Scientists at The Pirbright Institute have identified African swine fever virus (ASFV) proteins that can trigger an immune response in pigs. The team hopes to develop a vaccine using these proteins that is capable of protecting against the deadly disease.
Published in Frontiers in Immunology, the study shows that when some pigs were challenged with a virulent strain of ASF after receiving a vaccine that included the identified proteins, the level of virus in the blood was reduced. “This demonstrates that this method of vaccination could provide effective protection to pigs, though further work is needed”, said Dr Chris Netherton, Head of the ASF Vaccinology Group at Pirbright.
To determine which ASF proteins should be used in the vaccine, the team screened proteins to find those that activated immune cells in pigs, which had previously been infected by a weakened form of ASFV. The 18 proteins that generated the strongest immune cell response were then transferred into viral vectors; viruses which deliver the ASF proteins to pig cells, but are not harmful to pigs.
“ASFV has more than 150 proteins; understanding which of these triggers an immune response is difficult but crucial for creating this kind of vaccine. Now we have identified proteins that activate pig immune cells, we can work on optimising the vaccine components to ensure pigs are protected against virulent ASF strains” added Dr Netherton.
ASF infects all pigs and wild boar and can cause fever, loss of appetite, vomiting and bloody diarrhoea. The disease is often deadly, with some strains approaching case fatality rates of 100%. Although the virus does not cause disease in humans, it poses a significant threat to food security and has a substantial impact on the economy, especially on trade and farming. ASF has already resulted in the culling of over 1.1m pigs in China and nearly 2.5m pigs in Vietnam alone.
Culling, quarantine and strict biosecurity measures are currently the only defences farmers can use to prevent ASF spread. The development of a safe and effective vaccine is therefore vital for preventing the transmission of ASF, and is increasingly urgent considering the rapid spread of the disease through Europe and China. There are various types of ASF vaccine being worked on, but relatively little is known about the virus and how the immune system responds to it, which hampers progression.
Vaccines made with inactivated viruses have not offered protection to domestic pigs, and although live attenuated vaccines (which contain weakened versions of a live virus) show promise for protection, more testing is needed to ensure their safety. Pirbright researchers therefore hope that these vector vaccines will provide an alternative, which could help to control the spread of this devastating pig disease.
The UK Chief Veterinary Officer, Christine Middlemiss, said: “I welcome this research by The Pirbright Institute which demonstrates the UK’s world-leading role in developing the science and tools needed to tackle devastating animal diseases such as African swine fever. While this is encouraging progress, we continue to work closely with the UK pig sector to raise awareness of the risks and advise on maintaining high biosecurity standards, including minimising the risk of the virus infecting commercial pigs.”