Antioxidant defence systems in the protozoan pathogen Giardia intestinalis.

The microaerophilic protist Giardia intestinalis is the causative agent of giardiasis, one of the most common intestinal infectious diseases worldwide. The pathogen lacks not only respiratory terminal oxidases (being amitochondriate), but also several conventional antioxidant enzymes, including catalase, superoxide dismutase and glutathione peroxidase. In spite of this, since living attached to the mucosa of the proximal small intestine, the parasite should rely on an efficient antioxidant system to survive the oxidative and nitrosative stress conditions found in this tract of the human gut. Here, we review current knowledge on the antioxidant defence systems in G. intestinalis, focusing on the progress made over the last decade in the field. The relevance of this research and future perspectives are discussed.