Intestinal Barrier Repair in Giardiasis

Giardiasis is a common diarrheal disease caused by the protozoan parasite Giardia duodenalis. Acute symptoms can include diarrhea, but infections are often sub-clinical. It is transmitted via ingesting infectious cysts in contaminated food or water. In developing countries, giardiasis is one of the leading causes of growth stunting in children under two years old. Changes in intestinal barrier integrity have been shown to contribute to impaired nutrient absorption, thereby leading to growth stunting. Although intestinal barrier defects have been linked to infection, there is little understanding of barrier repair dynamics post-infection. Previous studies have demonstrated that Giardia infection is associated with dysbiosis in humans and animals. Because Aryl hydrocarbon receptor (AHR) signaling has been shown to promote intestinal repair in other systems, we are exploring the role of AHR in barrier repair following a Giardia infection. We quantified specific microbiome-derived AHR ligands in the plasma of infected C57BL/6 mice and observed a reduction of indole-3-ethanol and indole-3-pyruvic acid 21 days post-infection. Since IL-22 signaling can also promote barrier repair, we quantified IL-22 transcripts by RT-PCR and found significantly increased levels of IL-22 mRNA in infected mice. These data suggest that Giardia can reduce barrier repair through altered production of AHR ligands by the microbiome, but that IL-22 can counter this effect in some situations. This study will give better insight into developing effective dietary interventions to prevent growth stunting in infected children. Supported by grant from NIH AI166467