Scientists at The Pirbright Institute have shown that two new potential vaccines against Nipah virus developed by the University of Parma generate a strong immune response in pigs. These promising results suggest the vaccines could protect pigs against Nipah virus infection, which can cause respiratory problems and fatal encephalitis in pigs and humans. By preventing spread of the virus through pig populations, the novel vaccines would also lower the chances of humans contracting the disease.
Nipah virus typically infects bats, but pigs can become infected by consuming fruit contaminated with bat secretions. Spread of the virus from pigs to humans was responsible for the first and most severe human Nipah outbreak in Malaysia during 1998-99, where almost 200 pig farmers died after contracting the virus from infected pigs. The eradication of Nipah from pigs in Malaysia was dangerous and costly, requiring the army to cull almost half of the national herd and costing an estimated US$582 million.
In the new study, published in Vaccines, the team reported that the two vaccine candidates generated strong antibody and cellular immune responses in pigs. Since it is thought that both types of immune response are important for protection against Nipah virus, these results provide a solid basis for their further investigation in vaccine development for use in pigs and potentially other species.
To create the vaccines, scientists genetically engineered bovine herpes viruses (BoHV-4) to deliver Nipah virus proteins to pigs. The team selected the G and F proteins that Nipah virus is known to use to enter cells and facilitate cell-to-cell spread. When presented to the immune system, these proteins trigger a response that prepares the host to fight the infection.
“We were impressed by the magnitude of the immune responses stimulated by the BoHV-4 vaccines, especially the T cell responses. Our results suggest that BoHV-4 could also be used to make vaccines for other pig diseases where T cell responses are thought to play an important role in protection, such as African swine fever virus. This shows great potential for the future of this vaccine delivery system”, said Professor Simon Graham, Head of the Porcine Reproductive and Respiratory Syndrome Immunology Group at Pirbright.
Now that the team have shown the vaccine candidates induce potent immune responses, their next step will be to assess whether this will protect pigs when they are infected with the Nipah virus after receiving the vaccine. A complementary diagnostic test will also be developed that can differentiate between infected and vaccinated animals (DIVA), which would enable vaccines to be stockpiled and then utilised during outbreaks.
As emerging viruses continue to create new outbreaks around the world, preventing and controlling viral diseases that can spread from animals to people (known as zoonoses) has become a global priority. Protecting pigs from diseases such as Nipah can improve animal welfare, safeguard national economies and prevent ‘spill over’ infection to humans.
This study was funded by the VetBioNet project, European Union Horizon 2020 research and innovation programme under grant agreement N° 731014, the Biotechnology and Biological Sciences Research Council (BBSRC), part of UK Research and Innovation (UKRI) and with the support of the Erasmus+ Programme of the European Union (Master LIVE for vaccinology).
This research was also funded by the Department of Health and Social Care as part of the UK Vaccine Network (UKVN), a UK Aid programme to develop vaccines for diseases with epidemic potential in low and middle-income countries (LMICs).
Image: Colourised transmission electron micrograph of a Nipah Virus particle (green) near the edge of an infected cell (blue). Image captured and colour-enhanced at the NIAID Integrated Research Facility in Fort Detrick, Maryland. Credit: NIAID