DISCOVERY OF NEW ADJUVANTS FOR ORAL VAC- CINE FORMULATIONS

CELESTE PUEBLAS CASTRO; LORENA CORIA; LAURA BRUNO; KARINA PASQUEVICH; JULIANA CASSATARO

Congreso; LXIX REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI; 2021

In our laboratory, we have shown that U-Omp19 would be an idealmucosal adjuvant because it can inhibit gastrointestinal proteaseswhile it induces adaptive immune responses. To our knowledgethere are no other published reports describing the use of proteaseinhibitors from bacteria as immune vaccine adjuvants.Based on these previous results, we studied if other microbial pro-tease inhibitors also have adjuvant activity. After an in-silico screen-ing using MEROPS database plus literature, we have selected 11protease inhibitors present in human pathogenic microorganismsrepresenting different families of protease inhibitors.We made a screening based on 3 different selection criteria: i) pu-rification yield, ii) protease inhibitor activity against gastrointestinalproteases and iii) immunostimulatory properties. Our results indicatethat 5 putative protease inhibitors can inhibit the protease activity ofgastrointestinal proteases and pancreatin extract (p<0.001 ANOVA+ Bonferroni). We also shown that these molecules have the capac-ity to activate immune cells. We have found a significant increasein the production of IL-6 in BMDCs from C57BL/6 and C3H/HeJmice when the cells were stimulated with the protease inhibitors,compared with medium (p<0.001 ANOVA + Bonferroni) in 3 of them.Finally, we have found a significant increase in the proliferation ofOT-I CD8+ T cells after oral administration of OVA plus each of the3 bacterial protease inhibitors, compared with OVA alone (*P<0.05,**P<0.01 ANOVA + Bonferroni)Together our results show that the new identified bacterial proteaseinhibitors could be mucosal adjuvants, since they are able to in-crease adaptive immune responses to orally co-delivered model Ag.