Vaccination with polymerase chain reaction-generated linear expression cassettes protects mice against lethal influenza A challenge.

The feasibility of a linear expression cassette (LEC)-based influenza A DNA vaccine was demonstrated in mice, using a lethal dose (LD90) of a mouse-adapted A/Hong Kong/8/68 (H3N2) influenza strain. LECs expressing hemagglutinin (HA) from either the homotypic H3N2 or the heterotypic H1N1 (A/Puerto Rico/8/34) influenza virus were produced by polymerase chain reaction and either phosphodiester- or phosphorothioate-modified oligonucleotide primers. Survival subsequent to lethal viral challenge was used as a primary end point; weight loss was the secondary end point. Survival and weight loss data showed that protection can be achieved in mice with 50 microg of phosphate-buffered saline-formulated LEC DNA or 2 microg of Vaxfectin-formulated LEC DNA. Survival correlated with neutralizing antibody titers (hemagglutination inhibition, HAI); titers obtained after vaccination with LEC were equivalent to those obtained with HA (H3N2) plasmid DNA control. Vaccination with heterotypic H1 HA-LEC DNA provided no protection against viral challenge.

Plasmid vaccines and therapeutics: from design to applications.

In the late 1980s, Vical and collaborators discovered that the injection into tissues of unformulated plasmid encoding various proteins resulted in the uptake of the plasmid by cells and expression of the encoded proteins. After this discovery, a period of technological improvements in plasmid delivery and expression and in pharmaceutical and manufacturing development was quickly followed by a plethora of human clinical trials testing the ability of injected plasmid to provide therapeutic benefits. In this chapter, we summarize in detail the technologies used in the most recent company-sponsored clinical trials and discuss the potential for future improvements in plasmid design, manufacturing, delivery, formulation and administration. A generic path for the clinical development of plasmid-based products is outlined and then exemplified using a case study on the development of a plasmid vaccine from concept to clinical trial.