NFκB is differentially activated in macrophages from J774A.1 cell line infected with vaccine or virulent strains of Brucella abortus

Abstract

The activation and nuclear translocation of NF-B and the expression of the pro-inflammatory cytokine
genes by macrophages infected with the attenuated Brucella abortus RB51 and virulent 2308 strains
were evaluated. pIBα and NF-B were determined by immunoblot, and cytokines IFN- and IL12 mRNA
were determined by reverse transcriptase polymerase chain reaction (qPCR) and translocation of NF-B
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-B 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-B which is inactive. The p50 homodimer of NF-B 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-B which does not give rise to
pro-inflammatory response to eliminate the bacteria.