Performance of ORTHO HCV core antigen and trak-C assays for detection of viraemia in pre-seroconversion plasma and whole blood donors

Hepatitis C virus core antigen for screening organ donors and recipients

Organ donors and recipients are routinely screened for hepatitis C virus (HCV) infection, typically via anti-HCV detection. We analyze the utility of an alternative HCV core antigen (HCV-Ag) quantification system, the ARCHITECT HCV Ag Assay, in this setting. We simultaneously tested 315 samples from potential organ donors and recipients using two chemiluminescent microparticle immunoassays: ARCHITECT Anti-HCV and HCV Ag (Abbott, Germany). HCV-Ag was detected in 81 of the serum samples (25.71%) and anti-HCV in 87 (27.62%). Seventy-five of the HCV-Ag-positive samples were positive for anti-HCV (92.59%). Overall concordance between the two assays was 94.29%. Of the six HCV-Ag-positive/anti-HCV-negative patients, five had HCV-Ag values <32 fmol/L, and the sixth had a concentration of 477.50 fmol/L (viral load, 137,000 IU/mL). The HCV AG Assay detects HCV infections missed by the Anti-HCV Assay. Both markers should be used to screen for HCV infection in potential organ donors and recipients.

Utility of enzyme-linked immunosorbent assays to test core antigen in the diagnosis and antiviral therapy management of hepatitis C virus infections

In this study, we evaluate the performance of the enzyme-linked immunosorbent assays (ELISAs) for HCV Ag detection in the diagnosis and antiviral therapy management of HCV infections. For the diagnosis of an active HCV infection, the limit of detection of HCV Ag corresponding to HCV RNA level was approximately 7300 IU/mL; the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of HCV-Ag were 88.96, 100, 100, and 91.33%, respectively. The Pearson's correlation coefficient between HCV Ag and HCV RNA was 0.891. All patients with negative HCV Ag at interferon-α2α/ribavirin therapy week 1 achieved a sustained viral response (SVR), and the PPV was 100%; whereas in patients with positive HCV Ag at therapy weeks 12, the NPV for achieving non-response (NR) was 100%. The results showed that ELISAs for HCV Ag detection could be cost effectively applied to diagnose and evaluate the response to antiviral therapy for HCV infections.

Advances in the Diagnosis and Monitoring of Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection represents a major health problem worldwide. Approximately 350,000 people die every year from hepatitis C related diseases. Antiviral therapy is given to prevent such complications. Advances in serological and molecular assays greatly improved the diagnosis of hepatitis C virus infection and the management of chronically infected patients. Sensitive real-time PCR methods are currently used to monitor the response to antiviral therapy, to guide treatment decisions, and to assess the sustained virological response 24 weeks after the end of therapy. HCV genotyping is part of the pretreatment evaluation. Determination of HCV genotype is important both for tailoring antiviral treatment and for determining treatment duration. It predicts also response to therapy. With the recent introduction of the serine protease inhibitors telaprevir and boceprevir, approved for the treatment of genotype 1 chronic hepatitis C in combination with INF-a and ribavirin, subtyping has become clinically relevant. Indeed, subtypes 1a and 1b may respond differently to current telaprevir-based or boceprevir-based triple therapy. This review summarizes the most recent advances in the diagnosis and monitoring of HCV chronic infection.

Utility of a commercial quantitative hepatitis C virus core antigen assay in a diagnostic laboratory setting

In this study, the utility and impact of hepatitis C virus (HCV) core antigen (Cag) detection via a commercial assay have been evaluated in diagnostic laboratory conditions. In a total of 272 samples from 226 individuals, HCV RNA was detected in 81.3% and anti-HCV antibody prevalence was 86.4%. HCV Cag reactivity was identified in 59.9% of the samples and in 75.8% with detectable RNA. The sensitivity and specificity of HCV Cag assay have been calculated as 75.8% and 95.1%, respectively, and agreement between HCV RNA and HCV Cag was moderate (κ = 0.554). HCV Cag and RNA levels were highly correlated (r = 0.915 and 0.937). A viral load threshold of 10(3) IU/mL has been recognized, above which the correlation with RNA became statistically significant and sensitivity increased to 90.9%. Detection and quantification of HCV core antigen have been observed as a strong alternative to nucleic acid testing for HCV monitorization.

