Quantification of serum hepatitis C virus core protein level in patients chronically infected with different hepatitis C virus genotypes

Ultrasensitive electrochemical detection of hepatitis C virus core antigen using terminal deoxynucleotidyl transferase amplification coupled with DNA nanowires

Early diagnosis of hepatitis C virus (HCV) infection is essential to prevent disease from spreading and progression. Herein, a novel electrochemical biosensor was developed for ultrasensitive detection of HCV core antigen (HCVcAg) based on terminal deoxynucleotidyl transferase (TdT) amplification and DNA nanowires (DNW). After sandwich-type antibody-antigen recognition, the antibody-conjugated DNA was pulled to the electrode surface and further extended into a long DNA sequence by robust TdT reaction. Then, large numbers of methylene blue-loaded DNW (MB@DNW) as signal labels are linked to the extended DNA sequence. This results in an amplified electrochemical signal for HCVcAg determination, typically measured at around -0.25 V (Ag/AgCl). Under the optimum conditions, the proposed biosensor achieved a wide linear range for HCVcAg from 0.1 to 312.5 pg/mL with a low limit of detection of 32 fg/mL. The good practicality of the biosensor was demonstrated by recovery experiment (recoveries from 98 to 104% with RSD of 2.5-4.4%) and comparison with enzyme-linked immunosorbent assay (ELISA). Given the highlighted performance, the biosensor is expected to act as a reliable sensing tool for HCVcAg determination in clinics. Schematic representation of the ultrasensitive electrochemical biosensor based on terminal deoxynucleotidyl transferase (TdT) amplification linked with methylene blue-loaded DNA nanowires (MB@DNW), which can be applied to the determination of hepatitis C virus core antigen (HCVcAg) in clinical samples. dTTPs, 2'-deoxythymidine 5'-triphosphate.

Chronic Hepatitis C Virus Infection Impairs M1 Macrophage Differentiation and Contributes to CD8+ T-Cell Dysfunction

Chronic hepatitis C virus (HCV) infection causes generalized CD8+ T cell impairment, not limited to HCV-specific CD8+ T-cells. Liver-infiltrating monocyte-derived macrophages (MDMs) contribute to the local micro-environment and can interact with and influence cells routinely trafficking through the liver, including CD8+ T-cells. MDMs can be polarized into M1 (classically activated) and M2a, M2b, and M2c (alternatively activated) phenotypes that perform pro- and anti-inflammatory functions, respectively. The impact of chronic HCV infection on MDM subset functions is not known. Our results show that M1 cells generated from chronic HCV patients acquire M2 characteristics, such as increased CD86 expression and IL-10 secretion, compared to uninfected controls. In contrast, M2 subsets from HCV-infected individuals acquired M1-like features by secreting more IL-12 and IFN-γ. The severity of liver disease was also associated with altered macrophage subset differentiation. In co-cultures with autologous CD8+ T-cells from controls, M1 macrophages alone significantly increased CD8+ T cell IFN-γ expression in a cytokine-independent and cell-contact-dependent manner. However, M1 macrophages from HCV-infected individuals significantly decreased IFN-γ expression in CD8+ T-cells. Therefore, altered M1 macrophage differentiation in chronic HCV infection may contribute to observed CD8+ T-cell dysfunction. Understanding the immunological perturbations in chronic HCV infection will lead to the identification of therapeutic targets to restore immune function in HCV+ individuals, and aid in the mitigation of associated negative clinical outcomes.

Hepatitis C virus (HCV) Infection Rate among Seronegative Hemodialysis Patients Screened by Two Methods; HCV Core Antigen and Polymerase Chain Reaction

BACKGROUND

End-stage renal disease patients on chronic hemodialysis are among high risk groups for hepatitis C virus (HCV) infection for whom routine HCV screening is recommended. Anti-HCV antibody (ab) testing may not be reliable to detect all infected cases because of the blunted ab response due to depressed immune state in these patients. Using a more reliable, cost-effective and non-complex HCV screening test may be necessary in this group of patients for case finding and management, and also for prevention of infection spread.

OBJECTIVES

The aim of this study was to find the prevalence of HCV infection in HCV ab negative hemodialysis patients by Real time PCR and total HCV core antigen (ag) test and comparing the results of the two tests.

PATIENTS AND METHODS

From a single hemodialysis center, 181 anti- HCV ab negative patients were screened by total HCV core ag using an ELISA kit. Real time PCR was used for determination of the virus and viral load quantity.

RESULTS

Among the 181 anti-HCV ab negative patients, 13 (7.2%) were positive for HCV core ag and 11 (6%) had detectable HCV RNA with a range of 40-336543 IU/ml by PCR. The two tests had a high measurement agreement (Kappa=0.82, P<0.001). Of the 13 patients with positive HCV core ag test results, 3 were negative for HCV RNA. Considering real time PCR for HCV RNA as the gold standard for HCV infection determination in this patient population, HCV core ag assay yielded a sensitivity of 90.9%, specificity of 98.2%, positive predictive value of 76.9% and negative predictive value of 99.4%.

DISCUSSION

The rate of HCV infection among HCV ab negative hemodialysis patients was high. HCV core ag testing could be used as a sensitive method for HCV infection screening in this group of patients.

