Semmaphorin 3 A causes immune suppression by inducing cytoskeletal paralysis in tumour-specific CD8+ T cells.

Semaphorin-3A (SEMA3A) functions as a chemorepulsive signal during development and can affect T cells by altering their filamentous actin (F-actin) cytoskeleton. The exact extent of these effects on tumour-specific T cells are not completely understood. Here we demonstrate that Neuropilin-1 (NRP1) and Plexin-A1 and Plexin-A4 are upregulated on stimulated CD8+ T cells, allowing tumour-derived SEMA3A to inhibit T cell migration and assembly of the immunological synapse. Deletion of NRP1 in both CD4+ and CD8+ T cells enhance CD8+ T-cell infiltration into tumours and restricted tumour growth in animal models. Conversely, over-expression of SEMA3A inhibit CD8+ T-cell infiltration. We further show that SEMA3A affects CD8+ T cell F-actin, leading to inhibition of immune synapse formation and motility. Examining a clear cell renal cell carcinoma patient cohort, we find that SEMA3A expression is associated with reduced survival, and that T-cells appear trapped in SEMA3A rich regions. Our study establishes SEMA3A as an inhibitor of effector CD8+ T cell tumour infiltration, suggesting that blocking NRP1 could improve T cell function in tumours.

Tumor monocyte content predicts immunochemotherapy outcomes in esophageal adenocarcinoma.

For inoperable esophageal adenocarcinoma (EAC), identifying patients likely to benefit from recently approved immunochemotherapy (ICI+CTX) treatments remains a key challenge. We address this using a uniquely designed window-of-opportunity trial (LUD2015-005), in which 35 inoperable EAC patients received first-line immune checkpoint inhibitors for four weeks (ICI-4W), followed by ICI+CTX. Comprehensive biomarker profiling, including generation of a 65,000-cell single-cell RNA-sequencing atlas of esophageal cancer, as well as multi-timepoint transcriptomic profiling of EAC during ICI-4W, reveals a novel T cell inflammation signature (INCITE) whose upregulation correlates with ICI-induced tumor shrinkage. Deconvolution of pre-treatment gastro-esophageal cancer transcriptomes using our single-cell atlas identifies high tumor monocyte content (TMC) as an unexpected ICI+CTX-specific predictor of greater overall survival (OS) in LUD2015-005 patients and of ICI response in prevalent gastric cancer subtypes from independent cohorts. Tumor mutational burden is an additional independent and additive predictor of LUD2015-005 OS. TMC can improve patient selection for emerging ICI+CTX therapies in gastro-esophageal cancer.

HLA-E-restricted SARS-CoV-2-specific T cells from convalescent COVID-19 patients suppress virus replication despite HLA class Ia down-regulation.

Pathogen-specific CD8+ T cell responses restricted by the nonpolymorphic nonclassical class Ib molecule human leukocyte antigen E (HLA-E) are rarely reported in viral infections. The natural HLA-E ligand is a signal peptide derived from classical class Ia HLA molecules that interact with the NKG2/CD94 receptors to regulate natural killer cell functions, but pathogen-derived peptides can also be presented by HLA-E. Here, we describe five peptides from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that elicited HLA-E-restricted CD8+ T cell responses in convalescent patients with coronavirus disease 2019. These T cell responses were identified in the blood at frequencies similar to those reported for classical HLA-Ia-restricted anti-SARS-CoV-2 CD8+ T cells. HLA-E peptide-specific CD8+ T cell clones, which expressed diverse T cell receptors, suppressed SARS-CoV-2 replication in Calu-3 human lung epithelial cells. SARS-CoV-2 infection markedly down-regulated classical HLA class I expression in Calu-3 cells and primary reconstituted human airway epithelial cells, whereas HLA-E expression was not affected, enabling T cell recognition. Thus, HLA-E-restricted T cells could contribute to the control of SARS-CoV-2 infection alongside classical T cells.

PemBla: A Phase 1 study of intravesical pembrolizumab in recurrent non-muscle-invasive bladder cancer.

