A DNA-launched reverse genetics system of feline calicivirus identified 3′ UTR as an essential element for its replication

Abstract Virulent systemic feline calicivirus (VS-FCV) is a newly emerging pathogen associated with severe and acute virulent systemic disease, characterized with jaundice, oedema and high mortality (approximately 70%) in cat population. Currently, VS-FCV has a worldwide spread, but deficient in effective vaccines or therapeutic options to combat infection. As a result, VS-FCV is posing a serious threat to the health of felines. So far, the genomic characteristics and function of VS-FCV are poorly understood, and the underlying mechanism for its increased pathogenicity is also enigmatic. Reverse genetic system is proven to be a powerful tool to study the molecular biology of RNA viruses, but the reverse genetic system of VS-FCV has not been reported. In this study, we pioneered simple and fast construction of a plasmid-based VS-FCV reverse genetics system that efficiently produced infectious progeny virus in CRFK cells. Using this system, we next investigated the role of 3' untranslated region (UTR) and poly (A) tail on determining infectivity and replication of VS-FCV. The results showed that 3' UTR was a key element for maintaining the infection and replication capacity of VS-FCV. In addition, we found that the poly (A) tail was important for maintaining the infectivity of VS-FCV. In detail, if the infectious clone of VS-FCV lacks the poly (A) tail, or its poly (A) tail length is less than 28 bases, it failed to rescue any infectious progeny virus. In conclusion, we successfully established a rapid and efficient VS-FCV reverse genetic system, which provides a good platform for future research on the gene function and pathogenesis of VS-FCV. The effects of 3' UTR and poly (A) tail on VS-FCV infectivity and replication also provided new clues to the pathogenesis of VS-FCV.