Humoral Autoimmunity Research Articles

Aberrant METTL1-mediated tRNA m7G modification alters B-cell responses in systemic autoimmunity in humans and mice

Upon activation, naive B cells exit their quiescent state and enter germinal center (GC) responses, a transition accompanied by increased protein synthesis. How protein translation efficiency is adequately adjusted to meet the increased demand requires further investigation. Here, we identify the methyltransferase METTL1 as a translational checkpoint during GC responses. Conditional knockout of Mettl1 in mouse B cells blocks GC entry and impairs GC formation, whereas conditional knock-in of Mettl1 promotes GC responses. Mechanistically, METTL1 catalyzes m7G modification in a specific subset of tRNAs to preferentially translate BCR signaling-related proteins, ensuring mitochondrial electron transporter chain activity and sufficient bioenergetics in B cells. Pathologically, METTL1-mediated tRNA m7G modification controls B-cell autoreactivity in SLE patients or lupus-prone mice, and deletion of Mettl1 alleviates dysregulated B-cell responses during autoimmune induction. Thus, these results support the function of METTL1 in orchestrating an effective B-cell response and reveal that aberrant METTL1-mediated tRNA m7G modification promotes autoreactive B cells in systemic autoimmunity.

The identification of a SARs-CoV2 S2 protein-derived peptide with super-antigen-like stimulatory properties on T-cells.

Severe COVID-19 can trigger a cytokine storm, leading to acute respiratory distress syndrome (ARDS) with similarities to superantigen-induced toxic shock syndrome. An outstanding question is whether SARS-CoV-2 protein sequences can directly induce inflammatory responses. In this study, we identify a region in the SARS-CoV-2 S2 spike protein with sequence homology to bacterial super-antigens (termed P3). Computational modeling predicts P3 binding to sites on MHC class I/II and the TCR that partially overlap with sites for the binding of staphylococcal enterotoxins B and H. Like SEB and SEH peptides, P3 stimulated 25-40% of human CD4+ and CD8+ T cells, increasing IFN-γ and granzyme B production. viSNE and SPADE profiling identified overlapping and distinct IFN-γ and GZMB subsets. The super-antigenic properties of P3 were further evident by its selective expansion of T cells expressing specific TCR Vα and Vβ chain repertoires. In vivo experiments in mice revealed that the administration of P3 led to a significant upregulation of proinflammatory cytokines IL-1β, IL-6, and TNF-α. While the clinical significance of P3 in COVID-19 remains unclear, its homology to other mammalian proteins suggests a potential role for this peptide family in human inflammation and autoimmunity.

Human Papillomavirus Infection and Autoimmune Diseases: A Two-Sample Bidirectional Mendelian Randomization Study.

Although earlier observational studies have revealed a connection between human papillomavirus (HPV) infection and several autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), the exact causative mechanism underlying this association is still unknown. This two-sample bidirectional MR study was conducted based on publicly released data from genome-wide association studies (GWAS). Our results were mainly derived from the inverse variance weighted (IVW) model, with the remaining three models also being calculated. The MR Steiger test was used to examine the correctness of our causal direction. Sensitivity analysis was performed using Mendelian randomized pleiotropy residual sum and outlier (MR-PRESSO), MR-Egger regression. The IVW results showed that there was a positive causal association between HPV16 E7 protein and SLE (odds ratio (OR) = 1.075, 95% confidence interval (CI), 1.003-1.151, FDR-p = 0.04), however, there was a negative causal association between HPV18 E7 protein and SLE (OR = 0.884, 95% CI, 0.804-0.972, FDR-p = 0.02). No causal associations of HPV16 E7 protein and HPV18 E7 protein with RA, IBD was observed including its subtypes Ulcerative colitis (UC) and Crohn's disease (CD). Sensitivity analysis showed that there was no significant heterogeneity (p > 0.05) or genetic pleiotropy (p > 0.05). Our two-sample bidirectional Mendelian randomization study identifies a causal association between HPV infection and SLE, but no causal association between HPV infection and RA and IBD.

