Leukocyte Function-associated Antigen-1 Research Articles

Abstract 3592: Pharmacological intervention to temporally stimulate or inhibit ICAM-1 targeting CAR-T cells

Abstract Gene-engineered adoptive T cell therapies have recently been approved by the FDA. We have previously published data utilizing this technology to target intercellular adhesion molecule-1 (ICAM-1), a broad tumor biomarker. Using an affinity modified version of the physiological ligand of ICAM-1,leukocyte function-associated antigen-1 (LFA-1) I-domain, we have shown efficient clearance of a human metastatic anaplastic thyroid cancer (ATC). We were able to visualize and quantify the bio-distribution of CAR-T cells with a PET gene reporter, somatostatin receptor 2 (SSTR2) (Park et. al, Scientific Reports 7, Article number: 14366, 2017). To expand on this platform, we now want to control the activity of our CAR-T cells by exploiting these features using two FDA approved drugs. First, a somatostain analogue, Lanreotide, has been approved for treating Acromegaly and we have recently observed that Lanreotide can activate SSTR2-transduced T cells via calcium release. Second, Lovastatin, a drug clinically used for lowering cholesterol levels, was found to bind the LFA-1 I-domain and inhibit LFA-1 binding to ICAM-1. We hypothesized that in addition to our I-domain CAR-T cell, systemic use of Lanreotide will stimulate CAR-mediated tumor killing while systemic use of Lovastatin will inhibit CAR-mediated tumor killing. In-vitro testing involved effector to target (E:T) assays performed in the presence and absence of Lovastatin or Lanreotide. ICAM-1(+) ATC target cells or ICAM-1(-) 293T off-target cells were utilized, both of which were transduced with GFP-Firefly Luciferase (GFP/Fluc) for quantification. Effector T-cells derived from healthy donor PBMCs were either transduced with our I-domain CAR-T cell construct that contains SSTR2, or were left nontransduced. Similar assays were translated in-vivo using a previously established solid tumor model with GFP/Fluc ATC ICAM-1(+) cells. Luminescence was used to track tumor progression and regression throughout both in-vivo and in-vitro experiments. [Ga68] DOTA-TOC was administered via IV injections to visualize the bio-distribution of the CAR-T cells using SSTR2 via PET/CT. Both in-vitro and in-vivo experiments showed Lovastatins ability to compromise I-domain CAR-mediated tumor killing while Lanreotide expedited the rate of I-domain CAR-mediated killing. We report here that Lovastatin inhibits the interaction of our I-domain CAR with ICAM-1 that is present on our target tumor cells and compromises tumor killing. In addition, we have shown a unique phenomena where we can activate SSTR2-transduced CAR-T cells using Lanreotide. The ability to control CAR-T cell activity is an essential tool when addressing adverse effects and/or less than robust treatment outcomes. This will be crucial when translating our adoptive T cell therapy to the clinic. Citation Format: Yogindra Vedvyas, Jaclyn McCloskey, Yanping Yang, Irene M. Min, Moonsoo M. Jin. Pharmacological intervention to temporally stimulate or inhibit ICAM-1 targeting CAR-T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3592.

F-Actin-Driven CD28-CD80 Localization in the Immune Synapse

During immunological synapse (IS) formation, Tcell receptor (TCR) signaling complexes, integrins, and costimulatory molecules exhibit a particular spatial localization. Here, we develop an agent-based model for the IS formation based on TCR peptide-bound major histocompatibility complex (pMHC) and leukocyte-function-associated antigen 1 (LFA-1) intracellular activation molecule 1 (ICAM-1) dynamics, including CD28 binding to a costimulatory ligand, coupling of molecules to the centripetal actin flow, and size-based segregation (SBS). A radial gradient of LFA-1 in the peripheral supramolecular activation cluster (pSMAC) toward the central supramolecular activation cluster (cSMAC) emerged as a combined consequence of actin binding and diffusion and modified the positioning of other molecules. The simulations predict a mechanism of CD28 movement, according to which CD28-CD80 complexes passively follow TCR-pMHC microclusters. However, the characteristic CD28-CD80 localization in a ring pattern around the cSMAC only emerges with a particular CD28-actin coupling strength that induces a centripetal motion. These results have implications for the understanding of Tcell activation and fate decisions.

