Clinical and virological characteristics of lamivudine resistance in chronic hepatitis B patients: A single center experience

Hepatitis B Management in the Middle East: A Narrative Review of Current Antiviral Treatments

Introduction: Chronic hepatitis B (CHB) is a significant public health issue worldwide, especially in the Middle East region. Around 8% to 20% of patients with CHB develop cirrhosis, which may progress to hepatocellular carcinoma. The significant morbidity and mortality associated with CHB denote the importance of high-quality treatment. Methods: We searched the PubMed, Medline, and Cochrane databases from inception to January 2024 to identify relevant studies. Search terms were generated using established treatment guidelines for CHB. We also manually searched the bibliographies of relevant literature to obtain additional papers. Results: In this narrative review, we evaluated the seven currently licensed antiviral therapies for chronic Hepatitis B treatment, including nucleos(t)ide analogs (NAs) and pegylated interferon-alpha (PEG-IFNα). NAs can be divided into two categories: high barrier to resistance and low barrier to resistance. Tenofovir disoproxil fumarate, tenofovir alafenamide, and entecavir are NAs with a high barrier to resistance. Telbivudine has shown promise in providing high efficacy with low viral resistance rates; however, it is not recommended because of insufficient evidence and lack of cost-effectiveness. Lamivudine and adefovir dipivoxil, despite being efficacious, have a low barrier to resistance, the primary reason they are no longer recommended. PEG-IFNα has high efficacy and can be completed in 48 weeks. It is not associated with resistance; however, it has been reported to have several systemic adverse effects. Conclusions: Current first-line NA treatments in the Middle East include entecavir, tenofovir disoproxil fumarate, and tenofovir alafenamide. These drugs are favored over other NAs because of their low rates of resistance. PEG-IFNα has superiority over NAs in inducing a more durable antiviral response and having a finite treatment duration. The main drawback of PEG-IFNα is an unfavorable safety profile.

Hepatitis B virus-related hepatocellular carcinoma in the era of antiviral therapy: The emerging role of non-viral risk factors

Hepatocellular carcinoma (HCC), one of the major malignant lethal tumours, is most prevalent in Asian patients with chronic hepatitis B virus (HBV) infection. Both viral and non-viral factors contribute to the development of HCC. It is established that viral factors associated with HBV DNA level, HBV genotype, designated gene mutation, HBV DNA integration, HBx protein, hepatitis B surface antigen (HBsAg), hepatitis B core-related antigen (HBcrAg) and HBV RNA are correlated with hepatocarcinogenesis. Before the introduction of antiviral therapy, viral factors once attracted more attention during the development of HCC. With the widespread use of antiviral therapy, predominantly nucleos(t)ide analogues (NAs), most patients with chronic hepatitis B (CHB) have achieved sustained viral control. The role of non-viral factors, especially modifiable factors, is anticipated to be reinforced in the future. Herein, we reviewed the modifiable non-viral risk factors of HBV-related HCC, in the hope of providing substantial evidence for further development of novel precautionary measures for HCC. In addition, the therapeutic interventions for reducing the risk of HCC, like potential conventional pharmaceutical interventions and lifestyle modification are also discussed in this review. Future studies that would explore the specific mechanism of HBV-related HCC development in patients with satisfactory viral control and related precision treatment are warranted.

Antiviral efficacy of entecavir for hepatitis B virus rtA181V/T mutants

Background

The amino acid substitution at position 181 of the Hepatitis B virus (HBV) polymerase is a multi-drug resistance affecting both the L-nucleoside and acyclic phosphonate nucleotide groups. Data is limited on the efficacy of entecavir (ETV) rescuing chronic hepatitis B (CHB) patients with rtA181T/V mutation.

Methods

Thirty-one patients with rtA181T/V mutation and 25 patients with rtA181T/V and rtN236T mutation were enrolled. Virological, serological and biochemical outcomes of ETV rescue therapy over 12 months in CHB patients with rtA181T/V mutation strains were investigated. All patients were treated with ETV 0.5 mg/day for 12 months and scheduled follow-up every 3 months. Patients’ characteristics, laboratory tests results and clinical outcomes were collected and compared.

Results

After emergence of rtA181T/V mutant, serum HBV DNA levels increased over 4 log10 IU/mL, but the total bilirubin, alanine aminotransferase (ALT) levels raised moderately. No significant difference in baseline characteristics was observed between the rtA181T/V group and rtA181T/V + rtN236T group. After 12 months rescue therapy, total 85.7% (48/56) patients achieved HBV DNA undetectable. No significant difference in the mean reduction of serum HBV DNA and biochemical response was observed between both groups (3.59 ± 1.85 vs. 3.76 ± 2.15 log10 IU/ml; P = 0.756 and 90.3 vs. 80.0%; P = 0.272, respectively). The mean HBV DNA reduction, HBsAg and ALT levels were also similar between different rtA181T/sW172 mutations (P > 0.05). HBV DNA level is the only predictor of 12 months antiviral outcomes (odds ratio 6.723, P = 0.022).

