Membrane-associated and secreted forms of the Rhesus macaque rhadinovirus-encoded CD200 homologue and cellular CD200 demonstrate differential effects on Rhesus Macaque CD200 Receptor signaling and regulation of myeloid cell activation.

The CD200-CD200R pathway is involved in inhibition of immune responses, and the importance of this pathway to infectious disease is highlighted by the fact that viral CD200 (vCD200) molecules have been found to be encoded by several DNA viruses, including the human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV), and the closely related rhesus macaque rhadinovirus (RRV). KSHV vCD200 is the most extensively studied vCD200 molecule, however, the only herpesvirus vCD200 molecule to be examined in vivo is that encoded by RRV. Our prior studies have demonstrated that RRV vCD200 is a functional CD200 homologue that is capable of affecting immune responses in vivo, and further, that RRV can express a secreted form of vCD200 (vCD200-Sec) during infection. Despite this information, RRV vCD200 has not been examined specifically for effects on RM CD200R signaling, and the functionality of vCD200-Sec has not been examined in any context. Thus, we developed an in vitro model system in which B cells expressing vCD200 were utilized to assess the effects of this molecule on the regulation of myeloid cells expressing RM CD200R, mimicking interactions that are predicted to occur in vivo Our findings suggest that RRV vCD200 can bind and induce functional signals through RM CD200R, while vCD200-Sec represents a non-functional protein incapable of affecting CD200R signaling. We also provide the first demonstration of the function of RM CD200, which appears to possess more robust signaling capabilities than RRV vCD200, and also show that KSHV vCD200 does not efficiently induce signaling via RM CD200R.IMPORTANCE Viral CD200 homologues are encoded by KSHV and the closely related RRV. Though RRV vCD200 has been examined, questions still exist in regard to the ability of this molecule to induce signaling via rhesus macaque CD200R, as well as the potential function of a secreted form of vCD200. Further, all previous in vitro studies of RRV vCD200 have utilized an Fc fusion protein to examine functionality, which does not replicate the structural properties of the membrane-associated form of vCD200 that is naturally produced during RRV infection. In this study, we demonstrate for the first time that membrane-expressed RRV vCD200 is capable of inducing signal transduction via RM CD200R, while the secreted form of vCD200 appears to be non-functional. Further, we also demonstrate that RM CD200 induces signaling via RM CD200R, and is more robust than RRV vCD200, while KSHV vCD200 does not appear to induce efficient signaling via RM CD200R.

Dendritic Cell Maturation Defines Immunological Responsiveness of Tumors to Radiation Therapy.

Radiation therapy is capable of directing adaptive immune responses against tumors by stimulating the release of endogenous adjuvants and tumor-associated Ags. Within the tumor, conventional type 1 dendritic cells (cDC1s) are uniquely positioned to respond to these signals, uptake exogenous tumor Ags, and migrate to the tumor draining lymph node to initiate cross-priming of tumor-reactive cytotoxic CD8+ T cells. In this study, we report that radiation therapy promotes the activation of intratumoral cDC1s in radioimmunogenic murine tumors, and this process fails to occur in poorly radioimmunogenic murine tumors. In poorly radioimmunogenic tumors, the adjuvant polyinosinic-polycytidylic acid overcomes this failure following radiation and successfully drives intratumoral cDC1 maturation, ultimately resulting in durable tumor cures. Depletion studies revealed that both cDC1 and CD8+ T cells are required for tumor regression following combination therapy. We further demonstrate that treatment with radiation and polyinosinic-polycytidylic acid significantly expands the proportion of proliferating CD8+ T cells in the tumor with enhanced cytolytic potential and requires T cell migration from lymph nodes for therapeutic efficacy. Thus, we conclude that lack of endogenous adjuvant release or active suppression following radiation therapy may limit its efficacy in poorly radioimmunogenic tumors, and coadministration of exogenous adjuvants that promote cDC1 maturation and migration can overcome this limitation to improve tumor control following radiation therapy.

Japanese Macaque Rhadinovirus Encodes a Viral MicroRNA Mimic of the miR-17 Family.

