Deciphering the immune response to infectious bronchitis virus (IBV) in chickens: Advances in understanding infectious bronchitis

Authors: Dr. Neda Barjesteh, Dr. Faizel Careem, Kelsey O'Dowd, Dr. Martine Boulianne, Dr. Charles M. Dozois, Dr. Carl A. Gagnon

University of Montreal, University of Calgary, Institut national de la recherche scientifique

Article published in La Terre de chez nous on August 26, 2024: https://www.laterre.ca/chroniques/page-de-conseils/bronchite-infectieuse-decryptage-de-la-reponse-immunitaire-des-poulets/?fbclid=IwY2xjawE9UXtleHRuA2FlbQIxMQABHfuQY-z8hwGWuhQdrVbwR2GPgLfQL69M6HGPowagCD_nvcLwnGpAEjKEYQ_aem_MsG75r9TrPtCfnssN7Rvgg

Infectious bronchitis virus (or IBV) represents a major threat to poultry farms, causing respiratory tract infections in chickens, as well as decreases in egg production and false layers. The severity of the disease depends on several factors, including the virus strain, environmental conditions and the vaccination status of the chickens.

When a chicken is infected with IBV, it may show signs such as loss of appetite, sneezing, coughing and difficulty breathing, with a higher incidence in young chicks. Transmission of the virus occurs quickly, generally within two days, by air or by direct contact.

Despite the existence of vaccines, the diversity of IBV strains complicates the total protection of poultry against this disease. Sometimes, even after being infected with one strain of IBV, a chicken can still contract another strain of the virus. The emergence of a new variant, IBV Delmarva (DMV)/1639, prevalent in Eastern Canada, accentuates the challenges facing breeders. This variant is known to cause problems such as laying disorders or false laying syndrome.

To better understand the interaction between the IBV and the host immune system, researchers evaluated the host immune responses to varying strains of IBV. Once the virus enters the chickens' respiratory tract, innate defense mechanisms are activated, including the release of antiviral molecules. However, IBV is capable of counteracting these defenses, highlighting the importance of understanding the mechanisms of action to develop effective control strategies.

This study particularly focuses on specific cells in the chicken respiratory tract called tracheal epithelial cells, which are the first cells in contact with IBV. These cells act as guardians protecting the chickens' respiratory system from viruses. By examining two IB virus strains, DMV/1639 and Mass41, the researchers observed that these cells react differently depending on the strain of the virus and the time of infection. Researchers focused on both in vitro and in vivo studies to evaluate host responses to different strains of the virus and have a better understanding of host-virus interactions.

Researchers found the impact of different strains of the virus on the profile of epithelial cells transcriptome following the infection. In addition, researchers highlighted the transcriptome of epithelial cells over the time following the infection representing the dynamic of host response during the infection.  However, in both cases, as the infectionprogresses, the homeostasis of the chicks is disrupted and more genes are “activated” to defend against IBV infection.

In this particular study, underlying mechanisms involved in antiviral responses were investigated which shed lights on identifying new innovative approaches for control of respiratory viral infections in chickens.

The study of the immune response of chickens against IBV represents a crucial area of research for poultry health. By combining in vitro and in vivo approaches, researchers have identified molecular signatures specific to each strain of the virus, thus offering avenues to better understand the pathogenesis of the disease and develop more effective interventions. Future work will need to expand on these findings, including validating the results at the protein level and further exploring interactions between the virus and the host. This study was initiated by Neda Barjesteh and Kelsey O’Dowd.