Abstract
Shigella dysenteriae causes the most severe of all infectious diarrhoeas and colitis. We infected rhesus macaques orally and also treated them orally with a small and non-absorbable polypropyletherimine dendrimer glucosamine that is a Toll-like receptor-4 (TLR4) antagonist. Antibiotics were not given for this life-threatening infection. Six days later, the clinical score for diarrhoea, mucus and blood was 54% lower, colon interleukin-8 and interleukin-6 were both 77% lower, and colon neutrophil infiltration was 75% less. Strikingly, vasculitis did not occur and tissue fibrin thrombi were reduced by 67%. There was no clinical toxicity or adverse effect of dendrimer glucosamine on systemic immunity. This is the first report in non-human primates of the therapeutic efficacy of a small and orally bioavailable TLR antagonist in severe infection. Our results show that an oral TLR4 antagonist can enable controlled resolution of the infection-related-inflammatory response and can also prevent neutrophil-mediated gut wall necrosis in severe infectious diarrhoeas.