A bacterial protease inhibitor delivered subcutaneously limits APCs lysosomal proteolysis and increases immunogenicity of co-administered antigen

LORENA M. CORIA; ANDRÉS E. IBAÑEZ; MARIANELA V. CARABAJAL; PAULA BERGUER; LAURA BRUNO; GABRIELA S. RISSO; PAULA GONZALEZ COBIELLO; GABRIELA S. RISSO; MARIA FERNANDA FRANK; KARINA A. PASQUEVICH; JULIANA CASSATARO

Seattle

Conferencia; The Modes of Action of Vaccine Adjuvants; 2014

Keystone Symposia on Molecular and Cellular Biology

Our previous results demonstrated that a Brucella spp. protein (Bp) is a broad spectrum protease inhibitor as it can inhibit proteases present in the stomach and gut (mostly serine proteases). In this work we demonstrated that Bp also possesses inhibitory activity on lysosomal proteases (cysteine proteases). Bp partially reduced the proteolytic activity of commercial cysteine proteases in vitro. Inhibition mechanism of Bp on cysteine proteases was characterized using a specific fluorogenic substrate for cathepsin L indicating that Bp is a competitive inhibitor of cathepsin L with an inhibition constant in the µM range. Also, Bp was able to inhibit Ag degradation by antigen presenting cells (APCs) increasing Ag half life and promoting its cross presentation. Bp inflammatory properties were also analyzed. After subcutaneous administration, Bp increased the recruitment of APCs to draining lymph nodes. Furthermore, Bp induced the up-regulation of co-stimulatory molecules and secretion of pro-inflammatory cytokines from DCs in vitro. Moreover, subcutaneous co-administration of Bp as adjuvant and ovalbumin (OVA) as model antigen (Ag) induced OVA specific IFN-g producing CD8+ T cells and cytotoxic T cells. Finally, the adjuvant capacity of Bp in vaccine formulations using real microbial derived Ags was studied using a whole homogenate of Trypanosoma cruzi parasites (WH). Subcutaneous co-administration of Bp with WH reduced parasite loads and increased survival after T. cruzi infection in mice. Altogether, these results indicate that Bp behaves as an ideal component in vaccine formulations against infectious diseases.