Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update

Worldwide, some 240 million people have chronic hepatitis B virus (HBV), with the highest rates of infection in Africa and Asia. Our understanding of the natural history of HBV infection and the potential for therapy of the resultant disease is continuously improving. New data have become available since the previous APASL guidelines for management of HBV infection were published in 2012. The objective of this manuscript is to update the recommendations for the optimal management of chronic HBV infection. The 2015 guidelines were developed by a panel of Asian experts chosen by the APASL. The clinical practice guidelines are based on evidence from existing publications or, if evidence was unavailable, on the experts' personal experience and opinion after deliberations. Manuscripts and abstracts of important meetings published through January 2015 have been evaluated. This guideline covers the full spectrum of care of patients infected with hepatitis B, including new terminology, natural history, screening, vaccination, counseling, diagnosis, assessment of the stage of liver disease, the indications, timing, choice and duration of single or combination of antiviral drugs, screening for HCC, management in special situations like childhood, pregnancy, coinfections, renal impairment and pre- and post-liver transplant, and policy guidelines. However, areas of uncertainty still exist, and clinicians, patients, and public health authorities must therefore continue to make choices on the basis of the evolving evidence. The final clinical practice guidelines and recommendations are presented here, along with the relevant background information.

Clinical emergence of entecavir-resistant hepatitis B virus requires additional substitutions in virus already resistant to Lamivudine

Entecavir (ETV) exhibits potent antiviral activity in patients chronically infected with wild-type or lamivudine (3TC)-resistant (3TC(r)) hepatitis B virus (HBV). Among the patients treated in phase II ETV clinical trials, two patients for whom previous therapies had failed exhibited virologic breakthrough while on ETV. Isolates from these patients (arbitrarily designated patients A and B) were analyzed genotypically for emergent substitutions in HBV reverse transcriptase (RT) and phenotypically for reduced susceptibility in cultures and in HBV polymerase assays. After 54 weeks of 3TC therapy, patient A (AI463901-A) received 0.5 mg of ETV for 52 weeks followed by a combination of ETV and 100 mg of 3TC for 89 weeks. Viral rebound occurred at 133 weeks after ETV was started. The 3TC(r) RT substitutions rtV173L, rtL180M, and rtM204V were present at study entry, and the additional substitutions rtI169T and rtM250V emerged during ETV-3TC combination treatment. Reduced ETV susceptibility in vitro required the rtM250V substitution in addition to the 3TC(r) substitutions. For liver transplant patient B (AI463015-B), previous famciclovir, ganciclovir, foscarnet, and 3TC therapies had failed, and RT changes rtS78S/T, rtV173L, rtL180M, rtT184S, and rtM204V were present at study entry. Viral rebound occurred after 76 weeks of therapy with ETV at 1.0 mg, with the emergence of rtT184G, rtI169T, and rtS202I substitutions within the preexisting 3TC(r) background. Reduced susceptibility in vitro was highest when both the rtT184G and the rtS202I changes were combined with the 3TC(r) substitutions. In summary, infrequent ETV resistance can emerge during prolonged therapy, with selection of additional RT substitutions within a 3TC(r) HBV background, leading to reduced ETV susceptibility and treatment failure.

Nomenclature for antiviral-resistant human hepatitis B virus mutations in the polymerase region

There is currently no universally accepted numbering convention for the antiviral drug-related resistance mutations in the reverse transcriptase (rt) domain of the human hepatitis B virus (HBV) polymerase. The published inconsistencies have resulted from different HBV genotypes. A standardized numbering system for HBV polymerase is proposed. The new system is based on functional observations of HBV surface gene proteins (preS1, preS2, and HBsAg) and on the current convention used for human immunodeficiency virus type 1 (HIV-1) polymerase proteins (protease, rt, and integrase), in which the amino acid numbering restarts at the first codon position of each domain. The HBV polymerase protein can be divided into 4 domains (terminal protein, spacer, rt, ribonuclease H) and each of these can be numbered separately. In this proposal, the HBV rt domain starts with the highly conserved EDWGPCDEHG motif, contains 344 amino acids, and the lamivudine-related resistance mutations are found at amino acid rtL180M (previously amino acid 528, 526, 515, or 525) and rtM204V/I (previously 552, 550, 539, or 549). The new consensus rt domain numbering system is genotype independent and allows investigators to number any previously and newly discovered antiviral-related amino acid change in a standardized manner.

