Influence of host cell line and microsporidian species in the in vitro infection efficiency of Encephalitozoon spp.

Microsporidia are obligate intracellular eukaryotes infecting a wide range of hosts and cell types. The development of in vitro culture models is essential for studying host-parasite interactions and the pathogenesis of microsporidian infections. In this study, we compared the infection efficiency of three human pathogenic species of the genus Encephalitozoon (Encephalitozoon intestinalis, E. hellem, and E. cuniculi) across six cell lines: TC7, HT-29, HCT 116, T84, Vero, and MRC-5. Infection rates and the surface area of parasitic foci were determined after labeling microsporidia by fluorescence in situ hybridization (FISH). Both parameters varied significantly according to the cell line and Encephalitozoon species. TC7 cells consistently supported the highest infection rates, whereas HCT 116 cells were the least permissive. The surface areas of foci were primarily species-dependent, with larger foci observed for E. cuniculi and smaller ones for E. intestinalis. In conclusion, these results revealed marked differences in invasive and proliferative dynamics depending on the Encephalitozoon species and cell line and highlight the crucial impact of cell line selection on in vitro experimental outcomes. This work provides a foundation for improving and standardizing experimental models for future experiments on Encephalitozoon spp.