Self-luminous nanoengineered bacteria with the sustained release of interleukin 2 as an in situ vaccine for enhanced cancer immunotherapy.

Bacteria-based in situ vaccination (ISV) has emerged as an effective therapeutic approach by activating anti-tumor immunity. However, inducing immunogenic cell death (ICD) and promoting effector T cell activation remain critical challenges in clinical applications of bacteria-based ISV. Here, we have developed a tumor microenvironment-activated nano-hybrid engineered bacterium as ISV. It was engineered with a blue-light response module (EL222) and self-luminous luminal hyaluronic acid (LHA) nanoparticles. Our study demonstrates that LHA generates local blue light stimulated by hydrogen peroxide, non-invasively activating the engineered Escherichia coli to produce IL-2. The engineered bacteria serve as an immunological adjuvant, promoting dendritic cell maturation, synergistically promoting T cell infiltration, and ultimately triggering a comprehensive activation of the immune system. Furthermore, when combined with the immune checkpoint inhibitor anti-PD-L1, this approach further effectively enhances cancer immunotherapy. Our results provide new strategies and promising prospects for the development of bacteria-based ISV immunotherapy. STATEMENT OF SIGNIFICANCE: This study developed a tumor microenvironment-activated nano-hybrid engineered bacteria (Ec-mIL2@LHA) as in situ vaccine for enhanced cancer immunotherapy. The LHA in bacterial vaccine non-invasively generated blue light upon stimulation by hydrogen peroxide of TME, leading to the sustained release of low-dose IL2 by engineered bacteria. In vitro and in vivo studies have demonstrated the bacterial in situ vaccine induced the immunogenic cell death and promote maturation of dendritic cells, ultimately triggering a comprehensive activation of anti-tumor immunity. After combination with anti-PD-L1, the bacterial in situ vaccine further effectively enhance cancer immunotherapy and inhibit metastasis. We provide a promising strategy to amplify antitumor immune effects by an engineered bacterial vaccine, showing potential clinical applications.