Anisotropic Masked Mycobacterium Potentiates Amplified Antitumor Trained Immunity via Spleen Targeting and Myelopoiesis Conversion

ABSTRACT

Cancer progression involves systemic immune suppression and tumor recurrence facilitated by increased splenic protumoral myelopoiesis. To address this clinical challenge, we developed an engineered Trojan Mycobacterium as a trained immunity (TI)‐mediated splenic myelopoiesis converter (t‐SMC). This design provides an intravenously injectable anisotropic TI inducer with an aspect ratio of 3.6 for preferential spleen targeting and cellular uptake via a Mycobacterium “peeling‐off and masking‐up” strategy with human serum albumin incorporating an enzyme‑activatable Toll‑like receptor 7/8 agonist that boosts TI activation. t‐SMC induces antitumoral myelopoiesis with metabolic and epigenetic reprogramming in splenic macrophages. This shift toward antitumoral myelopoiesis markedly enriches the tumor microenvironment with inflammatory myeloid effectors in an E.G7‐OVA model, and the adoptive transfer of splenic myeloid cells confirmed the TI‐driven antitumor effect. Furthermore, comparative analysis revealed that the bacterial scaffold (alb‐Mycobac) initiates myeloid reprogramming, but only the integrated TLR7/8 agonist (t‐SMC) crosses the therapeutic threshold for tumor regression. In the MC38 surgical recurrence model, preoperative t‐SMC combined with standard adjuvant αPD‐L1 plus oxaliplatin achieved complete inhibition of recurrence in 50% of treated mice (3 of 6) with 62.5% long‐term survival, establishing TI priming as a translation‐ready preoperative adjuvant that converts immune‐checkpoint non‐responders into responders.