A synthetic peptide derived from Omp31 elicits a Th1 response and confers similar levels of protection against Brucella melitensis than whole Omp31.

KARINA PASQUEVICH,; SILVIA ESTEIN,; DE LA BARRERA SILVIA,; A BOWDEN, RAÚL; CA FOSSATI,; GUILLERMO H. GIAMBARTOLOMEI; JULIANA CASSATARO,

Córdoba

Congreso; VII Latin American Congress of Immunology.; 2005

ALAI

Previous results demonstrate that the recombinant outer membrane protein of 31kDa from Brucella melitensis (rOmp31) induce a specific T helper (Th) 1 response and confers protection against B. melitensis. In the present work in vitro T cell subset depletion showed that rOmp31 immunization elicited specific CD4+ Th1 cells while CD8+ T cells induced cytotoxic activity. In vivo depletion of T cell subsets showed that the rOmp31 elicited protection against B. melitensis infection is mediated by CD4+ T cells and CD8+ T cells did not contribute. We then studied a known exposed region from Omp31 on the Brucella membrane that comprises aminoacids (aa) 48-74 of Omp31. We evaluated the immunogenicity and protective efficacy of the 27aa synthetic peptide (Omp3148-74) in incomplete Freund´s adjuvant. Immunization with the peptide did not elicit specific humoral responses but elicited a Th1 response mediated by CD4+ T cells. Omp3148-74 conferred significant (p<0.01) protection (1.15 log) against B. melitensis. Levels of protection conferred by Omp3148-74 were similar (p>0.05) to those obtained with rOmp31 (1.24 log). The attenuated control vaccine Rev-1 induced 2.33 log protection. Finally, the finding that Omp3148-74 is a Th1 protective peptide will contribute in the development of a multivalent subunit vaccine against Brucella spp carrying only protective epitopes.