Evaluation of the potential of outer membrane vesicles from Brucella ovis as a vaccine against brucellosis

TOMAS LANDONI; FLORENCIA MUÑOZ GONZALEZ; LUCÍA ZAVATTIERI; BALDI PABLO C; FERRERO MARIANA CRISTINA

San Luis

Congreso; LXXI Reunion Anual de la Sociedad Argentina de Inmunología; 2023

Sociedad Argentina de Inmunología

Evaluation of the potential of outer membrane vesicles from Brucella ovis as a vaccine against brucellosisTomas Landoni, Florencia Muñoz González, Lucia Zavattieri, Pablo C Baldi, Mariana C. FerreroInstituto de Estudios de la Inmunidad Humoral (IDEHU), CONICE- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina. ferrerom@ffyb.uba.arSheep brucellosis is caused by Brucella ovis and B. melitensis. Control strategies for this disease include periodic diagnosis through serological tests and/or bacteriological cultures, as well as the culling of positive animals. Application of Brucella melitensis Rev-1 vaccine is recommended when prevalence is high. However, this attenuated vaccine strain presents significant drawbacks including the development of antibodies that interfere with serodiagnosis, and its virulence in humans, among others. Therefore, it is important to develop new safe and effective vaccines against ovine brucellosis. Outer Membrane Vesicles (OMV) from Gram-negative bacteria have been used in the development of acellular vaccines against numerous infectious diseases. In this study, we assessed the immunogenicity of OMV from B. ovis (strain Reo 198) with the aim of evaluating their potential as an acellular vaccine. For this purpose, B. ovis was cultured in tryptic soy broth supplemented with 0.5% yeast extract for 72 hours. OMV were isolated from the cell-free culture supernatant through ultracentrifugation. The protein content of the OMV fraction was determined using the bicinchoninic acid method, and the size of the isolated OMV was measured using Dynamic Light Scattering (DLS). DLS analysis demonstrated that OMV have a hydrodynamic diameter of 60 nm. To assess whether the B. ovis OMV antigens are recognized by serum antibodies from naturally infected sheep, an indirect ELISA assay was conducted using serum samples from both diseased and healthy animals. In another experiment female BALB/c mice were immunized by intramuscular route with 5 ug of OMVs, 5 ug of OMV plus 10 ug c-di AMP (adjuvant), or saline solution at 0 and 30 days. Sera samples were obtained at 21 and 45 days for the first immunization to determine specific antibody production by indirect ELISA. The levels of anti-OMV IgG in the sera of infected sheep were significantly higher than those of healthy animals (p