Structural organization of the hepatitis B virus minichromosome

The replicative intermediate of hepatitis B virus (HBV), the covalently closed, circular DNA, is organized into minichromosomes in the nucleus of the infected cell by histone and non-histone proteins. In this study we investigated the architecture of the HBV minichromosome in more detail. In contrast to cellular chromatin the nucleosomal spacing of the HBV minichromosome has been shown to be unusually reduced by approximately 10 %. A potential candidate responsible for an alteration in the chromatin structure of the HBV minichromosome is the HBV core protein. The HBV core protein has been implicated in the nuclear targeting process of the viral genome. The association of the HBV core protein with nuclear HBV replicative intermediates could strengthen this role. Our findings, confirmed by in vivo and in vitro experiments indicate that HBV core protein is a component of the HBV minichromosome, binds preferentially to HBV double-stranded DNA, and its binding results in a reduction of the nucleosomal spacing of the HBV nucleoprotein complexes by 10 %. From this model of the HBV minichromosome we propose that the HBV core protein may have an impact on the nuclear targeting of the HBV genome and be involved in viral transcription by regulating the nucleosomal arrangement of the HBV regulatory elements, probably in a positive manner.

The covalently closed duplex form of the hepadnavirus genome exists in situ as a heterogeneous population of viral minichromosomes

Replication of hepadnaviruses requires a persistent population of covalently closed circular (CCC) DNA molecules in the nucleus of the infected cell. It is widely accepted that the vital role of this molecule is to be the sole DNA template for the synthesis by RNA polymerase II of all viral transcripts throughout the infection process. Since the transcriptional activity of eukaryotic nuclear DNA is considered to be determined in part by its specific organization as chromatin, the nucleoprotein disposition of the hepadnavirus CCC DNA was investigated. These studies were undertaken on the duck hepatitis B virus (DHBV) CCC DNA present in the liver cell nuclei of DHBV-infected ducks. The organization and protein associations of the DHBV CCC DNA in situ were inferred from sedimentation, micrococcal nuclease digestion, and DNA superhelicity analyses. These three lines of investigation demonstrate that the DHBV CCC DNA is stably associated with proteins in the nuclei of infected liver cells. Moreover, they provide compelling evidence that the viral nucleoprotein complex is indeed a minichromosome composed of classical nucleosomes but in arrays that are atypical for chromatin. When the DHBV chromatin is digested with micrococcal nuclease, a ladder of viral DNA fragments that exhibits a 150-bp repeat is produced. This profile for the viral chromatin is obtained from the same nuclei in which the duck chromatin shows the standard 200-bp ladder. The superhelicity of the DHBV CCC DNA ranges from 0 to 20 negative supertwists per molecule, with all possible 21 topoisomers present in each DNA preparation. The 21 topoisomers of DHBV CCC DNA are inferred to derive from an identically diverse array of viral minichromosomes. In the DHBV minichromosomes composed of 20 nucleosomes, 96.7% of the viral DNA is calculated to be compacted into these chromatin subunits spaced on average by 5 bp of linker DNA; other minichromosomes contain fewer nucleosomes and proportionately more linker DNA. Two major subpopulations of DHBV minichromosomes are detected with comparable prevalence. The two groups correspond to minichromosomes which contain essentially a full or half complement of nucleosomes. The functional significance of this minichromosome diversity is unknown but is suggestive of transcriptional regulation of the viral DNA template.

Role of alcohol in the progression of liver disease caused by hepatitis C virus infection

In patients with chronic hepatitis C, alcohol consumption has been proposed as a risk factor for the progression of liver disease; however, evidence for this remains conflicting. Two hundred thirty-four anti-hepatitis C virus (HCV)-positive patients who had a liver biopsy performed within the past 24 months were studied. Demographic data and information on risk factors were recorded. A detailed lifetime alcohol consumption history was obtained. Viral studies included HCV viral titer and HCV genotype. Mean age (+/- SEM) of the group was 40.8 +/- 0.7 years. One hundred sixty-six (71%) were male. A risk factor for HCV infection was found in 195 patients (86%). Genotype distribution was: 1b: 22%; 1a: 15%; 1(nonsubtypable): 15%; 3a: 34%; and 2: 7%. Fifty (21%) patients had cirrhosis. Patients with cirrhosis were older (51.6 +/- 1.8 years) than those with chronic hepatitis (37.6 +/- 0.6 years; P = .0001), were infected at an older age (25.9 +/- 2.0 vs. 20.9 +/- 0.6 years; P = .001), and had a longer duration of infection (20.5 +/- 1.3 vs. 16.2 +/- 0.5 years; P = .0008). Patients with cirrhosis had a greater total lifetime alcohol consumption (288,765 +/- 58,115 g) than those with chronic hepatitis (189,941 +/- 15,453 g; P = .018). Cirrhotic patients also had greater total alcohol consumption during the period of infection with HCV (240,962 +/- 63,756 g vs. 146,510 +/- 12,862 g; P = .02). On multivariate analysis, subject age and total alcohol consumption were independently associated with the presence of cirrhosis. Total lifetime alcohol consumption is a risk factor for the progression of liver disease caused by HCV.

