Enhancement of host infectivity, immunity, and protective efficacy by addition of sodium bicarbonate antacid to oral vaccine formulation of live attenuated Salmonella secreting Brucella antigens.

In the present study, the importance of sodium bicarbonate antacid as an agent for an orally delivered attenuated Salmonella strain secreting Brucella antigens Cu-Zn superoxide dismutase (SodC) and outer membrane protein 19 (Omp19) as a live vaccine candidate against Brucella infection was investigated. First, Brucella antigens SodC and Omp19 were cloned into a prokaryotic constitutive expression vector, pJHL65. Then secretion of proteins was verified after transformation into an attenuated Salmonella typhimurium (ST) strain, JOL1800 (Δlon, ΔcpxR, Δasd, ΔrfaL), using western blot analysis. Mice were orally inoculated with phosphate-buffered saline (PBS) or with a co-mixture Salmonella secreting each antigens at a 1:1 ratio, each containing 1 × 108 CFU/mouse with and without sodium bicarbonate treatment. For antacid treatment, 1.3% w/v sodium bicarbonate was orally administered 30 min before and immediately after immunization with the Salmonella formulation. Humoral and cell-mediated immune responses were evaluated to investigate the efficacy of sodium bicarbonate in an oral formulation. The results indicated that addition of sodium bicarbonate to the vaccine significantly increased (P < 0.05) levels of anti-Brucella-specific systemic IgG responses, lymphocyte proliferation, and CD4+ T cell responses, indicating induction of a mixed Th1-Th2 response. Immunohistochemical assays and bacterial enumeration in intestinal samples also indicated that administration of sodium bicarbonate enhanced colonization of Salmonella. These results indicate that ingestion of the Salmonella formulation with sodium bicarbonate can enhance colonization of Salmonella and induce a significant protective immune response against Brucella compared with a formulation without sodium bicarbonate. Thus, incorporation of sodium bicarbonate as an antacid buffer is highly recommended for this oral live vaccine.

Evaluation of immune responses in mice and sheep inoculated with a live attenuated Brucella melitensis REV1 vaccine produced in bioreactor.

The Brucella melitensis REV1 vaccine is the most widely employed vaccine for prophylaxis against brucellosis in sheep and goats. The objective of vaccination is disease control in herds or preventing infection in farms. In this study, we produced REV1 vaccine with a protocol, based on the use of liquid medium in a bioreactor, that resulted efficient, safe, relatively fast, and cost-effective. The live attenuated vaccine produced was tested in mice and sheep to investigate its immunogenicity and efficacy. Seventy-two female BALB/c mice were obtained and subdivided in 2 groups, one was stimulated with 1 × 106 colony-forming units (CFUs) of B. melitensis while the other with physiological solution alone and acting as control group. Furthermore, 25 sheep were subdivided into 5 groups: four were inoculated with a B. melitensis dose, ranging from 0.6 × 109 and 3.2 × 109 CFUs and the other was the control group. In addition, a serological diagnosis was performed for sheep by rapid serum agglutination and the complement-fixation test. Immunocompetent cells from both experiment were collected at different times post vaccination and immunostained to evaluate innate and adaptive-immune responses. In mice flow cytometry was used to detect macrophages, T lymphocytes, dendritic cells, memory cells, naïve cells, natural killer cells, major histocompatibility complex type II, B lymphocytes, regulatory T lymphocytes, T helper lymphocytes, cytotoxic T lymphocytes and recently activated CD4+ and CD8+ lymphocytes. In sheep, macrophages, T helper cells, cytotoxic T lymphocytes, regulatory T lymphocytes, dendritic cells, memory cells and naïve lymphocytes, by the same method, were analyzed. The results showed, both in mice and sheep, that the live, attenuated REV1 vaccine stimulated all immunocompetent cells tested, with a balanced innate and adaptive response. In the sheep experiment, the administered vaccine dose was very important because, at the lower doses, immunological tolerance tended to disappear, while, at the highest dose, the immunological tolerance remained active for a long period. In our experimental conditions, the optimal vaccine dose for sheep was 3.2 × 109 CFUs, although a good immune response was found using a dose of 1.6 × 109 CFUs. The vaccine produced in this study could be extensively employed in developing countries to control the brucellosis in sheep and goats.

Confronting the barriers to develop novel vaccines against brucellosis.

Brucellosis is an important zoonotic disease of nearly worldwide distribution. This pathogen causes abortion in domestic animals and undulant fever, arthritis, endocarditis and meningitis in humans. Currently, there is no vaccine licensed for brucellosis in humans. Furthermore, control of brucellosis in the human population relies on the control of animal disease. Available animal vaccines may cause disease and in some cases have limited efficacy. This article discusses recent studies in the development of recombinant protein, DNA and live-attenuated vaccines against brucellosis. Furthermore, we call the attention of the scientific community, government and industry professionals to the fact that for these novel vaccine initiatives to become licensed products they need to be effective in natural hosts and bypass the regulatory barriers present in several countries.

Vacunas en la brucelosis humana / Vaccines in human brucellosis

Hace casi 100 años la brucelosis humana fue considerada por Zammit y Horrocks como una zoonosis, sólo 18 años después que Bruce identificó el agente etiológico de la fiebre de Malta. A lo largo de los años, el avance científico se ha visto encaminado primordialmente al control de la brucelosis animal en los aspectos de diagnóstico y vacunación. En cuanto a la enfermedad en el humano, el progreso más importante ha sido la quimioterapia, aunque en la última década el diagnóstico correcto ha sido un asunto de preocupación general. Las estrategias de erradicación de la brucelosis se divide en tres categorías: 1) Erradicación de la brucelosis animal; 2) Mejoramiento de las medidas de higiene individual y saneamiento y 3) Inmunización. Las vacunas contra la brucelosis han sido desarrolladas a lo largo de tres líneas: 1) vacunas vivas preparadas con cepas atenuadas como B. abortus cepa 19 y B. melitensis cepa Rev.1; 2) células completas inactivadas, como B. abortus cepa 45/20 y B. melitensis H-38 que se administran con adyuvante oleoso y 3) vacunas preparadas con fracciones celulares. Todas ellas han sido usadas ampliamente en el control de la brucelosis en animales y sólo en algunos casos muy particulares en humanos