telbivudine (n = 16), tenofovir (n = 14) or telbivudine plus tenofovir (n = 16). From baseline to Week 12, the mean (SD) reduction in HBV DNA levels was not significantly different between treatment groups: −3.9 (0.9) log₁₀ copies/mL in telbivudine group, −4.2 (0.7) log₁₀ copies/mL in tenofovir group, and −4.4 (1.0) log₁₀ copies/mL in combination group. No significant difference was observed among the three groups for viral clearance rate per day (0.97, 1.02, and 0.88, respectively) or for infected cell loss rate per day (0.04, 0.05, and 0.05, respectively). Antiviral efficiency in blocking viral production was similar in the monotherapy groups (median; 99.7% in telbivudine group and 99.4% in tenofovir group), but was slightly better and more homogeneous in the combination treatment group than in the monotherapy groups: mean (SD), 99.1% (0.8%) and 98.8% (1.6%), respectively (Wald–Wolfowitz test; P = 0.038). All treatments were well tolerated and no serious adverse event was reported during the study. Of the 46 patients in the safety population, 23 experienced adverse events. Most of the adverse events were not suspected to be related to the study drug by the investigators.

Conclusion

Monotherapy with telbivudine or tenofovir showed similar antiviral effectiveness in HBV DNA reduction and viral kinetics of HBV DNA decay. Efficiency in blocking viral production was slightly improved in the combination treatment group compared to the monotherapy groups.

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-014-0039-5) contains supplementary material, which is available to authorized users.

Truncated CXCL10 is associated with failure to achieve spontaneous clearance of acute hepatitis C infection

The pathogenesis of hepatitis C virus (HCV) infection is strongly influenced by the nature of the host's antiviral immunity. Counterintuitively, elevated serum concentrations of C-X-C chemokine 10 (CXCL10), a potent chemoattractant for antiviral T-cells and NK-cells, are associated with poor treatment outcomes in patients with chronic HCV. It has been reported that an N-terminal truncated form of CXCL10, generated by the protease dipeptidylpeptidase 4 (DPP4), can act as chemokine antagonist. We sought to investigate CXCL10 antagonism in the clinical outcome and evolution of acute HCV infection. We collected serial blood samples from 16 patients, at the clinical onset of acute HCV infection and at 12 standardized follow-up timepoints over the first year. Intact and truncated CXCL10 and DPP4 activity were quantified in all longitudinal samples. In addition, NK-cell frequency/phenotype, and HCV-specific T-cell responses were assessed. Subjects developing chronicity (n = 11) had higher concentrations of CXCL10 (P < 0.001), which was predominantly in a truncated form (P = 0.036) compared to patients who spontaneously resolved infection (n = 5). Truncated CXCL10 correlated with HCV-RNA (r = 0.40, P < 0.001) and DPP4 activity (r = 0.53, P < 0.001). Subjects who resolved infection had a higher frequency of HCV-specific interferon-gamma (IFNγ)-producing T-cells (P = 0.017) and predominance of cytotoxic NK-cells (P = 0.005) compared to patients who became chronic. Patients who became persistently infected had higher proportions of cytokine-producing NK-cells, which were correlated with concentrations of truncated CXCL10 (r = 0.92, P < 0.001).

CONCLUSION

This study provides the first evidence of chemokine antagonism during acute HCV infection. We suggest that the DPP4-CXCL10 axis inhibits antiviral innate and adaptive host immunity and favors establishment of viral persistence.

Identification of serum cytokine profiles associated with HBeAg seroconversion following antiviral treatment interruption

The major shortcoming of nucleos(t)ide analogue therapy for chronic hepatitis B (CHB) is the frequent requirement for indefinite therapy. Withdrawal of treatment can result in viral rebound with an alanine aminotransferase (ALT) flare leading to hepatic decompensation, while in others this can lead to hepatitis B e antigen (HBeAg) seroconversion. The aim of the study was to identify host immune profiles associated with these different outcomes. Eighteen HBeAg(+) patients, enrolled on a phase III trial with the nucleoside analogue adefovir dipivoxil, were followed for up to 128 weeks. For the first 48 weeks, all patients received continuous therapy. Subsequently, patients experienced cycles of treatment interruptions due to random drug/placebo misallocations. Host immune profiles were characterized by measuring a panel of serum cytokines before, during, and after each cycle of treatment withdrawal. Virus-specific T-cell responses were also determined at these time points in a subset of patients to elucidate the mechanisms utilized to control hepatitis B virus (HBV) replication post-treatment. Significantly, elevated levels of IFN-γ, IP-10, and IL-2 on-treatment were associated with HBeAg seroconversion after treatment withdrawal. In these patients, treatment interruption induced further increases in serum IFN-γ levels and marked increases in virus-specific T-cells producing IFN-γ, but minimal alterations in viremia and ALT. In HBeAg(+) patients with low on-treatment levels of serum IFN-γ, the interruption of therapy induced significant elevations in HBV-DNA, ALT, IP-10, and increases in virus-specific T-cells producing IL-10. Evaluating on-treatment serum cytokines in concert with virologic and clinical parameters may help to identify CHB patients who can successfully discontinue nucleos(t)ide analogue therapy.

Modeling viral kinetics and treatment outcome during alisporivir interferon-free treatment in hepatitis C virus genotype 2 and 3 patients

Alisporivir (ALV) is a cyclophilin inhibitor with pan-genotypic activity against hepatitis C virus (HCV). Here, we characterize the viral kinetics observed in 249 patients infected with HCV genotypes 2 or 3 and treated for 6 weeks with different doses of ALV with or without ribavirin (RBV). We use this model to predict the effects of treatment duration and different doses of ALV plus RBV on sustained virologic response (SVR). Continuous viral decline was observed in 214 (86%) patients that could be well described by the model. All doses led to a high level of antiviral effectiveness equal to 0.98, 0.96, and 0.90 in patients treated with 1,000, 800, and 600 mg of ALV once-daily, respectively. Patients that received RBV had a significantly faster rate of viral decline, which was attributed to an enhanced loss rate of infected cells, δ (mean δ = 0.35 d(-1) vs. 0.21 d(-1) in patients ± RBV, respectively; P = 0.0001). The remaining 35 patients (14%) had a suboptimal response with flat or increasing levels of HCV RNA after 1 week of treatment, which was associated with ALV monotherapy, high body weight, and low RBV levels in patients that received ALV plus RBV. Assuming full compliance and the same proportion of suboptimal responders, the model predicted 71% and 79% SVR after ALV 400 mg with RBV 400 mg twice-daily for 24 and 36 weeks, respectively. The model predicted that response-guided treatment could allow a reduction in mean treatment duration to 25.3 weeks and attain a 78.6% SVR rate.

CONCLUSION

ALV plus RBV may represent an effective IFN-free treatment that is predicted to achieve high SVR rates in patients with HCV genotype 2 or 3 infection.

Circulating chemokine (C-X-C Motif) receptor 5(+) CD4(+) T cells benefit hepatitis B e antigen seroconversion through IL-21 in patients with chronic hepatitis B virus infection

Given the clinical significance of hepatitis B e antigen (HBeAg) seroconversion in chronic hepatitis B virus (HBV) infection, it is critical to elucidate the mechanisms regulating this process. In the present study, we found that the frequency of circulating chemokine (C-X-C motif) receptor 5 (CXCR5)(+) CD4(+) T cells was higher in patients who had achieved HBeAg seroconversion in both cross-sectional (P < 0.001) and longitudinal (P = 0.009) studies. These cells were able to produce a significantly higher level of intracellular interleukin 21 (IL-21) after stimulation with HBV peptides in patients with telbivudine-induced HBeAg seroconversion (P = 0.007). Furthermore, sorted CXCR5(+) CD4(+) T cells from HBeAg seroconverters boosted a higher frequency of antibody against hepatitis B e antigen (anti-HBe)-secreting B cells in coculture assay (P = 0.011). Of note, the increase in frequency of anti-HBe-secreting B cells was abrogated by soluble recombinant IL-21 receptor-Fc chimera (P = 0.027), whereas exogenous recombinant IL-21 enhanced this effect (P = 0.043). Additionally, circulating CXCR5(+) CD4(+) T cells shared similar phenotypic markers, and were positively correlated in frequency with, splenic follicular T helper cells.

