Development of an indirect competitive ELISA based on σC protein for detection of antibodies against avian reovirus

Avian reovirus (ARV) causes viral arthritis in poultry, and emerging variants in China demand improved serosurveillance. We developed an indirect competitive ELISA (ic-ELISA) using a monoclonal antibody against recombinant σC protein. After optimization (coating antigen 6.0 μg/mL, mAb 1:4000, blocking 90 min, serum 60 min, mAb 90 min), the cut-off percent inhibition was set at 44.5% based on 40 negative sera. The assay showed no cross-reactivity with six common avian pathogens, a detection limit of 1:400 serum dilution, and excellent reproducibility (intra-CV ≤0.70%, inter-CV ≤7.70%). Testing 87 field sera from various regions of China gave an overall seropositivity of 59.8% (regional range 50.0-75.0%). Compared with a commercial IDEXX kit, our ic-ELISA detected 52 positives vs. 48 (χ²=4.32, P = 0.038), demonstrating superior sensitivity. This reliable, sensitive, and specific serological tool is suitable for large-scale ARV surveillance and vaccine monitoring.