TLR9/NF-kB Pathway Regulates Brucella CpG DNA-mediated Cytokine Response in Human Peripheral Blood Mononuclear Cells

Background: It was reported that targeting the Toll-like receptor 9 (TLR9) signaling pathway can be a promising therapeutic strategy for interventions in various inflammatory and infectious diseases. However, it was not known whether the human TLR9 is responsive to Brucella cytidine-phosphate-guanosine (CpG) DNA sequences and activates the host's innate immune system. Objective: The present study aimed to identify the novel human TLR9 agonists from Brucella CpG oligodeoxynucleotide (ODN) candidates and verify their immune response regulatory mechanisms. Methods: Molecular docking methods were used to discover potent agonists of the human TLR9. The potential molecules were further validated by Western blot and enzyme-linked immunosorbent assay (ELISA). Results: The experiment results showed a strong interaction and good compatibility between the human TLR9 and Brucella ODN1molecule. In addition, the induction of immune response by Brucella ODN-1 is a CpG-specific response. Moreover, the effects of Brucella ODN-1 on cytokine response are dependent on the TLR9-mediated NF-Kappa B pathway. Conclusion: These results indicated that the Brucella ODN-1 molecule can serve as a starting point to discover or designmore potent and specific TLR9 agonists that have the potential use in the treatment of infectious diseases.