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 EID. 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.