Tenofovir disoproxil fumarate rescue therapy following failure of both lamivudine and adefovir dipivoxil in chronic hepatitis B

OBJECTIVE

To determine the efficacy of tenofovir disoproxil fumarate (TDF) in adults with chronic hepatitis B virus (HBV) infection who had previously failed lamivudine (LAM) and had significant viral replication (HBV DNA >10⁵ copies/ml if HBeAg positive, > 10⁴ copies/ml if HBeAg negative) despite at least 24 weeks of treatment with adefovir dipivoxil (ADV).

DESIGN

A prospective open-label study of TDF 300 mg daily. Patients receiving combination ADV/LAM prior to baseline were switched to TDF/LAM.

SETTING

Multiple tertiary referral centres.

METHODS

Sixty patients were enrolled. The median age was 48.5 years (range 21e80), 46 (77%) were male and 40 (67%) were HBeAg positive. Thirty-eight patients (63%) were switched from ADV to TDF, the remainder from ADV/LAM to TDF/LAM. At baseline, substitutions conferring resistance to LAM or ADV were present in 20 patients (33%) and 17 patients (28%), respectively. The median baseline viral load was 5.33 log₁₀ IU/ml (range 2.81-8.04). Patients initially treated with TDF monotherapy with persistent viral replication at or after 24 weeks were switched to TDF/LAM. The main outcome measures were change in HBV viral load from baseline and percentage of patients achieving an undetectable viral load (<15 IU/ml).

RESULTS

Results are reported at 96 weeks of treatment. One patient discontinued TDF at 10 days due to rash. The time-weighted change in viral load from baseline to week 12 was -2.19 log10 IU/ml overall. The median change in HBV DNA from baseline to weeks 12, 24, 48 and 96 was -2.86, -3.23, -3.75 and -4.03 log₁₀ IU/ml, respectively. At 48 and 96 weeks, 27/59 (46%) and 38/59 (64%) patients achieved a HBV DNA <15 IU/ml. The response was independent of baseline LAM therapy or mutations conferring ADV resistance.

CONCLUSIONS

In heavily pretreated patients with a high rate of genotypic resistance, TDF retains significant activity against HBV although this appears diminished in comparison with studies of naïve patients.

Analysis of hepatitis B viral load decline under potent therapy: complex decay profiles observed

We used a new real-time polymerase chain reaction (PCR)-based assay that is sensitive, has a wide dynamic linear range, and is highly reproducible to quantify hepatitis B virus (HBV) DNA in the serum of infected individuals undergoing potent antiviral therapy. In addition, we made frequent measurements of viral load after initiation of treatment and maintained follow-up to about 12 weeks. To analyze the data we used a new model of HBV decay, which takes into account that existing drug treatments do not completely block de novo infection and the possibility of noncytolytic loss of infected cells. On initiation of therapy, there was a mean delay of 1.6 days followed by a biphasic or muliphasic decay of plasma HBV DNA. The slope of the first phase varied considerably, with one individual having rapid decay, corresponding to a virion half-life of 1 hour, but others showing half-lives of up to 92 hours. Individuals either had a slow second-phase decline (t((1/2)) = 7.2 +/- 1.2 days) or a flat second phase. Some individuals exhibited a complex "staircase pattern" of decay, with further phases of viral DNA decline and phases with little change in viral load.

The phenylpropenamide derivative AT-130 blocks HBV replication at the level of viral RNA packaging

Nucleos(t)ide analogue antiviral therapy for chronic hepatitis B has proven to be effective in the short term but the frequent development of resistance limits its clinical utility. Agents targeting other stages of viral replication are needed in order to develop improved combination therapies. The phenylpropenamide derivatives AT-61 and AT-130 have been shown to inhibit HBV replication in vitro, but the mechanism of action of these compounds remains undefined. The aim of this study was to determine the mechanism of action of AT-130, a non-nucleoside inhibitor of HBV in several in vitro models of replication. These studies found that AT-130 inhibited HBV DNA replication in hepatoma cells but had no effect on viral DNA polymerase activity or core protein translation. Total HBV RNA production was also unaffected in the presence of the drug whilst the amount of encapsidated RNA was significantly reduced, thereby inhibiting subsequent viral reverse transcription. These studies have established that the inhibition of HBV genome replication by a non-nucleoside analogue acting at the level of viral encapsidation and packaging is a potentially useful strategy for future therapeutic drug development in the management of chronic hepatitis B.

Spread of bloodborne viruses among Australian prison entrants

OBJECTIVES

To assess spread of bloodborne viruses among prison entrants in Victoria, Australia.

