Partial protection against tissue cysts formation in pigs vaccinated with crude rhoptry proteins of Toxoplasma gondii.

A vaccine containing crude Toxoplasma gondii rhoptry proteins incorporated in the immunostimulating complexes (ISCOM) adjuvant was tested in pigs for protecting against tissue cyst formation. For this, 38 mixed breed pigs were divided into four groups, G1 (vaccinated challenged, n=10) received two doses (100 microg/dose) of the rhoptry vaccine at days 0 and 21, G2 (vaccinated challenged, n=10) received viable tachyzoites (7 x 10(7)) of the RH strain at day 0, G3 (unvaccinated challenged, n=10) and G4 (unvaccinated unchallenged, n=8). Pigs were challenged with 4 x 10(4) VEG strain oocysts 57 days later. The G1 pigs produced high IgG antibody levels in the indirect enzyme-linked immunosorbent assay (ELISA) after the second dose of rhoptry vaccine, but were not clinically protected against a high dose oocyst challenge. Partial protection was observed in G1 at the chronic phase of infection, when compared with G3. Pigs in group 2 developed high antibody levels and were protected against clinic signs. T. gondii was not detected in two (G1) and three (G2) pigs by mouse bioassay. The results indicate partial protection in pigs vaccinated with a rhoptry vaccine.

Mast cell and eosinophils in the wall of the gut and eosinophils in the blood stream during Toxocara vitulorum infection of the water buffalo calves (Bubalus bubalis).

Toxocara vitulorum is a pathogenic nematode from the small intestine of very young buffalo calves. To understand the development of the inflammatory responses in the wall of the gut, samples of tissues were removed from the duodenum, jejunum and ileum of buffalo calves naturally infected with T. vitulorum during the beginning of the infection, at the peak of egg output, as well as during the periods of rejection of the worms and post-rejection. Two additional control groups of uninfected calves (by anti-helminthic therapy of their mothers and after the birth) were also necropsied on days 30 and 50 after birth. Blood samples were fortnightly collected from birth to 174 days post-birth. Blood smears were prepared and stained with Giemsa for eosinophils. The parasitological status of buffalo calves was evaluated through weekly fecal egg counts (EPG) from 1 to 106 days after birth, which revealed that T. vitulorum egg shedding started on day 11, reached the peak of the infection on day 49 and finally expelled the parasites between days 50 and 85 after birth. In the infected buffalo calves, the mast cell population increased significantly, by two-fold in the mucosa (villus-crypt unit (VCU)) of the duodenum and four-fold in the proximal jejunum; but these increases were statistically significant only at the peak of the infection. Although mast cell numbers increased in the mucosa of the ileum as well as in both the submucosal and muscle tissues of the duodenum, proximal jejunum and ileum, the data was not significantly different from the controls. Eosinophil numbers increased in the mucosa of the duodenum (two-five times higher than the control) and proximal jejunum (three-five-fold) during the period of the infection (beginning, peak and rejection). The relative numbers of eosinophils increased in the blood stream from the second to the seventh week. In conclusion, T. vitulorum infection elicited mastocytosis and tissue eosinophilia in the duodenum and proximal jejunum, as well as eosinophilia in the blood stream, during the beginning, at the peak and during the rejection of the worm. After the rejection of the worms, the numbers of these cells returned to normal levels suggesting that these cells may have a role in the process of rejection of T. vitulorum by the host.

Superinfections with genetically characterized Trypanosoma cruzi clones did not aggravate morbidity and mortality in BALB/c mice.

