Comparison of gE/gI- and TK/gE/gI-Gene-Deleted Pseudorabies Virus Vaccines Mediated by CRISPR/Cas9 and Cre/Lox Systems

Pseudorabies (PR), caused by pseudorabies virus (PRV), is an acute and febrile infectious disease in swine. To eradicate PR, a more efficacious vaccine needs to be developed. Here, the gE/gI- and TK/gE/gI-gene-deleted recombinant PRV (rGX Delta gE/gI and rGX Delta TK/gE/gI) are constructed through CRISPR/Cas9 and Cre/Lox systems. We found that the rGX Delta TK/gE/gI was safer than rGX Delta gE/gI in mice. Additionally, the effects of rGX Delta gE/gI and rGX Delta TK/gE/gI were further evaluated in swine. The rGX Delta gE/gI and rGX Delta TK/gE/gI significantly increased numbers of IFN-gamma-producing CD4+ and CD8+ T-cells in swine, whereas there was no difference between rGX Delta gE/gI and rGX Delta TK/gE/gI. Moreover, rGX Delta gE/gI and rGX Delta TK/gE/gI promoted a PRV-specific humoral immune response. The PRV-specific humoral immune response induced by rGX Delta gE/gI was consistent with that caused by rGX Delta TK/gE/gI. After the challenge, swine vaccinated with rGX Delta gE/gI and rGX Delta TK/gE/gI showed no clinical signs and viral shedding. However, histopathological detection revealed that rGX Delta gE/gI, not rGX Delta TK/gE/gI, caused pathological lesions in brain and lung tissues. In summary, these results demonstrate that the TK/gE/gI-gene-deleted recombinant PRV was safer compared with rGX Delta gE/gI in swine. The data imply that the TK/gE/gI-gene-deleted recombinant PRV may be a more efficacious vaccine candidate for the prevention of PR.