Outer membrane vesicles as vaccines candidates against Brucella suis infection

BIALER, MAGALÍ G; RAMIS LILA; MUÑOZ GONZALEZ F; CERRUTI MARIA LAURA; BALDI PABLO CESAR; FERRERO MARIANA CRISTINA; ZORREGUIETA ANGELES

Cordoba

Congreso; Congreso de la Sociedad Argentina de Investigaciones Biológicas; 2022

Sociedad Argentina de Investigaciones Biológicas

Gram-negative bacteria produce outer membrane vesicles (OMVs) that contain biologically activeproteins and perform diverse biological processes. In the last few decades the OMVs have been used in the development of acellular vaccines in a variety of pathogens both for human and veterinary use. Brucella is an intracellular pathogen capable of produce acute and chronic infections in wide variety of mammals and it causes a worldwide spread zoonosis called brucellosis. Our previous work showed that the TAM (Translocation and Assembly Module) inner membrane component (∆mapB) is required for the integrity of the OM of Brucella suis and production of higher amount of proteins associated to OMVs fraction. In this work, we characterized the OMVs produced by B. suis M1330 (wt) and B. suis ∆mapB and evaluated their immunogenicity. OMVs were obtained by ultracentrifugation of clarified culture supernatants from both strains. The size of the vesicles was analysed by dynamic light scattering (DLS)and we found that they were similar (around 40 nm diameter) and stable when stored at 4°C. In order to characterize the protein composition and differences in abundance, LFQ proteomic assay was achieved.104 hits were detected in total and the vast majority corresponded to OM and periplasmic proteins. In particular, OMV∆mapB showed 14 hits differentially expressed which showed high predicted antigenicity. Female Balb/c mice were immunized intramuscularly (i.m.) with OMVwt, OMVΔmapB or saline at 0 and 30 days. One week after last immunization serum, bronchoalveolar lavage, feces and saliva samples were obtained to measure OMV-specific antibodies. Vaccination with both OMVs induced serum specific IgG. Sera from OMV∆mapB vaccinated animals reached higher IgG titers than OMVwt group. In addition, OMV∆mapB mice showed high levels of serum specific IgG1, IgG2a and IgA, while in OMVwt vaccinated animals only low levels of specific IgA were detected. Serum specific antibodies from OMVwt and OMV∆mapB vaccinated mice reduced B. suis adherence and invasion to A549 cells, indicating the ability of the antibodies to neutralize Brucella infection. Moreover, serum obtained from both groups showedopsonizing capacity of antibodies since when preincubated with Brucella, CFU/ml obtained from lysates of infected macrophages was increased. Taken together these results show that vaccination with B. suis wt and ∆mapB OMVs induced systemic and mucosal specific humoral immune response, which may contribute to prevent Brucella mucosal entry and its dissemination