Colonization with ubiquitous protist Blastocystis ST1 ameliorates DSS-induced colitis and promotes beneficial microbiota and immune outcomes

Abstract

Blastocystis is a species complex that exhibits extensive genetic diversity, evidenced by its classification into several genetically distinct subtypes (ST). Although several studies have shown the relationships between a specific subtype and gut microbiota, there is no study to show the effect of the ubiquitous Blastocystis ST1 on the gut microbiota and host health. Here, we show that Blastocystis ST1 colonization increased the proportion of beneficial bacteria Alloprevotella and Akkermansia, and induced Th2 and Treg cell responses in normal healthy mice. ST1-colonized mice showed decreases in the severity of DSS-induced colitis when compared to non-colonized mice. Furthermore, mice transplanted with ST1-altered gut microbiota were refractory to dextran sulfate sodium (DSS)-induced colitis via induction of Treg cells and elevated short-chain fat acid (SCFA) production. Our results suggest that colonization with Blastocystis ST1, one of the most common subtypes in humans, exerts beneficial effects on host health through modulating the gut microbiota and adaptive immune responses.

Blastocystis: A Mysterious Member of the Gut Microbiome

“…Some studies have demonstrated that ST1 has beneficial effects on the host gut microbiome and immune system. Deng et al showed that colonization with Blastocystis ST1 could increase the levels of Alloprevotella and Akkermansia , which are beneficial bacteria for gut health, in a murine model [ 73 ]. Blastocystis ST3, another very common subtype, has been shown to cause an increase in beneficial bacteria such as Bacillota (syn.…”

“…These data indicate subtype-specific effects of Blastocystis on immune modulation. Moreover, regarding host–microbiome interactions, the increase in diverse bacteria in the gut microbiota of Blastocystis ST1 and ST4 carriers causes SCFA production, which is important for the immune system overall and its modulation [ 73 , 96 ].…”

“…Colonization with Blastocystis ST1, ST3, and ST4, the most common subtypes of Blastocystis , was associated with enhanced potent Th2 and Treg immune responses in a murine model of experimental colitis. Colonization with ST1, ST3, and ST4, has been reported in studies to have a beneficial effect on host health by regulating the gut microbiome composition and adaptive immune responses [ 63 , 73 , 75 ].…”

“…Deng et al indicated that ST1 colonization could induce Th2 and Treg cell responses in normal, healthy mice [ 73 ]. Long-term Blastocystis ST3 colonization was reported to modify the appearance of induced colitis in a rat model of intestinal inflammation, whereas short-term colonization had no effect.…”

A tryptophan metabolite made by a gut microbiome eukaryote induces pro‐inflammatory T cells

“…The role of Blastocystis in the human microbiome, whether it is harmful or beneficial, is still the subject of debate, despite its widespread colonization among the population. The outcome of gastrointestinal tract colonization may be influenced by factors such as the composition of gut bacterial communities, the host's immune status, and, notably, the genetic background of various Blastocystis subtypes (STs), with subtypes ST1 and ST4 being beneficial and ST7 pathogenic (Ajjampur et al , 2016; Yason et al , 2019; Deng et al , 2023a,b). There is limited information on how these protists interact with the gut immune system during intestinal colonization.…”