Comparison of plasma virus loads among individuals infected with hepatitis C virus (HCV) genotypes 1, 2, and 3 by quantiplex HCV RNA assay versions 1 and 2, Roche Monitor assay, and an in-house limiting dilution method

Evaluation of hepatitis C virus RNA RT/PCR qualitative and quantitative second generation assays

Hepatitis C virus (HCV) RNA qualitative and quantitative second generation assays (Amplicor HCV v2.0 and Amplicor HCV Monitor v2.0, respectively) were evaluated by testing serum samples from 132 blood donors anti-HCV positive HCV RNA negative by first generation qualitative assay and 326 viremic patients. An HCV RNA transcript was synthesized and ten-fold dilutions were used to assess sensitivity. Second generation assays were one log more sensitive than their respective first generation tests (10(2) copies per ml vs. 10(3) for the qualitative tests; 10(3) copies per ml vs. 10(4) for the quantitative tests). From the 132 anti-HCV positive RNA negative subjects, 6 (5%) were positive by Amplicor v2.0. Quantification figures by Monitor v2.0 were similar in genotypes 1, 2 and 3, whereas Monitor 1.0 values were higher in genotype 1 than in genotype 2 or 3. In 114 patients, branched-DNA v2.0 obtained higher values than Monitor v2.0 and Monitor v1.0 (6.6+/-0.6 log RNA copies per ml, 6.4+/-0.6, and 5.3+/-0.7, respectively, P<0.001). HCV RNA qualitative and quantitative second generation assays are more sensitive and genotype independent than first generation assays.

Mutations in the E2-PePHD and NS5A region of hepatitis C virus type 1 and the dynamics of hepatitis C viremia decline during interferon alfa treatment

Both a double-stranded RNA-dependent protein kinase (PKR)-phosphorylation homology domain (PePHD) within the E2 protein and a PKR-binding domain within the nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) genotype 1 isolates inhibit the function of the interferon alfa (IFN-alpha)-induced antiviral effector protein PKR in vitro. We investigated whether the mutational pattern of the E2 region (codons 618-681, including PePHD) of 81 HCV genotype 1-infected patients (HCV-1b [n = 54], HCV-1a [n = 27]) influences the response to IFN-alpha. Initial viral decline (DeltaHCV RNA) was determined at week 1 hereby covering the effector reactions of IFN-alpha-mediated first phase and the immune-mediated second phase. DeltaHCV RNA less than 50% (group 1); DeltaHCV RNA greater than 50% but less than 90% (group 2); and DeltaHCV RNA > or =90% (group 3) were differentiated. The PePHD region was highly conserved; the few mutations (5 patients) did not correlate with DeltaHCV RNA or sustained virologic response to IFN-alpha. Within the flanking regions before and after PePHD (codons 618-681) 72 of 81 patients (89%) had 2.6+/-0.17 mutations (median, 3; range, 1-8) that did not correlate with treatment response. Sequence analysis of the NS5A protein (codons 2,209-2,274, including interferon sensitivity determining region [ISDR]) in 39 of 81 patients showed a higher mean number of mutations in the ISDR (codons 2,209-2,248) in groups 2 (1.28+/- 0.43 [n = 18]) and 3 (1.89+/-0.54 [n = 9]) than in group 1 (0.67+/- 0.19 [n = 12]; P =.049 group 1 vs. 3) and a mutant type ISDR (e.g., > or =4 mutations) was significantly more frequent in sustained virologic responders than in nonresponders or relapsers (2 of 4 [50%] vs. 2 of 35 [6%]; P =.045). Thus, NS5A appears to be functionally relevant in IFN-alpha-induced effector reactions.

Haemophilic patients with hepatitis C have higher viral load compared to other well-defined patient groups

Comparison of hepatitis C viral load between different patient populations has been hampered by the use of different technology in individual studies. We had the impression that haemophilic (HAEM) patients had a higher serum load of hepatitis C virus (HCV) compared to other HCV-infected patients. We therefore studied viral load and genotypes in active illicit drug users (IDU), HAEM patients and patients with post-transfusion hepatitis (PTH). The study comprises 225 HCV-RNA positive patients, 117 IDU, 60 HAEM patients and 48 PTH patients. All patients were anti-HIV negative. HCV-RNA was measured with a quantitative reverse transcription polymerase chain reaction (RT-PCR) method, HCV-genotypes were determined with genotype specific primers in RT-PCR in 221 patients. Four patients could not be genotyped with our assay and were excluded. Overall viral load was higher in genotypes 1 and 2 compared to genotype 3, median values of HCV-RNA were 1,400 x 10(3) geq ml(-1), 2,700 x 10(3) geq ml(-1) and 270 x 10(3) geq ml(-1), respectively. HAEM patients had significantly higher viral load for both genotypes 1 and 3 compared to the IDU and PTH patients. In a multiple linear regression model HCV-RNA viral load was independently associated with HAEM and genotype, but not to age, gender or disease duration. In conclusion, HAEM patients have higher viral load than IDU and PTH patients. The reason for this is unknown, but it may be due to host factors or mode of transmission with multiple inoculations.

A multicenter, randomized trial of daily high-dose interferon-alfa 2b for the treatment of chronic hepatitis c: pretreatment stratification by viral burden and genotype

OBJECTIVES

The aim of this study was to determine prospectively whether an intensive regimen of daily, high-dose interferon would improve the response rate for the treatment of chronic hepatitis C in patients with unfavorable virological characteristics.

METHODS

A total of 104 patients with chronic hepatitis C were randomized at eight centers to receive interferon alfa-2b at a dose of 5 million units (MU) daily or 3 MU t.i.w. for a period of 24 wk. Patients were prospectively randomized by low or high viral burden and stratified by genotype. HCV RNA was measured by quantitative polymerase chain reaction, and response rates were compared between the dosage regimens.

RESULTS

HCV RNA levels dropped more rapidly to lower levels in the group treated with 5 MU daily. In this group, the initial virological response (IR) at wk 12 and the end-of-treatment response (ETR) at wk 24 were double that of patients treated with standard interferon (66% vs 33% and 48% vs 24%, p < 0.01). Sustained response rates were low for both dose groups (14% vs 4%, p = 0.08). Genotype-related differences in initial response rates were present in the standard dose group (63% non-1 genotype vs 24% genotype 1; p = 0.005) but not in those treated with 5 MU daily (66% vs 67%, p = NS). Using multivariate analysis, only the interferon dose was associated with IR and ETR (p = 0.002).

CONCLUSIONS

Daily, high dose interferon rapidly dropped HCV RNA and increased initial and end-of-treatment response rates when compared to t.i.w. regimens. This effect, independent of viral burden and genotype, suggests that patients with unfavorable viral characteristics might benefit from an intensive regimen that promotes rapid viral clearance. These data support further study of the use of high-dose induction regimens. However, improvements in sustained response rates will require additional therapeutic maneuvers such as prolonged therapy or the adjunctive use of ribavirin.

Retreatment for 24 vs 48 weeks with interferon-alpha2b plus ribavirin of chronic hepatitis C patients who relapsed or did not respond to interferon alone

We assessed the efficacy of interferon (IFN) plus ribavirin over 24 or 48 weeks for the retreatment of patients with chronic hepatitis C who had relapsed or did not respond to a previous course of IFN. One-hundred and twenty patients (69 non-responders and 51 relapsers) were randomly assigned to receive IFN-alpha2b (3 million units thrice weekly) plus ribavirin (1,000-1,200 mg per day) for 24 weeks (group A: 58 patients) or 48 weeks (group B: 62 patients). Treatment was discontinued at week 12 if the alanine aminotransferase (ALT) level remained elevated. The rate of sustained response was 15.5% in group A and 37.1% in group B (P = 0.013). Relapsers treated for 48 weeks had a sustained response rate of 66.6% compared with a sustained response rate of only 25% in those treated for 24 weeks (P = 0.004). Moreover, a sustained response was seen in 14.3% of non-responders treated for 48 weeks and in 8.8% of those treated for 24 weeks (P = 0.71). Fifty-three per cent of patients with a normal ALT level and undetectable hepatitis C virus (HCV) RNA at week 12 had a sustained response compared with 14% of those who were HCV RNA positive at week 12 (P < 0.001). Independent predictive factors of sustained response were: therapy for 48 weeks (P = 0.0026), relapse after IFN treatment (P = 0.0006), loss of HCV RNA at week 12 (P = 0.0008) and HCV genotype non-1 (P = 0.024). Hence, in patients with chronic hepatitis C who failed to respond to a previous course of IFN monotherapy, combination therapy with IFN plus ribavirin for 48 weeks seems to be more effective than IFN plus ribavirin for 24 weeks.

