Quantitative detection of hepatitis B virus DNA in human sera by branched-DNA signal amplification

Clinical evaluation of a new enzyme immunoassay for hepatitis B virus core-related antigen; a marker distinct from viral DNA for monitoring lamivudine treatment

We aimed to assess the clinical performance of a newly developed chemiluminescence enzyme immunoassay (CLEIA) for the detection of hepatitis B virus (HBV) core-related antigen (HBcrAg) in patients with chronic HBV infection. A total of 82 patients with chronic HBV infection and 167 HBV-negative controls were studied. HBcrAg was measured by CLEIA with monoclonal antibodies to hepatitis B e antigen (HBeAg) and hepatitis B core antigen (HBcAg), and HBV DNA was measured by transcription-mediated amplification assay (TMA) and in-house real-time detection polymerase chain reaction (RTD-PCR). The HBcrAg assay detected viremia in 189 of 216 samples (88%) collected from 72 patients whilst the TMA assay detected viremia in 178 of the 216 samples (82%) (P = 0.019). The HBcrAg concentration correlated linearly with the HBV DNA concentration (P < 0.001) over a range which varied 100 000-fold. The accuracy in the measurement of the patients' HBV load obtained using the HBcrAg assay was not affected by the absence of hepatitis B e antigen from the serum or the presence of precore mutations in the HBV genome. In patients without anti-viral drugs, changes in their serum HBcrAg concentration over time corresponded to their HBV DNA concentration. In six additional patients who were later treated with lamivudine, HBV DNA concentration declined more rapidly than their HBcrAg concentration. Three months after treatment commenced, the ratio of HBcrAg: HBV DNA had increased in all six patients (P = 0.031). The HBcrAg assay is a sensitive and useful test for the assessment of a patient's HBV load. When monitoring the anti-viral effect of lamivudine, HBcrAg provides a viral marker which is independent of HBV DNA.

New enzyme immunoassay for detection of hepatitis B virus core antigen (HBcAg) and relation between levels of HBcAg and HBV DNA

A new enzyme immunoassay specific for hepatitis B virus (HBV) core antigen (HBcAg) was developed. In order to detect HBcAg, specimens were pretreated with detergents to release HBcAg from the HBV virion and disassemble it to dimers, and simultaneously, the treatment inactivated anti-HBc antibodies. HBcAg detected by the assay peaked with HBV DNA in density gradient fractions of HBV-positive sera. The assay showed a wide detection range from 2 to 100,000 pg/ml. We observed no interference from anti-HBc antibody or blood components, but the assay was inhibited by very high concentrations (>1 microg/ml; corresponding to 80 signal/cutoff) of HBeAg. When the cutoff value was tentatively set at 4 pg/ml, all healthy control (HBsAg and HBV DNA negative, n = 160) and anti-hepatitis C virus-positive (n = 55) sera were identified as negative. HBcAg concentrations correlated very closely with HBV DNA (r = 0.946, n = 145) in 216 samples from 72 hepatitis B patients. In seroconversion panels, HBcAg concentrations changed in parallel with HBV DNA levels. The assay, therefore, offers a simple method for monitoring hepatitis B patients. With a series of sera during lamivudine therapy, HBV DNA levels fell sharply and the HBcAg concentration also decreased, but the change in HBcAg was smaller and more gradual. The supposed mechanism of these changes and their clinical significance are discussed.

Correlation of HBV DNA levels in serum and liver of chronic hepatitis B patients with cirrhosis

AIM

We sought to evaluate whether serum HBV DNA levels correlates with the liver free HBV DNA levels in chronic hepatitis B.

METHODS

Thirty-three consecutive chronic hepatitis B patients with cirrhosis were included in this study. Twenty cases had detectable serum HBV DNA (> 1.8 pg/ml). All had detectable free liver HBV DNA.

RESULTS

There was a strong correlation between the serum and liver HBV DNA levels (P = 0.0018, r = 0.717). Thirteen cases had undetectable serum HBV DNA. Among them, six cases still had detectable liver free HBV DNA. Eight cases were HBeAg-positive. Among them, seven cases were positive for both serum and liver HBV DNA, and one case was negative for both serum and liver HBV DNA. Twenty-five cases were HBeAg-negative and anti-HBe-positive. Among them, 13 cases were positive for serum HBV DNA, and 19 cases were positive for liver HBV DNA. No significant difference was noted for positivity of serum HBV DNA or liver free HBV DNA between HBeAg-positive and HBeAg-negative groups. The level of serum HBV DNA(491 +/- 772 pg/ml versus 203 +/- 447 pg/ml, p = 0.07) and liver free HBV DNA (33 +/- 81 pg/microg versus 6 +/- 15 pg/microg, p = 0.13) was also not statistically different.