CONCLUSION

Circulating CXCR5(+) CD4(+) T cells, by producing IL-21, may have a significant role in facilitating HBeAg seroconversion in patients with chronic HBV infection.

Efficacy and safety of continuous 4-year telbivudine treatment in patients with chronic hepatitis B

In the phase-III GLOBE/015 studies, telbivudine demonstrated superior efficacy vs lamivudine during 2-year treatment in HBeAg-positive and HBeAg-negative chronic hepatitis B (CHB). After completion, 847 patients had an option to continue telbivudine treatment for further 2 years. A total of 596 (70%) of telbivudine-treated patients, who were serum HBV DNA positive or negative and without genotypic resistance to telbivudine at the end of the GLOBE/015 trials, were enrolled into a further 2-year extension study. A group of 502 patients completed 4 years of continuous telbivudine treatment and were included in the telbivudine per-protocol population. Amongst 293 HBeAg-positive patients, 76.2% had undetectable serum HBV DNA and 86.0% had normal serum ALT at the end of 4 years. Notably, the cumulative rate of HBeAg seroconversion was 53.2%. Amongst 209 HBeAg-negative patients, 86.4% had undetectable HBV DNA and 89.6% had normal serum ALT. In patients who had discontinued telbivudine treatment due to HBeAg seroconversion, the HBeAg response was durable in 82% of patients (median 111 weeks of off-treatment follow-up). The cumulative 4-year resistance rate was 10.6% for HBeAg-positive and 10.0% for HBeAg-negative patients. Most adverse events were mild or moderate in severity and transient. Renal function measured by estimated glomerular filtration rate (eGFR) increased by 14.9 mL/min/1.73 m(2) (16.6%) from baseline to 4 years (P < 0.0001). In conclusion, in HBeAg-positive and HBeAg-negative CHB patients without resistance after 2 years, two additional years of telbivudine treatment continued to provide effective viral suppression with a favourable safety profile. Moreover, telbivudine achieved 53% of HBeAg seroconversion in HBeAg-positive patients.

High serum IL-21 levels after 12 weeks of antiviral therapy predict HBeAg seroconversion in chronic hepatitis B

BACKGROUND & AIMS

Interleukin-21 (IL-21) stimulates T cell and B cell responses and plays a role in control of chronic viral infections. The role of IL-21 in chronic hepatitis B virus (HBV) infection is not understood.

METHODS

Serum IL-21 levels were measured by enzyme immunoassay in 75 HBeAg-positive chronic hepatitis B (CHB) patients undergoing telbivudine treatment. The findings were validated in 103 patients from a separate clinical trial of telbivudine. A complete response to telbivudine was defined as having both HBeAg seroconversion and serum HBV-DNA level <300 copies/ml by treatment week 52. The proportions of T-cells producing IL-21 and/or expressing programmed death 1 (PD-1) in peripheral blood mononuclear cells were assessed longitudinally during treatment by intracellular cytokine staining and flow cytometry.

RESULTS

Median serum IL-21 levels at treatment week 12 were significantly higher in patients who did achieve vs. patients who did not achieve a complete response in both the initial (128.4 vs. 69.2 pg/ml, p=0.003) and the validation (142.2 vs. 89.9 pg/ml, p=0.004) trials. Serum levels of IL-21 (p=0.005) or HBV-DNA (p=0.003) levels at treatment week 12 independently predicted HBeAg seroconversion in the first year of treatment. The decrease in PD-1 expression on CD4(+) and CD8(+) T cells during the first 12 weeks on telbivudine treatment was not correlated with changes in IL-21 concentrations.

CONCLUSIONS

Serum IL-21 levels may be a biomarker for HBeAg seroconversion, and may contribute to individualization of antiviral therapy in HBeAg-positive CHB. IL-21 may also have a role in immunotherapy for CHB.

Kinetics of hepatitis B surface antigen decline during 3 years of telbivudine treatment in hepatitis B e antigen-positive patients

The impact of prolonged direct antiviral therapy on hepatitis B surface antigen (HBsAg) levels in patients with chronic hepatitis B is poorly understood. We quantitatively assessed serum HBsAg levels during 3 years of telbivudine treatment, as well as their relationship with virologic and biochemical characteristics in 162 hepatitis B e antigen-positive patients who maintained undetectable serum hepatitis B virus (HBV) DNA long-term. Telbivudine treatment progressively reduced serum HBsAg levels (mean ± SD) from baseline (3.8 ± 0.6 log₁₀ IU/mL) to treatment week 24 (3.4 ± 0.7 log₁₀ IU/mL), treatment year 1 (3.3 ± 0.8 log₁₀ IU/mL), and treatment year 3 (3.0 ± 1.4 log₁₀ IU/mL) (P <0.0001). In this patient population, HBsAg loss was observed in nine (6%) of 162 patients through year 3. During the first year of treatment, three patterns of HBsAg decline were observed: rapid (≥ 1 log₁₀ IU/mL) in 32 patients, slow (0-1 log₁₀ IU/mL) in 74 patients, and steady levels in 56 patients. These findings were associated with different likelihoods of HBsAg loss during long-term telbivudine therapy. Eight of 32 patients with rapid HBsAg decline versus none of 56 patients with steady HBsAg levels achieved HBsAg loss at year 3 (P = 0.0024). HBV genotype was a significant determinant for HBsAg kinetics, with the fastest decline in genotype A patients. In patients with subsequent HBsAg loss, viral antigens were already undetectable in liver biopsy samples after 1 year of treatment. This was associated with markedly enhanced antiviral T cell reactivity.

CONCLUSION

In patients who have effective suppression of viral replication during telbivudine treatment, a rapid decline in serum HBsAg levels during the first year may identify those with a greater likelihood of achieving HBsAg clearance.

Novel mechanism of antibodies to hepatitis B virus in blocking viral particle release from cells

Antibodies are thought to exert antiviral activities by blocking viral entry into cells and/or accelerating viral clearance from circulation. In particular, antibodies to hepatitis B virus (HBV) surface antigen (HBsAg) confer protection, by binding circulating virus. Here, we used mathematical modeling to gain information about viral dynamics during and after single or multiple infusions of a combination of two human monoclonal anti-HBs (HepeX-B) antibodies in patients with chronic hepatitis B. The antibody HBV-17 recognizes a conformational epitope, whereas antibody HBV-19 recognizes a linear epitope on the HBsAg. The kinetic profiles of the decline of serum HBV DNA and HBsAg revealed partial blocking of virion release from infected cells as a new antiviral mechanism, in addition to acceleration of HBV clearance from the circulation. We then replicated this approach in vitro, using cells secreting HBsAg, and compared the prediction of the mathematical modeling obtained from the in vivo kinetics. In vitro, HepeX-B treatment of HBsAg-producing cells showed cellular uptake of antibodies, resulting in intracellular accumulation of viral particles. Blocking of HBsAg secretion also continued after HepeX-B was removed from the cell culture supernatants.

CONCLUSION

These results identify a novel antiviral mechanism of antibodies to HBsAg (anti-HBs) involving prolonged blocking of the HBV and HBsAg subviral particles release from infected cells. This may have implications in designing new therapies for patients with chronic HBV infection and may also be relevant in other viral infections.