Performance characteristics of the COBAS AMPLICOR hepatitis C virus MONITOR Test, version 2.0

We evaluated the performance characteristics of the COBAS AMPLICOR Hepatitis C Virus (HCV) MONITOR Test, version 2.0. Dilution studies using patient specimens demonstrated a lower limit of detection of 1,000 copies per milliliter. The assay was linear from 1,000 to 1 million HCV RNA copies per milliliter. Within-run precision and between-run precision were acceptable (approximately 0.100 and 0.14 SD for log10 [copies per milliliter]). A comparison of this version of the test (y), with the manual AMPLICOR HCV MONITOR Test, version 1.0 (x), yielded the following Deming regression equation: y = 1.004(+/- 0.04)x + 0.654(+/- 0.22); Sy/x¿D = 0.336; n = 92; r2 = 0.846; r = 0.920. Further comparison of the COBAS version 2.0 assay (x) with the QUANTIPLEX HCV bDNA Test (y) yielded the following Deming regression equation: y = 0.943 (+/- 0.130)x + 0.473 (+/- 0.717); Sy/x¿D = 0.194; n = 26; r2 = 0.600; r = 0.774. Version 2.0 detected the spectrum of HCV genotypes better than version 1.0.

Clinical evaluation of the automated COBAS AMPLICOR HCV MONITOR test version 2.0 for quantifying serum hepatitis C virus RNA and comparison to the quantiplex HCV version 2.0 test

A second-generation hepatitis C virus (HCV) quantitative assay (COBAS AMPLICOR HCV MONITOR Test, version 2.0; COBAS HCM-2) has been developed, with the intention of achieving equivalent quantification of all HCV genotypes and improving assay performance. To evaluate the clinical performance of COBAS HCM-2 and its utility in predicting the response to alpha interferon treatment, sera from 215 chronic hepatitis C patients were analyzed and the results were compared with those obtained by the Quantiplex bDNA HCV RNA, version 2.0, assay (bDNA-2). The COBAS HCM-2 had significantly greater sensitivity than bDNA-2 (94.9 versus 88.4%; P < 0.001) when performed with sera from chronic hepatitis C patients who were viremic by a qualitative PCR test. The standard deviations for the within-run and between-run reproducibilities of COBAS HCM-2 were <0. 1 and <0.2, respectively, and it showed an improved linear range between genotypes with the threefold serial dilutions tested (r(2) = 0.986 to 0.995). The COBAS HCM-2 results were positively correlated with the bDNA-2 results, but the values for COBAS HCM-2 were on average 0.96 log lower than the values for bDNA-2. The mean difference in quantification values between these two assays did not differ among samples with different genotypes (0.70 to 1.00 log). No genotype-dependent difference in viral load was observed. The pretreatment viral load was significantly lower in complete responders. By using multivariate analysis, the viral load 2 weeks after the initiation of alpha interferon treatment was the strongest predictor of a complete response. In conclusion, COBAS HCM-2 demonstrated good sensitivity, linearity, and reproducibility and efficiency equal to that of bDNA-2 for the quantification of HCV genotypes 1 and 2. Hence, this assay provides a rapid and reliable method for the quantification of HCV RNA in serum and is useful for the planning of interferon treatment.

Assessment of viral loads in patients with chronic hepatitis C with AMPLICOR HCV MONITOR version 1.0, COBAS HCV MONITOR version 2.0, and QUANTIPLEX HCV RNA version 2.0 assays

The correlation between response to antiviral therapy and pretreatment viral load in patients with chronic hepatitis C has prompted the development of quantitative assays to measure viral load. The aim of our study was to assess the clinical relevance of the newly developed semiautomated PCR system COBAS HCV MONITOR version 2.0 in comparison with (i) the AMPLICOR HCV MONITOR version 1.0 assay, which underestimates RNA concentration of hepatitis C virus (HCV) genotypes 2 to 6, and (ii) the QUANTIPLEX HCV RNA version 2.0 assay, which achieves equivalent quantification for each HCV genotype, with samples from 174 patients diagnosed with chronic hepatitis C before therapy. The level and range of quantification measured with AMPLICOR HCV MONITOR version 1.0 were 1 log lower than when measured with the COBAS HCV MONITOR version 2.0, at 0.261 x 10(6) RNA copies/ml (range, 0.001 x 10(6) to 2.50 x 10(6) RNA copies/ml) and 4.032 x 10(6) RNA copies/ml (range, 0.026 x 10(6) to 72.6 x 10(6) RNA copies/ml), respectively. The two assays showed a poor correlation (r(2) = 0.175). The level and range of quantification were similar when measured with the COBAS HCV MONITOR version 2.0 and QUANTIPLEX HCV RNA version 2.0 assays, at 3.03 x 10(6) RNA copies/ml (range, 0.023 x 10(6) to 72.6 x 10(6) RNA copies/ml) and 4.91 Meq/ml (range, 0.200 to 49.5 Meq/ml), respectively. The two assays showed a strong correlation (r(2) = 0. 686) for each HCV genotype. The duration of treatment (6 or 12 months) is modulated according to HCV genotype and viral load. Our results indicate that COBAS HCV MONITOR version 2.0 and QUANTIPLEX HCV RNA version 2.0 assays showing an equal dynamic range for each HCV genotype are suitable tools to assess patients before therapy.

Performance of the COBAS AMPLICOR HCV MONITOR test, version 2.0, an automated reverse transcription-PCR quantitative system for hepatitis C virus load determination

A clinical evaluation of an automated quantitative PCR assay, the COBAS AMPLICOR HCV MONITOR test, version 2.0 (v2.0), was carried out to assess the performance of this test in comparison with that of the previous, manual version, the AMPLICOR HCV MONITOR test, and with that of nested PCR. Serial dilutions of serum samples infected with genotype 1b, 2a, or 3, as well as synthetic RNA transcripts and serum samples derived from 87 patients with chronic hepatitis C and infected with genotype 1a, 1b, 2a, 2b, 3a, 3b, 4, or 5, were analyzed to determine the ability of the system to efficiently quantify various hepatitis C virus (HCV) genotypes. These experiments showed that the COBAS AMPLICOR HCV MONITOR test, v2.0, has mean intra-assay, interassay, and interoperator coefficients of variation that range from 22 to 34.5% and a 3-logarithm dynamic range, which spans from 10(3) to 10(6) copies/ml. Compared to the previous, manual version of the test, the COBAS AMPLICOR HCV MONITOR test, v2.0, showed an improved efficacy for all genotypes, especially genotypes 2, 3, and 4, whose estimated concentrations were on average 1 logarithm higher. When used to monitor patients under treatment, however, both versions showed the same patterns of viremia, indicating that the COBAS AMPLICOR HCV MONITOR test, v2.0, and the AMPLICOR HCV MONITOR test were equally effective at detecting relative viremia changes in serial samples. As expected, the automated test was less sensitive than nested PCR; among specimens from a cohort of patients treated with interferon, nested PCR identified three more viremic specimens, which probably contained very low concentrations of HCV RNA.

Clinical significance of hepatitis C virus genotypes

On the basis of phylogenetic analysis of nucleotide sequences, multiple genotypes and subtypes of hepatitis C virus (HCV) have been identified. Characterization of these genetic groups is likely to facilitate and contribute to the development of an effective vaccine against infection with HCV. Differences among HCV genotypes in geographic distributions have provided investigators with an epidemiologic marker that can be used to trace the source of HCV infection in a given population. HCV genotype 1 may represent a more aggressive strain and one that is less likely to respond to interferon treatment than HCV genotype 2 or 3. However, these observations require confirmation before HCV genotyping can be used in clinical settings.

