Repetitive extragenic palindromic DNA sequences from Brucella melitensis stimulate Toll-like receptor 9 signaling in macrophages

Yu,Hui; Bai,Liyun; Zhang,Yaxian; Wang,Zhanli; Yu,Yongchun

doi:10.3892/mmr.2016.5990

Repetitive extragenic palindromic DNA sequences from Brucella melitensis stimulate Toll-like receptor 9 signaling in macrophages

Authors:
- Hui Yu
- Liyun Bai
- Yaxian Zhang
- Zhanli Wang
- Yongchun Yu
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Affiliations: Central Laboratory, Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200071, P.R. China, Department of Laboratory Medicine, The First Affiliated Hospital, Baotou Medical College, Baotou 014010, P.R. China, Department of Epidemiology, School of Public Health, Baotou Medical College, Baotou 014060, P.R. China
Published online on: December 6, 2016 https://doi.org/10.3892/mmr.2016.5990
Pages: 271-276

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Abstract

Brucella DNA activates the host innate immune system via the intracellular Toll-like receptor 9 (TLR9). However, the Brucella DNA sequences which are responsible for these immunostimulatory effects remain to be elucidated. The present study demonstrated that repetitive extragenic palindromic (REPs) sequences present in Brucella DNA were able to stimulate macrophages through TLR9. The induction of interferon-α (IFN-α) production by Brucella REPs was detected in cultured RAW264.7 mouse macrophages as well as in Wistar rats. Knockdown of TLR9 expression by siRNA in macrophages led to a reduction in IFN-α production following REPs stimulation. In addition, it was confirmed that the activating capacity of Brucella REPs is CpG dependent. Induction of IFN-α by Brucella REPs was completely abrogated when REP sequences were transformed into non-CpG sequences or by C-methylated modifications. Furthermore, it was observed that REPs-initiated TLR9/NF-κB and TLR9/MAPK signaling pathways contributed to the production of IFN-α. The identification of Brucella REPs as natural TLR9 agonists may be useful for the development of novel therapeutic applications.

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