Toll-Like Receptor-4 is Essential for Arcobacter Butzleri-Induced Colonic and Systemic Immune Responses in Gnotobiotic IL-10(–/–) Mice

Arcobacter butzleri causes sporadic cases of gastroenteritis, but the underlying immunopathological mechanisms of infection are unknown. We have recently demonstrated that A. butzleri-infected gnotobiotic IL-10(–/–) mice were clinically unaffected but exhibited intestinal and systemic inflammatory immune responses. For the first time, we here investigated the role of Toll-like receptor (TLR)-4, the main receptor for lipopolysaccharide and lipooligosaccharide of Gram-negative bacteria, in murine arcobacteriosis. Gnotobiotic TLR-4/IL-10-double deficient (TLR-4(–/–) IL-10(–/–)) and IL-10(–/–) control mice generated by broad-spectrum antibiotics were perorally infected with A. butzleri. Until day 16 postinfection, mice of either genotype were stably colonized with the pathogen, but fecal bacterial loads were approximately 0.5–2.0 log lower in TLR-4(–/–) IL-10(–/–) as compared to IL-10(–/–) mice. A. butzleri-infected TLR-4(–/–) IL-10(–/–) mice displayed less pronounced colonic apoptosis accompanied by lower numbers of macrophages and monocytes, T lymphocytes, regulatory T-cells, and B lymphocytes within the colonic mucosa and lamina propria as compared to IL-10(–/–) mice. Furthermore, colonic concentrations of nitric oxide, TNF, IL-6, MCP-1, and, remarkably, IFN-γ and IL-12p70 serum levels were lower in A. butzleri-infected TLR-4(–/–) IL-10(–/–) versus IL-10(–/–) mice. In conclusion, TLR-4 is involved in mediating murine A. butzleri infection. Further studies are needed to investigate the molecular mechanisms underlying Arcobacter–host interactions in more detail.