Brucellosis, in particular infections with Brucella abortus, Brucella melitensis or Brucella suis, remains a significant human health threat in many areas of the world. The persistence of pathogenic Brucella spp. in domestic livestock or free-ranging wildlife remains unresolved, despite decades of regulatory efforts worldwide. Although vaccination is probably the most economic control measure, administration of currently available vaccines alone is not sufficient for elimination of brucellosis in any host species. Complacency in brucellosis control programs usually results in failure, or at best, limited reductions in disease prevalence or incidence of human infections. New brucellosis vaccines with high efficacy and safety are needed that address the diversity in host species and can be more widely applied under field conditions. Development of safer and more efficacious vaccines alone, or combined with enhancements or increased emphasis on other regulatory program components, could have tremendous impac...

Essential role of vaccines in brucellosis control and eradication programs for livestock

Brucella spp. are zoonotic, facultative intracellular pathogens, which cause animal and human disease. Animal disease results in abortion of fetuses; in humans, it manifests flu-like symptoms with an undulant fever, with osteoarthritis as a common complication of infection. Antibiotic regimens for human brucellosis patients may last several months and are not always completely effective. While there are no vaccines for humans, several licensed live Brucella vaccines are available for use in livestock. The performance of these animal vaccines is dependent upon the host species, dose, and route of immunization. Newly engineered live vaccines, lacking well-defined virulence factors, retain low residual virulence, are highly protective, and may someday replace currently used animal vaccines. These also have possible human applications. Moreover, due to their enhanced safety and efficacy in animal models, subunit vaccines for brucellosis show great promise for their application in livestock and humans. This review summarizes the progress of brucellosis vaccine development and presents an overview of candidate vaccines.

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Progress in Brucella vaccine development

▪ Nacido en Cartagena (Murcia), en noviembre de 1954. ▪ Licenciado en Ciencias Químicas por la Universidad de Murcia, Catedrático de Física y Química, Divulgador Científico freelance, Escritor, y Conferenciante. ▪ Con 35 años de experiencia docente, ejerciendo como profesor. ▪ A lo largo de su dilatada carrera docente, ha desempeñado cargos de responsabilidad en la gestión de Centros Escolares, tales como Director (7 años), Jefe de Estudios (2 años), Jefe de Departamento de Física y Química (20 años), miembro del Consejo Escolar de Instituto y miembro del Consejo del Centro de Profesores y Recursos de Cartagena (11 años). ▪ Presentación de comunicaciones y ponencias en 28 Congresos, Jornadas y Seminarios. ▪ Ha sido durante 13 años tutor del segundo ciclo del curso de Aptitud Pedagógica de Educación Secundaria, organizado por el Instituto de Ciencias de la Educación, de la Universidad de Murcia y la Universidad Complutense de Madrid. ▪ También ha sido, durante 1 año, tutor de la fase de prácticas del Máster de Profesor de Educación Secundaria, organizado por el Instituto de Ciencias de la Educación, de la Universidad de Murcia.

Curriculum Vitae for

Brucella abortus S19 and RB51 strains have been successfully used to control bovine brucellosis worldwide; however, currently, most of our understanding of the protective immune response induced by vaccination comes from studies in mice. The aim of this study was to characterize and compare the immune responses induced in cattle prime-immunized with B. abortus S19 or RB51 and revaccinated with RB51. Female calves, aged 4 to 8 months, were vaccinated with either vaccine S19 (0.6–1.2 x 1011 CFU) or RB51 (1.3 x 1010 CFU) on day 0, and revaccinated with RB51 (1.3 x 1010 CFU) on day 365 of the experiment. Characterization of the immune response was performed using serum and peripheral blood mononuclear cells. Blood samples were collected on days 0, 28, 210, 365, 393 and 575 post-immunization. Results showed that S19 and RB51 vaccination induced an immune response characterized by proliferation of CD4+ and CD8+ T-cells; IFN-ɣ and IL-17A production by CD4+ T-cells; cytotoxic CD8+ T-cells; IL-6 secretion; CD4+ and CD8+ memory cells; antibodies of IgG1 class; and expression of the phenotypes of activation in T-cells. However, the immune response stimulated by S19 compared to RB51 showed higher persistency of IFN-ɣ and CD4+ memory cells, induction of CD21+ memory cells and higher secretion of IL-6. After RB51 revaccination, the immune response was chiefly characterized by increase in IFN-ɣ expression, proliferation of antigen-specific CD4+ and CD8+ T-cells, cytotoxic CD8+ T-cells and decrease of IL-6 production in both groups. Nevertheless, a different polarization of the immune response, CD4+- or CD8+-dominant, was observed after the booster with RB51 for S19 and RB51 prime-vaccinated animals, respectively. Our results indicate that after prime vaccination both vaccine strains induce a strong and complex Th1 immune response, although after RB51 revaccination the differences between immune profiles induced by prime-vaccination become accentuated.

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R.J. Morton

Papers

Effects of challenge dose on the clinical and immune responses of cattle vaccinated with reduced doses of Brucella abortus strain 19.