A simple and rapid approach to manipulate pseudorabies virus genome by CRISPR/Cas9 system

The broad host range of pseudorabies virus (PRV) and large capacity for foreign DNA make it a promising vector for the development of vaccines and agents of gene therapy. We show that up to 100 % viral gene disrupting efficiency was achieved by simple co-transfection of the purified PRV genomes with the clustered regularly-interspaced, short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) into cells. Furthermore, CRISPR/Cas9-mediated knock-in of > 4-kb-long DNA cassettes into the PRV genome at a positive rate of 50 % by a homology-independent DNA repair mechanism without constructing homology arms. This approach requires only a simple plasmid construction and is applicable to knock-in of other foreign genes. Our studies offered simple and efficient methods to manipulate PRV.