April Journal-2009.p65 - Association of Biotechnology and Pharmacy

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Current Trends in Biotechnology and Pharmacy Vol. 3 (2) 113-127, April 2009. ISSN 0973-8916 technology from a model system into a practical vaccine. While tobacco is a good model system for evaluating the production recombinant proteins, it produces toxic compounds which make it unsuitable for vaccine delivery. Clinical trials have shown the induction of immune responses with antigen expressed in potato and lettuce (61 & 30). Lettuce is a fast growing species suitable for direct consumption and experimental studies. Another practical alternative may be rice, which 120 is commonly used in baby food because of its low allergenicity. Recent studies have shown that mammalian proteins can be expressed to high levels in transgenic rice (58). Furthermore, rice is easy to store and transport, and protein expressed in rice grains is stable at room temperature (58). Rice flour can also be mixed with baby food, clean water or breast milk for delivery to infants. Fig-1 Strategy for the development of plant edible vaccine Plant Derived Edible Vaccines
Current Trends in Biotechnology and Pharmacy Vol. 3 (2) 113-127, April 2009. ISSN 0973-8916 121 Modulation of immune response to acquire immune tolerance One of the utilities of producing antigens in plants in large amount is in treatment of autoimmune diseases like diabetes mellitus which involve production of antibodies against glutamic acid decarboxylase (GAD) and insulin, leading to destruction of insulin-producing pancreatic cells (17, 65). The antigens targeted for autoimmune response can be fed to the animals to induce immune tolerance. However, since the use of antigens for inducing oral tolerance requires production in large amounts of the human antigens that are generally difficult to produce by conventional means, attempts have been made to produce such antigens in plants. Insulin (2) and GAD (45) have been produced in potato and tobacco, respectively. To detect the delivery of plant-synthesized insulin to the gut associated lymphoid tissue, insulin was linked to cholera- toxin B subunit. Non-obese diabetic mice which were fed with the transformed potato tuber tissue containing microgram level of the recombinant insulin delayed the progression of clinical diabetes. Similarly, GAD-producing tobacco plants, given as a dietary supplement, inhibited the development of diabetes in the non-obese diabetic mouse. Expression and assembly of antibodies in plants Transgenic plants are also being looked upon as a source for producing large-scale antibodies which can serve the purpose of passive immunization by direct application, in addition to providing a tool for drug targeting or interactive inactivation of undesirable molecules (41, 27). Gene technology has provided great impetus to the utility of antibodies, since antibody genes can be altered to order. Thus not only genes coding for both the light and heavy chains have been expressed, but modified genes capable of expressing only Fab fragments (assembled light chains and shortened heavy chains) or ScFV (single peptide chains where variable domains of heavy and light chains are covalently linked by a short flexible peptide) have also been expressed in bacteria and mammalian cells (19, 7, 10, 52, 63, 18, 67, 53 & 54, 5, 6, 56, 33, 68) (Table-3). Murine antibodies have humanized by changing the constant and framework domains. In addition, recent technology involving PCR (Polymerase chain reaction) and phage display allow cloning and screening of antibodies with suitable avidity easily. Table 3. Antibodies and antibody fragments produced in transgenic plants Antibody Antigen Plant IgG (k) Transition stage analog Tobacco IgM (ë) NP(4-hydroxy-3-nitrophenyl) Tobacco acetyl hapten Single domain (dAb) Substance P Tobacco Single chain Fv Phytochrome Tobacco Single chain Fv Artichoke mottled virus coat protein Tobacco Fab; IgG (k) Human creatin kinase Arabidopsis IgG (k) Fungal cutinase Tobacco IgG (k) and SIgG/A hybrid S. mutagens adhesin Tobacco Single chain Fv Abscisic acid Tobacco Single chain Fv Nematode antigen Tobacco Single chain Fv â-glucuronidase Tobacco â-1,4 endoglucanase Single chain antibody fragment Atrazin, Paraquat Tobacco IgG Glycoprotein B of Herpes simplex virus Soybean Das et al
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April Journal-2009.p65 - Association of Biotechnology and Pharmacy

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