Scientists at the UK’s Pirbright Institute, working in collaboration with the University of Oxford and the pharmaceuticals giant Astra Zeneca, have shown how a prospective Covid-19 vaccine for humans can successfully boost a pig’s immune response to the virus.
The studies, which have yet to be peer reviewed, indicate that two doses of the ChAdOx1 nCoV-19 (AZD1222) vaccine produce a greater antibody response than a single dose in pigs.
In a press release sent to AFN this week, Professor Bryan Charleston, who directs the Pirbright Institute, explained why a successful response in pigs was an important step in the development of Covid-19 vaccines for humans.
“The pig has proved to be a valuable model for testing human vaccines for other diseases to give an indication of the type of immune response induced and testing different doses,” he said. “Pigs are more physiologically similar to humans than some other animal models, for example their body weight and metabolic rate, and are more accessible than studies using non-human primates.”
Professor Simon Graham, lead author of a study that can be read here, described the results as “very encouraging.” Stephen Griffin, an associate professor at Leeds University who was not directly involved in this work, agreed, telling Reuters it was “an encouraging advance.”
A virus with more profound impacts than Covid-19
The work is running in parallel with other major vaccinology research into pigs that AFN has been monitoring closely over the last few months at Pirbright — the development of a vaccine for African Swine Fever (ASF).
Rabobank’s global strategist Justin Sherrard reckons this virus will have “more profound and long-lasting impacts on global animal protein markets than Covid-19.” Already, as his firm’s June update on ASF notes, hundreds of millions of pigs have been culled across Asia, with a high proportion of these in China. More recently, outbreaks have surfaced again in Europe and Africa; the BBC reported a few days ago that Nigeria was a new ASF hotspot, with farmers there reportedly culling at least 300,000 pigs.
In light of this, the World Organisation for Animal Health (OIE) has warned the disease could kill a quarter of the world’s pigs, partly due to the absence of a commercially-available vaccine.
A study by Pirbright, published this May in Vaccines, showed that 100% of pigs immunised with the new vaccine were protected from a lethal dose of ASF virus (ASFV).
The team created what is known as a vectored vaccine by inserting eight strategically selected ASFV genes into a non-harmful virus, known as a vector. Vectors are used to deliver the genes to pig cells where they produce viral proteins that prime the pig immune system to rapidly respond to an ASF infection. The combination of eight virus genes protected pigs from severe disease after challenge with an otherwise fatal strain of ASFV, although clinical signs of disease did develop. This is the first time that a vectored vaccine has shown a protective effect against ASF. Further development is needed, but if successful, this vaccine would enable the differentiation of infected animals from those that have received a vaccine (DIVA), which would allow vaccination programmes to be established without sacrificing the ability to trade.