Performance of two Real-Time RT-PCR assays for quantitation of hepatitis C virus RNA: evaluation on HCV genotypes 1-4

Accuracy for monitoring of the concentration of hepatitis C virus (HCV) RNA represents a major challenge throughout the management of patients with chronic hepatitis C. To investigate the genotype-independent efficiency and the accuracy of two real-time detection reverse transcription-polymerase chain reaction (RT-PCR) assays; the Cobas Ampliprep/Cobas TaqMan (CAP/CTM); and the Abbott RealTime HCV (ART), a total of 184 samples with different HCV subtypes were examined; 1b (n=58), 2a (n=39), 2b (n=26), 3a (n=20), and 4 (n=41). A robust linear correlation was observed between the two assays applied to genotypes 1b, 2a, 2b, and 3a [the correlation coefficient (R) ranged from 0.99 to 0.98], but not to genotype 4 specimens (R=0.78). A significant difference in measurements of HCV RNA using CAP/CTM and ART in serum samples with genotypes 1b and 4 was observed (0.72, -0.53 log IU/ml, P<0.0001, 0.01, respectively). A robust correlation was observed between the HCV core antigen and HCV RNA values by either of the HCV RNA quantitation assays applied to all genotypes with exception of genotype 4, for which R was higher with ART (R=0.95) than with CAP/CTM (R=0.80). The lower limit of detection of CAP/CTM and ART were 41.4 and 28.5 IU/ml using the WHO standards, respectively. In conclusion, two RT-PCR assays had a high efficiency and accuracy for quantitation of HCV RNA of genotypes 2a, 2b, and 3a, but the mean values of HCV RNA differed for genotype 1b and 4.

Detection of hepatitis C virus core antigen for early diagnosis of hepatitis C virus infection in plasma donor in China

AIM: To evaluate the efficacy of a new hepatitis C virus (HCV) core antigen assay developed in China.

METHODS: After the determination of HCV infection, 49 serial samples were selected from 11 regular plasma donors in 5 different plasma stations. To compare the performance of HCV core antigen detection and HCV PCR, these samples were genotyped, and each specimen was analyzed by ELISA for the detection of HCV core antigen and by qualitative HCV PCR.

RESULTS: Among all of the sequential samples, the original 13 specimens were HCV RNA-negative, and 36 samples were HCV RNA-positive. Twenty-seven samples (75%) were HCV core antigen-positive from these HCV RNA-positive specimens. Conversely, 27 samples (93.1%) were found HCV RNA-positive in HCV core antigen-positive samples. Intervals between HCV RNA and HCV core antigen-positive, as well as between HCV core antigen-positive and HCV antibody-positive were 36.0 and 32.8 d, respectively.

CONCLUSION: This HCV core antigen assay, developed in China, is able to detect much of anti-HCV-negative, HCV RNA-positive preseroconversion window period (PWP) plasma donations.

Circulating viral core and E1 antigen levels as supplemental markers for HCV chronic hepatitis

The performance of polyclonal monospecific rabbit anti-sera raised against synthetic peptides derived from conserved HCV sequences of genotype 4 was evaluated for efficient detection of viral core and E1 antigens in circulating immune complexes (ICs) precipitated from 65 serum samples of HCV patients. The infection was established in those patients by the presence of HCV RNA in their sera. A novel enzyme-linked immunosorbent assay (ELISA) was developed for the detection of HCV core and E1 antigen in serum samples. Western blot analyses were used to demonstrate the presence of the core and E1 target antigen in serum samples. The mean OD readings of both core and E1 antigens were significantly higher (P < 0.05) among the viremic patients when compared to controls. Also a significant positive correlation (P < 0.05, r = 0.98) between the values of both core and E1 was recorded. Western blot analysis based on monospecific antibodies against core and E1 recognized the 38-kDa and 88 -kDa bands respectively in the sera of all infected patients. No specific reaction was observed with the sera from uninfected individuals. Interestingly the results of core and E1 antigen levels displayed no positive correlation with the HCV copy number as measured by bDNA. Liver enzymes (ALT and AST) showed a moderate positive correlation (r = 0.44 and 0.47 respectively) with the viral core antigens level. The same trend holds true for E1 (r = 0.43 and 0.64 for ALT and AST respectively). HCV load in infected patients revealed extremely poor correlation with serum ALT and AST levels (r = 0.022 and 0.002 respectively). In conclusion we present a new combination of serological tools correlating with liver enzyme levels that could be utilized as supplemental tests to viral load testing. Also, a sensitive and specific immunoassay was developed for the detection of HCV core and E1 in human serum. This test can be applied for laboratory diagnosis of HCV infection.

