Chinese scientists recently reported that they have developed genetically modified pigs that are immune from the classical swine fever virus (CSFV).
Classical swine fever, caused by CSFV, is highly contagious, and the infected pigs often die within a few weeks. CSFV can be transmitted from one pig to another and also from mother to offspring. Both domestic and wild pigs can get infected with the virus.
With extensive vaccination, the disease was effectively controlled in North America, Australia and much of Europe with only sporadic outbreaks. However, it remains widespread throughout the rest of the world and control methods are limited to culls which lead to significant economic losses.
In the study, researchers from the College of Animal Sciences, China's Jilin University successfully produced anti-CSFV pigs by using the CRISPR/Cas9 gene-editing tool with the RNA interference (RNAi) technique.
CRISPR/Cas9 is like a pair of molecular scissors that have been widely used to produce genetically modified animals. The technology of RNAi has been regarded by virologists as a promising method for the suppression of viral infection.
To date, there have been several reported RNAi-based studies on CSFV suppression in vitro, indicating that the development of genetically modified pigs resistant to CSFV may be possible.
Chinese researchers performed the techniques on pigs, enabling the animals to have an innate resistance to CSFV. During a viral challenge, the 55 days old pigs were split into two rooms, each containing three gene-edited pigs, three unedited pigs, and one unedited pig infected with CSFV.
Results showed that although the gene-edited pigs were infected with the virus, their symptoms were far less severe and non-fatal and the blood virus count was also much lower. All of the unedited pigs were killed by classical swine fever.
Meanwhile, the researchers also found that the resistance to CSFV could be stably transmitted to the first-generation offspring.
The findings have been reported on the December issue of U.S. open-access journal PLOS Pathogens.
The researchers are still monitoring the safety and effectiveness of the approach as the gene-edited pigs age.
According to Ouyang Hongsheng of Jilin University, corresponding author of the research, the gene-edited strategy could be a direct and effective approach to permanently introduce disease-resistant traits into the mass population of farm pigs, and possibly other domestic species as well.