Relationship between histological prognosis of chronic hepatitis C and amount of hepatitis C virus core protein in serum

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.

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.

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.

Frequency of gC1qR+CD4+ T cells increases during acute hepatitis C virus infection and remains elevated in patients with chronic infection

CD4+ T cell responses are impaired in chronic HCV infection. To determine factor(s) involved in CD4+ T cell dysregulation, we examined the effect of extracellular core on the alteration of CD4+ T cell responses and the cell surface level of core-binding protein, gC1qR on CD4+ T cells from acute HCV patients with resolved and chronic infection. During the acute phase of infection, the frequency of gC1qR+CD4+ T cells increased in both resolved and chronic HCV infection compared to healthy controls. Notably, 6 months later, the frequency of gC1qR+CD4+ T cells maintained elevated in chronic patients compared to that in resolved patients. In addition, TCR stimulation increased the frequency of gC1qR+CD4+ T cells, resulting in core-induced inhibition of T cell responses in both resolved and chronic patients. These results suggest that HCV infection expands gC1qR+CD4+ T cells, which increase the susceptibility to core-mediated immune dysregulation and facilitate the establishment of HCV persistency.

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.

Comparison of serum hepatitis C virus RNA and core antigen concentrations and determination of whether levels are associated with liver histology or affected by specimen storage time

An enzyme immunoassay has recently been developed for the hepatitis C virus (HCV) core antigen. To evaluate the possible association between core antigen and HCV RNA levels with regards to the change in liver histology over time as well as study the effect of duration of storage on viral load results, sequential sera were analyzed from 45 patients with chronic HCV infection who had undergone two or more liver biopsies. A relatively strong association was found between the core antigen and HCV RNA concentrations (r(s) = 0.8), with a core antigen level of 1 pg/ml corresponding to approximately 1,000 IU/ml. All 42 sera with detectable HCV RNA at the time of the second biopsy had core antigen concentrations above 1 pg/ml, and the three sera without detectable HCV RNA had concentrations below 1 pg/ml. No association was found between HCV RNA or core antigen levels and the stage of fibrosis in biopsy samples, progression of fibrosis, necro-inflammatory grade, steatosis, genotype, alanine aminotransferase level, or alcohol consumption. A significant association was demonstrated between the storage time of the samples and both the HCV RNA and core antigen concentrations. The median log HCV RNA concentrations (international units/milliliter) were 3.92 for the sera obtained at the time of the first biopsy (median storage time, 13.0 years) and 4.41 for the sera obtained at the time of the second biopsy (median storage time, 6.6 years) compared to 5.96, the median for 102 different routine clinical patient samples.

Detection of HCV core antigen in human serum and plasma with an automated chemiluminescent immunoassay

BACKGROUND

Currently, the detection of HCV infection in blood donors relies on the ability of immunoassays to detect circulating HCV antibodies. However, a significant delay exists between the time of infection and the development of antibodies. This delay (window period) can last up to 70 days. The introduction of NAT for the detection of HCV RNA has reduced this window period dramatically. However, NAT is labor intensive, prone to contamination, and expensive as compared with standard serologic tests.

STUDY DESIGN AND METHODS

An automated, microparticle-based chemiluminescent assay for the detection of HCV core antigen in human serum and plasma was developed. The specificity and sensitivity of this prototype assay were evaluated by testing a population of normal blood donors and commercially available seroconversion panels.

RESULTS

The HCV core antigen assay exhibited a 99.9-percent specificity by detecting a single repeatably reactive sample out of 1004 normal donors tested. Assay sensitivity was determined by comparing the HCV core antigen detection rate with the antibody seroconversion profile and the rate of HCV RNA detection. Among 15 seroconversion panels examined, core antigen was detected in 69 of 70 antibody-negative and/or RNA-positive samples for a sensitivity relative to NAT of 98.6 percent.

CONCLUSION

These data indicate that the automated, microparticle-based chemiluminescent HCV core antigen assay can reduce the window period for detection of potentially infected blood donors by 32.7 days, and it represents a viable alternative to HCV RNA testing.