Objectives: This study aimed to investigate the anti-PD-1 inhibitor pembrolizumab as a potential agent for use in non-muscle-invasive bladder cancer (NMIBC) by conducting a Phase 1 safety run-in study to assess the safety and tolerability of intravesical pembrolizumab after transurethral resection of the bladder tumour (TURBT). Patients and methods: Eligible patients had recurrent NMIBC for which adjuvant treatment post TURBT was a reasonable treatment option, Eastern Cooperative Oncology Group Performance Status (ECOG PS) 0-1 and adequate end-organ function. Pembrolizumab was administered by intravesical instillation once weekly for a total of six doses. Intra-patient dose escalation was performed in three paired patient cohorts with doses starting at 50 mg and increasing through 100 mg to a maximum of 200 mg. Adverse events (AEs) were assessed using Common Terminology Criteria for Adverse Events (CTCAE) v4.03 with dose limiting toxicity (DLT) defined as a clinically significant, drug-related, Grade 4 haematological or Grade 3 or higher non-haematological toxicity occurring within 7 days of administration of the first treatment at a given dose for that patient. Results: Six patients were treated with no DLTs seen during dose escalation. Drug-related AEs were of low grade and included dysuria and fatigue. All patients completed six doses of treatment as planned. Pharmacokinetic and pharmacodynamic assays did not detect any pembrolizumab in the serum following repeated intravesical administration, and no changes in peripheral immune cell populations were observed. Conclusions: Administration of intravesical pembrolizumab was well tolerated and did not raise any safety concerns in patients with NMIBC following TURBT. There was no evidence of systemic absorption or systemic immune effects following intravesical administration. Further studies are required to assess whether intravesical administration has anti-tumour activity.

Evaluating performance of existing computational models in predicting CD8+ T cell pathogenic epitopes and cancer neoantigens.

T cell recognition of a cognate peptide-major histocompatibility complex (pMHC) presented on the surface of infected or malignant cells is of the utmost importance for mediating robust and long-term immune responses. Accurate predictions of cognate pMHC targets for T cell receptors would greatly facilitate identification of vaccine targets for both pathogenic diseases and personalized cancer immunotherapies. Predicting immunogenic peptides therefore has been at the center of intensive research for the past decades but has proven challenging. Although numerous models have been proposed, performance of these models has not been systematically evaluated and their success rate in predicting epitopes in the context of human pathology has not been measured and compared. In this study, we evaluated the performance of several publicly available models, in identifying immunogenic CD8+ T cell targets in the context of pathogens and cancers. We found that for predicting immunogenic peptides from an emerging virus such as severe acute respiratory syndrome coronavirus 2, none of the models perform substantially better than random or offer considerable improvement beyond HLA ligand prediction. We also observed suboptimal performance for predicting cancer neoantigens. Through investigation of potential factors associated with ill performance of models, we highlight several data- and model-associated issues. In particular, we observed that cross-HLA variation in the distribution of immunogenic and non-immunogenic peptides in the training data of the models seems to substantially confound the predictions. We additionally compared key parameters associated with immunogenicity between pathogenic peptides and cancer neoantigens and observed evidence for differences in the thresholds of binding affinity and stability, which suggested the need to modulate different features in identifying immunogenic pathogen versus cancer peptides. Overall, we demonstrate that accurate and reliable predictions of immunogenic CD8+ T cell targets remain unsolved; thus, we hope our work will guide users and model developers regarding potential pitfalls and unsettled questions in existing immunogenicity predictors.

Decitabine increases neoantigen and cancer testis antigen expression to enhance T-cell-mediated toxicity against glioblastoma.

BACKGROUND: Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. Despite maximal treatment, median survival remains dismal at 14-24 months. Immunotherapies, such as checkpoint inhibition, have revolutionized management of some cancers but have little benefit for GBM patients. This is, in part, due to the low mutational and neoantigen burden in this immunogenically "cold" tumor. METHODS: U87MG and patient-derived cell lines were treated with 5-aza-2'-deoxycytidine (DAC) and underwent whole-exome and transcriptome sequencing. Cell lines were then subjected to cellular assays with neoantigen and cancer testis antigen (CTA) specific T cells. RESULTS: We demonstrate that DAC increases neoantigen and CTA mRNA expression through DNA hypomethylation. This results in increased neoantigen presentation by MHC class I in tumor cells, leading to increased neoantigen- and CTA-specific T-cell activation and killing of DAC-treated cancer cells. In addition, we show that patients have endogenous cancer-specific T cells in both tumor and blood, which show increased tumor-specific activation in the presence of DAC-treated cells. CONCLUSIONS: Our work shows that DAC increases GBM immunogenicity and consequent susceptibility to T-cell responses in vitro. Our results support a potential use of DAC as a sensitizing agent for immunotherapy.

