Toxoplasma gondii: determinants of tachyzoite to bradyzoite conversion

• Published in: Parasitology research (1987) Vol. 107; no. 2; pp. 253 - 260
• Main Authors: Skariah, Sini, McIntyre, Matthew Karmen, Mordue, Dana G
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.07.2010; Springer-Verlag; Springer
• Subjects: Animals; Apicomplexa; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; bradyzoites; cytology; death; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation; General aspects; General aspects and techniques. Study of several systematic groups. Models; growth & development; host range; Humans; immunity; Immunology; Invertebrates; Medical Microbiology; Microbiology; parasites; pathogenesis; pathogenicity; Review; sporozoites; tachyzoites; Toxoplasma; Toxoplasma - cytology; Toxoplasma - growth & development; Toxoplasma - immunology; Toxoplasma - pathogenicity; Toxoplasma gondii; toxoplasmosis; vertebrates; Human Foreskin Fibroblast; Exogenous Stress; Parasite Replication; Tissue Cyst; Stage Conversion; Parasite; Protozoa; Apicomplexa; Toxoplasma gondii; Conversion
• ISSN: 0932-0113; 1432-1955; 1432-1955
• DOI: 10.1007/s00436-010-1899-6

Apicomplexa are primarily obligate intracellular protozoa that have evolved complex developmental stages important for pathogenesis and transmission. Toxoplasma gondii, responsible for the disease toxoplasmosis, has the broadest host range of the Apicomplexa as it infects virtually any warm-blooded vertebrate host. Key to T. gondii's pathogenesis is its ability to differentiate from a rapidly replicating tachyzoite stage during acute infection to a relatively non-immunogenic, dormant bradyzoite stage contained in tissue cysts. These bradyzoite cysts can reconvert back to tachyzoites years later causing serious pathology and death if a person becomes immune-compromised. Like the sexual stage sporozoites, bradyzoites are also orally infectious and a major contributor to transmission. Because of the critical role of stage conversion to pathogenesis and transmission, a major research focus is aimed at identifying molecular mediators and pathways that regulate differentiation. Tachyzoite to bradyzoite development can occur spontaneously in vitro and be induced in response to exogenous stress including but not limited to host immunity. The purpose of this review is to explore the potential contributors to stage differentiation in infection and how a determination is made by the parasite to differentiate from tachyzoites to bradyzoites.