Recombinant PRV Expressing GP3 and GP5 of PRRSV Provides Effective Protection Against Coinfection With PRV and PRRSV.

Porcine Reproductive and Respiratory Syndrome (PRRS) and Pseudorabies (PR) are highly contagious diseases caused by Porcine Reproductive and Respiratory Syndrome virus (PRRSV) and Pseudorabies virus (PRV). Due to the limited protective ability of currently commercialized vaccines against NADC30-like PRRSV and PRV variants, the pathological damage caused by coinfection of these two viruses has a significant impact on China's pig farming industry. In this study, six recombinant PRV stains with TK and gI/gE deletions and fused expression of GM-CSF and GP3 and GP5 proteins from NADC30-Like PRRSV were constructed by using the HDR-CRISPR/Cas9 system. After assessing growth characteristics and genetic stability, four strains demonstrating stable proliferation and expression of the GM-CSF, GP3, GP5 fusion protein in BHK-21 cells were selected. Evaluation of their ability to induce specific humoral and cellular immune responses in mice led to the selection of two strains with superior immunogenic effects: rPRV-ΔTK-GP3-GP5-eGFP-ΔgI/gE-mCHERRY-B and rPRV-ΔTK-eGFP-ΔgI/gE-GP3-GP5-mCHERRY-B. These strains were found to enhance NADC30-like PRRSV and PRV-specific immune responses in piglets, reduce pathological damage, and accelerate symptom resolution. In general, PRV is a promising viral vector for expressing PRRSV genes, and the data from this study provides references for new candidate vaccines against PRRSV.