A bacterial protease inhibitor is a mucosal adjuvant.

DELPINO M. V.; IBAÑEZ A.; CORIA L.; BARRIONUEVO P.; GARCIA SAMARTINO C.; GIAMBARTOLOMEI G. H.; CASSATARO J

Congreso; 6th Annual Grand Challenges in Global Health Meeting; 2010

Innovative Idea: We propose that a bacterial protein can function as both a protease inhibitor to protect antigens (Ags) delivered in an oral vaccine from degradation and also as an adjuvant triggering and directing the type of mucosal immune responses. Status Report: Our previous results indicate that oral delivery of chicken ovalbumin (OVA) plus Omp19 from Brucella spp. as adjuvant induces the migration of CD4+ and CD8+ T cells to gastrointestinal lamina propria and induces OVA-specific IFN-γ-producing CD4+ T cells. In this work, we demonstrated that Omp19 can inhibit in vitro the activity of serine proteases (elastase, trypsin, alpha-chymotrypsin, Cathepsin G) while it partially inhibited the activity of aspartyl proteases (pepsin, cathepsin D) and did not affect cystein proteases. Interestingly, this protease inhibitor is pH and thermal stable since it retained its full activity when previously exposed to the pH range tested (2,2-9) or within the range of 25-100 °C. Omp19 partially inhibited (30-40%): i) the proteolytic activity of crude lysosomal extracts derived from J744 macrophage cell line and ii) Ag-degradation in J744 cells. Of note, this protein inhibited the protease activity of a stomach lysate from mice in vitro. Besides, oral delivery of the Ag (casein or OVA) in the presence of Omp19 prevented Ag degradation in vivo (50%) in the stomach of mice without inducing any adverse effects like diarrhea or dehydration. Furthermore, oral administration of Ag plus Omp19 induced dendritic cell migration to mesenteric lymph nodes. Altogether these results indicate that Omp19 possesses the capability to induce not only an inflammatory response but also inhibit the proteolysis of the Ag. Thus Omp19 would constitute an ideal mucosal adjuvant. Critical Next Steps:  To investigate Omp19 in vivo inhibition of Ag proteolysis at different times in different organs/cells. To validate its mucosal adjuvant capacity using OT-I and OT-II mice.