Bovine leptospirosis is a widespread zoonotic disease, leading to serious economic losses in beef production and causing potential hazards to human health. It has been known that Leptospira species possess lipopolysaccharides (LPS), which are responsible for the leptospirosis pathogenicity, but little is known about the bovine immune response to leptospiral LPS. In this study, we evaluated leptospiral LPS-induced cytokine production in bovine cells by ELISA, and quantitatively measured toll-like receptor 2 (TLR2) and toll-like receptor 4 (TLR4) using real-time PCR and western blotting. In addition, the major toll-like receptors (TLRs) were determined through using anti-TLRs antibodies. We used Escherichia coli LPS as a positive control. Leptospiral LPS showed the ability to induce pro-inflammatory cytokine production in bovine fibroblasts that was significantly suppressed by the anti-TLR2 antibody. These results indicate that TLR2 is the main receptor for leptospiral LPS, inducing pro-inflammatory cytokine production in bovine cells, while cytokine induction by E.coli LPS was dependent on both TLR2 and TLR4. This suggests that leptospiral LPS differs from E. coli LPS in the receptors by which it is recognized in bovine cells, and that the TLR2-dependent pathway might play a significant role in leptospiral LPS-induced bovine chronic inflammatory disease.

Key words: Bovine fibroblasts, Leptospiral lipopolysaccharide, Toll-like receptors