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MICA and MICB proteins can be expressed on tumors and act as “kill me” signals to the immune system. But tumors often disguise themselves by shedding these proteins, which prevents specialized natural killer (NK) cells from recognizing and destroying the cancer. Ferrari de Andrade et al. engineered antibodies directed against the site responsible for the proteolytic shedding of MICA and MICB (see the Perspective by Cerwenka and Lanier). The approach effectively locked MICA and MICB onto tumors so that NK cells could spot them for elimination. The antibodies exhibited preclinical efficacy in multiple tumor models, including humanized melanoma. Furthermore, the strategy reduced lung cancer metastasis after NK cell–mediated tumor lysis. Science , this issue p. 1537 ; see also p. 1460 Natural killer cell–mediated antitumor response is restored when tumors are prevented from sloughing off surface markers. MICA and MICB are expressed by many human cancers as a result of cellular stress, and can tag cells for elimination by cytotoxic lymphocytes through natural killer group 2D (NKG2D) receptor activation. However, tumors evade this immune recognition pathway through proteolytic shedding of MICA and MICB proteins. We rationally designed antibodies targeting the MICA α3 domain, the site of proteolytic shedding, and found that these antibodies prevented loss of cell surface MICA and MICB by human cancer cells. These antibodies inhibited tumor growth in multiple fully immunocompetent mouse models and reduced human melanoma metastases in a humanized mouse model. Antitumor immunity was mediated mainly by natural killer (NK) cells through activation of NKG2D and CD16 Fc receptors. This approach prevents the loss of important immunostimulatory ligands by human cancers and reactivates antitumor immunity.

Lung emphysema and chronic bronchitis are the two most common causes of chronic obstructive pulmonary disease. Excess macrophage elastase MMP-12, which is predominantly secreted from alveolar macrophages, is known to mediate the development of lung injury and emphysema. Here, we discovered the endolysosomal cation channel mucolipin 3 (TRPML3) as a regulator of MMP-12 reuptake from broncho-alveolar fluid, driving in two independently generated Trpml3 −/− mouse models enlarged lung injury, which is further exacerbated after elastase or tobacco smoke treatment. Mechanistically, using a Trpml3 IRES-Cre/eR26- τ GFP reporter mouse model, transcriptomics, and endolysosomal patch-clamp experiments, we show that in the lung TRPML3 is almost exclusively expressed in alveolar macrophages, where its loss leads to defects in early endosomal trafficking and endocytosis of MMP-12. Our findings suggest that TRPML3 represents a key regulator of MMP-12 clearance by alveolar macrophages and may serve as therapeutic target for emphysema and chronic obstructive pulmonary disease. Excess macrophage elastase MMP-12 is a major driver of chronic obstructive pulmonary disease. Here the authors show that the endolysosomal ion channel TRPML3 is a regulator of the cellular reuptake of MMP-12, thus neutralizing harmful MMP-12 in the lung.

T-cell bispecific antibodies (TCBs) crosslink tumor and T-cells to induce tumor cell killing. While TCBs are very potent, on-target off-tumor toxicity remains a challenge when selecting targets. Here, we describe a protease-activated anti-folate receptor 1 TCB (Prot-FOLR1-TCB) equipped with an anti-idiotypic anti-CD3 mask connected to the anti-CD3 Fab through a tumor protease-cleavable linker. The potency of this Prot- FOLR1-TCB is recovered following protease-cleavage of the linker releasing the anti-idiotypic anti-CD3 scFv. In vivo, the Prot-FOLR1-TCB mediates antitumor efficacy comparable to the parental FOLR1-TCB whereas a noncleavable control Prot-FOLR1-TCB is inactive. In contrast, killing of bronchial epithelial and renal cortical cells with low FOLR1 expression is prevented compared to the parental FOLR1-TCB. The findings are confirmed for mesothelin as alternative tumor antigen. Thus, masking the anti-CD3 Fab fragment with an anti-idiotypic mask and cleavage of the mask by tumor-specific proteases can be applied to enhance specificity and safety of TCBs. The clinical application of T cell bispecific antibodies (TCBs) is often limited by the lack of tumour-specific antigens. In this study, the authors present a strategy to increase TCB tumour-selectivity by adding an anti-CD3 moiety that can be specifically activated by tumor specific proteases in the tumor microenvironment.