Conclusions

The results of the present study suggested that ETV is efficient in rescuing rtA181T/V mutation CHB patients. HBV DNA level could predict viral clearance at the 12^th month.

Factors associated with serum hepatitis B surface antigen levels and its on-treatment changes in patients under lamivudine therapy

BACKGROUND

We aimed to investigate factors associated with serum hepatitis B surface antigen (HBsAg) levels and its kinetics under lamivudine treatment in chronic hepatitis B patients.

METHODS

HBsAg levels were measured with the Architect HBsAg assay (Abbott laboratories, Abbott Park, IL, USA) in genotype B (HBV/B) or C (HBV/C) patients (n=218). Early HBsAg kinetics in 86 hepatitis B e antigen (HBeAg)-positive patients and long-term HBsAg changes in 45 patients with rapid and sustained viral suppression were further analysed.

RESULTS

Mean HBsAg levels were higher in male (n=181) than in female (n=37) patients (3.59 versus 3.23 log(10) IU/ml; P=0.036), and higher in 121 HBV/B than in 97 HBV/C patients (3.68 versus 3.34 log(10) IU/ml; P=0.006). In addition to HBV DNA loads (P<0.001), male gender (P=0.012) and HBV/B infection (P=0.035) were independently associated with higher HBsAg levels in antiviral-naive patients. HBsAg increases (0.00-0.87 log(10)) were found in 28/86 patients who obtained viral suppression under 12 weeks of lamivudine therapy. Higher baseline HBsAg levels (P=0.046), HBV/B infection (P=0.007) and faster HBV DNA declines (P=0.006) independently contributed to greater HBsAg decreases under 12 weeks treatment. An apparent dissociation between HBsAg and HBV DNA changes were found in 14/45 patients with rapid and sustained viral suppression, who had low baseline HBsAg levels and predominant HBV/C infection.

CONCLUSIONS

HBV/B and male gender were associated with higher HBsAg levels in antiviral-naive patients. Higher baseline HBsAg levels and HBV/B infection contributed to greater early HBsAg declines in HBeAg-positive patients, and might correlate with discordance between HBsAg and HBeAg or HBV DNA under long-term lamivudine treatment.

Lamivudine resistance mutations in patients infected with hepatitis B virus genotype D

AIM: To determine the distribution of viral genotypes for primary or acquired lamivudine resistance.

METHODS: A total of 283 patients with chronic hepatitis B virus (HBV) infection (245 patients with chronic hepatitis B and 38 inactive hepatitis B surface antigen carriers) were included in the study. The HBV genotype was determined by using quantitative real-time polymerase chain reaction and sequence analysis, and tyrosine-methionine-aspartate-aspartate (YMDD) motif mutations were determined using the reverse transcriptase hybridization method.

RESULTS: Lamivudine resistance was determined in a total of 25 (10.7%) chronic hepatitis B patients. Eight subjects (4%) had primary resistance to lamivudine, and 17 (53.1%) had secondary resistance to lamivudine. Genotype D, which was isolated from 267 of the patients with chronic HBV infection, was the dominant genotype in Turkey.

CONCLUSION: Identification of YMDD motif mutations should have a positive impact on the selection of proper antiviral medication for patients, even for those who are nucleoside naïve.

Clinical and virological characteristics of chronic hepatitis B with concurrent hepatitis B E antigen and antibody detection

The concurrent detection of hepatitis B e antigen (HBeAg) and its corresponding antibody (anti-HBe) in patients with chronic hepatitis B virus (HBV) infection is well established but the clinical features remain poorly understood. Demographic information, clinical and laboratory data were collected from 1624 consecutive inpatient records of patients with chronic hepatitis B. Viral genotype, basic core promoter and precore mutations were determined by direct sequencing. In vitro HBeAg and anti-HBe binding experiments were conducted with three pairs of HBeAg-positive and anti-HBe-positive serum samples, which were mixed at variable ratios and incubated at 37°C for 3-24h. Of the 1624 chronic patients, 169 (10.4%) had concurrent HBeAg and anti-HBe positivity, and this was associated with intermediate age and HBV-DNA load, higher alanine aminotransferase level and more pronounced liver damage compared with HBeAg-positive or anti-HBe-positive patients alone. HBeAg and anti-HBe titres (median and interquartile range, S/CO) in the concurrent positive group were 4.2 (1.8-9.6) and 0.54 (0.27-0.72), which were closer to their respective cut-off values than those of HBeAg-positive or anti-HBe-positive groups alone. For the cases successfully sequenced, 110/134 (82.1%) harboured T1762/A1764 or/and A1896 mutants. The binding experiments showed that HBeAg and anti-HBe could be concurrently observed provided an optimal ratio (HBeAg to anti-HBe) was chosen. In antiviral treatment-naive patients, concurrence of HBeAg and anti-HBe was not uncommon, and such patients had profound liver disease. An optimal ratio between HBeAg and anti-HBe led to their concurrent detection when sera were tested by sensitive assays.

