Two new genes have been identified in infectious bronchitis virus (IBV), a coronavirus that causes an acute, highly contagious and economically important respiratory disease of poultry. The research, carried out by scientists at The Pirbright Institute, raises the prospect that coronavirus genomes are more complex than previously thought. Understanding more about their basic biology can help to inform future vaccines and therapeutics.
Using state of the art genome analysis technology available in the Bioinformatics, Sequencing & Proteomics Group at Pirbright, the team of researchers were able to identify tiny fragments of the IBV genome in infected cells and eggs and show that two of them represent new virus genes.
These genes, named gene 2* and gene 7, have also been identified by researchers in other institutions, but in a paper published in the Journal of General Virology, scientists at Pirbright were able to show that gene 2* is specific to the Beaudette strain of IBV, a weakened form of the virus, while gene 7 was found in several different IBV strains, but not Beaudette.
The team used genetic engineering to insert gene 7 into the Beaudette strain to see if it changed the way the virus infected tracheal cells that are found in the airway. Normally, when these cells are infected with Beaudette they display reduced ciliary activity—the waving motion of tiny hair-like projections found on tracheal cells which usually help to clear infectious microorganisms from the airway.
However, in the tracheal cultures infected with the engineered strain of Beaudette, this effect was delayed. This indicates that gene 7 may indeed have a function, though the Beaudette strain is unusual as it is highly adapted to laboratory conditions so further work is needed to determine whether the results from this study have any implications for wild or vaccine strains of IBV.
Dr Erica Bickerton, Head of the Coronaviruses Group at Pirbright, said: “The identification of these new genes, and the potential that there are more to be found, shows there is still much to learn about coronavirus biology. Coronaviruses use a common mechanism for replication, so it is likely there are also undiscovered genes in other coronaviruses. Funding for this kind of fundamental, basic research is important as it can lead to insights into virus structure, function and replication that could have potential application for vaccines and anti-viral therapies in the future.”
This research was supported by the Biotechnology and Biological Sciences Research Council, part of UK Research and Innovation (BBSRC UKRI).
Image shows chicken cells infected with Beaudette – cell nuclei are shown in blue and the virus is shown in green and red.