Comparison between three quantitative assays in patients with chronic hepatitis C and their relevance in the prediction of response to therapy

To compare three quantitative assays measuring viral load in patients with chronic hepatitis C and to determine their value in predicting response to interferon (IFN) therapy, we analysed serum from 896 patients from eight European Centres using QUANTIPLEXtrade mark bDNA, MONITOR AMPLICORtrade mark and SUPERQUANTtrade mark assays. Analyses were performed on the same sample. Viral genotype was assessed using INNO-LiPA HCV II kits. Intercentre variations were observed that were related to the handling of specimens not processed and stored within 6 h of blood sampling. Among sera with optimal handling, a stronger correlation was observed between bDNA and SUPERQUANT (0.806) than between bDNA and MONITOR (0.677) and between MONITOR and SUPERQUANT (0.632). These discrepancies were greatest with genotype 2 (bDNA/SUPERQUANT= 0.772; bDNA/MONITOR=0. 456; SUPERQUANT/MONITOR= 0.299). This correlation was influenced by viraemia level and was better at lower viral loads. The proportion of sera with undetectable viral load was 15% with bDNA, 9.7% with MONITOR and 7.7% with SUPERQUANT. For the three measurements, the best cut-offs of sustained response to IFN treatment were located at their detection threshold. Among patients with viral load below the detection level, a sustained response was observed in 35% tested with bDNA, 38% with MONITOR and 80% with SUPERQUANT. Hence a stronger correlation was observed between bDNA and SUPERQUANT than between either of these assays and MONITOR. SUPERQUANT was the most sensitive assay and this greater sensitivity was associated with a better predictive value of treatment response.

Assessment of hepatitis C virus RNA and genotype from 6807 patients with chronic hepatitis C in the United States

Hepatitis C virus (HCV) RNA status and HCV genotype have become important tools in the diagnosis and monitoring of therapy in chronic HCV infection. To establish a database with respect to HCV genotype and serum HCV RNA concentrations in chronic hepatitis C patients in the United States, we analysed 6807 chronic hepatitis C patients who had HCV RNA and HCV genotype tests conducted at a central laboratory. The HCV RNA concentration cut-off for the lower 25th percentile of this population (low titre) was 0.9 x 106 copies ml-1. The median HCV RNA concentration was 3.5 x 106 copies ml-1 and the cut-off for the upper 25th percentile (high titre) was 5 x 106 copies ml-1. Male patients had a median HCV RNA concentration of 3.9 x 106 copies ml-1, which was significantly higher than the median HCV RNA level for females (2.75 x 106 copies ml-1; P < 0.001). HCV genotype 1 was detected in 73% of patients; genotype 2 in 14%; genotype 3 in 8%; mixed genotype in 4%; and genotypes 4, 5 and 6 with a frequency of < 1%. Patients from the Northeast, Southeast and Midwest had significantly (P < 0.001) more infections with genotype 1 than patients from the Western and Southern regions. African-American patients were more likely to be infected with genotype 1 when compared with Caucasian, Hispanic or Asian Pacific Islanders (P < 0.001). Patients infected with HCV genotype 1 and mixed HCV genotypes had significantly higher serum HCV RNA concentrations when compared with HCV genotypes 2 and 3 (P < 0.001 for all comparisons).

Performance of an automated system for quantification of hepatitis C virus RNA

The Amplicor HCV Monitor test for quantitative determination of serum or plasma hepatitis C virus (HCV) RNA was modified recently and introduced onto the Cobas Amplicor instrument to automate fully amplification, detection and calculation of results. This new version (v2.0) was evaluated in a routine diagnostic laboratory. The sensitivity and reproducibility were assessed on well-characterized panels (Eurohep) and clinical samples. HCV RNA levels measured by the v2.0 Monitor test were about 1log(10) higher than those detected by the previous version test, and genotypes 1 and 3 were quantified with equal sensitivity. Within the linear dynamic range of 10(3) to 10(6) copies/ml, the coefficients of variation for both intra- and inter-assay reproducibility ranged from 1.9 to 2.95%. This test system was found to be a reliable and labor saving assay for the quantification of HCV RNA.

Clinical significance of hepatitis C virus genotypes

On the basis of phylogenetic analysis of nucleotide sequences, multiple genotypes and subtypes of hepatitis C virus (HCV) have been identified. Characterization of these genetic groups is likely to facilitate and contribute to the development of an effective vaccine against infection with HCV. Differences among HCV genotypes in geographic distributions have provided investigators with an epidemiologic marker that can be used to trace the source of HCV infection in a given population. HCV genotype 1 may represent a more aggressive strain and one that is less likely to respond to interferon treatment than HCV genotype 2 or 3. However, these observations require confirmation before HCV genotyping can be used in clinical settings.

Routine detection and quantification of hepatitis B virus DNA in clinical laboratories: performance of three commercial assays

The detection and quantification of hepatitis B virus (HBV) genomes in molecular biology-based assays appear to be the most reliable methods for monitoring HBV infection and assessing responses to antiviral treatment. The aim of this study was to evaluate the performance of three HBV-DNA detection and quantification assays currently used for the management of HBV-infected patients: a solution-hybridization assay based on hybrid-capture (Digene Hybrid-Capture, Murex Diagnostics, Dartford, UK); a signal-amplification assay based on 'branched-DNA' (bDNA) technology (Quantiplex HBV DNA, Bayer Diagnostics, Emeryville, CA); and a target-amplification assay based on competitive polymerase chain reaction (Amplicor HBV Monitor, Roche Molecular Systems, Pleasanton, CA). The Monitor assay was significantly more sensitive than both the hybrid-capture and bDNA methods. This better sensitivity appeared to be clinically relevant. The linear ranges of quantification in the hybrid-capture, bDNA and Monitor methods were 6.5-9 log10 genome copies/ml, 6.5-9.5 log10 genome equivalents/ml, and 3-5.5 log10 genome copies/ml, respectively. However, the HBV-DNA units used in the three assays were not comparable. The specificity of the hybrid-capture, bDNA and Monitor assays was 99.2% (95% confidence interval: 97.7-100.0%), 99.2% (97.7-100.0%), and 97.8% (95.3-100%), respectively. Their within-run coefficients of variation and log10 SDs were 5.5% (+/- 0.025 log10 copies/ml), 6.7% (+/- 0.029 log10 Eq/ml) and 21.0% (+/- 0.093 log10 copies/ml), respectively. Between-run coefficients of variation ranged from 4.4-39.1%, 5-39.5%, and 17.8-96.1%, respectively. The competitive PCR-based Monitor assay appears to be significantly more sensitive but slightly less specific and reproducible than the hybrid-capture and bDNA methods. Given their respective performance, these three assays should be used in complementary fashion in the management of HBV-infected patients.

A new step toward standardization of serum hepatitis C virus-RNA quantification in patients with chronic hepatitis C

The need to improve efficacy of antiviral therapy for chronic hepatitis C has prompted the development of quantitative assays, which allows the assessment of viral load before therapy. The aim of our study was to evaluate the clinical relevance of 3 serum HCV-RNA quantitative assays in 87 patients with chronic hepatitis C, the noncommercially available SuperQuant assay (National Genetic Institute), recently used in large international controlled trials, the most early and widely used Quantiplex HCV RNA v2.0 assay (branched DNA [bDNA] v2.0; Bayer Diagnostics, Puteaux, France), and the new generation Cobas Amplicor HCV Monitor assay (COBAS v2.0; Roche Diagnostics Systems, Meylan, France), which is a semiautomated reverse transcription-polymerase chain reaction (RT-PCR) assay. The level and range of quantification were similar between all assays and a strong correlation was observed over all HCV genotypes among the assays. Recent publications have suggested that the baseline cut-off level of 2 x 10(6) copies/mL, as determined by the SuperQuant assay, is able to discriminate between patients with low viral load from those with high viral load and can be used to predict responses to therapy. Because all 3 assays use different testing technologies we examined how many of our patients fell above this defined cut-off level when tested by the other assays; of 22 patients measured below 2 x 10(6) copies/mL with the SuperQuant assay, 17 of 22 and 19 of 22 patients were eligible with the bDNA v2. 0 and the COBAS v2.0 assays, respectively (P >.05). Our results indicate that the 2 commercial assays can be used to determine treatment schedules in patients with chronic hepatitis C, providing a flexibility in multicenter controlled trials by offering better accessibility of test results.

[Viral quantitation of hepatitis C virus: present and future]

INTRODUCTION

Hepatitis C virus (HCV) plasmatic load, also called HCV viremia, is expressed in copies per milliliter or viral particle equivalents per milliliter.

CURRENT KNOWLEDGE AND KEY POINTS

The methods used to measure HCV viremia are based on two principles: the quantitation of viral proteins (measure of antigenemia using monoclonal antibodies), and the quantitation of viral nucleic acid using PCR after reverse transcription (RT-PCR), or signal amplification (branched DNA). There is no relationship between viremia and liver histologic activity.

FUTURE PROSPECTS AND PROJECTS

The use of HCV quantitative viremia in a treatment algorithm, including other factors such as age, genotype, degree of viral genetic heterogeneity, and liver fibrosis score will help adapt therapeutic associations for each individual.