Long-term effects of lamivudine treatment in Japanese chronic hepatitis B patients

AIM: To analyze the association between the emergence of tyrosine-methionine-asparatate-asparatate (YMDD) mutants (reverse transcription; rtM204I/V) and deterioration of liver function during long-term lamivudine treatment of Japanese patients with chronic hepatitis B virus (HBV) infection.

METHODS: The data of 61 consecutive Japanese patients with chronic hepatitis B who underwent continuous lamivudine treatment for more than 24 mo and had a virological response were analyzed. Analysis of YMDD mutants was done by real-time polymerase chain reaction with LightCycler probe hybridization assay for up to 90 mo (mean, 50.8 mo; range, 24-90 mo).

RESULTS: A mixed mutant-type (YMDD + tyrosine-isoleucine-asparatate-asparatate: YIDD or tyrosine-valine-asparatate-asparatate: YVDD) or a mutant-type (YIDD or YVDD) were found in 57.4% of 61 patients at 1 year, 78.7% of 61 patients at 2 years, 79.6% of 49 patients at 3 years, 70.5% of 34 patients at 4 years, 68.4% of 19 patients at 5 years, 57.1% of 14 patients at 6 years, and 33.3% of 6 patients at 7 years. Of the 61 patients, 56 (92%) had mixed mutant- or a mutant-type. Only 5 (8%) had no mutants at each observation point. Virological breakthrough was found in 26 (46.4%) of 56 patients with YMDD mutants, 20 of whom had a hepatitis flare-up: the remaining 30 (53.6%) had neither a virological breakthrough nor a flare-up. All 20 patients who developed a hepatitis flare-up had a biochemical and virological response after adefovir was added to the lamivudine treatment.

CONCLUSION: Our results suggest that it is possible to continue lamivudine treatment, even after the emergence of YMDD mutants, up to the time that the patients develop a hepatitis flare-up.

Hepatitis B virus genotype B has an earlier emergence of lamivudine resistance than genotype C

BACKGROUND

Hepatitis B virus (HBV) genotype B and C seem not to affect the therapeutic response to lamivudine (3TC). Whether a given genotype has an earlier emergence of 3TC resistance remains unclear. We thus conducted this study to elucidate the association of HBV genotype with the emergence of 3TC-resistant strains in Taiwanese patients.

METHODS

Forty chronic hepatitis B patients who developed resistance after 3TC therapy were retrospectively enrolled. HBV genotype, serum alanine aminotransferase (ALT) and HBV DNA levels were determined at baseline. The presence of 3TC-resistant mutations was confirmed by direct sequencing whenever biochemical breakthrough developed.

RESULTS

The distribution of HBV genotype B and C in 40 patients receiving 3TC therapy were 60% and 40%, respectively. The mean interval to detect 3TC-resistant strain was 19.6 +/-1.7 months. By using multivariate analysis, HBV genotype B and higher pre-treatment HBV DNA level were independently associated with earlier detection of 3TC-resistant strains. In addition, genotype B was significantly associated with development of 3TC resistance within the first 12 months of 3TC therapy compared with genotype C (odds ratio 8.27; P=0.004).

CONCLUSIONS

Compared with HBV genotype C, genotype B appears to have an earlier biochemical resistance to 3TC than genotype C. Therefore, more frequent monitoring of viral load or genotypical resistance might be needed for patients with HBV genotype B infection receiving 3TC therapy, especially during the first year.

Lamivudine and adefovir resistance in children and young adults with chronic hepatitis B

OBJECTIVE

Long-term lamivudine (LAM) and adefovir (ADV) treatment has been found to induce the emergence of drug-resistant hepatitis B virus (HBV) in a significant number of patients with chronic hepatitis B (CHB) infection. The aim of our study was to evaluate the LAM and ADV mutations detected in our patient group.

MATERIALS AND METHODS

Twenty-four patients diagnosed with CHB were enrolled in this study. The patient group consisted of those who had received 6 months of treatment with interferon-alpha and who did not response to this therapy. Patients were evaluated based on virologic and serologic response to therapy, and were classified as responders or non-responders. The treatment of non-responders continued with LAM (3mg/kg/d, maximum 100mg/d). Due to a lack of response to treatment, ADV (10mg/g) was added to the treatment regimen of eight young adult patients. The mutations associated with HBV drug resistance were investigated using reverse hybridization methods and PCR.

RESULTS

The mutation studies indicated that 14 (58.4%) of the patients had resistance. Three patients developed ADV-associated mutations (A181T), one after 18 months of ADV; the other two had undergone 18 and 36 months of LAM therapy without ADV exposure. Although the average LAM treatment period of the patients with LAM resistance was longer than for those in whom no resistance was detected, no statistically significant difference was found.

