Differential expression of inflammatory and immune response genes in rams experimentally infected with a rough virulent strain of Brucella ovis.

Infection of sheep with Brucella ovis results in ovine brucellosis, a disease characterized by infertility in rams, abortion in ewes and increased perinatal mortality in lambs. During the course of the infection both the ovine immune response and host cell gene expression are modified. The objective of this research was to conduct a preliminary characterization of differential gene expression in rams experimentally infected with B. ovis by microarray hybridization and real-time RT-PCR. Of the 600 ruminant inflammatory and immune response genes that were analyzed in the microarray, 20 and 14 genes displayed an expression fold change >1.75 with a P-value <0.05 at 15 and 60 days post-challenge (dpc), respectively. Of these genes, 16 were upregulated and 4 were downregulated in infected rams at 15 dpc. At 60 dpc, 11 and 3 genes were up- and down-regulated in infected rams, respectively. Only four genes, desmoglein, epithelial sodium channel, alpha subunit (ENaC-alpha), interleukin 18 binding protein (IL18BP) and macrophage migration inhibition factor (MIF) were found upregulated in infected rams at both 15 and 60 dpc. The analysis of differentially expressed genes demonstrated activation of inflammatory and innate immune pathways in infected animals. B. ovis infection also resulted in upregulation of genes involved in phagocytosis and downregulation of protective host defense mechanisms, both of which may contribute to the chronicity of B. ovis infection. The gene expression profiles differed between rams with severe and moderate B. ovis infection. This is the first analysis of differential gene expression in rough brucellae and particularly in B. ovis-infected rams. The characterization of the genes and their expression profiles in response to B. ovis infection further contributes to our understanding of the molecular mechanisms of infection and the pathogenesis of brucellosis.