The team hopes to develop a vaccine using these proteins that is capable of protecting against the deadly pig 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.
Dr Chris Netherton, Head of the ASF Vaccinology Group at Pirbright said: “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”.
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.
The development of a safe and effective vaccine is vital for preventing the transmission of ASF. The rapid spread of this fatal pig disease through Europe and China has already decimated pig populations, resulting 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 its spread.
Various types of vaccine are being developed, 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.”