A disordered region holds the full protease inhibitor and vaccine adjuvant activities of U-Omp19

M. LAURA DARRIBA; CELESTE PUEBLAS CASTRO; LORENA M. CORIA; LAURA BRUNO; LUCÍA B. CHEMES; RODOLFO M. RASIA; SEBASTIÁN KLINKE; JULIANA CASSATARO; KARINA A. PASQUEVICH

Congreso; 13th Latin American and Caribbean Congress of Immunology ALACI 2022; 2022

U-Omp19 is a bacterial protease inhibitor from Brucella abortus that inhibits gastrointestinal and lysosomal proteases, enhancing the half-life and immunogenicity of co-delivered antigens. U-Omp19 is a novel adjuvant that is in preclinical development with various vaccine candidates. However, the molecular mechanisms by which U-Omp19 exerts these functions and the structural elements responsible for these activities remain unknown. To elucidate the molecular basis of the U-Omp19 protease inhibitor and adjuvant activities we performed a structural, biochemical, and functional characterization of U-Omp19. Protein crystallography and NMR studies revealed that the protein consists of a compact C-terminal beta-barrel domain and a flexible N-terminal domain. To evaluate the contribution of each domain to U-Omp19´s activities several truncated protein constructs were designed and obtained. Our results demonstrate that the N-terminal domain behaves as an intrinsically disordered protein and that it retains the full protease inhibitor and adjuvant activities of U-Omp19. Collectively, these results may contribute to fulfill the need for vaccine adjuvant development by offering insights into the U-Omp19 biological mechanisms of action and by enabling the design of novel engineered structures that may have enhanced activity, stability, or be conjugated with other bioactive molecules or vaccine antigens.