Bovine toll-like receptor 9: a comparative analysis of molecular structure, function and expression

Area of Science:

• Immunology
• Molecular Biology
• Veterinary Science

Background:

• Non-methylated CpG motifs in microbial DNA are pathogen-associated molecular patterns (PAMPs).
• Toll-like receptor 9 (TLR9) recognizes CpG motifs, initiating immune responses.
• Species-specific differences exist in TLR9 expression and CpG oligodeoxynucleotide (ODN) responses.

Purpose of the Study:

• To compare the structure, function, and cellular distribution of bovine TLR9 with human and mouse TLR9.
• To investigate species-specific immune responses to CpG ODN in cattle.

Main Methods:

• Sequence homology analysis of the bovine TLR9 gene compared to human and mouse.
• Functional assays using CpG ODN to stimulate bovine leukocytes.
• Magnetic activated cell sorting to identify leukocyte subpopulations involved in CpG ODN response.

Main Results:

• Bovine TLR9 shows greater sequence homology to human TLR9 than to mouse TLR9.
• Similar CpG motifs optimally activate human and bovine leukocytes, distinct from mouse leukocytes.
• Class A CpG ODN are more potent inducers of interferon-alpha (IFN-alpha) in bovine leukocytes than class B CpG ODN.
• Dendritic cells, not monocytes, regulate CpG ODN-induced IFN secretion in cattle.

Conclusions:

• Bovine TLR9 structure and function are conserved with human TLR9 in blood leukocytes.
• CpG ODN-induced immune responses in cattle share similarities with humans, not mice.
• These findings highlight conserved innate immune recognition pathways across species.