DESIGN

Voluntary confidential testing of all prison entrants for markers of exposure to bloodborne viruses with collection of minimal data on demography and risk factors over 12 months.

SETTING

Her Majesty's Prisons, Pentridge and Fairlea, Victoria, Australia.

SUBJECTS

3429 male and 198 female prison entrants (> 99% of all prison entrants); 344 entered prison and were tested more than once.

MAIN OUTCOME MEASURES

Prevalence and incidence of antibodies to HIV, hepatitis B, and hepatitis C viruses, and minimal data on risk factors.

RESULTS

1562 (46%) gave a history of use of injected drugs, 1171 (33%) had antibody to hepatitis B core antigen, 1418 (39%) were anti-hepatitis C positive including 914 (64%) of the men who injected drugs, 91 (2.5%) were positive for hepatitis B surface antigen, and 17 (0.47%) were positive for antibody to HIV. Incidence rates for infection with hepatitis B and C virus were 12.6 and 18.3 per 100 person years, respectively; in men who injected drugs and were aged less than 30 years (29% of all prison entrants) these were 21 and 41 per 100 person years. Seroconversion to hepatitis B or C was associated with young age and shorter stay in prison. Only 5% of those who were not immune to hepatitis B reported hepatitis B immunisation.

CONCLUSIONS

Hepatitis B and C are spreading rapidly through some populations of injecting drug users in Victoria, particularly among men aged less than 30 years at risk of imprisonment in whom rates of spread are extreme; this group constitutes a sizeable at risk population for spread of HIV. This spread is occurring in a context of integrated harm reduction measures outside prisons for prevention of viral spread but few programmes within or on transition from prisons; it poses an urgent challenge to these programmes.

Detection of specific anti-leptospiral immunoglobulins M and G in human serum by solid-phase enzyme-linked immunosorbent assay

The enzyme-linked immunosorbent assay (ELISA) was used to detect leptospire-specific immunoglobulin M (IgM) and IgG in the sera of patients infected with leptospiral serovars hardjo, pomona, or copenhageni. All patients produced specific IgM and IgG detectable by ELISA. In contrast, only a few patients produced IgG agglutinins whereas all produced IgM agglutinins. The specificity and sensitivity of the test suggest that the ELISA anti-IgM technique is a suitable method for detecting leptospiral antibodies in human sera for diagnostic and epidemiological purposes.

Hepatitis B virus polymerase mutations during antiviral therapy in a patient following liver transplantation

BACKGROUND/AIMS

The purpose of this study was to investigate possible resistance mutations which arose in the polymerase gene of hepatitis B virus (HBV) in a patient with severe recurrent HBV infection following liver transplantation. The patient's management included antiviral chemotherapy for almost 4 years comprising ganciclovir, foscarnet and famciclovir. In the last 2.5 years of famciclovir treatment, an increase in serum HBV DNA levels and a reduced sensitivity of the virion-associated DNA polymerase to penciclovir triphosphate were observed.

METHODS

The viral polymerase gene and X gene were sequenced from serum samples collected at representative time intervals covering the entire treatment period.

RESULTS

No mutations were detected in the X gene. Three nucleotide mutations, each of which resulted in an altered amino acid sequence, were detected in the polymerase gene after 816 days of total antiviral therapy (370 days of famciclovir). Two of these mutations were detected by direct sequencing and the third was detected after cloning and was present in 10% of the clones. All three mutations occurred in "region B" of RNA-dependent DNA polymerases. The HBV polymerase has similarities to both RNA and DNA polymerases. These mutations in the HBV polymerase gene were located in a similar area to the penciclovir-induced mutations observed in the herpes simplex virus DNA polymerase gene.

CONCLUSIONS

Three mutations within the HBV polymerase gene were detected which were associated with a reduced penciclovir sensitivity.

Hepatitis C virus infection among a cohort of Victorian injecting drug users

OBJECTIVE

To describe the epidemiology of infection with hepatitis C virus (HCV) among injecting drug users (IDUs) in Victoria.

DESIGN AND SUBJECTS

Subjects were current IDUs from a wide spectrum of age, sex and social background, enrolled in a prospective study of injecting drug use. They were contacted by peer workers through their social networks and through community agencies and prisons, and were regularly followed for interview and blood collection in the field. Sera were tested for presence of antibody to HCV (anti-HCV), for the presence of HCV RNA directly in serum, and for measures of liver function. The results were correlated with demographic variables.

SETTING

Rural and metropolitan Victoria.

MAIN OUTCOME MEASURES

Presence of anti-HCV and demonstration of HCV RNA.

