Development of quantum dots-based immunochromatographic assay for the detection of infectious bronchitis virus

Infectious bronchitis virus (IBV) is a significant pathogen threatening global poultry production, known for its rapid transmission and the continuous emergence of new variants. Here, a monoclonal antibody (mAb) which specifically recognizes IBV SABD domain of S1 protein, designated 5G4, was prepared. This mAb, along with a previously developed mouse mAb (N1) targeting the IBV N protein, was utilized as the conjugate and capture antibodies, respectively, to develop a quantum dot-based lateral flow assay for the rapid detection of IBV infections. The optimal mass ratio of quantum dots to antibodies was determined to be 1.25:1, with an optimal incubation time of 1 h. The best line quality on the nitrocellulose membrane was observed when the concentrations of goat anti-mouse IgG and N1 were 0.8 mg/mL and 2 mg/mL, respectively. The developed assay was demonstrated rapid diagnostic capabilities, specifically detecting various IBV subtypes without cross-reactivity to other common avian pathogens. Sensitivity tests revealed that the assay could detect a minimum virus load of approximately 10^3.49 EID₅₀. The stability of the test strips was confirmed, as they maintained their functionality without significant changes after storage at room temperature for 1, 3, and 6 months. Finally, the assay was compared with a laboratory-developed qPCR method, which yielded a Kappa coefficient of 0.799 (p < 0.001), indicating a good consistency between the two methods. This study presents a quantum dot-based immunochromatographic assay for the rapid diagnosis of IBV, which offers a valuable tool for on-site detection of IBV infections and rapid disease diagnosis on poultry farms.