Identification and Characterization of Toxtazins A and B, Two Small Molecule Inhibitors of Virulence Gene Activation in Vibrio cholerae.

Abstract

Discovering how bacteria regulate their virulence mechanisms deepens our understanding of basic pathogenesis and allows us to uncover new potential targets for the treatment of disease. We applied a chemical genetics approach to probe the cellular requirements for virulence gene expression in Vibrio cholerae by targeting the main virulence gene regulator, ToxT. The screen revealed two novel classes of inhibitors, toxtazins A and B. Both reduce cholera toxin production and production of an important ToxT-regulated pilus, the toxin co-regulated pilus. We present evidence that toxtazin A works by inhibiting toxT transcription, and may do this by activating stress pathways in the cell. We also demonstrate that toxtazin B works by inhibiting tcpP transcription, and this may be due to a particular thiol switch in AphB, one of two transcriptional activators required to activate the tcpP promoter. Furthermore, treatment with toxtazin B resulted in a 100-fold reduction in colonization in an infant mouse model of infection. These results add to the growing body of literature indicating that small molecule inhibitors of virulence genes could be developed to treat infections and to learn more about the basic biological mechanisms required for virulence gene regulation.