Hepatitis C virus quantitation: optimization of strategies for detecting low-level viremia

A long-term assessment of quantitative hepatitis C virus (HCV) testing was performed at the University of Pittsburgh Medical Center. The Quantiplex HCV RNA 2.0 branched-chain DNA (bDNA) assay (Bayer Diagnostics) for hepatitis C viral load determination was used to test 3,471 specimens. bDNA-negative samples were also tested by an in-house qualitative reverse transcriptase (RT)-PCR assay with a measured sensitivity of fewer than 100 HCV genome equivalents per milliliter. Of 1,239 bDNA-negative specimens, 74.1% were negative and 25.9% were positive by RT-PCR, indicating the presence of viremia in a significant proportion of bDNA-negative samples. We discuss the medical and economic implications of these results and propose two alternatives for clinical laboratories to consider in approaching quantitative HCV testing. For laboratories able to perform a sensitive RT-PCR assay for </=40% of the bDNA test cost, prescreening bDNA requests by RT-PCR may be the most cost-effective approach.

Biological dynamics of viral load in hemodialysis patients with hepatitis C virus

The biological dynamics of hepatitis C virus (HCV) viremia in uremic patients with chronic infection have not been fully characterized. We prospectively studied fluctuations of HCV-RNA in sera from 52 patients with end-stage renal disease who were undergoing maintenance hemodialysis (HD) and had chronic HCV infection. We measured HCV viremia monthly over the course of 13 months with the branched-chain DNA (bDNA) signal amplification assay and prospectively analyzed liver function, expressed by monthly serum aspartate (AST) and alanine aminotransferase (ALT) determinations. We observed three different patterns of HCV viremia: (1) patients persistently positive by bDNA assay (persistent viremia; 23 of 52 patients; 44%), (2) individuals with alternatively positive and negative results (intermittent viremia; 17 of 52 patients; 33%), and (3) patients persistently negative by bDNA assay (12 of 52 patients; 23%). The HCV viral load over the follow-up was greater among patients with persistent compared with intermittent viremia (persistent, 31.7 x 10(5) Eq/mL; range, 6.3 x 10(5) to 16.03 x 10(6) Eq/mL versus intermittent, 10.4 x 10(5) Eq/mL; range, 1.1 x 10(5) to 9.4 x 10(6) Eq/mL; P = 0.0001). In addition, patients with persistent viremia had over time greater AST and/or ALT activities than the intermittent group (AST: persistent, 26.5 IU/L; range, 9.6 to 73.7 IU/L versus intermittent, 21.3 IU/L; range, 8 to 56.8 IU/L; P = 0.001 and ALT: persistent, 14.7 IU/L; range, 3.7 to 57.9 IU/L versus intermittent, 10.9 IU/L; range, 2.3 to 52.1 IU/L; P = 0.001). In the group with persistent viremia, the mean difference between maximum and minimum values of HCV-RNA observed in each individual patient was 2.09 +/- 0.7 natural logarithm (Log(n)) and in intermittent viremic patients, 1.55 +/- 1 Log(n) (P = 0.045). The HCV load at study entry (19.4 x 10(5) Eq/mL) was rather low and did not change versus the end of follow-up in all patients (P = not significant [NS]). In the entire group, the fluctuations in HCV-RNA levels over time between and within individuals were not significant (P = NS). No difference in variability of HCV-RNA values over time between patients infected with different HCV genotypes was seen. In conclusion, three different patterns of HCV viremia in HD over time were assessed; one third of viremic patients had intermittent viremia, and those patients had less HCV-RNA, enzyme-linked immunosorbent assay, and aminotransferase activity than did patients with persistent HCV load. Larger fluctuations in HCV RNA levels occurred in patients with persistent than with intermittent HCV viremia. However, the viremic HCV load was low and relatively stable over a 13-month follow-up in our population. Studies with longer observation periods are warranted to understand fully the natural history of HCV in these immunosuppressed individuals.

Natural fluctuations of hepatitis C viral load in a homogeneous patient population: a prospective study

The aim of this study was to determine the variation in hepatitis C viral load over an extended period of patient follow up. Serum samples were collected from 49 female individuals who were identified as having been infected from the same source of hepatitis C-contaminated anti-D immunoglobulin during the period from 1977 (May) to 1978 (November). All patients attended the hepatitis C clinic at Cork University Hospital, Cork, Ireland. The study group was homogeneous with respect to gender, hepatitis C virus (HCV) genotype (1b), and duration of infection. None of the patients had received antiviral therapy at the time of completion of study. Viral load quantifications were assessed using the Roche Monitor (F. Hoffmann-La Roche, Ltd., Basel, Switzerland) assay. The mean age of the study group at time of infection was 30.3 years (SD +/- 6.1) with a range from 18.5 to 43 years. The mean time of follow-up was 4. 1 years (SD +/- 1.0) with a range from 1.2 to 5 years. The mean rate of change of viral load per year was 0.23 log(10) viral copies per mL serum for the study group (SD +/- 0.19) with a range of -0.18 to 0.78 that was significantly different from zero, P < 10(-10). The rate of change of viral load per year was negatively correlated with viral load at first determination, r = -.35, P =.01. Age at infection did not correlate with the slope of change of viral load, P =.10. In conclusion, most women infected with HCV 1b will have an increase in viral load over time but a few patients who acquire infection early in adult life will show a decrease in viral load.

European multi-centre validation study of NucliSens Extractor in combination with HCV Amplicor 2.0 assay for HCV-NAT screening of plasma pools

The NucliSens Extractor in combination with the 2.0 version of the Roche Cobas HCV Amplicor test has been validated by five European blood screening laboratories in a multi-centre study. For testing the performance characteristics of this HCV-NAT method, the European Pharmacopoeia validation guidelines were followed. The CLB VQC reference reagents were used for testing robustness and sensitivity. After a technical improvement in the extraction stations, the NucliSens Extractor appeared to be contamination-free as was proved by testing negative controls alternating with samples containing a high HCV-RNA concentration. The Pelicheck HCV-RNA genotype 1 dilution panel was tested 74 times in the five laboratories and an overall 95% detection limit of 80 genome equivalents (geq)/ml was found. In one laboratory the Pelicheck panel was tested in 25 runs and here a 95% detection limit of 32 geq/ml was achieved. In this laboratory the Pelispy HCV-RNA run control samples of 140 geq/ml were consistently picked up in all extractor stations. In addition the laboratories have tested a WHO HCV-RNA genotype 1 standard dilution series 39 times and a Pelicheck HCV-RNA genotype 3 reference panel in 32 test runs. The limiting dilution analysis enabled us to compare the detection efficiency of the NucliSens-Amplicor method for the genoype 1 and genotype 3 isolates and to calibrate the reference reagents against each other. The combined Nuclisens-Amplicor method was found to detect the genotype 3 isolate in the Pelicheck HCV-RNA panels with 2-3 fold lower efficiency than the genotype 1 standard (assuming that the historical calibration of the genotype 3 against the genotype 1 standard is correct). In this study of a single method 1 IU of the WHO HCV-RNA standard was found to be equivalent to 5.1 geq of the VQC HCV-RNA standard (95% confidence intervals 3.1-9.1 geq). To avoid confusion with the use of the CLB VQC reagents we accept the NIBSC collaborative study in which calibration by a variety of methods showed that the Pelispy 380 geq/ml run control is equivalent to 100 IU/ml of the WHO standard. This multi-centre validation study demonstrates that the 95% detection limit of the NucliSens HCV Amplicor method lies far below the detection limits required by the international regulatory bodies.

Ribonuclease-resistant RNA Controls (Armored RNA) for Reverse Transcription-PCR, Branched DNA, and Genotyping Assays for Hepatitis C Virus

Background: Comparison and evaluation of molecular diagnostic assays for the detection and quantification of hepatitis C virus (HCV) RNA have been limited by the lack of RNA controls and calibrators. Armored RNA® technology is a means for producing RNA that is completely protected from plasma ribonucleases. This method produces recombinant pseudoviral particles that are noninfectious and contain predefined RNA sequences.

Methods: A consensus 412-base sequence from the 5′NCR/Core region of HCV subtype 2b was derived from 34 individually sequenced HCV genotype 2b variants. A DNA fragment encoding the consensus HCV-2b sequence was synthesized de novo, cloned, and expressed as an Armored RNA control. The resulting HCV-2b Armored RNA (AR-HCV-2b) contained the complete HCV-2b consensus RNA sequence encapsidated within a protective protein coat.