Baseline characteristics and early on-treatment response predict the outcomes of 2 years of telbivudine treatment of chronic hepatitis B

BACKGROUND/AIMS

In the GLOBE trial, telbivudine treatment was identified as a significant, independent predictor of better outcomes at 2 years. We analyzed all telbivudine recipients in this trial to determine the predictors of optimal outcomes.

METHODS

The intent-to-treat population comprised 458 HBeAg-positive and 222 HBeAg-negative telbivudine-treated patients. Multivariate logistic regression analyses were employed to evaluate baseline and/or early on-treatment variables.

RESULTS

Baseline HBV DNA<9 log(10)copies/mL, or ALT levels > or = 2x above normal were strong pretreatment predictors for HBeAg-positive, but not for HBeAg-negative patients. However, non-detectable serum HBV DNA at treatment week 24 (TW24) was the strongest predictor for better outcomes for both groups. A combination of pretreatment characteristics plus TW24 response identified subgroups with the best outcomes: (1) HBeAg-positive patients with baseline HBV DNA<9 log(10)copies/mL, ALT > or = 2x above normal and non-detectable HBV DNA at TW24 achieved at 2 years: non-detectable HBV DNA in 89%, HBeAg seroconversion in 52%, telbivudine resistance in 1.8%; and (2) HBeAg-negative patients with baseline HBV DNA<7 log(10)copies/mL and non-detectable serum HBV DNA at TW24 achieved at 2 years: non-detectable HBV DNA in 91%, telbivudine resistance in 2.3%.

CONCLUSION

During telbivudine treatment, non-detectable serum HBV DNA at treatment week 24 is the strongest predictor for optimal outcomes at 2 years.

2-Year GLOBE trial results: telbivudine Is superior to lamivudine in patients with chronic hepatitis B

BACKGROUND & AIMS

The GLOBE trial has compared the efficacy and safety of telbivudine versus lamivudine treatment over 2 years in patients with chronic hepatitis B.

METHODS

Hepatitis B e antigen (HBeAg)-positive (n = 921) and HBeAg-negative (n = 446) patients received telbivudine or lamivudine once daily for 104 weeks. The primary outcome, assessed in the intent-to-treat population, was therapeutic response (hepatitis B virus DNA <5 log(10) copies/mL and either HBeAg loss or normalization of alanine aminotransferase [ALT] level).

RESULTS

The therapeutic response to telbivudine was superior to that of lamivudine in HBeAg-positive (63% vs 48%; P < .001) and HBeAg-negative (78% vs 66%; P = .007) patients. HBeAg-positive patients given telbivudine also had better outcomes compared with lamivudine in terms of nondetectable viremia (< 300 copies/mL) at 55.6% versus 38.5% (P < .001), HBeAg loss at 35.2% versus 29.2% (P = .056), and viral resistance at 25.1% versus 39.5% (P < .001). Hepatitis B e antigen seroconversion was 29.6% versus 24.7% (P = .095) in all patients and 36% versus 27% (P = .022) in patients with baseline ALT level > or = 2 times normal. Telbivudine-treated HBeAg-negative patients showed higher rates of nondetectable viremia compared with lamivudine at 82.0% versus 56.7% (P < .001) and less resistance at 10.8% versus 25.9% (P < .001). Adverse events occurred with similar frequency, whereas grade 3/4 increases in creatine kinase levels were more common in patients given telbivudine (12.9% vs 4.1%, P < .001). Multivariate logistic regression analyses identified telbivudine treatment, among other variables, as an independent predictor of better week 104 outcomes.

CONCLUSIONS

Telbivudine is superior to lamivudine in treating patients with chronic hepatitis B over a 2-year period.

Hepatitis C virus (HCV)--specific T cell responses in injection drug users with apparent resistance to HCV infection

BACKGROUND

Injection drug users (IDUs) are at risk of acquiring hepatitis C virus (HCV) infection. We have identified a cohort of long-term IDUs who remain uninfected by HCV despite high-risk behavior. We have categorized these subjects as "exposed uninfected" and have sought immunological correlates with this apparent resistance.

METHODS

We studied 40 exposed uninfected subjects testing negative for both HCV antibody and HCV RNA. Details of injection behavior were ascertained by questionnaire. In vitro interferon (IFN)-gamma production by T cells in response to HCV proteins (core, E1, NS3, NS4, and NS5) was quantified by enzyme-linked immunospot assay, and findings were compared with those in 21 healthy control subjects.

RESULTS

All exposed uninfected subjects reported sharing needles or other injection paraphernalia on multiple occasions. The mean duration of injecting was 9.3 years (range, 0.5-26 years), with a median estimated number of injection episodes of 8760. IFN-gamma production in response to HCV proteins was found in 23 (58%) of 40 exposed uninfected subjects versus 4 (19%) of 21 control subjects (P = .004), with 14 exposed uninfected subjects responding to multiple antigens, compared with none of the control subjects (P = .001).

CONCLUSIONS

The majority of long-term IDUs who remain uninfected by HCV despite their high-risk behavior have HCV-specific T cell responses. These responses were frequently found for multiple HCV proteins, making cross-reactivity to other homologous antigens unlikely. These responses may represent an immunological footprint of HCV exposure that has not resulted in viremia or HCV antibody seroconversion. The potential role played by these responses in protection from HCV infection is of clinical importance.

Programmed death 1 expression during antiviral treatment of chronic hepatitis B: Impact of hepatitis B e-antigen seroconversion

Hyperexpression of the programmed death 1 (PD-1) molecule is a hallmark of exhausted T-cells, having a negative impact on T-cell activation and function. We studied longitudinally 18 hepatitis B e antigen (HBeAg)-positive patients undergoing treatment with direct antivirals (telbivudine or lamivudine) to determine the relationship between treatment-induced viremia reduction and HBeAg seroconversion with respect to PD-1 levels and T-cell reactivity. PD-1 expression was assessed by (1) flow cytometry and (2) quantitative real-time polymerase chain reaction; hepatitis B virus (HBV)-specific CD8+ T-cells were quantitated by pentamer staining; T-cell reactivity to HBV antigens was determined by interferon gamma (IFNgamma) and interleukin 10 (IL-10) enzyme-linked immunosorbent spot (ELISPOT) assays; and central/effector memory phenotypes were defined by phenotypic markers. PD-1 expression correlated closely with viremia levels. On therapy, PD-1 decreased significantly on total CD8+ T-cells, HBV-specific CD8+ T-cells, and CD3+/CD8- T-cells both as the percentage of positive cells (P < 0.01) and as the mean fluorescent intensity (P < 0.05), and this was paralleled by a marked reduction of PD-1 messenger RNA levels (P = 0.001). HBeAg serocoversion (in 6/18 patients) resulted in a further PD-1 decrease with a 50% reduction in the frequency of PD-1+/CD8+ T-cells, which was not observed in patients remaining HBeAg-positive. The decrease in PD-1 expression was associated with increased frequencies of IFNgamma-producing T-cells and decreased frequencies of IL-10 producing T-cells. At baseline, PD-1 expression correlated directly with the frequency of hepatitis B core antigen (HBcAg) central and effector memory phenotypes, whereas an inverse correlation was observed between PD-1 expression and HBcAg-specific effector phenotypes.

CONCLUSION

These results demonstrate that in chronic HBV infection, both viremia levels and HBeAg drive PD-1 expression and resulting T-cell impairment. Treatment-induced suppression of HBV replication reduces PD-1 expression; however, additional immunotherapeutic interventions are needed for restoration of T-cell functions.

