The Intersection of Immune Responses, Microbiota, and Pathogenesis in Giardiasis

Abstract

Giardia lamblia is one of the most common infectious protozoans in the world. Giardia rarely causes severe life-threatening diarrhea, and may even have a slight protective effect in this regard, but it is a major contributor to malnutrition and growth faltering in children in the developing world. Giardia infection also appears to be a significant risk factor for post-infectious irritable bowel and chronic fatigue syndromes. In this review we highlight recent work focused on the impact of giardiasis and the mechanisms that contribute to the various outcomes of this infection, including changes in the composition of the microbiota, activation of immune responses, and immunopathology.

The Chymase Mouse Mast Cell Protease-4 Regulates Intestinal Cytokine Expression in Mature Adult Mice Infected with Giardia intestinalis

“…A role for mast cells in controlling the G. intestinalis infection has been demonstrated in vivo in several different animal models [19,20]. Earlier studies in mice used animals less than 10 weeks of age that were treated with antibiotics before the challenge infection [7,8,22,35,61,62].…”

“…Recent research suggests that G. intestinalis can secrete a large number of immunomodulatory proteins, possibly regulating host immune responses [13][14][15][16]. However, the mechanisms on how interactions between the host and Giardia either lead to parasite clearance or to disease remain to be understood.Recent studies have shown the importance of different immune cells in giardiasis, where both innate and adaptive immunity seem to play significant roles [17][18][19]. Accumulated data suggest that there is a mixed Th1/Th2/Th17 response during giardiasis [19,20].…”

“…However, the mechanisms on how interactions between the host and Giardia either lead to parasite clearance or to disease remain to be understood.Recent studies have shown the importance of different immune cells in giardiasis, where both innate and adaptive immunity seem to play significant roles [17][18][19]. Accumulated data suggest that there is a mixed Th1/Th2/Th17 response during giardiasis [19,20]. When G. intestinalis attach to the microvillus brush border of intestinal epithelial cells (IECs) there is a production of chemokines and cytokines that will attract immune cells to the intestinal submucosa [20][21][22].…”

“…Recent studies have shown the importance of different immune cells in giardiasis, where both innate and adaptive immunity seem to play significant roles [17][18][19]. Accumulated data suggest that there is a mixed Th1/Th2/Th17 response during giardiasis [19,20].…”

Peptidylarginine Deiminase inhibition abolishes the production of large extracellular vesicles fromGiardia intestinalis, affecting host-pathogen interactions by hindering adhesion to host cells

“…While the majority of Giardia infected individuals are asymptomatic, giardiasis is a major contributor to malnutrition and growth impairment in children from developing countries (Fink & Singer, 2017). Additionally, the disease may also last for a long term as a chronic infection.…”