Comparison of two methods for quantification of hepatitis B viral DNA

Quantification of hepatitis B virus genomes and infectivity in human serum samples

BACKGROUND

Hepatitis B virus (HBV) infections are still a major health issue, with approximately 350 million people chronically infected with HBV worldwide. Information about the minimum copy number of HBV genomes required for infection would be useful as a reference for drug and vaccine development; for monitoring HBV patients during treatment; for screening of blood, organ, and tissue donors; and for regulating nucleic acid amplification assays for HBV.

STUDY DESIGN AND METHODS

Serum samples from chronic carriers (hepatitis B surface antigen-positive and antibody to HBV core antigen-positive) of the three most common subtypes of HBV were studied; their infectivity titers had been evaluated previously in chimpanzees. The genotypes of the HBV samples were determined by DNA sequences and type-specific amino acids of the S gene of HBV. Copy numbers of HBV DNA were quantified by real-time TaqMan polymerase chain reaction (PCR) and by nested PCR applied to limiting dilutions. The copy number determined for each inoculum was compared with previously defined chimpanzee infectivity titers.

RESULTS

The genotypes of the HBV adw, ayw, and adr inocula were A, D, and C, respectively. The concentration of HBV DNA was determined to be 5.4 x 10(9), 2.5 x 10(9), and 3.1 x 10(8) genome equivalents (geq) per mL for serum samples containing the adw, ayw, and adr, respectively. The chimpanzee infectivity titers per milliliter of these initial HBV-containing serum samples were previously determined to be 10(7.5) for adw, 10(7.5) for ayw (MS-2 strain), and 10(8) for adr.

CONCLUSION

The minimal copy number of HBV DNA in chronic carriers of HBV that can infect the chimpanzee model was estimated to be from 3 to 169 geq based upon the three well-characterized inocula.

Hepatitis B post-partum e antigen clearance in hepatitis B carrier mothers: Correlation with viral characteristics

BACKGROUND

The purpose of the present paper was to correlate hepatitis B virus (HBV) genotype, e antigen titer, HBV-DNA level and precore/basal core promoter mutations with post-partum e antigen clearance in hepatitis B e antigen (HBeAg)-positive carrier mothers.

METHODS

A total of 40 consecutive HBeAg-positive carrier mothers were studied from January 2002 to January 2003. The blood samples were taken at delivery, 3-4 months and at 1 year after delivery, and the follow-up period was until 1 year after delivery. All sera were assayed for HBeAg, HBV-DNA level, HBV genotype and precore/basal core promoter mutations. The correlation between HBV characteristics and post-partum e antigen clearance was analyzed by Mann-Whitney, Pearson chi2 and multiple logistic regression tests.

RESULTS

The mean age of the 40 HBeAg-positive carrier mothers was 29.9 +/- 5.3 years with a mean parity of 1.4 +/- 0.7. Five of them (group I) had post-partum e antigen clearance, which persisted thereafter, whereas the remaining 35 carrier mothers (group II) had persistent positivity of HBeAg during the follow-up period. The prepartum comparisons of HBV characteristics between groups I and II were comparable in terms of demographics and distributions of HBV genotype and precore/basal core promoter mutations. In contrast, group I carrier mothers had lower HBeAg titer and HBV-DNA level than group II carrier mothers (1:80 vs 1:4000, P = 0.02, and 3.75 x 10(5) vs 3 x 10(8) copies/mL, P = 0.028, respectively).

CONCLUSIONS

Post-partum e antigen clearance in HBeAg-positive carrier mothers is closely associated with prepartum low HBeAg titer or HBV-DNA level.

Evaluation of the COBAS amplicor HBV monitor assay and comparison with the ultrasensitive HBV hybrid capture 2 assay for quantification of hepatitis B virus DNA