CONCLUSIONS

HBV treatment with nucleoside analogues results in the development of mutant strains, leading to drug resistance. Therefore genotypic resistance testing is important in planning and monitoring HBV treatment.

GTPase activity is not essential for the interferon-inducible MxA protein to inhibit the replication of hepatitis B virus

Multiple studies have established that GTPase activity is critical for MxA to act against RNA viruses. Recently, it was shown that MxA can also restrict the replication of hepatitis B virus (HBV), a DNA virus, but the requirements for GTPase activity in inhibition of HBV by MxA remain unknown. Here, we report that GTPase-defective mutants (K83A, T103A, and L612K) can downregulate extracellular HBsAg and HBeAg and reduce the expression of extra- and intracellular HBV DNA in HepG2 cells to levels similar to that achieved by wild-type MxA. Furthermore, TMxA and T103, two nuclear forms of wild-type MxA and a GTPase-defective mutant (T103A) could only slightly decrease the expression of extra- and intracellular HBV DNA in HepG2 cells. In conclusion, GTPase activity is not essential for MxA protein to inhibit HBV replication, and MxA may have only a minimal effect on the replicative cycle of HBV in the nucleus.

Construction and expression of eukaryotic plasmids containing lamivudine-resistant or wild-type strains of Hepatitis B Virus genotype C

AIM: To construct eukaryotic expression plasmids of full-length Hepatitis B Virus (HBV) genotype C genome, which contain lamivudine-resistant mutants (YIDD, YVDD) or wild-type strain (YMDD), and to observe the expression of HBV DNA and antigens [hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg)] of the recombinant plasmids in HepG2 cells.

METHODS: Three HBV full-length genomes were amplified from the plasmids pMD18T-HBV/YIDD, pMD18T-HBV/YVDD and pMD18T-HBV/YMDD, using PCR. Three recombinant plasmids were generated by inserting each of the PCR products into the eukaryotic expression vector pcDNA3.1 (+), between the EcoRI and HindIII sites. After being characterized by restriction endonuclease digestion, and DNA sequence analysis, the recombinant plasmids were transfected into HepG2 cells. At 48 and 72 h post-transfection, the levels of intracellular viral DNA replication were detected by real-time PCR, and the expression of HBsAg and HBeAg in the cell culture supernatant was determined by ELISA.

RESULTS: Restriction endonuclease digestion and DNA sequence analysis confirmed that the three recombinant plasmids were correctly constructed. After transfecting the plasmids into HepG2 cells, high levels of intracellular viral DNA replication were observed, and HBsAg and HBeAg were secreted into the cell culture supernatant.

CONCLUSION: Eukaryotic expression plasmids pcDNA3.1 (+)-HBV/YIDD, pcDNA3.1 (+)-HBV/YVDD or pcDNA3.1 (+)-HBV/YMDD, which contained HBV genotype C full-length genome, were successfully constructed. After transfection into HepG2 cells, the recombinant plasmids efficiently expressed HBV DNA, HBsAg and HBeAg. Our results provide an experimental basis for the further study of HBV lamivudine-resistant mutants.

Comparison of ligase detection reaction and real-time PCR for detection of low abundant YMDD mutants in patients with chronic hepatitis B

AIM: To compare the ligase detection reaction (LDR) and real-time PCR for detection of low abundant YMDD mutants in patients with chronic hepatitis B infection.

METHODS: Mixtures of plasmids and serum samples from 52 chronic hepatitis B patients with low abundant lamivudine-resistant mutations were tested with LDR and real-time PCR. Time required and reagent cost for both assays were evaluated.

RESULTS: Real-time PCR detected 100, 50, 10, 1 and 0.1% of YIDD plasmid, whereas LDR detected 100, 50, 10, 1, 0.1, and 0.01% of YIDD plasmid, in mixtures with YMDD plasmid of 10⁶ copies/mL. Among the 52 clinical serum samples, completely concordant results were obtained for all samples by both assays, and 39 YIDD, 9 YVDD, and 4 YIDD/YVDD were detected. Cost and time required for LDR and real-time PCR are 60/80 CNY (8/10.7 US dollars) and 4.5/2.5 h, respectively.

CONCLUSION: LDR and real-time PCR are both sensitive and inexpensive methods for monitoring low abundant YMDD mutants during lamivudine therapy in patients with chronic hepatitis B. LDR is more sensitive and less expensive, while real-time PCR is more rapid.