UNLABELLED: Japanese macaque (JM) rhadinovirus (JMRV) is a novel, gamma-2 herpesvirus that was recently isolated from JM with inflammatory demyelinating encephalomyelitis (JME). JME is a spontaneous and chronic disease with clinical characteristics and immunohistopathology comparable to those of multiple sclerosis in humans. Little is known about the molecular biology of JMRV. Here, we sought to identify and characterize the small RNAs expressed during lytic JMRV infection using deep sequencing. Fifteen novel viral microRNAs (miRNAs) were identified in JMRV-infected fibroblasts, all of which were readily detectable by 24 h postinfection and accumulated to high levels by 72 h. Sequence comparisons to human Kaposi's sarcoma-associated herpesvirus (KSHV) miRNAs revealed several viral miRNA homologs. To functionally characterize JMRV miRNAs, we screened for their effects on nuclear factor kappa B (NF-κB) signaling in the presence of two proinflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-1ß (IL-1ß). Multiple JMRV miRNAs suppressed cytokine-induced NF-κB activation. One of these miRNAs, miR-J8, has seed sequence homology to members of the cellular miR-17/20/106 and miR-373 families, which are key players in cell cycle regulation as well as inflammation. Using reporters, we show that miR-J8 can target 3' untranslated regions (UTRs) with miR-17-5p or miR-20a cognate sites. Our studies implicate JMRV miRNAs in the suppression of innate antiviral immune responses, which is an emerging feature of many viral miRNAs. IMPORTANCE: Gammaherpesviruses are associated with multiple diseases linked to immunosuppression and inflammation, including AIDS-related cancers and autoimmune diseases. JMRV is a recently identified herpesvirus that has been linked to JME, an inflammatory demyelinating disease in Japanese macaques that mimics multiple sclerosis. There are few large-animal models for gammaherpesvirus-associated pathogenesis. Here, we provide the first experimental evidence of JMRV miRNAs in vitro and demonstrate that one of these viral miRNAs can mimic the activity of the cellular miR-17/20/106 family. Our work provides unique insight into the roles of viral miRNAs during rhadinovirus infection and provides an important step toward understanding viral miRNA function in a nonhuman primate model system.

Cutting edge: the pathogenicity of IFN-γ-producing Th17 cells is independent of T-bet.

During the development of experimental autoimmune encephalomyelitis (EAE), the proportion of pathogenic and myelin-specific cells within CNS-infiltrating cytokine-producing Th cells is unknown. Using an IL-17A/IFN-γ double reporter mouse and I-A(b)/myelin oligodendrocyte glycoprotein 38-49 tetramer, we show in this study that IL-17(+)IFN-γ(+) Th cells, which are expanded in the CNS during EAE, are highly enriched in myelin oligodendrocyte glycoprotein-specific T cells. We further demonstrate that IL-23 is essential for the generation and expansion of IFN-γ-producing Th17 cells independently of the Th1-associated transcription factors T-bet, STAT1, and STAT4. Furthermore, Th17 and IL-17(+)IFN-γ(+) Th cells can induce CNS autoimmunity independently of T-bet. Whereas T-bet is crucial for Th1-mediated EAE, it is dispensable for Th17 cell-mediated autoimmunity. Our results suggest the existence of different epigenetic programs that regulate IFN-γ expression in Th1 and Th17 cells.

Fluorescence tracking demonstrates T cell recirculation is transiently impaired by radiation therapy to the tumor.

T cells recirculate through tissues and lymphatic organs to scan for their cognate antigen. Radiation therapy provides site-specific cytotoxicity to kill cancer cells but also has the potential to eliminate the tumor-specific T cells in field. To dynamically study the effect of radiation on CD8 T cell recirculation, we used the Kaede mouse model to photoconvert tumor-infiltrating cells and monitor their movement out of the field of radiation. We demonstrate that radiation results in loss of CD8 T cell recirculation from the tumor to the lymph node and to distant sites. Using scRNASeq, we see decreased proliferating CD8 T cells in the tumor following radiation therapy resulting in a proportional enrichment in exhausted phenotypes. By contrast, 5 days following radiation increased recirculation of T cells from the tumor to the tumor draining lymph node corresponds with increased immunosurveillance of the treated tumor. These data demonstrate that tumor radiation therapy transiently impairs systemic T cell recirculation from the treatment site to the draining lymph node and distant untreated tumors. This may inform timing therapies to improve systemic T cell-mediated tumor immunity.

Myeloid MyD88 restricts CD8+ T cell response to radiation therapy in pancreatic cancer.

