Induction of immune response in BALB/c mice with a DNA vaccine encoding bacterioferritin or P39 of Brucella spp.

In this study, we evaluated the ability of DNA vaccines encoding the bacter ioferritin (BFR) or P39 proteins of Brucella spp. to induce cellular and hu moral immune responses and to protect BALB/c mice against a challenge with B. abortus 544. We constructed eukaryotic expression vectors called pCIBFR and pCIP39, encoding BFR or P39 antigens, respectively, and we verified tha t these proteins were produced after transfection of COS-7 cells. PCIBFR or pCIP39 was injected intramuscularly three times, at 3-week intervals. pCIP 39 induced higher antibody responses than did the DNA vector encoding BFR. Both vectors elicited a T-cell-proliferative response and also induced a st rong gamma interferon production upon restimulation with either the specifi c antigens or Brucella extract. In this report, we also demonstrat that ani mals immunized with these plasmids elicited a strong and long-lived memory immune response which persisted at least 3 months after the third vaccinati on. Furthermore, pCIBFR and pCIP39 induced a typical T-helper 1-dominated i mmune response in mice, as determined by cytokine or immunoglobulin G isoty pe analysis. The pCIP39 delivered by intramuscular injection (but not the p CIBFR or control vectors) induced a moderate protection in BALB/c mice chal lenged with B. abortus 544 compared to that observed in positive control mi ce vaccinated with S19.