Classical swine fever (CSF) caused by classical swine fever virus (CSFV) is one of the most detrimental diseases, and leads to significant economic losses in the swine industry. Despite efforts by many government authorities to stamp out the disease from national pig populations, the disease remains widespread.
Here, antiviral small hairpin RNAs (shRNAs) were selected and then inserted at the porcine Rosa26 (pRosa26) locus via a CRISPR/Cas9-mediated knock-in strategy. Finally, anti-CSFV transgenic (TG) pigs were produced by somatic nuclear transfer (SCNT).
We decided to perform animal challenge experiments with an “in-contact” infectious mode of infection. Next, all of the pigs were randomly distributed into two separate rooms, and each room included one non-TG pig that was used CSFV infection (NTG-In), three NTG pigs and three TG pigs. After three days of acclimation, these NTG-In pigs were directly challenged with CSFV by intramuscular injection, while the other housed pigs were not injected so that the natural spread of CSFV via cohabitation would be mimicked. During the course of infection, CSFV-associated clinical symptoms (including lethargy and haemorrhage), mortality and viremia in the challenged pigs were monitored and recorded daily. The results showed that all of the NTG pigs developed typical signs of CSFV infection, with a mortality rate of 100%. Although CSFV-associated clinical symptoms were also observed in the TG pigs, these symptoms were not serious, and the virus levels in the blood were lower in the TG pigs than in the NTG pigs.
Notably, in vitro and in vivo viral challenge assays further demonstrated that these TG pigs could effectively limit the replication of CSFV and reduce CSFV-associated clinical signs and mortality, and disease resistance could be stably transmitted to the F1-generation.
Altogether, our work demonstrated that RNA interference (RNAi) technology combining CRISPR/Cas9 technology offered the possibility to produce TG animal with improved resistance to viral infection.
The use of these TG pigs can reduce CSF-related economic losses and this antiviral strategy may be useful for future antiviral research.
Xie Z, Pang D, Yuan H, Jiao H, Lu C, Wang K, et al. (2018) Genetically modified pigs are protected from classical swine fever virus. PLoS Pathog 14(12): e1007193. https://doi.org/10.1371/journal.ppat.1007193