Dynamics of lamivudine-resistant hepatitis B virus during adefovir monotherapy versus lamivudine plus adefovir combination therapy

Adefovir dipivoxil has been used alone or together with lamivudine to suppress lamivudine-resistant hepatitis B virus (HBV). However, the dynamics of HBV populations under different selection pressures and their impact on treatment outcome are poorly understood. Pyrosequencing was applied to quantify longitudinally the evolution of wild type and lamivudine/adefovir-resistant HBV. Eight patients, with lamivudine-resistant HBV, were randomized to receive adefovir monotherapy or adefovir/lamivudine combination therapy for a median of 79 and 71 weeks, respectively. Pyrosequencing proved highly sensitive with a lower limit of quantitation of minor HBV populations of 2% irrespective of viraemia levels. Adefovir/lamivudine treatment resulted in greater viraemia reduction than adefovir monotherapy. During combination therapy, lamivudine-resistant HBV populations (codons 180 and 204) remained dominant (>90%) and no adefovir-resistance developed. During adefovir monotherapy, reversion to wild-type HBV was detected in two patients with one patient accumulating rapidly adefovir-resistant HBV along with increased viraemia. In conclusion, the dynamics of drug-resistant HBV strains vary under different selection pressures which have a significant impact on the success of rescue therapy, as well as for the selection of new mutations. The use of techniques such as Pyrosequencing provides an evidence-based approach for successful management of drug-resistant HBV.

APOBEC and iNOS are not the main intracellular effectors of IFN-gamma-mediated inactivation of Hepatitis B virus replication

BACKGROUND/AIM

Interferon-gamma (IFN-gamma) produced by activated T-cells is the principle mediator of non-cytolytic Hepatitis B virus (HBV) inactivation; however the intracellular pathways responsible are poorly defined. We investigated the role of IFN-gamma-inducible nitric oxide synthase (iNOS) and APOBEC3 (A3) enzyme family in the inhibition of HBV replication by IFN-gamma.

METHODS

Hepatoma-cell lines transfected with HBV DNA were treated with IFN-gamma. Viral replication, iNOS and A3 mRNAs were quantitated by TaqManPCR and the direct nitric oxide (NO) effect on HBV replication was investigated using an NO-donor. A3G antiviral activity was verified by co-transfection with its inhibitor, human immunodeficiency virus (HIV)-associated virion infectivity factor (Vif).

RESULTS

IFN-gamma caused a dose-dependent reduction (>50%) of HBV DNA in the absence of cytotoxicity. Although iNOS mRNA increased 45-fold in IFN-gamma treated cells, NO2- was not detectable in supernatants and the use of an NO-donor did not inhibit HBV replication. A3 enzyme mRNAs varied between cells and were >10-fold higher in lymphocytes than in liver tissue. IFN-gamma up-regulated A3G mRNA by three-fold, associated with significant HBV DNA decrease. However, A3G degradation by Vif did not abolish the antiviral effect of IFN-gamma against HBV.

CONCLUSIONS

IFN-gamma inhibits HBV replication and up-regulates both iNOS and A3G. However, other pathways appear to have a greater role in IFN-gamma-induced HBV inactivation in the liver.

Clinical trial: individualized treatment duration for hepatitis C virus genotype 1 with peginterferon-alpha 2a plus ribavirin

BACKGROUND

Individualized treatment regimens, taking into account the heterogeneity of patients with chronic hepatitis C, are needed to improve treatment outcomes.

AIM

To investigate prospectively the period of undetectable viraemia required for a high rate of sustained virological response in patients with chronic hepatitis C genotype 1 and the relationship to early viral kinetics.

METHODS

Forty-five chronic hepatitis C genotype 1 patients were given peginterferon-alpha 2a plus ribavirin. Viraemia and hepatocyte HCV-RNA levels were quantified using a TaqMan assay. Beyond the first time point of undetectable viraemia (<20 IU/mL) between baseline and treatment week 12, 32 of 45 (71%) patients were randomized to additional 12 weeks (G12); 24 weeks (G24) or 36 weeks therapy (G36). The remaining 13 patients received 48 weeks' treatment (G48).

RESULTS

The sustained virological response rates were: G12--five of 11 (45%); G2 --eight of 10 (80%); G36--eight of 11 (73%); G48--four of 13 (31%). The anti-viral efficacy (epsilon) and treatment-induced loss of infected hepatocytes (Mdelta), were significantly higher in patients with early viral clearance. In G12, patients with sustained virological response had lower baseline viraemia than those who relapsed.

CONCLUSIONS

Early viraemia clearance is a better marker than baseline viral load and differentiates chronic hepatitis C genotype 1 with high or low probability of sustained virological response. In patients with viraemia clearance within 12 weeks of starting peg-interferon/ribavirin therapy, an additional period of undetectable viraemia of minimum 24 weeks is required for high sustained virological response.

Telbivudine versus lamivudine in patients with chronic hepatitis B

BACKGROUND

Reducing hepatitis B virus (HBV) replication to minimal levels is emerging as a key therapeutic goal for chronic hepatitis B.

METHODS

In this double-blind, phase 3 trial, 1370 patients with chronic hepatitis B were randomly assigned to receive 600 mg of telbivudine or 100 mg of lamivudine once daily. The primary efficacy end point was noninferiority of telbivudine to lamivudine for therapeutic response (i.e., a reduction in serum HBV DNA levels to fewer than 5 log10 copies per milliliter, along with loss of hepatitis B e antigen [HBeAg] or normalization of alanine aminotransferase levels). Secondary efficacy measures included histologic response, changes in serum HBV DNA levels, and HBeAg responses.

RESULTS

At week 52, a significantly higher proportion of HBeAg-positive patients receiving telbivudine than of those receiving lamivudine had a therapeutic response (75.3% vs. 67.0%, P=0.005) or a histologic response (64.7% vs. 56.3%, P=0.01); telbivudine also was not inferior to lamivudine for these end points in HBeAg-negative patients. In HBeAg-positive and HBeAg-negative patients, telbivudine was superior to lamivudine with respect to the mean reduction in the number of copies of HBV DNA from baseline, the proportion of patients with a reduction in HBV DNA to levels undetectable by polymerase-chain-reaction assay, and development of resistance to the drug. Elevated creatine kinase levels were more common in patients who received telbivudine, whereas elevated alanine aminotransferase and aspartate aminotransferase levels were more common in those who received lamivudine.

CONCLUSIONS

Among patients with HBeAg-positive chronic hepatitis B, the rates of therapeutic and histologic response at 1 year were significantly higher in patients treated with telbivudine than in patients treated with lamivudine. In both the HBeAg-negative and the HBeAg-positive groups, telbivudine demonstrated greater HBV DNA suppression with less resistance than did lamivudine. (ClinicalTrials.gov number, NCT00057265 [ClinicalTrials.gov].).

Impact of NS5A Sequences of Hepatitis C Virus Genotype 1a on Early Viral Kinetics during Treatment with Peginterferon‐α2a plus Ribavirin

BACKGROUND. Hepatitis C virus (HCV) genotype 1 is the most prevalent genotype in Western countries, and treatment with pegylated interferon (pegIFN) plus ribavirin fails in 50%-60% of patients. Genetic variability within the NS5A dsRNA-dependent protein kinase binding domain (PKRbd) of HCV-1b has been associated with responsiveness to IFN- alpha . Little is known about NS5A sequences of HCV-1a. We investigated whether genetic variability of HCV-1a NS5A correlates with the early HCV kinetics during treatment.

METHODS

Twenty-four treatment-naive, HCV-1a-infected patients were treated with standard doses of pegIFN- alpha 2a plus ribavirin. HCV viremia was quantitated at days 0, 1, 2, and 3 and weeks 1, 2, 4, 8, and 12 of treatment. According to HCV kinetics, patients were classified as early rapid responders, early moderate responders, or early slow responders. The full-length HCV NS5A was sequenced at baseline and at week 1.