Memory T cells play an important role in mediating long-lasting adaptive immune responses to viral infections, such as SARS-CoV-2. In the context of the latter, much of our current knowledge stems from studies in vaccinated individuals or repeatedly infected individuals. However, limited knowledge is available on these responses in fully naive individuals in German communities. We performed immunophenotyping of a previously naive SARS-CoV-2 cohort in convalescent individuals after asymptomatic to moderate COVID-19. The samples were collected median 250 days post infection during the first wave of the COVID pandemic in Germany (March – May 2020). In this cohort of 174 individuals, we phenotyped different leukocyte cell populations in peripheral blood (B, T and Natural Killer cells). We then assessed the serostatus against the SARS-CoV-2 antigens Nucleocapsid (N) and Spike subunit (S1) with its receptor binding domain (RBD), as these are important correlates of protection, by testing for presence of immunoglobulin G (IgG) antibodies. We also measured IgG antibody responses against the N antigen of the common cold coronaviruses HCoV-OC43, HCoV-HKU1, HCoV-NL63 and HCoV-229E, to determine possible cross-reactivity. In a subset of the cohort (n = 76), we performed intracellular staining assays (ICS) after stimulation with SARS-CoV-2 and HCoV antigens. Key findings are significant differences in frequency of CD4+ memory T cell populations, notably CD4+ T EM and CD4+ T EMRA cells, between the group of SARS-CoV-2 positive individuals and the control group. These differences correlated with cytokine production (TNFα, IFNγ) after stimulation with SARS-CoV-2 peptides, indicating a specific T cell immune response. In conclusion, a clear memory T cell and humoral response can be detected up to 250 days post mild to moderate COVID-19 disease. Our results underline findings reported by others indicating a lasting cellular immune response even in a population which previously had not been exposed to SARS-CoV-2.

Retinoic acid-inducible gene-I (RIG-I) is a cytoplasmic immune receptor sensing viral RNA. It triggers the release of type I interferons (IFN) and proinflammatory cytokines inducing an adaptive cellular immune response. We investigated the therapeutic potential of systemic RIG-I activation by short 5′-triphosphate-modified RNA (ppp-RNA) for the treatment of acute myeloid leukemia (AML) in the syngeneic murine C1498 AML tumor model. ppp-RNA treatment significantly reduced tumor burden, delayed disease onset and led to complete remission including immunological memory formation in a substantial proportion of animals. Therapy-induced tumor rejection was dependent on CD4+ and CD8+ T cells, but not on NK or B cells, and relied on intact IFN and mitochondrial antiviral signaling protein (MAVS) signaling in the host. Interestingly, ppp-RNA treatment induced programmed death ligand 1 (PD-L1) expression on AML cells and established therapeutic sensitivity to anti-PD-1 checkpoint blockade in vivo. In immune-reconstituted humanized mice, ppp-RNA treatment reduced the number of patient-derived xenografted (PDX) AML cells in blood and bone marrow while concomitantly enhancing CD3+ T cell counts in the respective tissues. Due to its ability to establish a state of full remission and immunological memory, our findings show that ppp-RNA treatment is a promising strategy for the immunotherapy of AML.

T cell exhaustion is a hallmark of cancer and persistent infections, marked by inhibitory receptor upregulation, diminished cytokine secretion, and impaired cytolytic activity. Terminally exhausted T cells are steadily replenished by a precursor population (Tpex), but the metabolic principles governing Tpex maintenance and the regulatory circuits that control their exhaustion remain incompletely understood. Using a combination of gene-deficient mice, single-cell transcriptomics, and metabolomic analyses, we show that mitochondrial insufficiency is a cell-intrinsic trigger that initiates the functional exhaustion of T cells. At the molecular level, we find that mitochondrial dysfunction causes redox stress, which inhibits the proteasomal degradation of hypoxia-inducible factor 1α (HIF-1α) and promotes the transcriptional and metabolic reprogramming of Tpex cells into terminally exhausted T cells. Our findings also bear clinical significance, as metabolic engineering of chimeric antigen receptor (CAR) T cells is a promising strategy to enhance the stemness and functionality of Tpex cells for cancer immunotherapy. Exhaustion is the functional deterioration of T cells following chronic stimulation. Here, Wu et al. show that mitochondrial dysfunction drives T cell exhaustion by inhibiting HIF-1α degradation and transcriptional metabolic reprogramming.

