| | Production of Foreign Proteins from Transgenic Plant Suspension
Cultures
 | Optimized Production and
Stabilization of Mammalian Proteins Secreted from Transgenic Plant
Suspension Cultures
Transgenic plant cell suspension cultures can be utilized for the
production and secretion of biologically active mammalian proteins. Plant cell cultures
may offer an inexpensive alternative to the mammalian system for the production of
valuable foreign proteins. However, several difficulties remain before this promising new
protein production technology can be commercially viable. Primary among these is the fact
that the level of foreign protein expression within transgenic plant cells has to be
significantly increased. Furthermore, more efficient fermenter systems must be developed
to produce and recover the secreted mammalian proteins.
The objective of the research is to enhance the expression,
secretion, and recovery of mammalian proteins from transgenic plant suspension cultures.
Various human lymphokines including GM-CSF and interleukins (IL-2, IL-4, and IL-10) are
being employed as model transgenic protein products. The expression of mammalian proteins
in plant cells may be increased by using strong, constitutive and inducible promoters, or
by adding the non-translated leader sequence of the tobacco etch virus (TEV). The
targeting and secretion of transgenic proteins are being examined by adding various plant
signal peptide sequences. Protein recovery may be maximized through the testing of a
variety of additives for their effectiveness in stabilizing secreted transgenic proteins.
A novel affinity-chromatography bioreactor is being developed that uses the nickel-chelate
nitrilotriacetic column to increase in situ production and separation of the
secreted mammalian protein from plant suspension cultures. This research is being funded by the National Science Foundation.
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Production of Monoclonal Antibodies from Genetically Modified Plant
Suspension Cultures
Monoclonal antibodies (MAbs) are a highly diversified class of
proteins with major research and commercial applications. An increasing demand exists for
MAbs in the areas of diagnostics and therapeutics. Currently, the dominant method for
producing MAbs is through the fusion of antibody-producing spleen cells and a myeloma
line, which is known as hybridoma technique. However, this technique is slow, tedious, and
labor intensive. The number of antibody producing hybridoma lines per fusion is not large
enough to provide for an adequate survey of the immunological repertoire. There are also
significant limitations to produce antibodies with a precise amino acid sequence with this
technique. It is also costly to cultivate large quantities of hybridoma cells because of
their slow growth, low product yield, shear sensitivity, and expensive culture medium.
The production of MAbs in cultured transgenic plant cells can
offer some advantages over that in the mammalian systems. The media to cultivate plant
cells are well defined and inexpensive. Because plant cell medium does not contain
proteins, down-stream processing for the plant cell system is easier than that of the
mammalian cultures. Contamination by bacteria or fungi is easily monitored in plant tissue
cultures. Furthermore, these contaminants are usually not potent pathogens to human
beings.
This research was funded by the National Science Foundation.
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Comments and questions: jmlee@wsu.edu. Revised
January 15, 2001.
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