The emergence of YMDD mutants precedes biochemical flare by 19 weeks in lamivudine-treated chronic hepatitis B patients: an opportunity for therapy reevaluation

Given the loss of therapeutic efficacy associated with the development of resistance to lamivudine (LMV) and the availability of new alternative treatments for chronic hepatitis B patients, early detection of viral genotypic resistance could allow the clinician to consider therapy modification before viral breakthrough and biochemical relapse occur. To this end, 28 LMV-treated patients (44 +/- 12 years; 24 men), on their first therapy schedule, were monitored monthly at four Brazilian centers for the emergence of drug resistance using the reverse hybridization-based INNO-LiPA HBV DR assay and occasionally sequencing (two cases). Positive viral responses (HBV DNA clearance) after 6, 12, and 18 months of therapy were achieved by 57, 68, and 53% of patients, while biochemical responses (serum alanine aminotransferase normalization) were observed in 82, 82, and 53% of cases. All viral breakthrough cases (N = 8) were related to the emergence of YMDD variants observed in 7, 21, and 35% of patients at 6, 12, and 18 months, respectively. The emergence of these variants was not associated with viral genotype, HBeAg expression status, or pretreatment serum alanine aminotransferase levels. The detection of resistance-associated mutations was observed before the corresponding biochemical flare (41 +/- 14 and 60 +/- 15 weeks) in the same individuals. Then, if highly sensitive LMV drug resistance testing is carried out at frequent and regular intervals, the relatively long period (19 +/- 2 weeks) between the emergence of viral resistance and the onset of biochemical relapse can provide clinicians with ample time to re-evaluate drug therapy.

Differences of YMDD mutational patterns, precore/core promoter mutations, serum HBV DNA levels in lamivudine-resistant hepatitis B genotypes B and C

The aims of this study were to investigate the viral differences among lamivudine-resistant hepatitis B virus (HBV) genotypes B and C in vivo. Fifty-three patients carrying lamivudine-resistant HBV were enrolled in this study. HBV genotypes, Levels of alanine aminotransferase (ALT), HBV DNA levels were monitored during therapy. The polymerase and precore/core promoter genes were amplified by polymerase chain reaction and their products were sequenced directly. Among 53 patients resistant HBV genotypes B and C accounted for 41.50% and 58.50%, respectively. The occurrence of reverse transcriptase rt204I mutants was lower in genotype B (36.36%) than that in genotype C (87.10%), whereas rt204V mutants was higher in genotype B (63.64%) than that in genotype C (12.90%). The occurrence of precore mutation (nt1896A) was higher in genotype B (77.27%) than that in genotype C (32.26%). Serum HBV DNA levels after emergence of lamivudine resistance were higher in genotype C (7.71 +/- 0.80 Log copies/mL) compared with genotype B (6.97 +/- 0.77 Log copies/mL). Multivariate analysis identified pretreatment HBV DNA levels, HBeAg status and HBV genotype as independent factors associated with a shorter time to lamivudine resistance(P = 0.035, P = 0.006 and P = 0.001, respectively). Multivariate analysis showed that HBV genotype (P = 0.004) and pretreatment ALT levels (P = 0.01) was independently associated with YMDD mutational patterns. The results showed that the YMDD mutational patterns, precore mutation and serum HBV DNA levels differ between lamivudine-resistant HBV genotypes B and C in vivo. It is valuable for treatment of lamivudine-resistant HBV in clinic.

Clinical outcomes of chronic hepatitis B patients with persistently detectable serum hepatitis B virus DNA during lamivudine therapy

BACKGROUND AND AIM

A small proportion of chronic hepatitis B patients have persistently detectable serum hepatitis B virus (HBV) DNA despite lamivudine therapy. The incidence and clinical outcomes of patients who persistently have detectable serum HBV-DNA during lamivudine therapy was investigated.

METHOD

We enrolled 221 chronic hepatitis B patients who underwent lamivudine therapy for more than 6 months. Among them, 180 were HBeAg positive. Serum HBV-DNA, HBeAg, anti-HBe and alanine aminotransferase (ALT) levels were serially monitored. The study groups were defined, using a hybridization assay, as patients with reductions in serum HBV-DNA below the detectable level (group I) or patients with persistently detectable serum HBV-DNA (group II) during the initial 6 months of lamivudine therapy.

RESULTS

The incidence of patients who had persistently detectable HBV-DNA was 7.7%. After the first year, the rates of viral breakthrough, HBeAg loss and serum ALT normalization of group I versus group II were 21% versus 63%, 38% versus 0%, and 71% versus 28%, respectively (P < 0.001). The log(10) reduction of serum HBV-DNA at 6 months was -4.58 log(10) for group I and -1.97 log(10) for group II (P < 0.001, bDNA assay). There were no pretreatment lamivudine-resistant mutants in group II.

CONCLUSION

Lamivudine had little effect on serum HBV-DNA suppression, viral breakthrough suppression and rate of HBeAg loss and ALT normalization in chronic hepatitis B patients with persistently detectable serum HBV-DNA during the initial 6 months of therapy. Early termination of lamivudine therapy is advocated for these patients.

