MODULATION OF IMMUNE-RESPONSES IN BALB C MICE VACCINATED WITH BRUCELLA-ABORTUS CU-ZN SUPEROXIDE-DISMUTASE SYNTHETIC PEPTIDE VACCINE/

Three peptides, peptide 1 (GGDNYSDKPEPLGG), peptide 2 (LAEIKQRSLMVHGG) and peptide 3 (GGAPGEKDGKIVPAG), were synthesized based on the amino acid sequence of Brucella abortus Cu-Zn superoxide dismutase. These pe ptides were selected on the basis of their predicted hydrophilicity, f lexibility and antigenicity profiles. The three peptides, singly or in combination, with or without the adjuvant monophosphoryl lipid A were administered to Balb/c mice as vaccines for brucellosis. The protecti ve and immune responses induced by the peptide vaccines after challeng e exposure to virulent B. abortus strain 2308 were compared to those o btained with salt-extractable proteins (BCSP) vaccine prepared from B. abortus strain 19, recombinant B. abortus Cu-Zn superoxide dismutase (rSOD) vaccine and non-vaccinated mice. Mice vaccinated with 30 mu g o f peptide 3 plus 50 mu g monophosphoryl lipid A afforded two logs of p rotection (reduction in log(10) colony-forming units compared with con trol mice) and one log of protection when given without monophosphoryl lipid A, whereas 5 mu g of the salt-extractable proteins afforded thr ee logs of protection. The rSOD and peptides 1 and 2 given with or wit hout monophosphoryl lipid A afforded no protection. Superoxide dismuta se-specific IgG antibody was present in postchallenge sera only if BCS P was present in the vaccine. Peptide-specific IgG antibodies were pre sent in postchallenge sera of mice, and antibody concentrations were g enerally enhanced when monophosphoryl lipid A was included in the vacc ine. The overall results with the peptide vaccines suggest that peptid e 3 probably contains a specific sequence preferentially recognized by the cellular immune system leading to modulation of immune response m echanisms responsible for decreasing splenic infection.