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-gamma 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.