Psycho-Neuro-EndocrinE-Immunology Therapy of Cancer, Autoimmunity, Geriatric Disorders, Covid-19, and Hypertension.

Despite the great number of experimental investigations in the area of psycho-neuro-endocrine-immunology showing that endocrine, nervous, and immune systems cannot be in vivo physiologically separated, the diagnosis and therapies of the pathologies of these three functional biological systems continue to be separately performed from a clinical practice point of view. The separation between experimental and clinical medicine became dramatic after the discovery of more than 10 human molecules provided by anti-inflammatory and antitumor activity, completely devoid of any toxicity, which may be subdivided into three fundamental classes, consisting of the pineal indole, beta-carboline, and methoxy-kynuramine hormones. Moreover, human systemic diseases, including cancer, autoimmunity, and cardiovascular pathologies, despite their different pathogenesis and symptomatology, are commonly characterized by a progressive decline in the endogenous production of pineal hormones, endocannabinoids, and Ang 1-7, with a consequent inflammatory status and diminished natural resistance against cancer. Then the evaluation of the functional status of the pineal gland, the endocannabinoid system, and ACE2-Ang 1-7 axis should have to be included within the laboratory analyses for the systemic diseases. Finally, the correction of cancer- and autoimmunity-related neuroimmune and neuroendocrine alterations could influence the clinical course of systemic diseases. In fact, preliminary clinical results would demonstrate that the neuroimmune regimen with pineal hormones, cannabinoids, and Ang 1-7 may allow clinical benefits also in patients affected by systemic pathologies, including cancer, autoimmunity, and cardiovascular diseases, who did not respond to the standard therapies.

B-Cell Maturation Antigen (BCMA) as a Biomarker and Potential Treatment Target in Systemic Lupus Erythematosus.

The BAFF-APRIL system is crucial for the pathogenesis of systemic lupus erythematosus (SLE) by promoting B cell survival, differentiation and the maintenance of humoral autoimmunity. Here, we investigated the relationship of BCMA expression on B cell subsets with its ligands BAFF and APRIL, together with soluble BCMA, and with clinical and serologic variables in a cohort of 100 SLE patients (86 under conventional and 14 under belimumab therapy) and 30 healthy controls (HCs) using multicolor flow cytometry and ELISA. We found that BCMA expression in SLE patients was significantly increased on all B cell subsets compared to HCs, with all examined components of the BAFF-APRIL system being upregulated. BCMA expression was significantly increased on switched and unswitched memory B cells compared to naïve B cells, both in HCs and SLE. BCMA expression on B cells correlated with plasmablast frequencies, serum anti-dsDNA antibodies and complement consumption, while soluble BCMA correlated with plasmablast frequency, highlighting its potential as a clinical biomarker. Belimumab treatment significantly reduced BCMA expression on most B cell subsets and soluble TACI and contributed to the inhibition of almost the entire BAFF-APRIL system and restoration of B cell homeostasis. These results provide insights into the complex dysregulation of the BAFF-APRIL system in SLE and highlight the therapeutic potential of targeting its components, particularly BCMA, in addition to its use as a biomarker for disease activity.

Antibodies in neurological diseases: Established, emerging, explorative.

Within a few years, autoantibodies targeting the nervous system resulted in a novel disease classification. For several of them, which we termed 'established', direct pathogenicity has been proven and now guides diagnostic pathways and early immunotherapy. For a rapidly growing number of further anti-neuronal autoantibodies, the role in disease is less clear. Increasing evidence suggests that they could contribute to disease, by playing a modulating role on brain function. We therefore suggest a three-level classification of neurological autoantibodies according to the degree of experimentally proven pathogenicity and strength of clinical association: established, emerging, explorative. This may facilitate focusing on clinical constellations in which autoantibody-mediated mechanisms have not been assumed previously, including autoimmune psychosis and dementia, cognitive impairment in cancer, and neurodegenerative diseases. Based on recent data reviewed here, humoral autoimmunity may represent an additional "super-system" for brain health. The "brain antibody-ome", that is, the composition of thousands of anti-neuronal autoantibodies, may shape neuronal function not only in disease, but even in healthy aging. Towards this novel concept, extensive research will have to elucidate pathogenicity from the atomic to the clinical level, autoantibody by autoantibody. Such profiling can uncover novel biomarkers, enhance our understanding of underlying mechanisms, and identify selective therapies.