Transgelin-2 in immunity: Its implication in cell therapy

Transgelin-2 is a small 22-kDa actin-binding protein implicated in actin dynamics, which stabilizes actin structures and participates in actin-associated signaling pathways. Much curiosity regarding transgelin-2 has centered around its dysregulation in tumor development and associated diseases. However, recent studies have shed new light on the functions of transgelin-2, the only transgelin family member present in leukocytes, in the context of various immune responses. In this review, we outlined the biochemical properties of transgelin-2 and its physiological functions in T cells, B cells, and macrophages. Transgelin-2 regulates T cell activation by stabilizing the actin cytoskeleton at the immunological synapse. Transgelin-2 in B cells also participates in the stabilization of T cell-B cell conjugates. While transgelin-2 is expressed at trace levels in macrophages, its expression is highly upregulated upon lipopolysaccharide stimulation and plays an essential role in macrophage phagocytosis. Since transgelin-2 increases T cell adhesion to target cells via boosting the "inside-out" costimulatory activation of leukocyte function-associated antigen 1, transgelin-2 could be a suitable candidate to potentiate the antitumor response of cytotoxic T cells by compensating for the lack of costimulation in tumor microenvironment. We discussed the feasibility of using native or engineered transgelin-2 as a synergistic molecule in cell-based immunotherapies, without inducing off-target disturbance in actin dynamics in other cells.

Calcineurin positively regulates TCR-induced LFA-1-dependent cell adhesion via dephosphorylation of Lck Ser-59.

Abstract T cell adhesion via the interaction of the integrin leukocyte function-associated antigen-1 (LFA-1) with its ligand ICAM-1 is essential for the initiation of immune response. Upon ligation of T cell receptor (TCR), activation-induced LFA-1 conformational change occurs via phosphorylation of Thr-758 resulting in the enhancement of binding to ICAM-1. Recently, we reported that dephosphorylation of Lck Ser-59 (LckS59) by calcineurin results in enhanced TCR-proximal signaling, indicating that phosphorylated LckS59 negatively regulates T cell activation. Here we find that inhibition of calcineurin activity by immunosuppressive drugs such as cyclosporin A (CsA) rapidly reverses existing TCR-induced LFA-1-dependent cell adhesion as well as the phosphorylation of LFA-1 Thr-758 in Jurkat and primary human T cells. In addition, TCR-induced cell adhesion of T cells from LckS59A knock-in mice was stronger than T cells from LckWT mice. Consistent with enhanced cell adhesion, some of the signaling events downstream of TCR proximal signaling were also enhanced in LckS59A mouse T cells. Notably, LckS59A T cell adhesion was resistant to CsA inhibition. These observations provide new insights into a previously unrecognized role for calcineurin inhibitors in reversing ligand-dependent adhesion independently of its effects on NFAT activation.

Ligand- and cation-induced structural alterations of the leukocyte integrin LFA-1

In αI integrins, including leukocyte function-associated antigen 1 (LFA-1), ligand-binding function is delegated to the αI domain, requiring extra steps in the relay of signals that activate ligand binding and coordinate it with cytoplasmic signals. Crystal structures reveal great variation in orientation between the αI domain and the remainder of the integrin head. Here, we investigated the mechanisms involved in signal relay to the αI domain, including whether binding of the ligand intercellular adhesion molecule-1 (ICAM-1) to the αI domain is linked to headpiece opening and engenders a preferred αI domain orientation. Using small-angle X-ray scattering and negative-stain EM, we define structures of ICAM-1, LFA-1, and their complex, and the effect of activation by Mn2+ Headpiece opening was substantially stabilized by substitution of Mg2+ with Mn2+ and became complete upon ICAM-1 addition. These agents stabilized αI-headpiece orientation, resulting in a well-defined orientation of ICAM-1 such that its tandem Ig-like domains pointed in the opposite direction from the β-subunit leg of LFA-1. Mutations in the integrin βI domain α1/α1' helix stabilizing either the open or the closed βI-domain conformation indicated that α1/α1' helix movements are linked to ICAM-1 binding by the αI domain and to the extended-open conformation of the ectodomain. The LFA-1-ICAM-1 orientation described here with ICAM-1 pointing anti-parallel to the LFA-1 β-subunit leg is the same orientation that would be stabilized by tensile force transmitted between the ligand and the actin cytoskeleton and is consistent with the cytoskeletal force model of integrin activation.

Forced-rupture of cell-adhesion complexes reveals abrupt switch between two brittle states.

