title: Effect of Peptone Feeding on Transient Gene Expression Process in CHO DG44.
abstract: BACKGROUND
  Transient Gene Expression (TGE) gained popularity over the last decade as a rapid method for the production of milligram to gram quantities of recombinant proteins for preclinical studies in biophama industry. Thereby, the optimization of the TGE technique for Chinese hamster ovary (CHO) as the dominant host for the production of biotherapeutics is of great interest to reach the values for Human Embryo Kidney-293 (HEK-293) cells in terms of transfection efficiencies and production titers. TGE efficiencies are cell line and vector dependant.
  
  
  METHODS
  In transfection efficiency optimization experiments, different starting cell densities, different amounts of plasmid DNA and PEI transfection reagent were investigated to achieve the best conditions leading to maximum transfection efficiencies. Furthermore, in order to investigate the effect of peptone feeding on transfection efficiency, three different sources of peptones with the greatest effect in the CD DG44 basal media were selected; Casein Tryptone N1, Soy petone A2SC and Soy peptone E110.
  
  
  RESULTS
  The transfection strategy performed here was able to make an outstanding increase in transfection efficiency of CHO DG44 cell line transfected with pTracer-SV40-mutated t-PA plasmid from 3.6% in our starting non-optimized condition to 66.93% in finally optimized situation. Moreover, peptone feeding strategy used here was successful to increase volumetric productivities up to 37%. In addition, the amounts of both PEI and plasmid DNA were reduced up to 66% and 25%, respectively compared to our previous protocol.
  
  
  CONCLUSIONS
  Here we described an optimization process for TGE in suspension-adapted CHO cells based on Polyethylenimine (PEI)/DNA concentration, DNA: PEI ratio, starting cell densities and peptone feeding strategy.
authors.affiliation: Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Davami
authors.affiliation: Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran ; Islamic Azad University of Arak, Arak, Iran.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Eghbalpour
authors.affiliation: Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Barkhordari
authors.affiliation: Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: Fereidoun
authors.initials: F
authors.lastname: Mahboudi
keywords: Chinese hamster ovary cells; Peptones; Polyethylenimine; Protein production; Transient gene expression