Development of an RT-RAA-CRISPR-Cas12a assay for rapid, sensitive and visual detection of Tilapia Lake Virus (TiLV).

In this study，we developed a new, highly efficient, and sequence-specific method for detecting Tilapia Lake Virus (TiLV) based on the clustered regularly interspaced short palindromic repeats (CRISPR) - CRISPR-associated protein 12a (Cas12a) system. TiLV is a highly contagious virus that has caused significant damage to the global aquaculture industry. Specific primers, CRISPR RNA (crRNA), and single-stranded DNA (ssDNA) reporters were designed to detect TiLV genome segment 3, with the ssDNA reporters modified at the 5' and 3' ends with fluorophore and quencher groups, respectively. The assay showed no cross-reactivity with other bacterial and viral pathogens in fish. The detection limit was 9.10 copies per reaction for recombinant plasmid standards and 91.82 fg/μL for TiLV RNA, demonstrating high sensitivity. The reverse transcription recombinase aided amplification (RT-RAA) coupled CRISPR/Cas12a method showed 100 % concordance with the standard fluorescence method, indicating its accuracy and suitability for clinical testing. This study innovatively combined the RT-RAA technique with the CRISPR/Cas12a reaction system, offering a new diagnostic method for TiLV that is fast, portable, highly specific, and sensitive. This enables on-site rapid screening for TiLV, ensuring aquaculture safety and the secure circulation of aquatic animal products.