Cutibacterium acnes as an overseen autoimmunity trigger: Unearthing heat-shock driven molecular mimicry

Cutibacterium acnes, common resident of the human skin, can establish both commensal and pathogenic relations with the human host; however, long-term consequences of C. acnes-induced inflammation remained un(der)explored. To infer the capacity of triggering autoimmunity in humans via molecular mimicry, a comprehensive immunoinformatics analysis of the experimentally characterized C. acnes proteome was performed. The protocol included homology screening between the C. acnes and the human proteome, and validation of shared specificity regions against the collection of experimentally characterized T-cell epitopes, related to autoimmunity. To obtain highly reliable predictions, the results were subjected to additional cross-validation by a dedicated MHC-restriction analysis, including a docking study of C. acnes mimotopes and human counterparts with the highest degree of sequence similarity to MHCII molecules representing the highest risk for detected autoimmune pathologies. Due to mimicking of highly immunogenic, but also evolutionary conserved autoantigens from the Heat Shock protein family, association between C. acnes and the pathogenesis of highly incident autoimmune diseases: Type 1 Diabetes, Rheumatoid Arthritis, and Juvenile Idiopathic Arthritis, was found. To the best of our knowledge, this study is the first one to provide preliminary information and a mechanistic link on the putative involvement of C. acnes in the pathogenesis of autoimmunity in humans.

Peripheral-derived regulatory T cells contribute to tumor-mediated immune suppression in a nonredundant manner

Identifying tumor-mediated mechanisms that impair immunity is instrumental for the design of new cancer therapies. Regulatory T cells (Tregs) are a key component of cancer-derived immune suppression; however, these lymphocytes are necessary to prevent systemic autoimmunity in mice and humans, and thus, direct targeting of Tregs is not a clinical option for cancer patients. We have previously demonstrated that excising transcription factor Kruppel-like factor 2 (Klf2) within the T cell lineage blocks the generation of peripheral-derived Tregs (pTregs) without impairing production of thymic-derived Tregs. Using this mouse model, we have now demonstrated that eliminating pTregs is sufficient to delay/prevent tumor malignancy without causing autoimmunity. Cancer-bearing mice that expressed KLF2 converted tumor-specific CD4+ T cells into pTregs, which accumulated in secondary lymphoid organs and impaired further T cell effector activity. In contrast, pTreg-deficient mice retained cancer-specific immunity, including improved T cell infiltration into "cold" tumors, reduced T cell exhaustion in tumor beds, restricted generation of tumor-associated myeloid-derived suppressor cells, and the continued production of circulating effector T cells that arose in a cancer-dependent manner. Results indicate that tumor-specific pTregs are critical for early stages of cancer progression and blocking the generation of these inhibitory lymphocytes safely delays/prevents malignancy in preclinical models of melanoma and prostate cancer.

An autoimmune transcriptional circuit drives FOXP3+ regulatory T cell dysfunction.