Results: AR-HCV-2b was fully recoverable from human plasma incubated at 4 °C for &gt;300 days. The particles were tested in three clinical assay formats: AmplicorTM HCV Monitor 1.0, QuantiplexTM HCV RNA 2.0, and INNO-LiPATM HCV II. When added into seronegative, nonviremic plasma, AR-HCV-2b showed reproducible signals and linear dilutions in both the Amplicor and Quantiplex assays. AR-HCV-2b was correctly identified as subtype 2b in the INNO-LiPA line probe assay.

Conclusion: The HCV-2b Armored RNA control is a versatile, durable, ribonuclease-resistant viral RNA control that is compatible in three different clinical assay formats.

Molecular methods of measurement of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infection: implications for occupational health practice

Over the past decade, several molecular techniques for the detection of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) have been developed that have implications for occupational health practice. This review describes the techniques used for qualitative and quantitative detection of the viral genome, and briefly explains nucleic acid sequencing and analysis of phylogenetic trees. The review also discusses the current and potential uses of these techniques in investigations of transmission of bloodborne viruses by patient to worker and worker to patient, in the management of occupational exposure to blood, in research, and in the development of guidance and policy on infected healthcare workers who perform procedures prone to exposure.

Clinical application of the Quantiplex HCV RNA 2.0 and Amplicor HCV Monitor assays for quantifying serum hepatitis C virus RNA

AIM

To compare the performance characteristics and clinical application of two different technologies for quantifying serum hepatitis C virus (HCV) RNA levels.

METHODS

HCV RNA was quantified by Amplicor HCV Monitor assay (Amplicor) and Quantiplex HCV RNA 2.0 assay (bDNA-2) in 119 sera from 107 HCV infected patients.

RESULTS

Both assays had similar sensitivity (79.4% for Amplicor; 86.0% for bDNA-2), acceptable coefficients of variation (5.3% in Amplicor; 2.6% in bDNA-2), and good linearity (r2 > or = 0.98). There was a positive correlation between quantification values of both methods (r = 0.683, p < 0.001). The Amplicor values were on an average 1.76 log lower than bDNA-2 results. Male subjects and HCV genotype 1b were significantly associated with higher viral load determined by Amplicor, but not with viral load measured by bDNA-2. In 70 chronic HCV infected patients treated with interferon alfa, mean (SD) pretreatment viral load in 27 complete responders (3.47 (0.84) logs for Amplicor, 5.63 (0.58) for bDNA-2) was significantly lower than in non-responders (4.43 (1.01) logs for Amplicor, 6.10 (0.67) logs for bDNA-2; p < 0.001). Cut off points of 3.9 logs for Amplicor and 5.8 logs for bDNA-2 were determined to be the best for predicting response to interferon alfa, giving acceptable sensitivity (70.4%, 74.1%), specificity (72.1%, 65.1%), and accuracy (71.4%, 68.6%), respectively.

CONCLUSIONS

Both the Amplicor and bDNA-2 assays are clinically useful methods for HCV RNA quantification and are reliable for predicting the outcome of treatment, despite differences in absolute quantification values and in the correlation between HCV genotypes and viral load.

Clinical use of hepatitis C virus tests for diagnosis and monitoring during therapy

This article reviewed various methods used for the diagnosis and monitoring of HCV infection and discusses potential clinical applications. Substantial improvements have recently been made in assay technology. Moreover, the role of molecular testing in the clinical setting of hepatitis C is becoming better defined. The major challenge facing clinical laboratories is the further refinement, implementation, and standardization of optimized molecular tests, so that reliable data may be made available to clinicians. In turn, clinicians must understand the limitations of each methodology, including the variability of testing that may occur among different laboratories. As more experience is gathered, molecular testing will probably provide important data regarding the most effective use of current and future therapies for individual patients to achieve maximum benefit in the management of hepatitis C.

Development and evaluation of quantitative-competitive PCR for quantitation of coxsackievirus B3 RNA in experimentally infected murine tissues

A method is described for quantitation of enterovirus RNA in experimentally infected murine tissues. Viral RNA was extracted from tissue samples and amplified by reverse transcriptase PCR in the presence of an internal standard RNA. The ratio of PCR product derived from viral RNA and internal standard RNA was then determined using specific probes in a post-PCR electrochemiluminescent hybridization assay. This provided an estimate of the viral RNA copy number in the original sample, and detection of PCR product derived from internal standard RNA validated sample processing and amplification procedures. RNA copy number correlated with viral infectivity of cell culture-derived virus, and one tissue culture infective dose was found to contain approximately 10(3) genome equivalents. The ratio of RNA copy number to infectivity in myocardial tissue taken from mice during the acute phase of coxsackievirus B3 myocarditis was more variable ranging from 10(4)-10(7), and was dependent on the stage of infection, reflecting differential rates of clearance for viral RNA and viral infectivity. The assay is rapid, and could facilitate investigations which currently rely upon enterovirus quantitation by titration in cell culture. This would be useful for experimental studies of viral pathogenesis, prophylaxis and antiviral therapy.

Characterization of the quantitative HCV NASBA assay

A quantitative nucleic acid sequence-based amplification assay (NASBA-QT) for detection of hepatitis C virus RNA (HCV-RNA) was evaluated and compared with the HCV branched-DNA (bDNA) assay (Chiron Corporation) and the HCV MONITOR assay (Roche Diagnostic Systems). For this evaluation five panels were designed: (1) serial dilutions of genotype 1b in-vitro HCV-RNA; (2) standards of in-vitro HCV-RNA genotypes 1a, 1b, 2, 3, 4, and 5; (3) a proficiency panel consisting of 12 HCV-RNA positive plasma samples of different genotypes and HCV-RNA concentrations and a genotype 1a and 1b 3-fold dilution series; (4) a panel of 67 HCV-RNA positive plasma samples obtained from patients with HCV infection and (5) an HCV-RNA positive control sample, diluted 50-fold in 25 different HCV-RNA negative plasma samples. The quantitative detection limit was found to be 10(3) copies per 100 microl and the qualitative detection limit 10(2.3) per 100 microl. The amplification efficiency was independent of the plasma matrix, but dependent on the HCV genotype. The HCV NASBA-QT assay was more than 10 times as sensitive as the bDNA assay while the quantitative results of both assays were highly concordant. The HCV NASBA-QT assay was comparable in sensitivity with the HCV MONITOR assay, but the HCV MONITOR assay yielded consistently lower values. It is concluded that the HCV NASBA-QT assay is a reliable assay for quantitative HCV-RNA detection in various settings.

Serum levels of hepatitis C virus RNA in infants and children with chronic hepatitis C

BACKGROUND

The role of serum hepatitis C virus (HCV) load in infectivity, disease activity, and response to interferon treatment has been investigated in adults, and controversial results have been obtained. Little is known about HCV load in infants and children with HCV infection.

PURPOSE

To investigate the relation between HCV load in serum and features of associated liver disease in infants and children with HCV infection.

METHODS

Hepatitis C viral load was investigated in serial samples in 43 children with chronic HCV infection, including 32 patients aged 4 to 16 years infected by different routes and 11 vertically infected infants observed prospectively since birth.

RESULTS

Overall viremia ranged between 2.7 and 6.9 log copies/ml (median, 5.56 log/ml) and fluctuated slightly during the follow-up. Median HCV RNA levels did not significantly differ among infants, children, and adolescents. Viral load was also independent of sex, route of infection, clinical manifestation, alanine aminotransferase levels, and liver histology. All 11 perinatally infected children became chronic HCV carriers, whatever their initial viral load; retrospective testing of sera taken in the first day of life in three infants showed high viremia levels.

CONCLUSIONS

Viremia levels observed in children were similar to those reported in adults, were independent of age, biochemical activity of liver disease, and chronicity of infection. They were also relatively stable, suggesting that serial measurement of viral load is useless in untreated infants and children. The detection of viremia at birth in children in whom chronic hepatitis developed later suggests the possibility of in utero infection.

