Generation of recombinant rotaviruses from just 11 cDNAs encoding a viral genome

Reverse genetics technology allows one to engineer replication-competent viruses from cloned cDNAs at will. Since the establishment of the initial reverse genetics system for species A rotaviruses (RVAs) requiring a helper virus in 2006, attempts have been successfully made to improve this technology. Efficient generation of replication-competent RVAs is now possible from just 11 T7-driven plasmids encoding an RVA genome when the quantity ratio of the two rescue T7-driven plasmids for the NSP2 and NSP5 segments is increased by 3-fold in relation to that of the other nine plasmids (11 plasmid-only system). Further, it is now possible to generate recombinant RVAs even with severely less efficient infectivity by using the 11 plasmid-only system, which has not been possible with the existing approaches. More importantly, the 11 plasmid-only system does not need any helper expression plasmid, and thus this simplest and robust system has a clear advantage over the existing systems in terms of safety. This 11 plasmid-only system should contribute to the development of safe next-generation vaccines and vaccine vectors.