Circulating viral core and E1 antigen levels as supplemental markers for HCV chronic hepatitis

The performance of polyclonal monospecific rabbit anti-sera raised against synthetic peptides derived from conserved HCV sequences of genotype 4 was evaluated for efficient detection of viral core and E1 antigens in circulating immune complexes (ICs) precipitated from 65 serum samples of HCV patients. The infection was established in those patients by the presence of HCV RNA in their sera. A novel enzyme-linked immunosorbent assay (ELISA) was developed for the detection of HCV core and E1 antigen in serum samples. Western blot analyses were used to demonstrate the presence of the core and E1 target antigen in serum samples. The mean OD readings of both core and E1 antigens were significantly higher (P < 0.05) among the viremic patients when compared to controls. Also a significant positive correlation (P < 0.05, r = 0.98) between the values of both core and E1 was recorded. Western blot analysis based on monospecific antibodies against core and E1 recognized the 38-kDa and 88 -kDa bands respectively in the sera of all infected patients. No specific reaction was observed with the sera from uninfected individuals. Interestingly the results of core and E1 antigen levels displayed no positive correlation with the HCV copy number as measured by bDNA. Liver enzymes (ALT and AST) showed a moderate positive correlation (r = 0.44 and 0.47 respectively) with the viral core antigens level. The same trend holds true for E1 (r = 0.43 and 0.64 for ALT and AST respectively). HCV load in infected patients revealed extremely poor correlation with serum ALT and AST levels (r = 0.022 and 0.002 respectively). In conclusion we present a new combination of serological tools correlating with liver enzyme levels that could be utilized as supplemental tests to viral load testing. Also, a sensitive and specific immunoassay was developed for the detection of HCV core and E1 in human serum. This test can be applied for laboratory diagnosis of HCV infection.

Evaluation of clinical usefulness of second-generation HCV core antigen assay: comparison with COBAS AMPLICOR HCV MONITOR assay version 2.0

BACKGROUND

Hepatitis C virus (HCV) is an important etiologic agent for chronic liver diseases.

METHODS

The aim of this study was to evaluate the clinical usefulness of second-generation HCV core antigen assay by comparing the results of the assay with those of the COBAS AMPLICOR HCV MONITOR version 2.0 (COBAS v2.0).

RESULTS

HCV core antigen was detectable by this assay in 142/149 (95.3%) of serotype 1 (3821+/-322 fmol/l; mean+/-SD), in 56/58 (96.6%) of serotype 2 (2589+/-449 fmol/l), and in 6/6 (100%) of serotypes 1+2 (1240+/-548 fmol/l). The HCV core antigen levels measured by this assay correlated well with the HCV RNA levels by COBAS v2.0 (r=0.848, P<0.0001). In relation to the outcome of interferon monotherapy, the pretreatment HCV core antigen levels of sustained and non-sustained virological responders were 659+/-189 and 4904+/-376 fmol/l in serotype 1, 1993+/-740 and 3145+/-519 fmol/l in serotype 2. The cutoff values with the best accuracy for HCV core Ag levels to discriminate between sustained and non-sustained virological response were 699 fmol/l for serotype 1 and 292 fmol/l for serotype 2, respectively, by receiver operating characteristic curve analysis.

CONCLUSION

This new assay was considered to be useful in evaluating the HCV levels in patients with chronic hepatitis C.

Use of virologic assays in the diagnosis and management of hepatitis C virus infection

This article discusses the use of virologic assays in the diagnosis and management of hepatitis C virus (HCV) infection. The use of virologic tests has become essential in the management of HCV infection to diagnose HCV infection, guide treatment decisions, and assess the virologic response to antiviral therapy. The continuing development of test systems accompanied by new antiviral drugs and novel therapeutic approaches should lead to an optimization of the treatment of HCV infection.

De novo HCV infection among dialysis patients: a prospective study by HCV core antigen ELISA assay

BACKGROUND

Dialysis patients remain a high-risk group for hepatitis C virus infection. The current diagnosis of hepatitis C virus in dialysis patients includes serological measurement of anti-hepatitis C virus antibody; however, nucleic acid amplification technology for assessing hepatitis C virus viraemia is commonly used in other populations. An enzyme-linked immunosorbent assay test for detecting antibody to hepatitis C nucleocapsid core antigen (hepatitis C virus core antigen) in human serum has been recently developed (hepatitis C virus Core Antigen enzyme-linked immunosorbent assay test). It is conceived for screening of donor blood products to significantly reduce the 'serologic window' occurring before seroconversion during acute hepatitis C virus.

AIM AND METHODS

A cohort (n = 72) of patients on maintenance haemodialysis in a single unit in the years 2000-2003 was included. Study patients were tested monthly by hepatitis C virus Core Antigen enzyme-linked immunosorbent assay in a prospective, clinical trial. Routine results obtained by hepatitis C virus Core Antigen enzyme-linked immunosorbent assay test were confirmed by assessing hepatitis C virus viraemia by branched-chain DNA (bDNA) signal amplification assay.

RESULTS

De novo hepatitis C virus infection was identified in three patients during the study period; the hepatitis C virus incidence was 1.38% (95% confidence intervals, 1.31-4.09) per year. In each patient, hepatitis C virus core antigen testing allowed the serological identification of acute hepatitis C virus before anti-hepatitis C virus seroconversion. Hepatitis C virus RNA testing confirmed the results obtained by hepatitis C virus Core Antigen enzyme-linked immunosorbent assay in all cases. The time from initial hepatitis C virus detection by hepatitis C virus Core Antigen Assay and anti-hepatitis C virus seroconversion was not greater than four weeks. Two (67%) of three patients with de novo hepatitis C virus acquisition were HBsAg negative; both these patients underwent an initial phase of hepatitis C virus viraemia that was associated with an increase in alanine aminotransferase activity and preceded the seroconversion to anti-hepatitis C virus antibody. Nosocomial transmission of hepatitis C virus between haemodialysis patients was implicated in at least two (67%) of these three patients.