RESULTS

At baseline, variability of the NS5A C terminus (concentrated in the PKRbd) is associated with interferon efficacy but not with the second phase of the early viral decline that has been associated with a sustained virologic response. Comparisons between baseline and week-1 full-length sequences did not show significant increases in mutations.

CONCLUSIONS

Genetic variability of HCV-1a NS5A does not predict responsiveness to IFN- alpha . Differences in early kinetics during combination therapy are not due to selection of IFN-resistant HCV strains.

Protection of hepatocytes from cytotoxic T cell mediated killing by interferon-alpha

BACKGROUND

Cellular immunity plays a key role in determining the outcome of hepatitis C virus (HCV) infection, although the majority of infections become persistent. The mechanisms behind persistence are still not clear; however, the primary site of infection, the liver, may be critical. We investigated the ability of CD8+ T-cells (CTL) to recognise and kill hepatocytes under cytokine stimulation.

METHODS/PRINCIPLE FINDINGS

Resting hepatocytes cell lines expressed low levels of MHC Class I, but remained susceptible to CTL cytotoxicity. IFN-alpha treatment, in vitro, markedly increased hepatocyte MHC Class I expression, however, reduced sensitivity to CTL cytotoxicity. IFN-alpha stimulated hepatocyte lines were still able to present antigen and induce IFN-gamma expression in interacting CTL. Resistance to killing was not due to the inhibition of the FASL/FAS- pathway, as stimulated hepatocytes were still susceptible to FAS-mediated apoptosis. In vitro stimulation with IFN-alpha, or the introduction of a subgenomic HCV replicon into the HepG2 line, upregulated the expression of the granzyme-B inhibitor-proteinase inhibitor 9 (PI-9). PI-9 expression was also observed in liver tissue biopsies from patients with chronic HCV infection.

CONCLUSION/SIGNIFICANCE

IFN-alpha induces resistance in hepatocytes to perforin/granzyme mediate CTL killing pathways. One possible mechanism could be through the expression of the PI-9. Hindrance of CTL cytotoxicity could contribute to the chronicity of hepatic viral infections.

Genetic characteristics of hepatitis B virus genotypes as a factor for interferon-induced HBeAg clearance

The factors determining the responsiveness of different hepatitis B virus (HBV) genotypes to interferon treatment are not fully understood. We investigated the relationship between HBV genetic characteristics and the outcome of short (16 weeks) or prolonged (32 weeks) treatment with standard interferon-alpha in a prospectively followed cohort of 103 patients across Europe with HBeAg positive chronic hepatitis B. INNO-LiPA assays and HBV DNA sequencing were used to determine HBV genotypes, mutations in the core promoter and precore/core regions. After 16-weeks interferon-alpha treatment, the rate of HBeAg clearance was higher in genotype A versus all other genotypes (P = 0.014), or genotype D alone (P = 0.05). The HBV genome analysis revealed that: (i) after 16-weeks treatment, an HBV subpopulation with core promoter mutations emerged or increased (P < 0.001) only in genotype A; (ii) the core gene of genotype A has the lowest number of amino acid variations in comparison with genotypes B, C, or D. Logistic regression analysis identified genotype A as a positive predictor of short (16 weeks) treatment response (P = 0.001; odds ratio 6.19, 95 confidence interval 1.94-19.8), having a greater impact than baseline HBV DNA or alanine aminotransferase (ALT) levels. In contrast, the response to prolonged interferon-alpha treatment was not different between HBV genotypes. These results suggest that HBV genotype A responds earlier to interferon treatment than other genotypes, which is associated with its molecular characteristics. The optimal duration of interferon-based therapies in chronic hepatitis B may vary between different HBV genotypes.

Presence of hepatitis B virus core promoter mutations pre-seroconversion predict persistent viral replication after HBeAg loss

BACKGROUND

In patients with chronic hepatitis B virus (HBV) infection DNA levels do not always fall after anti-hepatitis B e (anti-HBe) seroconversion.

OBJECTIVES

To follow longitudinally through HB e antigen (HBeAg) loss HBV DNA levels and core promoter/precore sequences in a cohort of 21 chronic HBV carriers.

STUDY DESIGN

Treatment-naïve HBeAg seropositive HBV carriers were monitored through HBeAg loss for between 2 and 22 years (mean 9.3). Core promoter/precore sequences, genotypes, HBV DNA levels and HBe status were determined.

RESULTS

Patients were grouped into those in whom serum/plasma HBV DNA remained high after HBeAg loss (group 1, n=11; HBV DNA>5log(10)IU/ml) and those in whom HBV DNA declined (group 2, n=10). Re-appearance of HBeAg was seen in seven group 1 patients. Pre-seroconversion mutations in the core promoter region including A1762T and/or G1764A were detected more frequently in group 1 (P=0.031). Overall sequence changes at sites other than 1762/1764 were more common post-seroconversion in group 1 than group 2 patients (P=0.037).

CONCLUSIONS

The presence of core promoter mutations prior to HBeAg loss identified those patients in whom HBV DNA persisted at high levels and was associated with temporary re-emergence of serum HBeAg. These patients may benefit from early anti-viral treatment.

Impact of Early Viral Kinetics on T-Cell Reactivity during Antiviral Therapy in Chronic Hepatitis B

Background

The patterns of hepatitis B viral dynamics during different antiviral therapies and the associated changes in HBV-specific T-cell reactivity are not well defined.

Methods

We investigated the impact of early viral load decline on virus-specific T-cell reactivity in 30 hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B randomized to monotherapy with adefovir dipivoxil (ADV) or in combination with emtricitabine (ADV/FTC). Viral kinetics were analysed by mathematical modelling. T-cell reactivity to HBV core and/or surface antigens and natural killer T cell frequency were tested longitudinally, baseline to week 48, using EliSPOT assays and/or flow cytometry.

Results

Mathematical modelling of early HBV kinetics identified two subsets of patients: 11 fast responders (undetectable viraemia by week 12; eight on ADV/FTC three on ADV) and 19 slow responders who remained viremic (six on ADV/FTC 13 on ADV). The rate of infected hepatocyte loss was higher in fast than in slow responders ( P=0.0007), and correlated inversely with pre-treatment levels of intrahepatic covalently closed circular HBV DNA. The frequency of HBV core-specific CD4+ T-cells increased significantly only in fast responders, peaking between week 16 and 24, while the HBV surface-specific CD4+ T-cells increased in both subsets. These changes in CD4+ T-cell reactivity were transient however, and no increase in HBV-specific CD8+ T-cells was observed. By week 48, HBeAg seroconversion occurred only in 3/30 (10%) patients.

Conclusions

Early viraemia clearance facilitates recovery of virus-specific CD4+ T-cell reactivity, but appears insufficient to establish clinically relevant antiviral immunity.

Distribution and characteristics of hepatitis B virus genotype C subgenotypes in China

Genetic diversity within the same hepatitis B virus (HBV) genotype indicates the presence of several subgenotypes. We have found that genotype C is the most common in China, and this study aimed to determine the geographical distribution and characteristics of HBV-C subgenotypes in the country. A cohort of 534 patients with chronic HBV genotype C infection, collected across China, was analysed by nucleotide sequencing or polymerase chain reaction-restriction fragment length polymorphism. HBV-C1/Cs (n = 112, 21%) and HBV-C2/Ce (n = 397, 74%) were the most common HBV-C subgenotypes and showed different geographical distribution in China. No significant differences were found between patients infected with HBV-C1 and HBV-C2 when comparing liver function tests, hepatitis B e antigen positive rate and clinical manifestations. We identified two other types of HBV-C provisionally designated as HBV-CD1 and HBV-CD2, which have particular virological features and clustered in one geographic area. These two types of C/D hybrids have emerged through recombination with genotype D and encode serotype ayw2 hepatitis B surface antigen. In conclusion, there are at least four subtypes of HBV genotype C: subgenotypes C1, C2 and two types of C/D recombinants CD1 and CD2 in China, which have a distinct geographic distribution. Whether HBV-C subgenotypes differ in their impact on liver disease progression requires prospective studies.

