pH‐Responsive Biomineralized Probiotic for Self‐Amplifying Mucosal Vaccination: Gut‐Engineered Antigen Factories Drive Targeted Cervical Tumor Regression

Abstract Therapeutic vaccines against cervical cancer critically depend on sustained high‐level HPV antigen production and prolonged antigen exposure. However, suboptimal antigen bioavailability and rapid systemic clearance remain key barriers to achieving robust vaccine efficacy. Here, we engineer an oral biohybrid vaccine using pH‐responsive biomineralized Bacillus subtilis (B‐BS/E7@M) to establish gut‐based antigen factories for sustained HPV16 E7 production. The calcium phosphate mineral coating confers gastric acid resistance (78.9% survivability vs. 9.1% uncoated) and synergizes with probiotic‐mucosa interactions to prolong intestinal retention (96 h, 4 × controls), enabling >4‐day antigen persistence and markedly enhances oral bioavailability. This system elicits coordinated immune activation: mucosal priming through germinal center expansion and APC maturation elevates IgG, IgA, and T‐cell subsets—including total T cells, cytotoxic T cells, and effector memory T cells—from day 21 onward. Systemic CD8 + T‐cell activation via cross‐presentation enhances central and effector memory T cells, promoting tumor infiltration and resulting in 64% tumor suppression ( p < 0.001) with 50% complete remission in TC‐1 models. Mechanistic studies pinpoint gut‐orchestrated cytotoxic T cell clonal expansion as the dominant effector pathway. By bridging synthetic biology with stimuli‐responsive biomaterials, this work pioneers a paradigm of living biotherapeutics—self‐replicating, mucosa‐deployable systems for precision cancer immunotherapy.