RESULTS

Two-thirds (68%, 206/303) of the current cohort of IDUs were seropositive for HCV, risk being particularly associated with duration of injecting, and independently for men with opiate use and prison history, and for women with a history of methadone therapy. HCV RNA was detected in 48% (76/160) by polymerase chain reaction (PCR); 61% (74/122) of these subjects were HCV seropositive and 5% (2/38) seronegative. Of 32 HCV seronegative subjects followed for a mean period of 291 days, five seroconverted to HCV, an incidence of 20 infections per 100 person-years. Those who seroconverted were older, more likely to be male, had been injecting longer, more often reported opiate use, and were more likely to be based in the country. Serum liver enzyme levels were higher and more likely to be abnormal in HCV seropositive than seronegative subjects, and were highest in those seropositive subjects in whom HCV RNA was detected.

CONCLUSIONS

This population of IDUs has a very high rate of exposure to HCV, related to duration of injecting and independently to opiate use and prison history, perhaps reflecting increased risk in particular social networks. There is evidence of high rates of carriage of HCV, of continuing transmission of HCV, and of ongoing liver disease among these IDUs. If these IDUs are at all representative of all IDUs in Australia, we estimate that 80,000 current and former IDUs may be at risk of chronic liver disease from HCV, and that 8000-10,000 new infections may be occurring each year. Two subjects who were seronegative had HCV RNA detectable in sera. These data have important implications for screening programs and document the need for further measures to prevent spread of blood-borne viruses including HIV among IDUs.

Long-term entecavir treatment results in sustained antiviral efficacy and prolonged life span in the woodchuck model of chronic hepatitis infection

Entecavir (ETV) is a guanosine nucleoside analogue with potent antiviral efficacy in woodchucks chronically infected with woodchuck hepatitis virus. To explore the consequences of prolonged virus suppression, woodchucks received ETV orally for 8 weeks and then weekly for 12 months. Of the 6 animals withdrawn from therapy and monitored for an additional 28 months, 3 had a sustained antiviral response and had no evidence of hepatocellular carcinoma (HCC). Of the 6 animals that continued on a weekly ETV regimen for an additional 22 months, 4 exhibited serum viral DNA levels near the lower limit of detection for >2 years and had no evidence of HCC. Viral antigens and covalently closed circular DNA levels in liver samples were significantly reduced in all animals. ETV was well tolerated, and there was no evidence of resistant variants. On the basis of historical data, long-term ETV treatment appeared to significantly prolong the life of treated animals and delay the emergence of HCC.

In vitro susceptibilities of wild-type or drug-resistant hepatitis B virus to (-)-beta-D-2,6-diaminopurine dioxolane and 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil

Prolonged treatment of chronic hepatitis B virus (HBV) infection with lamivudine ([-]-beta-L-2',3'-dideoxy-3' thiacytidine) or famciclovir may select for viral mutants that are drug resistant due to point mutations in the polymerase gene. Determining whether such HBV mutants are sensitive to new antiviral agents is therefore important. We used a transient transfection system to compare the sensitivities of wild-type HBV and four lamivudine- and/or famciclovir-resistant HBV mutants to adefovir [9-(2-phosphonyl-methoxyethyl)-adenine; PMEA] and the nucleoside analogues (-)-beta-D-2, 6-diaminopurine dioxolane (DAPD) and 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU). The drug-resistant mutants contained amino acid substitutions in the polymerase protein. We found that the M550I and M550V plus L526M substitutions, which confer lamivudine resistance, did not confer cross-resistance to adefovir or DAPD, but conferred cross-resistance to L-FMAU. The M550V substitution in isolation conferred a similar phenotype to M550I, except that it did not confer significant resistance to L-FMAU. The L526M substitution, which is associated with famciclovir resistance, conferred cross-resistance to L-FMAU but not to adefovir or DAPD. Inhibition of HBV secretion by DAPD, L-FMAU, and adefovir did not always correlate with inhibition of the generation of intracellular HBV replicative intermediates, suggesting that these analogs may preferentially inhibit specific stages of the viral replication cycle.

Lamivudine therapy in patients undergoing liver transplantation for hepatitis B virus precore mutant-associated infection: high resistance rates in treatment of recurrence but universal prevention if used as prophylaxis with very low dose hepatitis B immune globulin