Immunological techniques in viral hepatitis

The need to quantitate and monitor immune responses of large patient cohorts with standardized techniques is increasing due to the growing range of treatment options for hepatitis B and hepatitis C, the development of combination therapies, and candidate experimental vaccines for HCV. In addition, advances in immunological techniques have provided new tools for detailed phenotypic and functional analysis of cellular immune responses. At present, there is substantial variation in laboratory protocols, reagents, controls and analysis and presentation of results. Standardization of immunological assays would therefore allow better comparison of results amongst individual laboratories and patient cohorts. The EASL-sponsored and AASLD-endorsed Monothematic Conference on Clinical Immunology in Viral Hepatitis was held at the University College London, United Kingdom, Oct 7-8, 2006 to bring together investigators with research experience in clinical immunology of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections for in-depth discussion, critical evaluation and standardization of immunological assays. This report summarizes the information presented and discussed at the conference, but is not intended to represent a consensus statement. Our aim is to highlight topics and issues that were supported by general agreement and those that were controversial, as well as to provide suggestions for future work.

Impact of early viral kinetics on T-cell reactivity during antiviral therapy in chronic hepatitis B

BACKGROUND

The patterns of hepatitis B viral dynamics during different antiviral therapies and the associated changes in HBV-specific T-cell reactivity are not well defined.

METHODS

We investigated the impact of early viral load decline on virus-specific T-cell reactivity in 30 hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B randomized to monotherapy with adefovir dipivoxil (ADV) or in combination with emtricitabine (ADV/FTC). Viral kinetics were analysed by mathematical modelling. T-cell reactivity to HBV core and/or surface antigens and natural killer T cell frequency were tested longitudinally, baseline to week 48, using EliSPOT assays and/or flow cytometry.

RESULTS

Mathematical modelling of early HBV kinetics identified two subsets of patients: 11 fast responders (undetectable viraemia by week 12; eight on ADV/FTC three on ADV) and 19 slow responders who remained viremic (six on ADV/FTC 13 on ADV). The rate of infected hepatocyte loss was higher in fast than in slow responders (P = 0.0007), and correlated inversely with pre-treatment levels of intrahepatic covalently closed circular HBV DNA. The frequency of HBV core-specific CD4+ T-cells increased significantly only in fast responders, peaking between week 16 and 24, while the HBV surface-specific CD4+ T-cells increased in both subsets. These changes in CD4+ T-cell reactivity were transient however, and no increase in HBV-specific CD8+ T-cells was observed. By week 48, HBeAg seroconversion occurred only in 3/30 (10%) patients.

CONCLUSIONS

Early viraemia clearance facilitates recovery of virus-specific CD4+ T-cell reactivity, but appears insufficient to establish clinically relevant antiviral immunity.

Direct evidence for immunomodulatory properties of ribavirin on T-cell reactivity to hepatitis C virus

BACKGROUND/AIM

An understanding of ribavirin's beneficial effects on treatment outcome in chronic hepatitis C (CH-C) may help to develop new treatment approaches. Here we investigated whether ribavirin directly affects HCV-specific reactivity of CD4+T-lymphocytes from patients with CH-C.

METHODS

Peripheral blood mononuclear cells from forty HCV RNA positive patients were cultured ex vivo with HCV core, NS3, NS4 alone, and with different concentrations of ribavirin. Virus-specific CD4+ T-cell reactivity was analysed by a proliferation assay; quantitation of cytokine (interferon-gamma, IL-10, IL-5, IL-12p35, IL-12p40) mRNA levels; measurement of interferon-gamma and IL-10 production (by ELISA) and enumeration of interferon-gamma and IL-10 producing T-cells by Elispot assays.

RESULTS

At 2-5 microM ribavirin induced de novo or enhanced T-cell proliferation to HCV antigens in a proportion of patients. Increased T-cell proliferation was associated with decreased IL-10 production in response to HCV core and reduced frequency of IL-10 producing CD4+ T-cells, while interferon-gamma levels remained unchanged. At 20 microM ribavirin markedly suppressed T-cell proliferation, and interferon-gamma mRNA expression to HCV antigens.

CONCLUSIONS

Ribavirin, at clinically achievable plasma levels, modulates directly the T-cell responses to HCV antigens in some CH-C patients. Suppression of IL-10 production may represent a useful strategy to induce/augment T-cell reactivity to HCV.

Comparison of real-time PCR assays for monitoring serum hepatitis B virus DNA levels during antiviral therapy

The performance characteristics of the RealART and Molecular Beacons assays were compared with those of the Digene Hybrid Capture II assay (ultrasensitive). The results of the RealART and Digene Hybrid assays were related (r = 0.94; P < 0.001) and diverged by 2 orders of magnitude. The RealART assay can be used to effectively monitor serum hepatitis B virus DNA levels.

Individualization of antiviral treatment regimens for chronic hepatitis C

The treatment of patients with chronic hepatitis C has rapidly evolved in the past 10 years. The introduction of ribavirin and, more recently, its combination with pegylated interferon represent two landmark changes in improving the treatment efficacy. Overall, sustained virological response at present can be expected in 43-46% of patients infected with genotype 1 and 75-80% in genotype 2 or 3 infection. In addition, factors associated with a lower or greater chance of response to treatment have now been identified, thus providing a basis for modifying current therapy according to the needs of different patient groups. Accumulating evidence demonstrates that individualized treatment regimens, according to the timing of treatment-induced viral clearance, provide a safe and cost-effective approach, as well as an improvement in treatment efficacy.

Chronic hepatitis B: a critical appraisal of current approaches to therapy

BACKGROUND & AIMS

Treatment of chronic hepatitis B (CHB) involves a number of complex and controversial issues. Expert opinions may differ from those of practicing hepatologists and gastroenterologists. We aimed to explore this issue further after a critical review of the literature.

METHODS

A panel of 14 international experts graded the strength of evidence for 16 statements addressing 3 content areas: patient selection, therapeutic end points, and treatment options. Available data relating to the statements were reviewed critically in 3 small work groups. After discussion of each statement with the entire panel, the experts voted anonymously to accept or reject statements based on the strength of evidence and their experience. A total of 241 members of the American Association for the Study of Liver Diseases (AASLD) responded to the same statements and their responses were compared with those of the experts. A discordant response was defined as a difference of more than 20% in any of the 5 graded levels of response (accept or reject) between the 2 groups.

RESULTS

With the exception of 2 statements, the experts' responses were relatively uniform. However, the responses of the AASLD members were discordant from the experts in 12 statements, spanning all 3 content areas.

CONCLUSIONS

Several areas of disagreement on the management of CHB exist between experts and AASLD members. Our results indicate a potential knowledge gap among practicing hepatologists. Better educational efforts are needed to meet the challenge of managing this complex disorder in which even expert opinion occasionally may disagree.