CONCLUSION

In conclusion, serum HBV DNA levels is strongly correlated with liver HBV DNA levels in chronic hepatitis B with cirrhosis. Liver free HBV DNA can still be detected in about half of the cirrhotic patients with undetectable serum HBV DNA. Serum HBeAg is not a good predictor of serum or liver HBV DNA levels in cirrhotic patients.

Sensitive enzyme immunoassay for hepatitis B virus core-related antigens and their correlation to virus load

A sensitive enzyme immunoassay (EIA) specific for hepatitis B virus core antigen (HBcAg) and hepatitis B e antigen (HBeAg) was developed. We designated the precore/core gene products as hepatitis B virus (HBV) core-related antigens (HBcrAg). In order to detect HBcrAg even in anti-HBc/e antibody-positive specimens, the specimens were pretreated in detergents. The antibodies are inactivated by this pretreatment and, simultaneously, the antigens are released and the epitopes are exposed. The assay demonstrated 71 to 112% recovery using HBcrAg-positive sera. We observed no interference from the tested anticoagulants or blood components. When the cutoff value was tentatively set at 10(3) U/ml, all healthy control (HBsAg/HBV-DNA negative; n = 108) and anti-HCV antibody-positive (n = 59) sera were identified as negative. The assay showed a detection limit of 4 x 10(2) U/ml using recombinant antigen. Detection limits were compared in four serially diluted HBV high-titer sera. The HBcrAg assay demonstrated higher sensitivity than HBV-DNA transcription-mediated amplification (TMA) or HBeAg radio immunoassay (RIA) in the dilution test. HBcrAg concentrations correlated well with HBV-DNA TMA (r = 0.91, n = 29) and in-house real-time detection-PCR (r = 0.93, n = 47) in hepatitis B patients. On HBeAg/anti-HBe antibody seroconversion panels, the HBcrAg concentration changed in accordance with HBV-DNA levels. HBcrAg concentration provides a reflection of HBV virus load equivalent to HBV-DNA level, and the assay therefore offers a simple method for monitoring hepatitis B patients.

Quantitative detection of hepatitis B virus DNA in serum by a new rapid real-time fluorescence PCR assay

A sensitive and accurate HBV DNA quantification assay is essential for monitoring hepatitis B virus (HBV) replication. This study evaluated a real-time PCR method performed in the LightCycler analyser for quantitative HBV DNA assay. HBV DNA results with this method were compared with those obtained using a branched-chain DNA (bDNA) solution hybridization assay. Real-time PCR was performed using two adjacent fluorescently labelled probes and primers corresponding to the HBV core gene. The same standard employed in the bDNA assay was used for calibration. Serum samples came from 193 HBV surface antigen (HBsAg)-positive patients (34 HBV e antigen (HBeAg)-positive and 93 with antibody to HBeAg (anti-HBe)), and 66 asymptomatic HBV carriers. In addition, we analysed serum samples from 8 anti-HBe-positive patients who had been receiving lamivudine treatment for more than three years. A linear standard curve was seen in the range from 10(3) to 10(8) copies/mL. In the reproducibility analysis, intra-assay coefficient of variation (CVs) at two known HBV DNA concentrations were 4% and 2% and interassay CVs were 6% and 4%. The median of serum HBV DNA by real-time PCR was 9.2 x 10(8) copies/mL in HBeAg-positive patients with persistently elevated alanine aminotransferase (ALT) levels, 1.3 x 10(7) copies/mL in anti-HBe-positive cases with persistently elevated ALT levels, 3.7 x 10(4) copies/mL in anti-HBe-positive patients with fluctuating ALT levels and 10(4) copies/mL in asymptomatic HBV carriers. The differences in HBV DNA levels among the various groups studied were statistically significant (P < 0.05). The cut-off between chronic hepatitis patients and asymptomatic carriers was found to be at a serum HBV DNA concentration of 5 x 10(4) copies/mL. Of the 109 serum samples with a viral load < 7.5 x 10(5) (negative by bDNA assay) 44 (40%) were positive by real-time PCR: 24 (56%) chronic hepatitis and 20 (33%) asymptomatic carriers. There was a positive association between HBV DNA levels determined by real-time PCR and ALT levels (P < 0.05), which was not observed with the bDNA assay for HBV DNA quantification. At 12 months of lamivudine treatment, 6 patients (75%) showed HBV DNA levels < 5 x 10(4) copies/mL (range < 10(3)-2 x 10(3)), significantly lower than at baseline. At 36 months, 2 of 8 (25%) showed HBV DNA levels persistently lower than 5 x 10(4) copies/mL (1.7 x 10(3), 6 x 10(3)). The LightCycler quantitative real-time PCR is a practical, sensitive, reproducible single-tube assay with a wide dynamic range of detection. The assay is automatic except for DNA extraction and the running time is only 70 min. The LightCycler real-time PCR is useful for identifying different states of HBV infection and for evaluating the efficacy of viral therapy.

