Impact of isotype on the mechanism of action of agonist anti-OX40 antibodies in cancer: implications for therapeutic combinations.

BACKGROUND: OX40 has been widely studied as a target for immunotherapy with agonist antibodies taken forward into clinical trials for cancer where they are yet to show substantial efficacy. Here, we investigated potential mechanisms of action of anti-mouse (m) OX40 and anti-human (h) OX40 antibodies, including a clinically relevant monoclonal antibody (mAb) (GSK3174998) and evaluated how isotype can alter those mechanisms with the aim to develop improved antibodies for use in rational combination treatments for cancer. METHODS: Anti-mOX40 and anti-hOX40 mAbs were evaluated in a number of in vivo models, including an OT-I adoptive transfer immunization model in hOX40 knock-in (KI) mice and syngeneic tumor models. The impact of FcγR engagement was evaluated in hOX40 KI mice deficient for Fc gamma receptors (FcγR). Additionally, combination studies using anti-mouse programmed cell death protein-1 (mPD-1) were assessed. In vitro experiments using peripheral blood mononuclear cells (PBMCs) examining possible anti-hOX40 mAb mechanisms of action were also performed. RESULTS: Isotype variants of the clinically relevant mAb GSK3174998 showed immunomodulatory effects that differed in mechanism; mIgG1 mediated direct T-cell agonism while mIgG2a acted indirectly, likely through depletion of regulatory T cells (Tregs) via activating FcγRs. In both the OT-I and EG.7-OVA models, hIgG1 was the most effective human isotype, capable of acting both directly and through Treg depletion. The anti-hOX40 hIgG1 synergized with anti-mPD-1 to improve therapeutic outcomes in the EG.7-OVA model. Finally, in vitro assays with human peripheral blood mononuclear cells (hPBMCs), anti-hOX40 hIgG1 also showed the potential for T-cell stimulation and Treg depletion. CONCLUSIONS: These findings underline the importance of understanding the role of isotype in the mechanism of action of therapeutic mAbs. As an hIgG1, the anti-hOX40 mAb can elicit multiple mechanisms of action that could aid or hinder therapeutic outcomes, dependent on the microenvironment. This should be considered when designing potential combinatorial partners and their FcγR requirements to achieve maximal benefit and improvement of patient outcomes.

Activating Inducible T-cell Costimulator Yields Antitumor Activity Alone and in Combination with Anti-PD-1 Checkpoint Blockade.

In recent years, there has been considerable interest in mAb-based induction of costimulatory receptor signaling as an approach to combat cancer. However, promising nonclinical data have yet to translate to a meaningful clinical benefit. Inducible T-cell costimulator (ICOS) is a costimulatory receptor important for immune responses. Using a novel clinical-stage anti-ICOS immunoglobulin G4 mAb (feladilimab), which induces but does not deplete ICOS+ T cells and their rodent analogs, we provide an end-to-end evaluation of the antitumor potential of antibody-mediated ICOS costimulation alone and in combination with programmed cell death protein 1 (PD-1) blockade. We demonstrate, consistently, that ICOS is expressed in a range of cancers, and its induction can stimulate growth of antitumor reactive T cells. Furthermore, feladilimab, alone and with a PD-1 inhibitor, induced antitumor activity in mouse and humanized tumor models. In addition to nonclinical evaluation, we present three patient case studies from a first-time-in-human, phase I, open-label, dose-escalation and dose-expansion clinical trial (INDUCE-1; ClinicalTrials.gov: NCT02723955), evaluating feladilimab alone and in combination with pembrolizumab in patients with advanced solid tumors. Preliminary data showing clinical benefit in patients with cancer treated with feladilimab alone or in combination with pembrolizumab was reported previously; with example cases described here. Additional work is needed to further validate the translation to the clinic, which includes identifying select patient populations that will benefit from this therapeutic approach, and randomized data with survival endpoints to illustrate its potential, similar to that shown with CTLA-4 and PD-1 blocking antibodies. Significance: Stimulation of the T-cell activation marker ICOS with the anti-ICOS agonist mAb feladilimab, alone and in combination with PD-1 inhibition, induces antitumor activity across nonclinical models as well as select patients with advanced solid tumors.

Immuno-PET Monitoring of CD8+ T Cell Infiltration Post ICOS Agonist Antibody Treatment Alone and in Combination with PD-1 Blocking Antibody Using a 89Zr Anti-CD8+ Mouse Minibody in EMT6 Syngeneic Tumor Mouse.

