Brucella abortus is an intracellular pathogen that causes infection in cattle, leading to reproductive losses and posing a zoonotic risk to humans. Understanding host immune responses at the molecular level is essential for developing targeted diagnostics and control strategies. This study aimed to investigate the expression of immune-related genes in Bos taurus naturally infected with Brucella abortus using integrated in vivo and in silico approaches. The infection was characterized as chronic based on persistent seropositivity and historical herd records of infection for 12–18 months prior to sampling. Gene expression analysis revealed significant upregulation of NOD2 and IL10 , indicating simultaneous activation of pro-inflammatory signaling and regulatory responses during chronic infection. In contrast, TLR9 was markedly downregulated, suggesting immune evasion mechanisms that suppress endosomal DNA recognition pathways. The expression levels of TLR5 and TLR6 remained unchanged, possibly due to the pathogen’s avoidance of flagellin and lipoprotein recognition. Venn diagram and protein–protein interaction (PPI) analyses highlighted functional overlaps among genes involved in infection response, Toll-like receptor signaling, and KEGG Brucella pathways. GO and KEGG enrichment further confirmed the involvement of the MyD88-dependent TLR signaling pathway, nitric oxide biosynthesis, and pathogen recognition mechanisms. These findings emphasize the complexity of the host immune response to chronic brucellosis, where the immune system attempts to control infection while being subverted by bacterial strategies. The identified gene expression patterns not only enhance our understanding of Brucella pathogenesis but also provide potential molecular markers that could guide future strategies for disease diagnosis and therapeutic intervention. Overall, this study contributes valuable insights into the host-pathogen interactions that define chronic Brucella abortus infection in cattle.
Mabrouk et al. (Sat,) studied this question.