The insertion of a 27aa peptide from Omp31 to the N-terminus of BLS significantly improved the degree of protection against B. melitensis and B. ovis infection.

J CASSATARO,; KARINA PASQUEVICH,; SILVIA ESTEIN,; A BOWDEN, RAÚL; CA FOSSATI,; GUILLERMO H. GIAMBARTOLOMEI; F GOLDBAUM,

Mérida. México

Congreso; Brucellosis 2005, International Research Conference.; 2005

In our laboratory we are studying different proteins from Brucella spp. in order to develop a subunit vaccine. Previous results demonstrate that a DNA vaccine codyng for an outer membrane protein of 31 kDa (Omp31) or a lumazine synthase (BLS) confer partial protection against Brucella infection (Cassataro in press, Velikovsky 2002). In this work, we constructed a chimerical BLS that contains a 27-residue long peptide (aa 48-74) comprising a putative extracellular exposed loop of the Omp31 (Vizcaino 2001) and delivered it as a DNA vaccine (pCIBLS-Omp31). Vaccination of Balb/c mice with pCIBLS-Omp31 provided the best protection level against B. ovis (3.14 log), which was higher than the given by the 2 plasmids (pCIOmp31+pcDNABLS) (2.20 log) and the control killed vaccine (H38S) (2.61 log). Moreover pCIBLS-Omp31 induced higher protection against B. melitensis (1.77 log) than pCIOmp31+pcDNABLS (1.09 log) but less protection than H38S (2.32 log). We then looked for a different immune response that could explain the better protection induced by this quimera. pCIBLS-Omp31 immunization developed stronger anti-Omp31 antibody responses than pCIOmp31 or pCIOmp31+pcDNABLS vaccination. CD8 and CD4 effector T cells from pCIBLS-Omp31-immunized mice were able to lyse in vitro Brucella-infected macrophages but there were no differences between the elicited responses from pCIOmp31+pcDNABLS-immunized mice. Moreover there were no Th1 (IL-2 or IFN-g secretion) responses after in vitro stimulation of splenocytes with rOmp31 or with the synthetic 27aa peptide in all groups. On the contrary Th1 responses after in vitro stimulation with rBLS were induced and were higher in the pCIBLS-Omp31 than in the pCIOmp31+pcDNABLS group. Altogether these results indicate that the addition of an immunodominant epitope from Omp31 to BLS significantly improved the degree of protection by each immunogen individually and will aid in the development of a subunit vaccine against Brucella spp.