Toxoplasma encephalitis of immunocompetent and nude mice: immunohistochemical characterisation of Toxoplasma antigen, infiltrates and major histocompatibility complex gene products

The Induction and Kinetics of Antigen-Specific CD8 T Cells Are Defined by the Stage Specificity and Compartmentalization of the Antigen in Murine Toxoplasmosis

“…After oral infection, bradyzoites switch to tachyzoites within 12-18 h (1), and this rapid stage conversion may result in the production of too low amounts of Ag, which is insufficient for the induction of a bradyzoite-specific CD8 T cell response. Thereafter, predominantly tachyzoites, but not bradyzoites, multiply in the gastrointestinal tract, disseminate in the host, and infect multiple parenchymatous and lymphatic organs (1,2). The conversion of some tachyzoites into bradyzoites, which eventually form intracellular tissue cysts in parenchymatous but not in lymphatic organs, is not initiated before day 6 p.i.…”

“…Humans and rodents develop toxoplasmosis following oral uptake of T. gondii cysts, which release bradyzoites-the slowly replicating form of the parasite-in the gastrointestinal tract. These bradyzoites transform into rapidly multiplying tachyzoites that may infect several organs including lung, heart, spleen, and brain (1,2). Immunocompetent hosts eradicate the parasite from most organs by the ensuing immune response, but not from the brain where the parasites convert into bradyzoites and may indefinitely persist within intracellular cysts (2).…”

Dynamic Imaging of T Cell-Parasite Interactions in the Brains of Mice Chronically Infected withToxoplasma gondii

“…During the initial acute phase of the infection, rapidly dividing tachyzoites hijack host cellular machinery to spread throughout the body but are eventually brought under control by a strong adaptive immune response (10 -13). Some parasites convert into slow-growing bradyzoites, which form cysts in brain and muscle that persist for the lifetime of the host and apparently effectively evade destruction by the immune system (14,15). T. gondii infections in humans are generally asymptomatic, although reactivation of intracerebral cysts can lead to toxoplasmic encephalitis in immunocompromised hosts (16).…”

CD40, autophagy and Toxoplasma gondii

“…Macrophages and T cells infiltrate the brain and the retina in cerebral and ocular toxoplasmosis (Schluter et al 1991, Gazzinelli et al 1994. Therefore, CD154 + T. gondii-reactive activated CD4 + T cells likely trigger CD40 signaling in macrophages and resident microglia.…”