A bio-orthogonally engineered probiotic-T cell chimera amplifies adoptive cell therapy through spatial DC-T cell immune licensing.
TL;DR
Mechanistically, T-FOLactis promoted dendritic cell (DC)-T cell proximity and established a spatially organized immune-licensing niche that amplified the functional impact of FOLactis-induced inflammatory cues, including IL-18, establishing a modular cell-surface engineering strategy for augmenting ACT in colorectal cancer through coordinated immune network engagement.
Abstract
Adoptive cell transfer (ACT) has achieved durable clinical responses in hematological malignancies, yet remains limited in solid tumors owing to poor T cell infiltration, inadequate persistence, and tumor-driven immunosuppression. Here, we report a bio-orthogonally engineered probiotic-T cell chimera (T-FOLactis) that creates a mutually reinforcing cellular-microbial system, in which FOLactis, an engineered Lactococcus lactis expressing a Flt3L-OX40L fusion protein, provides localized immunostimulatory cues to enhance T cell activation and effector function, while adoptively transferred T cells serve as cytotoxic effectors and mobile carriers that facilitate delivery of the bacterial payload to the tumor microenvironment. Using strain-promoted azide-alkyne cycloaddition chemistry, FOLactis bacteria were covalently anchored onto the surface of T cells, generating a cell-bound platform for spatially restricted immune modulation. In syngeneic colorectal cancer models, T-FOLactis reduced tumor burden by 78.1% compared with saline-treated controls and by 65.0% relative to conventional ACT, while prolonging median survival from 22 to 46 d without overt systemic toxicity. Mechanistically, T-FOLactis promoted dendritic cell (DC)-T cell proximity and established a spatially organized immune-licensing niche that amplified the functional impact of FOLactis-induced inflammatory cues, including IL-18. This spatial configuration was associated with enhanced coupling of cytokine availability, DC maturation, local co-stimulation and cytotoxic CD8+ T cell effector programming. IL-18 blockade impaired this licensing program and reduced therapeutic benefit, supporting IL-18 as a key functional mediator within the DC-T cell licensing niche. Together, these findings establish a modular cell-surface engineering strategy for augmenting ACT in colorectal cancer through coordinated immune network engagement.