ConclusionsWe reported an efficient ExnaseTMII-based in vitro recombi-nation approach for influenza gene cloning for influenza virusrescuing. In this strategy, influenza genes could be rapidly clonedthrough one PCR and a single ground of in vitro recombination,which was independent of any restriction enzyme, ligase and viralsequence information. And the high efficacy of our strategy wasevaluated and confirmed by cloning the eight genes from virusesPR8 and WS1. The results demonstrate that the cloning approachfor influenza genes developed here could speed and simplify theprocess of influenza gene cloning into reverse genetics system