Recurrent hepatitis B virus (HBV) infection remains a major cause of morbidity and mortality after liver transplantation. Recently, antiviral therapy, such as lamivudine, has become available for prophylaxis against HBV reactivation posttransplantation and for the treatment of HBV recurrent disease. We report our initial experience with lamivudine therapy in patients with precore mutant-associated HBV infection undergoing liver transplantation (n = 29). Outcomes were compared in three patient groups: group 1, precore mutant HBV infection not receiving lamivudine (n = 10); group 2, recurrent precore mutant HBV infection posttransplantation subsequently treated with lamivudine (n = 10); and group 3, HBV precore mutant patients undergoing liver transplantation and receiving lamivudine and low-dose hepatitis B immune globulin (HBIG) from the time of transplantation (n = 9). In group 1, HBV recurred in 9 of 10 patients, with subsequent graft loss in all 9 patients. In group 2, all patients developed HBV recurrence at a mean of 7.3 months posttransplantation and started lamivudine therapy at a median of 16 months posttransplantation. Follow-up on lamivudine therapy was for a median of 11 months. Six of these 10 patients developed mutations in the HBV polymerase gene associated with lamivudine resistance. There were two liver failure-related deaths in this group. In group 3 patients, there was one death from graft-versus-host disease. The remaining 8 patients have been followed up for a mean of 15.6 months posttransplantation, and all remain hepatitis B surface antigen negative and HBV DNA negative. In conclusion, lamivudine therapy in association with low-dose HBIG is effective in preventing HBV reactivation posttransplantation. Rescue therapy with lamivudine in patients with HBV recurrence is only moderately effective, with a 60% lamivudine resistance rate in patients treated for longer than 6 months.

Anti-viral therapy for prevention of perinatal HBV transmission: extending therapy beyond birth does not protect against post-partum flare

BACKGROUND

Antepartum anti-viral therapy (AVT) is often administered to prevent perinatal transmission of hepatitis B virus (HBV) infection. Little is known about the effect of AVT on post-partum flare rates and severity.

AIM

To examine whether extending AVT beyond birth influences the post-partum course.

METHODS

One hundred and one pregnancies in 91 women with HBV DNA levels ≥log 7 IU/mL were included. AVT (initially lamivudine, later tenofovir disoproxil fumarate) was commenced from 32 weeks gestation and stopped soon after birth and at 12 weeks post-partum. Outcomes according to post-partum treatment duration were examined: Group 1 = AVT ≤4 weeks (n = 44), Group 2 = AVT >4 weeks (n = 43), Group 3 = no AVT (n = 14).

RESULTS

The majority of women were HBeAg+ (97%), median age 29 years, baseline HBV DNA log 8.0 IU/mL and follow-up 48 weeks post-partum. Post-partum treatment duration was 2 weeks for Group 1 and 12 weeks for Group 2, P < 0.01. Flare rates were not significantly different: Group 1 = 22/44 (50%), Group 2 = 17/43 (40%) and Group 3 = 4/14 (29%), P = 0.32. Onset of flare was similar at 8/10/9 weeks post-partum for Groups 1/2/3 respectively, P = 0.34. The majority of flares spontaneously resolved. HBeAg seroconversion (n = 1/5/1 in Groups 1/2/3, P = 0.27) was not associated with treatment duration or the occurrence of a post-partum flare.

CONCLUSIONS

Post-partum flares are common and usually arise early after delivery. They are often mild in severity and most spontaneously resolve. Extending anti-viral therapy does not protect against post-partum flares or affect HBeAg seroconversion rates.

Antiviral chemotherapy for the treatment of hepatitis B virus infections

Approximately 5% of the world's human population have an increased risk for developing liver cancer and cirrhosis as a direct consequence of chronic infection with the hepatitis B virus (HBV). Antiviral chemotherapy remains the only option for controlling infection in these individuals, for whom the current licensed hepatitis B vaccines provide no benefit. Interferon (IFN)-alpha has proven benefit in a well-defined group of those with hepatitis B but has made little impact on the global burden of chronic liver disease. The development of more effective chemotherapy for treatment of chronic hepatitis B infection has proven to be extremely challenging, the result of both virus- and host-dependent factors, which will be reviewed in this article. Past attempts to treat chronic hepatitis B infection using nucleoside analogues were disappointing, but more recently, several nucleoside (or nucleotide) analogues have been identified that are potent and selective inhibitors of HBV replication. These agents fall into two broad categories: (1) nucleoside/nucleotides that have modified sugar residues in either cyclic or acyclic configurations and (2) stereoisomers of nucleosides in the "unnatural" L-configuration. Of the analogues that have been used clinically, representatives of the first category are purine derivatives, e.g., adefovir dipivoxil and famciclovir, whereas representatives of the second category are pyrimidine derivatives, such as lamivudine.

