Heitor Franco de Andrade

Antileishmanial and antitrypanosomal activity of bufadienolides isolated from the toad Rhinella jimi parotoid macrogland secretion

Amphibian skin secretions are considered a rich source of biologically active compounds and are known to be rich in peptides, bufadienolides and alkaloids. Bufadienolides are cardioactive steroids from animals and plants that have also been reported to possess antimicrobial activities. Leishmaniasis and American Trypanosomiasis are parasitic diseases found in tropical and subtropical regions. The efforts toward the discovery of new treatments for these diseases have been largely neglected, despite the fact that the only available treatments are highly toxic drugs. In this work, we have isolated, through bioguided assays, the major antileishmanial compounds of the toad Rhinella jimi parotoid macrogland secretion. Mass spectrometry and (1)H and (13)C NMR spectroscopic analyses were able to demonstrate that the active molecules are telocinobufagin and hellebrigenin. Both steroids demonstrated activity against Leishmania (L.) chagasi promastigotes, but only hellebrigenin was active against Trypanosoma cruzi trypomastigotes. These steroids were active against the intracellular amastigotes of Leishmania, with no activation of nitric oxide production by macrophages. Neither cytotoxicity against mouse macrophages nor hemolytic activities were observed. The ultrastructural studies with promastigotes revealed the induction of mitochondrial damage and plasma membrane disturbances by telocinobufagin, resulting in cellular death. This novel biological effect of R. jimi steroids could be used as a template for the design of new therapeutics against Leishmaniasis and American Trypanosomiasis.

The prevalence and avidity of Toxoplasma gondii IgG antibodies in pigs from Brazil and Peru

Raw or inadequately cooked pork is an important source of Toxoplasma gondii infection, and the infection rate in animals used as human food, is an important risk predictor. The prevalence of this infection was estimated in 396 sera from 5-month old pigs obtained at abattoirs in São Paulo, Brazil (300) and Lima, Peru (96). The seroprevalence was higher in pigs from Peru (32.3%) as compared to Brazil (9.6%), as detected by ELISA and Western blot. Hemagglutination gave poor resolution which was not useful for the diagnosis of T. gondii infection. Specific antibody avidity is correlated with infection time, as shown in experimentally infected piglets. Using an arbitrary cut-off of 50% avidity index, Brazilian pigs were found to be more recently infected than Peruvian pigs. Pork should be considered a significant source of human T. gondii infection both in Brazil and Peru. Avidity assays could help in the detection of the time of T. gondii infection in pigs, allowing preventive management.

200 Gy sterilised Toxoplasma gondii tachyzoites maintain metabolic functions and mammalian cell invasion, eliciting cellular immunity and cytokine response similar to natural infection in mice

200Gy gamma-irradiated Toxoplasma gondii RH tachyzoites failed to reproduce in vitro and in vivo. In short-term cultures, these parasites maintained a respiratory response, the ability to invade cells and preserved protein and nucleic acid synthesis. ELISA and Western blotting techniques demonstrated the similarity in humoral response between mice infected with gamma-irradiated tachyzoites and animals infected with naive parasites and treated with sulfadoxine, higher than mice immunised with formaldehyde-killed tachyzoites. Splenocyte stimulation by T. gondii antigen produced lymphoproliferative response and cytokine profile (IL-10, IL-12, IFN-gamma and TNF-alpha) similar to those produced by chronic natural infection. Mice immunised with irradiated tachyzoites had extended survival times after subsequent tachyzoite challenge, and displayed minimal cerebral pathology after cyst challenge. Irradiated tachyzoites lose their reproductive ability whilst maintaining metabolic function and may provide a novel tool for the study of toxoplasmosis and vaccine development.

Synthesis and Antileishmanial Activities of Novel 3-Substituted Quinolines

ABSTRACT The antileishmanial efficacy of four novel quinoline derivatives was determined in vitro against Leishmania chagasi, using extracellular and intracellular parasite models. When tested against L. chagasi-infected macrophages, compound 3b demonstrated 8.3-fold greater activity than did the standard pentavalent antimony. No significant activity was found for compounds 3a, 4a, and 4b. The antilesihmanial effect of compound 3b was independent of host cell activation, as demonstrated by nitric oxide production. Ultrastructural studies of promastigotes treated with compound 3b showed mainly enlarged mitochondria, with matrix swelling and reduction in the number of cristae. Synthetic analogues based on the quinoline ring structure, already an established template for antiparasitic drugs, could provide further useful compounds.

Mucosal leishmaniasis: in situ characterization of the host inflammatory response, before and after treatment

Mucosal leishmaniasis (ML) generally shows progressive tissue destruction, not yet fully elucidated, associated with an intense inflammatory response. To contribute to the understanding of this process and of how treatment interferes with it, we studied several anatomopathological parameters, including those analyzed by immunohistochemistry, such as Leishmania antigens, cells participating in the immune response and cytokine expression. Biopsies were taken from 20 patients with ML before and after treatment. A mixed Th1 and Th2 pattern response occurred inside ML before treatment, persist after treatment. Nevertheless, this mixed response was smaller than in active lesions, with reduced but present numbers of cells expressing TNF-alpha, IFN-gamma and IL-4 and sustained numbers of cells expressing IL-10. We may conclude that specific treatment causes a reduction of inflammatory lesions and disappearance of amastigote forms of Leishmania although the factors related to the pathogenesis of the lesion, such as T CD4+ and T CD8+ lymphocytes and Leishmania antigens, persist in treated lesions. The maintenance of these inflammatory patterns may be due to a specific host-parasite relationship response, strongly indicating the need for continuous surveillance of LM patients at risk of reactivation, despite effective cicatrization after therapy.

