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Pathological aspects of a subclinical form of experimental canine leishmaniasis is reported here for the first time. Fifteen mongrel dogs were used in the present study. Eight dogs were infected and seven were used as control. Four of the control dogs were inoculated with spleen cells from non-infected hamsters. The eight mongrel dogs inoculated intravenously with amastigotes forms of Leishmania chagasi envolved for periods as long as 25 months without any clinical characteristic sign of classical Visceral Leishmaniasis (VL). Most of the laboratory test results were compatible to those of the seven control animals but culture of bone marrow aspirated material and serologic testing (IIF) demonstrated or provided evidence that the animals were infected. The most important and predominant histopathological lesion in infected animals were epitheloid granulomas presented in the liver, spleen, adrenal gland and lung of some animals. Channels containing erythrocytes in some granulomas of the liver suggeste that these granulomas are formed inside sinusoidal capillaries. Despite the animals were proved to be infected and presented characteristic histologic lesions, they did not present external signs of disease. The granulomatous aspect of the lesions indicates a good immunologic reactivity and suggest that a host-parasite equilibrium does exist in the dog experimental model

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Pathological aspects of a subclinical form of experimental canine leishmaniasis is reported here for the first time. Fifteen mongrel dogs were used in the present study. Eight dogs were infected and seven were used as control. Four of the control dogs were inoculated with spleen cells from non-infected hamsters. The eight mongrel dogs inoculated intravenously with amastigotes forms of Leishmania chagasi evolved for periods as long as 25 months without any clinical characteristic sign of classical Visceral Leishmaniasis (VL). Most of the laboratory test results were compatible to those of the seven control animals but culture of bone marrow aspirated material and serologic testing (IIF) demonstrated or provided evidence that the animals were infected. The most important and predominant histopathological lesion in infected animals were epithelioid granulomas presented in the liver, spleen, adrenal gland and lung of some animals. Channels containing erythrocytes in some granulomas of the liver suggest that these granulomas are formed inside sinusoidal capillaries. Despite the animals were proved to be infected and presented characteristic histologic lesions, they did not present external signs of disease. The granulomatous aspect of the lesions indicates a good immunologic reactivity and suggest that a host-parasite equilibrium does exist in the dog experimental model.

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A kinetic study of the cells present in the spleen of BALB/c mice infected with Schistosoma mansoni was carried out. The lymphocytes were evaluated phenotypically with monoclonal antibodies and the effect of splenectomy on the modulation of periovular granuloma was also investigated. The infected mice had proportional increases in the numbers of neutophils, plasma cells, macrophages and eosinophils in the spleen. The largest number of neutrophil, plasma cells and macrophage were found between the 8th and the 12th week of infection, while the amount of eosinophils were higher later on, around the 20th week. The lymphocytes phenotipically characterized as Thy 1.2, Lyt 1.2 (CD4) increased mildly in proportional numbers. However, the percentage of lymphocytes with the Lyt 2.2 (CD8) phenotype, which is characteristic of supressor and cytotoxic T cells, increased significantly with the progress of the disease. The numbers of B lymphocytes, which comprise 50% of the mononuclear cells present in the spleen, increased significantly till the 16th week they began to decrease. The mean diameters of periovular granulomas were comparatively similar in both experimental groups (splenectomized and non-splenectomized mice). However, the evolutive types of granuloma (exudative, intermediate and fibrous) in splenectomized mice were proprtionally different from those of non splenectomized mice in the 16th and 24th week of infection. It is inferred that lymphonodes or other secondary lymphoide organs, in the abscence of the spleen, assume a modulating action on periovular granulomas, although the evolution of the granulomas is somehow delayed in splenectomized mice

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A kinetic study of the cells present in the spleen of BALB/c mice infected with Schistosoma mansoni was carried out. The lymphocytes were evaluated phenotypically with monoclonal antibodies and the effect of splenectomy on the modulation of periovular granuloma was also investigated. The infected mice had proportional increases in the numbers of neutrophils, plasma cells, macrophages and eosinophils in the spleen. The largest number of neutrophil, plasma cells and macrophage were found between the 8th and the 12th week of infection, while the amount of eosinophils were higher later on, around the 20th week. The lymphocytes phenotypically characterized as Thy 1.2, Lyt 1.2 (CD4) increased mildly in proportional numbers. However, the percentage of lymphocytes with the Lyt 2.2 (CD8) phenotype, which is characteristic of suppressor and cytotoxic T cells, increased significantly with the progress of the disease. The numbers of B lymphocytes, which comprise 50% of the mononuclear cells present in the spleen, increased significantly till the 16th week when they began to decrease. The mean diameters of periovular granulomas were comparatively similar in both experimental groups (splenectomized and non-splenectomized mice). However, the evolutive types of granuloma (exudative, intermediate and fibrous) in splenectomized mice were proportionally different from those of non splenectomized mice in the 16th and 24th week of infection. It is inferred that lymphnodes or other secondary lymphoid organs, in the absence of the spleen, assume a modulating action on periovular granulomas, although the evolution of the granulomas is somehow delayed in splenectomized mice.

