Vaccines and Therapeutic Proteins

In 1990, the first plant-made vaccines were performed via expression of Streptococcus mutans surface protein A in transgenic tobacco, followed by oral immunization of mice with the same plant material (Fischer and Emans, 2000). This transgenic plant material was later shown to successfully induce an antibody response through a demonstration that serum from immunized mice could react with intact S. mutans. Plants were also developed that expressed Escherichia coli enterotoxin B subunit (LT-B) and that exhibited successful inducement of both mucosal and serum antibody responses (Tacket, 2005). These initial experiments led to a cornucopia of studies involving generations of plant-made vaccines and therapeutic proteins and their applications in medicine. 

Transgenic Plants Expressing Vaccine and Therapeutic Proteins... 

This chapter illustrated the broad spectrum of uses for plant-derived vaccines and therapeutic proteins. Many of the biopharmaceuticals listed in this chapter were developed in transgenic tobacco or potato plants. While tobacco is not ideal for the expression of vaccine proteins nor is raw potato ideal for oral consumption, they are both relatively easy to work with and have been well characterized, making them useful for proof-of-concept studies. The use of plants for production systems and delivery vehicles holds great promise for future biopharmaceutical development. Proteins can be produced in plants while remaining biologically functional they can be scaled up for large production and purified inexpensively and with relative ease. The following chapters describe the many attributes of plant-made biopharmaceuticals in more detail. 

The stable transformation of plants has been used routinely as a method to express vaccine and therapeutic proteins. A number of disadvantages such as the length of time taken for transgenic plants to be generated and containment (i.e., preventing the escape of transgenes into the environment) have brought about a search for alternative methods by which to express proteins in plants. One such alternative is the utilization of plant virus expression systems. 

Commercial Uses of Virus Expression Vectors 4.2.5.1 Vaccines and Therapeutic Proteins... 

Several plant viral vectors have been used to successfully produce vaccines and therapeutic proteins in plants. TMV-based expression vectors represent one of the more successful examples and have produced a wide array of therapeutic proteins such as a-trichosanthin, tumor-specific single-chain antibodies, and a number of vaccine antigens (Table 4.1) (Dalsgaard et al., 1997). More recent examples of plant viral expression vectors utilized for vaccine production are provided in detail in Koprowski and Yusibov (2001), Pogue et al. (2002), and Canizares et al. (2005). 

Selected Examples of Vaccines and Therapeutic Proteins Expressed in Plants Using Plant Viral Expression Vectors... 

Examines the scale-up of plant-derived vaccine and therapeutic proteins in entire crops or in large batch cell suspension cultures... 

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