Resistance of hepatitis B virus to antiviral drugs: current aspects and directions for future investigation

Despite the existence of vaccines, chronic hepatitis B virus (HBV) infection remains a major health problem worldwide. Interferon therapy successfully controls infection in only a small percentage of chronically infected individuals. The recent approval of the nucleoside analogue lamivudine for the treatment of chronic HBV infection has ushered in a new era of antiviral therapy. While lamivudine is highly effective at controlling viral infection short-term, prolonged therapy has been associated with an increasing incidence of viral resistance. Thus, it appears that lamivudine alone will not be sufficient to control chronic viral infection in the majority of individuals. In addition to lamivudine, several new nucleoside and nucleotide analogues that show promising antihepadnaviral activity are in various stages of development. Lamivudine resistance has been found to confer cross-resistance to some of these compounds and it is likely that resistance to newer antivirals may also develop during prolonged use. Drug resistance therefore poses a major threat to nucleoside analogue-based therapies for chronic HBV infection. Fortunately, combination chemotherapy (antiviral therapy with two or more agents) can minimize the chance that resistance will develop and can be expected to achieve sustained reductions in viral load, provided that suitable combinations of agents are chosen. Here we review the basis of drug resistance in HBV, with emphasis on aspects that are likely to affect drug choice in future.

In vitro antiviral activity of penciclovir, a novel purine nucleoside, against duck hepatitis B virus

The in vitro antihepadnavirus activities of the purine nucleoside analogs ganciclovir (9-[2-hydroxy-1-(hydroxymethyl)ethoxymethyl]guanine) and penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] were compared in primary duck hepatocyte cultures congenitally infected with the duck hepatitis B virus (DHBV). Both compounds inhibited DHBV DNA replication to a comparable extent during continuous short-term treatment of the cultures. However penciclovir was more active both during longer-term continuous treatment (50% inhibitory concentrations: penciclovir, 0.7 +/- 0.1 microM; ganciclovir, 4.0 +/- 0.2 microM) and in washout experiments (50% inhibitory concentrations: penciclovir, 3.0 +/- 0.4 microM; ganciclovir, 46 +/- 1.5 microM) designed to compare the persistence of inhibitory activity after removal of the extracellular compound. The effects on viral protein synthesis were similar to the effects on viral DNA replication. These data suggest that penciclovir or its oral form, famciclovir, may have clinical utility in the treatment of chronic hepatitis B virus infection.

Hepatitis B virus mutations associated with antiviral therapy

The hepatitis B virus (HBV) replicates via an error prone viral reverse transcriptase resulting in a large pool of quasispecies with mutations spread throughout the genome. During antiviral drug selection pressure (e.g., lamivudine, adefovir, or entecavir) HBV mutants are selected from the pre-existing pool of quasispecies and over time become the dominant species. Not all mutations result in replication competent virus as HBV has the added complexity of overlapping reading frames. The HBV polymerase (Pol) gene overlaps the hepatitis B surface antigen (HBsAg) in a frame-shifted manner with the result that drug-resistant mutations in the HBV Pol can directly impact on the nature of HBsAg and its function. HBV genomic databases have been established to monitor antiviral selected mutations and are useful in determining conserved residues, genotypic differences, polymorphisms, and the mutation profiles selected under different antiviral selection pressures. These HBV databases may aid in the development of new diagnostic reagents as well as the monitoring of polymerase and envelope mutations selected under different antiviral pressures. Antiviral drug resistant mutants emerge as a function of at least six factors: the viral mutation frequency, the intrinsic mutability of the antiviral target site, the selective pressure exerted by the drug, the magnitude and rate of virus replication, the overall replication fitness of the mutant, and the availability of replication space. Only a limited number of HBsAg mutations selected during antiviral treatment have been characterized and the diagnostic and public health implications of these mutations need further investigation. Clearly, improved treatment strategies are required urgently to prevent the continued selection of HBV drug-resistant mutants.

Cross-resistance testing of antihepadnaviral compounds using novel recombinant baculoviruses which encode drug-resistant strains of hepatitis B virus

Long-term nucleoside analog therapy for hepatitis B virus (HBV)-related disease frequently results in the selection of mutant HBV strains that are resistant to therapy. Molecular studies of such drug-resistant variants are clearly warranted but have been difficult to do because of the lack of convenient and reliable in vitro culture systems for HBV. We previously developed a novel in vitro system for studying HBV replication that relies on the use of recombinant baculoviruses to deliver greater than unit length copies of the HBV genome to HepG2 cells. High levels of HBV replication can be achieved in this system, which has recently been used to assess the effects of lamivudine on HBV replication and covalently closed circular DNA accumulation. The further development of this novel system and its application to determine the cross-resistance profiles of drug-resistant HBV strains are described here. For these studies, novel recombinant HBV baculoviruses which encoded the L526M, M550I, and L526M M550V drug resistance mutations were generated and used to examine the effects of these substitutions on viral sensitivity to lamivudine, penciclovir (the active form of famciclovir), and adefovir, three compounds of clinical importance. The following observations were made: (i) the L526M mutation confers resistance to penciclovir and partial resistance to lamivudine, (ii) the YMDD mutations M550I and L526M M550V confer high levels of resistance to lamivudine and penciclovir, and (iii) adefovir is active against each of these mutants. These findings are supported by the limited amount of clinical data currently available and confirm the utility of the HBV-baculovirus system as an in vitro tool for the molecular characterization of clinically significant HBV strains.

