An ultrastructural study of the early development and tissue cyst formation of Toxoplasma gondii in the brains of mice

Abstract

The ultrastructural features of the early development and tissue cyst formation of Toxoplasma gondii were examined in the brains of mice at various intervals from 7 days to 22 months post inoculation (PI). At 11 days PI toxoplasmas, with the ultrastructural features of the proliferative (endozoite) form, were identified undergoing multiplication within both inflammatory and neural cells. Early tissue cyst formation was also observed, predominantly within neurons. By 21 days PI the proliferative forms had disappeared and only developing tissue cysts containing densely packed cystozoites were present. The proportion of dividing cystozoites decreased with increasing size and age of the cysts. The wall of the tissue cyst developed as an adaptation of the lining of the parasitophorous vacuole. In the majority of older cysts, numerous tubular structures were present beneath the cyst wall. All the cysts observed were retained within intact host cells. The only morphological change with increasing age was that a proportion of the older cysts contained loosely packed cystozoites in an electron lucent ground substance. There was no evidence of any degenerative changes within the cystozoites.

Hyperplastic cholangitis in a naturallyToxoplasma gondii-infected cat

“…The coccidianlike inclusions herein described were observed in this case at cytological examination of the liver smears; the organisms appeared sometimes as individual ovoid structures, deep blue coloured, consistent with meronts, other as roundish aggregates morphological similar to tachizoytes usually observed in the lungs of T. gondii-infected cats (Gardiner et al 1998). The cytoplasmic inclusions within biliary cells were also evident histologically, and were ultrastructurally identical to those previously described for T. gondii (Ferguson & Hutchison 1987). As these structures were difficult to distinguish morphologically from the other coccidian parasites, definitive diagnosis of toxoplasmosis was achieved through molecular assays.…”

Toxoplasma gondii:Étude ultrastructurale des formations kystiques observées en culture de fibroblastes humains

“…Ces formations kystiques sont similaires aux kystes cérébraux de souris. Leur description rejoint celle des études ultrastructurales portant sur les kystes tissulaires (Mehlborn et Frenkel, 1980 ;Ferguson et Hutchison, 1987) : formation intracellulaire limitée par une membrane aux invaginations plus ou moins nombreuses et profondes selon l'ancienneté du kyste, soulignée sur sa face interne par une accumulation de substance granuleuse. Un matériel granulaire plus dispersé occupe l'espace entre les toxoplasmes.…”

“…Or, l'aspect ultrastructural de ces kystes observés en culture cellulaire s'oppose sur de nombreux points aux vacuoles parasitophores contenant des amas de tachyzoïtes observés dans les cellules sarcomateuses TG d'ascite de souris infectée et, en culture cellulaire, dans une forte proportion de fibroblastes infectés. Les caractères ultrastructuraux de ces vacuoles contenant des colonies de tachyzoïtes sont en accord avec ceux décrits par d'autres auteurs (Nichols et O'Connor, 1980;Ferguson et Hutchison, 1987) : vacuole parasitophore limitée par une membrane mince, marquée par de longues invaginations tubulaires, contenant des formations membranaires dispersées entre les tachyzoïtes.…”

“…Les résultats de notre étude ultrastructurale des kystes cérébraux observés chez la souris sont en accord avec ceux déjà décrits par d'autres auteurs pour ces formations (Ferguson et Hutchison, 1987). Le kyste cérébral est intracellu laire ( fig.…”

Toxoplasma gondii: 1908-2008, homage to Nicolle, Manceaux and Splendore

“…It has been possible using immuno-histology and stage specific antibodies to follow the distribution of the parasite during the development of the acute phase in orally infected mice and identify the changes associated with conversion from the acute to the chronic phase (Ferguson & Hutchison 1987b, Dubey 1997a, Dubey et al 1997. Recently, it has been possible to track parasites in live mice by using Fire-fly luciferase expressing parasites (Saeij et al 2005, Boyle et al 2007).…”