Analytical performance characteristics and clinical utility of a novel assay for total hepatitis C virus core antigen quantification

The detection and quantification of hepatitis C virus (HCV) core antigen in serum or plasma by the use of different assay formats have previously been shown to represent useful markers of viral replication. In the present study, the intrinsic performance characteristics and the potential clinical utility of a novel assay for the quantification of total HCV core antigen were comprehensively assessed by using clinical serum samples and specimens contained in various evaluation panels. The Architect HCV Ag assay showed a specificity of 100%. The intra- and interassay coefficients of variation ranged from 3.6 to 8.0% and from 4.7 to 9.5%, respectively. Except for HCV genotype 2 isolates, the analytical sensitivity was always less than 10 fmol core antigen/liter, corresponding to approximately 500 to 3,000 IU of HCV RNA/ml. Linearity was guaranteed throughout the dynamic range (10 to 20,000 fmol/liter). When seroconversion panels were tested, the assay was not inferior to HCV RNA detection and reduced the preseroconversion period by 4 to 16 days. The results obtained by core antigen and HCV RNA quantification for 385 clinical specimens were correlated by regression analysis (r = 0.857), but the calculated conversion equation differed significantly from the line of identity. Monitoring of viral kinetics by use of either core antigen or RNA concentrations in 38 HCV-infected patients undergoing antiviral combination therapy resulted in very similarly shaped curves in all cases. Finally, the Architect HCV Ag assay was also shown to enable high-throughput screening of in vitro HCV RNA replication. With these results taken together, the Architect HCV Ag assay proved to be a specific, reproducible, highly sensitive, and clinically applicable test format which will find its future place in the context of virological HCV diagnostics.

Analytical evaluation of HCV core antigen and interest for HCV screening in haemodialysis patients

BACKGROUND

It is important to diagnose a hepatitis C virus infection in the acute phase in order to reduce the incidence of this infection in high-risk populations like haemodialysis patients. But detection systems for serum HCV antibodies are insensitive in the acute phase because of the long serological window. Previous studies showed that the HCV core antigen (HCV Ag) may be an alternative to HCV RNA in this context.

OBJECTIVES

To evaluate the performances of the new Abbott ARCHITECT((R)) HCV Ag test and its usefulness in screening for HCV infections in haemodialysis patients.

STUDY DESIGN

The serum HCV Ag titre was compared to the HCV RNA viral load in 98 samples from HCV-infected patients to determine the correlation between the two markers and the influence of genotype. We screened 2752 patients from 37 French haemodialysis units who tested negative for HCV antibodies using the HCV Ag and RNA assays.

RESULTS

The HCV Ag titre was correlated with the HCV RNA (Spearman test coefficient 0.9041, p<0.0001) and all genotypes and subtypes were detected. The HCV Ag and HCV RNA results agreed well for haemodialysis patients. Diagnostic specificity of HCV Ag was high (99.2%) considering HCV RNA as the reference. The two seronegative patients (of 2752) who were HCV RNA positive were also HCV Ag positive.

CONCLUSIONS

The ARCHITECT HCV Ag test is a reliable, highly specific assay for screening acute HCV infections in haemodialysis units. It is a robust alternative to HCV RNA testing.

Early viraemia clearance during antiviral therapy of chronic hepatitis C improves dendritic cell functions

Plasma and cellular HCV RNA and core antigen were tested in monocyte-derived DC (MDDC) from chronic hepatitis C patients undergoing treatment with peg-interferon alpha2b/ribavirin. DC allostimulatory capacity, HCV-specific T-cell reactivity and IL-12 production were measured at baseline and treatment week (TW)12. Using DC and autologous CD4(+)T-cells, obtained at baseline and TW12, we performed cross-over experiments to determine the relative role of DC and/or T-cells for impaired immune reactivity to HCV. HCV RNA and HCV core plasma levels had an impact on DC phenotype and allostimulatory capacity. In contrast, HCV genome/core protein, although detectable in DC from some patients had no effect on DC function. Antiviral immunity at TW12 was not improved in patients who remained HCV RNA positive, while early viraemia clearance (TW12) improved antiviral responses. The cross-over experiment revealed that changes in DC, rather than CD4(+)T cells have a major role for enhanced anti-HCV responses.

