Multicenter performance evaluation of the Elecsys HCV Duo immunoassay

Review of the U.S. Air Force Academy Hepatitis C Virus Screening Program to Ensure High-Value Care

INTRODUCTION

Hepatitis C virus (HCV) is primarily transmitted through blood-to-blood contact. Leading health agencies have called for the elimination of HCV as a public health threat, with universal screening considered a part of the strategy. Hepatitis C virus screening among incoming cadets and cadet candidates at the United States Air Force Academy (USAFA) was implemented in 2023. The purpose of this quality improvement project was to determine the results of this screening and the associated fiscal costs, benefits, and harms to make a recommendation for future incoming classes.

MATERIALS AND METHODS

The prevalence of HCV antibody positivity and confirmed HCV infections were calculated among the incoming cadets and cadet candidates at USAFA in summer 2023. Screening was conducted with a highly sensitive HCV total antibody test, and those who screened positive were further tested with a quantitative HCV polymerase chain reaction. The screening and follow-up care costs were calculated, and the potential harm of receiving a false positive notification was considered.

RESULTS

Of the 1,360 persons screened at USAFA in 2023, no confirmed HCV infections were identified. There was one false positive on screening in the cadet population (n = 1,131) and one false positive in the cadet candidate population (n = 229). The fiscal cost of universal HCV screening upon accession of cadets and cadet candidates, including medical follow-up, was at least $5,279. The opportunity cost was minimal because blood was drawn for other mandatory programs, although screening may have caused social and psychological harm to those receiving a false positive notification.

CONCLUSIONS

The prevalence of chronic HCV infection among incoming USAFA cadets and cadet candidates was 0%, below the population screening threshold that warrants screening, according to the Centers for Disease Control and Prevention. The harms of screening, including fiscal costs and potential psychological harm to individuals with a false positive screen, likely outweigh the benefits. We recommend against universal HCV screening in 2024 upon accession of USAFA cadets and cadet candidates.

Glycylglycine promotes the solubility and antigenic utility of recombinant HCV structural proteins in a point-of-care immunoassay for detection of active viremia

BACKGROUND

Although E. coli is generally a well-opted platform for the overproduction of recombinant antigens as heterologous proteins, the optimization of expression conditions to maximize the yield of functional proteins remains empirical. Herein, we developed an optimized E. coli (BL21)-based system for the overproduction of soluble immunoreactive HCV core/envelope proteins that were utilized to establish a novel immunoassay for discrimination of active HCV infection.

METHODS

The core/E1-E2 genes were amplified and expressed in E. coli BL21 (DE3) in the absence/presence of glycylglycine. The antigenic performance of soluble proteins was assessed against 63 HCV-seronegative (Ab-) sera that included normal and interferent sera (HBV and/or chronic renal failure), and 383 HCV-seropositive (Ab+) samples that included viremic (chronic/relapsers) and recovered patients' sera. The color intensity (OD450) and S/Co values were estimated.

RESULTS

The integration of 0.1-0.4M glycylglycine in the growth media significantly enhanced the solubility/yield of recombinant core and envelope proteins by ~ 225 and 242 fold, respectively. This was reflected in their immunoreactivity and antigenic performance in the developed immunoassay, where the soluble core/E1/E2 antigen mixture showed 100% accuracy in identifying HCV viremic sera with a viral RNA load as low as 3800 IU/mL, without cross-reactivity against normal/interferent HCV-Ab-sera. The ideal S/Co threshold predicting active viremia (> 2.75) showed an AUC value of 0.9362 (95% CI: 0.9132 to 0.9593), with 87.64, 91.23% sensitivity and specificity, and 94.14, 82.11% positive and negative predictive values, respectively. The different panels of samples assayed with our EIA showed a good concordance with the viral loads and also significant correlations with the golden standards of HCV diagnosis in viremic patients. The performance of the EIA was not affected by the immunocompromised conditions or HBV co-infection.

CONCLUSION

The applicability of the proposed platform would extend beyond the reported approach, where glycylglycine, low inducer concentration and post-induction temperature, combined with the moderately-strong constitutive promoter enables the stable production of soluble/active proteins, even those with reported toxicity. Also, the newly developed immunoassay provides a cost-effective point-of-care diagnostic tool for active HCV viremia that could be useful in resource-limited settings.