PATHOGENICITY OF Blastocystis sp. TO THE GASTROINTESTINAL TRACT OF MICE: RELATIONSHIP BETWEEN INOCULUM SIZE AND PERIOD OF INFECTION

The pathogenic potential of Blastocystis sp. in experimental models requires further investigation. In this work, the pathogenicity of this parasite in the gastrointestinal tract of male Swiss mice was evaluated according to the inoculum size and period of infection. Animals were infected intragastrically, with 100, 500, 1,000, 5,000 and 10,000 Blastocystis sp. vacuolar forms obtained from a mixture of eight human isolates cultured axenically in Jones' medium. After seven, 14, 21, 28 and 60 days of infection, the animals were sacrificed and fragments of the small intestine (duodenum), large intestine, and cecum were subjected to histopathological analysis. Blastocystis sp. triggered an inflammatory response in the different tissues analyzed, with a predominance of mononuclear cells. The parasite was found in the muscular layer of the cecum, showing its invasive character. Larger inocula triggered inflammatory processes earlier (seven days) than smaller ones (from 21 days). We conclude that, in the proposed model, the pathogenicity of Blastocystis sp. isolates that were studied is related to inoculum size and period of infection.

CD19 LYMPHOCYTE PROLIFERATION INDUCED BY Bifidobacterium animalis subsp. lactis IN C57BL/6 MICE EXPERIMENTALLY INFECTED WITH Toxoplasma gondii

Toxoplasmosis is frequently acquired through the oral route by the ingestion of cysts or oocysts of Toxoplasma gondii. Once ingested, the parasites penetrate the intestinal epithelial cells and rapidly disseminate to all organs in the host. During T. gondii infection, the intestinal microbiota plays an important role in stimulating a protective immune response against the parasite. In this sense the use of probiotics is worthy of note since they are live microorganisms that have beneficial effects on the host through stimulation of the immune response that can be important in the control of T. gondii proliferation and dissemination in the host. In the present study, the action of the probiotic Bifidobacterium animalis subsp. lactis was investigated in C57BL/6 mice infected with oocysts of ME49 strain of T. gondii. The probiotic had an immunomodulatory action, inducing CD19 lymphocyte proliferation and consequently increasing anti-T. gondii antibody level.Bifidobacterium animalis subsp. lactisprovided protection in supplemented mice, compared to the control group. In addition, supplemented animals had milder inflammatory process in the small intestine, indicating that the probiotic protects the intestinal mucosa during infection with T. gondii. It was concluded that the probioticB. animalis subsp. lactis induces humoral immune response capable of providing protection against T. gondii infection.

EVALUATION OF THE THERAPEUTIC EFFICACY OF LEVAMISOLE HYDROCHLORIDE ON THIRD-STAGE LARVAE OF Lagochilascaris minor IN EXPERIMENTALLY INFECTED MICE

Lagochilascariosis, a disease caused by Lagochilascaris minor, affects the neck, sinuses, tonsils, lungs, the sacral region, dental alveoli, eyeballs and the central nervous system of humans. A cycle of autoinfection may occur in human host tissues characterized by the presence of eggs, larvae and adult worms. This peculiarity of the cycle hinders therapy, since there are no drugs that exhibit ovicidal, larvicidal and vermicidal activity. Given these facts, we studied the action of levamisole hydrochloride on third-stage larvae in the migration phase (G1) and on encysted larvae (G3) of L. minor. To this end, 87 inbred mice of the C57BL/6 strain were divided into test groups comprising 67 animals (G1-37; G3-30) and a control group (G2-10; G4-10) with 20 animals. Each animal was inoculated orally with 2,000 infective eggs of the parasite. The animals of the test groups were treated individually with a single oral dose of levamisole hydrochloride at a concentration of 0.075 mg. The drug was administered either 30 minutes prior to the parasite inoculation (G1 animals) or 120 days after the inoculation (G3 animals). The mice in the control groups were not treated with the drug. After the time required for the migration and the encysting of L. minor larvae, all the animals were euthanized and their tissues examined. The data were analyzed using the Student's unpaired t-test and the Levene test. The groups showed no statistically significant difference. Levamisole hydrochloride was ineffective on third-stage larvae of L. minor. These findings explain the massive expulsion of live adult worms, as well as the use of long treatment schemes, owing to the persistence of larvae and eggs in human parasitic lesions.

Experimental studies on Trypanosoma (Schizotrypanum) cruzi strains isolated from man, from animals and from triatomine bugs in Brazil

A study on nine strains of T. cruzi isolated from man, from animais and from triatomine bugs in Brazil are described. The parasites were slightly viscerotropic in white mice in six of the strains, highly viscerotropic and cardiotropic in two strains, and asymptomatic on one strain. Mechanical and cyclical passage from infected to healthy mice, and treatment of the infected mice with immunosuppressant drug, did not increase the blood parasitaemia or strain virulence. The results of biometric studies on the blood trypanosomes from each strain are also described. The various aspects on the importance of T. cruzi strain Identification are emphasized and discussed.

