The correlation of HCV RNA and HCV core antigen in different genotypes of HCV

Hepatitis C Virus-Core Antigen: Implications in Diagnostic, Treatment Monitoring and Clinical Outcomes

The hepatitis C virus (HCV) infection, a global health concern, can lead to chronic liver disease. The HCV core antigen (HCVcAg), a viral protein essential for replication, offers a cost-effective alternative to HCV RNA testing, particularly in resource-limited settings. This review explores the significance of HCVcAg, a key protein in the hepatitis C virus, examining its structure, function, and role in the viral life cycle. It also evaluates its clinical use in diagnosis and treatment monitoring, comparing its performance to the standard HCV RNA assay using data from PubMed and Google Scholar. HCVcAg assays show high pooled sensitivity (93.5%) and pooled specificity (99.2%) compared to HCV RNA assays, correlating closely (r = 0.87) with HCV RNA levels. Hence, HCVcAg testing offers a cost-effective way to diagnose active HCV infections and monitor treatment, especially in resource-limited settings, but its sensitivity can vary and standardization is needed. HCVcAg also predicts liver disease progression and assesses liver damage risk, aiding patient management. It helps to identify patients at risk for fibrosis or carcinoma, making it vital in hepatitis C care. HCVcAg testing can expand access to HCV care, simplify management, and contribute to global elimination strategies, especially in low- and middle-income countries.

Comparison of anti-HCV combined with HCVcAg (Elecsys HCV Duo immunoassay) and anti-HCV rapid test followed by HCV RNA analysis using qRT-PCR to identify active infection for treatment

Hepatitis C virus (HCV) infection can cause acute and chronic hepatitis, leading to liver cirrhosis and hepatocellular carcinoma. The World Health Organization aims to eliminate viral hepatitis by 2030 through extensive screening and treatment. To achieve this goal, comprehensive and widespread screening is essential for diagnosis and treatment. This study aims to evaluate the diagnostic sensitivity and specificity of the Elecsys® HCV Duo immunoassay (Duo-assay), which simultaneously detects anti-HCV antibodies (Duo/anti-HCV) and HCV core antigen (Duo/HCVcAg) in a single sample, compared with initially antibody testing followed by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, this study aimed to evaluate a relationship between Duo/HCVcAg and qRT-PCR assay in different genotypes. A total of 769 plasma samples were tested using the Duo-assay to further evaluate the test's performance and conduct Duo/HCVcAg correlation analysis using qRT-PCR for each genotype. Among the active infection group (anti-HCV+/RNA+; n = 473), the Duo-assay showed 100% sensitivity for detecting Duo/anti-HCV and 70.6% for Duo/HCVcAg. In the resolved infection group (anti-HCV+/RNA-; n = 176), the assay showed 100% sensitivity for Duo/anti-HCV and 100% specificity for Duo/HCVcAg. In the non-infected group (anti-HCV-/RNA-; n = 120), the assay showed 100% specificity for both Duo/anti-HCV and Duo/HCVcAg. Moreover, no correlation was observed between the Duo/HCVcAg and HCV RNA tests, irrespective of genotype. These findings indicate that the Duo-assay is highly sensitive for detecting anti-HCV and specifically identifies patients with active infection. Nevertheless, cases with anti-HCV+/HCVcAg-results should undergo additional confirmation with western blot/immunoblot and qRT-PCR to ensure diagnostic accuracy, especially in Blood donation facilities.

An amino acid substitution in HCV core antigen limits its use as a reliable measure of HCV infection compared with HCV RNA

Hepatitis C virus (HCV) is a viral pathogen that causes chronic hepatitis, which can lead to cirrhosis and hepatocellular carcinoma. Detection of HCV RNA is the standard method used to diagnose the disease and monitor antiviral treatment. A quantification assay for the HCV core antigen (HCVcAg) has been proposed as a simplified alternative to the HCV RNA test for predicting active HCV infection, with the aim of achieving the global goal of eliminating hepatitis. The objective of this study was to determine the correlation between HCV RNA and HCVcAg, as well as the impact of amino acid sequence heterogeneity on HCVcAg quantification. Our findings demonstrated a strong positive correlation between HCV RNA and HCVcAg across all HCV genotypes (1a, 1b, 3a, and 6), with correlation coefficients ranging from 0.88 to 0.96 (p < 0.001). However, in some cases, samples with genotypes 3a and 6 exhibited lower HCVcAg levels than expected based on the corresponding HCV RNA values. Upon the core amino acid sequence alignment, it was observed that samples exhibiting low core antigen levels had an amino acid substitution at position 49, where threonine was replaced by either alanine or valine. Core mutation at this position may correlate with one of the epitope regions recognized by anti-HCV monoclonal antibodies. The present findings suggest that the utilization of HCVcAg as a standalone marker for HCV RNA might not provide adequate sensitivity for the detection of HCV infection, especially in cases where there are variations in the amino acid sequence of the core region and a low viral load of HCV RNA.

