Development of a time-resolved fluoroimmunoassay for Epstein-Barr virus viral capsid antigen IgA antibody in human serum

Viral capsid antigen (VCA) IgA is one of the most commonly tested antibodies for Epstein-Barr virus (EBV) in the clinic and is a proven biomarker to predict the risk of nasopharyngeal carcinoma (NPC) and other diseases. At present, a VCA-IgA antibody is used for clinical diagnosis by enzyme-linked immunosorbent assay (ELISA), which can detect samples only qualitatively or semi-quantitatively, with unsatisfactory sensitivity and specificity. In this study, an indirect time-resolved fluoroimmunoassay (TRFIA) using Eu(3+) labeled mouse anti-human IgA monoclonal antibodies as a tracer was developed. This method produced a linear range of 0-30 AU/mL, with a limit of detection of 0.018 AU/mL. The intra- and inter-assay precisions were 1.62-4.30% and 3.56-7.57%, respectively. TRFIA showed no cross-reactivity against potentially interfering substances and a better sensitivity and specificity compared with commercial ELISA. This study confirmed that an indirect TRFIA meets the requirement for clinical testing and could be an alternative to detect VCA-IgA levels in human serum in the clinic.