Frequent Exposure of Mice to Crude Brucella abortus Proteins Down‐regulates Immune Response

Abstract

Mice repeatedly immunized via the intraperitoneal route with a Brucella abortus antigen lost their ability to develop a strong in vitro lymphoproliferative response. This result correlates with a decreased tendency of the lymphoid population to produce interferon-gamma when stimulated in culture with the immunizing antigen. With respect to the humoral response, as the number of immunizations increased, the animals produced more specific immunoglobulin M and immunoglobulin G1 antibodies. It is postulated that the long-term exposure of an animal to Brucella antigen changes the nature of the immune response from a T-cell-mediated response to a humoral response favouring the establishment of the disease.

Cloning, expression and immunogenicity of the translation initiation factor 3 homologue of Brucella abortus

“…IL-4 was not secreted by lymphocytes from any of the immunization groups (data not shown). This finding is in agreement with our previous study in which immunization of mice intra-footpad with CPBs or B. abortus Cu-Zn SOD did not induce the production of IL-4 (On˜ate and Folch, 1995;On˜ate et al, 2000). We failed to detect IF3-specific antibodies in the serum from mice vaccinated with His-IF3 at seven day postimmunization (data not shown).…”

Intraspleen Delivery of a DNA Vaccine Coding for Superoxide Dismutase (SOD) ofBrucella abortusInduces SOD-Specific CD4+and CD8+T Cells

“…The T cells were stained with monoclonal antibodies against the CD4 (clone GK1.5; isotype, rat Protection experiments. Protection experiments were performed as described previously (26). Briefly, 4 weeks after vaccination, six mice from each group were challenged by intraperitoneal injection of 10 4 CFU of B. abortus 2308.…”

Evaluation of Brucella abortus DNA vaccine by expression of Cu–Zn superoxide dismutase antigen fused to IL-2

“…Single-cell suspensions were prepared from the spleens according to a standard procedure (On˜ate et al, 1999), and erythrocytes were eliminated with ACK lysis solution (150 mM NH 4 Cl, 1 mM Na 2 EDTA [pH 7.3]). Splenocytes were cultured at 37 1C with 5% CO 2 in a 96-well flat-bottom plate at a concentration of 4 Â 10 5 viable cells/well for total T-cell populations in the presence of 4 mg of crude B. abortus RB51 proteins (CBPs) per well, an extract obtained from bacteria subjected to hypertonic salt solution (1 M NaCl with 0.1 M sodium citrate) and sonication (On˜ate et al, 2000); 0.4 mg of purified Cu-Zn SOD (recombinant SOD -rSOD) per well, obtained by a chromatography affinity procedure (On˜ate et al, 2000); 0.25 mg of ConA per well; or no additives (unstimulated control). Splenocytes (total T-cell) were cultured in c-RPMI medium for 3 days and pulsed for 8 h with 0.4 mCi of thymidine (40 Ci/mmol); Amersham, London, UK) per well, and the radioactivity incorporated in the DNA was measured in a liquid scintillation counter.…”

“…Protection experiments were performed as described previously (On˜ate et al, 2000). Briefly, 4 weeks after vaccination, six mice from each group were challenged by intraperitoneal injection of 10 4 CFU of B. abortus 2308.…”