Cell adhesion complexes (CACs), which are activated by ligand binding, play key roles in many cellular functions ranging from cell cycle regulation to mediation of cell extracellular matrix adhesion. Inspired by single molecule pulling experiments using atomic force spectroscopy on leukocyte function-associated antigen-1 (LFA-1), expressed in T-cells, bound to intercellular adhesion molecules (ICAM), we performed constant loading rate (rf) and constant force (F) simulations using the self-organized polymer model to describe the mechanism of ligand rupture from CACs. The simulations reproduce the major experimental finding on the kinetics of the rupture process, namely, the dependence of the most probable rupture forces (f*s) on ln rf (rf is the loading rate) exhibits two distinct linear regimes. The first, at low rf, has a shallow slope, whereas the slope at high rf is much larger, especially for a LFA-1/ICAM-1 complex with the transition between the two occurring over a narrow rf range. Locations of the two transition states (TSs) extracted from the simulations show an abrupt change from a high value at low rf or constant force, F, to a low value at high rf or F. This unusual behavior in which the CACs switch from one brittle (TS position is a constant over a range of forces) state to another brittle state is not found in forced-rupture in other protein complexes. We explain this novel behavior by constructing the free energy profiles, F(Λ)s, as a function of a collective reaction coordinate (Λ), involving many key charged residues and a critical metal ion (Mg2+). The TS positions in F(Λ), which quantitatively agree with the parameters extracted using the Bell-Evans model, change abruptly at a critical force, demonstrating that it, rather than the molecular extension, is a good reaction coordinate. Our combined analyses using simulations performed in both the pulling modes (constant rf and F) reveal a new mechanism for the two loading regimes observed in the rupture kinetics in CACs.

Volatile Anesthetic Isoflurane Attenuates Liver Injury in Experimental Polymicrobial Sepsis Model.

Volatile anesthetics are often administered to patients with sepsis for procedural anesthesia or sedation in intensive care units. Sepsis still carries significant morbidities and mortalities, and organ injuries pose major complications. Early liver dysfunction is associated with poor outcome mainly as a result of overwhelming neutrophil recruitment. Leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) are major adhesion molecules on neutrophils and involved in neutrophil recruitment. We have previously showed that volatile anesthetic isoflurane inhibited LFA-1 and Mac-1. Here we studied the role of isoflurane, LFA-1 and Mac-1 on neutrophil recruitment to the liver and liver injury using experimental polymicrobial abdominal sepsis induced by cecal ligation and puncture (CLP) surgery. We used wild type (WT), LFA-1, Mac-1 and intercellular adhesion molecule-1 (ICAM-1) knockout (KO) mice. Following the induction of sepsis by CLP surgery, a group of mice were exposed to isoflurane for 2 hours. We found that Mac-1 and ICAM-1, but not LFA-1 were involved in neutrophil recruitment to liver. Isoflurane attenuated neutrophil recruitment and liver injury in WT and LFA-1 KO mice. Mac-1 KO mice had limited neutrophil recruitment and liver injury, both of which were not attenuated by isoflurane further, suggesting that isoflurane mitigated liver injury via Mac-1. Mac-1 colocalized with ICAM-1 and fibrinogen on liver tissues. In the presence of fibrinogen Mac-1 bound ICAM-1 significantly more, while LFA-1 bound less to ICAM-1, suggesting that Mac-1 used fibrinogen as a bridging molecule to bind ICAM-1. In conclusion, isoflurane exposure attenuated neutrophil recruitment and liver injury via Mac-1.

A Functional Analysis on the Interspecies Interaction between Mouse LFA-1 and Human Intercellular Adhesion Molecule-1 at the Cell Level.

The interaction between intercellular adhesion molecules (ICAM) and the integrin leukocyte function-associated antigen-1 (LFA-1) is crucial for the regulation of several physiological and pathophysiological processes like cell-mediated elimination of tumor or virus infected cells, cancer metastasis, or inflammatory and autoimmune processes. Using purified proteins it was reported a species restriction for the interaction of ICAM-1 and LFA-1, being mouse ICAM-1 able to interact with human LFA-1 but not human ICAM-1 with mouse LFA-1. However, in vivo results employing tumor cells transfected with human ICAM-1 suggest that functionally mouse LFA-1 can recognize human ICAM-1. In order to clarify the interspecies cross-reactivity of the ICAM-1/LFA-1 interaction, we have performed functional studies analyzing the ability of human soluble ICAM-1 and human/mouse LFA-1 derived peptides to inhibit cell aggregation and adhesion as well as cell-mediated cytotoxicity in both mouse and human systems. In parallel, the affinity of the interaction between mouse LFA-1-derived peptides and human ICAM-1 was determined by calorimetry assays. According to the results obtained, it seems that human ICAM-1 is able to interact with mouse LFA-1 on intact cells, which should be taking into account when using humanized mice and xenograft models for the study of immune-related processes.