CONCLUSIONS

Serological testing for hepatitis C virus core antigen can identify acute hepatitis C virus infection before anti-hepatitis C virus seroconversion. The time from initial hepatitis C virus detection by hepatitis C virus core antigen assay and anti-hepatitis C virus seroconversion was not >4 weeks. De novo acquisition of hepatitis C virus in haemodialysis was associated with a rise in alanine aminotransferase levels. Hepatitis C virus core antigen enzyme-linked immunosorbent assay test results can be obtained in routine laboratories without the need of special equipment or training. Hepatitis C virus core antigen testing among anti-hepatitis C virus negative patients on maintenance dialysis is suggested in order to early assess de novo hepatitis C virus within dialysis units.

The role of core antigen detection in management of hepatitis C: a critical review

Several assays in research format and two commercial assays for the detection of hepatitis C virus (HCV) core protein or HCV core antigen have been developed in recent years. In order to elucidate the role and significance of HCV core antigen detection in the diagnosis and management of hepatitis C, we reviewed 56 studies published in peer-reviewed journals until September 2004. Evaluations in transfusion settings showed that the HCV core antigen assay detects HCV infection, similarly as nucleic acid techniques (NAT), between 40 and 50 days earlier than the current third generation HCV antibody screening assays. HCV core antigen levels closely track HCV RNA dynamics, and allow clinical monitoring of a patient's therapy, independently of HCV genotype, however, mainly in the samples with HCV RNA levels above 20,000 IU/ml. Considering the lower sensitivity of HCV core antigen detection in comparison to NAT, the HCV core antigen assay is not practical for the determination of the end of treatment response and sustained viral response, but could be useful for the determination of early viral response in the pegylated interferon-alpha and ribavirin treated patients infected with HCV genotype 1. The HCV core antigen detection is a viable tool for study of hepatitis C pathogenesis. The HCV core antigen can be used as a marker of HCV replication in anti-HCV positive individuals in the areas of the world that cannot afford NAT and/or in the settings that are not equipped or competent to perform HCV RNA testing. Because the manufacturer of HCV core antigen assays recently stopped an active marketing of these assays in several countries, it will, unfortunately and probably, never be possible to determine the actual potential and usefulness of HCV core antigen testing in the management of hepatitis C.

Usefulness of a new immuno-radiometric assay to detect hepatitis C core antigen in a community-based population

A new immuno-radiometric assay (IRMA) to detect hepatitis C virus (HCV) core antigen (HCVcAg) has been developed. The aim of the present study was to investigate the sensitivity and specificity of this IRMA to measure HCV antigenemia, based on the detection of HCV RNA as the gold standard, and to assess the utility of the IRMA in a community-based population. Anti-HCV positive residents in a hyperendemic area of HCV infection in Japan were studied. Serum levels of HCVcAg were measured using IRMA, and the presence of HCV RNA was determined by a qualitative reverse transcription-polymerase chain reaction (RT-PCR) assay. The sensitivity and the specificity of the IRMA were 96.4 and 100%, respectively. The sensitivity of the IRMA was similar between serological HCV group I (HCV genotypes 1a and 1b) (97.6%) and group II (HCV genotypes 2a and 2b) (94.0%). There was a strong correlation between serum HCVcAg level and HCV-RNA measured by a quantitative RT-PCR (r = 0.832, P < 0.0001). There also was a very strong correlation of HCVcAg level between IRMA measurements performed on serum and those performed on plasma (r = 0.984, P < 0.0001). In conclusion, this new IRMA is useful for the detection of HCV core antigen in a community-based population.

Novel assay using total hepatitis C virus (HCV) core antigen quantification for diagnosis of HCV infection in dialysis patients

Dialysis patients remain a high-risk group for hepatitis C virus (HCV) infection. The current diagnosis of HCV infection among dialysis patients includes serological assays and nucleic acid amplification technology (NAT) for assessing serum anti-HCV antibody and HCV viremia, respectively. However, current NAT techniques are expensive and labor-intensive and often lack standardization. An assay prototype designed to detect and quantify total HCV core antigen (total HCV core Ag) protein in serum and plasma in the presence or absence of anti-HCV antibodies has been recently developed. A comparison between a total anti-HCV core Ag enzyme-linked immunosorbent assay (ELISA) and a quantitative HCV RNA assay based on reverse transcription-PCR (RT-PCR) (Amplicor HCV Monitor test) was performed using a large (n = 305) cohort of ELISA HCV 3.0 HCV-negative and -positive patients on maintenance dialysis. The concentrations of HCV core Ag and HCV RNA levels (measured by RT-PCR) were significantly correlated (r = 0.471, P = 0.0001) over a wide range of HCV RNA levels and were maintained among different HCV genotypes (HCV genotype 1, r = 0.862, P = 0.0001; HCV genotype 2, r = 0.691, P = 0.0001). We estimated that 1 pg of total HCV core Ag per ml is equivalent to approximately 19.952 IU of HCV RNA per ml, even if the wide range in the ratio of core Ag to HCV RNA (95% confidence intervals, 2.8 x 10(3) to 1.6 x 10(5) IU/ml) precluded definitive conclusions. In summary, total HCV core Ag proved to be useful for performing HCV RNA measurement among dialysis patients in routine laboratories without the need for special equipment or training. The present study supports the use of the total anti-HCV core Ag ELISA for assessing viral load among dialysis patients with HCV infection.

