CONICET | Buscador de Institutos y Recursos Humanos

Brucella spp. can be transmitted to humans through mucosae. Currently,there are no human vaccines against this infection. We have previously shown thatBtaF is an adhesin involved in the attachment of Brucella spp. to biotic andabiotic surfaces, and that it is important for the dissemination andpersistence of the pathogen after intra-traqueal murine infection. Based on theseresults, we evaluated BtaF as a potential component of an acellular vaccine againstbrucellosis. Six-week-old Balb/c mice were weekly immunized for 3 weeks with BtaF(10ug) plus 3?,5?-c-di-AMP (c-di-AMP,10ug), c-di-AMP alone or saline. One weekafter last immunization serum, saliva, feces, bronchoalveolar (BAL) and vaginallavage (VL) fluids, lung homogenates and spleens were obtained. Levels of BtaF-specificantibodies were measured by indirect ELISA in all samples. In vitro production of gamma interferon (IFN-γ) or interleukin-5 (IL-5) by spleen cells stimulated with BtaF (1 or 10µg), ConA or RPMI was determined. Immunized mice showed increased serum levels of total antibodies againstBtaF (p<0.0001), and of specific IgA in saliva, feces, BAL, VL and lungs(p<0.0001; p<0.0001; p<0.05; p<0.01; p<0.05) compared with controls.IgA titers in serum were 12800. Serum titers of IgG2a were higher than those of IgG1 (409600 vs. 51200). The IgG1/IgG2a ratiowas 0.49. Splenocytes from immunized mice secreted high levels of IFN-γ (495.5 pg/ml for 10ug, p<0.05) and IL-5 (222.8pg/ml for 1 ug BtaF and 454 pg/ml for 10ug, p<0.01 and p<0.05).Thisincrement in IFN-γ production was abolished when CD4+ cells were depleted (p<0.01) butnot after CD8+ cells depletion. Intranasal vaccination with BtaF plus c-di-AMP induced a systemic andmucosal specific immune response, which may contribute to prevent the mucosalentry of Brucella and its dissemination. The activated cellular immune responseshown by high levels of IFN-γ, was dependent onCD4+ cells and may be crucial for a protective effect of this vaccine.