Radiation therapy induces immunogenic cell death in cancer cells, whereby released endogenous adjuvants are sensed by immune cells to direct adaptive immune responses. TLRs expressed on several immune subtypes recognize innate adjuvants to direct downstream inflammatory responses in part via the adapter protein MyD88. We generated Myd88 conditional knockout mice to interrogate its contribution to the immune response to radiation therapy in distinct immune populations in pancreatic cancer. Surprisingly, Myd88 deletion in Itgax (CD11c)-expressing dendritic cells had little discernable effects on response to RT in pancreatic cancer and elicited normal T cell responses using a prime/boost vaccination strategy. Myd88 deletion in Lck-expressing T cells resulted in similar or worsened responses to radiation therapy compared to wild-type mice and lacked antigen-specific CD8+ T cell responses from vaccination, similar to observations in Myd88-/- mice. Lyz2-specific loss of Myd88 in myeloid populations rendered tumors more susceptible to radiation therapy and elicited normal CD8+ T cell responses to vaccination. scRNAseq in Lyz2-Cre/Myd88fl/fl mice revealed gene signatures in macrophages and monocytes indicative of enhanced type I and II interferon responses, and improved responses to RT were dependent on CD8+ T cells and IFNAR1. Together, these data implicate MyD88 signaling in myeloid cells as a critical source of immunosuppression that hinders adaptive immune tumor control following radiation therapy.

Tumor resident memory CD8 T cells and concomitant tumor immunity develop independently of CD4 help.

Tissue resident memory (Trm) CD8 T cells infiltrating tumors represent an enriched population of tumor antigen-specific T cells, and their presence is associated with improved outcomes in patients. Using genetically engineered mouse pancreatic tumor models we demonstrate that tumor implantation generates a Trm niche that is dependent on direct antigen presentation by cancer cells. However, we observe that initial CCR7-mediated localization of CD8 T cells to tumor draining lymph nodes is required to subsequently generate CD103+ CD8 T cells in tumors. We observe that the formation of CD103+ CD8 T cells in tumors is dependent on CD40L but independent of CD4 T cells, and using mixed chimeras we show that CD8 T cells can provide their own CD40L to permit CD103+ CD8 T cell differentiation. Finally, we show that CD40L is required to provide systemic protection against secondary tumors. These data suggest that CD103+ CD8 T cell formation in tumors can occur independent of the two-factor authentication provided by CD4 T cells and highlight CD103+ CD8 T cells as a distinct differentiation decision from CD4-dependent central memory.

Non-Redundant Roles of T Cell Costimulation Pathways in Inflammatory Arthritis Revealed by Dual Blockade of ICOS and CD28 with Acazicolcept (ALPN-101).

OBJECTIVE: CD28 and inducible T cell costimulator (ICOS) appear to have nonredundant roles in T cell activation and adaptive immunity. We undertook this study to characterize in vitro and in vivo the therapeutic potential of acazicolcept (ALPN-101), an Fc fusion protein of a human variant ICOS ligand (ICOSL) domain designed to inhibit both CD28 and ICOS costimulation, in inflammatory arthritis. METHODS: Acazicolcept was compared in vitro with inhibitors of either the CD28 or ICOS pathways (abatacept and belatacept [CTLA-4Ig], prezalumab [anti-ICOSL monoclonal antibody]) in receptor binding and signaling assays, and in a collagen-induced arthritis (CIA) model. Acazicolcept was also compared in cytokine and gene expression assays of peripheral blood mononuclear cells (PBMCs) from healthy donors or rheumatoid arthritis (RA) or psoriatic arthritis (PsA) patients stimulated with artificial antigen-presenting cells (APCs) expressing CD28 and ICOS ligands*. RESULTS: Acazicolcept bound CD28 and ICOS, prevented ligand binding, and inhibited human T cell functional interactions, matching or exceeding the activity of CD28 or ICOS costimulatory single-pathway inhibitors tested individually or in combination. Acazicolcept administration significantly reduced disease in the CIA model and more potently than abatacept. Acazicolcept also inhibited proinflammatory cytokine production from stimulated PBMCs in cocultures with artificial APCs and demonstrated unique effects on gene expression distinct from those induced by abatacept, prezalumab, or a combination of both. CONCLUSION: Both CD28 and ICOS signaling play critical roles in inflammatory arthritis. Therapeutic agents such as acazicolcept that coinhibit both ICOS and CD28 signaling may mitigate inflammation and/or disease progression in RA and PsA more effectively than inhibitors of either pathway alone.

