The host-parasite relationship ofToxoplasma gondii in the brains of chronically infected mice

Abstract

The host parasite relationship in the brains of asymptomatic mice chronically infected with Toxoplasma gondii was examined at 3, 6 and 12 months post-infection (PI) using electron microscopy. The parasites were located in large numbers within tissue cysts which ranged in size from 10-50 microns in diameter. The cysts were predominantly found in the grey matter. The toxoplasms were enclosed by a cyst wall consisting of a membrane, with irregular invaginations, and an underlying layer of homogeneous osmiophilic material. A detailed examination of 50 cysts revealed that all the cysts were present within intact host cells irrespective of their size or the period PI. The majority of host cells could be positively identified as neurons by the presence of synapses. No extracellular cysts were observed. It is probable that the intracellular location of the cysts protects them from recognition and attack by the host immune system.

Astrocyte gp130 Expression Is Critical for the Control of Toxoplasma Encephalitis

“…Neurons are a major target cell of T. gondii tachyzoites in the CNS. In addition, cysts are exclusively detectable in neurons (40). Thus, especially the increased number of cysts in GFAP-Cre gp130 fl/fl mice indirectly suggests that the control of T. gondii is impaired in neurons.…”

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

“…This assumption is experimentally supported by the crucial protective role of CD8 T cells in the TE of retrovirus-infected immunocompromised mice (35,36). The failure of CD8 T cells to completely eliminate T. gondii from the brain may be caused by an immune evasion of tachyzoites in which CD8 T cells switch into bradyzoites, which do not induce a primary ␤-gal-specific CD8 T cell response, as well as the formation of cysts in neurons (37,38), which in general lack expression of MHC class I and II Ag (39).…”

Toxoplasmosis and Congenital Sensorineural Hearing Loss in Saudi Arabia

“…This could explain the long-term period of its latent infection. 4 The disease has attracted the attention of otolaryngologists, since the parasite has been recognized to be transmitted transplacentally and could result in selective infection of the fetal CNS, causing multiple or isolated neurological damage ranging from blindness, hydrocephalus, microcephaly, psychomotor and mental retardation, epilepsy and deafness. 3 There are numerous studies on the prevalence of the disease in different regions of the world.…”