HLA-E-restricted, Gag-specific CD8+ T cells can suppress HIV-1 infection, offering vaccine opportunities.

Human leukocyte antigen-E (HLA-E) normally presents an HLA class Ia signal peptide to the NKG2A/C-CD94 regulatory receptors on natural killer (NK) cells and T cell subsets. Rhesus macaques immunized with a cytomegalovirus-vectored simian immunodeficiency virus (SIV) vaccine generated Mamu-E (HLA-E homolog)-restricted T cell responses that mediated post-challenge SIV replication arrest in >50% of animals. However, HIV-1-specific, HLA-E-restricted T cells have not been observed in HIV-1-infected individuals. Here, HLA-E-restricted, HIV-1-specific CD8 + T cells were primed in vitro. These T cell clones and allogeneic CD8 + T cells transduced with their T cell receptors suppressed HIV-1 replication in CD4 + T cells in vitro. Vaccine induction of efficacious HLA-E-restricted HIV-1-specific T cells should therefore be possible.

Enhanced Immunogenicity of Mitochondrial-Localized Proteins in Cancer Cells.

Epitopes derived from mutated cancer proteins elicit strong antitumor T-cell responses that correlate with clinical efficacy in a proportion of patients. However, it remains unclear whether the subcellular localization of mutated proteins influences the efficiency of T-cell priming. To address this question, we compared the immunogenicity of NY-ESO-1 and OVA localized either in the cytosol or in mitochondria. We showed that tumors expressing mitochondrial-localized NY-ESO-1 and OVA proteins elicit significantdly higher frequencies of antigen-specific CD8+ T cells in vivo. We also demonstrated that this stronger immune response is dependent on the mitochondrial location of the antigenic proteins, which contributes to their higher steady-state amount, compared with cytosolic localized proteins. Consistent with these findings, we showed that injection of mitochondria purified from B16 melanoma cells can protect mice from a challenge with B16 cells, but not with irrelevant tumors. Finally, we extended these findings to cancer patients by demonstrating the presence of T-cell responses specific for mutated mitochondrial-localized proteins. These findings highlight the utility of prioritizing epitopes derived from mitochondrial-localized mutated proteins as targets for cancer vaccination strategies.

Publisher Correction: Clonal analysis of Salmonella-specific effector T cells reveals serovar-specific and cross-reactive T cell responses.

In the version of this article initially published, the first affiliation lacked 'MRC'; the correct name of the institution is 'MRC Weatherall Institute of Molecular Medicine'. Two designations (SP110Y and ST110H) were incorrect in the legend to Fig. 6f,h,i. The correct text is as follows: for panel f, "...loaded with either the CdtB(105-125)SP110Y (DRB4*SP110Y) or the CdtB(105-125)ST110H (DRB4*ST110H) peptide variants..."; for panel h, "...decorated by the DRB4*SP110Y tetramer (lower-right quadrant), the DRB4*ST110H (upper-left quadrant)..."; and for panel i, "...stained ex vivo with DRB4*SP110Y, DRB4*ST110H...". In Fig. 8e, the final six residues (LTEAFF) of the sequence in the far right column of the third row of the table were missing; the correct sequence is 'CASSYRRTPPLTEAFF'. In the legend to Fig. 8d, a designation (HLyE) was incorrect; the correct text is as follows: "(HlyE?)." Portions of the Acknowledgements section were incorrect; the correct text is as follows: "This work was supported by the UK Medical Research Council (MRC) (MR/K021222/1) (G.N., M.A.G., A.S., V.C., A.J.P.),...the Oxford Biomedical Research Centre (A.J.P., V.C.),...and core funding from the Singapore Immunology Network (SIgN) (E.W.N.) and the SIgN immunomonitoring platform (E.W.N.)." Finally, a parenthetical element was phrased incorrectly in the final paragraph of the Methods subsection "T cell cloning and live fluorescence barcoding"; the correct phrasing is as follows: "...(which in all cases included HlyE, CdtB, Ty21a, Quailes, NVGH308, and LT2 strains and in volunteers T5 and T6 included PhoN)...". Also, in Figs. 3c and 4a, the right outlines of the plots were not visible; in the legend to Fig. 3, panel letter 'f' was not bold; and in Fig. 8f, 'ND' should be aligned directly beneath DRB4 in the key and 'ND' should be removed from the diagram at right, and the legend should be revised accordingly as follows: "...colors indicate the HLA class II restriction (gray indicates clones for which restriction was not determined (ND)). Clonotypes are grouped on the basis of pathogen selectivity (continuous line), protein specificity (dashed line) and epitope specificity; for ten HlyE-specific clones (pixilated squares), the epitope specificity was not determined...". The errors have been corrected in the HTML and PDF versions of the article.

