A rapid and sensitive lanthanide-based fluorescent microsphere immunochromatographic test for semi-quantitative detection of infectious bursal disease virus in poultry

Infectious bursal disease virus (IBDV) is a major immunosuppressive pathogen threatening global poultry production. The emergence of very virulent (vvIBDV) and novel variant strains (nVarIBDV) has increased immune escape and reduced vaccine effectiveness, underscoring the need for rapid and reliable diagnostic tools. To promote antigen detection technologies which usually time-consuming and require specialized laboratory facilities, this study developed a simple, rapid, and sensitive fluorescent microsphere immunochromatographic test strip (FM-ICTS) for semi-quantitative detection of IBDV antigen. The FM-ICTS was constructed using lanthanide fluorescent microspheres conjugated to an anti-VP2 monoclonal antibody within a double-antibody sandwich lateral flow format. Reaction conditions were optimized, and a quantitative standard curve was established using serial dilutions of inactivated IBDV (B87 strain). The assay generated stable fluorescence signals within 15 min and showed high analytical sensitivity, detecting IBDV antigen at dilutions up to 1:5120. No cross-reactivity with Chicken Anemia Virus (CAV), Avian Leukosis Virus(ALV), Avian Influenza Virus(AIV), or Marek’s Disease Virus(MDV) was observed, confirming excellent specificity. Repeatability tests demonstrated low coefficients of variation (< 10%). When evaluated using 50 clinical samples, FM-ICTS exhibited 95% concordance with the national standard RT-PCR method and accurately identified vvIBDV, classical infectious bursal disease virus (clIBDV), and nVarIBDV strains. With significant cost advantage and capability of relative quantification, the developed FM-ICTS provides a candidate method suitable for field diagnostics and vaccine quality monitoring.