Quantitative detection of hepatitis B virus DNA by real-time nucleic acid sequence-based amplification with molecular beacon detection

We have developed a hepatitis B virus (HBV) DNA detection and quantification system based on amplification with nucleic acid sequence-based amplification (NASBA) technology and real-time detection with molecular beacon technology. NASBA is normally applied to amplify single-stranded target RNA, producing RNA amplicons. In this work we show that with modifications like primer design, sample extraction method, and template denaturation, the NASBA technique can be made suitable for DNA target amplification resulting in RNA amplicons. A major advantage of our assay is the one-tube, isothermal nature of the method, which allows high-throughput applications for nucleic acid detection. The homogeneous real-time detection allows a closed-tube format of the assay, avoiding any postamplification handling of amplified material and therefore minimizing the risk of contamination of subsequent reactions. The assay has a detection range of 10(3) to 10(9) HBV DNA copies/ml of plasma or serum (6 logs), with good reproducibility and precision. Compared with other HBV DNA assays, our assay provides good sensitivity, a wide dynamic range, and high-throughput applicability, making it a viable alternative to those based on other amplification or detection methods.

Hepatitis B virus DNA levels, precore mutations, genotypes and histological activity in chronic hepatitis B

The present study aimed to clarify how viraemia levels reflect the clinical stages of chronic hepatitis B virus (HBV) infection, in particular studying whether 'healthy carriers' can be identified by analysing HBV DNA levels with a highly sensitive quantitative assay. Histology activity index (HAI), alanine aminotransferase (ALT) level, genotype and precore mutations were compared with the HBV DNA level, as measured using the Amplicor HBV Monitor assay in a prospective study. In 124 hepatitis B e antigen-negative (HBeAg-) patients, the majority with mild liver disease, log HBV DNA levels showed a Gaussian distribution around a geometric mean of 33 000 genome copies ml-1, and increasing HBV DNA level was associated with significantly higher inflammation (HAIinfl) and fibrosis (HAIfibr) scores and higher ALTi (ALT / the upper reference value). Severe inflammation (HAIinfl > or = 7) was seen in 83% (five of six), 36% (eight of 22) and 3% (one of 37) of HBeAg- patients with HBV DNA > 107, > 2 x 105 and < 104 copies ml-1, respectively. In severe HBeAg- hepatitis, patients with precore wild-type infection had lower HBV DNA levels than those with precore mutants. In 36 HBeAg-positive (HBeAg+) patients, no correlation between HBV DNA level and liver damage was seen. Ninety-six per cent of HBeAg- patients with ALTi < 0.5 had HAIinfl < or = 3. In HBeAg- carriers with ALTi 0.5-1.0, the relative risk for severe inflammation, comparing HBV DNA > 2 x 105 copies ml-1 vs < 2 x 105 copies ml-1, was 14.7. In conclusion, in HBeAg- carriers, HBV DNA < 104 copies ml-1 or ALTi < 0.5 indicates mild inflammation, while > 2 x 105 copies ml-1 of HBV DNA may justify further investigations. Precore status may be relevant for the interpretation of viraemia.

