Species-Specific Minimal Sequence Motif for Oligodeoxyribonucleotides Activating Mouse TLR9

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Toll-like receptor 9 (TLR9) recognizes microbial DNA, initiating immune responses.
• Synthetic oligodeoxyribonucleotides (ODNs) mimic microbial DNA to activate TLR9.
• Understanding mouse TLR9 activation motifs is crucial for immunological research.

Purpose of the Study:

• To systematically investigate the sequence determinants for mouse TLR9 activation by B class phosphodiester ODNs.
• To identify the minimal sequence motif required for activating mouse TLR9.
• To compare mouse TLR9 activation motifs with those of human TLR9.

Main Methods:

• Systematic investigation of B class phosphodiester ODN sequences.
• Assessing TLR9 activation in mouse immune cells (macrophages, dendritic cells, B cells).
• Analyzing sequence properties, including CpG dinucleotide positioning and ODN length.

Main Results:

• Mouse TLR9 requires a single CpG dinucleotide located 4-6 nucleotides from the 5'-end.
• A 5'TCC sequence adjacent to the CpG augments activation.
• ODN length (23-29 nt) is optimal for dendritic cell activation, while distance from the 5'-end fine-tunes macrophage activation.
• Minimal sequences induce Th1-type cytokine synthesis and cell surface marker expression.

Conclusions:

• Mouse TLR9 exhibits distinct sequence selectivity compared to human TLR9.
• The identified minimal sequence provides insights into species-specific TLR9 activation.
• Differences in receptor binding sites likely account for interspecies variations in TLR9 activation.