This study was conducted to evaluate the immunogenicity and protective efficacy of a DNA vaccine encoding Brucella abortus Cu,Zn superoxide dismutase (SOD). Intramuscular injection of plasmid DNA carrying the SOD gene (pcDNA-SOD) into BALB/c mice elicited both humoral and cellular immune responses. Animals injected with pcDNA-SOD developed SOD-specific antibodies which exhibited a dominance of immunoglobulin G2a (IgG2a) over IgG1. In addition, the DNA vaccine elicited a T-cell-proliferative response and also induced the production of gamma interferon, but not interleukin-10 (IL-10) or IL-4, upon restimulation with either recombinant SOD or crude Brucella protein, suggesting the induction of a typical T-helper-1-dominated immune response in mice. The pcDNA-SOD (but not the control vector) induced a strong, significant level of protection in BALB/c mice against challenge with B. abortus virulent strain 2308; the level of protection was similar to the one induced by B. abortus vaccine strain RB51. Altogether, these data suggest that pcDNA-SOD is a good candidate for use in future studies of vaccination against brucellosis.
In the development of vaccines capable of providing immunity against brucellosis, Cu-Zn superoxide dismutase (SOD) has been demonstrated to be one of the protective immunogens of Brucella abortus. In an earlier study, we provided strong evidence that intramuscular injection with a plasmid DNA carrying the SOD gene (pcDNA-SOD) was able to induce a protective immune response. The present study was designed to characterize T-cell immune responses after an intraspleen (i.s.) vaccination of BALB/c mice with pcDNA-SOD. Animals vaccinated with pcDNA-SOD did not develop SOD-specific antibodies, at least until week 4 after immunization (the end of the experiment), and in vitro stimulation of their splenocytes with either recombinant Cu-Zn SOD or crude Brucella protein induced the secretion of gamma interferon (IFN-␥), but not interleukin-4, and elicited the induction of cytotoxic-T-lymphocyte activity. Upon analyzing the SOD-specific T-cell responses, the pcDNA-SOD vaccination was found to be stimulating both CD4؉ -and CD8 ؉ -T-cell populations. However, only the CD4 ؉ population was able to produce IFN-␥ and only the CD8 ؉ population was able to induce cytotoxic activity. Nevertheless, although i.s. route vaccination induces a significant level of protection in BALB/c mice against challenge with the virulent B. abortus strain 2308, vaccination by the intramuscular route with a similar amount of plasmid DNA does not protect. Based on these results, we conclude that i.s. immunization with pcDNA-SOD vaccine efficiently induced a Th1 type of immune response and a protective response that could be related to IFN-␥ production and cytotoxic activity against infected cells by SOD-specific CD4 ؉ and CD8 ؉ T cells, respectively.Brucellosis is a zoonotic disease that is endemic in some regions of the world. In human populations, the major cause of the disease is Brucella melitensis, but several cases have also been attributed to Brucella abortus, which otherwise primarily affects bovines. Because of the economic losses to the cattle industry caused by B. abortus, as well as because of the zoonotic infections by these bacterial species (8), great efforts are being made to eradicate bovine brucellosis all over the world. In order to achieve this objective, vaccine strains of B. abortus 32) have been used with relatively good results. However, even these vaccine strains are far from ideal, since they present some disadvantages, e.g., causing reactions in humans, inducing abortion in pregnant cattle, and showing a likelihood of changing to a virulent form (33).Brucella is an intracellular pathogen; therefore, cellular immune response is critical in generating protection against infection (42). It is well documented that gamma interferon (IFN-␥) production by CD4 ϩ T cells is essential to the protective response; IFN-␥ activates macrophages by enhancing their ability to kill bacteria (18,20,34,43). It is still unknown if there is a correlation between the degree of in vitro cytotoxic-Tlymphocyte (CTL) activity and in vivo levels of pro...
El sector agrícola es de gran importancia para la estrategia comercial latinoamericana, siendo Estados Unidos uno de sus principales destinos. Los requisitos relativos a calidad e inocuidad alimentarias de dicho mercado se han incrementado y se reflejan en un número creciente de medidas no arancelarias. El incumplimiento de estas puede llevar al rechazo del cargamento en la frontera, lo que implica pérdidas importantes. El objetivo del presente artículo es contribuir a ampliar el conocimiento acerca de los rechazos de exportaciones agrícolas por incumplimiento de normas relativas a calidad e inocuidad alimentarias. Para ello se consideró específicamente el caso de las hortalizas y frutas frescas procedentes de América Latina en la frontera de Estados Unidos.
SUMMARYBrucellosis, a disease caused by the intracellular facultative bacteria Brucella abortus, is a widely distributed zoonosis throughout the world, affecting mainly cattle and causing sterility in males and abortion in pregnant females. Protection against B. abortus relies on the activation of cellular immunity involving lymphocytes T CD4 + , subset Th1, secreting gamma-interferon (γ-INF), a cytokine stimulatings macrophage bactericidal activity and cytotoxic activity of lymphocytes TCD8 + , which are able to lyse Brucella infected cells. The main antigenic components of Brucella are lipopolysaccharide (LPS) and proteins, especially superoxide dismutase (SOD) with demonstrated immune potential. Brucellosis spreading is prevented with vaccines using attenuated or inactivated strains of B. abortus, such as strains 19, 45/20 and RB51. On the other hand, several investigators are making efforts to obtain immunity using antigenic structures of Brucella as subcellular vaccines and recently, genetic vaccines based on DNA and RNA molecules. The aim of this review is to give a current overview about brucellosis, its pathogenicity and the clinical syndrome. Firstly, an analysis of the genetic, antigenic and immune characteristics of Brucella is presented. Secondly, the vaccines presently used for prevention and the research on subcellular vaccines are discussed. Finally, the new approach in the vaccine investigation, genetic DNA and RNA vaccines, for Brucella is presented. INTRODUCCIONLa brucelosis es una zoonosis cuya incidencia y prevalencia varían de un país a otro. La infección causada por la especie Brucella abortus es la que más frecuentemente afecta al ganado bovino, causando esterilidad en machos y abortos en hembras preñadas, lo que conduce a graves pérdidas económicas en países en los que es endémica. En países no desarrollados constituye además un problema sanitario para la población humana.B. abortus es una bacteria Gram negativa con un lipopolisacárido (LPS) fuertemente inmunodominante, el que junto con la capacidad de sobrevivir en el interior de células fagocíticas constituyen sus principales factores de virulencia. La infección en humanos conduce a una enfermedad con tendencia a la cronicidad, con fiebre y malestar recurrentes que deterioran su calidad de vida y que además puede presentar complicaciones como artritis, meningitis, entre otras.En el ganado bovino la bacteria se ubica en la placenta y órganos reproductores por su afinidad por el eritritol.La respuesta inmune frente a B. abortus, patógeno intracelular facultativo, depende principalmente de la activación de la inmunidad mediada por células, con la participación de células T CD4 + de tipo Th1, que secretan interferón gama (INF-γ), citoquina que estimula tanto la actividad bactericida de macrófagos como la actividad citotóxica de los linfocitos T CD8 + . Estos últimos son capaces entonces de destruir células infectadas con Brucella.La identificación de proteínas con demostrada capacidad inmune, entre las que se ha identificado la superóxido ...
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