Gene-edited pigs immune to swine fever
Using CRISPR to modify pig genome shows promise against deadly disease. Andrew Masterson reports.
A team of researchers from China has created genetically modified pigs that are immune to the devastating disease classical swine fever (CSF).
CSF is caused by classical swine fever virus (CSFV), and is present in domestic pig and wild boar populations across the globe. It is extremely virulent and highly contagious.
Some cases are asymptomatic, meaning that persistently infected carriers shed the virus copiously without being detected. Symptomatic variants cause severe and distressing symptoms leading to death – if euthanasia doesn’t intervene – in seven to 10 days. Some outbreaks result in 100% mortality, and multi-billion-dollar damage bills.
Currently, the primary defence against CSF outbreaks is vaccination, with 22 countries having a compulsory program. More than 90% of pigs in any population must be vaccinated for the strategy to work.
The approach is costly, time consuming and labour-intensive, and in some areas compliance is low. The disease remains widespread in South and Central America, eastern Europe and substantial parts of Asia and Africa.
Now, however, Zicong Xie from the College of Animal Sciences at China’s Jilin University, and colleagues, might have come up with a solution: pigs that are genetically rewired to resist the virus.
In a paper published in the journal PLOS Pathogens, the researchers report using CRISPR/Cas9 gene-editing technology to select antiviral small hairpin RNAs (shRNAs) and inserting them into a genome location known as Rosa26. (The location is well understood, and a frequent target for genetic modification in mouse models.)
The modified DNA was then transferred back into its pig hosts. Xie’s team report that subsequent in vitro and in vivo tests conducted on the offspring revealed that the “pigs could effectively limit the replication of CSFV and reduce CSFV-associated clinical signs and mortality”.
Furthermore, the same resistance was passed on to the subsequent generation.
The scientists describe their work to date as a “proof of principle study”. Clearly, more research is needed, but Xie and colleagues are enthusiastic about the prospects.
“We believe that the use of [transgenic] pigs can contribute to reduction of CSFV-related economic losses and could have financial benefits,” they conclude.
“Additionally, this antiviral strategy is technically applicable to other domestic species and will provide insights for future antiviral research.”