S9 - Symposium 3

Outer membrane vesicles derived from a Brucella mutant: toward a Safe and effective brucellosis vaccine

Muñoz González, Florencia ^1,2, - Bialer, Magali G. ³ - Cerutti, Maria Laura ⁴ - Estein, Silvia M. ⁵ - Ramis, Lila ³ - Baldi, Pablo C. ^1,2 - Zorreguieta, Ángeles ^3,6 - Ferrero, Mariana C. ^1,2

1) Facultad de Farmacia y Bioquímica, Cátedra de Inmunología, UBA, Argentina
2) Instituto de Estudios de la Inmunidad Humoral (IDEHU), CONICET-UBA, Buenos Aires, Argentina
3) Fundación Instituto Leloir (FIL), IIBBA-CONICET (CONICET-FIL), Buenos Aires, Argentina
4) Centro de Rediseño e Ingeniería de proteínas (CRIP), UNSAM, Buenos Aires, Argentina
5) Laboratorio de Inmunología, Departamento de Sanidad Animal y Medicina Preventiva (SAMP), Centro de Investigación Veterinaria Tandil (CIVETAN-CONICET-CICPBA), Facultad de Ciencias Veterinarias (FCV), UNCPBA, Tandil, Buenos Aires, Argentina
6) Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires, Argentina.
Contacto: ferrerom@ffyb.uba.ar

MapB, the Brucella suis homolog of TamB, plays a critical role in maintaining outer membrane integrity and facilitating protein translocation. Its deletion disrupts outer membrane homeostasis, altering both the composition and biogenesis of outer membrane vesicles (OMVs), and consequently modifying their structure and immunogenic content.

Porcine brucellosis remains a challenging zoonotic disease, with no approved vaccines available for human or swine use. This study evaluated the vaccine potential of OMVs derived from B. suis 1330 (wild-type) and its isogenic ΔmapB mutant in a murine model. OMVs were isolated and characterized by electron microscopy, dynamic light scattering (DLS), SDS-PAGE, and proteomic analysis, revealing spherical particles (90–130 nm) enriched in known Brucella immunogens.

Mice were immunized intramuscularly with OMVs from both strains. The ΔmapB OMVs elicited significantly higher serum IgG levels compared to wild-type OMVs. Antibodies from both groups reduced B. suis adherence and invasion of lung epithelial cells and enhanced phagocytosis by macrophages. Moreover, splenocytes from ΔmapB OMVs–immunized mice secreted increased levels of IL-17 and IFN-γ, indicating a more robust Th1-type immune response.

Immunization with either OMVs preparation conferred protection against intratracheal challenge with virulent B. suis. However, ΔmapB OMVs provided superior protection following intraperitoneal infection. These findings demonstrate that ΔmapB OMVs are highly immunogenic and capable of inducing both mucosal and systemic immunity, supporting their potential as a safe and effective acellular vaccine candidate against porcine brucellosis.