Hepatitis B virus genotypes and subgenotypes in China

Eight Hepatitis B virus (HBV) genotypes (A to H) have been identified based on an intergenotype divergence of 8% or more in the entire nucleotide sequence. Subgenotypes have also been identified in different HBV genotypes. As a highly endemic area for HBV infection, the prevalence of chronic HBV infection in China is between 8 and 20% of the general population. Genotypes B and C were identified as the most common HBV strains and account for approximately 95% of Chinese patients. Further study confirmed all genotype B strains belong to subgenotype Ba. Two of genotype C subgenotypes, C1 (Cs) and C2 (Ce), were found in China and they showed different geographic distributions. Genotype A was very rarely found, while genotypes E, F, G and H have not beenreported until now. Two types of HBV C/Drecombinant viruses have been identified in west China and distinct geographic and ethnic distributions were observed. Significant differences were observed (P < 0.001) in the prevalence of A1896 and T1762/A1764 mutations among HBV Ba, C1 and C2 subgenotypes in Chinese patients. Accumulating evidence showed the response rate to antiviral therapy in Chinese patients is higher in genotype B than genotype C patients on interferon treatment, but no difference was observed on nucleoside/nucleotide analog treatment.

Future prospectives for the management of chronic hepatitis B

Chronic hepatitis B virus infection affects about 400 million people around the globe and causes approximately one million deaths a year. Since the discovery of interferon-α as a therapeutic option the treatment of hepatitis B has evolved fast and management has become increasingly complicated. The amount of viral replication reflected in the viral load (HBV-DNA) plays an important role in the development of cirrhosis and hepatocellular carcinoma. The current treatment modalities for chronic hepatitis B are immunomodulatory (interferons) and antiviral suppressants (nucleoside and nucleotide analogues) all with their own advantages and limitations. An overview of the treatment efficacy for both immunomodulatory as antiviral compounds is provided in order to provide the clinician insight into the factors influencing treatment outcome. With nucleoside or nucleotide analogues suppression of viral replication by 5-7 log₁₀ is feasible, but not all patients respond to therapy. Known factors influencing treatment outcome are viral load, ALT levels and compliance. Many other factors which might influence treatment are scarcely investigated. Identifying the factors associated with response might result in stopping rules, so treatment could be adapted in an early stage to provide adequate treatment and avoid the development of resistance. The efficacy of compounds for the treatment of mutant virus and the cross-resistance is largely unknown. However, genotypic and phenotypic testing as well as small clinical trials provided some data on efficacy in this population. Discontinuation of nucleoside or nucleotide analogues frequently results in viral relapse; however, some patients have a sustained response. Data on the risk factors for relapse are necessary in order to determine when treatment can be discontinued safely. In conclusion: chronic hepatitis B has become a treatable disease; however, much research is needed to tailor therapy to an individual patient, to predict the sustainability of response and determine the best treatment for those failing treatment.

Serum HBV RNA is a predictor of early emergence of the YMDD mutant in patients treated with lamivudine

Lamivudine (LAM) is a nucleoside analogue widely used for the treatment of chronic hepatitis B virus (HBV) infection. Emergence of resistant strains with amino acid substitutions in the tyrosine-methionine-aspartate-aspartate (YMDD) motif of reverse transcriptase is a serious problem in patients on LAM therapy. The amount of covalently closed circular DNA in the serum is reported to be higher in patients who develop YMDD mutants than in those without mutants. However, there is no useful serum marker that can predict early emergence of mutants during LAM therapy. Analysis of patients who were treated with entecavir (n=7) and LAM (n=36) showed some patients had high serum levels of HBV RNA. Median serum levels of HBV RNA were significantly higher in patients in whom the YMDD mutant had emerged within 1 year (n=6, 1.688 log copies/ml) than in those in whom the YMDD mutant emerged more than 1 year after treatment (n=12, 0.456 log copies/ml, P=0.0125) or in whom the YMDD mutant never emerged (n=18, 0.688 log copies/ml, P=0.039). Our results suggest that HBV RNA is a valuable predictor of early occurrence of viral mutation during LAM therapy.

Comparison of amplicon-sequencing, pyrosequencing and real-time PCR for detection of YMDD mutants in patients with chronic hepatitis B

AIM: To compare the sequencing of PCR products, pyrosequencing, and real-time PCR for detection of Tyrosine-methionine-aspartate-aspartate (YMDD) mutants in patients with chronic hepatitis B.

METHODS: Mixtures of plasmids and serum samples from 69 chronic hepatitis B patients treated with lamivudine were tested for YMDD mutations by sequencing of PCR products, pyrosequencing, and real-time PCR, respectively. Time required and reagent costs of the three assays were evaluated.

