Simplified Reverse Genetics Method to Recover Recombinant Rotaviruses Expressing Reporter Proteins.

Rotaviruses are a large and evolving population of segmented double-stranded RNA viruses that cause severe gastroenteritis in the young of many mammalian and avian host species, including humans. With the recent advent of rotavirus reverse genetics systems, it has become possible to use directed mutagenesis to explore rotavirus biology, modify and optimize existing rotavirus vaccines, and develop rotavirus multitarget vaccine vectors. In this report, we describe a simplified reverse genetics system that allows the efficient and reliable recovery of recombinant rotaviruses. The system is based on co-transfection of T7 transcription vectors expressing full-length rotavirus (+)RNAs and a CMV vector encoding an RNA capping enzyme into BHK cells constitutively producing T7 RNA polymerase (BHK-T7). Recombinant rotaviruses are amplified by overseeding the transfected BHK-T7 cells with MA104 cells, a monkey kidney cell line that is highly permissive for virus growth. In this report, we also describe an approach for generating recombinant rotaviruses that express a separate fluorescent reporter protein through the introduction of a 2A translational stop-restart element into genome segment 7 (NSP3). This approach avoids deleting or modifying any of the viral open reading frames, thus allowing the production of recombinant rotaviruses that retain fully functional viral proteins while expressing a fluorescent protein.