Biomedical Engineering Reference
In-Depth Information
$10.5/1 to $2/1 (e.g. 10 e 2% serum in the medium), the cost of the CHO cell product would
drop to $6500/g.
A primary lesson from this exercise is the difficulty of making choices of host e vector
systems without a fairly complete analysis. The price will depend on the protein, its charac-
teristics, and intended use. Changes in process technology (e.g. low serum medium for CHO
cells or protein secretion systems in E. coli ) can have dramatic effects on manufacturing costs
and choice of the host e vector system.
14.8. RE GULATORY CONSTRAINTS ON GENETIC PRO CESSES
When genetic engineering was first introduced, there was a great deal of concern over
whether the release of genetically modified cells could have undesirable ecological
consequences.
Reports in the popular press led to fears of “genetic monsters” growing in our sewers, on
our farmlands, or elsewhere. Consequently, the use of genetic engineering technology is
strictly regulated. The degree of regulatory constraint varies with the nature of the host,
vector, and target protein. For example, consider a scenario where serious harm might arise.
The gene for a highly toxic protein is cloned into E. coli to obtain enough protein to study that
protein's biochemistry. Assume that a plasmid that is promiscuous (i.e. the plasmid will
shuttle across species lines) is used. Also assume that laboratory hygiene is not adequate
and a small flying insect enters the laboratory and comes into contact with a colony on a plate
awaiting destruction. If that insect leaves the laboratory and returns to its natural habitat,
then the target gene is accidentally released into the environment. Laboratory strains of
E. coli are fragile and usually will not survive long in a natural environment. However,
a very small probability exists that the plasmid could cross over species lines and become
incorporated into a more hardy soil bacterium (e.g. Pseudomonas sp.). The plasmid would
most certainly contain antibiotic-resistance factors as well. The newly transformed soil bacte-
rium could replicate. Many soil bacteria are opportunistic pathogens. If they enter the body
through a wound, they can multiply and cause an infection. If, in addition, the bacterium
makes a toxic protein, the person or animal that was infected could die from the toxic protein
before the infection was controlled. If the plasmid also confers antibiotic resistance, the infec-
tion would not respond to treatment by the corresponding antibiotic, further complicating
control of the spread of the gene for the toxin.
This scenario requires that several highly improbable events occur. No case of significant
harm to humans or the environment due to the release of genetically modified cells has been
documented. However, the potential for harm is real. Cell recombination can also occur natu-
rally
14.3 when chance presents. For example, the discovery of NDM-1 (New Delhi metallo-
beta-lactamase 1) that dubbed as “superbug” has made headlines in 2010. The NDM-1 is
a gene that produces an enzyme that deactivates basically all antibiotics. The drug resistance
gene NDM-1 can pass from one kind of bacteria to another.
Regulations controlling genetic engineering concentrate on preventing the accidental
release of genetically engineered organisms. The deliberate release of genetically engineered
cells is possible, but an elaborate procedure must be followed to obtain permission for such
experiments.
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