The appearance of new viruses and the cost of developing certain
vaccines require that new vaccination strategies now have to be developed.
DNA vaccination seems to be a particularly promising method. For this application, plasmid
DNA is injected into the subject (man or animal). This plasmid
DNA encodes an
antigen that will be expressed by the cells of the subject. In addition to the
antigen, the plasmid also encodes a resistance to an
antibiotic, which is used during the construction and production steps of the plasmid. However, regulatory agencies (FDA, USDA and EMA) recommend to avoid the use of
antibiotics resistance genes. Delphi Genetics developed the Staby(®) technology to replace the antibiotic-resistance gene by a selection system that relies on two bacterial genes. These genes are small in size (approximately 200 to 300 bases each) and consequently encode two small
proteins. They are naturally present in the genomes of bacteria and on plasmids. The technology is already used successfully for production of
recombinant proteins to achieve higher yields and without the need of
antibiotics. In the field of
DNA vaccines, we have now the first data validating the innocuousness of this Staby(®) technology for eukaryotic cells and the feasibility of an industrial production of an
antibiotic-free
DNA vaccine. Moreover, as a proof of concept, mice have been successfully vaccinated with our
antibiotic-free
DNA vaccine against a deadly disease,
pseudorabies (induced by Suid herpesvirus-1).