BIOTECHNOLOGY - V. H. Herasymenko - 2006

Part II. Special Biotechnologies

Chapter 16. DNA VACCINES

16.1. STRUCTURE

Structurally, a DNA vaccine refers to plasmid DNA (a covalently closed circular molecule ranging from 4 to 6 kbp in length) that incorporates genes encoding the Proteins of a selected pathogen that are crucial for immunogenicity, expressing these proteins under the control of a eukaryotic promoter (a DNA region responsible for binding RNA polymerase to initiate METABOLISM/31.html">Transcription). The Construction of a DNA vaccine molecule typically employs the early promoter of cytomegalovirus, Rous Sarcoma virus, simian virus 40 (SV40), adeno-associated virus (AAV), α-globin, β-Actin, Dihydrofolate Reductase, as well as polyadenylation signals from SV40 or bovine Growth Hormone. To serve as a Selection marker required for the Replication of the recombinant plasmid in E. coli, an Antibiotic Resistance Gene (for ampicillin, or less commonly kanamycin) is included in the construct.

Replication of the plasmid DNA itself occurs exclusively in bacterial Cells (E. coli), whereas Transcription of the gene for the specific protective protein (the insert) takes place in mammalian cells.

To date, more efficient systems have also been developed that are capable of expressing not only individual antigen genes but also combinations thereof (Feltquate D. M., 1998), or—by additionally incorporating adeno-associated virus terminal repeat genes into the construct—integrating the DNA vaccine molecule into the host Cell chromosome (Deryabina O. et al., 2003), see Fig. 16.1.

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Fig. 16.1. Schematic diagram of the CSFV recombinant plasmid pTR-UFneo-:

TR - adeno-associated virus (AAV) terminal repeat, PCMV - cytomegalovirus promoter region, SD/SA - splice donor/acceptor, E2 CSFV - classical swine fever virus E2 protein gene, pA₁ - polyadenylation signal, pA₂ - polyadenylation signal, neo - neomycin resistance gene (selectable marker), Amp - ampicillin resistance gene

(selectable marker)