Arntzen, personal communication. This level of production is clearly not necessary for all protein pharmaceuticals, but there are many cases in which large quantities are required. Monoclonal antibodies mAbs , the largest class of biologics now in development, are often needed in substantial amounts. Many mAbs are also being developed as topical mucosal treatments, in which the dosage requirements and the need for repeated applications are likely to be much greater due to the washing effects of mucosal secretions.
For example, the Guy's 13 mAb, which prevents colonization of the oral cavity by Streptococcus mutans , required a dose of If this were administered to the child population of Europe alone, a production capacity of more than 1, kg per year would be required. Other topical agents are likely to be needed at similar levels. HIV protein microbicides could be used to prevent HIV transmission by topical vaginal or rectal application. However, these reagents have not yet been tested in humans because existing manufacturing capacities are not able to produce sufficient amounts for clinical tests.
Thus, to treat one million women, it would be necessary to produce approximately kg of the protein per year. Producing therapeutics for the developed world is important, but there is also a moral imperative to provide medicines for developing countries. We will probably see an effective vaccine against HIV in the next few years, but as soon as it is developed, the global demand will far exceed our ability to produce the compound. Beyond HIV, there are many other infectious diseases that require attention.
Recombinant hepatitis B vaccine, for instance—produced in genetically modified yeast at present—cannot be made in sufficient quantities and at a low enough cost to meet the demands of developing countries. The scalability of production in transgenic plants could offer one of the few practical solutions to overcome these commercial and moral dilemmas.
Regardless of the availability of a vaccine or protein therapeutic, cost is a major factor for developing countries. In addition, it is likely that new vaccines will become more complex in composition, have longer development times and consequently will cost more when they come to market. Although the cost of production in plants will be low, this may not be the most important economic factor. Several other factors influence the price of new vaccines, including regulatory requirements for drug development and manufacture—which have become more stringent and costly in recent years—the high failure rate of new drugs, and the protection of IP.
Production in transgenic plants could offer a new model for vaccine development. Hopefully, developing countries would be involved, and the focus would shift to specific regional diseases that do not otherwise feature prominently in current drug development. Another fundamental advantage of plants has always been the range and diversity of recombinant molecules that they can potentially produce. As higher eukaryotes, plants are able to synthesize small peptides, polypeptides and complex multimeric proteins, many of which cannot be made in microbial systems Ma et al , This versatility is reflected in the increasing number of recombinant proteins that has been reported in the literature.
For many molecules, such as antibodies, the presence of plant chaperones that are homologous to those in mammalian cells is an important factor, as these chaperones control the efficiency of protein assembly and the extent of protein degradation.
The overall benefits are not only in the range of recombinant proteins that can be made in plants, but also in the flexibility that is allowed in the engineering of new pharmaceutical proteins, which can be designed with plant expression in mind Chargelegue et al , There has been much interest in the oral delivery of vaccines using edible transgenic plant material, but one major hurdle is the need to ensure an appropriate immune response. Despite the advantages of oral delivery, only the live Sabin polio vaccine is delivered by this route at present, which reflects important gaps in our knowledge of the mucosal immune system.
However, PDPs would undoubtedly assist vaccine programmes in developing countries by simplifying immunization regimens and reducing the costs of vaccine production, purification, storage and administration. Nevertheless, it is important to recognize that edible vaccines will not be delivered as fresh produce, as often suggested.
A regulated product requires controlled delivery of standardized doses, so some level of processing of the edible plant material would be required. This need not include complex purification, but is more likely to involve simple and inexpensive food processing techniques that are readily available, such as freeze drying.
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Although the potential advantages of plants for PDP production are now becoming clearer, concerns remain about low product yield, modified glycan structures and the impact of pharmaceutical plants on the environment. Nicholson et al delivered into rice plants four transgenes that represent the components of a secretory antibody. Even though they were delivered on different plasmids, such multiple transgenes are frequently inherited in a linked fashion Chen et al , Direct DNA transfer also allows the introduction into plants of minimal expression cassettes that contain only the promoter, open reading frame and terminator sequences.
In the case of plant glycosylation, it is unlikely that plant glycans will be immunogenic or allergenic, but altered glycans might affect the functionality of some recombinant glycoproteins. Another maturing technology is the synthesis of PDPs in plastids. This confers significant advantages, primarily because of the large number of transgene copies in homoplasmic transformants, which allows the production of extremely high levels of recombinant protein Bock, ; Daniell, However, there have also been several cases in which there was little or no expression of a target pharmaceutical molecule in plastids.
Codon optimization can be an issue, as was shown in the case of TetC, in which transgenes with a high AT content were expressed at the highest levels. Recombinant proteins are also subject to proteolysis in plastids. The choice of target antigen must therefore reflect an understanding of the microenvironment in the chloroplast and its functionality, to ensure efficient and stable protein accumulation without adversely affecting chloroplast function.
Whilst transformation and transgene expression are important technological goals, it is also necessary to consider the wider impact of pharmaceutical plants on human and environmental health. Two safety issues are often raised in this context: the possible transgene escape through pollen or seed dispersal, and the potential for recombinant molecules to enter the food chain. Transformation of the plastid genome is one of several strategies that have been put forward to minimize transgene flow through pollen Daniell, , as the plastid DNA is maternally inherited in most crop plants Fig 1.
An alternative is the use of male sterile plant lines, in which no pollen is produced. Seed dispersal could be prevented by making seed viability dependent on an exogenous stimulus, such as the application of a chemical inducer Daniell, In cases where direct oral administration of the pharmaceutical is desirable, edible plants are clearly preferred.
Are you sure you want to Yes No. Jahangir Alam. Mahima Thakur. Misikir M. Show More. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. Molecular pharming 1. History Introduction Conclusion Applications of transgenic animals in pharmaceuticals Methods of creating transgenic animals Contents Reference 3. Using genetically modified plants or animals to produce pharmaceuticals, also called as Gene Pharming; part of Molecular Farming Introduction 4.
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Transgenic animals are animals which have been genetically transformed by splicing and inserting foreign, animal or human genes into their chromosomes. The inserted gene, when successful, enables an animal to make a certain pharmaceutical protein in its milk, urine, blood, sperm, or eggs, or to grow rejection-resistant organs for transplant. Gordon and F.dockdine.com/4033.php
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Retrovirus-mediated gene transfer. Transgenic Animals And Their Applications The animal whose genetic material is taken from another organism is called as transgenic animal. The artificial genes are inserted in the germline cells of the organisms so they pass from one generation to the other. Cancer as a Metabolic Disease. Thomas Seyfried. Curtis Klaassen. Color Atlas of Genetics. Eberhard Passarge. Golder N. Advances in Applied Microbiology. Allen I. Stem Cell Culture. Jennie P.
Plant-based vaccines against viruses
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