Regulation of the mitogen-activated protein kinases by Brucella spp. expressing a smooth and rough phenotype: relationship to pathogen invasiveness.

By comparing smooth wild-type Brucella spp. to their rough mutants, we show that the LPS O chain restricted the activation of the ERK1/2 and p38 mitogen-activated protein kinase (MAPK) pathways, thus preventing the synthesis of immune mediators that regulate host defense. We conclude that the MAPKs are a target for immune intervention by virulent smooth Brucella.