Pyrimidine salvage in Toxoplasma gondii as a target for new treatment.

Toxoplasmosis is a common protozoan infection that can have severe outcomes in the immunocompromised and during pregnancy, but treatment options are limited. Recently, nucleotide metabolism has received much attention as a target for new antiprotozoal agents and here we focus on pyrimidine salvage by Toxoplasma gondii as a drug target. Whereas uptake of [3H]-cytidine and particularly [3H]-thymidine was at most marginal, [3H]-uracil and [3H]-uridine were readily taken up. Kinetic analysis of uridine uptake was consistent with a single transporter with a Km of 3.3 ± 0.8 µM, which was inhibited by uracil with high affinity (Ki = 1.15 ± 0.07 µM) but not by thymidine or 5-methyluridine, showing that the 5-Me group is incompatible with uptake by T. gondii. Conversely, [3H]-uracil transport displayed a Km of 2.05 ± 0.40 µM, not significantly different from the uracil Ki on uridine transport, and was inhibited by uridine with a Ki of 2.44 ± 0.59 µM, also not significantly different from the experimental uridine Km. The reciprocal, complete inhibition, displaying Hill slopes of approximately -1, strongly suggest that uridine and uracil share a single transporter with similarly high affinity for both, and we designate it uridine/uracil transporter 1 (TgUUT1). While TgUUT1 excludes 5-methyl substitutions, the smaller 5F substitution was tolerated, as 5F-uracil inhibited uptake of [3H]-uracil with a Ki of 6.80 ± 2.12 µM (P > 0.05 compared to uracil Km). Indeed, we found that 5F-Uridine, 5F-uracil and 5F,2'-deoxyuridine were all potent antimetabolites against T. gondii with EC50 values well below that of the current first line treatment, sulfadiazine. In vivo evaluation also showed that 5F-uracil and 5F,2'-deoxyuridine were similarly effective as sulfadiazine against acute toxoplasmosis. Our preliminary conclusion is that TgUUT1 mediates potential new anti-toxoplasmosis drugs with activity superior to the current treatment.

Seroprevalence of Toxoplasma gondii infection among HIV-positive patients in Southwest Iran and associated risk factors: a case-control study.

BACKGROUND: The current study aimed to determine the seroprevalence of Toxoplasma gondii infection among HIV-positive patients and healthy subjects. METHODS: This study was carried out on HIV-positive patients and healthy individuals in Southwest Iran. Five millilitres of venous blood samples were collected aseptically from each individual. Sera and buffy coats were isolated from each sample and evaluated for anti-Toxoplasma antibodies and T. gondii DNA using ELISA kit and real-time PCR, respectively. Statistical analysis was performed using SPSS 18 software. RESULTS: Of 64 AIDS/HIV-positive patients, six (9.3%, 95% CI 7.2 to 11.3%) were seropositive for only IgG and five (7.8%, 95% CI 6.0 to 9.5%) were seropositive for both IgG and IgM. Moreover, among 64 healthy controls, 10 (15.6%, 95% CI 12.1 to 19.0%) were seropositive for only IgG and 2 (3.1%, 95% CI 2.4 to 3.7%) were seropositive for both IgG and IgM. Toxoplasma gondii DNA was detected in six samples (9.3%, 95% CI 7.2 to 11.3%) in the AIDS/HIV-positive patients group and eight samples (5.95%, 95% CI 4.6 to 7.2%) in the control group using real-time PCR. Consumption of undercooked meat was documented as an associated risk factor for T. gondii seropositivity in AIDS patients (OR 4.06, 95% CI 0.966 to 17.09; p=0.045). CONCLUSIONS: Our findings showed a lower prevalence of Toxoplasma infection in AIDS/HIV-positive patients vs healthy controls; however, a considerable number of AIDS/HIV-positive patients were also seen to be at risk of toxoplasmosis. Based on the findings, screening and prophylaxis for toxoplasmosis should be implemented for all AIDS/HIV-positive patients in Southwest Iran.