Dynamical Mechanisms of Allosteric Modulations by Small Molecules on Leukocyte Function-Associated Antigen-1

Dynamical Mechanisms of Allosteric Modulations by Small Molecules on Leukocyte Function-Associated Antigen-1

From the Cover: Prolonged Exposure to Volatile Anesthetic Isoflurane Worsens the Outcome of Polymicrobial Abdominal Sepsis.

Sepsis continues to result in high morbidity and mortality. General anesthesia is often administered to septic patients, but the impacts of general anesthesia on host defense are not well understood. General anesthesia can be given by volatile and intravenous anesthetics. Our previous in vitro study showed that volatile anesthetic isoflurane directly inhibits leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1), critical adhesion molecules on leukocytes. Thus, the role of isoflurane exposure on in vivo LFA-1 and Mac-1 function was examined using polymicrobial abdominal sepsis model in mice. As a comparison, intravenous anesthetic propofol was given to a group of mice. Wild type, LFA-1, Mac-1, and adhesion molecule-1 knockout mice were used. Following the induction of polymicrobial abdominal sepsis by cecal ligation and puncture, groups of mice were exposed to isoflurane for either 2 or 6 h, or to propofol for 6 h, and their outcomes were examined. Bacterial loads in tissues and blood, neutrophil recruitment to the peritoneal cavity and phagocytosis were studied. Six hours of isoflurane exposure worsened the outcome of abdominal sepsis (P < .0001) with higher bacterial loads in tissues, but 2 h of isoflurane or 6 h of propofol exposure did not. Isoflurane impaired neutrophil recruitment to the abdominal cavity by inhibiting LFA-1 function. Isoflurane also impaired bacterial phagocytosis via complement receptors including Mac-1. In conclusion, prolonged isoflurane exposure worsened the outcome of experimental polymicrobial abdominal sepsis and was associated with impaired neutrophil recruitment and bacterial phagocytosis via reduced LFA-1 and Mac-1 function.

The effect of different anesthetics on tumor cytotoxicity by natural killer cells

A number of retrospective studies have suggested that choice of anesthetic drugs during surgical tumor resection might affect tumor recurrence/metastasis, or outcome of patients. The recent study showed that volatile anesthetics-based general anesthesia was associated with the worse outcomes than intravenous anesthetics-based general anesthesia. However, the underlying mechanism is yet to be determined. Because natural killer (NK) cells are implicated as important immune cells for tumor recurrence/metastasis in the perioperative period, we examined the effect of different anesthetics on NK cell-mediated tumor cytotoxicity. Because adhesion molecule leukocyte function-associated antigen-1 (LFA-1) is functionally important in NK cells and is inhibited by commonly used volatile anesthetics isoflurane and sevoflurane, we hypothesized that these anesthetics would attenuate NK cell-mediated cytotoxicity. Using human NK cell line NK92-MI cells and tumor cell line K562 cells as a model system, we performed cytotoxicity, proliferation, conjugation and degranulation assays. Lytic granule polarization was also assessed. We showed that isoflurane, sevoflurane and LFA-1 inhibitor BIRT377 attenuated cytotoxicity, and reduced conjugation and polarization, but not degranulation of NK cells. Our data suggest that isoflurane and sevoflurane attenuated NK cell-mediated cytotoxicity at least partly by their LFA-1 inhibition in vitro. Whether or not isoflurane and sevoflurane attenuate NK cell-mediated tumor cytotoxicity in patients needs to be determined in the future.

Th17 Cells Induce Dopaminergic Neuronal Death via LFA-1/ICAM-1 Interaction in a Mouse Model of Parkinson's Disease.

