Development and Application of a High Sensitivity Immunochromatographic Test Strip for Detecting Classical Swine Fever Virus Antibody

Abstract

Background: Classical swine fever (CSF) is caused by classical swine fever virus (CSFV) and has lead huge losses to the pig industry worldwide. Although vaccination and other control measures have been carried out, it is essential to establish a rapid valid method for CSF vaccination monitoring and clinical diagnosis. CSFV E2 protein has been well known as a major antigen for antibody detection. It is significant to improve affinity between E2 protein and CSFV antibody to result in a better performance of detection method. Results: In this study, a recombinant E2 extracellular protein (aa 1-331), which was with the native homodimer conformation and had a high affinity with anti-CSFV-E2 monoclonal antibody WH303, was expressed using Bac-to-Bac baculovirus expression system. A novel immunochromatographic test strip based on the recombinant CSFV E2 protein was developed for CSFV antibody detection. The sensitivity of this strip for detecting CSFV standard positive serum was 1:102400, 4 times higher than that of the former developed CnC2 test strip. No cross reaction with other swine virus antibodies was observed. The detection of clinical swine serum samples (n=138) demonstrated that the agreement of the new E2 test strip with three commercial ELISA kits was 88.40% (122/138), 86.23% (119/138), and 96.38% (133/138), respectively. Conclusion: Our data indicate that a novel E2 test strip with higher sensitivity has been developed and can be applied for clinical sample detections, providing a new powerful and simple approach for future monitoring CSFV antibodies.