Studying the regulation of immune signalling molecules related to immunity during Avibacterium paragallinarum infection
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Infectious coryza is a contagious and acute upper respiratory poultry disease caused by Avibacterium paragallinarum, that plagues predominantly layers but also affects broiler breeds. The chicken’s immune response to Av. paragallinarum serovar C-3 (SA-3) infection (reported to be most virulent in South Africa), and the underlying genetic mechanisms involved, are poorly understood and not well documented. The aim of the study is to understand the complexity of the regulation of immune functions by identifying the molecules that are expressed during Av. paragallinarum serovar C-3 (SA-3 strain) infection. In this study, chickens (control versus experimental groups) were directly challenged via infraorbital injection with Av. paragallinarum serovar C-3 (SA-3 strain) and the immune response was monitored. The mean disease score and mean daily egg production score were recorded and calculated. Blood and sera were obtained for blood microscopy, leukocyte population profiling by flow cytometry analysis, and antibody/cytokine screening with ELISA assays. Finally, control and experimental chickens were sacrificed based on the clinical scores obtained (0, 1, 2 or 3). Post-mortem examination was conducted, and organs were harvested for immunohistochemistry staining for identification of distinct immune cell populations. The in vivo results obtained from the experimental studies in combination with the in silico results obtained from bioinformatics tools for the generation of immune signalling pathway maps may provide insight and a birds-eye view into the immune mechanisms between host-pathogen interactions for this disease. Results from our study could potentially assist with diagnostic tests for serovar C-3 and provide insight towards more efficient vaccine development. Hence, if vaccine practices are improved this will limit importations of birds from huge global markets, thus preventing carry-over poultry diseases and zoonosis as well as maintaining a safe and sustainable economy.