The effect of a dialyzable transfer factor (TFd) in the experimental american trypanosomiasis of mice: preliminary report

A dialyzable transfer factor (TFd) was obtained from spleen cells, of mice vaccinated with the avirulent PF strain of Trypanosoma cruzi. This factor reduced significahtly the parasitemia of animals treated before or after the infection with a virulent strain of the same parasite, but does not reduced the mortality rate to a level lower than that of the control mice. It is expected that in a next future, new techniques in the use ofsuch factor will bring better resutts.

Course of infection and histopathological lesions in mice infected with seventeen Trypanosoma cruzi strains isolated from chronic patients

Mice were infected with blood forms of 17 Trypanosoma cruzi strains recently isolated from chronic patients, which were dassified as of low, medium or high virulence on grounds of the prepatent period, parasitemia and mortality at the acute phase. A total of 212 mice were studied after 3, 6, 9 and 12 months of infection. In the chronic phase, intracellular parasites were detected in 11.0%,27.9%and 54.0,% of mice inoculated, respectively, with the low, medium and high virulent strains (r= 0.98, p < 0.005). Heart fibrosis was also related to virulence, affecting 5.7%, 11.6%and30.8% (r = 0.98, p < 0.001) of the mice inoculated with the above strains; a similar relationship was observed between intensity and frequency of the heart inflammatory reaction and the severity of infection at its early stage. Necrotizing arteritis was detected in 12.2% of the inoculated animals and this lesion was related to the infection duration rather than to strain characteristics. Inflammatory lesions and tissue parasitism were stable within the period of observation, whereas fibrosis was Progressive. The findings suggest that mice may reproduce heart lesions resembling human pathology and that organ damage apparently depends on the parasite virulence.

Evolution of sarcoma 180 (ascitic tumor) in mice infected with Schistosoma mansoni

Mice infected with 60 cercariae of Schistosoma mansoni were more resistant to the sarcoma 180 ascites tumor. Tumor inoculation was performed 50 days after schistosoma infection and the animals were observed and weighed at 48 hours intervals for development and progression of malignancy. In infected mice the weight gain (ascites formation) started later and was shorter than in uninfected Controls. Also, the number of tumor cells into the peritoneal cavity 72h after tumor implantation was shorter in infected group than incontrols. This in creased resistance against a transplantable tumor probably is related to the effect of endotoxin on tumoricidal activity of macrophages activated by the infection. The immunodepression induced by Schistosoma mansoni infection enhances the proliferation of endogenous bacteria increasing the amount of endotoxin absorbed from the gut.

Liver and serum soluble protein changes and pathomorphology in undernourished mice with acute Schistosomiasis mansoni

Body, liver and spleen weights; histopathology of the liver, spleen and intestines; hepatic and serum soluble proteins changes were the parameters studied in undernourished Swiss albino mice experimentally infected with S. mansoni. Non-infected deficient animab had lower liver/body weight and spleen/body weight ratios as compared to the controls (22.60% casein group). Infected mice showed higher values regardless the type of diet. Undernourished infected subgroup showed a persistent exudative periovular reaction in the liver. Soluble hepatic proteins content and serum protein fractions appeared to be lower in the deficient infected mice. A significant difference was detected in the gammaglobulin fraction between infected and non-infected animals fed the control diet with higher values for the former. Our data suggest that the effects of malnutrition, per se, are sometimes more detrimental to the host than those due to Manson 's schistosomiasis.

The influence of the regional basic diet from northeast Brazil on health and nutritional conditions of mice infected with Schistosoma mansoni

Protein nutritionalstatus indicators were studied in weanling albino Swiss mice infected with S. mansoni andfed the Regional Basic Diet (RBD)from Northeast Brazil, a multideficient diet of low-protein content. Each mouse was infected percutaneously with 80 cercariae. The experiment lasted 63 days. The growth curve, food consumption, protein intake, weight gain, Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) were the parameters investigated. RBD-fed mice showed a marked weight loss, a lower food and protein intake, a slower body weight gain and lower rates of food protein utilization when compared to casein-fed animals. Differences between infected and non-infected mice were not consistent. The present results suggest that the effects of RBD-induced malnutrition on health and nutritional conditions of the mice are more severe than those of Manson's schistosomiasis, in the initial phase of the disease.

