Infection and development of Nosema mesnili NM-HC-A8801 (Microsporida: Protozoa) in lepidopteran cell line

Spores of Nosema mesnili NM-HC-A8801 primed with 0.1-N KOH solution were inoculated in Antheraea eucalypti cell cultures at a ratio of 30 spores per cell. The inoculated insect cells were cultured at 27°C in GRACE'S medium supplemented with 10% fetal bovine serum. At 1 h post-inoculation, the percentage of hatched spores was approximately 20%, and about 5% of A. eucalypti cells were infected initially with sporoplasms. At 96 h post-inoculation, many-coiled mature spores were produced and an infected A. eucalypti cell contained about 40 protozoans. A rapid increase in cell infection rates was observed and the percentage of infected cells reached 90% 120 h post-inoculation. In the life cycle, N. mesnili NM-HC-A8801 was diplokaryotic and showed disporous development which are typical of the genus Nosema. However, the spread of infection and spore production were markedly different from N. bombycis and Nosema sp. NIS M11.