Clonal analysis of Salmonella-specific effector T cells reveals serovar-specific and cross-reactive T cell responses.

To tackle the complexity of cross-reactive and pathogen-specific T cell responses against related Salmonella serovars, we used mass cytometry, unbiased single-cell cloning, live fluorescence barcoding, and T cell-receptor sequencing to reconstruct the Salmonella-specific repertoire of circulating effector CD4+ T cells, isolated from volunteers challenged with Salmonella enterica serovar Typhi (S. Typhi) or Salmonella Paratyphi A (S. Paratyphi). We describe the expansion of cross-reactive responses against distantly related Salmonella serovars and of clonotypes recognizing immunodominant antigens uniquely expressed by S. Typhi or S. Paratyphi A. In addition, single-amino acid variations in two immunodominant proteins, CdtB and PhoN, lead to the accumulation of T cells that do not cross-react against the different serovars, thus demonstrating how minor sequence variations in a complex microorganism shape the pathogen-specific T cell repertoire. Our results identify immune-dominant, serovar-specific, and cross-reactive T cell antigens, which should aid in the design of T cell-vaccination strategies against Salmonella.

Tumor-associated neutrophils suppress pro-tumoral IL-17+ γδ T cells through induction of oxidative stress.

Interleukin 17 (IL-17)-producing γδ T cells (γδ17 T cells) have been recently found to promote tumor growth and metastasis formation. How such γδ17 T-cell responses may be regulated in the tumor microenvironment remains, however, largely unknown. Here, we report that tumor-associated neutrophils can display an overt antitumor role by strongly suppressing γδ17 T cells. Tumor-associated neutrophils inhibited the proliferation of murine CD27- Vγ6+ γδ17 T cells via induction of oxidative stress, thereby preventing them from constituting the major source of pro-tumoral IL-17 in the tumor microenvironment. Mechanistically, we found that low expression of the antioxidant glutathione in CD27- γδ17 T cells renders them particularly susceptible to neutrophil-derived reactive oxygen species (ROS). Consistently, superoxide deficiency, or the administration of a glutathione precursor, rescued CD27- Vγ6+ γδ17 T-cell proliferation in vivo. Moreover, human Vδ1+ γδ T cells, which contain most γδ17 T cells found in cancer patients, also displayed low glutathione levels and were potently inhibited by ROS. This work thus identifies an unanticipated, immunosuppressive yet antitumoral, neutrophil/ROS/γδ17 T-cell axis in the tumor microenvironment.

Somatic POLE exonuclease domain mutations are early events in sporadic endometrial and colorectal carcinogenesis, determining driver mutational landscape, clonal neoantigen burden and immune response.