Program Report: Nîsohkamâtowak-Helping Patients and Families Living With Kidney Disease in Northern Saskatchewan.

PURPOSE OF THE PROGRAM: Nîsohkamâtowak, the Cree word for Helping Each Other, is an initiative to close gaps in kidney health care for First Nations and Métis patients, their families, and communities in northern Saskatchewan. Nîsohkamâtowak emerged from a collaboration between the Kidney Health Community Program and First Nations and Métis Health Services to find ways to deliver better care and education to First Nations and Métis people living with kidney disease while acknowledging Truth and Reconciliation and the Calls to Action. SOURCES OF INFORMATION: This article describes how traditional Indigenous protocols and storytelling were woven into the Nîsohkamâtowak events, gathering of patient and family voices in writing and video format, and how this work led to a collaborative co-designed process that incorporates the Truth and Reconciliation: Calls to Action into kidney care and the benefits we have seen so far. The teachings of the 4 Rs-respect, reciprocity, responsibility, and relevance, were critical to ensuring that Nîsohkamâtowak reports and learning were shared with participants and the communities represented in this initiative. METHODS: Group discussions and sharing circles were facilitated in several locations throughout northern and central Saskatchewan. Main topics of discussion were traditional medicines, residential schools impact, community and peer supports for kidney disease patients, and cultural safety education for health care providers. KEY FINDINGS: The general themes selected for improvement were education, support within the local community, traditional practices and cultural competency, and delivery of services. To address these gaps in kidney care, the following objectives were co-created with First Nations and Métis patients, families, and communities for Kidney Health to provide culturally appropriate education and resources, to ensure appropriate follow-up support to include strengthening connections to communities and other health authorities, to incorporate traditional practices into program design, and to ensure appropriate service delivery across the spectrum of care with a focus on screening and referral, which is strongly linked to coordination of care with local health centers. IMPLICATIONS: As a result of this work, the Kidney Health Community Program restructured the delivery of services and continues to work with Nîsohkamâtowak advisors on safety initiatives and chronic kidney disease awareness, prevention, and management in their respective communities. The Truth and Reconciliation and Calls to Action are honored to close the gaps in kidney care. LIMITATIONS: Nîsohkamâtowak is a local Kidney Health initiative that has the good fortune of having dedicated funding and staff to carry out this work. The findings may be unique to the First Nations and Métis communities and people who shared their stories. Truth and Reconciliation is an ongoing commitment that must be nurtured. Although not part of this publication, the effects of COVID-19 have made it difficult to further advance the Calls to Action, with more limited staff resources and the inability to meet in person as in the past.

OBJECTIFS DU PROGRAMME: Nîsohkamâtowak, un terme cri signifiant « s'aider les uns les autres ¼, est une initiative qui vise à combler les lacunes dans les soins de santé rénaux pour les patients des Premières Nations et Métis, leurs familles et leurs collectivités du nord de la Saskatchewan. Nîsohkamâtowak est née d'une collaboration entre le Kidney Health Community Program et First Nations and Métis Health Services pour trouver des moyens d'offrir de meilleurs soins et une meilleure éducation aux membres des Premières Nations et aux Métis qui vivent avec une néphropathie, tout en reconnaissant les appels à l'action de la Commission de vérité et réconciliation du Canada. SOURCES: Cet article décrit comment les protocoles et récits autochtones traditionnels ont été intégrés aux événements de Nîsohkamâtowak, comment les voix des patients et des familles ont été recueillies par écrit et sous forme de vidéos, et comment ces travaux ont mené à un processus collaboratif de conception conjointe qui intègre les recommandations de Vérité et réconciliation : Appels à l'action dans les soins rénaux et qui a mené aux avantages constatés jusqu'à présent. L'enseignement des quatre grands principes ­ respect, réciprocité, responsabilité et pertinence ­ était essentiel pour assurer que les rapports et les apprentissages de Nîsohkamâtowak soient partagés avec les participants et les communautés représentées par cette initiative. PRINCIPAUX RÉSULTATS: Les thèmes généraux suivants ont été retenus pour amélioration : l'éducation, le soutien dans la communauté locale, les pratiques traditionnelles et les compétences culturelles, et la prestation des services. Pour combler ces lacunes dans les soins rénaux, les objectifs suivants liés à la santé rénale ont été développés conjointement avec les patients, les familles et les communautés des Premières Nations et des Métis: offrir une éducation et des ressources adaptées à la culture; assurer un soutien de suivi approprié, notamment en renforçant les liens avec les communautés et avec les autres autorités sanitaires; intégrer les pratiques traditionnelles dans la conception des programmes; et garantir la prestation appropriée des services dans tout l'éventail des soins, en mettant l'accent sur le dépistage et l'aiguillage, qui sont fortement liés à la coordination des soins avec les centres de santé locaux. RÉSULTATS: À la suite de ces travaux, le Kidney Health Community Program a restructuré la prestation des services et continue à ce jour de travailler avec les conseillers de Nîsohkamâtowak sur des initiatives de sécurité, ainsi que sur la sensibilisation, la prévention et la prise en charge de l'insuffisance rénale chronique dans leurs collectivités respectives. La Commission de vérité et réconciliation du Canada : appel à l'action est honorée de combler les lacunes dans les soins rénaux. LIMITES: Nîsohkamâtowak est une initiative locale de santé rénale qui bénéficie d'un financement et d'un personnel dédiés pour accomplir ce travail. Les résultats pourraient être propres aux communautés des Premières Nations et des Métis et aux personnes qui ont partagé leurs histoires. La Commission de vérité et réconciliation est un engagement permanent qui doit être soutenu. Bien que cela ne soit pas souligné dans cette publication, la pandémie de COVID-19 a rendu difficile l'avancement des appels à l'action en raison des ressources humaines plus limitées et de l'incapacité de se rencontrer en personne comme auparavant.