Autoimmune diseases, among the most common disorders of young adults, are mediated by genetic and environmental factors. Although CD4+FOXP3+ regulatory T cells (Tregs) play a central role in preventing autoimmunity, the molecular mechanism underlying their dysfunction is unknown. Here, we performed comprehensive transcriptomic and epigenomic profiling of Tregs in the autoimmune disease multiple sclerosis (MS) to identify critical transcriptional programs regulating human autoimmunity. We found that up-regulation of a primate-specific short isoform of PR domain zinc finger protein 1 (PRDM1-S) induces expression of serum and glucocorticoid-regulated kinase 1 (SGK1) independent from the evolutionarily conserved long PRDM1, which led to destabilization of forkhead box P3 (FOXP3) and Treg dysfunction. This aberrant PRDM1-S/SGK1 axis is shared among other autoimmune diseases. Furthermore, the chromatin landscape profiling in Tregs from individuals with MS revealed enriched activating protein-1 (AP-1)/interferon regulatory factor (IRF) transcription factor binding as candidate upstream regulators of PRDM1-S expression and Treg dysfunction. Our study uncovers a mechanistic model where the evolutionary emergence of PRDM1-S and epigenetic priming of AP-1/IRF may be key drivers of dysfunctional Tregs in autoimmune diseases.

CGAS-activated endothelial cell-T cell cross-talk initiates tertiary lymphoid structure formation.

Aberrant activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) pathway causes autoimmunity in humans and mice; however, the exact mechanism by which the cGAS-STING pathway initiates adaptive immunity and tissue pathology is still not fully understood. Here, we used a cGAS knockin (KI) mouse model that develops systemic autoimmunity. In the lungs of cGAS-KI mice, blood vessels were enclosed by organized lymphoid tissues that resemble tertiary lymphoid structures (TLSs). Cell-intrinsic cGAS induction promoted up-regulation of CCR5 in CD8+ T cells and led to CCL5 production in vascular endothelial cells. Peripheral CD8+ T cells were recruited to the lungs and produced CXCL13 and interferon-γ. The latter triggered endothelial cell death, potentiated CCL5 production, and was essential for TLS establishment. Blocking CCL5 or CCR5, or depleting CD8+ T cells, impaired TLS formation. cGAS-mediated TLS formation also enhanced humoral and antitumor responses. These data demonstrate that cGAS signaling drives a specialized lymphoid structure that underlies autoimmune tissue pathology.

Mild Primary or Breakthrough SARS-CoV-2 Infection Promotes Autoantibody Production in Individuals with and without Neuro-PASC.

Patients with long COVID can develop humoral autoimmunity after severe acute SARS-CoV-2 infection. However, whether similar increases in autoantibody responses occur after mild infection and whether vaccination prior to SARS-CoV-2 breakthrough infection can limit autoantibody responses is unknown. In this study, we demonstrate that mild SARS-CoV-2 infection increases autoantibodies associated with rheumatic autoimmune diseases and diabetes in most individuals, regardless of vaccination status prior to infection. However, patients with long COVID and persistent neurologic and fatigue symptoms (neuro-PASC) have substantially higher autoantibody responses than convalescent control subjects at an average of 8 mo postinfection. Furthermore, high titers of systemic lupus erythematosus- and CNS-associated autoantibodies in patients with neuro-PASC are associated with impaired cognitive performance and greater symptom severity. In summary, we found that mild SARS-CoV-2 primary and breakthrough infections can induce persistent humoral autoimmunity in both patients with neuro-PASC and healthy COVID convalescents, suggesting that a reappraisal of mitigation strategies against SARS-CoV-2 is warranted to prevent transmission and potential development of autoimmunity.

UNCovering new causes of monogenic systemic lupus erythematosus.

UNC93B1 is essential for the stability and endosomal trafficking of nucleic-acid sensing Toll-like receptors (TLRs) including TLR7 and TLR8. Increased TLR7 responses are associated with lupus autoimmunity in both mice and humans. In a recent article, Al-Azab etal. demonstrate the role of a variant of UNC93B1 (p.V117L) in the induction of pediatric systemic lupus erythematosus in patients and in mice through TLR7/8 hyperresponsiveness. They also highlight a potential role for the pharmacological inhibition of interleukin-1 receptor-associated kinase (IRAK) 1 and/or 4 in ameliorating disease.

Large-scale mutational analysis identifies UNC93B1 variants that drive TLR-mediated autoimmunity in mice and humans.