Primary screening of blood donors by nat testing for HCV-RNA: development of an "in-house" method and results

An "in-house" RT-PCR method was developed that allows the simultaneous detection of the RNA of the Hepatitis C Virus (HCV) and an artificial RNA employed as an external control. Samples were analyzed in pools of 6-12 donations, each donation included in two pools, one horizontal and one vertical, permitting the immediate identification of a reactive donation, obviating the need for pool dismembering. The whole process took 6-8 hours per day and results were issued in parallel to serology. The method was shown to detect all six HCV genotypes and a sensitivity of 500 IU/mL was achieved (95% hit rate). Until July 2005, 139,678 donations were tested and 315 (0.23%) were found reactive for HCV-RNA. Except for five false-positives, all 310 presented the corresponding antibody as well, so the yield of NAT-only donations was zero, presenting a specificity of 99.83%. Detection of a window period donation, in the population studied, will probably demand testing of a larger number of donations. International experience is showing a rate of 1:200,000 - 1:500,000 of isolated HCV-RNA reactive donations.

Antibodies to a novel antigen in acute hepatitis C virus infections

BACKGROUND

Conformational viral proteins potentially play an important role in the immunobiology of acute hepatitis C virus (HCV) infection and may enable earlier antibody detection.

MATERIALS AND METHODS

HCV RNA was detected using nucleic acid testing. Early antibody production was evaluated using three enzyme immunoassays (EIAs) containing antigenic proteins not present in licensed EIAs. Respectively, these contained: (1) multiple-epitope fusion antigen (MEFA) 7.1-NS3/4a, (2) F and Core, and (3) E1/E2 proteins. NS3/4a is a conformational antigen retaining protease and helicase enzymatic activities. MEFA 7.1 contains the linear epitopes used in licenced EIAs, including the latest EIA-3.0, in combination with genotype 1-3 specific epitopes. Forty-two RNA positive, EIA-3.0 negative samples, including two persistently serosilent cases, were used to evaluate these research EIAs. As controls, 54 EIA-3.0 negative/RNA negative and three HCV RNA+/antibody positive specimens were included.

RESULTS

Only the MEFA 7.1-NS3/4a EIA was positive in seven (17%) of the 42 HCV RNA + specimens, in all three EIA-3.0 positive controls but in none of 54 EIA-3.0 negative/HCV RNA negative controls. Notably, six of the seven (86%) specimens had evidence of active hepatitis (ALT > 210 IU/l). The two serosilent cases were research EIA negative.

CONCLUSION

A novel EIA with conformational and linear epitopes detected HCV antibodies in 17% of viraemic specimens missed by the standard reference EIA-3.0. Our research EIA appears to detect HCV antibodies closer to the initiation of acute hepatitis. Given that the average RNA-positive, antibody-negative window period is 56.4 days, this 17% yield would translate into a 10-day earlier detection of antibodies.

A chemiluminescent, magnetic particle-based immunoassay for the detection of hepatitis C virus core antigen in human serum or plasma

Hepatitis C virus (HCV) exposure in blood donors is determined serologically by the detection of anti-HCV antibodies in serum or plasma. However, a "window" period of 30-70 days after exposure exists where specific antibodies to HCV antigens are not detected. The use of nucleic acid testing for the detection of HCV RNA or antigen testing for the detection of HCV core protein have resulted in dramatic reductions in the pre-seroconversion window period. In this study, an automated HCV core antigen detection test was developed. This magnetic microparticle-based assay utilizes anti-HCV core monoclonal antibody to capture antigen present in human serum or plasma. Captured antigen is then detected using an anti-HCV core monoclonal antibody conjugated with a chemiluminescent compound. The specificity of this assay was established at 99% upon testing a population of normal volunteer blood donors. Sensitivity was determined by testing 16 commercially available HCV seroconversion panels representing genotypes 1a, 1b, 2b, and 3a. In each panel tested, HCV core antigen was detected prior to anti-HCV antibody, resulting in a reduction of the window period by greater than 23 days on average, and greater than 34 days on panels initially NAT negative. In addition, HCV core antigen was detected in >97% of HCV RNA positive/antibody negative specimens, exhibiting sensitivity nearly equivalent to nucleic acid testing in the pre-seroconversion window period for the panels examined.