Protection of BALB/c Mice againstBrucella abortus544 Challenge by Vaccination with Bacterioferritin or P39 Recombinant Proteins with CpG Oligodeoxynucleotides as Adjuvant

Abstract

The P39 and the bacterioferrin (BFR) antigens of Brucella melitensis 16M were previously identified as T dominant antigens able to induce both delayed-type hypersensivity in sensitized guinea pigs and in vitro gamma interferon (IFN-␥) production by peripheral blood mononuclear cells from infected cattle. Here, we analyzed the potential for these antigens to function as a subunitary vaccine against Brucella abortus infection in BALB/c mice, and we characterized the humoral and cellular immune responses induced. Mice were injected with each of the recombinant proteins alone or adjuvanted with either CpG oligodeoxynucleotides (CpG ODN) or non-CpG ODN. Mice immunized with the recombinant antigens with CpG ODN were the only group demonstrating both significant IFN-␥ production and T-cell proliferation in response to either Brucella extract or to the respective antigen. The same conclusion holds true for the antibody response, which was only demonstrated in mice immunized with recombinant antigens mixed with CpG ODN. The antibody titers (both immunoglobulin G1 [IgG1] and IgG2a) induced by P39 immunization were higher than the titers induced by BFR (only IgG2a). Using a B. abortus 544 challenge, the level of protection was analyzed and compared to the protection conferred by one immunization with the vaccine strain B19. Immunization with P39 and CpG ODN gave a level of protection comparable to the one conferred by B19 at 4 weeks postchallenge, and the mice were still significantly protected at 8 weeks postchallenge, although to a lesser extent than the B19-vaccinated group. Intriguingly, no protection was detected after BFR vaccination. All other groups did not demonstrate any protection.Brucella species are facultative intracellular gram-negative bacterial pathogens that infect both phagocytic and nonphagocytic cells (42). Brucella abortus causes abortion and infertility in cattle and also various chronic zoonotic infections in humans (8,42). The intracellular localization of these bacteria implies that the immunity against Brucella requires a cell-mediated immune response, which makes the Th1 arm of the response very crucial for controlling the infection (44).Brucella abortus strain B19 is one of the most commonly used attenuated live vaccines against bovine brucellosis and induces high level of protection in cattle (15). The presence of smooth lipopolysaccharide in the vaccine strain B19 may interfere with the discrimination between infected and vaccinated individuals (32) and impair the test and slaughter strategy. Moreover, this strain can cause abortion when administered to pregnant cattle (9) and is still fully virulent for humans (42). In order to avoid these drawbacks, alternative vaccination approaches are needed. Among these, subcellular vaccines able to induce protective Th1 cell-mediated immune response are being developed. Recombinant antigens of Brucella spp. such as HtrA (40), GroEL (2, 30, 34), GroES (34), Cu,Zn superoxide dismutase (SOD) (47, 49), YajC (52), UvrA (34), and L7 and L12 (37) have been sh...

Effect of CpG oligodeoxynucleotide on the immune response of 28 kDa outer membrane protein ofBrucella

“…The significant rise (P B0.001) in the titre of IgG in mice of group 1 compared to group 2 and 3 supports the effect of adjuvant (CpG ODN). Our results are in agreement with the previous report of Klinman et al (2004) and Al-Mariri et al (2001). The mice immunised with rOMP28'CpG showed relative predominance of IgG2a over IgG1, however, IgG1 was relatively predominant in rOMP28 immunised mice.…”

“…This suggested the role of CpG ODN in antigen-specific isotype class switching, when coadministered with rOMP28 and induction of Th1 arm of immune response (Figure 1B and C). This corroborated to the finding of Al-Mariri et al (2001) and Klinman et al (1999).…”

“…This implies the requirement of a cell-mediated immune response against Brucella, which makes the Th1 arm of the response critical for control of brucellosis (Splitter et al 1996). Several Brucella antigens such as p39 (Al-Mariri et al 2001), L7/L12 (Mallick et al 2007), YaJC (Vemulapalli et al 2000), OMP31 (Cassataro et al 2005) have been studied for their immunogenicity and protective ability with promising results. In general, the recombinant protein vaccines stimulate Th2 cells resulting in strong humoral responses.…”

Immunization with Recombinant Brucella Species Outer Membrane Protein Omp16 or Omp19 in Adjuvant Induces Specific CD4 + and CD8 + T Cells as Well as Systemic and Oral Protection against Brucella abortus Infection

“…utilizing numerous proteins (2,12,15,25,36). Most of the studies have shown satisfying results in animal models but no clear prospect for further experimentation in humans.…”

Evaluation of Immunogenicity of Dna Vaccine Coding Outer Membrane Protein 31 (Omp31) of Brucella Melitensis in Mice.

“…For challenging purpose, B.melitensis 16 M was used (obtained from vet. Sera vacci Rec Institute, Cairo, Egypt) and was cultured under optimal conditions in tryptose soya agar supplemented with yeast extract 10 g/ lml (Oxoid, England) incubated overnight at 37°C for 72 hrs in 5% Co 2 to ensure sufficient cell density (10). The obtained bacteria were harvested and suspended in PBS and the abundance was adjusted to be 1x10 5 CFU/200µl for protection experiment.…”