The Effect of Cationic Liposomes Encapsulating pcDNA3.1+PA Plasmids on Humoral Immune Response in Mice

Background: DNA vaccines are third generation vaccines which have made promises to combat infectious diseases. Cationic liposomes are used as effective delivery systems for DNA vaccines to generate stronger immunity. Objective: Encapsulation of pcDNA3.1+PA plasmid, encoding protective antigen (PA) of Bacillus anthracis (B. anthracis) into cationic liposomes, and evaluation of its effect on specific humoral specific immunity against PA were aimed. Methods: The liposomes containing pcDNA3.1+PA plasmids were prepared with phosphatidylcholine (PC), dioleoyl phosphatidylethanolamine (DOPE) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) using dehydration-rehydration method. BALB/c mice were immunized by intramuscular (IM) injection to investigate the immunogenicity of the formulations. The resulting specific antibodies against PA, total IgG, IgG1, IgG2a and IgG2b isotypes, were evaluated by enzyme linked immunosorbent assay (ELISA) method. Conclusion: A higher concentration of specific IgG against PA was found in sera of a group immunized with the encapsulated plasmid compared with the naked plasmid alone. This difference was significant for IgG1 isotype.