Performance characteristics of the COBAS Amplicor HBV Monitor test (Roche Diagnostics), which measures hepatitis B virus (HBV) DNA quantitatively, were evaluated and compared with the Ultrasensitive HBV Hybrid Capture 2 (HC2; Digene Corporation) assay. Linearity and within-run precision were assessed for both methods by using eight HBV DNA-positive samples serially diluted to obtain a range of <100 to 500,000 HBV DNA copies/ml and run in triplicate. Agreement between the methods was studied with 100 clinical samples. HC2 assay performance near the limit of detection was investigated through repeat testing of 149 samples with HC2 and testing of 37 samples with HC2 results of <4,700 HBV DNA copies/ml by Amplicor assay and a qualitative PCR assay. The linearity experiment for Amplicor had regression of observed values compared to expected values (y = 1.073x - 0.247; R(2) = 0.993, n = 32; for HC2, y = 0.855x + 0.759, R(2) = 0.729, n = 18). Within-run standard deviation of log HBV DNA copies/ml ranged from 0.003 to 0.348 (Amplicor) and 0.027 to 0.253 (HC2). Agreement assessed by Deming regression was poor [Amplicor = 1.197(HC2) - 0.961; R(2) = 0.799, standard error of the estimate (SEE) = 0.710, n = 94]. Near the lower limit of detection, 32 of 149 repeat HC2 results were <4,700 HBV DNA copies/ml. Of the 37 samples with HC2 results of <4,700 HBV DNA copies/ml, HBV DNA was not detected in 15 samples, while HBV DNA was detected by at least one PCR method in 12 samples. Amplicor is linear from 200 to 200,000 HBV DNA copies/ml with undiluted samples, and this range can be expanded through dilution. Inconsistent HC2 results near the limit of detection justify use of a grey zone.

Establishment and assessment of two methods for quantitative detection of serum duck hepatitis B virus DNA

AIM: To establish and assess the methods for quantitative detection of serum duck hepatitis B virus (DHBV) DNA by quantitative membrane hybridization using DHBV DNA probe labeled directly with alkaline phosphatase and fluorescence quantitative PCR (qPCR).

METHODS: Probes of DHBV DNA labeled directly with alkaline phosphatase and chemiluminescent substrate CDP-star were used in this assay. DHBV DNA was detected by autoradiography, and then scanned by DNA dot-blot. In addition, three primers derived from DHBV DNA S gene were designed. Semi-nested primer was labeled by AmpliSensor. Standard curve of the positive standards of DHBV DNA was established after asymmetric preamplification, semi-nested amplification and on-line detection. Results from 100 samples detected separately by alkaline phosphatase direct-labeled DHBV DNA probe with dot-blot hybridization and digoxigenin-labeled DHBV DNA probe hybridization. Seventy samples of duck serum were tested by fluorescent qPCR and digoxigenin-labeled DHBV DNA probe in dot-blot hybridization assay and the correlation of results was analysed.

RESULTS: Sensitivity of alkaline phosphatase direct-labeled DHBV DNA probe was 10 pg. The coincidence was 100% compared with digoxigenin-labeled DHBV DNA probe assay. After 30 cycles, amplification products showed two bands of about 180 bp and 70 bp by 20 g/L agarose gel electrophoresis. Concentration of amplification products was in direct proportion to the initial concentration of positive standards. The detection index was in direct proportion to the quantity of amplification products accumulated in the current cycle. The initial concentration of positive standards was in inverse proportion to the number of cycles needed for enough quantities of amplification products. Correlation coefficient of the results was (0.97, P < 0.01) between fluorescent qPCR and dot-blot hybridization.

CONCLUSION: Alkaline phosphatase direct-labeled DHBV DNA probe in dot-blot hybridization and fluorescent qPCR can be used as valuable means to quantify DHBV DNA in serum.

Clinical evaluation of the COBAS Amplicor HBV monitor test for measuring serum HBV DNA and comparison with the Quantiplex branched DNA signal amplification assay in Taiwan

AIMS

To evaluate the performance characteristics and clinical usefulness of the COBAS Amplicor HBV monitor (COBAS-AM) test in Taiwan and to examine its correlation with the Quantiplex branched DNA signal amplification (bDNA) assay for measuring serum hepatitis B virus (HBV) DNA concentrations.

METHODS

HBV DNA was measured by the COBAS-AM test in 149 sera from chronic HBV infected patients that had previously been analysed by the bDNA assay.

RESULTS

The COBAS-AM test showed good reproducibility, with acceptable intra-assay and interassay coefficients of variation (1.6% and 0.9%, respectively) and good linearity (r2=0.98). The overall sensitivity of the COBAS-AM test was significantly higher than that of the bDNA assay (95.3% v 83.2%): 69.6% of samples with HBV DNA below the detection limit of the bDNA assay could be measured by the COBAS-AM test. There was a significant correlation between the results of the two assays (r=0.901; p<0.0001). On average, the results derived from the COBAS-AM test were 0.55 log lower than those of the bDNA assay. HBV DNA concentrations were significantly higher among HBV e antigen (HBeAg) positive patients than negative ones, and higher among patients with abnormal alanine aminotransferase (ALT) concentrations than those with normal ALT concentrations (p=0.0003).