Genotype dependence of hepatitis C virus load measurement in commercially available quantitative assays

Standardization and genotype independence of methods used to quantify hepatitis C virus (HCV) RNA in clinical specimens are necessary for accurate assessment of the role of HCV quantitation as a prognostic marker for HCV infection and monitoring of the response to antiviral treatment. Commercially available methods used to measure HCV loads include PCR-based (Roche Monitor) and hybridization-based (Quantiplex bDNA-2) methods. Recently, a new version of the Roche Monitor assay (version 2.0) has become available; it has been modified to achieve more equal quantitation of different HCV genotypes. Consistent with previous reports, Roche Monitor version 1.0 substantially underestimated concentrations of RNA transcripts of types 2b, 3a, 4a, 5a, and 6a and virus loads in individuals infected with genotypes 2 to 6 relative to reference tests. However, version 2.0 achieved equivalent quantitation of each genotype over a narrow quantitative range (10(3) to 5 x 10(5) copies of RNA/ml) but significantly underestimated RNA concentrations above this range. The assay showed an equivalent inability to quantify high levels of HCV RNA in plasma samples, and this was responsible for the falsely narrow range of virus loads detected in HCV-infected individuals. In contrast, the Chiron bDNA-2 assay could only measure RNA concentrations in the upper quantitative range (2 x 10(5) to 5 x 10(7) copies of RNA/ml) but showed equivalent sensitivity for genotypes 1 to 5; however, concentrations of type 6a RNA transcripts and virus loads in clinical specimens from individuals infected with type 6a were underestimated by a factor of 2 to 4. Differences were observed between PCR- and hybridization-based assays in their relative quantitation of HCV RNA transcripts and HCV genomic RNA, which may cause problems with the use of transcripts for interassay calibration.

Chronic Hepatitis C Virus Infections in Leukemia Survivors: Prevalence, Viral Load, and Severity of Liver Disease

The natural history of chronic hepatitis C (HCV) infections in long-term leukemia survivors has not been well characterized. We studied the prevalence of HCV infections, measured HCV RNA levels, and evaluated the severity of liver disease in patients with leukemia who achieved long-term remissions after intensive chemotherapy or bone marrow transplantation (BMT). HCV antibody tests were performed by the enzyme-linked immunosorbent assay (ELISA) and positive tests confirmed by the recombinant immunoblot assay (RIBA). HCV RNA levels were measured by the branched DNA (bDNA) assay. Seventy-five leukemia survivors with 25 or more blood donor exposures were identified. Nine (12%) were anti-HCV positive. All were infected before 1992 when second generation HCV screening tests were implemented. Mean HCV RNA levels were 10.3 ×106 eq/mL versus 3.2 × 106 eq/mL (P = .056) in a control group of 20 anti-HCV positive immunocompetent individuals of comparable age who were infected twice as long (17.8 ± 6.5 years v 9.0 ± 4.4 years in leukemia survivors, P = .001). Liver biopsies were performed on six of the nine anti-HCV positive leukemia survivors. All showed at least moderate portal inflammation and half had evidence of bridging fibrosis. We conclude that viral loads in anti-HCV positive leukemia survivors are markedly higher than in immunocompetent controls. Our results suggest that long-term leukemia survivors with chronic HCV may have more rapidly progressive liver disease than has been previously recognized.

Chronic Hepatitis C Virus Infections in Leukemia Survivors: Prevalence, Viral Load, and Severity of Liver Disease

The natural history of chronic hepatitis C (HCV) infections in long-term leukemia survivors has not been well characterized. We studied the prevalence of HCV infections, measured HCV RNA levels, and evaluated the severity of liver disease in patients with leukemia who achieved long-term remissions after intensive chemotherapy or bone marrow transplantation (BMT). HCV antibody tests were performed by the enzyme-linked immunosorbent assay (ELISA) and positive tests confirmed by the recombinant immunoblot assay (RIBA). HCV RNA levels were measured by the branched DNA (bDNA) assay. Seventy-five leukemia survivors with 25 or more blood donor exposures were identified. Nine (12%) were anti-HCV positive. All were infected before 1992 when second generation HCV screening tests were implemented. Mean HCV RNA levels were 10.3 ×106 eq/mL versus 3.2 × 106 eq/mL (P = .056) in a control group of 20 anti-HCV positive immunocompetent individuals of comparable age who were infected twice as long (17.8 ± 6.5 years v 9.0 ± 4.4 years in leukemia survivors, P = .001). Liver biopsies were performed on six of the nine anti-HCV positive leukemia survivors. All showed at least moderate portal inflammation and half had evidence of bridging fibrosis. We conclude that viral loads in anti-HCV positive leukemia survivors are markedly higher than in immunocompetent controls. Our results suggest that long-term leukemia survivors with chronic HCV may have more rapidly progressive liver disease than has been previously recognized.

Development of a simple and highly sensitive enzyme immunoassay for hepatitis C virus core antigen

A highly sensitive enzyme immunoassay (EIA) for the hepatitis C virus (HCV) core antigen (HCVcAg) was developed, and its performance was compared with that of the AMPLICOR HCV test (Roche Molecular Systems). The developed one-step pretreatment method, 30-min incubation of the specimen with a solution containing three different types of detergents (Triton X-100, 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate [CHAPS], and sodium dodecyl sulfate), does not require any special device. Because the interfering anti-core antibody in the sample was sufficiently inactivated by the pretreatment, HCVcAg in the sample could be detected. The immunoreactivity on gel filtration was shifted from void fractions to those corresponding to the molecular mass range from 20 to 25 kDa, which is equal to the estimated molecular mass of HCVcAg, after the pretreatment. By the recovery test with HCVcAg-positive serum, the recovery rate was 93.5 to 106. 5%. There was no interference with the EIA by anticoagulants or blood components in the serum. When the cutoff value was tentatively set at 0.5 mU/ml based on the distribution of healthy subjects' sera, the sera of all healthy subjects (n = 125) and patients with hepatitis B (n = 50) were negative. HCVcAg was detected in sera from 57 of 73 individuals (78.1%) with anti-HCV antibody. Similarly, HCV RNA was detected in sera from 59 individuals (80.8%) with the AMPLICOR HCV as the qualitative test (AMPLICOR HCV test) and in sera from 54 individuals (74.0%) by the AMPLICOR HCV Monitor as the quantitative test (AMPLICOR Monitor test). Concentrations of HCVcAg and HCV RNA (measured by the AMPLICOR Monitor test) correlated significantly (r = 0.8, P < 0.001). On seroconversion panels, HCVcAg was detected during the early stage of infection, when anti-HCV antibodies had not been produced. This assay for HCVcAg is simpler than assays for HCV RNA based on gene technology and shows specificity and sensitivity equivalent to those of the AMPLICOR HCV test.

Comparative study of a modified competitive RT-PCR and Amplicor HCV monitor assays for quantitation of hepatitis C virus RNA in serum

A modified competitive RT-PCR (mcRT-PCR) to measure HCV RNA in serum and the Amplicor HCV Monitor assay were compared. For mcRT-PCR, the RNA extracted was retrotranscribed and coamplified in one step with a known amount of a DNA internal control (IC). Digoxigenin-labeled amplified products were hybridized to specific HCV DNA and IC-DNA probes and quantified by colorimetry. HCV RNA concentration was calculated by plotting the ratio of HCV/IC ODs against a calibration curve. Multiple samples were analyzed in the same round and tedious titration of each sample with a competitor was unnecessary. The mcRT-PCR assay was linear from 6 x 10(3) to 6 x 10(7) copies/ml, whereas Amplicor was linear up to 1-2 x 10(6) copies/ml. HCV RNA was measured in samples from 75 carriers. There was agreement between both methods in type 1 infections but not in type 2 or type 3 infections, in which the values measured by Amplicor were, on average, 15 times lower than those measured by the mcRT-PCR. HCV RNA measured by Amplicor was higher in type 1 infections than in type 2 or 3 infections, but no differences were found when viral load was assessed by mcRT-PCR. The binding efficiency of the Amplicor-probe was greater for type 1 than for types 2 or 3, suggesting Amplicor underestimates the viral load in the latter types. In contrast, the mcRT-PCR is not affected by genotype-related variation of HCV. This study suggests that mcRT-PCR assay is reliable for sensitive and accurate measurement of HCV RNA over a broad range of values independently of the HCV genotype.