Effects of severe protein restriction in levels of parasitemia and in mortality of mice accutely infected with Trypanosoma cruzi

Adult mice were submitted to different degrees of protein restriction for five weeks (4.75, 9.5,14.25 and 19% of protein in isocaloric diets with normal content of mineral and vitamins), being subsequently infected with two strains of Trypanosoma cruzi: 10(5) trypomastigotes of Y strain or 14(5) trypomastigotes of CL strain. The same diet was maintained for all animals and the infection wasfollowed up by evaluation of blood parasites, mortality and intensity of lesions in the heart and skeleton muscle. Only severe protein restriction (4.75%) induced decrease in resistance to the infection with both the Y and CL strains of T. cruzi, which resulted in higher parasitemia and mortality. The inflammatory lesions in heart and skeleton muscle were less extensive in groups with severe protein restriction despite the increased number of parasite in muscle cells. Depression of immune mechanisms could be responsiblefor the reduced resistance and reduced inflammatory reaction after T. cruzi infection in severely protein restricted animals.

Schistosoma mansoni in mice: modulation of granulomatous response after reinfection and chemotherapeutic treatment

Mice previously infected with Schistosoma mansoni, and cured by specific treatment (400mg/kg oxamniquine, p. o.) in the chronic phase of the disease, were reinfected 20 days after treatment to assess their capacityfor modulation ofthe granulomatous response. Histopathologic examination of the animals ' liver, at 60 days after reinfection, evidenced the presence of typical granulomas of the chronic phase in most animals. This infer that the capacity for modulation of the granulomatous response had been maintained, thus preventing a new acute phase of the disease. Conversely, a group of previously infected mice, untreated and submitted to reinfection, showed reactivation of the granulomatous response in 50% of the animals. The possible implications of these findings in human schistosomiasis mansoni are discussed.

Hepatic pathology in Capillaria hepatica infected mice

Septal fibrosis of the liver regularly develops in rats infected with Capillaria hepatica. To find out whether such fibrosis also occurs in mice, 20 animals were submitted to infection with either 100 or 300 embryonated eggs and histologically examined after several periods of time, from 30 to 110 days afterwards. Results showed that mice developed acute, severe, diffuse and focal hepatic lesions that were soon modulated to focal areas of fibrosis containing eggs and worm remnants, despite the fact that a few worms remained alive, at least up to 110 days after inoculation. Areas of perisinusoidal fibrosis appeared in the proximity and around focal parasitic lesions, but clear-cut septal fibrosis was not observed. Why septal fibrosis forms in rats, but not in mice during C. hepatica infection, only further studies can clarify. Mice seem to show better host/parasite relationship than rats in regard to C. hepatica infection.

Vaccination of C57BL/10 mice against cutaneous leishmaniasis using killed promastigotes of different strains and species of Leishmania

Antigenic extracts from five Leishmania stocks were used to vaccinate C57BL/10 mice. The Leishvacin® and PH8 monovalent vaccine yielded the highest IFN-gamma levels in the supernatants of spleen cell culture from vaccinated animals. Each single strain immunized group showed evidence of protective immunity six months after the challenge with promastigotes of Leishmania (Leishmania) amazonensis. No differences were detected between the vaccinated groups. It can be concluded that vaccines composed of single Leishmania stocks can provide protection to C57BL/10 mice against L. (L.) amazonensis infection.

The use of protein hydrolysate improves the protein intestinal absorption in undernourished mice infected with Schistosoma mansoni

Patients residing in endemic areas for schistosomiasis in Brazil are usually undernourished and when they develop the hepatosplenic clinical form of the disease should usually receive hospital care, many of them being in need of nutritional rehabilitation before specific treatment can be undertaken. In the mouse model, investigations carried out in our laboratory detected a reduced aminoacid uptake in undernourished animals which is aggravated by a superimposed infection with Schistosoma mansoni. However, in well-nourished infected mice no dysfunction occurs. In this study, we tried to improve the absorptive intestinal performance of undernourished mice infected with S. mansoni by feeding them with hydrolysed casein instead of whole casein. The values obtained for the coefficient of protein intestinal absorption (cpia) among well-nourished mice were above 90% (either hydrolysed or whole protein). In undernourished infected mice, however, the cpia improved significantly after feeding them with hydrolysed casein, animals reaching values close to those obtained in well-nourished infected mice.

Structural changes in the jejunal mucosa of mice infected with Schistosoma mansoni, fed low or high protein diets

The effects of high and low-protein diets on the structure of the jejunal mucosa were studied in Schistosoma mansoni infected mice (morphology and histomorphometry). Weaning male albino mice were infected with 80 cercariae, fed with high (20%) or low-protein (5%) diets and compared to uninfected controls under the same conditions. Mice were sacrificed 12 weeks after infection. Animals submitted to a low-protein diet showed lower weight curves, mainly when infected. In the jejunal mucosa, finger-like villi were the predominant pattern among uninfected high-protein fed animals, while the infected ones showed leaf-shaped and flattened villi in most cases. Undernourished infected mice had 65.7% leaf-shaped villi. A significant increase in the number of goblet cells was seen in infected mice. A decrease in the number of absorptive cells was detected in undernourished mice, particularly in infected ones.