Evaluation of viral load and transcriptome changes in tracheal tissue of two hybrids of commercial broiler chickens infected with avian infectious bronchitis virus: a comparative study

Infectious bronchitis virus (IBV) is one of the major threats to the poultry industry, with significant economic consequences. Despite strict measures, the disease is difficult to control worldwide. Experimental evidence demonstrates that the severity of IBV is affected by the genetic background of the chicken, and the selection of appropriate breeds can increase production efficiency. Therefore, the aim of the present study was to assess the strength of the immune response to IBV in tracheal tissues of Ross 308 and Cobb 500 broiler chickens by evaluating transcriptome changes, focusing on immune responses and the viral load in tracheal tissues two days after IBV infection. We identified 899 and 1350 differentially expressed genes (DEGs) in the Cobb 500 and Ross 308 experimental groups compared to their respective control groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated the involvement of signaling pathways (Toll-like receptor [TLR], NOD-like receptor [NLR], and RIG-I-like receptor [RLR] signaling pathways). Interestingly, the RLR signaling pathway appears to be affected only in the Cobb hybrid. Furthermore, the viral loads in tracheal samples obtained from the Ross challenged group were significantly higher than those of the Cobb challenged group. The results of this study indicated that the host transcriptional response to IBV infection as well as the viral load can differ by hybrid. Furthermore, genes such as TLR-3, ChIFN-α, MDA5, LGP2, IRF-7, NF-κB, and TRIM25 may interfere with IBV proliferation.