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.

Vibration Controlled Transient Elastography in Screening for Silent Liver Diseases.

OBJECTIVES: The objective of this study was to screen for significant hepatic fibrosis or steatosis in asymptomatic, apparently healthy subjects by using Vibration-controlled transient elastography and controlled attenuation parameter (CAP). METHODS: Prospectively, 433 asymptomatic apparently healthy adults were included. Fibroscan/CAP examination was performed for all of them. Subjects with liver stiffness measurement > 6 kPa or CAP >248 dB/m were further evaluated to assess underlying chronic liver disease. RESULTS: According to fibroscan/CAP examination, subjects were classified into four subgroups: normal (119) with CAP score of 215.85 ± 24.81 dB/m and fibrosis score of 4.47 ± 0.81 kPa, subjects with steatosis only 133 with CAP score of 309.41 ± 42.6 dB/m and fibrosis score of 4.74 ± 0.82 kPa, subjects with both steatosis and fibrosis 95 with CAP score of 318.20 ± 39.89 dB/m and fibrosis score of 7.92 ± 2.58 kPaand subjects with fibrosis only 86 with CAP score of 213.48 ± 22.62 dB/m and fibrosis score of 6.96 ± 1.11 kPa. S0 was present in 205 (47.3%), S1 in 48 (10.2%), S2 in 16 (3.7%) and S3 in 168 (38.8%) of studied subjects, whereas F0-1 was present in 371 (85.7%), F2 in 44 (10.16%), F3 in 16 (3.7%) subjects and F4 in only one (0.23%) subject. Subjects with both steatosis and fibrosis showed significantly higher transaminases, triglycerides and total cholesterol levels than other subgroups. CONCLUSIONS: Most asymptomatic, apparently healthy subjects (72%) have significant steatosis and fibrosis. Liver stiffness measurement and CAP might represent promising first-line noninvasive procedures to screen for silent liver diseases in the general population.