PURPOSE: The presence and functional competence of intratumoral CD8+ T cells is often a barometer for successful immunotherapeutic responses in cancer. Despite this understanding and the extensive number of clinical-stage immunotherapies focused on potentiation (co-stimulation) or rescue (checkpoint blockade) of CD8+ T cell antitumor activity, dynamic biomarker strategies are often lacking. To help fill this gap, immuno-PET nuclear imaging has emerged as a powerful tool for in vivo molecular imaging of antibody targeting. Here, we took advantage of immuno-PET imaging using 89Zr-IAB42M1-14, anti-mouse CD8 minibody, to characterize CD8+ T-cell tumor infiltration dynamics following ICOS (inducible T-cell co-stimulator) agonist antibody treatment alone and in combination with PD-1 blocking antibody in a model of mammary carcinoma. PROCEDURES: Female BALB/c mice with established EMT6 tumors received 10 µg, IP of either IgG control antibodies, ICOS agonist monotherapy, or ICOS/PD-1 combination therapy on days 0, 3, 5, 7, 9, 10, or 14. Imaging was performed at 24 and 48 h post IV dose of 89Zr IAB42M1-14. In addition to 89Zr-IAB42M1-14 uptake in tumor and tumor-draining lymph node (TDLN), 3D radiomic features were extracted from PET/CT images to identify treatment effects. Imaging mass cytometry (IMC) and immunohistochemistry (IHC) was performed at end of study. RESULTS: 89Zr-IAB42M1-14 uptake in the tumor was observed by day 11 and was preceded by an increase in the TDLN as early as day 4. The spatial distribution of 89Zr-IAB42M1-14 was more uniform in the drug treated vs. control tumors, which had spatially distinct tracer uptake in the periphery relative to the core of the tumor. IMC analysis showed an increased percentage of cytotoxic T cells in the ICOS monotherapy and ICOS/PD-1 combination group compared to IgG controls. Additionally, temporal radiomics analysis demonstrated early predictiveness of imaging features. CONCLUSION: To our knowledge, this is the first detailed description of the use of a novel immune-PET imaging technique to assess the kinetics of CD8+ T-cell infiltration into tumor and lymphoid tissues following ICOS agonist and PD-1 blocking antibody therapy. By demonstrating the capacity for increased spatial and temporal resolution of CD8+ T-cell infiltration across tumors and lymphoid tissues, these observations underscore the widespread potential clinical utility of non-invasive PET imaging for T-cell-based immunotherapy in cancer.

Engineering Cancer Antigen-Specific T Cells to Overcome the Immunosuppressive Effects of TGF-ß.

Adoptive T cell therapy with T cells expressing affinity-enhanced TCRs has shown promising results in phase 1/2 clinical trials for solid and hematological tumors. However, depth and durability of responses to adoptive T cell therapy can suffer from an inhibitory tumor microenvironment. A common immune-suppressive agent is TGF-ß, which is secreted by tumor cells and cells recruited to the tumor. We investigated whether human T cells could be engineered to be resistant to inhibition by TGF-ß. Truncating the intracellular signaling domain from TGF-ß receptor (TGFßR) II produces a dominant-negative receptor (dnTGFßRII) that dimerizes with endogenous TGFßRI to form a receptor that can bind TGF-ß but cannot signal. We previously generated specific peptide enhanced affinity receptor TCRs recognizing the HLA-A*02-restricted peptides New York esophageal squamous cell carcinoma 1 (NY-ESO-1)157-165/l-Ag family member-1A (TCR: GSK3377794, formerly NY-ESO-1c259) and melanoma Ag gene A10254-262 (TCR: ADP-A2M10, formerly melanoma Ag gene A10c796). In this article, we show that exogenous TGF-ß inhibited in vitro proliferation and effector functions of human T cells expressing these first-generation high-affinity TCRs, whereas inhibition was reduced or abolished in the case of second-generation TCRs coexpressed with dnTGFßRII (e.g., GSK3845097). TGF-ß isoforms and a panel of TGF-ß-associated genes are overexpressed in a range of cancer indications in which NY-ESO-1 is commonly expressed, particularly in synovial sarcoma. As an example, immunohistochemistry/RNAscope identified TGF-ß-positive cells close to T cells in tumor nests and stroma, which had low frequencies of cells expressing IFN-γ in a non-small cell lung cancer setting. Coexpression of dnTGFßRII may therefore improve the efficacy of TCR-transduced T cells.

