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Transgenic plants expressing vaccine antigens can be used to tackle autoimmune disease like diabetes. Insulin dependent diabetes melites is an autoimmune disease resulted in the destruction of insulin producing pancreatic cells.
Disease is triggered by involvement of both humoral and cell mediated immunity. The type I diabetes by autoimmunity is due to the inadvert attack on insulin producing cells by their own body immune system. As a result, insulin produced by the body is seen as an offender protein or auto-antigen and it will be targeted to destroy insulin producing cells.
Oral administration of pancreatic specific auto-antigen can prevent autoimmune diabetes. However, therapy requires repeated administration of large amount of auto-antigen. Thus, inducing oral tolerance requires production of large amount of human antigen, which is extremely difficult to produce by conventional methods.
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Therefore, attempt has been made to produce auto-antigen like insulin and glutamic acid decarboxylase (CAD) in plant to acquire immune tolerance. A plant based cholera toxin B subunit and insulin fusion protein has been produced successfully in transgenic plants.
These groups generated transgenic potato plant that synthesizes human insulin at level upto 0.05% of total soluble protein. In order to deliver plant derived insulin to the gut-associated lymphoid tissues, insulin was linked to the cholera toxin B subunit (CTB). Plant produced insulin retained GM1-ganglioside binding affinity and antigenecity of both CTB and insulin.
When diabetic mice were fed with transgenic potato tuber containing microgram level of CTB insulin fusion antigenic protein showed substantial reduction in pancreatic islet inflammation and delay progression of diabetes. This indicated that plants are ideal system for the large production of large quantities of insulin, which are required for oral tolerance.