Toxoplasma gondii Pneumonia in Immunocompetent Subjects: Case Report and Review

Pulmonary toxoplasmosis is rare in immunocompetent subjects. Here, we describe a 41-year-old previously healthy male patient who presented to the emergency department of a hospital with a life-threatening case of pneumonia due to Toxoplasma gondii infection, which responded to specific therapy. Clinical and image-based findings overlap with those for atypical pneumonias, and toxoplasmosis should be considered in the differential diagnosis--especially if immunoglobulin M-specific antibodies are detected.

Infectivity of cysts of the ME-49 Toxoplasma gondii strain in bovine milk and homemade cheese

OBJECTIVE Analyze the infectivity and storage resistance of cysts of the ME-49 strain of Toxoplasma gondii in artificially infected bovine milk and homemade fresh cheese. METHODS Pasteurized bovine milk was infected with 10 cysts/ml of the ME-49 strain of T.gondii and inoculated in different groups of mice, immediately or after storage at 4 degrees C for 5, 10 and 20 days. Homemade fresh cheese was prepared with artificially infected milk, and also tested in groups of mice, using the same storage process. Infection was identified by the presence of cysts in the brain or serological testing in challenged mice after 5 weeks, confirmed by Western Blot and histology. RESULTS The infectivity of cysts of the ME-49 strain of T.gondii was maintained in the milk even after storage for 20 days at refrigerator temperatures. Cysts were also able to survive the production process of homemade fresh cheese and storage for a period of 10 days in the same conditions. CONCLUSIONS These data demonstrated that milk and dairy products could be an important source of T.gondii in human contamination, reinforcing the importance of milk pasteurization before any processing or ingestion.

Evaluation of tests for antibody response in the follow-up of patients with acute and chronic forms of paracoccidioidomycosis

Several serological tests have been used successfully in the diagnosis of paracoccidioidomycosis (PCM). In contrast, data about the use of these tests in the follow-up of PCM patients have been heterogeneous. In this study, serum samples from 43 PCM patients with different clinical forms were analysed by counter-immuno-electrophoresis (CIE), complement fixation (CF) and ELISA before treatment. With CIE and ELISA, the chronic unifocal form showed significantly lower antibody levels compared with chronic multifocal and acute forms. Acute form patients had significantly higher titres than patients with multifocal disease by CIE but not by ELISA. No significant differences were observed with CF. Twenty-seven of these patients were followed-up for 2 years and showed a decline in antibody levels by all three tests, paralleling clinical improvement. However, only patients with unifocal disease cleared their antibodies after 1 year of treatment as analysed by CF and ELISA and after 2 years by CIE, suggesting that these patients may need shorter courses of therapy. Patients with the other clinical form of the disease needed > or =2 years of therapy to clear their antibodies. Sera from a further five patients who presented with a relapse were analysed. At the time of relapse all showed increases in antibody levels by CIE and ELISA, but only three showed increases by CF tests. Therefore, CIE and ELISA demonstrated a better clinical correlation than CF, probably reflecting the fungal burden of PCM patients more accurately.

Serological survey of antibodies to Toxoplasma gondii in food animals from São Paulo state, Brazil

Toxoplasmosis is one of the most prevalent parasitic infections of man and livestock, and its transmission has usually been attributed to ingestion of undercooked or raw meat from infected livestock, with the infection rate in those animals being an important risk predictor of human disease, high in Brazil and Sao Paulo State. Looking for this public health problem, we tested serum samples from cattle, goat, sheep and chicken from the State of Sao Paulo, Brazil, for IgG antibodies to Toxoplasma gondii by enzyme-linked immunosorbent assay (ELISA). Antibodies to Toxoplasma gondii were found in 31.00% (62/200) of sheep, 17.00% (34/200) of goat and 11.00% (22/200) of cattle, without positive sample in chicken. Despite differences in feeding habits of each species, the rate of infection of tested animals could be better attributed to livestock management methods, which improvement could reduce infection.

Prostaglandin and nitric oxide regulate TNF-α production during Trypanosoma cruzi infection

Abstract The mechanisms that control TNF- α production by macrophages during Trypanosoma cruzi infection are still unknown. Destruction of intracellular forms by cytokine activated macrophages is considered to be a major mechanism of parasite elimination. Although in vitro TNF- α contributes to enhanced parasite destruction by macrophages, previous work in vivo has shown that as the parasite burden increases, serum TNF- α levels decline. In this report we show that TNF- α production by peritoneal adherent cells is elevated at the initial phase of T. cruzi infection. As infection progresses TNF- α production decreases. The observed reduction is partly due to inhibition, largely exerted by endogenous PG and secondarily by NO. Inhibition of their synthesis partially restored the ability to produce high levels of TNF- α to macrophages upon stimulation by LPS. Neither endogenous IL-10 nor TGF- β seem to be involved in the negative regulation of TNF- α production.