Kinetic studies of recombinant rabies virus glycoprotein (RVGP) cDNA transcription and mRNA translation in Drosophila melanogaster S2 cell populations

Abstract

Recombinant rabies virus glycoprotein (RVGP) was expressed in cell membranes of stably transfected Drosophila S2 cells using constitutive and inducible promoters. Although with quantitative differences of RVGP expression in both systems, the cDNA transcription, as evaluated by relative RVGP mRNA levels measured by qRT-PCR, sustained the amount of RVGP producing cells and the RVGP volumetric (ΠRVGP) productivity. At the transition to the stationary cell growth phase, once the cell culture slowed down its rate of multiplication, an accumulation of RVGP mRNA and RVGP was clearly observed in both cell populations. Nevertheless, cell cultures performed under sub-optimal temperatures indicated that an envisaged increase in the RVGP production is not only dependent on cell growth rate, but essentially on optimal cell metabolic state.

Fig. 1

Kinetics of S2AcRVGP-2k cell growth and RVGP mRNA (a) and RVGP expression (b). Suspension cell cultures were performed at 28 °C. lnX natural logarithm of cell concentration (filled circle), RVGP mRNA relative RVGP mRNA (fold difference) compared to time 0 h (grey columns), μ calculated by the regression line of lnX dots corresponding to cell growth phase, П _RVGP RVGP volumetric productivity (filled triangle), % of RVGP producer cells anti-RVGP-FITC labeled cells measured by flow cytometry (white columns), P _c RVGP cell content measured by ELISA (filled square). Data shown are the average of 3 different experiments. * Statistically different from the preceding values (P < 0.05)

Fig. 2

Kinetics of S2MtRVGP-Hy cell growth and RVGP mRNA (a) and RVGP expression (b) upon CuSO₄ induction at culture onset. Suspension cell cultures were performed at 28 °C. lnX natural logarithm of cellular concentration (filled circle), RVGP mRNA relative RVGP mRNA (fold difference) compared to time 0 h (grey columns), μ calculated by the regression line corresponding to growth phase, П _RVGP RVGP volumetric productivity (filled triangle), % of RVGP producer cells anti-RVGP-FITC labeled cells measured by flow cytometry (white columns), P _c RVGP cell content measured by ELISA (filled square). Data shown are the average of 3 different experiments. * Statistically different from the preceding values (P < 0.05)