ICOS is upregulated on T cells following radiation and agonism combined with radiation results in enhanced tumor control.

Multiple preclinical studies have shown improved outcomes when radiation therapy is combined with immune modulating antibodies. However, to date, many of these promising results have failed to translate to successful clinical studies. This led us to explore additional checkpoint and co-stimulatory pathways that may be regulated by radiation therapy. Here, we demonstrate that radiation increases the expression of inducible T cell co-stimulator (ICOS) on both CD4 and CD8 T cells in the blood following treatment. Moreover, when we combined a novel ICOS agonist antibody with radiation we observed durable cures across multiple tumor models and mouse strains. Depletion studies revealed that CD8 T cells were ultimately required for treatment efficacy, but CD4 T cells and NK cells also partially contributed to tumor control. Phenotypic analysis showed that the combination therapy diminished the increased infiltration of regulatory T cells into the tumor that typically occurs following radiation alone. Finally, we demonstrate in a poorly immunogenic pancreatic tumor model which is resistant to combined radiation and anti-PD1 checkpoint blockade that the addition of this novel ICOS agonist antibody to the treatment regimen results in tumor control. These findings identify ICOS as part of a T cell pathway that is modulated by radiation and targeting this pathway with a novel ICOS antibody results in durable tumor control in preclinical models.

Fluorescent tracking identifies key migratory dendritic cells in the lymph node after radiotherapy.

Radiation therapy generates extensive cancer cell death capable of promoting tumor-specific immunity. Within the tumor, conventional dendritic cells (cDCs) are known to carry tumor-associated antigens to the draining lymph node (TdLN) where they initiate T-cell priming. How radiation influences cDC migration is poorly understood. Here, we show that immunological efficacy of radiation therapy is dependent on cDC migration in radioimmunogenic tumors. Using photoconvertible mice, we demonstrate that radiation impairs cDC migration to the TdLN in poorly radioimmunogenic tumors. Comparative transcriptional analysis revealed that cDCs in radioimmunogenic tumors express genes associated with activation of endogenous adjuvant signaling pathways when compared with poorly radioimmunogenic tumors. Moreover, an exogenous adjuvant combined with radiation increased the number of migrating cDCs in these poorly radioimmunogenic tumors. Taken together, our data demonstrate that cDC migration play a critical role in the response to radiation therapy.

Multiplatform comparison of multiplexed bead arrays using HPV genotyping as a test case.

