A Study of PA DNA/Dendron Nanoparticles for Genetic Immunisation Against Anthrax

Protective antigen (PA), the binding subunit of toxins produced by Bacillus anthracis is singularly the most important antigen required for specific immunity to anthrax disease. We used cationic poly-lysine dendrons to develop a genetic anthrax vaccine. Plasmid CMV/ER PA83 which encoded full length PA 83 was complexed with dendrons to form dendriplexes. Two types of dendron were used: C0 and C18.These were mixed with DNA to form dendriplexes, of approximately 80 nm in size, which were tested for immunogenicity. A/J and BALB/c mice were vaccinated with dendriplexes containing 1μg and 50 μg plasmid DNA per dose over a period of 6 weeks. Immunisation with naked PA DNA did not induce an antibody response even after secondary boosting, whereas both dendriplexes produced strong anti-PA antibody response. This response was dose dependent. We conclude that dendriplexes show superior immunogenicity compared to naked PA DNA in both mouse strains and that C18 dendriplexes with 50 μg plasmid DNA are most efficacious. However, the elicited antibodies did not neutralise lethal toxin in vitro. Therefore further work is required to improv these preparations in order to elicit functional antibodies.