Quantification of hepatitis C virus RNA in serum by branched DNA-based signal amplification assays

The objective of the study was to compare the clinical sensitivity and specificity of versions 1.0 and 2.0 of the branched DNA (bDNA)-based hepatitis C virus (HCV) RNA quantification assay, and also to compare the values yielded by the two versions according to the HCV genotype. Serum samples from 268 patients tested routinely by a non-quantitative HCV RNA PCR assay (group A) were tested with version 2.0 of the bDNA assay. Samples from 342 HCV PCR-positive patients with chronic hepatitis C eligible for interferon treatment (group B) were tested with both version 1.0 and version 2.0 of the bDNA assay. Version 2.0 had a clinical sensitivity of 92% (95% confidence interval (CI): 87-97%) in group A and 89% (86-92%) in group B. In group B, the gain in sensitivity with bDNA 2.0 was 16% relative to bDNA 1.0 (P < 0.001). The log values of the two assays correlated with samples positive by both assays (r = 0.83, P < 0.0001), but the distribution of values was larger in samples containing HCV genotypes 2 and 3. The mean ratio of assay 2.0/assay 1.0 values was 1.69 +/- 1.44 (range: 0.33-13.43). The mean ratio was close to 1 with samples containing genotype 1 or 4, but ranged from 0.33 to more than 5. The mean ratio was close to 3 with samples containing genotype 2 or 3, and ranged from 0.5 to more than 13. HCV RNA levels were significantly lower in samples containing genotype 4 than in those containing other genotypes. Sera from 200 anti-HCV-negative, HCV RNA PCR-negative blood donors (group C), and from 164 anti-HCV-negative patients with symptoms of chronic liver disease (group D) were used to assess the clinical specificity of bDNA 2.0. In addition, samples with an HCV RNA titer between 0.2 (assay cutoff) and 0.5 MEq/ml from a group of 546 patients tested routinely for HCV RNA load by bDNA 2.0 (group E) were retested by bDNA 2.0 and by qualitative PCR. The specificity of bDNA 2.0 was 100% (98-100%) in group C and 99% (97-100%) in group D. Among the 41 samples from group E, 38 were positive by bDNA 2.0 retesting (36 were PCR-positive) and three were negative by bDNA 2.0 retesting (all were PCR-positive). It is concluded that version 2.0 of the bDNA assay is markedly more sensitive than version 1.0 and has a good specificity. In contrast with version 1.0, version 2.0 is not influenced by the HCV genotype. The relationship between values obtained with assays 1.0 and 2.0 on clinical specimens is not linear, indicating that HCV RNA titers cannot reliably be calculated from the results of version 1.0.

Linkage of Crohn's disease to the major histocompatibility complex region is detected by multiple non-parametric analyses

BACKGROUND

There is evidence for genetic susceptibility to Crohn's disease, and a tentative association with tumour necrosis factor (TNF) and HLA class II alleles.

AIMS

To examine the potential of genetic linkage between Crohn's disease and the MHC region on chromosome 6p.

METHODS

TNF microsatellite markers and, for some families, additional HLA antigens were typed for 323 individuals from 49 Crohn's disease multiplex families to generate informative haplotypes. Non-parametric linkage analysis methods, including sib pair and affected relative pair methods, were used.

RESULTS

Increased sharing of haplotypes was observed in affected sib pairs: 92% (48/52) shared one or two haplotypes versus an expected 75% if linkage did not exist (p=0.004). After other affected relative pairs were included, the significance level reached 0.001. The mean proportion of haplotype sharing was increased for both concordant affected (pi=0.60, p=0.002) and unaffected sib pairs (pi=0.58, p=0. 031) compared with the expected value (pi=0.5). In contrast, sharing in discordant sib pairs was significantly decreased (pi=0.42, p=0. 007). Linear regression analysis using all three types of sib pairs yielded a slope of -0.38 at p=0.00003. It seemed that the HLA effect was stronger in non-Jewish families than in Jewish families.

CONCLUSIONS

All available analytical methods support linkage of Crohn's disease to the MHC region in these Crohn's disease families. This region is estimated to contribute approximately 10-33% of the total genetic risk to Crohn's disease.

Branched DNA signal amplification for direct quantitation of nucleic acid sequences in clinical specimens

In this chapter I have reviewed the development of bDNA as a method for quantitation of nucleic acid targets and the application of this technology to the study of infectious diseases and cell biology. The ability to quantify viral nucleic acids in clinical specimens has led to a better understanding of the pathogenesis of chronic viral infections such as HIV-1, HCV, and HBV. The information provided by these methods can also be important in the management of patients with these infections. The prognostic value of a single baseline HIV-1 RNA level rivals that surgical staging procedures for cancer, which are among the most powerfully predictive tests in medicine (Mellors et al., 1996). These methods have been used to assess rapidly the effects of antiviral therapy, which has both expedited the development of antiviral drugs and improved the management of patients with HIV-1 and HCV infections. bDNA has several characteristics that distinguish it from the quantitative target amplification systems, including better tolerance of target sequence variability, more direct measurement of target, simpler sample preparation, and less sample-to-sample variation. However, the first- and second-generation bDNA assays lacked sensitivity compared with the target amplifications systems. The changes incorporated into the third-generation assays have effectively increased the signal-to-noise ratio to such a high level that the analytical sensitivity of system 8 bDNA approaches that of PCR. In theory, bDNA can be made even more sensitive by increasing both the sample volume and the signal-to-noise ratio. Nonspecific hybridization can be further reduced by finding more effective blockers for the solid phase or by redesigning the amplifier molecule or the solid phase itself. The increased sensitivity may create new applications for the technology in filter and in situ hybridization assays.

Hepatitis C virus RNA profiles in chronically infected individuals: do they relate to disease activity?

Fluctuations of hepatitis C virus (HCV)-RNA serum levels were monitored in a multicenter study in 76 chronic HCV carriers who had been followed longitudinally without receiving antiviral therapy to assess their relation with the course of liver disease activity. Forty-four patients had normal transaminases over more than 2 years, while 32 additional patients had fluctuating levels. Viral load was measured in serial serum samples prospectively collected for 10 to 12 months in 54 patients and in sera stored yearly up to 8 years in an additional 22 patients. In patients tested monthly, a lesser extent of fluctuations was detected in cases with constantly normal transaminases as compared with those with fluctuating transaminases. In the former group, the mean difference between maximum and minimum values observed in each individual patient was 0.7 Log, while in the latter group, it was 1.3 Log (P =.0004). Most of these patients experienced, on average, three peaks of viremia over 1 year. The range of variation observed upon yearly testing was between 0.2 and 2.2 Log and did not reach statistical significance between the two groups. In conclusion, a careful viral replication profile can be achieved only by monthly testing, because longer time intervals could miss viremia fluctuations. HCV-RNA levels are more stable in asymptomatic HCV carriers than in patients with biochemical activity of liver disease.

Comparative evaluation of hepatitis C virus RNA quantitation by branched DNA, NASBA, and monitor assays

Several studies have shown a relationship between pretreatment hepatitis C virus (HCV) viral load and the response to interferon (IFN) therapy, creating a need for quantitative HCV-RNA assays. Here, we compared three commercial methods: nucleic acid sequence-based amplification NASBA (Organon), branched DNA 2.0 (bDNA) (Chiron), and Monitor (Roche), with reverse-transcription polymerase chain reaction (RT-PCR) as the reference. We assessed sensitivity and reproducibility on a well-characterized panel of sera (EUROHEP), a Chimp Rodney plasma pool, and samples from IFN-treated and -untreated patients with chronic hepatitis C caused by different HCV genotypes. The reproducibility of the NASBA and bDNA methods was slightly better than that of Monitor, especially for genotypes 2 and 4. NASBA had the highest sensitivity (99% vs. 94% and 88% with Monitor and bDNA, respectively), especially for the follow-up of patients on IFN. NASBA gave the highest HCV-RNA concentrations, which were approximately 10-fold more than with the bDNA assay and 100-fold more than with the Monitor kit. The linearity, tested on the chimp Rodney plasma pool, was better with bDNA for high viral load than with NASBA and Monitor, although for low concentration of HCV RNA, bDNA was negative. Pretreatment viral load was lower in patients who had a sustained virological response to IFN, although the bDNA method was not sensitive enough to quantify all pretreatment samples. This study indicates that gene amplification methods (NASBA or Monitor) have better sensitivity than bDNA assays for quantification of HCV RNA in patients with chronic HCV infection, although the bDNA and NASBA methods are more likely to quantify all genotypes. Prospective studies are needed to demonstrate the usefulness of quantitative assays for the follow-up of patients with chronic hepatitis C.

