Abstract
Bombyx mori cultured cell line NIAS-Bm-Ke1 (Ke1 cells) that adjusted to serum-free medium was established. Ke1 cells showed moderate cell growth in serum-free media, but the cells showed low susceptibility to infection with BmPTLNPV, a recombinant BmNPV expressing the luciferase gene. Addition of heat-treated silkworm hemolymph in serum-free medium led to enhance the susceptibility of Ke1 cells to BmPTLNPV infection. By infection with a hybrid baculovirus, which is infectious to both Ke1 and Sf9 cells and encodes the luciferase gene, Ke1 cells cultured in KBM700 serum-free medium containing heat-treated silkworm hemolymph showed higher luciferase activity than Sf9 cells cultured in SF900II serum-free medium containing 10% of FBS. Ke1 cells were adaptable to suspension culture using KBM700 serum-free media. Luciferase gene expression by BmPTLNPV infection was observed in the cells cultured in KBM700 serum-free medium without heat-treated silkworm hemolymph only if the infected cells were cultured in the medium containing heat-treated silkworm hemolymph for a certain period just after infection. Based on these results, we concluded that Ke1 cells are suitable for the expression of recombinant protein in the baculovirus gene expression system.
