Raising the prospect that coronavirus genomes are more complex than previously thought, two new genes have been identified in infectious bronchitis virus (IBV), which is a coronavirus that causes an acute, highly contagious and economically important respiratory disease of poultry, according to researchers at The Pirbright Institute in the U.K.
Understanding more about the basic biology of IBV and other coronaviruses can help inform future vaccines and therapeutics, Pirbright said.
Using state-of-the-art genome analysis technology available in the Bioinformatics, Sequencing & Proteomics Group at Pirbright, the research team was 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 at other institutions, but in a paper published in the Journal of General Virology, the Pirbright researchers 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, the Pirbright announcement said. Normally, when these cells are infected with the Beaudette strain, they display reduced ciliary activity — the waving motion of tiny hair-like projections found on tracheal cells that usually helps 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 indeed may have a function, although the Beaudette strain is unusual in that 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, the researchers acknowledged.
“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,” Dr. Erica Bickerton, head of the Coronaviruses Group at Pirbright, said. "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 antiviral therapies in the future."