Performance of HCV Antigen Testing for the Diagnosis and Monitoring of Antiviral Treatment: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

Active hepatitis C virus (HCV) infection is based on the detection of HCV RNA that it is effective but presents high cost and the need to hire trained personnel. This systematic review and meta-analysis is aimed at evaluating the diagnostic accuracy of HCV Ag testing to identify HCV cases and to monitor antiviral treatment including DAA treatment.

METHODS

The studies were identified through a search in PubMed, Lilacs, and Scopus from 1990 through March 31, 2020. Cohort, cross-sectional, and randomized controlled trials were included. Two independent reviewers extracted data and assessed quality using an adapted Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Our primary outcome was to determine the accuracy of HCV Ag detection for the diagnosis, which we estimated using random-effects meta-analysis.

RESULTS

Of 3,062 articles identified, 54 met our eligibility criteria. The studies described cohorts from 20 countries, including 14,286 individuals with chronic HCV individuals. Studies for ECLIA technology demonstrated highest quality compared to studies that used ELISA. The pooled sensitivity and specificity (95% CI) for HCV Ag detection of active HCV infection were 98.82% (95%CI = 98.04%; 99.30%) and 98.95% (95%CI = 97.84%; 99.49%), respectively. High concordance was found between HCV Ag testing and HCV RNA detection 89.7% and 95% to evaluate antiviral treatment.

CONCLUSIONS

According to our findings, HCV Ag testing could be useful to identify HCV active cases in low-resource areas. For antiviral treatment, HCV Ag testing will be useful at the end of treatment.

Rapid, sensitive and cost-effective determination of immune checkpoint inhibitor activity using a magnetic bead-based binding assay

Immune checkpoint Inhibitors (ICIs) are effective immunno-therapeutic agents for cancer. Rapid and sensitive determination of the blocking activity of ICIs is important for ICIs development and immunological research. Among various immune checkpoint (IC) binding assays, cell-based binding assays are widely regarded, and the functional ELISA is a convenient alternative. However, these methodologies are limited by time-consuming preparation of cell lines stably expressing IC molecules, or long turnaround time with high cost. In this study, two magnetic bead based binding assays were developed to evaluate activity of ICIs, which was determined by a soluble ligand/bead immobilized receptor based binding assay (sL/bR binding assay) that assessed efficacy to block binding of one soluble IC ligand on its cognate receptor immobilized beads, or by a soluble receptor/bead immobilized ligand based binding assay (sR/bL binding assay) that assessed efficacy to block binding of soluble IC receptor on its cognate ligand immobilized beads. Half maximal inhibitory concentration (IC50) values of ICIs were calculated to determine ICIs activity. The sL/bR binding assay accurately determined the activity of two TIGIT blocking antibodies, since the relative blocking activity of two TIGIT antibodies determined by the sL/bR binding assay established in this study and that by the cell based binding assay were almost identical. In contrast, the sR/bL binding assay showed significantly improved sensitivity to determine activity of two PD-1 blocking antibodies than the sL/bR binding assay that was tested in this study and previous reports. Moreover, both amount of the used recombinant protein of ICI receptor/ligand and turnaround time of the two binding assays were more than 10 times less than those of the functional ELISA. These data indicate that the two magnetic bead based binding assays are sensitive, rapid and cost-effective methods to determine blocking activity of ICIs.

Improving Diagnosis of Hepatitis C Virus Infection Using Hepatitis C Core Antigen Testing in a Resource-Poor Setting

INTRODUCTION:

We compared the hepatitis C virus (HCV) core antigen test with the HCV RNA assay to confirm anti-HCV results to determine whether the HCV core antigen test could be used as an alternative confirmatory test to the HCV RNA test.

METHODS:

Sera from 156 patients were analyzed for anti-HCV and HCV core antigen using a chemiluminescent microparticle immunoassay (Architect i2000SR) and for HCV RNA using the artus HCV RG RT-PCR Kit (QIAGEN) in a Rotor-Gene Q instrument.

RESULTS:

The diagnostic sensitivity, specificity, and positive and negative predictive values of the HCV core antigen assay compared to the HCV RNA test were 77.35%, 100%, 100%, and 89.38%, respectively. HCV core antigen levels showed a good correlation with those from HCV RNA quantification (r =0.872). However, 13 samples with a viral load of less than 4000 IU/mL were negative in the HCV core antigen assay. All gray-zone reactive samples were also RNA positive and were positive on repeat testing.

