Immune checkpoint therapy has transformed cancer treatment, yet efficacy and safety challenges persist. Selectively inhibiting tumor-infiltrating regulatory T cells (Ti-Tregs) while enhancing CD8+ T cell function are complementary strategies in cancer immunotherapy. Here, we engineered a bispecific antibody, FRP303, targeting 4-1BB and CCR8, which are co-expressed on a highly immunosuppressive subset of Ti-Tregs. In vivo, FRP303 outperformed monoclonal antibodies in CT26 and MC38 colorectal tumors and poorly immunogenic B16F10 melanoma. Treatment with FRP303 reduced Ti-Treg frequency, increased CD8+ T cell infiltration, and elevated antitumor cytokines IFN-γ and TNF-α. Safety assessments showed FRP303 does not disrupt immune homeostasis in peripheral tissues or induce significant hepatotoxicity. Moreover, FRP303 demonstrated strong synergistic effects when combined with a PD-1 antibody. In summary, FRP303 mediated anti-tumor activity through a dual mechanism involving the selective depletion of Ti-Tregs and the enhancement of CD8+ T cell function, offering a promising strategy for cancer immunotherapy.
© 2025 The Authors.

Pathological α-synuclein (α-syn) can spread from the gut to the central nervous system (CNS), with CD4 + T cells playing a key role in this process. Lymphocyte activation gene 3 (LAG3) is involved in intestinal inflammation, regulates CD4 + T cell proliferation and function, and can specifically bind to pathological α-syn during cell-to-cell transmission. However, it remains unclear whether LAG3 is involved in the spread of pathological α-syn from the gut to the brain.
We utilized LAG3 knockout mice, combined with injection of α-syn preformed fibril (PFF) into the longitudinal and intermediate muscle layers of the pylorus and duodenum to model Parkinson's disease (PD). We used Immunohistochemistry staining, Western Blot, Flow cytometry to detect the changes of TH, α-syn, pro-inflammatory factors, barrier-related proteins and CD4 + T cells differentiation.
Our results show that LAG3 knockout partially alleviates psychological and behavioral deficits, dopamine system damage, and the gut-to-brain transmission of α-syn, which correlates with enhanced regulatory T cell (Treg) cell proliferation. Furthermore, LAG3 knockout improved intestinal dysfunction and increased the expression of tight junction proteins in both the gut and the blood-brain barrier (BBB). In CD4 + T cells isolated from the spleen, LAG3 knockout suppressed the aggregation of α-syn PFF, thereby inhibiting the toxic T-cell response induced by α-syn PFF. LAG3 deficiency also enhanced the IL-2/STAT5 signaling pathway, which regulates Treg proportions both in vivo and in vitro.
Our findings demonstrated that LAG3 intrinsically limits Treg cell proliferation and function in the environment with pathological α-syn and promotes the gut-to-brain transmission of α-syn.
© 2025. The Author(s).

Oropharyngeal candidiasis (OPC) is an opportunistic infection caused by Candida albicans. IL-17-mediated immunity driven by Th17 cells plays a crucial role in defense against this infection. However, the location and mechanism by which the Th17 immune response is induced during OPC remain unclear. Here, we show that C. albicans in the gut enhances protection against OPC. Intestinal C. albicans is taken up by the mucosal immune system and triggers a systemic C. albicans-responsive Th17 cell response. Upon oral infection with C. albicans, these Th17 cells migrate from the gut to the oral region and accumulate in the tongue tissue, resulting in antifungal immune responses. The pathobiont-reactive Th17 cells developed in the gut strongly provide IL-17A not only locally in the mouth but also systemically in the serum upon OPC. Our findings highlight that fungal pathogen-responsive Th17 cells in the gut-mouth axis enhance protection against OPC.
© 2025 The Author(s).

Interleukin-12 (IL-12) is a promising pro-inflammatory cytokine for cancer immunotherapy, but its toxicity and short half-life in serum limit its clinical application. Tumor-targeted delivery of IL-12 by fusion with either antibody or secretion by chimeric antigen receptor T (CAR-T) cells showed reduced systematic toxicity; however, the poor tumor microenvironment (TME) response or the lack of systematic IL-12 regulation still remains risk of low efficacy or high toxicity. Here, we developed TME-specific delivery of IL-12 by a tumor-targeted adeno-associated virus 9 (tAAV9). The tAAV9 was formed by an anti-folate receptor 1 (anti-FOLR1) antibody fragment conjugated with AAV9 via highly efficient Spy-ligation. With targeted infection of FOLR1+ cells in vivo, intravenous (i.v.) administration of tAAV9 specifically delivered IL-12 (tAAV9-IL-12) to TME and significantly suppressed tumor progression with favorable safety profile compared with rAAV9 (recombinant wild-type AAV9) delivery. Moreover, the IL-12 level in the serum was decreased significantly with the suppression of tAAV9-IL-12-infected tumor cell, so that generates promising negative feedback to ensure the safety profile.
© 2025 The Author(s).

Imbalanced effector and regulatory CD4+ T cell subsets drive many inflammatory diseases. These T cell subsets rely on distinct metabolic programs, modulation of which differentially affects T cell fate and function. Lipid metabolism is fundamental yet remains poorly understood across CD4+ T cell subsets. Therefore, we performed targeted in vivo CRISPR/Cas9 screens to identify lipid metabolism genes and pathways essential for T cell functions. These screens established mitochondrial fatty acid synthesis genes Mecr, Mcat, and Oxsm as key metabolic regulators. Of these, the inborn error of metabolism gene Mecr was most dynamically regulated. Mecrfl/fl; Cd4cre mice had normal naïve CD4+ and CD8+ T cell numbers, demonstrating that MECR is not essential in homeostatic conditions. However, effector and memory T cells were reduced in Mecr knockout and MECR-deficient CD4+ T cells and proliferated, differentiated, and survived less well than control T cells. Interestingly, T cells ultimately showed signs of mitochondrial stress and dysfunction in the absence of MECR. Mecr-deficient T cells also had decreased mitochondrial respiration, reduced tricarboxylic acid intermediates, and accumulated intracellular iron, which appeared to contribute to increased cell death and sensitivity to ferroptosis. Importantly, MECR-deficient T cells exhibited fitness disadvantages and were less effective at driving disease in an in vivo model of inflammatory bowel disease. Thus, MECR-mediated metabolism broadly supports CD4+ T cell proliferation and survival in vivo. These findings may also provide insight to the immunological state of MECR- and other mitochondrial fatty acid synthesis-deficient patients.
© The Author(s) 2025. Published by Oxford University Press on behalf of The American Association of Immunologists.