Characterization of the robust humoral immune response to GSK2618960, a humanized anti-IL-7 receptor monoclonal antibody, observed in healthy subjects in a Phase 1 study.

Interleukin-7 (IL-7) signaling modulates T cell activity and is implicated in numerous autoimmune diseases. An anti-IL-7 receptor monoclonal antibody (GSK2618960) biotherapeutic was evaluated in healthy subjects for safety, pharmacokinetics (PK), pharmacodynamics (PD) and immunogenicity in a single-dose escalation phase I study. We found that antibodies against GSK2618960 (i.e., anti-drug antibodies or ADA) developed in 83% and 100% of GSK2618960-treated subjects in the 0.6 and 2.0 mg/kg dose cohorts, respectively. Of the ADA positive subjects, 64% (7 of 11) had detectable neutralizing activity. Further investigation revealed the presence of GSK2618960-specific memory B cells, indicating the development of immunological memory for the ADAs. Ex vivo stimulation of peripheral blood mononuclear cell (PBMC) samples demonstrated a relatively strong CD4+ T cell proliferation response to GSK2618960 as compared to the control anti-RSV antibody (which is known to have only low immunogenic potential), confirming the high immunogenic potential of GSK2618960. Furthermore, GSK2618960 was found to bind in vitro monocyte-derived dendritic cells (DCs). GSK2618960 treatment of PBMCs increased the proportion of DC cells showing an increase in expression of CD83, CD86 and CD209, which indicated enhanced DC differentiation and activation relative to the isotype control anti-ß amyloid antibody. Collectively, the evidence supports that the high incidence of observed clinical immunogenicity was likely related to the receptor-mediated activity by GSK2618960.

Depletion of LAG-3+ T Cells Translated to Pharmacology and Improvement in Psoriasis Disease Activity: A Phase I Randomized Study of mAb GSK2831781.

Activated T cells drive a range of immune-mediated inflammatory diseases. LAG-3 is transiently expressed on recently activated CD4+ and CD8+ T cells. We describe the engineering and first-in-human clinical study (NCT02195349) of GSK2831781 (an afucosylated humanized IgG1 monoclonal antibody enhanced with high affinity for Fc receptors and LAG-3 and antibody-dependent cellular cytotoxicity capabilities), which depletes LAG-3 expressing cells. GSK2831781 was tested in a phase I/Ib, double-blind, placebo-controlled clinical study, which randomized 40 healthy participants (part A) and 27 patients with psoriasis (part B) to single doses of GSK2831781 (up to 0.15 and 5 mg/kg, respectively) or placebo. Adverse events were generally balanced across groups, with no safety or tolerability concern identified. LAG-3+ cell depletion in peripheral blood was observed at doses ≥ 0.15 mg/kg and was dose-dependent. In biopsies of psoriasis plaques, a reduction in mean group LAG-3+ and CD3+ T-cell counts was observed following treatment. Downregulation of proinflammatory genes (IL-17A, IL-17F, IFNγ, and S100A12) and upregulation of the epithelial barrier integrity gene, CDHR1, was observed with the 5 mg/kg dose of GSK2831781. Psoriasis disease activity improved up to day 43 at all GSK2831781 doses (0.5, 1.5, and 5 mg/kg) compared with placebo. Depletion of LAG-3-expressing activated T cells is a novel approach, and this first clinical study shows that GSK2831781 is pharmacologically active and provides encouraging early evidence of clinical effects in psoriasis, which warrants further investigation in T-cell-mediated inflammatory diseases.

High OX-40 expression in the tumor immune infiltrate is a favorable prognostic factor of overall survival in non-small cell lung cancer.

INTRODUCTION: OX-40 co-stimulatory signaling plays a role in mounting anti-tumor immune responses and clinical trials targeting this pathway are ongoing. However, the association of with OX-40 protein expression with clinical outcomes and pathological features in non-small cell lung cancer (NSCLC) are largely unknown. METHODS: Surgically-resected stage I-III NSCLC specimens (N = 100) were stained by immunohistochemistry (IHC) for the following immune markers: OX-40, PD-L1, PD-1, CD3, CD4, CD8, CD45RO, CD57, CD68, FOXP3, granzyme B, and ICOS. Immune-related markers mRNA expression were also assessed. We evaluated the association of OX-40 levels with major clinicopathologic variables, including molecular driver mutations. RESULTS: OX-40 IHC expression was observed in all tested tumors, predominantly localized in the membrane of the tumor immune infiltrate, and was not associated with a specific clinicopathologic or molecular subtype. High OX-40 expression levels measured by IHC median score were associated with better overall survival (OS) (p = 0.002), independent of CD3/CD8, PD-L1, and ICOS expression. High OX-40 IHC score was associated with increased expression of immune-related genes such as CD3, IFN-gamma, ICOS, CD8, CXCL9, CXCL10, CCL5, granzyme K. CONCLUSIONS: High OX-40 IHC expression in the tumor immune infiltrate is associated with favorable prognosis and increased levels of immune-related genes including IFN-gamma in patients with surgically resected stage I-III NSCLC. Its prognostic utility is independent of PD-L1 and other common markers of immune activation. High OX-40 expression potentially identifies a unique subgroup of NSCLC that may benefit from co-stimulation with OX-40 agonist antibodies and potentially enhance the efficacy of existing immune checkpoint therapies.

