On opportunist infections by Trypanosoma lewisi in humans and its differential diagnosis from T. cruzi and T. rangeli.

Trypanosoma lewisi is a cosmopolitan species originally found in Rattus spp., being nonpathogenic, host-restricted, and transmitted by rat fleas. This species has been recorded as an opportunist blood parasite of human beings mainly in Asia, with a case in Africa. In Brazil, this species was recently recorded in captive monkeys. As T. lewisi can share vertebrate hosts both with Trypanosoma rangeli and Trypanosoma cruzi, some markers for the differential diagnosis of these species were examined and discussed herein. The identification of T. lewisi was based on morphological features of bloodstream stages at the initial phase of infection in mammals, isoenzyme electrophoresis at the MDH locus, and PCR products of kinetoplast DNA (kDNA) minicircles using the primers TC121/TC122.

Variable sensitivity to complement-mediated lysis among Trypanosoma rangeli reference strains.

Six reference strains of Trypanosoma rangeli from different days of growth in axenic cultures were assayed for susceptibility to complement-mediated lysis by non-immune guinea-pig serum. Their authenticity was also confirmed by isoenzyme analyses. Parasites were incubated with 25% active or 68°C-inactivated serum (37°C, 30 min) for all tests; thereafter the lysis rates were determined. Highly variable lysis percentages were observed among T. rangeli strains and in the same stock at different growing days. In a few assays, three strains (Macias, R-1625 and Choachi) presented total or very high resistance. The others (H-14, San Agustín and SC-58) were generally most susceptible, and could reach lysis rates as high as Trypanosoma cruzi. After incubation with active sera, the epimastigotes were usually the predominant stages, being followed by spheromastigotes and/or transitional forms. Those stages and trypomastigotes could also be partially susceptible. In four strains, the short epimastigotes were more resistant to lysis than the long ones. Experiments with C3-deficient serum displayed total or partial participation of the alternative-complement pathway in T. rangeli lysis. This study confirmed the variable complement sensitivity of T. rangeli, which can be related to its intraspecific heterogeneity, to the remarkable complexity of its life-cycle stages, and to the methodology employed.

Sera of patients with systemic lupus erythematosus react with plasmodial antigens and can inhibit the in vitro growth of Plasmodium falciparum.

The acquisition of protective immunity in malaria is a slow process during which autoantibodies are produced. The present work aimed at studying a possible interference of autoimmune responses on malaria immune protection. This was done by investigating the presence of autoantibodies in the sera of malarious patients, by searching for reactivity of autoantibodies from autoimmune patients against plasmodial antigens, and by studying the effect of such antibodies on the in vitro growth of Plasmodium falciparum. Sera from systemic lupus erythematosus (SLE) and malaria patients were tested against autologous and plasmodial antigens. Out of the 109 SLE sera tested, 48 (44%) reacted against the parasite. In addition, 26 (47%) out of 55 randomly selected sera, mainly those containing anti-DNA and antinuclear autoantibodies, were able to inhibit parasite growth to some extent. Conversely, a high frequency (81%) of sera of malaria patients exhibited reactivity against autoantigens. The results show that patients with autoimmune processes can produce antibodies that recognize plasmodial antigens in the absence of plasmodial infection, that malaria patients can produce autoantibodies, that SLE sera can inhibit plasmodial growth in vitro, and that the presence of anti-DNA and antinuclear antibodies may be important in such anti-plasmodial activity. It is concluded that autoimmune responses may have influence on the protective immunity against malaria.

Trypanosoma rangeli Tejera, 1920, in chronic Chagas' disease patients under ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC-Fiocruz, Brazil).

We report the finding, the isolation by hemoculture, and the characterization of Trypanosoma rangeli stocks from two chronic Chagas' disease patients who received ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC, FIOCRUZ). Both patients proceeded from Bahia State (Brazil). One of them presented the cardiac form of the disease and the other indeterminate symptomalogy. Giemsa-stained smears of the hemocultures from these patients evidenced that they were coinfected with T. rangeli and Trypanosoma cruzi, with predominance of the former species. These isolates could only be successfully grown in Novy-MacNeal-Nicolle + liver infusion-tryptose supplemented with 20-30% fetal calf serum. After 6 months of serial maintenance, rich and apparently pure cultures of T. rangeli were obtained. Both stocks were analyzed with different approaches and compared with two T. cruzi isolates also from chagasic patients under care at IPEC, besides T. rangeli and T. cruzi reference strains. All stocks were characterized by morphology, biometry, electrophoresis of isoenzymes, and products of kDNA minicircle amplified by polymerase chain reaction. The identification of T. rangeli was largely confirmed by all techniques. Taken together, these data represent the third report on T. rangeli in human hosts in Brazil.