The sequential occurrence of viral mutations in a liver transplant recipient re-infected with hepatitis B: hepatitis B immune globulin escape, famciclovir non-response, followed by lamivudine resistance resulting in graft loss

BACKGROUND/AIMS

The purpose of this study was to characterize the clinical, histological and virological events in an orthotopic liver transplant (OLT) recipient with recurrent hepatitis B infection who was initially managed with hepatitis B immune globulin (HBIg) and when viral recurrence occurred, with nucleoside analogue salvage therapy. The aims were to document the mutations occurring in the hepatitis B virus (HBV) polymerase gene as a consequence of HBIg escape, famciclovir non-response and subsequent lamivudine resistance.

METHODS

Throughout the follow-up of 796 days, the patient was seen at least at 4-week intervals. Clinical, biochemical and virological data were registered according to protocol. HBV DNA was quantified throughout the treatment period. The viral polymerase gene was sequenced from serum samples collected at representative time intervals. Consecutive liver biopsies were scored according to the modified Knodell classification.

RESULTS

Clinically, the patient was in excellent condition until the development of acute hepatitis during the lamivudine therapy period, 765 days post-OLT. Until this terminal event, serum transaminase activity was only 1-2 times the upper limit of normal with serum bilirubin and prothrombin time within the normal range. Subsequent liver biopsies showed chronic active hepatitis with no signs of fibrosis. The post-mortem biopsy showed severe acute hepatitis B with massive necrosis. The HBV polymerase gene was sequenced during HBIg, famciclovir and lamivudine treatment. One mutation I533L was detected during HBIg treatment. No amino acid changes were selected during famciclovir treatment. Three amino acid changes were selected while the patient was on lamivudine treatment, which include L533I, S559T and M550I.

CONCLUSIONS

We have documented HBV recurrence in a liver transplant recipient with the emergence of a multidrug resistant HBV which caused graft loss. The primary resistance to famciclovir in spite of therapeutic penciclovir levels may be as a result of a combination of the mutations found in the polymerase region. After 300 days of lamivudine treatment, a drug-resistant population emerged which was associated with a greater than three log increase in HBV DNA and contributed to loss of graft function. This is the first report of such an adverse clinical outcome due to the emergence of a mutant virus as a consequence of immunoprophylactic and antiviral therapy in a liver transplant recipient.

Taxonomic classification of hepatitis A virus

Sufficient data have accumulated to permit the ICTV Ad Hoc Study Group on the Taxonomy of Hepatitis Viruses to recognize hepatitis A virus as a picornavirus. Within the family Picornaviridae, hepatitis A virus closely resembles members of the genus Enterovirus.

Toll-like receptor expression in chronic hepatitis C: correlation with pro-inflammatory cytokine levels and liver injury

BACKGROUND/AIMS

Toll-like receptors (TLR's) are critical receptors that promote innate immune responses to pathogen-associated molecular patterns. Activation of TLR's leads to production of pro-inflammatory cytokines such as tumour necrosis factor (TNF)-alpha. This study investigates whether peripheral blood monocyte expression of TLR's is disturbed in patients with chronic hepatitis C and whether levels of expression of these molecules are significantly correlated with hepatitis C virus (HCV) genotype, viral load, hepatic necroinflammatory activity, histological stage and circulating TNF-alpha concentrations.

METHODS

In 18 non-cirrhotic patients with biopsy-proven, virologically-confirmed chronic hepatitis C and 32 controls, we measured expression of TLR2 and TLR4 on peripheral blood monocytes. HCV genotype, viral load, serum alanine aminotransferase (ALT) levels, histological stage of disease and circulating TNF-alpha and endotoxin levels were also determined.

RESULTS

Peripheral blood monocyte expression of TLR2 and TLR4 were significantly increased in patients with chronic hepatitis C compared to controls, irrespective of HCV genotype or histological stage of disease. Circulating levels of TNF-alpha were also significantly increased in patients with chronic hepatitis C. In both the overall study cohort and patients with chronic hepatitis C, monocyte expression of TLR2, but not of TLR4, correlated significantly with serum TNF-alpha levels. In patients with chronic hepatitis C, monocyte expression of TLR2, but not of TLR4, also correlated significantly with serum ALT levels. Expression of TLR's was not significantly correlated with viral load.

CONCLUSIONS

Up-regulation of peripheral blood monocyte expression of TLR2 and TLR4 occurs in patients with chronic hepatitis C. Increased monocyte expression of TLR2, but not of TLR4, correlates significantly with both increased circulating TNF-alpha levels and hepatic necroinflammatory activity in this disorder.