How Toxoplasma gondii crosses anatomical barriers : a study of tachyzoite and sporozoite invasion
- Anna Poukchanski.
- May 2013.
- Physical description
- online resource (xii, 149 pages) : illustrations (some color)
- Poukchanski, Anna.
- Amieva, Manuel thesis advisor.
- Boothroyd, John C. thesis advisor (primary).
- Nelson, W. J. (W. James) thesis advisor.
- Sonnenburg, Justin, 1973- thesis advisor.
- Stanford University. Department of Microbiology and Immunology.
- Stanford University. Committee on Graduate Studies. degree grantor.
- Includes bibliographical references (p. 134-149). 218 refs.
- Toxoplasma gondii is an obligate intracellular parasite. It has extraordinary abilities to infect virtually any warm blooded animal, cross a number of biological barriers (intestine, placenta and blood-brain), and invade any nucleated cell tested thus far in vitro. Chapter 1 provides a general introduction to Toxoplasma gondii and its ability to invade the host cell. Emphasis is placed on biological barriers and molecular mechanism of invasion for the different forms of the parasite. Chapter 2 describes a study of how Toxoplasma crosses the human placenta. Chapter 3 provides an insight as to how Enteric Glial Cells contribute to oral Toxoplasma infection in vivo. Chapter 4 deals with the study of how Toxoplasma sporozoites invade host cells. All research topics shed light on details of how Toxoplasma crosses the anatomical barriers: from the tissue barriers of placenta to infection to the possible immune and barrier functions of Enteric Glial Cells to how Toxoplasma sporozoites invade host cells. Chapter 2 describes experiments demonstrating that Toxoplasma tachyzoites invade the human placenta. These experiments used the human placental explant system to determine where the tachyzoites first invade, how they travel down the anchoring villi, and whether there exist type differences in ability to invade this tissue. This study provided several insights: (i) Toxoplasma tachyzoites are unable to penetrate the syncytium, and invade only the exposed tissue (anchoring villi); (ii) There does not appear to be a significant difference in the ability of different strains to infect the tissue. Chapter 3 addresses the possible role of TGF-[beta] by Enteric Glial Cells (EGCs) in oral Toxoplasma infection. Mice expressing a Dominant Negative TGF-[beta] receptor in EGCs were orally infected with Toxoplasma tissue cysts. At the end of the time trials, mice were sacrificed and their intestines subjected to histological analysis. Experiments did not reveal a clear-cut contribution to the control of inflammation by this cell type to the progress of disease. Chapter 4 examines the function of two paralogues of AMA1 and RON2 that are present exclusively in Toxoplasma sporozoites. Dubbed sporoAMA1 and sporoRON2, respectively, that sporoRON2 and sporoAMA1 form an exclusive pairing, stabilized with unique structural features. Furthermore, pre-treating sporozoites with a C-terminal portion of sporoRON2 (but not generic RON2) inhibits sporozoite invasion. We see sporoRON2 in a different compartment from RON4, suggesting that sporoRON2 functions independently of known moving junction components. These data indicate that sporozoites' host cell invasion is dependent on a novel, stage-specific version of the AMA1-RON2 pairing.
- Blood-Brain Barrier > immunology
- Intestines > immunology
- Placenta > immunology
- Sporozoites > physiology
- Toxoplasma > pathogenicity
- Toxoplasma > immunology
- Publication date
- Title Variation
- How T. gondii crosses anatomical barriers
- Submitted to the Department of Microbiology and Immunology and the Committee on Graduate Studies of Stanford University.
- Thesis (Ph.D.)--Stanford University, 2013.