Infection and development of vairimorpha sp. NIS M12(microsporida: Protozoa) in a lepidopteran cell line

Vairimorpha sp. NIS M12, a microsporidian parasite isolated from the silkworm, Bombyx mori, successfully infected the cell line of Spodoptera frugiperda SF21AE II. After priming with 0.1N KOH solution, the spores were mixed thoroughly with S. frugiperda cells suspended in Rinaldini's solution. Inoculated cells were cultured at 28°C in IPL-41 medium supplemented with 10% fetal bovine serum. At a ratio of 30 spores per cell, 9.1% of S. frugiperda cells were infected initially with sporoplasms 1hr postinoculation. About 65% of the infected cells harbored a single sporoplasm. The spread of infection and spore production of V. sp. NIS M12 in cell cultures were markedly different from those of Nosema bombycis, while the in vitro life cycles of the two parasites was similar. Short-coiled spores occurred 72hr postinoculation, and longcoiled mature spores were produced 10 days postinoculation. No formation of syncytia was observed in Vairimorpha infected cell cultures.