Nucleic acid-sensing Toll-like receptors (TLR) 3, 7/8, and 9 are key innate immune sensors whose activities must be tightly regulated to prevent systemic autoimmune or autoinflammatory disease or virus-associated immunopathology. Here, we report a systematic scanning-alanine mutagenesis screen of all cytosolic and luminal residues of the TLR chaperone protein UNC93B1, which identified both negative and positive regulatory regions affecting TLR3, TLR7, and TLR9 responses. We subsequently identified two families harboring heterozygous coding mutations in UNC93B1, UNC93B1+/T93I and UNC93B1+/R336C, both in key negative regulatory regions identified in our screen. These patients presented with cutaneous tumid lupus and juvenile idiopathic arthritis plus neuroinflammatory disease, respectively. Disruption of UNC93B1-mediated regulation by these mutations led to enhanced TLR7/8 responses, and both variants resulted in systemic autoimmune or inflammatory disease when introduced into mice via genome editing. Altogether, our results implicate the UNC93B1-TLR7/8 axis in human monogenic autoimmune diseases and provide a functional resource to assess the impact of yet-to-be-reported UNC93B1 mutations.

Caveolin-1 restrains pathogenic T follicular helper cell response in primary Sjögren’s syndrome

Abstract T follicular helper (Tfh) cells play a central role in humoral autoimmunity, including primary Sjögren’s syndrome (pSS). However, targeting Tfh cells is challenging in clinical management. Previous studies suggested that inducible T­cell co­stimulator (ICOS) directed Tfh cell motility in engaging bystander B cells, which promoted plasma cell differentiation and antibodies production. Here, we identified a novel function of caveolin-1 (Cav-1) in restraining ICOS expression in Tfh cells and pSS pathogenesis. Cav-1 deficiency significantly promoted human and murine Tfh cell responses, while Cav-1-/- mice exhibited exacerbated disease pathology of experimental SS (ESS). Peroxisome proliferator-activated receptor alpha (PPARa), a downstream transcription factor of Cav-1, rapidly repressed Icos transcription upon Tfh polarization, interestingly, independence of lipid metabolism. Phenotypic analyses suggested that Cav-1 and PPARa expressions were decreased in CD4+ T cells from pSS patients and ESS mice. Notably, pharmaceutical activation of PPARa with fenofibrate could suppress human and murine Tfh cells both in vitro and in vivo, while oral administration of fenofibrate effectively ameliorated ESS pathology in mice with acute or chronic inflammation. These results revealed an unrecognized role of Cav-1/PPARa axis in Tfh cell tolerance and pSS pathogenesis, suggesting PPARa as a promising target in the treatment of humoral autoimmunity.

The ouroboros of autoimmunity.

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Identification and characterization of PD-1 agonists for the treatment of autoimmune and inflammatory diseases

Abstract The development of autoimmune diseases is the result of a dysregulated immune response against self-antigens, resulting in cell dysregulation and tissue damage. Upon chronic exposure to antigens, inhibitory receptors (IR) are upregulated as a feedback mechanism to limit T-cell effector activity. IR deficiency is associated with autoimmunity in mice and humans. Similarly, blockade of IR is efficacious for the treatment of cancer but is often associated with new onset of immune-related adverse events. Therefore, if loss or blocking of IR pathways can result in autoimmunity, agonism of these pathways should restore normal immune homeostasis. However, the generation of agonistic antibodies present some challenges. For instance, to elicit strong receptor agonism, super-clustering mediated by the binding of the constant region (Fc) of an antibody to FcgRs, must occur. However, while FcgRs are widely expressed on antigen-presenting cells (APCs), they are not the same and are classified, based on their function, as activating or inhibitory. Of note, FcgRIIb is the only inhibitory Fc receptor, and APCs derived from mice deficient in this receptor exhibited exaggerated cytokine release. Most PD-1 agonist antibodies in clinical development contain a wild-type Fc and can trigger unwanted production of pro-inflammatory cytokines by engaging activating FcgRs. To mitigate such liability, we designed novel PD-1 agonistic antibodies that selectively bind FcgRIIb and prevent APC activation.