T helper (Th)17 cells, a subset of CD4+ T lymphocytes, have strong pro-inflammatory property and appear to be essential in the pathogenesis of many inflammatory diseases. However, the involvement of Th17 cells in Parkinson's disease (PD) that is characterized by a progressive degeneration of dopaminergic (DAergic) neurons in the nigrostriatal system is unclear. Here, we aimed to demonstrate that Th17 cells infiltrate into the brain parenchyma and induce neuroinflammation and DAergic neuronal death in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- or 1-methyl-4-phenylpyridinium (MPP+)-induced PD models. Blood-brain barrier (BBB) disruption in the substantia nigra (SN) was assessed by the signal of FITC-labeled albumin that was injected into blood circulation via the ascending aorta. Live cell imaging system was used to observe a direct contact of Th17 cells with neurons by staining these cells using the two adhesion molecules, leukocyte function-associated antigen (LFA)-1 and intercellular adhesion molecule (ICAM)-1, respectively. Th17 cells invaded into the SN where BBB was disrupted in MPTP-induced PD mice. Th17 cells exacerbated DAergic neuronal loss and pro-inflammatory/neurotrophic factor disorders in MPP+-treated ventral mesencephalic (VM) cell cultures. A direct contact of LFA-1-stained Th17 cells with ICAM-1-stained VM neurons was dynamically captured. Either blocking LFA-1 in Th17 cells or blocking ICAM-1 in VM neurons with neutralizing antibodies abolished Th17-induced DAergic neuronal death. These results establish that Th17 cells infiltrate into the brain parenchyma of PD mice through lesioned BBB and exert neurotoxic property by promoting glial activation and importantly by a direct damage to neurons depending on LFA-1/ICAM-1 interaction.

The Integrin LFA-1 Controls T Follicular Helper Cell Generation and Maintenance

T follicular helper (Tfh) cells are a CD4+ Tcell subset critical for long-lived humoral immunity. We hypothesized that integrins play a decisive role in Tfh cell biology. Here we show that Tfh cells expressed a highly active form of leukocyte function-associated antigen-1 (LFA-1) that was required for their survival within the germinal center niche. In addition, LFA-1 promoted expression of Bcl-6, a transcriptional repressor critical for Tfh cell differentiation, and inhibition of LFA-1 abolished Tfh cell generation and prevented protective humoral immunity to intestinal helminth infection. Furthermore, we demonstrated that expression of Talin-1, an adaptor protein that regulates LFA-1 affinity, dictated Tfh versus Th2 effector cell differentiation. Collectively, our results define unique functions for LFA-1 in the Tfh cell effector program and suggest that integrin activity is important in lineage decision-making events in the adaptive immune system.

Downstream effect profiles discern different mechanisms of integrin αLβ2 inhibition

The integrin leucocyte function-associated antigen-1 (αLβ2, LFA-1) plays crucial roles in T cell adhesion, migration and immunological synapse (IS) formation. Consequently, αLβ2 is an important therapeutic target in autoimmunity. Three major classes of αLβ2 inhibitors with distinct modes of action have been described to date: Monoclonal antibodies (mAbs), small molecule α/β I allosteric and small molecule α I allosteric inhibitors. The objective of this study was to systematically compare these three modes of αLβ2 inhibition for their αLβ2 inhibitory as well as their potential agonist-like effects. All inhibitors assessed were found to potently block αLβ2-mediated leucocyte adhesion. None of the inhibitors induced ZAP70 phosphorylation, indicating absence of agonistic outside-in signalling. Paradoxically, however, the α/β I allosteric inhibitor XVA143 induced conformational changes within αLβ2 characteristic for an intermediate affinity state. This effect was not observed with the α I allosteric inhibitor LFA878 or the anti-αLβ2 mAb efalizumab. On the other hand, efalizumab triggered the unscheduled internalization of αLβ2 in CD4+ and CD8+ T cells while LFA878 and XVA143 did not affect or only mildly reduced αLβ2 surface expression, respectively. Moreover, efalizumab, in contrast to the small molecule inhibitors, disturbed the fine-tuned internalization/recycling of engaged TCR/CD3, concomitantly decreasing ZAP70 expression levels. In conclusion, different modes of αLβ2 inhibition are associated with fundamentally different biologic effect profiles. The differential established here is expected to provide important translational guidance as novel αLβ2 inhibitors will be advanced from bench to bedside.

