CRISPR/Cas12a-assisted visual and on-site detection of porcine circovirus type 2.

BACKGROUND: Porcine circovirus type 2 (PCV2) is a globally prevalent viral pathogen that causes substantial economic losses in the swine industry. Rapid and accurate on-site diagnosis is critical for controlling the spread of PCV2. In recent years, RNA-guided CRISPR/Cas12a nucleases combined with recombinase polymerase amplification (RPA) have emerged as a promising approach for nucleic acid detection. This study aimed to develop a novel RPA-CRISPR-based method for the rapid and sensitive detection of PCV2 in field settings. RESULTS: We designed and optimized CRISPR RNAs (crRNAs) targeting conserved regions of the PCV2 Cap and Rep genes. Upon recognition of the target sequence, the Cas12a nuclease was activated to cleave a single-stranded DNA-fluorophore quencher (ssDNA-FQ) reporter, generating a fluorescent signal detectable either by a fluorescence detector or via visual readout. The entire procedure was performed at 37 °C and completed within one hour. The assay achieved a detection limit as low as 10 copies/µL and showed no cross-reactivity with other major porcine viruses. Furthermore, a rapid-release reagent was used to replace conventional DNA extraction from serum samples, facilitating efficient on-site detection. The assay was validated using clinical samples, and the results showed strong concordance with those obtained by PCR. CONCLUSIONS: The RPA-CRISPR-based assay developed in this study is highly sensitive and specific, enabling detection of PCV2 within one hour. Its simplicity, rapidity, and ease of use in the field offer significant practical advantages, making it a valuable tool for the on-site diagnosis of PCV2. This method represents a promising alternative for the early and rapid detection of PCV2 infections and holds potential for contributing to the prevention and control of the disease in the swine industry.