Anti-IL-7 receptor α monoclonal antibody (GSK2618960) in healthy subjects - a randomized, double-blind, placebo-controlled study.

AIM: Interleukin (IL)-7 signalling modulates T cell activity and is implicated in numerous autoimmune diseases. The present study investigated the safety, pharmacokinetics, target engagement, pharmacodynamics and immunogenicity of GSK2618960, an IL-7 receptor-α subunit (CD127) monoclonal antibody. METHODS: A double-blind (sponsor-unblind) study of a single intravenous infusion of either GSK2618960 (0.6 mg kg-1 or 2.0 mg kg-1 ) or placebo was carried out in 18 healthy subjects over 24 weeks. RESULTS: GSK2618960 was well tolerated; there were no serious or significant adverse events. The observed half-life was 5 (±1) days (2.0 mg kg-1 ), with nonlinear pharmacokinetics. Full receptor occupancy (>95%) was observed until day 8 (0.6 mg kg-1 ) and day 22 (2.0 mg kg-1 ). Maximal inhibition of IL-7-mediated signal transducer and activator of transcription 5 (STAT5) phosphorylation was observed in 5/6 subjects until day 22 (2.0 mg kg-1 ). Mean circulating IL-7 and soluble receptor (CD127) levels were increased above baseline during days 2 and 15 (0.6 mg kg-1 ) and days 2 and 22 (2.0 mg kg-1 ). No meaningful changes were observed in absolute numbers or proportions of immune cell populations or inflammatory cytokine profiles (IL-6, tumour necrosis factor-α, interferon-γ, IL-2). Persistent antidrug antibodies (ADAs) were detected in 5/6 subjects administered a dose of 0.6 mg kg-1 (neutralizing in 2/6) and in 6/6 subjects administered 2.0 mg kg-1 (neutralizing in 5/6). CONCLUSION: GSK2618960 was well tolerated and blocked IL-7 receptor signalling upon full target engagement. Although there was no discernible impact on peripheral T cell subsets in healthy subjects, GSK2618960 may effectively modulate the autoinflammatory activity of pathogenic T cells in diseased tissue. A relatively short half-life is likely the result of target-mediated rather than ADA-mediated clearance.

Tumor-immune profiling of murine syngeneic tumor models as a framework to guide mechanistic studies and predict therapy response in distinct tumor microenvironments.

Mouse syngeneic tumor models are widely used tools to demonstrate activity of novel anti-cancer immunotherapies. Despite their widespread use, a comprehensive view of their tumor-immune compositions and their relevance to human tumors has only begun to emerge. We propose each model possesses a unique tumor-immune infiltrate profile that can be probed with immunotherapies to inform on anti-tumor mechanisms and treatment strategies in human tumors with similar profiles. In support of this endeavor, we characterized the tumor microenvironment of four commonly used models and demonstrate they encompass a range of immunogenicities, from highly immune infiltrated RENCA tumors to poorly infiltrated B16F10 tumors. Tumor cell lines for each model exhibit different intrinsic factors in vitro that likely influence immune infiltration upon subcutaneous implantation. Similarly, solid tumors in vivo for each model are unique, each enriched in distinct features ranging from pathogen response elements to antigen presentation machinery. As RENCA tumors progress in size, all major T cell populations diminish while myeloid-derived suppressor cells become more enriched, possibly driving immune suppression and tumor progression. In CT26 tumors, CD8 T cells paradoxically increase in density yet are restrained as tumor volume increases. Finally, immunotherapy treatment across these different tumor-immune landscapes segregate into responders and non-responders based on features partially dependent on pre-existing immune infiltrates. Overall, these studies provide an important resource to enhance our translation of syngeneic models to human tumors. Future mechanistic studies paired with this resource will help identify responsive patient populations and improve strategies where immunotherapies are predicted to be ineffective.

