BACKGROUND Toxoplasma gondii is an obligate intracellular parasite that infects humans at high prevalence rates. The virulent RH strain of T. gondii is generally considered to have lost its cyst forming capacity. This study performed to obtain tissue cysts in mice infected with tachyzoites of RH strain treated with sulfadiazine (SDZ). It provides the opportunity to analyze the conversion of tac...

The conservation of Toxoplasma gondii strains isolated from humans and animals is essential for conducting studies on Toxoplasma. Conservation is the main function of the French Biological Toxoplasma Resource Centre (BRC Toxoplasma, France, http://www.toxocrb.com/). In this study, we have determined the suitability of a standard cryopreservation methodology for different Toxoplasma strains usin...

DNA methylation is a key epigenetic modification which confers phenotypic plasticity and adaptation. Cyst-forming strains of Toxoplasma gondii undergo tachyzoite to bradyzoite conversion after initial acute infection of a host, and the reverse conversion may occur in immune-suppressed hosts. The formation of m5C is catalyzed by DNA methyltransferase (DNMT). We identified two functional DNA meth...

Toxoplasma gondii is a protozoan parasite of mammals and birds that is an important human pathogen. Infection with this Apicomplexan parasite results in its dissemination throughout its host via the tachyzoite life-stage. After dissemination these tachyzoites differentiate into bradyzoites within cysts that remain latent. These bradyzoites can transform back into tachyzoites and in immunosupres...

BACKGROUND This study was performed to induce conversion of RH strain tachyzoites of Toxoplasma gondii to bradyzoites by pH changing of the culture medium. METHODS HeLa cell monolayers were infected at a 1:1 tachyzoite to cell ratio. Four hours after infection, the culture medium was removed and replaced with culture medium and 5% FCS, adjusted to pH 8 with NaOH. The culture was maintained at...

Besnoitia darlingi from naturally infected opossums (Didelphis virginiana) from Mississippi, USA, was propagated experimentally in mice, cats, and cell culture and was characterised according to ultrastructural, genetic, and life-history characteristics. Cats fed tissue cysts from opossums shed oocysts with a prepatent period of nine or 11 days. Oocysts, bradyzoites, or tachyzoites were infecti...

Mast cells participate in the host defense against parasites. Mast cells release leukotrienes (LTs), potent 5-lipoxygenase (LO) products of arachidonic acid well-known to be involved in the inflammatory process. After incubation with Toxoplasma gondii, mast cells were found to degranulate and release LTB4; this interaction damages the tachyzoites. This mast cell activity against the tachyzoites...

Protozoal dermatitis was diagnosed in a 6-year-old female Great Dane dog from Rio de Janeiro, Brazil. The dog died because of a chronic illness with an Ehrlichia-like organism. Numerous apicomplexan parasites were identified histologically in the section of dermal lesions. The protozoan reacted with Toxoplasma gondii polyclonal rabbit serum but not with Neospora caninum or Sarcocystis neurona a...

Attachment and invasion of Toxoplasma gondii and Neospora caninum to a cat and a dog fibroblast cell line and 2 epithelial cell lines (a cat kidney and Vero) were compared in vitro using fluorescence antibody methodology. In addition, trypsin treatment of tachyzoites was used to determine whether protein molecules were essential to the process of invasion. The results show that both T. gondii a...