Propionibacterium acnes host cell tropism contributes to vimentin-mediated invasion and induction of inflammation

Summary The contribution of the human microbiota to health and disease is poorly understood. Propioni- bacterium acnes is a prominent member of the skin microbiota, but is also associated with acne vulgaris. This bacterium has gained recent attention as a potential opportunistic pathogen at non-skin infection sites due to its association with chronic pathologies and its isolation from diseased prostates. We performed comparative global-transcriptional analyses for P. acnes infec- tion of keratinocytes and prostate cells. P. acnes induced an acute, transient transcriptional inflam- matory response in keratinocytes, whereas this response was delayed and sustained in prostate cells. We found that P. acnes invaded prostate epi- thelial cells, but not keratinocytes, and was detect- able intracellularly 7 days post infection. Further characterization of the host cell response to infec- tion revealed that vimentin was a key determinant for P. acnes invasion in prostate cells. siRNA- mediated knock-down of vimentin in prostate cells attenuated bacterial invasion and the inflammatory response to infection. We conclude that host cell tropism, which may depend on the host protein vimentin, is relevant for P. acnes invasion and in part determines its sustained inflammatory capac- ity and persistence of infection.