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.

Nanoemulsion of atovaquone as a promising approach for treatment of acute and chronic toxoplasmosis.

Treatment of toxoplasmosis is necessary in congenital form and immunocompromised patients. Atovaquone is a powerful suppressor of protozoan parasites with a broad-spectrum activity, but an extremely low water solubility and bioavailability. In this study, nanoemulsion of this drug was prepared with grape seed oil using spontaneous emulsification method to increase bioavailability and efficacy of atovaquone for treatment of toxoplasmosis. In vitro activity of atovaquone nanoemulsion against T. gondii, RH and Tehran strains, was assessed in HeLa cell culture. For in vivo assessment, BALB/c mice were infected with RH and Tehran strains and then treated with nanoemulsion of atovaquone, compared to that treated with free atovaquone. Concentration of atovaquone nanoemulsion showed in vitro anti-parasitic effects in both strains of T. gondii. Furthermore, oral administration of atovaquone nanoemulsion increased oral bioavailability, tissue distribution and mice survival time and reduced parasitemia and number and size of the brain cysts. Decrease of cyst numbers was verified by down regulation of BAG1 using real-time polymerase chain reaction (real-time PCR) assay. Effective therapeutic activity of atovaquone at a reduced dose is the major achievement of this study.

[Effects of atovaquone and astragalus combination on the treatment and IL-2, IL-12, IFN-γ levels on mouse models of acute toxoplasmosis]. / Atovakuon ve astragalus kombinasyonunun akut toksoplazmozlu fare modeli tedavisi ve IL-2, IL-12, IFN-γ düzeyleri üzerindeki etkileri.

Reactivation of Toxoplasma gondii infections and serious clinical manifestations such as encephalitis may develop in immunocompromised subjects and AIDS patients. Different protocols are used for the treatment of toxoplasmosis in high-risk patient groups, however life-long prophylactic therapy against reactivation risk in AIDS patients may lead to several undesired results. Atovaquone is an effective antiprotozoal agent against toxoplasmosis with minor side effects. On the other hand, Astragalus membranaceus root extract (AmE) has been shown to have immunomodulatory and antimicrobial activities, empowering immunity by enhancing proliferation and activation of phagocytic cells mainly macrophages, and inducing Th1 type immune response. The aim of this study was to investigate the effectiveness of atovaquone alone and in combination with AmE, in the treatment of toxoplasmosis, and on the levels of IL-2, IL-12 and IFN-γ in experimentally infected mice with T.gondii. For this purpose, four experimental groups, each consisting of eight BALB/c mice, were set with the approval of Ethics Committee for the Animal Experiments. All the mice were infected with 0.5 ml of a suspension containing 2 x 104/ml trophozoites prepared from T.gondii RH strain by intraperitoneal injection. Twenty-four hours after the infection, atovaquone (100 mg/kg/day) was given to atovaquone group, AmE (0.075 mg/g) to astragalus group and atovaquone (100 mg/kg/day) plus AmE (0.075 mg/g) to Atovaquone + Astragalus (Ato + Astra) group by oral gavage. The mice in the fourth group, which was the control group, were all infected but untreated. The above administrations were carried out for seven days. On the 8th day peritoneal fluids of mice were collected under anaesthesia and trophozoite numbers per 1 ml were detected by counting on the Thoma slide. In addition, the heart bloods of mice were drawn and IL-2, IL-12, IFN-γ levels were determined in serum samples by using commercial ELISA kits (eBioscience, Austria). The mean number of trophozoites in Ato + Astra group was found significantly lower than the number of trophozoites in the other three groups (p< 0.05). The number of trophozoites in the atovaquone and astragalus groups were found significantly lower than the number of trophozoites in the control group (p< 0.05). There was a significant increase in IL-2 levels of astragalus group compared with the other three groups, in addition when IL-2 levels of Ato + Astra group were compared with ones in other three groups, a significant decrease was noticed (p< 0.05). There was a definite increase in IL-12 levels of atovaquone, astragalus and the control groups compared to those in Ato + Astra group (p< 0.05). A significant increase was found in IFN-γ levels in atovaquone and Ato + Astra groups compared with those in the control group (p< 0.05). Within the reach of our literature survey, this study was the first research in which the effectiveness of the combination of atovaquone and AmE was investigated in the treatment of acute toxoplasmosis. The results of our study suggested that there might be a synergy between atovaquone and AmE in the treatment of acute toxoplasmosis. In case these results are supported by further studies, atovaquone and AmE combination may have a potential to be used for therapy in immunocompromized patients such as AIDS patients who have a risk for toxoplasmosis.

Cerebral malaria in spite of peripheral parasite clearance in a patient treated with atovaquone/proguanil.

Cerebral malaria, the most frequent complication of falciparum malaria, is usually predicted by an increased count of asexual parasites in peripheral blood. We report a case of a female returnee from Ghana who developed cerebral malaria in spite of parasite clearance in peripheral blood after therapy with atovaquone/proguanil.

Pharmacokinetics of dihydroartemisinin following oral artesunate treatment of pregnant women with acute uncomplicated falciparum malaria.

OBJECTIVE: To determine the pharmacokinetic properties of dihydroartemisinin (DHA) following oral artesunate treatment in women with recrudescent multi-drug resistant falciparum malaria, in the second and third trimesters of pregnancy. METHODS: Serial plasma concentrations of artesunate and DHA were measured in 24 women after the final dose of a 3 day treatment with artesunate (4 mg kg(-1) day(-1)) and atovaquone (20 mg kg(-1) day(-1)) plus proguanil (8 mg kg(-1) day(-1)), daily. Conventional non-compartmental modelling and a population one-compartment pharmacokinetic model were applied to the data. RESULTS: Artesunate was very rapidly eliminated. For DHA the median [90% range] estimate of oral clearance (CI/F) was 4.0 [0.8-20.7] l hour(-1) kg(-1), total apparent volume of distribution (Vd/f) was 3.4 [0.9-60.7] l/kg, and terminal elimination half-life was 1.0 [0.6-2.4] h. CONCLUSION: The kinetics of DHA are modified by pregnancy. The plasma levels of the active antimalarial metabolite DHA are lower than reported previously in non-pregnant adults. Dose-optimisation studies in pregnant women are needed.