To determine the role of Trypanosoma cruzi superinfections on the outcome of Chagas' disease, groups of BALB/c mice were prime-infected with low virulence clones h1 and h2 and challenged with high virulence clones m3 and m4. All mice injected with the m3 and m4 clones succumbed before or at 16 days postinfection. In contrast, all mice injected with the h1 and h2 clones survived the prime infection and were superinfected with the m3 and m4 clones. Low-level parasitemias were observed in mice after challenge with the virulent clones. The mortality ratios in the superinfected mice were not statistically different from those seen in the mice that received a single T. cruzi injection. The histopathological lesions recorded during the course of the infections showed features in the superinfected mice similar to those seen in the animals receiving a single infection. These data argue that morbidity and mortality in BALB/c mice, infected with T. cruzi clonal lines, are not associated with the frequency of receiving the parasite burden.

In vivo and in vitro experimental intestinal amebiasis in Mongolian gerbils (Meriones unguiculatus).

One of the main drawbacks of experimental amebiasis is the lack of an adequate animal model for invasive intestinal lesions. Mongolian gerbils are useful because both intestinal and hepatic amebiasis can be produced experimentally with Entamoeba histolytica trophozoites. In this paper we show results obtained with in vivo and in vitro models of intestinal amebiasis in gerbils. We inoculated gerbils intracecally with monoxenic cultures of a highly virulent E. histolytica HM1:IMSS substrain. In the in vivo model an increase in mucus production was observed during the first 6 h of interaction. Microulcerative mucosal lesions appeared at 24-72 h postinoculation. Inflammatory infiltrate and edema of the lamina propria were associated with superficial foci of necrosis. At 96 h the cecal mucosa had an almost normal appearance and live amebas were no longer detected. In the in vitro model, early damage was detected in cecal strips mounted in Ussing chambers as a rapid fall in potential difference, short-circuit current, and transepithelial resistance that correlated with the extent of the microscopic lesions produced. The latter consisted of cellular edema and the appearance of small, translucent vacuoles at the base of epithelial cells. Further damage led to loss of intercellular junctions, destruction of interglandular epithelial cells, and edema of the lamina propria. The present results demonstrate that the gerbil is useful as an experimental model for the analysis of early stages of invasive intestinal amebiasis both in vivo and in vitro.

Antigen-specific Il-4- and IL-10-secreting CD4+ lymphocytes increase in vivo susceptibility to Trypanosoma cruzi infection.

Control of macrophage parasiticidal function by treatment with recombinant cytokines or their neutralizing antibodies modifies the severity of experimental Trypanosoma cruzi infections. However, so far, no direct in vivo evidence has demonstrated changes in disease outcome after altering the initial ratios of parasite-specific IFN-gamma and IL-10/IL-4-secretor cells in secondary lymphoid organs. To this end, a population of predominantly CD4+ parasite-Ag-reactive, IL-4- and IL-10-secreting T lymphocytes derived from T. cruzi-immunized mice was adoptively transferred to naive recipients. Compared with cell responses from normal mice, spleen cells of uninfected recipients proliferated significantly to T. cruzi Ag and produced much greater amounts of IL-4 and IL-10; lower IFN-gamma levels and increased IL-4/IL-10 levels were induced by Con A stimulation. Recipient mice challenged with T. cruzi presented overwhelming tissue and blood parasitemia and early death, contrasting with typically resistant controls. Uninfected recipients did not exhibit tissue damage following cell transfer. No disease exacerbation occurred in recipients of OVA-reactive CD4+, IL-4/IL-10-secreting T lymphocytes stimulated with OVA at the start of infection. On Day 6 postinfection, not only spleen cells but also LN cells from infected recipients showed decreased production of IFN-gamma and augmented secretion of IL-4/IL-10 compared to cells from untransferred infected mice. The results indicate that an imbalance of Th cell populations leading to the predominance of secreted IL-4 and IL-10 at the start of infection and the concomitant down-regulation of IFN-gamma secretion reversed the host's resistance to T. cruzi. Moreover, transfer of anti-T. cruzi Th2-type cells most likely favored the in vivo expansion of parasite-specific host cells toward a Th2 phenotype.

Trypanosoma cruzi: aberrant expression of class II major histocompatibility complex molecules in skeletal and heart muscle cells of chronically infected mice.

