Hybrid Outer Membrane Vesicles with Genetically Engineering for Treatment of Implant‐Associated Infections and Relapse Prevention Through Host Immunomodulation

Abstract Implant‐associated infections (IAIs) are refractory to elimination, and the local immunosuppressive microenvironment (IME) exacerbates therapeutic difficulties, ultimately causing persistence and relapse. Therefore, exploring immunostrengthening treatments holds great promise for reversing IME and thoroughly eradicating chronic or repetitive infections. Bacterial outer membrane vesicles (OMVs) have emerged as potential immunostimulatory candidates; however, they lack active targeting capabilities and cause non‐specific inflammatory side effects. In this study, bone marrow‐derived mesenchymal stem cells (BMSCs) are genetically engineered to overexpress CXCR4 and isolated cell membranes (mBMSC _CXCR4 ) for hybridization with OMVs derived from Escherichia coli ( E. coli ) to produce nanovesicles (mBMSC _CXCR4 @OMV). The resulting mBMSC _CXCR4 @OMV nanovesicles demonstrate excellent bone marrow targeting capability and are effectively taken up by bone marrow‐derived macrophages, triggering the efficient transition to pro‐inflammatory M1 status through TLR/NF‐κB pathway. This alteration promotes innate bactericidal capacity and antigen presentation. Subsequent activation of T and B cells and inhibition of myeloid‐derived suppressor cells (MDSCs) facilitated in vivo adaptive immunity in mouse models. Additionally, mBMSC _CXCR4 @OMV boosted memory B cell and bacteria‐specific antibody responses. Together, these data highlight the potential of mBMSC _CXCR4 @OMV to eradicate complicated IAIs and provide whole‐stage protection against postsurgical relapse, thus marking a significant immunotherapeutic advancement in the post‐antibiotic era.