Detection of genomic- and minus-strand of hepatitis C virus RNA in the liver of chronic hepatitis C patients by strand-specific semiquantitative reverse-transcriptase polymerase chain reaction

Studies aimed at correlating the intrahepatic hepatitis C virus (HCV)-RNA level and anatomo-clinical features have been difficult because of sensitivity and specificity shortcomings of available techniques. We titered the genomic- and minus-strand HCV RNAs by a strand-specific, semiquantitative, genotype-independent reverse-transcriptase polymerase chain reaction (RT-PCR) in the liver tissue of 61 patients with chronic hepatitis C. Findings were correlated with the levels of HCV RNA in the serum, the HCV genotype, the expression of intrahepatic HCV antigens, the histological activity (using separate scores for the lobular and the portal/periportal necroinflammatory activity and for the fibrosis), and the response to interferon alfa (IFN-alpha) treatment. Genomic- and minus-strand HCV RNA were detected in 59 and 57 liver specimens, respectively. The HCV-RNA level in the serum correlated with the genomic-strand, but not with the minus-strand, HCV-RNA titer in the liver. No correlations were found between either strand of the intrahepatic HCV RNA and the level of expression of HCV antigens in the liver, or with the grading/staging of the underlying liver disease. The response to IFN-alpha treatment could be predicted by the serum HCV-RNA level and genotype, but not by the intrahepatic level of genomic- or minus-strand HCV RNA. These results suggest that, although the detection of the minus-strand HCV RNA reliably identifies the presence of replicating HCV in its target organ, the quantitative measurement of viremia remains the clinically meaningful "golden standard" for assessing the level of HCV replication.

Sequential serum hepatitis C viral RNA levels longitudinally assessed by branched DNA signal amplification

The aim of this study was to determine the stability of viral load over an extended period in patients with chronic hepatitis C virus (HCV). Sequential serum specimens collected from fourteen non-alcoholic adult patients with chronic HCV between 1990 and 1997 were tested retrospectively for HCV RNA levels by branched DNA assay (Quantiplex HCV RNA 2.0 [Chiron Diagnostics, Emeryville, CA]). A minimum of three serum samples was obtained at various intervals from each patient. None of the patients received antiviral therapy. Liver biopsies, available for 10 of 14 patients, showed mild or moderate hepatitis in seven and cirrhosis in three (one developed cirrhosis during follow-up). RIBA strip immunoassay showed that 7, 3, and 4 patients had viral genotypes 1, 2, and 3, respectively. The follow-up time averaged 5.3 years (range, 3.7 to 6.6 years). Eight patients (57.2%) showed increased viral levels from baseline to follow-up, the remaining six patients (42.8%) showed decreased viral levels. The three cirrhotic patients had the highest viral levels over time. The mean change was a 0.29-fold decrease (median, +1.14 [corrected]; range, -17.49 to +7.32). A less than twofold change in either direction was demonstrated for six patients (42.8%), and a less than threefold change was demonstrated for 10 patients (71.4%). Variation from baseline to last follow-up as calculated by log determination showed that the viremic load varied less than one log10 in all but one individual. These results show that viral load remains relatively stable over prolonged periods in most untreated patients with chronic hepatitis C.

Interferon alfa-2b alone or in combination with ribavirin for the treatment of relapse of chronic hepatitis C. International Hepatitis Interventional Therapy Group

BACKGROUND

Interferon alfa is the only effective treatment for patients with chronic hepatitis C. Forty percent of patients have an initial response to this therapy, but most subsequently relapse. We compared the effect of interferon alone with that of interferon plus oral ribavirin for relapses of chronic hepatitis C.

METHODS

We studied 345 patients with chronic hepatitis C who relapsed after interferon treatment. A total of 173 patients were randomly assigned to receive standard-dose recombinant interferon alfa-2b concurrently with ribavirin (1000 to 1200 mg orally per day, depending on body weight) for six months, and 172 patients were assigned to receive interferon and placebo.

RESULTS

At the completion of treatment, serum levels of hepatitis C virus (HCV) RNA were undetectable in 141 of the 173 patients who were treated with interferon and ribavirin and in 80 of the 172 patients who were treated with interferon alone (82 percent vs. 47 percent, P<0.001). Serum HCV RNA levels remained undetectable 24 weeks after the end of treatment in 84 patients (49 percent) in the combination-therapy group, but in only 8 patients (5 percent) in the interferon group (P<0.001). Sustained normalization of serum alanine aminotransferase concentrations and histologic improvement were highly correlated with virologic response. Base-line serum HCV RNA levels of 2 x 10(6) copies per milliliter or less were associated with higher rates of response in both treatment groups. Viral genotypes other than type 1 were associated with sustained responses only in the combination-therapy group. Combined therapy caused a predictable fall in hemoglobin concentrations but otherwise had a safety profile similar to that of interferon alone.

CONCLUSIONS

In patients with chronic hepatitis C who relapse after treatment with interferon, therapy with interferon and oral ribavirin results in higher rates of sustained virologic, biochemical, and histologic response than treatment with interferon alone.

Screening blood donations for viral genomes: multicenter study of real-time simulation using pooled samples on the model of hepatitis C virus RNA detection

BACKGROUND

The systematic screening for several blood-borne viral genomes in blood donations is a complementary safety measure planned or discussed by the national authorities of several countries.

STUDY DESIGN AND METHODS

To appreciate the feasibility of such screening using pooled samples, a multicenter study of real-time simulation has been performed on the model of hepatitis C virus (HCV) infection. Four blood transfusion center laboratories and two research and diagnosis laboratories simultaneously screened, by several HCV RNA polymerase chain reaction assays, a panel of plasma sample pools of different sizes (500, 100, and 10 samples), collected from HCV-infected or HCV-uninfected blood donors. One viremic plasma was introduced in each pool. HCV RNA was detected by in-house polymerase chain reaction procedures or by standardized manual or semi-automated polymerase chain reaction assays.

RESULTS

The results indicate the feasibility of sample pooling, which renders the screening for viral genomes by molecular biology techniques applicable in the short term and the importance of the experience of laboratory personnel in the use of molecular biology tools.

CONCLUSION

The improvement of standardized assays needs to be continued, and training of laboratory staff members appears to be a crucial step before systematic screening of blood donations for viral genomes by molecular biology techniques can occur.

Effect of interferon therapy on hepatitis C virus RNA in whole blood, plasma, and peripheral blood mononuclear cells

Fifty-two patients with chronic hepatitis C virus (HCV) infection were treated with standard doses of interferon alfa-2b. During treatment, HCV RNA detection was studied in samples of whole blood (WB), plasma (Pl), and peripheral blood mononuclear cells (PBMCs). Individuals were classified as sustained responders (SRs), complete responders with relapse (CRs), partial responders (PRs), or nonresponders (NRs) according to normalization of serum alanine transaminase (ALT) during treatment and follow-up. Before treatment, 100% of WB samples and more than 95% of Pl and PBMC samples were positive for HCV RNA. During treatment, there was progressive clearance of HCV RNA from Pl and PBMCs in SRs and CRs, but CRs had significantly more positive WB samples during and following treatment (P <.0001). At 6 months, only 10% of CR patients were positive by Pl assay, but 50% were positive by WB assay (P <.01). In the PR group, all WB samples remained positive throughout treatment, although 25% to 40% of PBMC and Pl samples became negative for HCV RNA during the first 2 months of therapy (WB > Pl or PBMC; P < .001). However, at later times during treatment most Pl and PBMC samples in the PR group were positive. Samples from the NR group showed no clearance of HCV RNA from WB, Pl, or PBMC fractions. These data document the increased sensitivity of WB assays for detecting HCV RNA in the peripheral blood of patients during interferon therapy. Furthermore, our findings suggest that WB analysis of HCV RNA may be a useful parameter to monitor in determining the end point of interferon therapy.

Mother to child transmission of hepatitis C virus: prospective study of risk factors and timing of infection in children born to women seronegative for HIV-1. Tuscany Study Group on Hepatitis C Virus Infection

OBJECTIVE

To determine the risk factors for and timing of vertical transmission of hepatitis C virus in women who are not infected with HIV-1.

DESIGN

Follow up for a median of 28 (range 24-38) months of babies born to women with antibodies to hepatitis C virus but not HIV-1.

SUBJECTS

442 mothers and babies, of whom 403 completed the study.

MAIN OUTCOME MEASURES

Presence of antibodies to hepatitis C virus and viral RNA and alanine aminotransferase activity in babies. Presence of viral RNA, method of infection with hepatitis C, method of delivery, and type of infant feeding in mothers.

RESULTS

13 of the 403 children had acquired hepatitis C virus infection at the end of follow up. All these children were born to women positive for hepatitis C virus RNA; none of the 128 RNA negative mothers passed on the infection (difference 5%, 95% confidence interval 2% to 7%). 6 children had viral RNA immediately after birth. 111 women had used intravenous drugs and 20 had received blood transfusions. 11 of the infected children were born to these women compared with 2 to the 144 with no known risk factor (difference 7%, 2% to 12%).

CONCLUSIONS

This study suggests that in women not infected with HIV only those with hepatitis C virus RNA are at risk of infecting their babies. Transmission does seem to occur in utero, and the rate of transmission is higher in women who have had blood transfusions or used intravenous drugs than in women with no known risk factor for infection.