Occurrence of IGG antibodies anti-TOXOPLASMA GONDII and NEOSPORA CANINUM in cattle raised in family agricultural properties in Realeza, Parana, Brazil

This cross-sectional study evaluates the presence of antibodies against Neospora caninum and Toxoplasma gondii in cattle raised in Realeza, PR. There was a seroprevalence of N. caninum and T. gondii of 87.5% and 67.9%, respectively in the properties assessed. The frequencies of T. gondii and N. caninum in the animals were 41.1% and 55.1%, respectively. The studied coccidia are widely distributed in dairy cows reared on family farms in the municipality of Realeza, PR. Sanitary control for reproductive diseases must be adopted to prevent miscarriages and the economic damage caused by the disease. Future studies should be performed to investigate how widespread these pathogens are in cattle herds in southwestern Parana.

Taenia crassiceps antigens induce a Th2 immune response and attenuate injuries experimentally induced by neurotoxoplasmosis in BALB/c mice.

Toxoplasma gondii is a pathogenic agent responsible for causing both systemic and local disease which elicits a typically pro-inflammatory, Th1 immune response. Taenia crassiceps antigen induces a Th2 immune response that immunomodulates Th1 based infections. Therefore the aim of this study was to evaluate whether T. crassiceps cysticerci antigens are able to modulate the inflammatory response triggered in experimental neurotoxoplasmosis (NT). BALB/c mice were inoculated with T. gondii cysts and/or cysticerci antigens and euthanized at 60 and 90days after inoculation (DAI). The histopathology of the brains and cytokines produced by spleen cells culture were performed. The animals from the NT group, 90DAI (NT90), presented greater intensity of lesions such as vasculitis, meningitis and microgliosis and cytokines from Th1 profile characterized by high levels of IFN-gamma. While in the T. crassiceps antigens group, 60DAI, there were more discrete lesions and high levels of IL-4, a Th2 cytokine. In the NT co-inoculated with cysticerci antigens group the parenchyma lesions were more discrete with lower levels of IFN-gamma and higher levels of IL-4 when compared to NT90. Therefore the inoculation of T. crassiceps antigens attenuated the brain lesions caused by T. gondii inducing a Th2 immune response.

Molecular Cloning, Expression and Characterization of Plasmid Encoding Rhomboid 4 (ROM4) of Tachyzoite of Toxoplasma gondii RH Strain.

BACKGROUND: The objective of this study was to clone, express and characterize the gene encoding rhomboid 4 (ROM4) proteins, a vital gene in surface adhesion and host cell invasion process of tachyzoite of T. gondii in an appropriate expression vector and eukaryotic cell for production of recombinant protein. METHODS: Toxoplasma RNA was isolated from tachyzoites (RH strain) and complementary DNA was synthesized. Oligonucleotide primer pair was designed based on Toxoplasma ROM4 gene sequence with XhoI and EcoRI restriction sites at 5' end of forward and reverse primers, respectively. ROM4 gene was amplified by PCR, cloned into pTG19-T vector and the recombinant plasmid was sequenced. The gene was subcloned into pcDNA3 plasmid and expressed in CHO cells as eukaryotic cell. SDS-PAGE and western blotting were performed for protein determination and verification. RESULTS: Cloning of ROM4 gene in pTG19-T vector was confirmed by colony-PCR and enzymatic digestion. The results of enzymatic digestion and gene sequencing confirmed successful cloning and subcloning procedures. The nucleotide sequence of the cloned ROM4 gene showed 99% homology compared to the corresponding sequences of original gene. SDS-PAGE and western blotting analyses of the purified protein revealed a single band having expected size of 65 kDa. CONCLUSION: This eukaryotic expression system is an appropriate system for high-level recombinant protein production of ROM4 gene from T. gondii tachyzoites used as antigenic component for serological assay and vaccine development.

