Resistance to Encephalitozoon intestinalis is associated with interferon-gamma and interleukin-2 cytokines in infected mice.

The understanding of the immunopathology of infections caused by microsporidia has pinpointed the importance of T cell-mediated immunity. The immunopathology caused by the interesting protozoan parasite Encephalitozoon intestinalis, a microsporidium pathogenic in man, is not clearly understood. In this study, we demonstrate that a specific cellular immune response is implicated in the control of microsporidiosis infection in mice. Interferon (IFN)-gamma receptor knockout mice (IFN-gamma R(o/o)) developed a chronic infection with E. intestinalis, whereas a transient infection developed in wild-type mice. Encephalitozoon intestinalis proteins induced proliferation of murine spleen and mesenteric lymph node cells collected from infected mice. The host response to microsporidia infection was regulated by a specific pattern of cytokine protection. Spleen cells derived from resistant 129 Sv/Ev mice inoculated with E. intestinalis secreted significant levels of gamma-interferon and interleukin-2 but cells from highly susceptible IFN-gamma R knockout mice secreted high levels of interleukin-4 (mostly between 2 and 4 weeks post infection). This is the first report in which a specific cellular immune response against E. intestinalis infection is presented.

A new developmentally regulated gene family in Leishmania amastigotes encoding a homolog of amastin surface proteins.

The ability of Leishmania to survive within the phagolysosomes of mammalian macrophages is heavily dependent on the developmental regulation of a number of genes. Characterization of genes preferentially expressed during the parasite's intracellular growth would help to elucidate the mechanisms controlling stage-specific gene regulation and the intracellular life of the parasite in general. Using a genomic approach based on the differential hybridization screening of high-density filters, we have identified a new developmentally regulated gene in Leishmania, which is part of a multigene family and encodes a highly hydrophobic protein that shares homology with the Trypanosoma cruzi amastin proteins. The fusion of the Leishmania amastin gene homolog with the green fluorescent protein and analysis by confocal microscopy suggested a surface localization for this protein. The amastin gene homolog is expressed predominantly in the amastigote form of several Leishmania species and is strictly regulated by acidic pH at the post-transcriptional level. Its developmental expression involves sequences within the 3'-untranslated region.

Encephalitozoon intestinalis: humoral responses in interferon-gamma receptor knockout mice infected with a microsporidium pathogenic in AIDS patients.

IFN-gamma receptor knockout mice and wild-type mice were infected per os with Encephalitozoon intestinalis. Both groups developed an infection that was chronic in the mutant mice whereas it was only transient in wild-type mice. The infection of mutant mice was characterized by the continual shedding of spores in feces, splenomegaly, the enlargement of the biliary tract, and the occurrence of numerous nodules in the liver and in the small intestine wall. The humoral response was studied by ELISA, IFA, and Western blotting. ELISA titers of anti-E. intestinalis antibodies of IgG, IgM, and IgA isotypes were higher in IFN-gamma R0/0 mice than in wild-type mice and they increased in time after infection. Levels of IgG2a were inferior to those of IgG1 in mutant mice in contrast to wild-type mice. High levels of parasite specific antibodies were accompanied by an increase in type 2 cytokines (IL-4 and IL-10) secretion in the duodenum of IFN-gamma R0/0 mice. The E. intestinalis spore wall was recognized by IgM, IgG, and IgA from all infected mice whereas the extruded polar tube only reacted with IgG and IgA from IFN-gamma R0/0 mice after 45 days of the infection. IFN-gamma R0/0 mice IgG and IgA reacting with polar tube identified also a series of proteins which could be components of this structure. On the proteins recognized by all infected mice sera, two were first recognized by IgM at day 15 and then by IgG at day 30 in wild-type (WT) mice. The persistent reactivity of all proteins in mutant mice is consistent with the chronicity of the infection in these animals; in contrast, their resorption at day 30 in WT animals corroborates the transient character of the infection in these mice. The correlation between the evolution of the proteic pattern and the development of the infection provides evidence of the validity of this murine model to study human microsporidiosis. Indeed the reported results confirm the potential value of serological methods for diagnosing E. intestinalis infection in immunocompetent and in immunocompromised human subjects, for elucidating the age pattern of the microsporidiosis and also for identifying risk groups.

[Human intestinal microsporidiosis in Bamako (Mali): the presence of Enterocytozoon bieneusi in HIV seropositive patients]. / Microsporidiose intestinale humaine à Bamako (Mali): présence d'Enterocytozoon bieneusi chez les patients séropositifs pour le VIH.

A study was conducted between 1993 and 1996 in Bamako to determine the rate of occurrence of microsporidia in 88 patients. Most (80%) had chronic diarrhea associated with weight loss and 87.5% were HIV-positive. Intestinal microsporidia were detected in 32% of the patients infected with HIV-1, HIV-2, or coinfected with both strains. Microsporidiosis was also diagnosed in three of the eleven HIV-negative individuals (27%). Microsporidiosis was confirmed by electron microscopy in 6 HIV-positive patients and 1 HIV-negative individual. Enterocytozoon bieneusi was detected in each case. These results suggest that microsporidia are common pathogens in HIV-positive patients in Bamako. Cases of microsporidiosis have been reported for the first time in HIV-2-infected patients. The proportion of women microsporidiosis patients is higher in Mali than in industrialized countries. The presence of microsporidia in HIV-negative patients suggests that these parasites may be an underestimated cause of enteritis in developing countries.