A BRUCELLA PROTEASE INHIBITOR IS A USEFULL ADJUVANT IN ORAL VACCINE FORMULATIONS.

RISSO, GS; IBAÑEZ AE; CORIA LM; PASQUEVICH KA; DELPINO M. V.; BRIONES G; CASSATARO J

Congreso; XXXVII Congreso de la Sociedad Brasilera de Inmunología; 2012

Introduction: Previous results showed that a Brucella protein (BP) administered by the oral route and without adjuvants induced protection against oral Brucella challenge. These results indicated that BP had self-adjuvant properties and prompted us to study its potential application as adjuvant for other antigens (Ags).Methods and Results: Our results indicated that BP is a broad spectrum protease inhibitor with a stronger activity against serine proteases secreted by the pancreas to the intestine (elastase, trypsine and alpha chymotrypsin; p<0.05, n=5). As BP is able to inhibit in vitro the activity of many proteases present at the gastrointestinal tract we directed all our efforts to study its potential application in oral vaccine delivery. We showed that in BALB/c mice (n=5) oral delivery of OVA in the presence of BP resulted in a significantly increased OVA-specific T cell response (DTH assay; p<0.05, n=5) and OVA-specific IFN-γ producing CD4+ and CD8+ T cells determined by flow cytometry at the mucosal (MLNs; p<0.05, n=5) and systemic (spleen; p<0.05, n=5) level.The natural route of infection and the need for a Th1-biased response, makes Salmonella Typhimurium a strong candidate for oral vaccination with the novel adjuvant BP. Therefore, we fed BALB/c mice (n=5) with i) Heat-killed Salmonella (HKS), ii) HKS+BP or iii) HKS+CTB and challenged them later with virulent S. Typhimurium by the oral route. We also evaluated anti-HKS specific IgA in feces and IgG in serum of immunized animals by ELISA and found that BP induces an increase in HKS-specific antibody production.Conclusion: Altogether, our results suggest that BP would be an ideal mucosal adjuvant. When co-delivered orally it can bypass the harsh environment of the gastrointestinal tract inhibiting proteases. Besides it can enhance Th1 and CD8+ T Ag-specific immune response and would be a useful adjuvant in oral killed vaccine formulations against Salmonella.