Toxoplasmose gástrica em paciente infectado pelo vírus da imunodeficiência humana. Relato de caso / Gastric toxoplasmosis in patient infected with human immunodeficiency virus. Case report

A toxoplasmose é uma zoonose altamente disseminada. A maio­ria das infecções em imunocompetentes é assintomática. Porém, em pacientes imunodeprimidos, a infecção adquire um curso variável. Em pacientes com contagem de CD4 abaixo de 100 e que foram previamente expostos ao Toxoplasma gondii, pode haver reativação da doença em diversos tecidos. Envolvimento do trato gastrintestinal por Toxoplasma gondii é raramente relatado. Embora os sintomas gastrintestinais sejam comuns entre os pacientes com síndrome da imunodeficiência adquirida, a maioria é causada por infecções entéricas que não o Toxoplasma gondii. O objetivo deste estudo foi relatar um caso raro de toxoplasmose gástrica. Paciente do gênero feminino, 38 anos, com diagnóstico recente de vírus da imunodeficiência humana, iniciou sintomas gástricos inespecíficos como: epigastralgia, náuseas, vômitos e perda ponderal. O diagnóstico definitivo foi fechado com o estudo anatomopatológico da lesão na mucosa gástrica. Foi instituído tratamento para a toxoplasmose com clindamicina, pirimetamina e ácido folínico (devido à mielotoxicidade), com melhora parcial dos sintomas. Embora raro, a toxoplasmose gástrica deve entrar no diagnóstico diferencial de dor epigástrica em pacientes portadores da síndrome da imunodeficiência adquirida com contagem de CD4 baixa. Seu diagnóstico pre­suntivo pode ser dado pelo quadro clínico, mas o diagnóstico definitivo é obtido pela biópsia da lesão...

Toxoplasmosis is a highly disseminated zoonosis. Most infections are asymptomatic in immunocompetent patients. However, in immunocompromised patients, infection acquires a variable course. In patients with CD4 counts lower than 100 and who have been previously exposed to Toxoplasma gondii, there may be reactivation of the disease in various tissues. Involvement of the gastrointestinal tract by Toxoplasma gondii is rarely reported. Although gastrointestinal symptoms are common among patients with acquired immunodeficiency syndrome, most are caused by enteric infections other than Toxoplasma gondii. The aim of this study was to report a rare case of gastric toxoplasmosis. A 38-year-­old female patient, recently diagnosed with immunodeficiency human virus, presented with nonspecific gastric symptoms such as epigastric pain, nausea, vomiting and weight loss. The definitive diagnosis was reached with anatomopathological examination of gastric mucosa damage. She was treated for toxoplasmosis with clindamycin, pyrimethamine and folinic acid (due to myelotoxicity), with partial improvement of symptoms. Although rare, gastric toxoplasmosis should enter the differential diagnosis of epigastric pain in patients with acquired immunodeficiency syndrome with low CD4 count. Its presumptive diagnosis can be made on a clinical basis, but the definitive diagnosis is reached with biopsy...

Interaction and cystogenesis of Toxoplasma gondii within skeletal muscle cells in vitro

Infection by the protozoan parasite Toxoplasma gondii is widely prevalent in humans and animals. To prevent human infection, all meat should be well cooked before consumption, since the parasite is present in skeletal muscle. In this context, the use of skeletal muscle cells (SkMCs) as a cellular model opens up new approaches to investigate T. gondii-host cell interactions. Immunofluorescent detection of proteins that are stage-specific for bradyzoites indicated that complete cystogenesis of T. gondii in in vitro cultures of SkMCs occurs after 96 h of infection. Ultrastructural analysis showed that, after 48 h of interaction, there were alterations on the parasitophorous vacuole membrane, including greater thickness and increased electron density at the inner face of the membrane. The present study demonstrates the potential use of primary cultures of SkMCs to evaluate different molecular aspects of T. gondii invasion and cystogenesis and presents a promising in vitro model for the screening of drug activities toward tissue cysts and bradyzoites.