Commensal bacterial hybrid nanovesicles improve immune checkpoint therapy in pancreatic cancer through immune and metabolic reprogramming

Harnessing the immunomodulatory ability of the microbiota, such as fecal microbiota transplantation (FMT), has emerged as a promising strategy to improve cancer immunotherapy. However, the lack of standardization in fecal material formulation and safety concerns have hindered clinical application. To overcome these limitations, we developed a high-yielding method by hybridizing bacteria protoplast-derived membrane nanovesicles (PDNVs) from three colon bacteria strains that have been associated with favorable responses to immune checkpoint therapy, including Akkermansia muciniphila, Bifidobacterium longum, and Bifidobacterium breve. The resulting hybrid nanovesicles (HNVs) are composed mainly of cytoplasmic membrane proteins inherited from the originating bacteria but lack pyrogens such as lipopolysaccharide and lipoteichoic acid. Our study demonstrated that HNVs have superior targeting abilities to tumors and peripheral lymphoid organs, leading to greater capability in inducing innate immune activation, dendritic cell maturation and antigen presentation, as well as tumor microenvironment reprogramming. Combined with αPD-1 blockade therapy, HNVs efficiently inhibited the tumor growth in multiple pancreatic cancer mouse models, including Panc02 subcutaneous and liver metastatic models, and orthotopic KPC-Luc pancreatic cancer model. Mechanically, HNVs simultaneously activated the innate arm of immunity and inhibited tumor oxidative phosphorylation (OXPHOS) to reshape the tumor immune microenvironment for improved αPD-1 blockade therapy. Notably, HNVs administration gave rise to similar tumor regression rates to oral transfer of a mixture of live or inactivated bacteria during αPD-1 blockade therapy, but with fewer adverse effects such as diarrhea and colon-intestinal inflammation. Our findings present a stable, cost-effective, and safe alternative to live bacteria for regulating tumor microenvironment for improved cancer immunotherapy.