Antigen expressing vectors

LDH-x is one of the best characterized antigens and its amino acid sequence is known. A synthetic peptide based on a portion of the molecule has been shown to reduce fertUity in laboratory animals. The nucleotide sequence coding for human LDH-x has been defined and engineered into an expression vector system (121). 

Smith, G.P. Filamentous fusion phage novel expression vectors that display cloned antigens on the virion surface. Science 228 1315-1317, 1985. 

PCA Passive cutaneous anaphylaxis pCDM8 Eukaryotic expression vector PCNA Proliferating cell nuclear antigen... 

Yeast expression vectors have been among those most commonly used since the beginning of gene technology. Vectors based on baker s yeast, Saccharomyces cerevisiae, have been especially popular for robust expression of many types of recombinant proteins [90]. For instance, the first commercially available recombinant vaccine, the hepatitis B surface antigen vaccine, was produced from an S. cerevisiae vector [91]. Many other recombinant proteins have also been efficiently expressed in yeast including al-Antitrypsin [92], insulin [93], Epstein-Barr virus envelope protein [94], superoxide dismutase [95] and interferon-a [90]. 

FIGURE 4.2 Schematic diagram of RNA virus expression vectors, (a) TMV as an epitope presentation system, and (b) a polypeptide presentation system. Dark diamonds represent foreign antigen/peptide. 

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). 

The field of DNA vaccines centers on the ability to deliver genetic material, coding, for desired protein antigens in the context of a mammalian expression vector (Donnelly et al., 1997). It was realized that the immunostimulatory properties observed with DNA vaccines, namely the ability to induce a Thl biased or cell mediated immune response, was attributable in part to the presence of CpG motifs within the plasmid DNA (Klinman et al., 1997). In fact, it was demonstrated that the quality of immune activation by DNA vaccines could be influenced by the deliber-ate alteration of CpG content (Krieg et al., 1998). Further, with the identification of neutralizing CpG motifs it became possible to remove any neutralizing influence from the DNA vaccine plasmids. The end result was the optimization of DNA vaccine plasmids, with respect to immune activation (Krieg et al., 1998). 

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