LFA-1 integrin antibodies inhibit leukocyte α4β1–mediated adhesion by intracellular signaling

AbstractBinding of intercellular adhesion molecule-1 to the β2-integrin leukocyte function associated antigen-1 (LFA-1) is known to induce cross-talk to the α4β1 integrin. Using different LFA-1 monoclonal antibodies, we have been able to study the requirement and mechanism of action for the cross-talk in considerable detail. LFA-1-activating antibodies and those inhibitory antibodies that signal to α4β1 induce phosphorylation of Thr-758 on the β2-chain, which is followed by binding of 14-3-3 proteins and signaling through the G protein exchange factor Tiam1. This results in dephosphorylation of Thr-788/789 on the β1-chain of α4β1 and loss of binding to its ligand vascular cell adhesion molecule-1. The results show that with LFA-1 antibodies, we can activate LFA-1 and inhibit α4β1, inhibit both LFA-1 and α4β1, inhibit LFA-1 but not α4β1, or not affect LFA-1 or α4β1. These findings are important for the understanding of integrin regulation and for the interpretation of the effect of integrin antibodies and their use in clinical applications.

The role of ICAM-1 isoforms in neutrophil recruitment to liver

Abstract Intercellular adhesion molecule-1 (ICAM-1) is one of important molecules involved in neutrophil recruitment and works as a ligand for integrin leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1) on neutrophils. Full-length ICAM-1 consists of five domains (D1–D2–D3–D4–D5) and D1 is a ligand binding domain for LFA-1 and D3 is for Mac-1. In addition, several alternative splicing variants exist as shown in transgenic mice. ICAM-1 Exon 4 deletion mice express D1D4D5, D1D2D5 and D1D5, while exon 5 deletion mice express D1D2D3D5, D1D2D5 and D1D5. The previous report of sepsis model showed exon 4 deletion mice showed significant reduction in neutrophil recruitment to liver with no mortality, while almost all of exon 5 deletion mice died with a large neutrophil recruitment. The mortality of WT mice was better than that of exon 5 deletion mice and worse than that of exon 4 deletion mice. These results suggest that ICAM-1 isoforms have functional roles in neutrophil recruitment. Our sepsis model demonstrated that neutrophil recruitment to liver was not affected in LFA-1 knockout mice and was reduced significantly in Mac-1 knockout mice. We speculated that ICAM-1 isoforms have functional roles via the interaction with Mac-1. Our PCR experiments demonstrated that liver highly expressed full length ICAM-1, D1D3D4D5 and D1D2D3D5 with full length ICAM-1 at the most abundant amount. Both D1D3D4D5 and D1D2D3D5 contain D3 and potentially bind to Mac-1. We expressed D1D3D4D5 and D1D2D3D5 along with full-length ICAM-1 in 293T cells, and examined the binding to Mac-1. Our preliminary data suggest that D1D2D3D5 bound more strongly to Mac-1 than full-length, supporting our hypothesis.

TGFβ Signaling Intersects with CD103 Integrin Signaling to Promote T-Lymphocyte Accumulation and Antitumor Activity in the Lung Tumor Microenvironment.

Homing of CD8(+) T lymphocytes to the tumor microenvironment is an important step for mounting a robust antitumor immune response. TGFβ is responsible for CD103 (αEβ7) integrin induction in activated intraepithelial CD8(+) T lymphocytes. However, the interplay between TGFβ and CD103 and their contribution to T-cell infiltration and antitumor activity remain unknown. Here, we used viable human lung tumor slices and autologous tumor antigen-specific T-lymphocyte clones to provide evidence that CD103 is directly involved in T-lymphocyte recruitment within epithelial tumor islets and intratumoral early T-cell signaling. Moreover, TGFβ enhanced CD103-dependent T-cell adhesion and signaling, whereas it inhibited leukocyte function-associated antigen (LFA)-1 (αLβ2) integrin expression and LFA-1-mediated T-lymphocyte functions. Mechanistic investigations revealed that TGFβ bound to its receptors (TGFBR), which promoted the recruitment and phosphorylation of integrin-linked kinase (ILK) by TGFBR1. We further show that ILK interacted with the CD103 intracellular domain, resulting in protein kinase B (PKB)/AKT activation, thereby initiating integrin inside-out signaling. Collectively, our findings suggest that the abundance of TGFβ in the tumor microenvironment may in fact engage with integrin signaling pathways to promote T-lymphocyte antitumor functions, with potential implications for T-cell-based immunotherapies for cancer. Cancer Res; 76(7); 1757-69. ©2016 AACR.

Anti-Leukocyte Function-Associated Antigen 1 Therapy in a Nonhuman Primate Renal Transplant Model of Costimulation Blockade-Resistant Rejection.

