Abstract

The activation and nuclear translocation of NF-kB and the expression of the pro-inflammatory cytokine genes by macrophages infected with the attenuated Brucella abortus RB51 and virulent 2308 strains were evaluated. pIkBα and NF-kB were determined by immunoblot, and cytokines IFN-g and IL12 mRNA were determined by reverse transcriptase polymerase chain reaction (qPCR) and translocation of NF-kB protein to the nucleus was determined by electrophoretic mobility shift assay (EMSA). We demonstrate that the attenuated B. abortus RB51 strain stimulates cells resulting in NF-kB activation and nuclear translocation, during experimental infection in macrophages J774A.1 which induced a pro-inflammatory response producing IL-6, 12 TNF-s INF-g and iNOS. The virulent strain B. abortus 2308 also stimulated the cells but induced a p50 homodimer of NF-kB which is inactive. The p50 homodimer of NF-kB binds to DNA, and thus blocked the activation of pro-inflammatory cytokines genes. Therefore, an evasion mechanism of the strain 2308 is to produce an inactive homodimer of NF-kB which does not give rise to pro-inflammatory response to eliminate the bacteria.

Key words: Brucella abortus, RB51, 2308, NF-kB, transduction signals.