Isotype-Specific Autoantibody Signatures in Cancer and Sepsis Samples through Multiplex Profiling

Abstract Many diseases can be characterized by specific autoantibodies. The Luminex™ multi-analyte profiling platform enables simultaneous detection a panel of autoantibodies in a single assay with minimal sample volume. MILLIPLEX™ multiplex assays include the 15-plex Human Cancer Autoantibody Panel, 23-plex Human Cytokine Autoantibody Panel, and 20-plex Human Autoimmune Autoantibody Panel, allowing qualitative profiling of autoantibodies in serum and plasma samples. In this study, we focused on detecting cancer-associated autoantibodies and anti-cytokine autoantibodies in breast cancer, colorectal cancer, sepsis, and healthy control samples (n ≥ 20 in each group). We used the Luminex™ 200™ system and the xMAP™ INTELLIFLEX DRSE instrument for analysis. Preliminary data revealed anti-cytokine IgG autoantibodies against multiple cytokines (e.g., IL-2, IL-4, IFNγ) in cancer, sepsis, and healthy individuals. Additionally, certain cytokine autoantibodies (e.g., IL-1α, IL-12p40, IL-6) were detected in the tested disease samples but not in healthy controls. Isotype profiling demonstrated increased detection of cancer-associated autoantibodies by combining IgG and IgM signatures in cancer samples (e.g., p53, CCNB1/Cyclin B1, SOX2, CTAG1B/NY-ESO-1, Her2/ErbB2). We believe this robust MILLIPLEX™ autoantibody detection and comprehensive isotype profiling can guide further research on autoantibodies as translational biomarkers in a clinical setting.

The role of autoimmune thyroid disorders in patients with alopecia areata

Objective: The aim of this study was to investigate the association of thyroid autoimmunity with alopecia areata (AA) by examining thyroid stimulating hormone (TSH) and thyroid autoantibody levels. In addition, to compare the epidemiologic data obtained with the data of our country. Methods: Our study was organized as a cross-sectional, retrospective study. The study was performed on patients between the ages of 2-65 years who were admitted to our outpatient clinic between 01.01.2008 and 31.12.2011, who were clinically or histopathological diagnosed with AA, examined for etiology and thyroid autoantibodies were requested. Patients under two years of age and over 65 years of age, patients with no thyroid autoantibodies and pregnant patients were excluded. Results were expressed as mean±standard deviation and median values. Mann-Whitney U test was used to compare TSH, anti-TG antibody (Anti-TG) and anti-TPO (Anti-TPO) antibody values in the variables of nail involvement, psychiatry, comorbidity and family history. Spearman correlation analysis was used to examine the relationships between age and disease duration and TSH, Anti-TPO and Anti-TG variables. Results: In our study, 65 (42.8%) of 152 patients were female and 87 (57.2%) were male. The ages of the patients ranged between 2-65 years and the mean age was 26.5±14.6 years. The mean age of females was 27.5±14.4 and 25.7±14.9 in males. Elevated thyroid autoantibodies were found in a total of 29 patients, 21 of whom were female and 8 of whom were male. Of these 29 patients, 10 had hypothyroidism, 2 had chronic thyroiditis and 3 had toxic multinodular goiter. 14 patients did not return after the examination at the internal medicine outpatient clinic, so the diagnosis of thyroid disease could not be reached. The mean TSH, Anti-TG and Anti-TPO values were 2.27±1.57, 29.2±99 and 71.5±2.2, respectively. When these values were analyzed separately as men and women, they were found to be 2.6±2.02, 41.8±1.23 and 134±2.8 in women and 1.99±1.03, 19.8±75.6 and 24.5±1.32 in men. There was a significant difference between men and women in terms of Anti-TG and Anti-TPO values (p=0.011 and p=0.001, respectively). A significant correlation was found between disease duration and Anti-TPO positivity (p=0.045); however, a similar relationship was not found between disease duration and Anti-TG positivity (p=0.34). Conclusions: As a result of this study, although there was a significant correlation between anti-TPO and duration of AA, the association between thyroid autoimmunity and AA was not found to be statistically significant. This may be due to the fact that humoral autoimmunity plays a role in thyroid autoimmunity and primarily cellular autoimmunity plays a role in AA. In addition, the epidemiologic data of our study were similar to the data of studies conducted in our country.