While previous studies have investigated the utility of Luminex technology in comparison to other standard techniques, there have been few studies directly comparing different bead-based assays. A key barrier to establishing Luminex technology in research or clinical laboratories is the apparent need to purchase not only encoded bead sets but also the Luminex instrument. However, as flow cytometry instrumentation continues to improve in sensitivity and in the number and diversity of detection parameters, a diverse range of bead-based assays is likely to emerge. Human papillomavirus (HPV) genotyping requires multiplexed analysis of 10-100 individual genotypes per sample, which is well suited to bead-based assays whilst technically challenging and costly for related technologies (e.g., qPCR). Here we performed an unbiased technical comparison between Luminex technology and our in-house 3-mercaptopropyl trimethoxysilane ("MPS") bead platform, which has been designed for integration with generic cytometry instruments. In genotyping 200 clinical samples, we compared the two bead assays against the goldstandard Roche Line Blot (RLB) assay, and both performed well in receiver-operator characteristic (ROC) curve analysis. We also show instrument-based differences are a significant factor in comparing the methods, which needs to be considered in future comparative studies. These multi-platform analyses are important in establishing the validity of new methods, as well as highlighting specific advantages and disadvantages of the assays for specific applications.

Ultrasound guidance for the creation of a small animal model of aortic injury.

PURPOSE: To develop a small animal model of controlled aortic intimal injury with ultrasound (US) imaging guidance. MATERIALS AND METHODS: Via carotid artery cutdown, a custom-made microcatheter/angled metal device system was advanced to damage the intima of the ascending aortas of 20 Sprague-Dawley rats and 10 JCR atherosclerotic rats. This minimally invasive endovascular procedure was monitored by a clinical US imaging system. Injured aortas were harvested for histologic confirmation via a grading system: grade I, intima injury; grade II, injury to media; and grade III, injury through the entire aortic wall. Neointimal reactions at the injury site were compared by calculating the ratio of intimal to medial thickness among different animal groups at various survival times (week 1, weeks 2-3, and weeks 4-7). RESULTS: Clear visualization of the architecture of the heart and great vessels and the exact location of the angled metal device by US imaging ensured consistent intimal damage of the aorta. Histopathologic analysis confirmed that most of the aortic injures were classified as grade I. There was no significant difference between the two rat groups. Analysis of pathophysiologic reactions at the injury sites revealed increased thickening of neointimal hyperplasia as animal survival times extended from week 1 to weeks 4-7 after the aortic interventions. CONCLUSIONS: This study demonstrates the feasibility of clinical US imaging to precisely guide the creation of controlled aortic intimal injury in rats, which may become a useful tool to facilitate research involving the prevention and treatment of atherosclerotic cardiovascular disease.

Bisulfite-free analysis of 5MeC-binding proteins and locus-specific methylation density using a microparticle-based flow cytometry assay.

DNA methylation analysis is emerging as a new technique with potential capabilities for early cancer detection. However, current state-of-the-art techniques are not easily translatable into routine clinical methods. Herein we describe a bead-based flow cytometry assay which combines DNA hybridization to microparticles with 5MeC-specific proteins/antibodies. These assays can be used to study the binding properties of current and emerging 5MeC-binding proteins and may also have potential in the measurement of 5MeC density in clinical samples for cancer detection.

Defining Immunogenic and Radioimmunogenic Tumors.

In the cancer literature tumors are inconsistently labeled as 'immunogenic', and experimental results are occasionally dismissed since they are only tested in known 'responsive' tumor models. The definition of immunogenicity has moved from its classical definition based on the rejection of secondary tumors to a more nebulous definition based on immune infiltrates and response to immunotherapy interventions. This review discusses the basis behind tumor immunogenicity and the variation between tumor models, then moves to discuss how these principles apply to the response to radiation therapy. In this way we can identify radioimmunogenic tumor models that are particularly responsive to immunotherapy only when combined with radiation, and identify the interventions that can convert unresponsive tumors so that they can also respond to these treatments.

The Dynamic Entropy of Tumor Immune Infiltrates: The Impact of Recirculation, Antigen-Specific Interactions, and Retention on T Cells in Tumors.

Analysis of tumor infiltration using conventional methods reveals a snapshot view of lymphocyte interactions with the tumor environment. However, lymphocytes have the unique capacity for continued recirculation, exploring varied tissues for the presence of cognate antigens according to inflammatory triggers and chemokine gradients. We discuss the role of the inflammatory and cellular makeup of the tumor environment, as well as antigen expressed by cancer cells or cross-presented by stromal antigen presenting cells, on recirculation kinetics of T cells. We aim to discuss how current cancer therapies may manipulate lymphocyte recirculation versus retention to impact lymphocyte exclusion in the tumor.

A platform for locoregional T-cell immunotherapy to control HNSCC recurrence following tumor resection.

