Rapid Visual Detection of Senecavirus A Based on RPA-CRISPR/Cas12a System with Canonical or Suboptimal PAM.

Senecavirus A (SVA) is an emerging pathogen responsible for vesicular lesions and neonatal mortality in swine. In the absence of effective vaccines or therapeutics, early and accurate diagnosis is essential for controlling SVA outbreaks. Although nucleic acid-based detection methods are commonly employed, there remains a pressing need for rapid, convenient, highly sensitive, and specific diagnostic tools. Here, we developed a two-pot assay combining recombinase polymerase amplification (RPA) with CRISPR/Cas12a containing crRNA targeting canonical protospacer adjacent motifs (PAMs) for simple, rapid, and visual identification of SVA in clinical samples. Subsequently, we successfully streamlined this system into a one-pot assay by selecting a specially designed crRNA targeting suboptimal PAM and integrating RPA amplification reagents and CRISPR/Cas12a detection components into a single reaction system in one tube. The developed methods exhibited diagnostic specificity, showing no cross-reactivity with four major swine viruses, while showing remarkable sensitivity with a lower detection limit of just two copies. Clinical validation in field samples using these two methods revealed perfect agreement (100% concordance) with conventional quantitative PCR (qPCR) results (sample size, n = 28), with both assays completing detection within 30 min. These results demonstrate that both the one-pot and two-pot RPA-CRISPR/Cas12a assays offer a reliable and efficient method for detecting SVA in this pilot study. Despite the limited sample size, the assays combine rapid reaction time with high sensitivity and specificity, showing great potential for future diagnostic applications.