Infection and long-term cultivation of the microsporidium Nosema bombycis in Sf9 insect cell culture

Abstract

The microsporidium Nosema bombycis is economically important as a causative agent of silkworm pebrine, and also as a potential biological control agent for lepidopteran pests such as Dendrolimus sibiricus. In this study, N. bombycis spores were isolated from diseased Bombyx mori larvae. After artificial stimulation in 0.1 M KOH, they were inoculated into the Sf9 cell line to initiate continuous proliferation of the parasite. After 7 days of initial infection, fresh Sf9 cells were added, establishing a long-term persistently infected culture. We quantified the percentage of infected cells and the dynamics of spore accumulation during primary infection and long-term cultivation, and determined the limits of cell survival and infectivity in the infected culture. Our studies enabled us to propose key parameters for utilizing this host-parasite system as a model for studying nosematosis and resistance mechanisms, as well as for the mass-production of spores for plant protection.