Surgical resection of head and neck squamous-cell carcinoma (HNSCC) is associated with high rates of local and distant recurrence, partially mitigated by adjuvant therapy. A pre-existing immune response in the patient's tumor is associated with better outcomes following treatment with conventional therapies, but improved options are needed for patients with poor anti-tumor immunity. We hypothesized that local delivery of tumor antigen-specific T-cells into the resection cavity following surgery would direct T-cells to residual antigens in the margins and draining lymphatics and present a platform for T-cell-targeted immunotherapy. We loaded T-cells into a biomaterial that conformed to the resection cavity and demonstrated that it could release T-cells that retained their functional activity in-vitro, and in a HNSCC model in-vivo. Locally delivered T-cells loaded in a biomaterial were equivalent in control of established tumors to intravenous adoptive T-cell transfer, and resulted in the systemic circulation of tumor antigen-specific T-cells as well as local accumulation in the tumor. We demonstrate that adjuvant therapy with anti-PD1 following surgical resection was ineffective unless combined with local delivery of T-cells. These data demonstrate that local delivery of tumor-specific T-cells is an efficient option to convert tumors that are unresponsive to checkpoint inhibitors to permit tumor cures.

Targeting MerTK Enhances Adaptive Immune Responses After Radiation Therapy.

PURPOSE: The role of MerTK, a member of the Tyro3-Axl-MerTK family of receptor tyrosine kinase, in the immune response to radiation therapy (RT) is unclear. We investigated immune-mediated tumor control after RT in murine models of colorectal and pancreatic adenocarcinoma using MerTK wild-type and knock-out hosts and whether inhibition of MerTK signaling with warfarin could replicate MerTK knock-out phenotypes. METHODS AND MATERIALS: Wild-type and MerTK-/- BALB/c mice were grafted in the flanks with CT26 tumors and treated with computed tomography guided RT. The role of macrophages and CD8 T cells in the response to radiation were demonstrated with cell depletion studies. The role of MerTK in priming immune responses after RT alone and with agonist antibodies to the T cell costimulatory molecule OX40 was evaluated in a Panc02-SIY model antigen system. The effect of warfarin therapy on the in-field and abscopal response to RT was demonstrated in murine models of colorectal adenocarcinoma. The association between warfarin and progression-free survival for patients treated with SABR for early-stage non-small cell lung cancer was evaluated in a multi-institutional retrospective study. RESULTS: MerTK-/- hosts had better tumor control after RT compared with wild-type mice in a macrophage and CD8 T cell-dependent manner. MerTK-/- mice showed increased counts of tumor antigen-specific CD8 T cells in the peripheral blood after tumor-directed RT alone and in combination with agonist anti-OX40. Warfarin therapy phenocopied MerTK-/- for single-flank tumors treated with RT and improved abscopal responses for RT combined with anti-CTLA4. Patients on warfarin therapy when treated with SABR for non-small cell lung cancer had higher progression-free survival rates compared with non-warfarin users. CONCLUSIONS: MerTK inhibits adaptive immune responses after SABR. Because warfarin inhibits MerTK signaling and phenocopies genetic deletion of MerTK in mice, warfarin therapy may have beneficial effects in combination with SABR and immune therapy in patients with cancer.

TGFß suppresses CD8+ T cell expression of CXCR3 and tumor trafficking.

Transforming growth factor beta (TGFß) is a multipotent immunosuppressive cytokine. TGFß excludes immune cells from tumors, and TGFß inhibition improves the efficacy of cytotoxic and immune therapies. Using preclinical colorectal cancer models in cell type-conditional TGFß receptor I (ALK5) knockout mice, we interrogate this mechanism. Tumor growth delay and radiation response are unchanged in animals with Treg or macrophage-specific ALK5 deletion. However, CD8αCre-ALK5flox/flox (ALK5ΔCD8) mice reject tumors in high proportions, dependent on CD8+ T cells. ALK5ΔCD8 mice have more tumor-infiltrating effector CD8+ T cells, with more cytotoxic capacity. ALK5-deficient CD8+ T cells exhibit increased CXCR3 expression and enhanced migration towards CXCL10. TGFß reduces CXCR3 expression, and increases binding of Smad2 to the CXCR3 promoter. In vivo CXCR3 blockade partially abrogates the survival advantage of an ALK5ΔCD8 host. These data demonstrate a mechanism of TGFß immunosuppression through inhibition of CXCR3 in CD8+ T cells, thereby limiting their trafficking into tumors.