Novel Evolved Immunoglobulin (Ig)-Binding Molecules Enhance the Detection of IgM against Hepatitis C Virus

Jie Cao,Chao Liu,Qiuli Chen,Xufang Yang,Niansong Wang,Baohua Qian,Jinhong Wang,Huaqun Zhang,Peipei Qi,Shuhan Sun,Hua Yang,Wei Pan,Shaohua Jiang,John E Tavis

doi:10.1371/journal.pone.0018477

Abstract

Detection of specific antibodies against hepatitis C virus (HCV) is the most widely available test for viral diagnosis and monitoring of HCV infections. However, narrowing the serologic window of anti-HCV detection by enhancing anti-HCV IgM detection has remained to be a problem. Herein, we used LD5, a novel evolved immunoglobulin-binding molecule (NEIBM) with a high affinity for IgM, to develop a new anti-HCV enzyme-linked immunosorbent assay (ELISA) using horseradish peroxidase-labeled LD5 (HRP-LD5) as the conjugated enzyme complex. The HRP-LD5 assay showed detection efficacy that is comparable with two kinds of domestic diagnostic kits and the Abbott 3.0 kit when tested against the national reference panel. Moreover, the HRP-LD5 assay showed a higher detection rate (55.9%, 95% confidence intervals (95% CI) 0.489, 0.629) than that of a domestic diagnostic ELISA kit (Chang Zheng) (53.3%, 95% CI 0.463, 0.603) in 195 hemodialysis patient serum samples. Five serum samples that were positive using the HRP-LD5 assay and negative with the conventional anti-HCV diagnostic ELISA kits were all positive for HCV RNA, and 4 of them had detectable antibodies when tested with the established anti-HCV IgM assay. An IgM confirmation study revealed the IgM reaction nature of these five serum samples. These results demonstrate that HRP-LD5 improved anti-HCV detection by enhancing the detection of anti-HCV IgM, which may have potential value for the early diagnosis and screening of hepatitis C and other infectious diseases.

Highlights

Serologic determination of specific antibodies against hepatitis C virus (HCV) and detection of viral RNA are the most widely available tests for viral diagnosis and monitoring of HCV infection
The affinity of LD5 binding to human IgM (hIgM), with a KD of 0.31 nM, was higher than that binding to Human IgG (hIgG) and reached the level of the binding of staphylococcal protein A (SpA) with the hIgG
enzyme-linked immunosorbent assay (ELISA) results showed that HRPLD5 had a much stronger binding reaction with hIgM and human IgA (hIgA) than did horseradish peroxidase (HRP)-goat anti-human PcAb, and had similar binding to hIgG compared with HRP-goat anti-human PcAb (Fig. 1)

Summary

Introduction

Serologic determination of specific antibodies against hepatitis C virus (HCV) and detection of viral RNA are the most widely available tests for viral diagnosis and monitoring of HCV infection. The sensitivity of the third-generation EIA was greater than 98%, a significant improvement over the approximately 80% sensitivity of the first-generation EIA, and the average seroconversion period of 10 to 16 weeks using first-generation EIA was shortened to approximately 8 weeks [3,4,5,6,7] This improvement was mostly attributed to the addition of HCV coating antigens, core proteins (c22–3), NS3 (c33c) and NS5 to the NS4 protein (c100–3) used in the first-generation EIA. This 8 weeks serologic window of anti-HCV detection remains to be a problem for early viral diagnosis and efficient screening of blood donors. It should be possible to narrow the serologic window of anti-HCV detection by enhancing the anti-HCV IgM detection

Methods

Results

Conclusion