During Plasmodium falciparum infection leading to cerebral malaria, cytokine production and cytoadherence of parasitized erythrocytes (PRBCs) to postcapillary venules are involved. We demonstrate ...that PRBC adhesion induces apoptosis in human endothelial cells (HLECs). PRBC adhesion modulated HLEC gene expression in tumor necrosis factor-α superfamily genes (Fas, Fas L and DR-6) and apoptosis-related genes (Bad, Bax, caspase-3,SARP 2, DFF45/ICAD, IFN-γ receptor 2, Bcl-w, Bik, and iNOS). Apoptosis was confirmed by (1) morphological modifications by electron microscopy, (2) annexin V binding, (3) DNA degradation, by measuring intracytoplasmic nucleosomes, and (4) caspase activity. The apoptotic stimulus was physical contact between HLECs and PRBCs and not parasite-secreted molecules. In addition, it was found that cytoplasmic (caspase 8) and mitochondrial (caspase 9) pathways were involved in this process. These data not only describe the direct apoptotic effect of PRBC adhesion on endothelial cells but also provide new useful tools that allow an evaluation of potential pharmaceuticals
The antiparasitic effect of a collection of compounds with antimitotic activity has been tested on a mammalian cell line infected with Encephalitozoon intestinalis, a microsporidian causing ...intestinal and systemic infection in immunocompromised patients. The antiparasitic effect was evaluated by counting the number of parasitophorous vacuoles detected by immunofluorescence. Out of 526 compounds tested, 2 (pancratistatin and 7-deoxynarciclasine) inhibited the infection without affecting the host cell. The 50% inhibitory concentrations (IC(50)s) of pancratistatin and 7-deoxynarciclasine for E. intestinalis were 0.18 microM and 0.2 microM, respectively, approximately eightfold lower than the IC(50)s of these same compounds against the host cells. Electron microscopy confirmed the gradual decrease in the number of parasitophorous vacuoles and showed that of the two life cycle phases, sporogony was more sensitive to the inhibitors than merogony. Furthermore, the persistence of meronts in some cells apparently devoid of sporonts and spores indicated that the inhibitors block development rather than entry of the parasite into the host cell. The occurrence of binucleate sporoblasts and spores suggests that these inhibitors blocked a specific phase of cell division.
Enterocytozoon bieneusi is a major cause of chronic diarrhea and malabsorption in patients with AIDS. We report what we believe is the first case of intestinal infection due to E. bieneusi in a ...heart-lung transplant recipient who was seronegative for human immunodeficiency virus (HIV). The clinical presentation and the evolution of the disease were identical to those usually observed in patients with AIDS and included diarrhea, massive weight loss, and persistent infection despite treatment with albendazole. E. bieneusi was identified in the patient's duodenal mucosaby electron microscopy. No other etiologic agent was detected. We conclude that E. bieneusi may be responsible for serious intestinal infections in patients whose immunosuppression is not related to HIV.
Microsporidia are unicellular and obligate intracellular spore-forming parasites. The spore inoculates the host cell with its non-motile infectious content, the sporoplasm, by way of the polar ...tube–the typical invasive apparatus of the microsporidian spore. Molecules involved in host cell invasion were investigated in Encephalitozoon intestinalis. Mouse polyclonal and monoclonal antibodies were raised against spore proteins and their reactivity was tested by Western-blotting and immunolocalization techniques, including electron and confocal microscopy. The antibodies thus generated could be divided into two major groups. One group reacted to the surface of the parasite at different developmental stages, mostly presporous stages and mature spores, whereas the other group recognized the polar tube. Of the antibodies reacting to the spore wall, one identified an exospore protein at 125 kDa while all others recognized a major doublet at 55–60 kDa, and minor proteins present at the surface of sporogonic stages and in the endospore. All antibodies recognizing spore wall proteins reacted also to the material forming septa in the parasitophorous vacuole. A major polar tube protein at 60 kDa was identified by another group of antibodies.
SUMMARY
The ultrastructural study of the invasion of cells (THP1 AND RK13) by E. intestinalis shown that infective stages enter host cells via a phagocytic process intitiated at the contact of the ...apical part of spores with host cell membrane. The polar tube is extruded within an invagination of the host cell membrane that extends inside a pseudopod containing microfilaments. These observations suggest that microsporidia as well as other intracellular pathogens can induce host cell alterations facilitating the invasio.
Microsporidia are a group of obligate intracellular protistan parasites that have recently gained recognition as opportunistic infections in persons with AIDS or in those who are otherwise ...immunocompromised. To date, eight genera have been identified as human pathogens, Encephalitozoon, Enterocytozoon, Nosema, Vittaforma, Pleistophora, Trachipleistophora, Brachiola, and the collective genus Microsporidium. A frequent causative agent of microsporidial diarrhea and systemic infection among AIDS patients is Encephalitozoon intestinalis. This parasite can also cause chronic diarrhea in immunocompetent persons. However, many epidemiologic aspects of this infection remain poorly understood as the diagnostic tools for this parasite are not amenable to widespread use. In an attempt to improve this situation, we have developed an ELISA test to detect human serum antibodies reactive with Encephalitozoon intestinalis.
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