A rapid, visual, ultrasensitive and highly specific method for detecting adeno-associated virus 2020 based on the LAMP-CRISPR/Cas12a system.

Avian parvovirus infection would lead to growth retardation, weight loss, physical deformities and increased mortality in poultry, causing substantial economic losses to the poultry industry. Therefore, the development of a rapid, visual, ultrasensitive and highly specific method is essential for timely diagnosis and effective control of the avian parvovirus infection. In this study, we developed a detection platform based on loop-mediated isothermal amplification (LAMP) combined with the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 12a (Cas12a) system. Firstly, we have identified a novel avian parvovirus strain from diseased Muscovy ducks. Through genome sequencing, sequence assembly and phylogenetic tree analysis, we have identified this novel avian parvovirus as an adeno-associated virus (AAA) belonging to the family Parvoviridae, subfamily Parvovirinae and genus Dependoparvovirus. So, the novel virus strain was named AAV-2020. Next, specific sgRNAs and LAMP primers targeting the 3 capsid proteins (Cap) genes of AAV-2020 were designed and optimized. Moreover, the CRISPR/Cas12a-based system demonstrated a limit of detection as low as 2 copies/μL for AAV-2020. Importantly, the system could effectively distinguish AAV-2020 from 3 closely related AAV strains with high sequence similarity, indicating excellent specificity. In summary, we developed a novel, rapid, visual, ultrasensitive and highly specific detection system for AAV-2020, offering a reliable tool for early diagnosis and on-site detection of avian parvovirus infections, which would aid in the prevention and control of avian parvovirus infection in poultry industry.