DUAL TARGETING OF RFAP AND FIMH IMPAIRS AIEC INTRACELLULAR SURVIVAL AND LIMITS OMV-DEPENDENT IL-23/PTH17 AXIS ACTIVATION, OFFERING A NOVEL THERAPEUTIC STRATEGY FOR CROHN¿S DISEASE

Crohn’s disease (CD) is a chronic inflammatory disorder characterized by an aberrant inflammatory response against a dysbiotic gut microbiota. Especially, intestinal enrichment of the adherent-invasive Escherichia coli strain (AIEC), together with a dysregulated activation of the IL-23/pTh17 axis, is a distinctive feature of CD. In this context, current therapies primarily suppress the exaggerated inflammation without directly targeting AIEC, and the only AIEC-based approach under investigation is the inhibition of FimH, which mediates adhesion to intestinal epithelial cells. However, whether FimH inhibitors also affect other key steps of AIEC-host interaction, such as intramacrophagic replication, the associated excessive TNF-α secretion, and especially the marked activation of the IL-23/pTh17 axis, remains unknown. Therefore, here we aimed to characterize the pleiotropic activity of specific AIEC virulence determinants to assess whether their simultaneous targeting can prevent the cascade of pathogenic events leading to chronic inflammation. To this aim, we generated and functionally characterized single and double mutants in the LF82 strain, focusing on ΔfimH, ΔrfaP, and ΔybaT for their specific inhibitory effect on distinct host-AIEC pathogenic interactions. Our functional analysis revealed that the ΔrfaPΔfimH double mutant strongly impairs intracellular persistence within macrophages and dendritic cells and, most notably, completely abolished intracellular survival within intestinal epithelial cells. Consistently, the associated pro-inflammatory response — including IL-8, CCL20, TNF-α, and the pTh17-polarizing cytokine IL-23/IL-1β, was markedly reduced in response to ΔrfaPΔfimH double mutant strain. Remarkably, we demonstrated for the first time that OMVs released by LF82 are sufficient to drive the pathogenic skewing of protective cTh17 cells into pathogenic IFN-γ-producing Th17 cells, thereby revealing a previously unrecognized mechanism through which AIEC promotes mucosal immune dysregulation. Strikingly, OMVs derived from the ΔrfaPΔfimH double mutant displayed a reduced ability to induce pTh17 generation. In conclusion, our study strongly proves that dual targeting of RfaP and FimH represents a novel and highly promising therapeutic strategy to simultaneously impair key mechanisms of AIEC virulence and to attenuate the exaggerated inflammatory response that characterizes CD patients.