How Intracellular Bacteria Survive: Surface Modifications That Promote Resistance to Host Innate Immune Responses.
Ernst, Robert K.; Guina, Tina; Miller, Samuel I.
[Article] Journal of Infectious Diseases. 179 Sup 2:S326-S330, March 1999.

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: Bacterial pathogens regulate the expression of virulence factors in response to environmental signals. In the case of salmonellae, many virulence factors are regulated via PhoP/PhoQ, a two-component signal transduction system that is repressed by magnesium and calcium in vitro. PhoP/PhoQ-activated genes promote intracellular survival within macrophages, whereas PhoP-repressed genes promote entrance into epithelial cells and macrophages by macropinocytosis and stimulate epithelial cell cytokine production. PhoP-activated genes include those that alter the cell envelope through structural alterations of lipopolysaccharide and lipid A, the bioactive component of lipopoly-saccharide. PhoP-activated changes in the bacterial envelope likely promote intracellular survival by increasing resistance to host cationic antimicrobial peptides and decreasing host cell cytokine production.

(C) Copyright Oxford University Press 1999.