| Summary: | Background: <i>Encephalitozoon hellem</i> (<i>E. hellem</i>) belongs to a group of opportunistic pathogens called microsporidia. Microsporidia infection symptoms vary and include diarrhea, ocular disorders and systemic inflammations. Traditionally, immunodeficient animals were used to study microsporidia infection. To overcome the difficulties in maintenance and operation using immunodeficient mice, and to better mimic natural occurring microsporidia infection, this study aims to develop a pharmacologically immunosuppressed murine model of <i>E. hellem</i> infection. Methods: Wild-type C57BL/6 mice were immunosuppressed with dexamethasone (Dex) and then <i>E. hellem</i> spores were inoculated into the mice intraperitoneally. Control groups were the Dex-immunosuppressed but noninoculated mice, and the Dex-immunosuppressed then lipopolysaccharide (LPS)-treated mice. Mice body weights were monitored and all animals were sacrificed at the 15th day after inoculation. Tissue fragments and immune cells were collected and processed. Results: Histopathological analysis demonstrated that <i>E. hellem</i> inoculation resulted in a disseminated nonlethal infection. Interestingly, <i>E. hellem</i> infection desensitized the innate immunity of the host, as shown by cytokine expressions and dendritic cell maturation. We also found that <i>E. hellem</i> infection greatly altered the composition of host gut microbiota. Conclusions: Dex-immunosuppressed mice provide a useful tool for study microsporidiosis and the interactions between microsporidia and host immunity.
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