Novel type of hepatitis B virus mutation: replacement mutation involving a hepatocyte nuclear factor 1 binding site tandem repeat in chronic hepatitis B virus genotype E

The genetic diversity of hepatitis B virus (HBV) strains has evolved through mutations such as point mutations, deletions or insertions, and recombination. We identified and characterized a novel type of mutation which is a complex of external insertion, deletion, and internal duplication in sequences from one of six patients with chronic hepatitis B virus genotype E (HBV/E). We provisionally named this mutation a "replacement mutation"; the core promoter upstream regulatory sequence/basic core promoter was replaced with a part of the S1 promoter covering the hepatocyte nuclear factor 1 (HNF1) binding site, followed by a tandem repeat of the HNF1 site. A longitudinal analysis of the HBV population over 6 years showed the clonal change from wild-type HBV/E to replacement-mutant type, resulting in a lower hepatitis B (HB) e antigen titer, a high HBV DNA level in serum, and progression of liver fibrosis. In an in vitro study using a replication model, the replacement-mutant HBV showed higher replication levels than the wild-type HBV/E replicon, probably mediated by altered transcription factor binding. Additionally, this HNF1 site replacement mutation was associated with excessive HB nucleocapsid protein expression in hepatocytes, in both in vivo and in vitro studies. This novel mutation may be specific to HBV genotype E, and its prevalence requires further investigation.

Lamivudine plus interleukin-12 combination therapy in chronic hepatitis B: antiviral and immunological activity

Interleukin-12 (IL-12) is an immunomodulatory cytokine that promotes cellular immunity. Pre-clinical data suggest that IL-12 inhibits hepatitis B virus (HBV) replication by stimulating interferon-gamma (IFN-gamma) production. We investigated whether a combination treatment with lamivudine plus recombinant human interleukin-12 (rhIL-12) will result in a greater and prolonged suppression of HBV replication in comparison with lamivudine monotherapy. Fifteen patients with HBeAg-positive chronic hepatitis B were randomized to receive either lamivudine alone for 24 weeks (group 1); combination of lamivudine for 16 weeks and rhIL-12 (200 ng/kg twice weekly), starting 4 weeks after initiation of lamivudine, for 20 weeks (group 2), or the same schedule as for group 2, with lamivudine and a higher dose of rhIL-12 (500 ng/kg, group 3). Serum HBV DNA levels, T-cell proliferation, frequency of virus-specific T-cells, and IFN-gamma production were evaluated serially during and 24 weeks posttreatment. Lamivudine plus rhIL-12/500 showed greater antiviral activity than lamivudine monotherapy. However, after stopping lamivudine in groups 2 and 3, serum HBV DNA increased significantly despite continuing rhIL-12 administration. Lamivudine plus rhIL-12 treatment was associated with a greater increase in virus-specific T-cell reactivity, IFN-gamma production, and an inverse correlation between the frequency of IFN-gamma-producing CD4+ T-cells and viremia. The T-cell proliferative response to HBcAg did not differ between the three groups. In conclusion, the addition of IL-12 to lamivudine enhances T-cell reactivity to HBV and IFN-gamma production. However, IL-12 does not abolish HBV replication in HBeAg-positive patients and does not maintain inhibition of HBV replication after lamivudine withdrawal.

Relationship between early HCV kinetics and T-cell reactivity in chronic hepatitis C genotype 1 during peginterferon and ribavirin therapy

BACKGROUND/AIMS

To gain understanding of inter-individual differences of treatment response in hepatitis C virus genotype 1 (HCV-G1) patients, we investigated simultaneously the early HCV kinetics and virus-specific T-cell reactivity.

METHODS

Thirty, treatment-naïve HCV-G1 patients received peginterferon-alfa2a 180 microg/week plus ribavirin 1000-1200 mg/day, with blood samples collected prospectively at protocol time-points. HCV RNA was quantitated with a TaqMan assay with mathematical modelling of HCV decay. Virus-specific CD4+/CD8+ T-cells were enumerated by Elispot assays.

RESULTS

HCV kinetic analysis identified two subgroups: fast (18/30) and slow (12/30) treatment-responders. Although these subgroups did not differ in any baseline characteristics, fast responders (FR) showed greater antiviral efficacy (epsilon) than slow responders (SR) (84.5+/-3.2 vs. 65.2+/-7.0%, P=0.002), and a higher rate of infected cell loss (delta) (0.56+/-0.2 vs. 0.04+/-0.02, P=0.038). The viral load drop (baseline to treatment week 4) was higher in FR vs. SR group (3.5+/-1.1 vs. 1.4+/-0.6 log10IU/mL, P<0.001). T-cell reactivity to HCV increased only in FR (after the loss of viraemia), but not in SR patients.

CONCLUSIONS

Assessment of early viral and T-cell kinetics during treatment reveals marked differences amongst HCV-G1 patients and may provide a basis for treatment individualization. Enhancement of antiviral T-cell reactivity requires rapid viraemia clearance, rather than immunostimulation alone.

Geographic distribution, virologic and clinical characteristics of hepatitis B virus genotypes in China

The significance of hepatitis B virus (HBV) genotypes for the heterogeneity of chronic HBV infection and severity of liver disease is not well understood. The aim of this study was to determine the distribution and virologic characteristics of HBV genotypes in China and possible association with the diversity of liver disease. The study includes 1096 chronic HBV carriers from nine provinces in China. We collected clinical and laboratory data and analysed the HBV strains in sera by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and nucleotide sequencing techniques. The most common HBV genotypes were B (41%) and C (53%), while genotypes A and D were also found. A North-South divide was identified in genotype B and C distribution - genotype C was predominant in northern China, while genotype B was more prevalent in southern provinces. Patients with genotype B were younger than those with genotype C, and had a lower prevalence of HBeAg - 65%vs 72%, respectively (P = 0.03). However, the severity of liver disease did not differ significantly between patients infected with genotype B or C - neither when comparing liver function tests (1024 patients), nor hepatic inflammation and fibrosis (264 patients). Amongst 47 patients with genotype D (by PCR-RFLP), 37 (79%) were infected with a new subtype (designated Dc), having a recombination fragment from genotype C precore/core region. This is the first large-scale HBV genotype study from China and convincing documentation of the North-to-South gradient of genotypes C vs B in this country. HBV DNA recombination over the surface and precore/core genes increases the diversity of HBV strains and may have diagnostic and clinical implications.

Blocking of interleukin-10 receptor--a novel approach to stimulate T-helper cell type 1 responses to hepatitis C virus

Chronic hepatitis C virus (HCV) infection is associated with weak CD4+ T-helper type 1 reactivity and enhanced interleukin-10 production to HCV antigens. Here we demonstrate in vitro that monoclonal antibody-induced blockade of IL-10 receptor (IL-10R) generates a favorable balance of CD4+ T-cell responses to HCV. The addition of anti-IL-10R to mononuclear cells leads to a dose-dependent increase of T-cell proliferative response to HCV core, non-structural proteins 3 and 4. In competition experiments, anti-IL-10R reversed the inhibitory effect of IL-10 on HCV-specific T-cell proliferation. Furthermore, the blockade of IL-10R altered the balance towards type 1 antiviral T-cell reactivity with an increased frequency of HCV-specific IFN-gamma producing T-cells and IFN-gamma secretion. The impact of IL-10R blockade on T-cell reactivity to HCV demonstrates the major role of IL-10 in suppressing antiviral T-cell responses. Blocking IL-10 activity may be a useful immunotherapy approach to enhance the efficacy of antiviral treatment in chronic hepatitis C.

Is hepatitis C virus infection of dendritic cells a mechanism facilitating viral persistence?

More than 170 million people worldwide are chronically infected with hepatitis C virus (HCV), which is a major cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Impaired T-cell reactivity to HCV, a hallmark of inefficient adaptive immunity, is believed to be responsible for the high propensity of HCV to cause chronic infection. Dendritic cells are the most potent antigen-presenting cells and many viruses affect various dendritic cell functions. Data suggest that such changes induced by HCV may have an important role in viral persistence. HCV has been shown to bind to dendritic cells, although viral replication within these cells occurs at a very low level. Dendritic cells from people with chronic HCV infection are impaired in their capacity to stimulate T cells. This impairment may be a consequence of changes in the expression of major histocompatibility complex and costimulatory molecules on its surface, as well as in the production of cytokines such as interleukin 12. In addition, hepatic dendritic cells may be affected by the tolerogenic microenvironment of the liver, possibly generating dendritic cells that promote regulatory T cells, which suppress the cellular immune response mounted against HCV.

