Phage therapy targeting DNA-encapsulated membrane vesicle-producing intestinal symbiotic Klebsiella pneumoniae ameliorates autoimmune disease.

Autoimmune hepatitis (AIH) is a progressive and currently incurable inflammatory liver disorder. Accumulating evidence suggests that intestinal Klebsiella pneumoniae may contribute to AIH. However, the specific bacterial features underlying its role remain unclear. We isolated 32 strains of K. pneumoniae from both healthy and AIH patients. Genomic and phenotypic analyses identified a unique strain, KpA4-1 from an AIH patient, distinguished by its production of membrane vesicles (MVs) encapsulating plasmid DNA (p2). Administration of p2-containing MVs in mice elevated serum liver enzymes and antinuclear antibodies (ANA), indicating liver injury and autoimmune activation. Oral administration of KpA4-1 in AIH mice exacerbated AIH pathology, evidenced by elevated liver enzymes, increased ANA titers, and enhanced hepatic CD8 + T cell infiltration. Mechanistically, KpA4-1 activated the cGAS-STING signaling pathway that potentiated hepatic inflammation in AIH mice. The pivotal role of the p2 was further validated by attenuated AIH pathology in mice treated with KpA4-1Δp2 or bacteriophage therapy targeting KpA4-1. Collectively, these findings uncover a novel mechanism by which the intestinal K. pneumoniae exacerbates AIH via DNA-encapsulated MVs, highlighting their potential as diagnostic or therapeutic targets.