Application of a new enzyme-linked immunosorbent assay for detection of total hepatitis C virus core antigen in blood donors

Recent studies have shown that total hepatitis C virus (HCV) core antigen, both free and antibody bound, is an accurate indirect marker of viral replication that can be used in clinical practice. The aim of the present study was to evaluate the performance of a new total HCV core antigen enzyme-linked immunosorbent assay (ELISA) for detection and quantification of total core antigen in blood donors, testing positive for anti-HCV antibodies and for prospective low-risk population screening. A population comprising 257 samples, from blood donors detected reactive for anti-HCV antibodies [137 recombinant immunoblot assay (RIBA) positive and 120 RIBA indeterminate], were tested by using a new total HCV core antigen ELISA. HCV-RNA was quantified by using quantitative polymerase chain reaction (PCR) assays in all RIBA-positive samples and RIBA-indeterminate samples that were positive for the total core antigen. Specificity of the assay was studied in 1070 healthy blood donors negative for anti-HCV antibodies. Compared with quantitative PCR assays, the total HCV core antigen assay showed 97.37% sensitivity. The three HCV-RNA-positive samples, which tested negative for the total core antigen, had a low viral load (< 1.4 x 10(4) IU mL(-1)). All samples with more than 1.4 x 10(4) IU mL(-1) of viral RNA were positive for total core antigen, independent of the HCV genotype. Concentration of total core antigen correlated significantly with those of HCV-RNA (r = 0.614, P < 0.0001). Overall specificity in freshly collected blood donor specimens was 99.63%. Our data indicate that the total HCV core antigen ELISA has a sensitivity close to PCR assays in diagnosing HCV infection in blood donors with anti-HCV antibodies and shows an excellent specificity in volunteer donors. This assay, in combination with anti-HCV antibodies screening tests, could be an alternative to molecular assays for HCV infection screening in blood donors.

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

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

Clinical utility of total HCV core antigen quantification: a new indirect marker of HCV replication

Hepatitis C virus (HCV) RNA detection, viral load quantification, and HCV genotyping are widely used in clinical practice. Recently, the availability of an anticore antigen (Ag) monoclonal antibody allowed development of an enzyme-linked immunosorbent assay (ELISA) detecting and quantifying total HCV core Ag in peripheral blood of HCV-infected patients. The aims of the present study were to investigate the biologic significance of this new marker in HCV infection, to establish the intrinsic performance of the current assay, and to determine its potential utility in the management of HCV-infected patients. A panel of infected sera calibrated to the World Health Organization International Standard and 657 serum samples from infected patients receiving antiviral treatment were studied. We showed that total HCV core Ag quantification is an accurate, precise, and specific indirect marker of HCV replication. We estimated that 1 pg/mL of total HCV core Ag is equivalent to approximately 8,000 HCV RNA international units (IU)/mL, although minor between-patient differences may exist. In conclusion, total HCV core Ag quantification can be used in the various indications of viral load monitoring, including the evaluation of baseline viral load before therapy, the assessment of the virologic response to antiviral treatment, and the study of early viral kinetics during therapy. Nevertheless, the total HCV core Ag assay cannot be used as a marker of viral replication for HCV RNA values below 20,000 IU/mL, limiting its use in the monitoring of late events during and after antiviral treatment.

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.

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

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

Novel approach to reduce the hepatitis C virus (HCV) window period: clinical evaluation of a new enzyme-linked immunosorbent assay for HCV core antigen

The window period in hepatitis C virus (HCV) infection is still a major problem in ensuring blood safety. HCV RNA detection by nucleic acid amplification technology-based tests has contributed to reduce the infectivity of blood products, but it is expensive, time-consuming and affected by a high prevalence of false-positive results. The aim of this study was to assess the performance of a newly developed enzyme immunoassay for the detection of HCV core antigen and its suitability for use in the screening of blood units in order to identify infecting samples that do not contain specific antibodies. For evaluation of laboratory performance, different samples were selected: to evaluate specificity, we tested 2,586 sera from blood donors, 500 general population samples, and 58 "difficult sera". All samples were tested by two screening assays, and results were negative. To estimate clinical sensitivity, 103 HCV RNA-positive, anti-HCV-negative samples, 6 natural seroconversion panels, and 9 commercial seroconversion panels were tested. Intra- and interassay precision were determined on two HCV-RNA-positive, anti-HCV-negative sera. Seventeen (0.66%) blood donor samples, 2 (0.4%) general population samples, and 2 (3.44%) difficult sera were initially reactive; 3 sera were positive on repetition. These 21 samples tested by reverse transcription-PCR were negative. The clinical sensitivity calculated with seroconversion panels and seroconverted patient samples was very similar to PCR sensitivity: 95% of PCR-positive, antibody-negative samples contained detectable HCV antigen. Data on intra- and interassay precision showed dispersion indices with values of less than 10%. In conclusion, the HCV antigen assay showed high sensitivity and specificity and could become a useful means of improving the safety of blood and blood products.