CONCLUSIONS:

The Architect HCV core antigen assay is highly specific and has an excellent positive predictive value. At the present level of sensitivity (77%), the study is still relevant in a low-income setting in which most of the HCV-positive patients would go undiagnosed, since HCV RNA testing is not available and/or not affordable. HCV core antigen testing can also help determine the true burden of infection in a population, considering the fact that almost 50% of the anti-HCV positive cases are negative for HCV RNA.

Subclinical Hepatitis C Virus Infection in Patients with Chronic Obstructive Pulmonary Disease: Evidence from a Cross-Sectional Multicenter Observation Study

Background: Patients with hepatitis virus C (HCV) infection have declined levels of forced expiratory volume (FEV), which is a prognostic marker for chronic obstructive pulmonary disease (COPD). Objectives: The current study primarily aimed to investigate the incidence of subclinical HCV infection (clinical signs are absent but positive HCV RNA test performed by polymerase chain reaction) in patients with COPD of Zhejiang province, China, and its secondary aim was to investigate the clinical influence of HCV infection on COPD severity by body mass index, airflow obstruction, dyspnea, and exercise capacity (BODE) scoring index and pulmonary function tests (PFT). Methods: A total of 252 patients with COPD (confirmed by routine lab tests, BODE index, and PFT) were included in a cross-sectional multicenter study. An anti-HCV antibody test was used to diagnose HCV infection. Hepatitis virus C RNA was tested for patients with a HCV antibody-positive test. Results: Twelve patients had a positive anti-HCV antibody test. Of 12 anti-HCV antibody positive test patients, 10 were positive for the HCV RNA. The prevalence of anti-HCV antibody positivity and HCV RNA positivity was 12/ 252 and 10/ 252, respectively. The partial arterial pressure of oxygen was the same for patients with HCV RNA positive test compared to those with a negative anti-HCV antibody test (59.70 ± 5.50 mmHg vs. 63.84 ± 15.63 mmHg, P = 0.791). Patients with a positive HCV RNA test had a higher partial arterial pressure of carbon dioxide compared to those with a negative anti-HCV antibody test (43.70 ± 1.89 mmHg vs. 49.42 ± 7.33 mmHg, P = 0. 007). BODE index was higher for patients with HCV RNA positive test than those with anti-HCV antibody test negative (6 (3 - 7) vs. 4 (2 - 6), P < 0.0001). Among the variables of BODE index scoring, the values of distance walked in 6 min (P < 0.0001) and % predicted forced expiratory volume in 1 s (P < 0.0001) were fewer for patients with HCV RNA positive test than those with a negative anti-HCV antibody test. Conclusion: This study demonstrated that subclinical HCV infection may be observed in COPD patients.

The correlation of HCV RNA and HCV core antigen in different genotypes of HCV

Background

To analyze the correlation of HCV RNA and HCV core antigen (HCV cAg) in different genotypes of HCV.

Methods

One hundred and six patients who were diagnosed with HCV infection by HCV RNA test were included in the study. HCV genotypes were detected by PCR fluorescent probe. Detected HCV cAg's expression in serum quantitatively and qualitatively with chemiluminescent micro‐particle immuno assay (CMIA) and enzyme‐linked immunosorbent assay (ELISA), respectively, and compared positive rates. Analyzed the correlation of HCV RNA and HCV cAg in different genotypes.

Results

Distribution of HCV genotypes in 106 HCV infected patients were as follows: 1b genotype 46 (43.4%); 2a genotype 7 (6.6%); 3a genotype 18 (17.0%); 3b genotype 3 (2.8%); 6a genotype 9 (8.5%); 1b/3b mixed type 13 (12.3%); and unidentified type 10 (9.4%). Positive rates of HCV cAg detected by CMIA and ELISA were 100% and 56%, respectively, with statistical significance (χ² = 60.38, P = 0.000). HCV cAg in 1b genotype group was higher than that in 3b and 1b/3b genotype groups, with statistical significance (U = 3.0, P = 0.006, U = 165, P = 0.014). HCV RNA and HCV cAg in genotype 1b demonstrated a positive correlation (r = 0.894, P = 0.04).

Conclusion

Major genetic subtype of HCV genotype was 1b. Compared with ELISA, detection of HCV cAg by CMIA increased the positive rate and facilitated early diagnosis and treatment of HCV‐infected patients. With the increase in HCV RNA load and the expression of HCV cAg, HCV cAg could be an early indicator for the diagnosis of HCV infection in 1b genotype.