Real-time PCR assay using molecular beacon for quantitation of hepatitis B virus DNA

Abstract

Levels of hepatitis B virus (HBV) DNA in the blood serve as an important marker in monitoring the disease progression and treatment efficacy of chronic HBV infection. Several commercial assays are available for accurate measurement of HBV genomic DNA, but many of them are hampered by relatively low sensitivity and limited dynamic range. The aim of this study was to develop a sensitive and accurate assay for measuring HBV genomic DNA using real-time PCR with a molecular beacon (HBV beacon assay). The performance of this assay was validated by testing serial dilutions of the two EUROHEP HBV DNA standards (ad and ay subtypes) of known concentrations. The assay showed low intra-assay (<7%) and interassay (<5%) variations for both subtypes. Its dynamic range was found to be 10(1) to 10(7) copies per reaction (1.0 x 10(2) to 1.0 x 10(9) copies ml(-1)). The assay was further evaluated clinically using serum samples from 175 individuals with chronic hepatitis B. The HBV DNA level measured by this assay showed good correlation with that measured by the commercially available COBAS AMPLICOR HBV Monitor test (r = 0.901; P < 0.001). The higher sensitivity and broader dynamic range of this assay compared to the existing commercial assays will provide an ideal tool for monitoring disease progression and treatment efficacy in HBV-infected patients, in particular for those with low levels of HBV viremia.

FIG. 1.

Testing of HBV beacon assay with EUROHEP reference plasmas. Serial ninefold dilutions were made from the EUROHEP standards of subtypes ad and ay. Each sample was analyzed in duplicate in 10 runs. The mean concentration of HBV DNA measured by the HBV beacon assay was plotted against the expected HBV DNA concentration (r = 0.999; P < 0.001).

FIG. 2.

Correlation plot of log₁₀ HBV DNA values obtained with COBAS AMPLICOR HBV Monitor test and HBV beacon assay (r = 0.908; P < 0.001).