Anti-virulence Strategy against Brucella suis: Synthesis, Biological Evaluation and Molecular Modeling of Selective Histidinol Dehydrogenase Inhibitors

Abstract

In the facultative intracellular pathogen Brucella suis, histidinol dehydrogenase (HDH) activity, catalyzing the last step in histidine biosynthesis, is essential for intramacrophagic replication. The inhibition of this virulence factor by substituted benzylic ketones was a proof of concept that disarming bacteria leads to inhibition of intracellular bacterial growth in macrophage infection. This work describes the design, synthesis and evaluation of 19 new potential HDH inhibitors, using a combination of classical approaches and docking studies. The IC₅₀-values of these inhibitors on HDH activity were in the nanomolar range, and several of them showed a 70–100% inhibition of Brucellagrowth in minimal medium. One selected compound yielded a strong inhibitory effect on intracellular replication of B. suis in human macrophages at concentrations as low as 5 μM, with an overall survival of intramacrophagic bacteria reduced by a factor 10³. Docking studies with two inhibitors showed a good fitting in the catalytic pocket and also interaction with the second lipophilic pocket binding the cofactor NAD⁺. Experimental data confirmed competition between inhibitors and NAD⁺ at this site. Hence, these inhibitors can be considered as promising tools in the development of novel anti-virulence drugs.