In isolated skeletal, heart, and smooth muscle cells from BALB/c and C3H/HeJ mice infected with different strains of Trypanosoma cruzi the presence of class II MHC molecules was investigated by immunocytochemical techniques. We employed single muscle fibers instead of conventional cryostat sections to obtain a more accurate antigen localization. Approximately half of the skeletal muscle cells isolated from the rectus femoris expressed Ia antigens on their surface, irrespective of the mouse or parasite strain combination. Ia expression was apparent only at 30 days postinfection and thereafter. The heart muscle cells expressed class II molecules only at 1 and 3 months postinfection. In no case did the smooth muscle cells from infected mice express Ia antigens. Studies of the same molecules in the noninfected animals gave constantly negative results. We conclude that in the course of the chronic infection of mice with T. cruzi, ectopic expression of class II MHC molecules occurs at the surface of skeletal and heart muscle cells, providing a possible mechanism for explaining the anti-striped muscle autoreactivity present in Chagas' disease.

[Experimental intestinal amebiasis: invasion and extension of the amebic lesion]. / Amibiasis intestinal experimental: invasión y extensión de la lesión amibiana.

A morphological analysis of an experimental model of invasive intestinal amebiasis was carried out using the washed-closed cecal loop model in hamsters and guinea-pigs. By light microscopy, few amebic trophozoites adhered to the intestinal epithelium, whereas many associated to the mucus blanket. Some trophozoites attached to the interglandular epithelium, during the first 10 to 15 hours of interaction. Hereafter, the parasites destroyed gradually the epithelium and were associated with normal and lysed inflammatory cells. Some amebas have cell debris and erythrocytes in their cytoplasms. Typical amebic ulcer contained abundant trophozoites at the basolateral area. The results suggest that intestinal mucus and muscularis mucosa are temporal barriers to amebic invasion and extension of the ulcer. At the mucosal and submucosal levels, lysis of inflammatory cells produced by amebas seems to play an important role in the extension of the ulcer.

Leiomiócitos parasitados pelo Trypanosoma Cruzi nas formas congênita e crônica adquirida da doença de Chagas / Smooth muscle cells infected by Trypanosoma Cruzi in congenital and chronic acquired forms of Chagas disease

Os leiomiócitos parassitados pelo T. cruzi, de vasos umbilicais e placentários de casos congênitos da doença de Chagas, foram comparados com células semelhantes da veia suprarrenálica de chagásicos crônicos. Observou-se que algumas destas células, em ambos os grupos, apresentavam envoltório visto à microscopia de fase, nas preparaçöes näo coradas, e à microscopia de luz comum, quando coradas pelo PAS e pela HE. A prata-metenamina cora apenas o envoltório das células parasitadas dos casos de doença de Chagas congênita. A técnica do picro-sirius, associada à microscopia de luz polarizada, mostra que ambos os grupos de leiomiócitos parasitados podem apresentar delicada membrana com birrefrigência discreta "verde limäo", enquanto que un envoltório espesso com forte birrefrigência amarelada ou brancacente é visto apenas nos leiomiócitos fetais. A técnica da peroxidase anti-peroxidase cpara T. cruzi mostra acúmulo de material PAP-positivo formando uma faixa interrompida que se coloca mais internamente à faixa PAS-positivo, em ambas as formas da doença. As modificaçöes nucleares e citoplasmáticas das células fetais parasitadas (Chagas congênito) e dos adultos (chagásicos crônicos) säo muito semelhantes, destacando-se o gigantismo nuclear, o aparecimento de grânulos algumas vezes PAP-positivo, e a desproporçäo entre o aumento do volume celular e o número de parasitas. É possível que o estado de imunodeficiência, localizado na glândula suprarrenal do adulto e o tecido fetal tenham algum papel na gênese dessa peculiaridade das células parasitadas, comuns na doença de Chagas congênita e na forma crônica adquirida