March 30, 2023
French government agency lab close to creating new ASF vaccine
A vaccine to combat African swine fever (ASF) could be produced based on research carried out by the Ploufragan-Plouzané-Niort Laboratory of French government agency ANSES.
The initial results obtained are promising and are paving the way for an effective means of combating this disease, which is responsible for high mortality rates in pigs and wild boar in several countries in Europe, Asia and the Caribbean.
As part of its mandate as National Reference Laboratory for ASF, the Pig Virology and Immunology (VIP) Unit of the Ploufragan-Plouzané-Niort Laboratory inactivated the Georgia 2007/1 viral strain, which is currently circulating in the European Union. While monitoring the effects of this heat inactivation, it happened to detect an attenuated strain derived from the Georgia strain. This strain only caused a slight fever in infected animals, whereas infection with the Georgia strain is normally fatal in 100% of cases.
The team carried out a series of studies with this attenuated strain and confirmed that most pigs inoculated intramuscularly or oronasally with this virus showed only mild symptoms. Although safety was not perfect, survival was much better than with the original viral strain.
"Intramuscular vaccination is the method most commonly used on farms," said Marie-Frédérique Le Potier, head of the VIP Unit. "Oral vaccination could be used to vaccinate wild boar using bait. This method was used for classical swine fever in the early 2000s and eradicated the disease from areas of France where it was present. That is why we tested both routes of administration from the beginning".
Another promising result is that infected pigs develop an immune response, which allows them to resist infection with the ASF virus without showing any symptoms, as early as two weeks after vaccination. These results were published in the journal Viruses in December 2022.
ANSES scientists continued to work on the attenuated strain, so that it could multiply in cell lines produced in vitro and not in cells that had to be taken from pigs, as had initially been the case. This step was a success, raising the possibility of producing the vaccine on a large scale. Additionally, the strain of virus produced in this way caused fewer symptoms than the original attenuated strain, while still being effective.
Studies are still under way to ensure that this attenuated strain cannot be transmitted from one animal to another or become virulent again. The scientists will also assess the ability of the vaccine to prevent animals that are vaccinated and then exposed to the pathogenic ASF virus from retransmitting the virus.
The vaccine developed by ANSES scientists has the advantage of not being produced by genetic manipulation, making it easier to authorise its use in the wild. Wild boar may be the first target for the vaccine in Western Europe. This is the most affected species and the presence of the virus in wildlife constitutes a risk for pig farms.
The laboratory had filed a patent for the vaccine that was published last August. The Ouest Valorisation Technology Transfer Office (TTO) is supporting ANSES in encouraging interested manufacturers to exploit this patent.