In Vitro Cultivation for Glugea plecoglossi (Microsporidia) Isolated from Ayu ( Plecoglossus altivelis ).

Glugea plecoglossi is an obligate intracellular microsporidium, which poses a significant threat to ayu ( Plecoglossus altivelis ). In vitro cultivation models are invaluable tools for investigating intracellular microorganisms, including G. plecoglossil . In this study, we attempted to in vitro cultivate G. plecoglossi using primary cultures derived from ayu monocytes/macrophages (MO/MΦ), a murine-derived macrophage cell line RAW264.7, and the epithelioma papulosum cyprini (EPC) cell line. The results demonstrated that MO/MΦ infected with spores exhibited a pronounced immune response which was presented by rapidly high expression levels of inflammatory cytokines, such as PaIL-1β , PaTNF-α , PaIL-10 , and PaTGF-β , and detached within 96 h post-infection (hpi). Infected RAW264.7 cells remained capable of stable passage yet exhibited cellular deformation with a decrease in intracellular spores occurring around 8 days post-infection (dpi). In contrast, EPC cells promised a substantial parasite population, and the cytokine expression levels returned to normal by 8 dpi. In addition, G. plecoglossi spores recovered from EPC cells could infect young ayu, suggesting that EPC cells might be used as an in vitro cultivation system for G. plecoglossi .