Flagella-overexpressing bacteria with inducible lysis capability delivering cGAMP intratracheally for enhanced anticancer immunotherapy

Intratracheal administration demonstrates superior therapeutic effectiveness against pulmonary diseases with reduced systemic toxicity, especially for non-small cell lung cancer (NSCLC). However, conventional intratracheally administered drugs struggle to further penetrate into the tumor core from the pulmonary parenchyma due to biological obstacles such as the mucosal barrier and the tumor extracellular matrix. Here, an engineered Salmonella strain named VNP DCX that achieves flagella overexpression and inducible lysis has been developed as an intratracheal delivery vehicle to penetrate biological barriers for intratumoral drug delivery. After intratracheal administration, the enhanced motility and invasive properties of VNP DCX facilitate them to penetrate barriers and colonize orthotopic lung tumors, along with the stimulator of interferon genes (STING) agonist cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) loaded on them. Bacteria remaining in lung tissues are subsequently lysed via the inducible lysis circuit to avoid refractory pneumonia. The combination of STING pathway activation and bacterial overexpressed flagella facilitates tumor-associated macrophage M1 polarization. Additionally, dendritic cells mature, as well as T lymphocytes prime, both of which promote tumor eradication. Therefore, intratracheal motile bacterial carriers are effective in penetrating biological barriers and delivering therapeutic drugs, offering a novel strategy for non-small cell lung cancer immunotherapy.