Nonenveloped nucleocapsids of hepatitis C virus in the serum of infected patients

One of the characteristics of hepatitis C virus (HCV) is the high incidence of persistent infection. HCV core protein, in addition to forming the viral nucleocapsid, has multiple regulatory functions in host-cell transcription, apoptosis, cell transformation, and lipid metabolism and may play a role in suppressing host immune response. This protein is thought to be present in the bloodstream of the infected host as the nucleocapsid of infectious, enveloped virions. This study provides evidence that viral particles with the physicochemical, morphological, and antigenic properties of nonenveloped HCV nucleocapsids are present in the plasma of HCV-infected individuals. These particles have a buoyant density of 1.32 to 1.34 g/ml in CsCl, are heterogeneous in size (with predominance of particles 38 to 43 or 54 to 62 nm in diameter on electron microscopy), and express on their surface epitopes located in amino acids 24 to 68 of the core protein. Similar nucleocapsid-like particles are also produced in insect cells infected with recombinant baculovirus bearing cDNA for structural HCV proteins. HCV core particles isolated from plasma were used to generate anti-core monoclonal antibodies (MAbs). These MAbs stained HCV core in the cytoplasm of hepatocytes from experimentally infected chimpanzees in the acute phase of the infection. These chimpanzees had concomitantly HCV core antigen in serum. These findings suggest that overproduction of nonenveloped nucleocapsids and their release into the bloodstream are properties of HCV morphogenesis. The presence of circulating cores in serum and accumulation of the core protein in liver cells during the early phase of infection may contribute to the persistence of HCV and its many immunopathological effects in the infected host.

Evaluation of quantitative measurements of hepatitis C virus RNA to predict sustained response to interferon by genotype

Hepatitis C virus (HCV) virus load is one of the most important predictive factors for the outcome of interferon (IFN) therapy. Recent technological advances have allowed a more precise measurement of HCV load. However, the exact cutoff values that could be used to predict the outcome of IFN have not been established for each assay. Five recent quantitative assays were evaluated for the measurement of HCV (Amplicor monitor ver 1.0, Amplicor monitor ver 2.0 (GT), Amplicor monitor ver 2.0 (Cobas), Quantiplex branched DNA amplification (bDNA) ver 2.0 and HCV core protein level by enzyme immunosorbent assay) in 209 consecutive patients with chronic hepatitis C, who received IFN therapy. The results of the two second generation Amplicor monitor tests (GT and Cobas) showed the best correlation (r = 0.930), but the other tests also showed relatively good correlations (r = 0.646-0.925). Each method predicted the effect of IFN with comparable predictive efficacy, ranging from 77.0 to 80.8%. Receiver operating characteristic (ROC) curve analysis showed that Amplicor monitor ver 2.0 and bDNA ver 2.0 are superior in predicting the response in genotype 2a. The best cutoff value for predicting the response to IFN was different by genotype, which should be considered in selecting candidates for IFN treatment.

Efficacy of a hepatitis C virus core antigen enzyme-linked immunosorbent assay for the identification of 'window-phase' blood donations

BACKGROUND AND OBJECTIVES

Recent studies have suggested that potentially infectious donations provided during the antibody-negative 'window' phase of hepatitis C virus (HCV) infection may be identified by testing for viral RNA or HCV core protein. We therefore evaluated the performance of an HCV antigen enzyme-linked immunosorbent assay (ELISA) for identification of window-phase donations and for prospective screening of blood donors.

MATERIALS AND METHODS

One-hundred and twenty-eight archived plasma donations containing HCV RNA, but lacking antibody to HCV (anti-HCV), were tested by using the HCV antigen ELISA, together with 9951 freshly collected serum and plasma specimens from blood donors.

RESULTS

HCV core antigen was detected in 94% (120/128) of window-phase plasma donations. Overall specificity in freshly collected blood donor specimens was 99.74%. Two putative window-phase donations containing HCV core protein and viral RNA were identified from paid plasma donors by prospective testing with the HCV antigen ELISA.

CONCLUSION

These results indicate that an HCV antigen ELISA can identify almost all (94%) of viraemic donations given during the seronegative window phase of infection. The performance of the HCV antigen ELISA appears to be suitable for large-scale screening of blood donations.

Leptin has no role in determining severity of steatosis and fibrosis in patients with chronic hepatitis C

OBJECTIVE

The presence of steatosis is a common histological finding in patients with chronic hepatitis C (CHC). The causes of the severity of this condition are not yet clear, although both metabolic and viral factors supposedly are involved. In this study our aim was to examine the possible influence that leptin levels, hepatitis C virus (HCV) RNA levels, and hepatitis G virus (HGV) infection have on the severity of steatosis and on the presence and degree of fibrosis in patients with CHC.

METHODS

One hundred eighty-two CHC patients with histological findings of steatosis were chosen from among a cohort of patients referred to our center for staging of liver disease. Among them 48 CHC patients were accurately selected so as to rule out possible confounding factors for the presence of steatosis (diabetes mellitus, hyperlipemia, obesity, alcohol). Leptin levels, HCV RNA levels, and HCV genotype, and the presence of HGV RNA were assessed in these patients and related to histological findings.

RESULTS

We found that leptin levels in CHC patients were similar to those in healthy subjects. No relationship was found between leptin levels and severity of steatosis. HCV RNA levels, HCV genotype, and the presence of HGV infection were no different among CHC patients with various degrees of steatosis. Leptin was not related to different degrees of fibrosis, whereas higher viral load was the only parameter associated to higher fibrosis scores.