A new intertype recombinant between genotypes C and D of hepatitis B virus identified in China

Hepatitis B virus (HBV) genotypes have a characteristic geographical distribution. More than 90 % of chronic HBV patients in China are infected with genotypes B or C. Here, eight HBV isolates that were initially classified as genotype D by PCR-restriction fragment length polymorphism analysis were analysed in detail. The complete HBV genome was sequenced and compared with 32 sequences retrieved from GenBank, representing HBV genotypes A–G. Phylogenetic analysis of the S gene (nt 10–800) classified all eight isolates as genotype D. However, phylogenetic analyses of nt 800–10 and the open reading frames (ORFs) of the precore/core and X genes classified all eight isolates as genotype C. This discordance between phylogenetic trees reconstructed on different ORFs suggested that intertype recombination has occurred in all eight isolates. By using the simplot program, the site of recombination with genotype D was located in the preS2/S region, spanning nt 10–799 in seven of eight isolates and nt 10–1499 in the other isolate. These results demonstrate that intertype recombination should be considered as a type of variation that increases the genetic diversity of HBV. Hybrids of different HBV genotypes might exhibit specific virological properties and their significance in the diagnosis and management of chronic hepatitis B deserves further investigation.

Hepatitis C virus persistence after spontaneous or treatment-induced resolution of hepatitis C

It is presumed that resolution of hepatitis C, as evidenced by normalization of liver function tests and disappearance of hepatitis C virus (HCV) RNA from serum, as determined by conventional laboratory assays, reflects virus eradication. In this study, we examined the expression of the HCV genome in the sera, peripheral blood mononuclear cells (PBMC), and, on some occasions, monocyte-derived dendritic cells (DC) long after resolution of hepatitis C by using a highly sensitive reverse transcription (RT)-PCR-nucleic acid hybridization (RT-PCR-NAH) assay. The samples obtained from 16 randomly selected patients (5 with spontaneous and 11 with treatment-induced resolution), monitored for up to 5 years, were studied by qualitative and semiquantitative RT-PCR-NAH and by real-time RT-PCR to detect the HCV RNA positive strand. The replicative HCV RNA negative strand was examined in PBMC after culture with a T-cell proliferation stimulating mitogen. The findings show that HCV RNA was carried in the convalescent-phase sera and/or PBMC in all 16 individuals investigated. Also, DC from six of seven patients were reactive for the HCV genome. Importantly, traces of the HCV RNA negative strand, suggesting progressing virus replication, were detected in the majority of mitogen-stimulated PBMC, including four samples collected 5 years after recovery. Sequencing of the HCV 5' untranslated region fragment revealed genotype 1b in four of nine individuals examined and genotypes 1a and 2a in three and two patients, respectively. These results imply that HCV RNA can persist at very low levels in the serum and peripheral lymphoid cells and that an intermediate replicative form of the HCV genome can persist in PBMC for many years after apparently complete spontaneous or antiviral therapy-induced resolution of chronic hepatitis C.

Single nucleotide polymorphisms in the interferon-gamma and interleukin-10 genes do not influence chronic hepatitis C severity or T-cell reactivity to hepatitis C virus

BACKGROUND

The mechanisms by which interferon-gamma (IFN-gamma) contributes to inter-individual heterogeneity in the severity of chronic hepatitis C (CH-C) are unknown. In 116 consecutive patients with CH-C, we tested the hypothesis that host genetic factors regulating IFN-gamma production and activity influence the severity of liver damage and hepatitis C virus (HCV)-specific T-cell reactivity.

METHODS

We determined the genotypes of functionally significant polymorphisms in the IFN-gamma gene and in the promoter of interleukin-10 (IL-10), a cytokine that counteracts IFN-gamma. We also measured concanavalin A (Con A)-stimulated IL-10 and IFN-gamma production, and the frequency of virus-specific T-cells, producing IFN-gamma or IL-10.

RESULTS

The grade of inflammation and the stage of fibrosis of CH-C showed no associations with either the IFN-gamma or IL-10 promoter polymorphisms or with Con A-stimulated IL-10 or IFN-gamma production. Similarly, there were no associations between HCV-specific T-cell frequencies and these host genetic factors. On multivariate analysis, the grade of inflammation and the duration of HCV infection accounted for only 37% of the variance in the stage of CH-C (P<0.0001). This percentage did not increase by including any genetic variables in the analyses.

CONCLUSION

Future studies investigating the entire cytokine gene sequences will provide better information regarding genetic variations responsible for inter-individual differences in the severity of CH-C.

Direct evidence that naturally occurring mutations within hepatitis B core epitope alter CD4+ T-cell reactivity

Exacerbations of chronic hepatitis B have been associated with accumulation of mutations in the HBV core gene, with amino acid (aa) substitutions clustering between aa 50 and 69. This region of the nucleocapsid protein is known as an immunodominant epitope for CD4+ T-lymphocytes, however the impact of these mutations on T-cell reactivity has not been investigated. For this purpose, we undertook fine mapping of the reactivity of peripheral blood lymphocytes, isolated from patients with acute (n = 8) or chronic hepatitis B (n = 10), against a panel of branched synthetic peptides. The peptide aa sequences corresponded to the wild type HBV (aa 50-69), or contained 1-3 aa changes derived on the basis of naturally occurring mutations. In four of eight patients with acute hepatitis B the wild type peptide 50-69, which corresponded to the core gene sequence of HBV present in these patients, induced a strong T-cell proliferative response. In the same cases, the T-cell response to the mutant peptides was altered at various degrees, depending on the number and the position of aa changes. The most pronounced inhibition of CD4+ T-cell response (between 44 and 92%) was caused by a peptide ligand with two aa substitutions at positions 64 and 67. These results demonstrate that mutations within immunodominant epitopes of the HBV nucleocapsid can affect the CD4+ T-lymphocyte reactivity, which may have a role for the accumulation of certain HBV strains after hepatitis flares during the course of chronic HBV infection.

Endocytosis of hepatitis B immune globulin into hepatocytes inhibits the secretion of hepatitis B virus surface antigen and virions

Hepatitis B immunoglobulin is used for prophylaxis against hepatitis B virus (HBV) and is thought to act by neutralization of virions and hepatitis B virus surface antigen (HBsAg)-containing particles in circulation. Using a panel of hepatocyte-derived cell lines, the present study investigated in vitro whether HBs-specific immunoglobulin G (IgG) is internalized in hepatocytes and whether it interacts with HBsAg in the cells. By immunoelectron microscopy and immunoblotting, human IgG and FcRn receptor for IgG were demonstrated on cellular membranes and in cytoplasmic extracts, irrespective of the HBsAg status of the cells. Furthermore, HBsAg and anti-HBs were shown to be colocalized in the same cellular compartment by two-color confocal microscopy. Endocytosis of HBs-specific IgG caused intracellular accumulation of HBsAg in a dose-dependent manner and inhibited the secretion of HBsAg and HBV virions from the cells. These effects were not observed with F(ab)(2) fragments or nonimmune IgG as controls. The specificity of intracellular HBsAg- anti-HBs interaction was further investigated in cells transfected with HBV genomes expressing wild-type HBsAg or immune escape HBsAg (with a G145R mutation). Monoclonal anti-HBs markedly reduced the secretion of wild-type HBsAg, while the secretion of mutant HBsAg was not affected. These results suggest that HBs-specific IgG binds to hepatocytes and interacts with HBsAg within the cells. This may be relevant for the selection of surface antibody escape mutations.