21 research outputs found

    Assessment of the COBAS Amplicor HBV Monitor Test for Quantitation of Serum Hepatitis B Virus DNA Levels

    No full text
    Treatment of patients with chronic hepatitis B virus (HBV) infections with potent antiviral therapy often results in dramatic reductions in the levels of viremia to very low levels. Monitoring of serum HBV DNA levels is a consistent method for the assessment of antiviral potency; however, widely used hybridization assays for the monitoring of HBV DNA levels have limited sensitivities and are not effective for the monitoring of patients whose serum HBV DNA levels have decreased to below approximately 700,000 HBV genomes/ml. The objective of the present study was to assess a PCR-based assay (the COBAS-AM assay) for quantitation of serum HBV DNA levels and to compare the results of the COBAS-AM assay with those of a solution hybridization assay with a radiolabeled probe. The precision and accuracy of the assay were determined with low-positive and high-positive controls consisting of a plasmid DNA molecule containing HBV-specific primer binding regions, and the sensitivity of the assay was determined by using serial dilutions of sera from subjects with chronic HBV infection. HBV DNA levels were quantitated in 1,695 serum samples from subjects with chronic HBV infection who were enrolled in clinical trials of lamivudine in North America or Asia. The COBAS-AM assay demonstrated high levels of inter- and intra-assay precision and accuracy, and the linear range of the COBAS-AM assay was greater than that of the solution hybridization assay. The assay is linear over a 3-log(10) range and is able to quantitate serum HBV DNA at levels 3 log(10) lower than those that can be detected by the solution hybridization assay. We found that the COBAS-AM assay is an accurate PCR-based assay for quantitation of serum HBV DNA levels in subjects with chronic HBV infection

    Kinetic Analysis of Wild-Type and YMDD Mutant Hepatitis B Virus Polymerases and Effects of Deoxyribonucleotide Concentrations on Polymerase Activity

    No full text
    Mutations in the YMDD motif of the hepatitis B virus (HBV) DNA polymerase result in reduced susceptibility of HBV to inhibition by lamivudine, at a cost in replication fitness. The mechanisms underlying the effects of YMDD mutations on replication fitness were investigated using both a cell-based viral replication system and an in vitro enzyme assay to examine wild-type (wt) and YMDD-mutant polymerases. We calculated the affinities of wt and YMDD-mutant polymerases for each natural deoxyribonucleoside triphosphate (dNTP) and determined the intracellular concentrations of each dNTP in HepG2 cells under conditions that support HBV replication. In addition, inhibition constants for lamivudine triphosphate were determined for wt and YMDD-mutant polymerases. Relative to wt HBV polymerase, each of the YMDD-mutant polymerases showed increased apparent K(m) values for the natural dNTP substrates, indicating decreased affinities for these substrates, as well as increased K(i) values for lamivudine triphosphate, indicating decreased affinity for the drug. The effect of the differences in apparent K(m) values between YMDD-mutant polymerase and wt HBV polymerase could be masked by high levels of dNTP substrates (>20 μM). However, assays using dNTP concentrations equivalent to those measured in HepG2 cells under physiological conditions showed decreased enzymatic activity of YMDD-mutant polymerases relative to wt polymerase. Therefore, the decrease in replication fitness of YMDD-mutant HBV strains results from the lower affinities (increased K(m) values) of the YMDD-mutant polymerases for the natural dNTP substrates and physiological intracellular concentrations of dNTPs that are limiting for the replication of YMDD-mutant HBV strains

    Lamivudine as Initial Treatment for Chronic Hepatitis B in the United States

    No full text
    Hepatitis B virus (HBV) infects more than 300 million people worldwide, contributing to debilitating illness and death. 1 Until recently, the only antiviral drug for the treatment of hepatitis B was interferon. 2 – 4 In preliminary studies of patients with chronic hepatitis B, lamivudine, an oral nucleoside analogue, 5 was well tolerated and suppressed serum levels of HBV DNA profoundly. 6 – 9 We therefore conducted a one-year study of the efficacy of lamivudine in patients with chronic hepatitis B. After our data on patients had been collected, Lai et al. 10 reported the results of a placebo-controlled study in which they found histologic, biochemical, and . . 

    Genome-wide Association Study Identifies Genetic Determinants of Urine PCA3 Levels in Men

    Get PDF
    Prostate cancer gene 3 (PCA3) is a non-coding gene specifically overexpressed in prostate cancer (PCa) that has great potential as a clinical biomarker for predicting prostate biopsy outcome. However, genetic determinants of PCA3 expression level remain unknown. To investigate the association between genetic variants and PCA3 mRNA level, a genome-wide association study was conducted in 1371 men of European descent in the REduction by DUtasteride of prostate Cancer Events trial. First-voided urine specimens containing prostate cells were obtained after digital rectal examination. The PROGENSA PCA3 assay was used to determine PCA3 score in the urinary samples. A linear regression model was used to detect the associations between (single nucleotide polymorphisms) SNPs and PCA3 score under an additive genetic model, adjusting for age and population stratification. Two SNPs, rs10993994 in β-microseminoprotein at 10q11.23 and rs10424878 in kallikrein-related peptidase 2 at 19q13.33, were associated with PCA3 score at genome-wide significance level (P = 1.22 x 10-9 and 1.06 x 10-8, respectively). Men carrying the rs10993994 “T” allele or rs10424878 “A” allele had higher PCA3 score compared with men carrying rs10993994 “C” allele or rs10424878 “G” allele (β = 1.25 and 1.24, respectively). This is the first comprehensive search for genetic determinants of PCA3 score. The novel loci identified may provide insight into the molecular mechanisms of PCA3 expression as a potential marker of PCa

    Extended treatment with lamivudine and adefovir dipivoxil in chronic hepatitis B patients with lamivudine resistance

    No full text
    PURPOSE: We and others have reported that adding adefovir dipivoxil (adefovir) to lamivudine results in virological and biochemical improvement in cases of lamivudine resistance. The current study assessed the efficacy and safety of combined therapy after 104 weeks of combined treatment and analyzed the frequency of persistent lamivudine resistant HBV. METHODS: A total of 78 patients with compensated CHB (Group A) were maintained on either adefovir 10 mg daily (n = 38) or placebo (n = 40) while continuing lamivudine. An additional 38 patients with decompensated cirrhosis or post liver transplantation (Group B) received lamivudine plus adefovir. The primary endpoint was HBV DNA response at year 2. RESULTS: At week 104 of therapy, a significantly greater proportion of patients in Group A on combination therapy (76%) had a decline in serum HBV DNA to ≤10(5) copies or >2 log(10) reduction from baseline compared to those receiving lamivudine alone (13%; p < 0.001). Fifty-two percent of Group A patients on combination treatment continued to have the M204V/I HBV mutation compared to 92% receiving lamivudine alone (p = 0.0013). Virologic response occurred less frequently in patients expressing persistent lamivudine resistant HBV. In Group B, 87% of patients had HBV DNA response at week 104 (median change from baseline of −5.84 log(10) copies/mL). CONCLUSIONS: The combination of lamivudine and adefovir for 2 years generally proved effective in lamivudine-resistant cases, but there was a persistently high rate of detection of lamivudine resistant mutants and impaired virologic response in compensated patients
    corecore