Omp19 has the ability to induce the internalization of the co-administered antigen in antigen presenting cells in vitro and triggers cytotoxic T cell responses against the antigen.

CORIA, LORENA; IBAñEZ, ANDRéS; BERGUER, PAULA; BARRIONUEVO, PAULA; GIAMBARTALOMEI, GUILLERMO; CASSATARO, JULIANA

Buenos Aires

Congreso; 1º Congreso Franco-Argentino de Inmunología, LVIII Reunión Anual de la Sociedad Argentina de Inmunología.; 2010

Sociedad Argentina de Inmunología

Previously, we have demonstrated that the protein moiety of Omp19 from Brucella spp.(U-Omp19) has adjuvant properties and could be used as a Th1 adjuvant that facilitates antigen (Ag) cross-presentation and induces IFN-ã producing CD8+ T cells. Given the capacity of antigen presenting cells (APCs) to modulate immune responses, in the present study we investigated if APCs are involved in the ability of U-Omp19 to stimulate a specific CD8 T cell response. To assess this, purified dendritic cells (DCs) from spleen of C57BL/6 mice were treated with ovoalbumin (OVA) alone or plus U-Omp19 or LPS as positive control and then co-cultivated with OTI CD8+ T cells. We evaluated the induction of IFN-ã producing T cells by intracellular IFN-ã staining and degranulation of cytotoxic T cells by CD107a expression on the membrane. A higher percentage of IFN-ã producing T CD8 (32.36%) and cytotoxic T cells (14.06%) was induced when DCs were stimulated with OVA+U-Omp19 compared to T cells co-cultivated with DCs pulsed with OVA alone (23.42% and 8.98% respectively). These results suggested that U-Omp19 can act directly on DCs to enhance T cell responses. Therefore, we evaluated if Omp19 has a direct effect on APCs that could enhance the Ag internalization and presentation to T cells. To this end, purified DCs from spleen mice were pulsed in vitro with OVA-FITC alone or OVA-FITC+U-Omp19 or LPS as positive control. DCs pulsed with OVA-FITC+U-Omp19 showed a greatly increase in Ag internalization compared with OVA alone (MFI 367.88±19.1 vs. 15.29±1.8). We have also found that U-Omp19 increased OVA internalization by J774 macrophage cell line and by A20J B-lymphoma cell line at different times. These results indicate that U-Omp19 increases the Ag capture by immature DCs, macrophages and B lymphocytes. In conclusion, U-Omp19 as adjuvant increases the amount of internalized Ag in APCs. This capacity would lead the improved T CD8 and CTL immune responses observed when U-Omp19 is co-administered with the Ag.