BackgroundPancreatic ductal adenocarcinoma (PDAC) remains largely refractory to chimeric antigen receptor (CAR)-T cell therapy. Insufficient T cell infiltration, a highly immunosuppressive microenvironment, and antigen loss pose major challenges for CAR-T cell therapy.MethodsWe investigated therapeutic synergies of synthetic 5′-triphosphate RNA (3p-RNA), an agonist of the cytoplasmic double-stranded RNA sensor Retinoic Acid Inducible Gene I (RIG-I), and CAR-T cell therapy using syngeneic and human xenograft PDAC models. Tumor growth, chemokine secretion, immune-cell composition, CAR-T persistence, and endogenous T cell responses were assessed by flow cytometry, multiplex cytokine arrays, Enzyme-linked Immunospot (ELISpot), and vaccination-challenge.Results3p-RNA provoked rapid type I interferon accompanied with chemokine ligand CCL5 and CXCL9/10/11 secretion, creating chemokine gradients that recruited chemokine receptor CCR5+/CXCR3+ CAR-T cells into tumors. RIG-I activation enhanced CAR-T cell proliferation, activity, and CAR-T persistence. Combination therapy eradicated established tumors in 60%–70% of mice, whereas either monotherapy was largely ineffective. Cured animals rejected CAR antigen-negative tumor cell rechallenge, demonstrating antigen-spreading and endogenous T cell responses.ConclusionsIntratumoral RIG-I priming reprograms the PDAC microenvironment, transforming a non-responsive cancer into a CAR-T-permissive one, supporting durable, poly-antigenic immunity. These findings position 3p-RNA as a rapid, clinically tractable co-therapy to extend CAR-T efficacy to solid tumors.

Since its discovery, interleukin-1 has been extensively studied in a wide range of medical fields. Besides carrying out vital physiological functions, it has been implicated with a pivotal role in the progression and spreading of different cancer entities. During the last years, several clinical trials have been conducted, shedding light on the role of IL-1 blocking agents for the treatment of cancer. Additionally, recent developments in the field of immuno-oncology have implicated IL-1-induced signaling cascades as a major driver of severe chimeric antigen receptor T cell-associated toxicities such as cytokine release syndrome and immune effector cell-associated neurotoxicity. In this review, we summarize current clinical trials investigating the role of IL-1 blockade in cancer treatment and elaborate the proposed mechanism of these innovative treatment approaches. Additionally, we highlight cutting-edge developments utilizing IL-1 blocking agents to enhance the safety and efficacy of adoptive T cell therapy.

Immunotherapy has become an established pillar of cancer treatment improving the prognosis of many patients with a broad variety of hematological and solid malignancies. The two main drivers behind this success are checkpoint inhibitors (CPIs) and chimeric antigen receptor (CAR) T cells. This review summarizes seminal findings from clinical and translational studies recently presented or published at important meetings or in top-tier journals, respectively. For checkpoint blockade, current studies focus on combinational approaches, perioperative use, new tumor entities, response prediction, toxicity management and use in special patient populations. Regarding cellular immunotherapy, recent studies confirmed safety and efficacy of CAR T cells in larger cohorts of patients with acute lymphoblastic leukemia or diffuse large B cell lymphoma. Different strategies to translate the striking success of CAR T cells in B cell malignancies to other hematological and solid cancer types are currently under clinical investigation. Regarding the regional distribution of registered clinical immunotherapy trials a shift from PD-1 / PD-L1 trials (mainly performed in the US and Europe) to CAR T cell trials (majority of trials performed in the US and China) can be noted.