The discovery of potent immunostimulatory CpG-ODNs widely distributed in bacterial genomes.

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.

• Authors: Juan Liu, Yan Wei, Yongling Lu, Yangyuling Li, Qian Chen, Yan Li
• Journal: Journal of microbiology (Seoul, Korea) (J Microbiol) Vol. 58 Issue 2 Pg. 153-162 (Feb 2020) ISSN: 1976-3794 [Electronic] Korea (South)
• PMID: 31872374 (Publication Type: Journal Article)

Chemical References

• Adjuvants, Immunologic
• CPG-oligonucleotide
• Oligodeoxyribonucleotides
• Toll-Like Receptor 9

Topics

• Adjuvants, Immunologic (genetics)
• Animals
• Computational Biology
• Escherichia coli (genetics)
• Genome, Bacterial (immunology)
• Immunity, Innate
• Macrophages, Peritoneal (immunology, microbiology)
• Mice
• Oligodeoxyribonucleotides (genetics)
• Streptococcus (genetics)
• Toll-Like Receptor 9 (immunology)