Page 159 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioTechnology

P1: GRB/GUB P2: FYD Final Pages
Encyclopedia of Physical Science and Technology EN009G-399 July 6, 2001 20:4

44 Mammalian Cell Culture

The use of mammalian host systems for the production of very short half-lives and make only single-dose treatment
pharmaceutically relevant products has been discussed, at possible. The field has moved on to the use of adoptive
timesquitecontroversially,byregulatorycontrolagencies, immunotherapy, where the patient’s cells are altered and
academic institutions, and private companies. In all these grown in vitro and perfused back into the patient. Many
discussions, the transfer to patients of agents (globally re- novel products have been developed—for example, the
ferred to as “adventitious” agents) has been the reason for CD-4 receptor, which is a combination of the genes cod-
concern. The three main types of agents are viruses, DNA- ing for the soluble form of the CD-4 receptor with the gene
containing oncogenes, and any other pathogenic activity sequence for IgG molecules which results in a soluble re-
and contaminating proteins that may give rise to immune ceptor for HIV.
reactions or any other adverse reaction. In fact, some of the
early experiences, especially with primary cells, resulted
in the transfer of viruses of known or unknown origin to C. Immunoregulators
human patients (e.g., SV40 virus in polio vaccines). The The production of alpha-interferon in Namalwa cells by
sophistication of modern purification techniques and the Wellcome was the first licenced use of a cancer cell sub-
accuracy of assay measurements at the picogram level al- strate for a human biological. The unrestricted growth
low substates to be used that were considered a hazard 15 in suspension culture of these cells allowed the first
years ago, as quality control emphasis is now on the purity multithousand-Liter (8000 L) unit process to be developed
of the final product. for human products. The knowledge gained from produc-
ing FMDV vaccine in suspension BHK cells was of great
benefit in developing this process. A wide range of both
V. CELL PRODUCTS
interferons and interleukins occurs naturally, and to date
both alpha- and gamma-interferons and interleukins 2, 3,
A. Viral Vaccines
4, 6, 11, and 12 have been manufactured in culture.
The first cell-based vaccine was for polio and was pro-
duced in monkey kidney cells. A series of HDC vac- D. Recombinant Products
cines were licenced during the 1960s. The first recom-
The fact that cells with specialized in vivo functions, such
binant vaccine was against hepatitis B and currently the
as endocrine cells secreting hormones, could not be grown
primary target is human immunodeficiency virus (HIV).
and replicated in culture with retention of their special-
Other viral diseases with trial vaccines are hetres simplex
ized properties has always been a great disappointment,
virus (HSV), rous sorcoma virus (RSV), cytomegalovirus
not only for advancing medical studies but also for using
(CMV), influenza, and rotavirus. The vaccine field has ex-
cells to manufacture naturally occurring biologicals. Thus,
panded from the area of infectious diseases to include can-
genetic engineering techniques that allow the gene(s) re-
cer (particularly melanoma, also breast, colorectal, ovar-
sponsibleforproductionofrequiredbiologicalsinahighly
ian, and B-cell cancers), rheumatoid arthritis, multiple
sclerosis, and contraception. The vaccine itself is showing differentiated (nonculturable) cell to be inserted into a
a dynamic evolution from the original whole virus (dead fast-growing robust cell line have opened up numerous
or attenuated), through subunits (native and recombinant), possibilities for exploitation by animal cell technology
genetically deleted viruses, to the future aim of DNA vac- (Table I).
cines and mucosal immunity. The emerging pharmaceutical biotech-industry realized
in the mid-1980s that the expression capacity of microbial
systems, and in particular of Escherichia coli, was limited
B. Antibodies
when the protein of interest required a complex folding
The production of monoclonal antibodies, first at the re- with multiple disulfide bridges and secondary modifica-
search level and then for diagnostics (including in vivo tions such as glycosilation, fucosilation, or other post-
imaging) from the mid-1980s gave a huge impetus to in- translational processing. Simply, the majority of some-
dustrial animal cell biotechnology. The use of monoclonal what larger proteins could not be expressed in a functional
antibodies expanded from small-requirement (dose) diag- and structurally correct form in microbial systems. Human
nostics to large-dose therapeutics for HIV, cancer, allergic tPA, a protein with 528 amino acids, 15 disulfide bridges,
diseases, arthritis, renal prophylaxis, septic shock, trans- and three glycosilation sites is in this category. Initial at-
plantation, asthma, CMV, and anti-idiotype vaccines. The tempts to express functional tPA in E. coli failed, while ef-
development of recombinant monoclonal antibodies was forts to produce moderate quantities of this protein in CHO
largely driven by the need to “humanize” the product cells were successful. The naturally adherent CHO cells
to prevent immunological incompatibilities that lead to were scaled up for an industrial robot-driven production