Costimulation blockade with the fusion protein belatacept provides a desirable side effect profile and improvement in renal function compared with calcineurin inhibition in renal transplantation. This comes at the cost of increased rates of early acute rejection. Blockade of the integrin molecule leukocyte function-associated antigen 1 (LFA-1) has been shown to be an effective adjuvant to costimulation blockade in a rigorous nonhuman primate (NHP) model of islet transplantation; therefore, we sought to test this combination in an NHP renal transplant model. Rhesus macaques received belatacept maintenance therapy with or without the addition of LFA-1 blockade, which was achieved using a murine-derived LFA-1-specific antibody TS1/22. Additional experiments were performed using chimeric rhesus IgG1 (TS1/22R1) or IgG4 (TS1/22R4) variants, each engineered to limit antibody clearance. Despite evidence of proper binding to the target molecule and impaired cellular egress from the intravascular space indicative of a therapeutic effect similar to prior islet studies, LFA-1 blockade failed to significantly prolong graft survival. Furthermore, evidence of impaired protective immunity against cytomegalovirus was observed. These data highlight the difficulties in translating treatment regimens between organ models and suggest that the primarily vascularized renal model is more robust with regard to belatacept-resistant rejection than the islet model.

Dual functions of Rap1 are crucial for T-cell homeostasis and prevention of spontaneous colitis.

Rap1-GTP activates leukocyte function-associated antigen-1 (LFA-1) to induce arrest on the high endothelial venule (HEV). Here we show that Rap1-GDP restrains rolling behaviours of T cells on the peripheral lymph node addressin (PNAd), P-selectin and mucosal addressin cell adhesion molecule-1 (MadCAM-1) by inhibiting tether formation. Consequently, Rap1 deficiency impairs homing of naive T cells to peripheral lymph nodes, but accelerates homing of TH17 and TH1 cells to the colon, resulting in spontaneous colitis with tumours. Rap1-GDP associates with and activates lymphocyte-oriented kinase, which phosphorylates ERM (ezrin, radixin and moesin) in resting T cells. Phosphomimetic ezrin reduces the rolling of Rap1-deficient cells, and thereby decreases their homing into the colon. On the other hand, chemokines activate Rap1 at the plasma membrane within seconds, and Rap1-GTP binds to filamins, which diminishes its association with the β2 chain of LFA-1 and results in LFA-1 activation. This Rap1-dependent regulation of T-cell circulation prevents the onset of colitis.

Impact of Leukocyte Function-Associated Antigen-1 Blockade on Endogenous Allospecific T Cells to Multiple Minor Histocompatibility Antigen Mismatched Cardiac Allograft.

Blocking leukocyte function-associated antigen (LFA)-1 in organ transplant recipients prolongs allograft survival. However, the precise mechanisms underlying the therapeutic potential of LFA-1 blockade in preventing chronic rejection are not fully elucidated. Cardiac allograft vasculopathy (CAV) is the preeminent cause of late cardiac allograft failure characterized histologically by concentric intimal hyperplasia. Anti-LFA-1 monoclonal antibody was used in a multiple minor antigen-mismatched, BALB.B (H-2B) to C57BL/6 (H-2B), cardiac allograft model. Endogenous donor-specific CD8 T cells were tracked down using major histocompatibility complex multimers against the immunodominant H4, H7, H13, H28, and H60 minor Ags. The LFA-1 blockade prevented acute rejection and preserved palpable beating quality with reduced CD8 T-cell graft infiltration. Interestingly, less CD8 T cell infiltration was secondary to reduction of T-cell expansion rather than less trafficking. The LFA-1 blockade significantly suppressed the clonal expansion of minor histocompatibility antigen-specific CD8 T cells during the expansion and contraction phase. The CAV development was evaluated with morphometric analysis at postoperation day 100. The LFA-1 blockade profoundly attenuated neointimal hyperplasia (61.6 vs 23.8%; P < 0.05), CAV-affected vessel number (55.3 vs 15.9%; P < 0.05), and myocardial fibrosis (grade 3.29 vs 1.8; P < 0.05). Finally, short-term LFA-1 blockade promoted long-term donor-specific regulation, which resulted in attenuated transplant arteriosclerosis. Taken together, LFA-1 blockade inhibits initial endogenous alloreactive T-cell expansion and induces more regulation. Such a mechanism supports a pulse tolerance induction strategy with anti-LFA-1 rather than long-term treatment.