Studies on serum-free culture of insect cells for virus propagation and recombinant protein production

Abstract

Three lepidopteran cell lines, Spodoptera frugiperda cell line IPLB-Sf-21 and its clonal isolate Sf9 and the Trichoplusia ni cell line TN368, were adapted to a serum-free medium, EX-CELL 400. The cell growth kinetics of the serum-free cultures in monolayer were compared with that of serum-containing cultures. Virus production and recombinant protein production with a baculovirus expression vector in serum-free cultures were evaluated in comparison with those in serum-containing cultures. The production of both polyhedra and extracellular virus in both types of media was not significantly different. The production of β-galactosidase as a recombinant protein in the serum-free cultures was not as high as that in serum-containing cultures. Electron microscopical studies showed that virus replication and polyhedra formation in serum-free cultures were very similar to those in serum-containing cultures. The larval infectivity of polyhedra produced in the three cell lines grown in EX-CELL 400 medium did not differ from each other. In contrast, the infectivity of polyhedra produced in serum-containing cultures differed for the three cell lines and polyhedra from IPLB-SF-21 cells showed the highest infectivity.