Rabies virus glycoprotein expression in Drosophila S2 cells: Influence of re-selection on protein expression

The aim of this study was to achieve expression of recombinant rabies virus glycoprotein (rRVGP) in Drosophila S2 cells. For this, a cDNA coding for the selection hygromycin antibiotic and the cDNA encoding the RVGP protein under the control of the constitutive actin promoter (Ac) were cloned in an expression plasmid, which was transfected into S2 cells. S2 cell populations (S2AcRVGPHy) showed rRVGP expression in cell lysates, attaining concentrations up to 1.5 μg/10⁷ cells (705 μg/L). Of the transfected cells, 20% were shown to express the rRVGP. Cell subpopulations selected by limiting dilution expressed higher rRVGP yields and 90% of the cells were shown to express the rRVGP. Cell populations re-selected by addition of hygromycin were shown to express 10 times higher rRVGP yields. The data presented here show that Drosophila S2 cells can be efficiently transfected with an expression/selection plasmid for rRVGP expression, allowing its synthesis with a high degree of physical and biological integrity. The importance of subpopulation selection was indicated by the increasing rRVGP yields during these procedures.