No abstract

Background: Encephalitozoon hellem (E. hellem) 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 E. hellem infection. Methods: Wild-type C57BL/6 mice were immunosuppressed with dexamethasone (Dex) and then E. hellem 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 E. hellem inoculation resulted in a disseminated nonlethal infection. Interestingly, E. hellem infection desensitized the innate immunity of the host, as shown by cytokine expressions and dendritic cell maturation. We also found that E. hellem 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.

Microsporidia are a group of spore-forming, fungus-related pathogens that can infect both invertebrates and vertebrates including humans. The primary infection site is usually digestive tract, but systemic infections occur as well and cause damages to organs such as lung, brain, and liver. The systemic spread of microsporidia may be intravascular, requiring attachment and colonization in the presence of shear stress. Von Willebrand Factor (VWF) is a large multimeric intravascular protein and the key attachment sites for platelets and coagulation factors. Here in this study, we investigated the interactions between VWF and microsporidia Encephalitozoon hellem (E. hellem), and the modulating effects on E. hellem after VWF binding. Microfluidic assays showed that E. hellem binds to ultra-large VWF strings under shear stress. In vitro germination assay and infection assay proved that E. hellem significantly increased the rates of germination and infection, and these effects would be reversed by VWF blocking antibody. Mass spectrometry analysis further revealed that VWF-incubation altered various aspects of E. hellem including metabolic activity, levels of structural molecules, and protein maturation. Our findings demonstrated that VWF can bind microsporidia in circulation, and modulate its pathogenicity, including promoting germination and infection rate. VWF facilitates microsporidia intravascular spreading and systemic infection.

[Background] Co-infection of multiple pathogens into one host is a great threat to public health, for it exacerbates symptoms and leads to worse outcomes compared to single pathogen infection. Both Mycobacterium tuberculosis (Mtb) and microsporidia are wide spread pathogens world-widely. However, the co-infection of Mycobacterium tuberculosis with microsporidia has long been underestimated. [Methods] Current study recruited Mtb-positive pulmonary patients and Mtb-negative patients yet immune-suppressed due to various causes. Stool samples were collected from these two groups of individuals and the total DNAs were isolated. Quantitative PCR (qPCR) assay was used to detect the presence of microsporidia in these samples. [Results] The results showed that infection rates of microsporidia are 39.6% (23/58) in Mtb-positive group and 50% (4/8) in Mtb-negative yet immune-suppressed group. Sequencing of the positive further revealed that the infected microsporidia species include all four common human-infecting microsporidia which are Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon cuniculi and Encephalitozoon hellem. [Conclusion] Our report is the first to investigate and compare the influences of Mtb-infection and host immune state in microsporidia infection. Our findings demonstrated that microsporidia have high co-infection incidence with Mtb, and the host immune state has profound influence on infection of microsporidia. [Trial Registration] N/A.