CONCLUSIONS

The COBAS-AM assay, more sensitive in HBeAg negative samples than the bDNA assay, can effectively measure HBV DNA concentrations in Taiwanese patients. HBV DNA values measured by the COBAS-AM test and bDNA assay correlate significantly.

Hepatitis B virus genotypes and spontaneous hepatitis B e antigen seroconversion in Taiwanese hepatitis B carriers

Hepatitis B virus (HBV) is classified into eight genotypes (A-H), and genotype C is associated with more aggressive liver disease compared to genotype B. However, the mechanisms responsible for the clinical differences remain unclear. To test whether genotype C patients had with lower rates of spontaneous hepatitis B ge antigen (HBeAg) seroconversion than genotype B patients, stored serum samples from 146 Taiwanese adult HBeAg-positive hepatitis B carriers followed-up for a mean of 52 months (range, 12-120 months) were tested for HBV genotype by a molecular method. Genotype C patients were significantly older than genotype B patients (mean age, 37 +/- 12 vs. 29 +/- 10 years, P < 0.001). During the follow-up period, genotype C patients had a significantly lower rate of spontaneous HBeAg seroconversion than genotype B patients (27 vs. 47%, P < 0.025). Spontaneous HBeAg seroconversion occurred one decade later in genotype C patients compared with genotype B patients. Multivariate analyses identified age < or =35 years (odds ratio: 2.08; 95% confidence interval [CI], 1.07-4.0; P < 0.05), high baseline serum alanine aminotransferase level (odds ratio: 2.34; 95%CI, 1.39-4.09; P < 0.005), and HBV genotype B (odds ratio: 1.94; 95%CI, 1.03-3.63; P < 0.05) as independent factors associated with spontaneous HBeAg seroconversion. In conclusion, genotype C patients, compared to genotype B patients, have a delayed HBeAg seroconversion in the immune clearance phase of chronic HBV infection, which may contribute to a more progressive liver disease and more refractory to antiviral therapy.

Serum HBV DNA as a marker of efficacy during therapy for chronic HBV infection: analysis and review of the literature

Currently, compounds under evaluation for treatment of chronic hepatitis B virus (HBV) infection are evaluated with liver histology as the primary end point for efficacy. However, because of practical limitations in serial liver biopsies, there is a need for alternate markers to assess efficacy over shorter periods of time. Considering the direct correlation between viral replication and disease progression during human immunodeficiency virus and hepatitis C virus infection, we explored whether such a correlation exists for HBV infection. We reviewed the literature and conducted an analysis to investigate the relationship between absolute or treatment-induced changes in HBV DNA levels and other accepted markers of disease activity. A total of 26 prospective studies met our selection criteria, including 33 evaluable treatment arms. The study treatments consisted of nucleosides and/or interferon regimens and control arms. We found statistically significant and consistent correlations between viral load level or change and histologic grading and biochemical and serologic response. Our analysis suggests that a treatment-induced reduction in HBV DNA level can be used for assessing efficacy of treatment regimens. Further, we observed that quantitative HBV DNA has a broader dynamic range than histology, allowing demonstration of differences between 2 active treatments of unequal potency. The analysis showed stronger results in studies using nucleoside regimens and in hepatitis B e antigen (HBeAg)-positive patients. In conclusion, the goal of anti-HBV therapy should be profound and durable viral suppression, as defined by very sensitive assays. Additional prospective studies are needed to precisely determine the desirable level of viremia to attain.

The effect of lamivudine therapy in hepatic decompensation during acute exacerbation of chronic hepatitis B

BACKGROUND/AIMS

Severe acute exacerbation (AE) of chronic hepatitis B (CHB) can lead to hepatic decompensation and death. The aim of this study was to investigate the effect of lamivudine therapy in hepatic decompensation during such AEs.

METHODS

In a 10-month period, a total of 60 consecutive AE patients with jaundice and prolonged prothrombin time over 3s were treated with lamivudine 150 mg daily. As a historical control, another 31 CHB patients with AE resulting in hepatic decompensation hospitalized in an immediate past 6-month period were enrolled for comparison.