RESULTS: Real-time PCR detected 100%, 50%, 10%, 1% and 0.1% of YVDD plasmid in mixtures with 10⁶ copies/mL of YMDD plasmid, whereas sequencing and pyrosequencing only detected 100% and 50% of YVDD plasmid in aliquots of the corresponding mixtures. Completely concordant results were obtained from 60 (87%) out of the 69 clinical serum samples by the three assays. Mutants were detected by real-time PCR in less than 20% of the total virus population, but no mutant was detected by sequencing and pyrosequencing. In addition, real-time PCR required less time and was more cost-effective than the other two assays. However, throughput of pyrosequencing was the highest.

CONCLUSION: Among the three assays compared, real-time PCR is the most sensitive, cost-effective, and time saving for monitoring YMDD mutants in patients with chronic hepatitis B on lamivudine therapy.

Response to long-term lamivudine treatment in patients infected with hepatitis B virus genotypes A, B, and C

Response to lamivudine treatment longer than 1 year was compared in 15 patients persistently infected with hepatitis B virus (HBV) genotype A, 38 with genotype B, and 449 with genotype C. Patients with genotype A were younger (median age 37 [range 24-49] vs. 47 [24-67] or 44 [18-73], P = 0.015), possessed hepatitis B e antigen (HBeAg) more frequently (73% vs. 21% or 56%, P < 0.001) and HBV DNA in higher levels (8.6 [6.1-8.7] vs. 6.5 [<3.7-8.7] or 6.5 [<3.7-8.7] log genome equivalents (LGE)/ml, P = 0.024) than those with genotype B or C. During lamivudine, YMDD mutants (89% vs. 53% or 42%, P = 0.0001) and breakthrough hepatitis developed more often (47% vs. 21% or 29%, P = 0.023) in patients with genotype A than B or C. YMDD mutants elicited more frequently in patients with genotype A than B or C who were positive (82% [9/11] vs. 25% [2/8] or 48% [117/245], P = 0.037) or negative for HBeAg (75% [3/4] vs. 30% [9/30] or 33% [68/204], P = 0.003). HBeAg (hazard ratio 2.1 [95% confidence interval 1.53-2.92], P < 0.001) and genotype A (2.78 [1.08-7.12], P = 0.034) enhanced the emergence of YMDD mutants by the Cox proportional hazard model. The risk for breakthrough hepatitis was increased by the baseline alanine aminotransferase level <500 IU/L (2.56 [1.82-5.50], P = 0.018), HBeAg (2.11 [1.40-3.16], P < 0.001), cirrhosis (1.92 [1.24-2.97], P = 0.004) and HBV DNA > or =8.0 LGE/ml (1.57 [1.04-2.36], P = 0.03); it was influenced by genotypes only in patients with HBeAg. In conclusion, HBV genotypes help in predicting response to long-term lamivudine treatment and development of YMDD mutants in patients with chronic hepatitis B.

Detection of rtN236T and rtA181V/T mutations associated with resistance to adefovir dipivoxil in samples from patients with chronic hepatitis B virus infection by the INNO-LiPA HBV DR line probe assay (version 2)

The nucleotide analog adefovir dipivoxil (ADV) is an effective antiviral treatment for chronic hepatitis B virus (HBV) infection, with resistance to ADV estimated to occur less frequently than resistance to lamivudine treatment. The detection of ADV resistance mutations is necessary during therapy to monitor and anticipate possible treatment failure. The INNO-LiPA HBV DR v2 (LiPA; Innogenetics, Ghent, Belgium) is a DNA hybridization line probe assay for the detection of HBV polymerase mutations associated with resistance to lamivudine and ADV. Evaluation of this assay to detect ADV resistance mutations was performed by analyzing 38 patients treated with ADV. Serial samples taken at 6-month intervals during treatment were available for most patients. A total of 124 samples were analyzed by both LiPA and sequencing. By LiPA analysis, 12 patients (31.5%) were found to have mutations associated with resistance to ADV (rtA181V/T and/or rtN236T). This contrasted with sequence analysis, which found nine patients (24%) with either or both mutations. Twice as many samples were rtN236T positive by LiPA (18 of 124) compared to sequence analysis (9 of 124). LiPA detected the rtN236T mutation at least 6 months earlier than its detection by sequencing in patients for whom consecutive serum samples were available. Although less sensitive, sequencing has the advantage of providing information on other polymerase mutations not represented on LiPA strips. The INNO-LiPA HBV DR v2 assay is a very sensitive and specific assay for the detection of the rtN236T mutation associated with resistance to ADV.

Early detection and quantification of lamivudine-resistant hepatitis B virus mutants by fluorescent biprobe hybridization assay in lamivudine-treated patients

BACKGROUND

Long-term lamivudine treatment induces the emergence of lamivudine-resistant hepatitis B virus (HBV). The objective of this study was to develop a fluorescent biprobe hybridization (FBH) assay for the detection and quantification of HBV mutants in the clinical course of lamivudine-treated patients and to evaluate its clinical usefulness.

