The Rickettsia Surface Protein OmpB is Critical for Virulence and Evasion of Autophagy

Rickettsia are obligate intracellular bacteria that evade antimicrobial autophagy in the host cell cytosol by unknown mechanisms. Other cytosolic pathogens block different steps of autophagy targeting, including the initial step of polyubiquitin coat formation. One mechanism of evasion is to mobilize actin to the bacterial surface. Here, we show that actin mobilization is insufficient to block autophagy recognition of the pathogen Rickettsia parkeri. Instead, R. parkeri employs outer membrane protein B (OmpB) to block ubiquitylation of bacterial surface proteins, including OmpA, and subsequent recognition by autophagy receptors. Although OmpB is dispensable for bacterial growth in endothelial cells, it is essential for R. parkeri to block autophagy in macrophages and to colonize mice. Our results indicate that OmpB acts as a protective shield to obstruct autophagy recognition, revealing a distinctive bacterial mechanism to evade antimicrobial autophagy.