ABSTRACT
Toxoplasma gondii is an opportunistic intracellular parasite that, in the tachizoite stage in the life cycle, is capable of infecting a wide range of nucleated cells of vertebrate hosts. In an effort to characterize the adaptations of tachizoites that facilitate intracellular survival, this chapter examines the unique modifications of host cell phagosomes that occur following infection with T. gondii. Toxoplasma enters the host cell by invagination of the plasma membrane in a process that resembles phagocytosis yet also involves active orientation and motility by the parasite. T. gondii contains electron-dense vacuoles, distinctly separate from the rhoptries, that appear to fuse with the cell membrane and discharge their contents into the newly formed phagosome. The distribution of Toxoplasma surface antigens in the intravacuolar networks is readily demonstrated by surface colloidal gold labeling using both polyclonal antisera and monoclonal antibodies to T. gondii.
