Parasitic Protozoa and Interactions with the Host Intestinal Microbiota

Abstract

Parasitic protozoan infections represent a major health burden in the developing world and contribute significantly to morbidity and mortality. These infections are often associated with considerable variability in clinical presentation. An emerging body of work suggests that the intestinal microbiota may help to explain some of these differences in disease expression. The objective of this minireview is to synthesize recent progress in this rapidly advancing field. Studies of humans and animals and in vitro studies of the contribution of the intestinal microbiota to infectious disease are discussed. We hope to provide an understanding of the human-protozoal pathogen-microbiome interaction and to speculate on how that might be leveraged for treatment.

Keywords: host pathogen; microbiota; parasite; protozoa.

FIG 1

Host intestinal microbiota and interactions with host and parasite. Changes in the composition of the intestinal microbiota (image 1) may increase resistance to parasite infection at mucosal sites, such as the intestine, by mechanisms such as decreased virulence or parasite adherence (image 2). Changes in the microbiota may also alter systemic immunity to parasites by alteration of granulopoiesis or adaptive immunity (image 3). A better understanding of the mechanisms underlying microbiota-mediated protection may help explain clinical variability and help treat parasitic protozoan infections.

FIG 2

Model of SFB-mediated protection against E. histolytica colonization. SFB (segmented filamentous bacteria) colonization of the intestine may induce soluble mediators, including SAA, which may increase intestinal immune responses against ameba as well as trigger systemic epigenetic changes in bone marrow that support more-robust granulopoiesis and protection against intestinal E. histolytica infection. (Republished with modifications from mBio [83].)