Intestinal bacterium beats host defence

Interferon-inducible guanylate-binding proteins (GBPs) have recently become recognized as key players in immunity to pathogens. Feng Shao and colleagues now report a mechanism by which the intestinal pathogen Shigella flexneri counteracts this host defence. They show in mice that the S. flexneri effector E3 ligase IpaH9.8 ubiquitinates multiple GBPs to initiate their proteosomal degradation during infection. Absence or disruption of IpaH9.8 activity enabled GBPs to limit bacterial growth. This targeting of host GBPs by IpaH9.8 represents a novel bacterial virulence strategy in bacterial pathogens.