Canada’s Vaccine and Infectious Disease Organization is working to create the safest and most effective version of a vaccine to prevent African Swine Fever
By Jackie Clark
Western Canada is home to the Vaccine and Infectious Disease Organization (VIDO), an international research centre currently contributing to efforts to develop a vaccine for African Swine Fever (ASF). After considering both effectiveness and safety of vaccine types, researchers at VIDO have decided to work on a viral vector vaccine.
“We think it gives you the best chance of success. It gives the best immune response without having the problems that are included in the live attenuated vaccine. It’s safe, it doesn’t cause any disease by itself, there is no risk of virus spreading,” Dr. Volker Gerdts, director and CEO of VIDO, told Farms.com.
Scientists in China and Spain are working on live attenuated ASF vaccines; however, these include the live virus and therefore pose a risk of the virus shedding and spreading to previously uninfected pigs, Gerdts explained. The third type of vaccine involves using small pieces of the virus, called antigens, and this is referred to as a subunit vaccine.
“The subunit vaccine is also very safe,” Gerdts said. “The issue is that we still don’t know which parts of the virus are protective.”
“If you have that, then the subunit vaccine may work, if you have strong antigens with it,” he added.
At VIDO, researchers are identifying those same protective antigens, but instead of using the subunit method, they’re putting them into a different virus to act as a method of vaccine delivery.
Researchers “can put (the antigens) in these viral vectors, and now you have a delivery system that delivers the antigen for you. It brings a lot of advantages in that it induces a better immune response,” Gerdts said.
“We all are still in the process of finding a vaccine that works,” Gerdts said. The most advanced vaccine currently is a live attenuated vaccine developed in China, which will likely hit the marketplace first.
“All the others, the subunit and also viral vector vaccines, are still in pre-clinical and clinical development. It’s going to take years before we have one that’s ready to be used,” Gerdts explained.
Though a live attenuated vaccine on the market may help the ASF crisis in China, Gerdts thinks it is unlikely to be used in Canada.
“In my opinion, no one in North America is going to use a live attenuated vaccine for ASF, because the risk is just too big that the virus starts to shed and somehow will make its way into feral pigs or wild pigs and then it’s very difficult for us to control the disease in the future,” he said.
“Realistically I think that most countries would not introduce a live attenuated vaccine as part of their immunization regime, unless they are in a situation like China is,” he added.
There are many strains of ASF, called genotypes, and the one circulating right now is just one genotype.
“The long-term goal for this disease would be to have a vaccine that also protects against other genotypes,” Gerdts explained. It would be advantageous for researchers to develop a “DIVA” vaccine, which means differentiate infected from vaccinated animals. DIVA vaccines are important for international trade.
“You can demonstrate to other countries that you vaccinated the animals in your country, but you don’t have the actual virus,” Gerdts said.
This research was being conducted with partners in Africa prior to the ASF breakout in China and will still require years of work to come to fruition. VIDO is also collaborating on different aspects of ASF with labs in the U.S. and Germany.