Agriculture Reference
In-Depth Information
function depending whether it is expressed in microbes, mammals, or
plants. Bacteria for instance, do not add certain sugar residues (glycosy-
lation) and might not be able to correctly process some human glycol-
proteins.
8
Product safety is another reason frequently reiterated by industry, as
PMPs are claimed to be free of contaminating human or animal viruses,
which is a concern in case of production from mammalian cell lines.
9
Although a presence of such viruses in mammalian cell lines might pose
risks to human health, plant viruses are not known to infect humans.
Potential savings in production costs have been strongly empha-
sized,
10
although industry has more become less optimistic in recent
years. In fact the agricultural production of plant biomass that includes
the target protein is likely to be much cheaper compared to conventional
production with microbes and mammalian cells in high-tech facilities.
According to earlier and very optimistic estimates, recombinant proteins
could be produced in plants at 2 to 10 percent of the cost of microbial
fermentation systems and at 0.1 percent of the cost of mammalian cell
cultures, although this depends on the product yield.
11
Cut down in costs
would, however, only affect the production of the crude protein, whereas
the purification of the protein and formulation of the biopharmaceutical
in subsequent downstream processing amounts to 50 to 80 percent of the
total production costs.
The preclinical and clinical trials of new biopharmaceuticals are
already long-term, very expensive procedures required by pharmaceu-
tical legislation. Higher compliance costs have to be anticipated for
approval of PMPs compared to conventional biopharmaceuticals under
8
R. Twyman et al., Molecular Farming in Plants: Host Systems and Expression Tech-
nology, 21
Trends in Biotechnology
570-578 (2003).
9
U. Commandeur et al., The Biosafety of Molecular Farming in Plants. 5
AgBiotechNet
1-9 (2003).
10
J. H. Seon & M. M. Moloney, A Unique Strategy for Recovering Recombinant Pro-
teins from Molecular Farming: Affinity Capture on Engineered Oil Bodies, 4
Journal
of Plant Biotechnology
95-101 (2002).
11
G. Giddings, Transgenic Plants as Protein Factories. 12
Current Opinions in Biotech-
nology
450-454 (2001).