CONCLUSIONS

These findings suggest that the degree of steatosis in patients with CHC does not seem to depend on serum leptin levels or on viral factors, at least as far as HCV viremia and genotype and HGV infection are concerned. The severity of fibrosis does not seem to be influenced by leptin levels, whereas HCV viral load does seem to play some role.

Efficacy of HCV core antigen detection during the preseroconversion period

BACKGROUND

The purpose of this study was to compare the performances of HCV core antigen (HCV Ag) testing with HCV RNA detection during the preseroconversion period.

STUDY DESIGN AND METHODS

Six HCV antibody (HCV Ab)-negative and HCV RNA-positive blood samples from 6 donors and 135 serial samples from 28 patients who had undergone hemodialysis, collected a mean of 90 days before the detection of HCV Ab, were tested by ELISA for the detection of HCV Ag and by PCR to quantify HCV RNA.

RESULTS

Five of the six donors were positive for HCV Ag. The donor with a negative HCV Ag test had the lowest viral load. In the hemodialysis patients, the 43 first specimens of the series were HCV RNA negative. Of the 92 specimens that were HCV RNA positive, 81 (88%) were positive for HCV Ag. Among the 74 samples with more than 10(5) RNA copies, 71 (96%) were HCV Ag positive. Average time from first viremic bleed to first HCV Ag-positive bleed was estimated at 2.0 days and that to first HCV Ab-positive bleed at 50.8 days.

CONCLUSION

HCV Ag testing permits the detection of an HCV infection about 1.5 months earlier than the HCV Ab screening tests and an average of only 2 days later than quantitative HCV RNA detection in individual specimens.

Hepatitis C virus core mutations reduce the sensitivity of a fluorescence enzyme immunoassay

Four of 107 samples obtained from hepatitis C virus (HCV) carriers showed lower HCV core antigen levels in a fluorescence enzyme immunoassay (FEIA) than expected from corresponding HCV RNA levels. Nucleotide sequencing revealed a mutation in the HCV core region (Thr49Pro) that appears to have reduced the FEIA sensitivity.

Detection of hepatitis C core antigen in the antibody negative 'window' phase of hepatitis C infection

BACKGROUND AND OBJECTIVES

Despite improvements in assays for anti-HCV, there remains a significant delay before the appearance of antibodies following infection, during which, circulating viral RNA is present. We have evaluated a prototype assay for the serological detection of hepatitis C virus (HCV) core antigen with specimens derived from the early phase of HCV infection.

MATERIALS AND METHODS

Serial specimens from 24 individuals undergoing HCV seroconversion were tested for the presence of anti-HCV, HCV RNA and HCV core antigen.

RESULTS

HCV antigen was detected at the same time as HCV RNA in 83% (20/24) cases. The mean time to the first detection of HCV antigen was approximately 1 day later than HCV RNA. Overall, 87% of HCV-RNA-positive specimens contained detectable HCV core antigen.

CONCLUSION

These results indicate that HCV core antigen can be identified by routine serological ELISA in specimens from the early antibody-negative phase of HCV infection. A test for HCV core antigen may be a useful test for identifying window phase blood donations from antibody negative donors infected with HCV.

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

BACKGROUND

Hepatitis C virus (HCV) viraemia is one of the factors for histological prognosis of chronic hepatitis C.

METHODS

One hundred and thirty-five patients who received hepatic biopsies twice at intervals of 5 years or longer were followed up for a mean of 9.7 +/- 4.0 years were studied retrospectively. The amount of HCV viraemia present was measured as the concentration of HCV core protein by using the fluorescence enzyme immunoassay method.

RESULTS

Multiple-regression analysis, using deterioration of the histological stage as a dependent variable, showed that greater age (P = 0.041), higher stage of hepatic histology at the start of follow up (P = 0.029), and higher serum concentration of core protein (P < 0.001) were independent factors affecting the deterioration of the liver's histological stage. At follow up, no significant difference in histological stage was seen between patients with serum HCV core protein > or = 100 pg/mL (n = 60) and those with serum core protein < 100 pg/mL (n = 75). The histological grade in patients with high serum core-protein levels tended to be significantly worse and the deterioration rate of the histological stage was significantly higher than in those with low HCV core protein levels (68 vs 35%, P < 0.001). The mutation rate of the HCV envelope-2/non-structural 1 (E2/NS1) nucleotide region was compared in two patients who had high serum concentrations of HCV core protein and whose histological stage had deteriorated with two patients who had low serum concentrations of the core protein and whose histological stages remained unchanged. No significant difference in E2/NS1 mutation was found.

CONCLUSIONS

The amount of HCV viraemia was suggested to be a significant factor for determining histological outcome in patients with chronic hepatitis C. The mutation rate in the E2/NS1 region did not seem to be associated with the prognosis of chronic hepatitis C.

Diagnostic tests for hepatitis C

Two categories of virological assays are in practice used for the diagnosis and management of hepatitis C virus (HCV) infection, including serological and molecular biology-based assays. Serological assays include: screening tests based on enzyme immunoassays (EIAs); supplemental "analytical" assays based on immunoblot testing; and serological assays detecting genotype-specific antibodies for the serological determination of HCV genotype, so-called "serotyping" assays. Molecular assays include: qualitative assays, detecting HCV RNA in body fluids; quantitative assays measuring HCV viral load, a parameter that estimates the level of HCV replication in the liver; and tests analyzing the sequence of HCV genomes (genotyping assays).