METHODS

We developed an FBH assay to detect mutations in the HBV DNA polymerase gene. The assay's detection sensitivity was determined using a dilution series of wild-type/mutant plasmid DNA. Blood samples obtained from 27 lamivudine-treated patients were analyzed.

RESULTS

Mutant DNA levels as low as 10% of total HBV DNA were detected (sensitivity = 100%, specificity = 80%). HBV mutants were detected in five of the 27 patients during an average follow-up of 20 months after lamivudine administration. In one of the five patients, the YIDD mutant was detected at the initiation of lamivudine treatment, while the remaining four patients were identified as having YIDD mutants within 3 months after beginning lamivudine administration. Of the five patients with an HBV mutant, four developed breakthrough hepatitis more than 10 months after the detection of HBV mutants, following the reappearance or a re-increase of HBV DNA, characterized by a predominance of the mutant. The YIDD mutant was detected in one patient, even when the titer of the serum HBV DNA was below the detection limit of commercially available quantitative polymerase chain reaction.

CONCLUSIONS

The FBH assay is an efficient method for detecting and quantifying HBV mutants, as early as 3 months after lamivudine administration.

Clinical evaluation of oligonucleotide microarrays for the detection of HBV mutants associated with lamivudine resistance

OBJECTIVES

Long-term lamivudine administration in hepatitis B virus (HBV)-infected patients induces the emergence of HBV mutants with lamivudine resistance. The aim of the present study was to evaluate the clinical application of an oligonucleotide microarray in detecting HBV mutants associated with lamivudine resistance.

METHODS

947 HBV DNA-positive sera from: 388 patients receiving lamivudine treatment, 559 chronic hepatitis B patients not receiving lamivudine treatment, and 359 from HBV DNA-negative controls, were assayed for HBV mutations using the oligonucleotide microarray. Furthermore, follow-up studies were performed using 255 clinical samples from 51 patients treated with lamivudine at various periods. The results were compared with sequencing and real-time polymerase chain reaction (PCR).

RESULTS

The HBV DNA polymerase Tyr-Met-Asp-Asp motif (YMDD) mutation was detected in all 388 samples containing lamivudine-resistant mutations identified by microarray. For the codons rt180, rt204 and rt207, the agreements between the microarray and sequencing data are 96.6, 98.5 and 100%, respectively. Two previously unreported mutants were also found in those samples. In the 947 samples collected from different patients, which were detected positive for HBV DNA by quantitative PCR, all but three weak-positive samples were positive by the microarray, demonstrating an agreement of 99.7%. In all the positive samples, mutations could be detected in the relevant loci of HBV DNA polymerase with lamivudine resistance. All of the 359 HBsAg-negative samples were shown to be negative for HBV DNA using the microarray method. Follow-up detection of the clinical samples from 51 patients treated with lamivudine demonstrated that the microarray method was able to detect mutations in mixed viruses that were infecting prior to sequencing.

CONCLUSION

The oligonucleotide microarray can be conveniently utilized to detect mutant HBV in clinical serum samples.

Genotypic resistance to lamivudine among hepatitis B virus isolates in Mexico

BACKGROUND

Drug resistance of hepatitis B virus (HBV) is an increasing clinical problem. Resistance to lamivudine in HBV isolates in Mexico has been poorly explored.

OBJECTIVES

To characterize the mutation patterns associated with genotypic resistance to lamivudine and their prevalence among HBV isolates in Mexico.

MATERIAL AND METHODS

Thirty-nine Mexican HBV isolates were analysed by PCR and line probe assay for detection of genetic variants in the polymerase open reading frame domains B and C (INNO-LiPA HBV DR; INNOGENETICS N. V., Ghent, Belgium). This assay detects wild-type and mutations at codons 180, 204 and 207 of the HBV polymerase gene, and at codon positions 171, 172, 195, 196, 198 and 199 of the HBV surface antigen (HBsAg). HBV isolates were obtained from HBsAg-positive serum samples of 15 chronic hepatitis patients, two haemodialysis patients with chronic HBV carriage, 20 men found positive for HBsAg when seeking HIV testing and two AIDS patients with chronic HBV infection. None of the participants had received antiviral therapy.

RESULTS

Overall, HBV wild-type was found in 37 (94.9%) out of the 39 isolates studied. Two (5.1%) out of the 39 isolates showed mixed wild-type and mutant populations. These mutations occurred in isolates from one hepatitis patient and one haemodialysis patient. The isolate from the hepatitis patient showed a double mutation at codon positions 180 (L180M) and 204 (M204V), thus a 2.6% prevalence of genotypic resistance to lamivudine was found. The isolate from the haemodialysis patient showed a single mutation at codon position 180 (L180M). The two HBV mutant isolates were further analysed for genotype and both isolates were genotype H.

CONCLUSIONS

HBV genotypic resistance to lamivudine exists in Mexican isolates. The results highlight the importance of testing for HBV resistance before treatment and have implications for a more rational use of drugs.