Detection of Yersinia pestis using branched DNA

In contrast to target amplification methods, e.g. polymerase chain reaction, the branched DNA (bDNA) signal amplification method quantitates target nucleic acid at physiological levels, involving a series of hybridization reactions without thermal cycling. In this report, we describe a modification of the bDNA assay in which a <<concatenated>> preamplifier oligonucleotide (206 mer) is used in concert with ELISA and light addressable potentiometric sensor (LAPS) formats to detect the plasminogen activator (pla) gene of Yersinia pestis, the etiological agent of plague. Pla is encoded by a 9.6-kb plasmid pPCP, which is essential for virulence. The detection limit of the bDNA-ELISA and LAPS assays is less than 10 000 and 1000 molecules of Y. pestis plasmid DNA, respectively.

Comparison of two methods for quantification of hepatitis B viral DNA

BACKGROUND

Quantitation of serum hepatitis B virus (HBV) DNA has proven useful in assisting with patient management and treatment and several commercially available assays have been developed to quantify serum HBV-DNA levels.

METHODS

The performance of the cross-linking assay and the branched-DNA signal amplification (bDNA) assay for the quantitative measurement of HBV-DNA was studied in 99 hepatitis B surface antigen-positive and viraemic patients.

RESULTS

Of these samples, 82 (83%) were positive for HBV-DNA by both assays and four (4%) were below the cut-off for both assays. Of the remaining 13 samples, 10 contained measurable levels of HBV-DNA by the cross-linking assay alone and three other samples contained measurable levels of HBV-DNA by the bDNA assay alone. The sensitivity gain of the cross-linking assay relative to bDNA assay in this study population was 10/92 (11%). In addition, a linear regression analysis showed that the HBV-DNA levels obtained from both assays was significantly correlated (gamma=0.974, P< 0.0001).

CONCLUSIONS

These findings suggest that the recently developed cross-linking assay is more sensitive than the bDNA assay for the quantitative determination of HBV-DNA.

Quantitative detection of hepatitis B virus by transcription-mediated amplification and hybridization protection assay

We have developed a sensitive and quantitative assay using transcription-mediated amplification and hybridization protection assay for the detection of hepatitis B virus (HBV) DNA in serum. The transcription-mediated amplification was carried out in a single tube. The hybridization protection assay was carried out in a microtiter plate with two probes with different specific activities to obtain a broad detection range. As a result, the assay had a detection range of 5 x 10(3) to 5 x 10(8) genome equivalents (GE)/ml and good quantitative accuracy on a logarithmic scale. A moderately sized manual assay run can be completed within 5 h. Measurements of the amounts of HBV DNA in clinical samples by the assay showed the amounts under various disease conditions to be widely distributed (more than 5 logs, from approximately 5 x 10(3) to 5 x 10(8) GE/ml). It was also shown that the amount of HBV DNA in one chronic hepatitis patient varied widely, with a range of more than 5 logs during long-term monitoring. Our assay has the potential to be used to monitor and determine the prognosis of HBV patients and carriers, especially during interferon treatment.

Clinical evaluation of the branched DNA assay for hepatitis B virus DNA detection in patients with chronic hepatitis B lacking hepatitis B e antigen and treated with interferon-alpha

The aim of this study was to evaluate the Chiron branched DNA (bDNA) assay for detection of serum hepatitis B virus (HBV) DNA in patients with chronic hepatitis B lacking hepatitis B e antigen (HBeAg) and undergoing interferon (IFN) therapy. Results obtained with the bDNA assay were compared with those obtained using the Abbott liquid hybridization (LH) assay and the polymerase chain reaction (PCR). Serial samples (274) from 34 patients were analysed. Analysis of variance results indicated that bDNA values were more significantly correlated than LH values with both PCR positive/negative results (probability of artifact (Prob > F) = 0.7 and 0.09 for LH and bDNA assays, respectively) and presence/absence of precore mutations (Prob > F = 0.21 and 0.001 for LH and bDNA assays, respectively). Both bDNA and LH results correlated highly with alanine aminotransferase (ALT) values (both had Prob > F values of 0.0) while PCR was not correlated with ALT (Prob > F = 0.05). In 26 evaluable patients, a model based on a generalized Knodell score was used to predict response to IFN therapy, as defined by normalization of ALT values during therapy. This model discriminated well between non-responders and responders. The bDNA results correlated well with the generalized Knodell score, while the LH results did not (Prob > F = 0.04 and 0.19 for the bDNA and LH assays, respectively). In conclusion, the bDNA assay appears to be useful for quantification of HBV DNA levels in HBeAg-negative chronic hepatitis as it correlates with biochemical and histological indications of disease severity as well as with response to IFN therapy.