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We performed different "in vivo" investigations to study the pharmacological properties of a native DS: anti-thrombosis by the stasis model, bleeding potential by tail transection bleeding time and template bleeding time, and profibrinolysis by a growing thrombus model and by an established thrombus model. The results suggest that DS is a safe antithrombotic drug by i.v. administration without bleeding potential, even at very high doses (up to 16 mg/Kg). DS has shown a protective index of at least 4 in contrast to heparin that has shown a protective index of 1. The profibrinolytic models so far studied did not evidence a clear profibrinolytic contribution to the antithrombotic properties of DS, but showed a prolonged antithrombotic action that cannot be explained only by the heparin cofactor II potentiation.

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The study of the surface antigens of Leishmania braziliensis braziliensis revealed a great homogeneity among ten strains isolated from Bolivia and two reference strains from Brazil and Belize. A 72 kDa major protein, present in all L. b. braziliensis strains, was recognized by both cutaneous and mucocutaneous human sera, but was not recognized by Kala-azar and chagasic sera. No cross-reactive antigens were found among strains of Leishmania braziliensis guyanensis, Leishmania braziliensis panamensis, Leishmania mexicana amazonensis and Leishmania donovani chagasi testing these strains with hamster and human anti-L. b. braziliensis sera. Moreover, these strains possessed major antigens with molecular weights different from those of L. b. braziliensis strains. A microheterogeneity of L. b. braziliensis surface antigens was detected for the high molecular weight antigens and seemed to be related to the isoenzymic microheterogeneity.

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Foi usado um teste imunoenzimático competitivo para investigar a presença de anticorpos anticomponente 5 nos soros de sariguês, cäes, coelhos e ratos infectados com o Trypanosoma cruzi. Neste teste, foi utilizado um anticorpo monoclonal contra o antígeno 5 que é específico do T. cruzi. Também foram testados os soros de 51 pacientes venezuelanos com doença de Chagas. Apesar desses anticorpos näo serem detectados nos soros de cäes, ratos e sariguês infectados com o T. cruzi, alguns soros de coelhos infectados apresentaram resultados positivos porém em níveis próximos aos do limite de positividade do teste. Esses achados surgerem que a resposta imune em animais naturalmente ou experimentalmente infectados com o T. cruzi é diferente daquela que é observada na doença de Chagas humana

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Sequential development of Leishmania braziliensis promastigotes from a noninfective to an infective stage was demonstrated. The generation of infective forms was related to their growth cycle and restricted to stationary stage organisms. Using immunofluorescence techniques, we have noticed that the binding of a monoclonal antibody (mAb) against L. braziliensis (VD5/25) increased progressively as the promastigotes developed in culture and was maximal with the infective forms. This antigenic differentiation was not detected with an anti-L. braziliensis polyclonal rabbit antiserum, suggesting that only a few epitopes, including that recognized by VD5/25, have their expression effectively increased on the surface of infective promastigotes. Immunoprecipitation of lysates of surface-iodinated L. braziliensis promastigotes with this mAb revealed two proteins of apparent 65,000 and 50,000 Mr, the 50,000 Mr protein probably representing the unreduced form of the major surface glycoprotein described in several species of Leishmania (GP65). The increasing expression of this epitope was not found with L. chagasi promastigotes, but seems to occur with the parasites from the L. mexicana complex. Intracellular survival of L. braziliensis was completely inhibited when the infective promastigotes were treated with VD5/25. It appears, therefore, that the increasing expression of GP65 on the promastigote surface represents an essential mechanism of leishmania survival in the macrophage.

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Complement-dependent cytotoxic antibodies were found in 54% of Schistosoma mansoni infected patients from Burundi and in 69 to 78% of Schistosoma mansoni ninfected Brazilian patients. The levels of cytotoxic Ab were not statistically different in sera from infected mothers and from their newborn children, suggesting a transfer through the placenta. A sandwich radioimmunoassay (SRIA) and the Radioimmunoprecipitaion-PEG assay (RIPEGA) technique were used in order to detect respectively total schistosome circulating soluble antigens (CSA) and schistosome antigen '4' in sera from infected patients. An inverse relationship was found between the presence of cytotoxic Ab and both total CSA and antigen '4'. The cytotoxic Ab and total CSA levels were followed in five Erythrocebus patas monkeys for 30 weeks after Schistosoma mansoni infection. As in human schistosomiasis the presence of cytotoxic Ab was found to be inversely correlated with the presence of total CAS. The blocking role of Schistosoma mansoni antigens in a complexed form was suggested by the inhibitory effect of the ultracentrifugation pellet of infected human serum on the cytotoxic activity. Moreover, the CSA absorption of infected monkey serum by passage through an anti-CSA immunosorbent significantly increased the cytotoxic activity. Possible mechanisms for the inhibitory role of circulating immune complexes on complement-dependent cytotoxic activity are discussed.

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