Giardia lamblia, the Intestinal Microbiome, and Innate Immunity: A Study of the Host-Parasite Relationship during G. lamblia Infection
Maloney, Jenny G.
Infection with the protozoan parasite G. lamblia is a major cause of diarrheal disease worldwide. Prevalence is highest in developing countries with an estimated 20-30% of the population infected at any given time. G. lamblia is also common in the developed world, but as the parasite is most often transmitted through the consumption of contaminated drinking water, prevalence rates in countries with an industrialized water supply are only around 2-7%. G. lamblia infection can be a serious health concern as chronic reinfection is associated with a failure to thrive in children in areas of high prevalence. G. lamblia may also have long term health consequences associated with the development of post-infection immune disorders. G. lamblia causes epithelial barrier breakdown, defects in the epithelial brush border, and increased intestinal motility, yet no overt signs of inflammation are observed during infection. Infection may perturb the commensal bacterial populations of the host intestinal tract, and host commensal composition contributes to disease susceptibility. The interplay between the host immune system, the commensals of the small intestine, and G. lamblia are explored here. We report that G. lamblia infection alters the expression of host innate immune factors know to be important in the regulation of commensal microbes and that antibiotic treatment has a profound effect on the expression of these same innate immune factors. We also demonstrate that CD11b+, CD11c+, F4/80+, CX3CR1int, Ly6Cint, MHCII- macrophages accumulate in the mouse small intestine during infection. These cells have an immunosuppressive phenotype as they co-express ARG1 and NOS2 and have increased expression of IL-10 following infection. The results of this study could have important implications for the influence of G. lamblia on innate immune function and commensal microbe composition during infection. We also describe the accumulation of a macrophage population that could help to explain the lack of inflammation observed during G. lamblia infection. This study contributes to our understanding of the role of innate immunity and the commensal microbiota during G. lamblia infection which could be important for the design of disease control strategies in the future.
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LESS IS MORE: THE IMPLICATIONS OF GENOMIC MINIMALISM ON THE REGULATION OF GENE EXPRESSION IN THE PARASITE GIARDIA LAMBLIA Williams, Christopher Woten (Georgetown University, 2012)<italic>Giardia lamblia<italic> is one of the most common eukaryotic intestinal parasites in the world. A theme of simplified cellular machinery characterizes much of its biology with interesting consequences: a greatly ...