Abstract
Oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG-ODN) can be specifically recognized by Toll-like receptor 9 (TLR9), provoking innate immune responses. Designed according to this structural feature, many synthetic phosphorothioate CpG-ODNs successfully activate macrophages. However, it is difficult to find potent stimulatory CpG-DNA fragments in microbial genomes. Therefore, whether microbial CpG-DNA substantially contributes to infectious and immune diseases remains controversial. In this study, high-throughput scanning was carried out for thousands of bacterial genomes with bioinformatics tools to comprehensively evaluate the distribution of CpG-DNA fragments. A random sampling test was then performed to verify their immunostimulatory properties by experiments in vitro and in vivo. Natural TLR9-dependent and potent stimulatory CpG-DNA fragments were found in microbial genomes. Interestingly, highly conserved stimulatory CpG-DNA fragments were found in 16S and 23S rDNA sequences with multiple copies, while others were species-specific. Additionally, we found that the reported active motifs were mostly non-stimulatory in natural CpG fragments. This evidence indicates that the previous structural descriptions of functional CpG-ODNs are incomplete. Our study has assessed the distribution of microbial CpG-DNA fragments, and identified natural stimulatory CpG-DNA fragments. These findings provide a deeper understanding of CpG-ODN structures and new evidence for microbial DNA inflammatory function and pathogenicity.
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01 April 2020
In the article by Liu et al. published in Journal of Microbiology 2020; 58, 153���162, 1# The Supplementary data���s consecutive numbers (Supplementary data Fig. S2) on 9th line of 4th paragraph in the section of ���Discussion.��� on page 160 should be corrected in (Supplementary data Fig. S1). The sentence should have read: The results showed that the nonspecific internalization of T03 had only a slight competition with CpG-ODNs (Supplementary data Fig. S1).
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Acknowledgments
Thanks to Professor Jianping Xie for providing the experimental training for Juan Liu. This work was supported by the National Natural Science Foundation of China (Grant no. 81373133).
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Liu, J., Wei, Y., Lu, Y. et al. The discovery of potent immunostimulatory CpG-ODNs widely distributed in bacterial genomes. J Microbiol. 58, 153–162 (2020). https://doi.org/10.1007/s12275-020-9289-y
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DOI: https://doi.org/10.1007/s12275-020-9289-y