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The immunomodulatory function of the gastric microbiota in cancer is poorly understood, partly due to the stomach¡¯s acidic environment and limited microbial colonization. Here, by analyzing 68 paired human gastric cancer (GC) samples, we identify Ligilactobacillus salivarius as a commensal bacterium depleted in tumors but enriched in immune checkpoint blockade (ICB) responders. Oral administration of L. salivarius enhances anti-PD-1 efficacy in multiple GC mouse models by promoting pro-inflammatory macrophage activation. Mechanistically, bacterial extracellular vesicles (bEVs) derived from L. salivarius deliver 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase (2,3-BdpM) to tumors, where it activates formyl peptide receptor 1 (FPR1) on macrophages, triggering mitogen-activated protein kinase (MAPK) and nuclear factor ¦ÊB (NF-¦ÊB) signaling. Moreover, 2,3-BdpM augments the cytotoxic activity of chimeric antigen receptor (CAR)-Claudin18.2+ macrophages in an FPR1-dependent manner. These findings describe a microbial-macrophage axis that enhances GC immunotherapy and highlights the translational potential of orally deliverable microbial adjuvants. Graphical abstract Highlights?Intratumoral reduction of L. salivarius correlates with GC immunotherapy efficacy?bEVs derived from L. salivarius enhance immunotherapy efficacy in GC mouse models?2,3-BdpM in bEV triggers pro-inflammatory macrophage remodeling via FPR1?The cytotoxicity of CAR-Claudin18.2+ macrophages was amplified with 2,3-BdpM alone Yu et al. identify Ligilactobacillus salivarius as a gastric commensal enriched in immunotherapy responders. Oral administration enhances anti-PD-1 efficacy by delivering 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase (2,3-BdpM) via bacterial extracellular vesicles (bEVs) to activate pro-inflammatory macrophages through formyl peptide receptor 1 (FPR1), revealing a microbial-macrophage axis that potentiates gastric cancer immunotherapy.

PurposeCancer immunotherapy aims to enhance the immune system¡¯s ability to recognize and eliminate cancer cells, providing a sustained and effective immune response. However, the tumor microenvironment (TME), characterized by an abundance of tumor-associated M2 macrophages and the presence of exhausted or na?ve T cells (non-effector T cells), remains a major barrier to effective immunotherapy. Herein, inflammatory M1 macrophage-derived extracellular vesicles (M1EV) were surface-modified to display interleukin-2 (M1EV_IL2), aiming to develop a multifunctional cancer immunotherapeutic agent capable of modulating both innate and adaptive immune responses.MethodsWe engineered M1EV to label the surface with azide groups through metabolic glycoengineering and developed M1EV_IL2 that displayed IL-2 via bioorthogonal chemistry. M1EV_IL2 were purified by size-exclusion chromatography (SEC) and characterized through comprehensive analyses, including nanoparticle tracking analysis (NTA). In vitro macrophage repolarization and T cell activation were evaluated at the gene-expression level, followed by ex vivo assays assessing T-cell proliferation, cytokine secretion, and activation marker expression.ResultsM1EV_IL2 effectively retained the intrinsic physicochemical properties of EVs while displaying IL-2 stably on its surface. It upregulated M1 macrophage markers, IL-1¦Â and CXCL10, while downregulating the M2 macrophage marker CD206, thereby inducing M2-to-M1 macrophage repolarization. In addition, M1EV_IL2 also activated CD4+ T cells and induced the activation of na?ve CD8+ T cells to effector T cells, leading to enhanced cell proliferation and secretion of antitumor cytokines.ConclusionThese results indicate that M1EV_IL2 has the potential to reshape the tumor immune landscape by simultaneously activating macrophages and T cells, thereby enhancing both innate and adaptive immune responses. Unlike conventional cancer therapies, which directly target tumor cells, M1EV_IL2 is expected to enhance immune responses, potentially mitigating adverse effects while improving therapeutic efficacy. Graphical Abstract

Zhang et al. demonstrate that the expression of a mutated CARMIL2 protein in CD28-deficient mice induces most of the developmental and functional consequences known to result from CD28 costimulation and in turn triggers potent tumor-specific T cell responses resistant to PD-1 and CTLA-4 blockade. Naive T cell activation requires both TCR and CD28 signals. The CARMIL2 cytosolic protein enables CD28-dependent activation of the NF-¦ÊB transcription factor via its ability to link CD28 to the CARD11 adaptor protein. Here, we developed mice expressing a mutation named Carmil2QE and mimicking a mutation found in human T cell malignancies. Naive T cells from Carmil2QE mice contained preformed CARMIL2QE-CARD11 complexes in numbers comparable to those assembling in wild-type T cells after CD28 engagement. Such ready-made CARMIL2QE-CARD11 complexes also formed in CD28-deficient mice where they unexpectedly induced most of the functions that normally result from CD28 engagement in a manner that remains antigen-dependent. In turn, tumor-specific T cells expressing Carmil2QE do not require CD28 engagement and thereby escape to both PD-1 and CTLA-4 inhibition. In conclusion, we uncovered the overarching role played by CARMIL2-CARD11 signals among those triggered by CD28 and exploited them to induce potent solid tumor¨Cspecific T cell responses in the absence of CD28 ligands and immune checkpoint inhibitors.