One copy in one-pot for rapid and accurate SFTSV testing by LAC12b-2M

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne pathogen that can cause a fatality rate as high as 12-50 %, posing a significant threat to public health. SFTSV is prevalent in mountainous and hilly regions with relatively poor medical conditions. Therefore, there is an urgent need to develop a new convenient, rapid and sensitive method for SFTSV detection in low-resource environments.

We developed a one-pot and visualized method for SFTSV detection using loop-mediated isothermal amplification assisted by CRISPR/Cas12b with G478A/K396A double mutations (LAC12b-2M). The specificity, sensitivity, accuracy and limit of detection (LOD) of LAC12b-2M were evaluated using clinical reverse transcription-quantitative PCR (RT-qPCR) as the reference method, with gradient dilutions of strong positive SFTSV RNA samples and 215 clinical serum samples from two cohorts.

LAC12b-2M is sensitive to detect SFTSV with a LOD of 1 copy/μL at 61 °C within 30 min. Compared to clinical RT-qPCR, LAC12b-2M demonstrated a sensitivity of 98.8 % (82/83), a specificity of 100.0 % (96/96), and an accuracy of 99.4 % (178/179) in cohort 1 (n=179), and an accuracy of 100.0 % in cohort 2 (n=36).

Our LAC12b-2M method holds promise for point-of-care SFTSV testing in different healthcare settings, particularly in low-resource region where SFTSV is prevalent.