Large-scale transient expression from mammalian cells is a new technology.
Breakthroughs have been achieved for non-viral delivery methods: transfecti
ons can now be done at the 1-10 L scale with mammalian cells grown in suspe
nsion. Production of 1-20 mg/L of recombinant protein have been obtained in
stirred bioreactors. Modified alphaviruses have provided a fast and effici
ent expression technology based on viral vectors.