Immunopathology of early and advanced epididymis lesions caused by Brucella ovis in rams

Ovine brucellosis is an infectious disease that causes alterations in the reproductive tract in ram and abortion in ewes. Their negative economic impact in ovine production warrants a thorough understanding the interactions between B. ovis and the host. Here, epididymis lesions of rams infected by B. ovis were histopathologically staged into early and advanced. Expression by immunohistochemistry of Brucella antigens, inflammatory cell markers (CD3, CD79αcy) and cytokines (IFN-γ, TNF-α, TGF-β1) was assessed in both stages. Early lesions were characterized by epithelial changes, interstitial inflammation, and mild fibrosis; whereas advanced lesions displayed caseous granulomas containing numerous macrophages, multinucleated giant cells, lymphocytes, and plasma cells. Expression of Brucella antigens were observed in both stages. The cellular response in B. ovis lesions were predominantly of T-cells (CD3+) whereas low numbers of B-cells and plasma cells (CD79αcy+) were present in both early and advanced lesions. IFN-γ was expressed by lymphocytes in early lesions suggesting that the adaptive immune response against B. ovis is initiated by Th1 cells, this response was also preserved in advanced stages. Expression of TNF-α was observed in neutrophils of epithelial microabscesses and intraepithelial T-cells of early lesions suggesting a promotion of neutrophil phagocytosis triggered by TNF-α. On the other hand, advanced lesions showed a reduction of TNF-α expression which may permit B. ovis persistence in granulomas. Lastly, TGF-β1 expression (fibroblast, macrophages and less in lymphocytes) were increased with time, suggesting that B. ovis promotes TGF-β1 secretion promoting chronicity of the lesions.