Genomic instability, which is a hallmark of cancer, is generally thought to occur in the middle to late stages of tumourigenesis, following the acquisition of permissive molecular aberrations such as TP53 mutation or whole genome doubling. Tumours with somatic POLE exonuclease domain mutations are notable for their extreme genomic instability (their mutation burden is among the highest in human cancer), distinct mutational signature, lymphocytic infiltrate, and excellent prognosis. To what extent these characteristics are determined by the timing of POLE mutations in oncogenesis is unknown. Here, we have shown that pathogenic POLE mutations are detectable in non-malignant precursors of endometrial and colorectal cancer. Using genome and exome sequencing, we found that multiple driver mutations in POLE-mutant cancers show the characteristic POLE mutational signature, including those in genes conventionally regarded as initiators of tumourigenesis. In POLE-mutant cancers, the proportion of monoclonal predicted neoantigens was similar to that in other cancers, but the absolute number was much greater. We also found that the prominent CD8+ T-cell infiltrate present in POLE-mutant cancers was evident in their precursor lesions. Collectively, these data indicate that somatic POLE mutations are early, quite possibly initiating, events in the endometrial and colorectal cancers in which they occur. The resulting early onset of genomic instability may account for the striking immune response and excellent prognosis of these tumours, as well as their early presentation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

MAIT cell clonal expansion and TCR repertoire shaping in human volunteers challenged with Salmonella Paratyphi A.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can detect bacteria-derived metabolites presented on MR1. Here we show, using a controlled infection of humans with live Salmonella enterica serovar Paratyphi A, that MAIT cells are activated during infection, an effect maintained even after antibiotic treatment. At the peak of infection MAIT cell T-cell receptor (TCR)ß clonotypes that are over-represented prior to infection transiently contract. Select MAIT cell TCRß clonotypes that expand after infection have stronger TCR-dependent activation than do contracted clonotypes. Our results demonstrate that host exposure to antigen may drive clonal expansion of MAIT cells with increased functional avidity, suggesting a role for specific vaccination strategies to increase the frequency and potency of MAIT cells to optimize effector function.

Effect of MUC1/ß-catenin interaction on the tumorigenic capacity of pancreatic CD133+ cells.

Despite the fact that the biological function of cluster of differentiation (CD)133 remains unclear, this glycoprotein is currently used in the identification and isolation of tumor-initiating cells from certain malignant tumors, including pancreatic cancer. In the present study, the involvement of mucin 1 (MUC1) in the signaling pathways of a highly tumorigenic CD133+ cellular subpopulation sorted from the pancreatic cancer cell line HPAF-II was evaluated. The expression of MUC1-cytoplasmic domain (MUC1-CD) and oncogenic signaling transducers (epidermal growth factor receptor, protein kinase C delta, glycogen synthase kinase 3 beta and growth factor receptor-bound protein 2), as well as the association between MUC1 and ß-catenin, were characterized in HPAF-II CD133+ and CD133low cell subpopulations and in tumor xenografts generated from these cells. Compared with HPAF CD133low cells, HPAF-II CD133+ cancer cells exhibited increased tumorigenic potential in immunocompromised mice, which was associated with overexpression of MUC1 and with the accordingly altered expression profile of MUC1-associated signaling partners. Additionally, MUC1-CD/ß-catenin interactions were increased both in the HPAF-II CD133+ cell subpopulation and derived tumor xenografts compared with HPAF CD133low cells. These results suggest that, in comparison with HPAF CD133low cells, CD133+ cells exhibit higher expression of MUC1, which contributes to their tumorigenic phenotype through increased interaction between MUC1-CD and ß-catenin, which in turn modulates oncogenic signaling cascades.

The emerging Protumor role of γδ T lymphocytes: implications for cancer immunotherapy.

Tumor-infiltrating lymphocytes are key mediators of tumor immune surveillance and are important prognostic indicators in cancer progression. Among the various lymphocyte subsets implicated in protection against cancer are γδ T lymphocytes, which can kill tumor cells and secrete potent antitumor cytokines. By contrast, recent reports have revealed an unexpected series of protumor functions of γδ T cells in mouse models and human patients. In particular, specific γδ T-cell subsets are capable of recruiting immunosuppressive myeloid populations, inhibiting antitumor responses, and enhancing angiogenesis, thus promoting cancer progression. A common mediator of such functions appears to be the cytokine IL17, whose pathogenic effects can override the antitumor immune response orchestrated by IFNγ. Here, we review these studies and discuss their implications for the manipulation of γδ T cells in cancer immunotherapy.

Murine CD27(-) Vγ6(+) γδ T cells producing IL-17A promote ovarian cancer growth via mobilization of protumor small peritoneal macrophages.

