title: Dissemination of extracellular and intracellular Toxoplasma gondii tachyzoites in the blood flow.
abstract: Toxoplasma gondii is an intracellular parasite. It has been thought that T. gondii can disseminate throughout the body by circulation of tachyzoite-infected leukocytes (intracellular parasite) in the blood flow. However, a small number of parasites exist as free extracellular tachyzoites in the blood flow (extracellular parasite). It is still controversial whether the extracellular parasites in the blood flow disseminate into the peripheral tissues. In this study, we evaluated the dissemination efficiency of the extracellular and intracellular parasites in the blood flow using GFP-expressing transgenic parasite (PLK/GFP) and DsRed Express-expressing transgenic parasite (PLK/RED). When PLK/GFP and PLK/RED tachyzoites were injected, as intracellular and extracellular forms respectively, at the same time into the tail vein of a mouse, many disseminated green fluorescent PLK/GFP tachyzoites were observed in the lung, the spleen, the liver and the brain. However, only a few red fluorescent PLK/RED tachyzoites were detected in these organs. When PLK/GFP and PLK/RED tachyzoites were injected in the opposite manner, that is, as extracellular and intracellular forms respectively, the majority of tachyzoites in these tissues were PLK/RED tachyzoites. Collectively, these results indicate that intracellular tachyzoites mainly disseminate throughout the body and that extracellular tachyzoites hardly contribute to parasite dissemination.
authors.affiliation: Department of Veterinary Parasitological Diseases, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Unno
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Suzuki
authors.forename: Xuenan
authors.initials: X
authors.lastname: Xuan
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Nishikawa
authors.forename: Katsuya
authors.initials: K
authors.lastname: Kitoh
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takashima
mesh_terms: D000818:Animals; D001775:Blood Circulation; D002522:Chlorocebus aethiops; D005110:Extracellular Space / Q000469:parasitology*; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006790:Host-Parasite Interactions; D007962:Leukocytes / Q000469:parasitology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D014122:Toxoplasma / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology*; D014124:Toxoplasmosis, Animal / Q000469:parasitology / Q000503:physiopathology*; D014709:Vero Cells
chemical_list: D008164:Luminescent Proteins; C413663:fluorescent protein 583; D049452:Green Fluorescent Proteins