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

K. A. PASQUEVICH; S. M. ESTEIN; S. DE LA BARRERA; R. BOWDEN; C. A. FOSSATI; G. H. GIAMBARTOLOMEI; J. CASSATARO

Córdoba, Argentina

Congreso; VII Congreso Latinoamericano de Inmunología; 2005

The outer membrane protein of 31kDa from Brucella melitensis as recombinant protein (rOmp31) confers protection against B. melitensis by eliciting a Th1 response. We studied the T cells subsets involucrated in this protective immunity. rOmp31-vaccinated mice were depleted in vivo of CD8+ T cells or CD4+ T cells. In the absence of immune depletion, mice given rOmp31 exhibited a significant (p‹0.01) degree of protection against B. melitensis when compared with controls reciving PBS (1.22log protection). rOmp31 vaccination induced 1.13log protection in mice depleted of CD8+ T cells (p‹0.05) and 0.372log protection in CD4+-depleted mice (p›0.05). To determine the contribution of T cells subsets in the Omp31-specific Th1 response, spleen cells were depleted of CD4+ or CD8+ T cells, CD4+ T cells depletion abrogated the antigen-specific secretion of IL-2 and IFN-g in rOmp31 vaccinated mice and depletion of CD8+ T cells did not affect the cytokine production. We studied an exposed region on Omp31, a protective B epitope that is located to a hydrophilic loop. We design a 27 aa synthetic peptide comprising aa 48-74 from Omp31 (Omp3148-74) and immunized animals with Omp3148-74 in adjuvant. Spleen cells from Omp3148-74 immunized mice produce antigen-specific IFN-g and IL-2, and this cytokine production was mediated by CD4+ T cells. Omp3148-74 immunization confers significant levels of protection against B. melitensis similar to rOmp31 immunization, indicating that Omp3148-74 contains immunodominant protective T cells epitope.