DNA electroporation prime and protein boost strategy enhances humoral immunity of tuberculosis DNA vaccines in mice and non-human primates

DNA vaccines have shown to induce strong immune response in small animals; however, its capacity of inducing robust antigen-specific immune responses in large animals is limited. In the present study, in vivo electroporation (EP) was applied and the effect of EP on humoral immune response against tuberculosis (TB) induced by DNA vaccination was tested in mice and rhesus macaques. Mice injected with 10 μg DNA encoding Ag85A and ESAT-6 followed by EP showed a reproducible humoral immunity which was equal to that obtained by using 100 μg DNA without EP. Boosting the DNA/EP treated animals with corresponding recombinant protein (50 μg of either Ag85A or ESAT-6) without adding adjuvant gave more than a 7–8-fold increase in the antibody titre but only 3–4-fold increase was found in the mice receiving 100 μg DNA without EP followed by protein boost. In concordance with the results obtained in mice, the monkeys received less DNA achieved equal high antibody responses to those induced by high dosage of DNA. Boosting the the DNA/EP treated monkeys with TB protein (500 μg of either Ag85A or ESAT-6) improved the humoral response by 7–8-fold increase in antibody titre, indicating electroporation's ability to compensate lower DNA concentration and enhance humoral immunity of TB DNA vaccines in mice and non-human primates.