Cancer-associated inflammation mobilizes a variety of leukocyte populations that can inhibit or enhance tumor cell growth in situ. These subsets include γδ T cells, which can infiltrate tumors and typically provide large amounts of antitumor cytokines, such as IFN-γ. By contrast, we report here that in a well-established transplantable (ID8 cell line) model of peritoneal/ovarian cancer, γδ T cells promote tumor cell growth. γδ T cells accumulated in the peritoneal cavity in response to tumor challenge and could be visualized within solid tumor foci. Functional characterization of tumor-associated γδ T cells revealed preferential production of interleukin-17A (IL-17), rather than IFN-γ. Consistent with this finding, both T cell receptor (TCR)δ-deficient and IL-17-deficient mice displayed reduced ID8 tumor growth compared with wild-type animals. IL-17 production by γδ T cells in the tumor environment was essentially restricted to a highly proliferative CD27((-)) subset that expressed Vγ6 instead of the more common Vγ1 and Vγ4 TCR chains. The preferential expansion of IL-17-secreting CD27((-)) Vγ6((+)) γδ T cells associated with the selective mobilization of unconventional small peritoneal macrophages (SPMs) that, in comparison with large peritoneal macrophages, were enriched for IL-17 receptor A, and for protumor and proangiogenic molecular mediators, which were up-regulated by IL-17. Importantly, SPMs were uniquely and directly capable of promoting ovarian cancer cell proliferation. Collectively, this work identifies an IL-17-dependent lymphoid/myeloid cross-talk involving γδ T cells and SPMs that promotes tumor cell growth and thus counteracts cancer immunosurveillance.

Epigenetic and transcriptional signatures of stable versus plastic differentiation of proinflammatory γδ T cell subsets.

Two distinct subsets of γδ T cells that produce interleukin 17 (IL-17) (CD27(-) γδ T cells) or interferon-γ (IFN-γ) (CD27(+) γδ T cells) develop in the mouse thymus, but the molecular determinants of their functional potential in the periphery remain unknown. Here we conducted a genome-wide characterization of the methylation patterns of histone H3, along with analysis of mRNA encoding transcription factors, to identify the regulatory networks of peripheral IFN-γ-producing or IL-17-producing γδ T cell subsets in vivo. We found that CD27(+) γδ T cells were committed to the expression of Ifng but not Il17, whereas CD27(-) γδ T cells displayed permissive chromatin configurations at loci encoding both cytokines and their regulatory transcription factors and differentiated into cells that produced both IL-17 and IFN-γ in a tumor microenvironment.

Protective role of the inflammatory CCR2/CCL2 chemokine pathway through recruitment of type 1 cytotoxic γδ T lymphocytes to tumor beds.

Tumor-infiltrating lymphocytes (TILs) are important prognostic factors in cancer progression and key players in cancer immunotherapy. Although γδ T lymphocytes can target a diversity of tumor cell types, their clinical manipulation is hampered by our limited knowledge of the molecular cues that determine γδ T cell migration toward tumors in vivo. In this study we set out to identify the chemotactic signals that orchestrate tumor infiltration by γδ T cells. We have used the preclinical transplantable B16 melanoma model to profile chemokines in tumor lesions and assess their impact on γδ TIL recruitment in vivo. We show that the inflammatory chemokine CCL2 and its receptor CCR2 are necessary for the accumulation of γδ TILs in B16 lesions, where they produce IFN-γ and display potent cytotoxic functions. Moreover, CCL2 directed γδ T cell migration in vitro toward tumor extracts, which was abrogated by anti-CCL2 neutralizing Abs. Strikingly, the lack of γδ TILs in TCRδ-deficient but also in CCR2-deficient mice enhanced tumor growth in vivo, thus revealing an unanticipated protective role for CCR2/CCL2 through the recruitment of γδ T cells. Importantly, we demonstrate that human Vδ1 T cells, but not their Vδ2 counterparts, express CCR2 and migrate to CCL2, whose expression is strongly deregulated in multiple human tumors of diverse origin, such as lung, prostate, liver, or breast cancer. This work identifies a novel protective role for CCL2/CCR2 in the tumor microenvironment, while opening new perspectives for modulation of human Vδ1 T cells in cancer immunotherapy.