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The aim of this study was to verify the effect of immunosuppression by cyclophosphamide (Cy) on susceptibility of BALB/c mice subjected to challenge with recombinant strains of Toxoplasma gondii. Animals were prime infected with the D8 (recombinant I/III) or the ME49 (type II) non-virulent strains, weekly immunosuppressed with Cy and challenged with the CH3 or EGS virulent strains (I/III). Parasites recovered from surviving mice were submitted to PCR-RFLP analysis to confirm co-infection. Prime-infection with the D8 strain conferred more protection against challenge with the CH3 and EGS strains when compared with ME49 prime infection. Cy treatment caused significant leukopenia in the infected mice, what probably favors reinfection after challenge. Reinfection was associated with increased levels of IgA. Otherwise, Cy-treated mice presented significantly lower IgA levels after challenge, suggesting involvement of this immunoglobulin on protection against reinfection. In conclusion, BALB/c mice susceptibility to reinfection by T. gondii is related to genetic differences among the strains used for primary and challenge infections. Alteration of the host’s immune integrity by Cy probably compromises the protection previously established by primary infection.

In an attempt to isolate and characterize Toxoplasma gondii from the State of Minas Gerais, Brazil, musculature samples from 72 pigs, 25 dogs, 28 free-range chickens and 50 chickens produced in industrialized farms were collected. Antibodies to T. gondii have not been detected in pigs, but were found in nine (40.9 %) out of 22 dogs, and in 15 (53.6 %) of 28 free range chickens. T. gondii was not isolated from pigs and industrialized chickens, but from eight dogs and 11 free range chickens. In order to determine T. gondii virulence, female BALB/c mice were inoculated with 103, 102, 101 and 100 tachyzoites of the 19 isolates. The strains RH (virulent) and ME49 (non-virulent) were used as references. Isolates were divided into three groups according to the virulence phenotype: five isolates were classified into virulent in mice, one into non-virulent and 13 into intermediate virulent. Nested-PCR of T. gondii SAG2 locus amplified DNA from 21 out of 22 DNA samples directly extracted from heart of free range chickens. These samples were genotyped through a PCR-RFLP assay. Seventeen (80.9 %) were classified into type I; one (4.8 %) into type III and three (14.3 %) into type I or II.

The efficacy of atovaquone and sulfadiazine was examined alone or in combination for the treatment of mice infected with six Brazilian Toxoplasma gondii strains previously genotyped using the PCR-RFLP assays of the SAG2 gene, in addition to RH strain. Swiss mice were infected intraperitoneally with 102 tachyzoites from each strain of T. gondii and treated with 6.25, 12.5, 25 and 50 mg/Kg/day of atovaquone or 40, 80, 160 and 320 mg/Kg/day of sulfadiazine. In a second experiment, mice were treated with the association of previously determined doses of each drug. Treatment started 48 hours post-infection, and lasted 10 days. The susceptibility of T. gondii to atovaquone and to sulfadiazine was different according to the parasite strain. It was observed strains that are susceptible to atovaquone, and strains that are resistant to it. Type I strains were more susceptible to the activity of sulfadiazine and more resistant to atovaquone. Yet type III strains were susceptible to atovaquone and to sulfadiazine. Association of atovaquone and sulfadiazine presented a synergic effect in the treatment of mice infected with RH type I strain and an additive effect in the treatment of mice infected with one type I strain and with two type III strains.

The effect of 14 natural and synthetic naphthoquinones in the replication of Toxoplasma gondii was evaluated. In vitro studies were accomplished in cultures of 2C4 fibroblasts infected with RH- strain. Enzyme-linked immunosorbent assay was used to quantify parasite growth. For the studies in vivo, mice were infected with tachyzoites of the RH strain or cysts of the T. gondii EGS strain. In vitro, seven naphthoquinones demonstrated significant inhibition of intracellular T. gondii growth at concentrations of 1 and 5 μg/ml. Only three compounds were significantly protective when tested in animals: 2-hydroxy-3'-(3'-pentenyl)-l ,4-naphthoquinone (PHNQ4), 2-hydroxy-3-(l'-vinylphenyl)-l,4-naphthoquinone (PHNQ5) and 2- hydroxy-3-(l'-propen-3'-phenyl)-1,4- naphthoquinone (PHNQ6). In animals infected with the EGS strain and treated with PHNQ4 (50 mg/kg/day orally), a 7-day prolongation of the time to death was observed. Treatment with 100 mg/kg/day orally or 50 mg/kg/day i.p. of PHNQ5 resulted in a 5-day and 16-day prolongation of the time to death, respectively. Treatment with 50 mg/kg/day orally or 50 mg/kg/day i.p. of PHNQ6 resulted in a 4-day prolongation of the time to death or up to 30 days after treatment, respectively. Our results suggest that the naphthoquinones may be important therapeutic agents for the treatment of toxoplasmosis.

With the purpose of establishing alternative parameters to determine the virulence of Toxoplasma gondii strains, the antigenic diversity of eight strains of the parasite isolated in Brazil was evaluated. BALB/c mice were inoculated i.p. with 100, 101, 102 and 103 tachyzoites from each strain. The mortality and time to death of the animals showed that T. gondii strains may be divided in three groups: three strains resulted in 100% of mortality, 5-10 days post inoculation (DPI); three strains resulted in 100% of mortality, 7-19 DPI and brain cysts were observed in the mice which were inoculated; two strains resulted in 0% of mortality, 30 DPI. The analysis of the antigenic profile of different T. gondii strains through Western blotting, using rabbit antiserum to T. gondii, revealed that most antigens are similar to all strains. The mAb 4C3H4 recognized antigens only in the RH, N, AS28 and ME49 strains..

Reported is an evaluation of 13 years of intervention by the Chagas Disease Control Programme in an endemic area (Montalvania) in the State of Minas Gerais, Brazil. The design used was an epidemiological panel study. The reduction of Trypanosoma cruzi infection rates was estimated from data collected on three separate occasions: a serological survey in 1975-80, a quasi-experimental study in 1987, and the present investigation. A random sample of 156 households was selected and blood samples were collected from 653 inhabitants. The data routinely collected by the control programme were analysed to correlate the results with the incidence ofT. cruzi. The overall prevalence of infection was 2.3%; however, no participant under 14 years of age was found to have a positive serological test. The total reduction in T. cruzi infection rates in this area from the start of the programme's activities was estimated to be 83.5%. Cross-sectional comparisons for the age groups 2-6 years and 7-14 years indicated a 100% reduction in T. cruzi incidence rates; but cohort comparisons showed that 100% reduction was achieved only for the 2-6-years age group., Introduction Public health services and programmes can be evaluated by different theoretical and methodological approaches which take into account the triad of structure-process-results (1). Since structure and process can rapidly [...]