RESULTS

Patients in both groups were comparable in clinical and biochemical features. After a median treatment period of 6 weeks (range 1-48 weeks), all of the 25 patients with pretherapy bilirubin level < 20 mg/dl in the treatment group survived, while five (25%) of 20 patients in the control group died (P=0.013; odds ratios, 2.667; 95% confidence interval, 1.787-3.979). However, the mortality rate was similar in patients with pretherapy bilirubin level > or =20 mg/dl in both groups.

CONCLUSIONS

These results suggest that lamivudine may prevent fatality in CHB patients with hepatic decompensation if therapy starts early enough or before serum bilirubin level rise over 20 mg/dl, but helps little if serum level already risen over that level.

Hepatitis B genotypes and the response to interferon therapy

BACKGROUND/AIMS

Possible pathogenic differences among hepatitis B virus (HBV) genotypes have been observed; however, the response to interferon therapy among HBV genotypes remains unknown. We therefore analyzed the efficacy of interferon alfa in the treatment of chronic hepatitis B patients with different HBV genotypes.

METHODS

Fifty-eight genotype B or C infected chronic hepatitis B patients who had been treated with interferon alfa-2b were retrospectively studied. The response to interferon was defined as normalization of serum aminotransferase level, loss of hepatitis B e antigen and HBV DNA 48 weeks post-treatment.

RESULTS

Baseline data of both groups of patients were comparable; however, genotype C patients had a higher serum aminotransferase level and a higher frequency of core promoter mutation. The response rate was 41% and 15% in genotype B and C patients, respectively (p=0.045). In those with higher serum aminotransferase levels, the response rate was 50% and 17%, respectively (p=0.025). Additionally, younger age and genotype B infection may predict a better response to interferon alfa.

CONCLUSIONS

HBV genotype C, compared to genotype B, is associated with a higher frequency of core promoter mutation, and a lower response rate to interferon alfa therapy.

Prednisolone priming enhances Th1 response and efficacy of subsequent lamivudine therapy in patients with chronic hepatitis B

Asian lamivudine trial has shown that hepatitis B e antigen (HBeAg) seroconversion rate during 1 year of lamivudine therapy was only 16% but was 64% in the subgroup of patients with a pretherapy serum alanine transaminase (ALT) level over 5 times the upper limit of normal (ULN). To test whether ALT rebound following corticosteroid priming enhances response to lamivudine therapy, a pilot study was conducted in 30 patients with ALT levels less than 5x ULN (43-169; N < 36 U/L). They received 30 mg of prednisolone daily for 3 weeks, 15 mg daily for 1 week, no treatment for 2 weeks, and then 150 mg of lamivudine daily for 9 months. Complete response (CR) was defined as ALT normalization with HBV-DNA seroclearance and HBeAg seroconversion. Peripheral blood mononuclear cell proliferation and cytokine secretion in response to recombinant HBV core antigen were serially assayed in 7 patients during priming and after withdrawal of prednisolone. Clinical rebound with an ALT over 5x ULN was observed in 20 patients (67%). Of these 20, 12 (60%) showed CR as compared with 1 (10%) of the 10 patients without significant ALT rebound (P <.002). The HBeAg seroconversion sustained in 70% of the patients 3 to 6 months after the end of lamivudine therapy. Immunological assays revealed that the responders showed Th1 dominant response and higher stimulation index to prednisolone priming. No serious side effect was encountered. These results suggest that corticosteroid priming induced immune/ALT rebound greatly enhances response to lamivudine therapy in chronic hepatitis B. Confirmation by randomized controlled trial is needed.

Case report: dramatic response to lamivudine therapy following corticosteroid priming in chronic hepatitis B

A 21 year-old male patient with chronic hepatitis B was treated with lamivudine 150 mg daily after withdrawal of a short course of oral prednisolone (30 mg daily for 3 weeks, 15 mg daily for 1 week). Serum hepatitis B virus (HBV)-DNA increased during prednisolone pretherapy and serum alanine aminotransferase (ALT) was increasing after withdrawal of prednisolone. Clearance of HBV-DNA with hepatitis B e antigen seroconversion and ALT normalization occurred within 2 months after starting lamivudine therapy. If this dramatic response to lamivudine therapy after corticosteroid priming is confirmed by further studies, the regimens used in this particular case might become a powerful therapeutic tool for chronic HBV infection.