Development of a TT virus DNA quantification system using real-time detection PCR

Although TT virus (TTV) was isolated from a cryptogenic posttransfusion hepatitis patient, its pathogenic role remains unclear. It has been reported that the majority of the healthy population is infected with TTV. To elucidate the differences between TTV infection in patients with liver diseases and TTV infection in the healthy population, a quantification system was developed. TTV DNA was quantified by a real-time detection PCR (RTD-PCR) assay on an ABI Prism 7700 sequence detector. With this system, TTV DNA was quantified in 78 hepatitis C virus (HCV)-infected patients (63 with elevated serum alanine aminotransferase [ALT] levels and 15 with normal ALT levels) and in 70 voluntary blood donors (BDs). The quantification range was 2.08 to 7.35 log copies/ml. The intra-assay and interassay coefficients of variation were 0.37 to 6.33% and 0.60 to 7.07%, respectively. The mean serum TTV DNA levels in the HCV-infected patients with both elevated and normal ALT levels and BDs were 3.69 +/- 0.89, 3.45 +/- 0.76, and 3.45 +/- 0.67 log copies/ml, respectively. Comparison of the serum TTV DNA levels among the HCV-infected patients revealed that they were not related to the serum ALT and HCV core protein levels or to the histopathological score on liver biopsy. This study showed that (i) the RTD-PCR assay for the detection of TTV was accurate and had a high degree of sensitivity, (ii) the mean serum TTV DNA level was similar among HCV-infected patients, irrespective of their ALT level, and also among BDs, and (iii) a high serum TTV DNA level does not affect the serum ALT and HCV levels or liver damage in HCV-infected patients.

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.

HCV core immunodominant region analysis using mouse monoclonal antibodies and human sera: characterization of major epitopes useful for antigen detection

Monoclonal antibodies (MAbs) were generated by immunizing mice with a truncated recombinant protein corresponding to the immunodominant region (residues 1-120) of hepatitis C virus (HCV) nucleocapsid protein. The specific recognition by either human sera or mouse monoclonal antibodies of overlapping peptides spanning the core region 1-120 as well as the comparison with epitopes described earlier allowed the fine mapping of HCV core. Within the region 1-120, the major antigenic domain could be restricted to the first 45 amino acids. Indeed, the peptide S42G (residues 2-45) allowed the detection of an anti-HCV core response by all anticore-positive human sera examined. According to their epitope localization, three groups of mouse MABs could be evidenced that were directed against different regions of core. Group II MAbs recognized a strictly linear epitope (QDVKF, residues 20-24), whereas group I MABs were directed against a conformational epitope mainly located at the amino acid residues (QIVGG, 29-33). The epitope of group III MABs was also conformational (PRGRRQPI, residues 58-65). These three epitopes appeared close but different from the three major human epitopes RKTKRNTN, VYLLPR, and GRTWAQPGYPWPLY (residues 7-17, 34-39, and 73-86, respectively). Group II MAB 7G12A8 and group I MAB 19D9D6 were used in a sandwich ELISA for the capture and the detection, respectively, of viral core antigen in sera of patients with chronic HCV infection. After treatment of sera with triton x 100 in acidic conditions, amounts of viral antigen as low as 20 pg/ml of sera could be detected.

Interferon-alpha therapy in patients dually infected with hepatitis C virus and GB virus C/hepatitis G virus--virological response of HGV and pretreatment HGV viremia level

BACKGROUND/AIMS

The response to interferon-alpha (IFN) therapy of recently isolated GB virus C and hepatitis G virus (HGV) is still unclear. To investigate the biochemical and virological response to IFN therapy in patients with chronic hepatitis C virus (HCV) infection concomitantly infected with HGV, 196 patients with HCV who had received IFN therapy were retrospectively studied.

METHODS

HGV and HCV RNA were detected by reverse transcription nested polymerase chain reaction (RT-PCR). Serum HGV RNA levels were quantified by competitive RT-PCR. The HGV genotype was detected by restriction fragment length polymorphism analysis using the PCR products.

RESULTS

Of 196 patients, 16 (8.2%) were positive for both HCV and HGV RNA before IFN therapy. There were no significant clinical and virological differences between the patients with dual infection and those with only HCV infection. During the therapy, a decrease or loss of serum HGV RNA level was observed in these patients. Six months after cessation of the therapy, five of 16 patients became negative for HGV RNA by RT-PCR. The pretreatment HGV RNA level of the patients who lost HGV RNA after cessation of IFN was low (median=10(3) copies/ml), compared to the level (median=10(7) copies/ml, p<0.01) in the patients with positive HGV RNA after the therapy. The HGV genotype of these 16 patients was the same type.

CONCLUSIONS

These data suggest that: 1) there is no significant difference in response to IFN therapy between patients with dual and single infection; 2) HGV shows sensitivity to IFN therapy; and 3) in the patients who show a low pretreatment HGV RNA level, serum HGV RNA becomes undetectable by RT-PCR after cessation of IFN therapy.