Toxoplasma gondii: Protection against colonization of the brain and muscles in a rat model

Adjunctive bradyzoite-directed therapy for reducing complications of congenital toxoplasmosis

Congenital toxoplasmosis is caused by in utero infection of the fetus with the intracellular parasite Toxoplasma gondii. Upon infection, the parasite forms life-long cysts in fetal brain and eyes which are resistant to the currently accepted therapy of pyrimethamine and sulfadiazine. These cysts commonly reactivate later in life causing chorioretinitis and visual impairment, and rarely cause neurological complications. I hypothesize that adjunctive, bradyzoite-directed therapies have the potential to alleviate a significant burden of disease by reducing cyst burden in neonatal brain and eyes. Atovaquone is perhaps the most promising drug for further evaluation given its low side-effect profile, established safety, and efficacy in animal models reducing cyst burden. Very limited observational data in humans suggests atovaquone may prevent Toxoplasma-associated chorioretinitis recurrence. Clinical trials are needed to evaluate it and other potential drugs as adjunctive treatment in congenital toxoplasmosis.

Immunization of Wistar female rats with 255-Gy-irradiated Toxoplasma gondii: preventing parasite load and maternofoetal transmission

Toxoplasmosis, caused by an obligate intracellular protozoan parasite, Toxoplasma gondii, is an worldwide parasitic disease, with significant importance for animal production and considerable impact to the public health. This study was aimed to evaluate the dynamic of the distribution of T.gondii in tissues of female Wistar rats and their puppies tissues, after the immunization by oral rote with irradiated tachyzoites. One week after pregnancy confirmation, rats was challenged by gavage with T. gondii bradyzoites, oocysts or tachyzoites of T. gondii. Forty-eight pregnant rats were grouped as follow: immunized and challenged with bradyzoites (BZ*); non-immunized and challenged with bradyzoites (BZ); immunized and challenged with oocysts (OC*); non-immunized and challenged with oocysts (OC); immunized and challenged with tachyzoites (TZ*); non-immunized and challenged with tachyzoites (TZ); only immunized (I); control group (C). After parturition the rats were sacrificed and the tissues were researched for the DNA of T. gondii by polymerase chain reaction (PCR) and the parasite load determined by the quantitative PCR (qPCR). It was verified that the immunization with irradiated tachyzoites of T. gondii induced the reduction of parasitic load in most organs analyzed, although not prevent the establishment of infection with the parasite. And also, the immunization showed a favorable effect on the birth rate and litter size.

Lower expression of inducible nitric oxide synthase and higher expression of arginase in rat alveolar macrophages are linked to their susceptibility to Toxoplasma gondii infection

Rats are naturally resistant to Toxoplasma gondii infection, particularly the RH strain, while mice are not. Previous studies have demonstrated that inducible nitric oxide synthase (iNOS) and arginase-1 of rodent peritoneal macrophages are linked to the mechanism of resistance. As an increasing number of studies on human and animal infections are showing that pulmonary toxoplasmosis is one of the most severe clinical signs from T. gondii infection, we are interested to know whether T. gondii infection in alveolar macrophages of rats is also linked to the levels of iNOS and arginase-1 activity. Our results demonstrate that T. gondii could grow and proliferate in rat alveolar macrophages, both in vitro and in vivo, at levels higher than resistant rat peritoneal macrophages and at comparable levels to sensitive mouse peritoneal macrophages. Lower activity and expression levels of iNOS and higher activity and expression levels of arginase-1 in rat alveolar macrophages were found to be linked to the susceptibility of T. gondii infection in these cells. These novel findings could aid a better understanding of the pathogenesis of clinical pulmonary toxoplasmosis in humans and domestic animals.