A light at the end of the tunnel
There is a light at the end of the tunnel. As we continue to fight to contain ASF outbreaks, the African swine fever, it seems that a vaccine will finally be available soon, which will solve this terrible problem once and for all. This viral disease, fatal to pigs but harmless to humans, is a huge threat that worries farmers, because it spreads easily among animals and causes the atrocious death of pigs just four days after infection. The virus is extraordinarily resistant, able to survive for months in the soil of pigsties, in pork or on people's clothing. In parts of Africa and Europe, wild boars, warthogs, pigs and ticks have also contributed to the spread of the virus, creating a natural reservoir that is difficult to control. As if that wasn't enough, the virus is extremely effective at evading the host's immune system, making creating a vaccine quite difficult.
Strict biosecurity measures
This is why, until now, an effective vaccine against ASF has never been available. Currently, the only way to control its spread is through rigorous biosecurity measures, such as the rapid culling of all livestock, with incalculable economic damage to affected farmers. The loss of all the pigs can in fact have catastrophic consequences, such as the permanent closure of farms and the disappearance of entire production chains. Now, researchers at the International Livestock Research Institute (ILRI) have given exciting news, which may represent a milestone in this field: the first ASF vaccine will soon become a reality. “We have an experimental vaccine that shows 100% efficacy in controlled trials, with a very favorable safety profile,” says Lucilla Steinaa, a scientist at ILRI, who is leading the research on this new potential vaccine.
Take the virus and weaken it
The main theory behind making an effective live attenuated vaccine against ASF is to take the virus and weaken it, turning it into a form that is harmless to pigs. As ILRI scientist Hussein Abkallo explains: “When the pig is infected, its immune system responds to slow down the replication of the virus. But the virus is intelligent, as it demonstrates a level of adaptability. It has genes that help it evade the host immune system. By identifying and removing these particular genes from the virus, its ability to progress within the host and cause disease can be effectively counteracted.” However, the ASF virus has around 160 genes and the function of each one and how they interact with each other is extremely complex and often still unclear. “When you delete a gene, you don't know exactly what will happen to the virus. You can't predict it,” says Steinaa: “And finding out requires expensive and time-consuming testing on live pigs. Working out the vaccine dosage is also another challenge.”
Six years of effort
But Steinaa saw the potential of a Nobel Prize-winning technology, CRISPR/Cas9 genome editing, to generate live attenuated vaccines for ASF and other pathogens, which appears to address past challenges. Thanks to a grant from the International Development Research Center (IDRC), co-financed by the Bill & Melinda Gates Foundation, it was possible to develop this innovative approach to ILRI, i.e. a much more precise genome editing method than previous methods. With this new approach, it is essentially possible to quickly locate any specific area of a genome and replace these sections with the precision of a molecular scalpel, immediately targeting known genes in the ASF genome for rapid elimination. After six years, their efforts have brought success. “We have shown that with CRISPR/Cas9, within two months it is possible to generate multiple experimental vaccines in parallel,” says Abkallo. After successfully testing the experimental vaccine on live animals for four weeks, ILRI scientists are now seeking private sector partners to expand testing into a development phase, which will require standardized production of the vaccine.
Other research areas
According to the scientists, this method has great potential to be applied to other research areas as well. “Genome editing can also be used to make animal breeding more accurate and efficient,” Steinaa emphasizes enthusiastically: “This is indeed a technology that in the future can be used to generate live attenuated vaccines against a large variety of pathogens, facilitating the improvement of genetic resistance against diseases" (source: Assosuini).