T-cell engaging bispecific outer membrane vesicles (BiTE-OMV) for targeted prostate cancer immunotherapy

Outer membrane vesicles (OMVs) are nanosized vesicles secreted by bacteria. Compared with exosomes, OMVs can be generated much more easily by cells and they offer better biocompatibility than synthetic nanoparticles. In addition, OMVs are more easily genetically modified, allowing the display of various antibody fragments on their surface by introducing plasmids. Through autodisplay technology, we have developed OMVs that display multivalent antibodies for T-cell engagement, termed bispecific T-cell engager (BiTE)-OMVs, for targeted tumor cell lysis. In this study, we targeted the prostate-specific membrane antigen (PSMA) for prostate cancer cell targeting and the CD3 antigen for T-cell targeting. The E. coli was genetically modified with two plasmids containing two single-chain variable fragment (scFv) antibodies, one against each antigen, resulting in BiTE-OMVs that engage T cells with prostate cancer cells. We used genetically engineered bacteria (ClearColiTM), resulting in safer, less immunogenic, and cost-effective BiTE-OMVs. Moreover, the resulting BiTE-OMVs demonstrated enhanced binding affinity of 0.3 nM (anti-PSMA scFv) and 5.8 nM (anti-CD3 scFv) due to the high expression density of the scFvs. The feasibility of BiTE-OMVs was confirmed by achieving 53.2 % PSMA-specific cytotoxicity. These results suggest that BiTE-OMVs could serve as a broadly applicable platform for bi- or multispecific nanomedicines.