Single-dose IBV vaccine under development

IBV is a coronavirus that causes a highly contagious disease in poultry, resulting in respiratory symptoms which affect the reproductive tracts of birds, in turn threatening the health and welfare of the birds, and food security.

Past research at Pirbright highlighted important targets in the virus genome that could be investigated to create safer vaccines. And now recent research, published in the Journal of Virology, aimed to explore these targets, and understand the mechanisms of weakening a virus to create a vaccine, a process known as attenuation.

Amino acid changes

Researchers found that attenuation of IBV was caused by changes located in non-structural proteins, and that the 2 specific amino acids were responsible for this. Research showed that these amino acid changes resulted in the virus being less able to cause disease in poultry. The researchers then investigated how changes in these amino acids weakened the virus.

Results

The 2 amino acids were found to be associated with temperature-sensitive replication of IBV, meaning that the attenuated virus is less able to replicate at higher temperatures, a characteristic which can be advantageous for vaccine development.

The internal body temperature of a chicken is 41°C (compared to 37°C for humans). A virus is less able to multiply at 41°C and is therefore less able to cause severe disease in chickens. This makes it suitable to be used as a vaccine and has the potential to provide high levels of immunity and protect against severe infection in poultry.

Researchers then moved on to investigate if this attenuated IBV strain could provide protection against disease-causing strains of IBV. They found that vaccination provided 100% protection from disease, demonstrating that the temperature sensitivity characteristic could be used to develop new vaccines against this challenging disease.

Dr Erica Bickerton, head of the coronaviruses group at Pirbright, said: “An effective vaccine for IBV could improve the health and welfare of poultry globally. It could also benefit the economy by protecting farmers’ livelihoods and protecting food security.

“This research opens opportunities to create novel, innovative vaccines that could be effective against many strains of IBV and potentially reveals ways to create vaccines for other viruses in the coronavirus family.”

The work was supported with grant funding from the Biotechnology and Biological Sciences Research Council (BBSRC) and the study can be found at A Temperature-Sensitive Recombinant of Avian Coronavirus Infectious Bronchitis Virus Provides Complete Protection against Homologous Challenge | Journal of Virology (asm.org)