Abstract LB361: The exonuclease TREX1 constitutes an innate immune checkpoint limiting cGAS/STING-mediated anti-tumor immunity

Abstract The DNA exonuclease TREX1 (Three-prime repair exonuclease 1) is critical for preventing autoimmunity in mice and humans by degrading endogenous cytosolic DNA, which otherwise triggers activation of the innate cGAS/STING pathway leading to the production of type I IFNs. Since tumor cells are prone to aberrant cytosolic DNA accumulation, we hypothesized that they are critically dependent on TREX1 activity to limit their immunogenicity. Here we show, that in tumor cells TREX1 indeed restricts the spontaneous activation of the cGAS/STING pathway and the subsequent induction of a type I IFN response. As a result, TREX1 deficiency compromised in vivo tumor growth in mice. This delay depended on a functional immune system, systemic type I IFN signaling, and tumor-intrinsic cGAS expression. Mechanistically, we show that tumor TREX1 loss drove activation of CD8 T cells and NK cells, prevented CD8 T cell exhaustion and remodeled an immunosuppressive myeloid compartment. Consequently, TREX1 deficiency synergized with T cell directed immune checkpoint blockade. Collectively, we conclude that TREX1 is essential to limit tumor immunogenicity, and that targeting this innate immune checkpoint remodels the tumor microenvironment and enhances anti-tumor immunity by itself and in combination with T cell-targeted therapies. Citation Format: Junghyun Lim, Ryan Rodriguez, Katherine Williams, John Silva, Alan Gutierrez, Paul Tyler, Faezzah Baharom, Tao Sun, Eva Lin, Scott Martin, Brandon Kayser, Robert J. Johnston, Ira Mellman, Lélia Delamarre, Nathaniel West, Sören Müller, Yan Qu, Klaus Heger. The exonuclease TREX1 constitutes an innate immune checkpoint limiting cGAS/STING-mediated anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB361.

The Exonuclease TREX1 Constitutes an Innate Immune Checkpoint Limiting cGAS/STING-Mediated Antitumor Immunity.

The DNA exonuclease three-prime repair exonuclease 1 (TREX1) is critical for preventing autoimmunity in mice and humans by degrading endogenous cytosolic DNA, which otherwise triggers activation of the innate cGAS/STING pathway leading to the production of type I IFNs. As tumor cells are prone to aberrant cytosolic DNA accumulation, we hypothesized that they are critically dependent on TREX1 activity to limit their immunogenicity. Here, we show that in tumor cells, TREX1 restricts spontaneous activation of the cGAS/STING pathway, and the subsequent induction of a type I IFN response. As a result, TREX1 deficiency compromised in vivo tumor growth in mice. This delay in tumor growth depended on a functional immune system, systemic type I IFN signaling, and tumor-intrinsic cGAS expression. Mechanistically, we show that tumor TREX1 loss drove activation of CD8+ T cells and NK cells, prevented CD8+ T-cell exhaustion, and remodeled an immunosuppressive myeloid compartment. Consequently, TREX1 deficiency combined with T-cell-directed immune checkpoint blockade. Collectively, we conclude that TREX1 is essential to limit tumor immunogenicity, and that targeting this innate immune checkpoint remodels the tumor microenvironment and enhances antitumor immunity by itself and in combination with T-cell-targeted therapies. See related article by Toufektchan et al., p. 673.