What technique should be used for routine detection and quantification of HBV DNA in clinical samples?

Detection of hepatitis B virus (HBV) DNA in serum allows monitoring of HBV replication and assessing responses to antiviral treatment. HBV DNA quantification measures virus replication and can be used as a prognosis indicator of liver disease and an index of response to antiviral drugs. The aim of this study was to compare the performances of three HBV DNA detection and/or quantification techniques for assessing HBV replication. Three hundred unselected sera with a request for HBV DNA detection and quantification were tested with a molecular hybridisation technique without amplification (Digene Hybrid-Capture, Murex Diagnostics Ltd), a signal amplification assay based on branched DNA technology (Quantiplex HBV DNA, Chiron diagnostics), and an 'in-house' qualitative, non quantitative target amplification assay based on the polymerase chain reaction (PCR) with primers located in the S gene of the HBV genome. Hybrid-capture and branched DNA gave concordant results in 278 cases (93%). In the 128 samples positive by both assays, DNA titres in pg/ml were related significantly (r = 0.70, P < 0.0001). but branched DNA titres increased more rapidly than hybrid-capture titres when the amount of HBV DNA in the sample increased. Twenty-two sera (7%) were negative by hybrid-capture, but positive in branched DNA (detection rate gain: 15%). In these 22 patients, DNA titres were low, HBsAg was present in all instances and alanine aminotransferase activity was elevated in 18 patients (82%); HBeAg was present in seven patients (32%) and anti-HBe antibodies in 18 patients (82%); liver biopsy, undertaken in 18 patients, revealed chronic active hepatitis in all instances, associated with cirrhosis in eight cases. Qualitative, non-quantitative HBV DNA PCR was positive in 75 (50%) of the 150 hybrid-capture-negative, branched DNA-negative samples, including a significant proportion of patients without evidence of ongoing HBV-related liver disease. The results show that in general, the branched DNA assay detects HBV DNA in more patients than hybrid-capture and that this improved detection rate is relevant clinically and genome equivalents/ml are preferred to pg/ml to quantify HBV DNA in clinical specimens and finally qualitative, non-quantitative polymerase chain reaction can detect HBV DNA in patients without evidence of active HBV-related liver disease. This study emphasizes the need for more sensitive, university standardised quantitative HBV DNA assays and for the definition of clinically relevant cutoffs with these assays.

A clinical evaluation of a new method for HBV DNA quantitation in patients with chronic hepatitis B

Selection of HBsAg-positive patients for antiviral therapy requires an estimation of disease activity and viral replication. Serum transaminases and histological analysis are commonly used to assess disease activity, and viral replication is assessed by serological testing of HBeAg and serum hepatitis B virus (HBV) DNA. Dot blot hybridisation may be insufficiently sensitive to corroborate low-grade replication in patients with active hepatitis, and polymerase chain reaction (PCR) may be testing too sensitive for this role. Theoretically an assay of intermediate sensitivity is therefore required. Our aim was to evaluate whether the branched chain DNA (bDNA) assay would fulfil this function. Seventy-one HBsAg-positive patients were tested for HBV DNA by the bDNA assay; 64 were also tested by dot blot hybridisation and, when appropriate, also by PCR. Thirty-seven (52%) patients were positive for HBV DNA by the bDNA assay. HBV DNA was detected in the majority (21/28; 75%) of HBeAg-positive patients but also in 14 of 36 (39%) anti-HBe-positive patients. HBV DNA was detected by the bDNA assay in 20 of 48 (42%) patients negative for HBV DNA by dot blot hybridisation assay. All patients positive for HBV DNA by dot blot hybridisation were also positive by the bDNA assay. Sixteen of twenty-five (64%) patients negative for HBV DNA by the bDNA assay were positive for HBV DNA by PCR. The bDNA assay is a sensitive and reliable method for the detection of HBV DNA. As nucleoside analogue therapy becomes more widely available, the assay should provide a useful tool for the selection for and monitoring of patients on antiviral therapy.