CCL20 neutralization by a monoclonal antibody in healthy subjects selectively inhibits recruitment of CCR6+ cells in an experimental suction blister.

AIMS: GSK3050002, a humanized IgG1κ antibody with high binding affinity to human CCL20, was administered in a first-in-human study to evaluate safety, pharmacokinetics (PK) and pharmacodynamics (PD). An experimental skin suction blister model was employed to assess target engagement and the ability of the compound to inhibit recruitment of inflammatory CCR6 expressing cells. METHODS: This study was a randomized, double-blind (sponsor open), placebo-controlled, single-centre, single ascending intravenous dose escalation trial in 48 healthy male volunteers. RESULTS: GSK3050002 (0.1-20 mg kg-1 ) was well tolerated and no safety concerns were identified. The PK was linear over the dose range, with a half-life of approximately 2 weeks. Complex of GSK3050002/CCL20 increased in serum and blister fluid with increasing doses of GSK3050002. There were dose-dependent decreases in CCR6+ cell recruitment to skin blisters with maximal effects at doses of 5 mg kg-1 and higher, doses at which GSK3050002/CCL20 complex in serum and blister fluid also appeared to reach maximum levels. CONCLUSIONS: These results indicate a relationship between PK, target engagement and PD, suggesting a selective inhibition of recruitment of CCR6+ cells by GSK3050002 and support further development of GSK3050002 in autoimmune and inflammatory diseases.

Characterisation of the clinical and activated T cell response to repeat delayed-type hypersensitivity skin challenges in human subjects, with KLH and PPD, as a potential model to test T cell-targeted therapies.

OBJECTIVE: To characterise the delayed-type hypersensitivity (DTH) skin reaction to repeated challenges of keyhole limpet hemocyanin (KLH) and tuberculin purified protein derivative (PPD) in healthy volunteers, as a potential model to test T cell-targeted investigational agents. SUBJECTS, TREATMENT AND METHODS: Forty-nine subjects received either KLH, PPD, or PBS repeat skin challenges, and clinical assessments including induration, erythema and Laser Doppler Imaging. Skin biopsies or suction blisters were taken after challenge to investigate the cellular infiltrate of the challenge site, the T cell activation status, as determined by LAG-3 expression, and, specifically for the blister, the concentrations of inflammatory cytokines. Point estimates, estimates of variation and corresponding 95% confidence intervals were constructed for each type of challenge and timepoint. RESULTS: The DTH response could be measured at 48 and 120 h post-KLH and PPD challenge with induration, erythema and Laser Doppler Imaging, with 48 h post-challenge demonstrating the peak of the response. PPD was well tolerated in subjects after multiple challenges, however, a significant number of KLH-treated subjects demonstrated an injection site reaction 6-7 days following the SC injection. PPD demonstrated a boost effect on the second challenge as measured by increased induration, where as this was not noted consistently for KLH. Compared to unchallenged and PBS control-injected skin, increased T cell numbers were detected in the challenge site by both the skin suction blister and biopsy technique, at either time point following KLH or PPD challenge. Use of the T cell activation marker LAG-3 demonstrated the activated phenotype of these cells. In skin blisters, higher numbers of LAG-3+ T cells were detected at 48 h post-challenge, whereas in the biopsies, similar numbers of LAG-3+ cells were observed at both 48 and 120 h. Analysis of blister T cell subpopulations revealed some differences in phenotypes between the time points and between the CD4 and CD8 T cells. Blister cytokine analysis revealed a pro-inflammatory dominated signature in PPD-challenged skin. CONCLUSIONS: In summary, our data support the use of a repeat KLH and PPD DTH challenge in clinical trials and that the clinical measures of induration and to a lesser extent erythema are appropriate to monitor the clinical DTH response. Both the blister and biopsy can be utilised to assess and quantify activated T cells and at the dose used, PPD was better tolerated than KLH and hence may be optimal for future studies.

Safety, tolerability, pharmacokinetics and pharmacodynamics of an anti- oncostatin M monoclonal antibody in rheumatoid arthritis: results from phase II randomized, placebo-controlled trials.

INTRODUCTION: Oncostatin M (OSM) has been implicated in the pathophysiology of rheumatoid arthritis (RA) through its effect on inflammation and joint damage. GSK315234 is a humanised anti-OSM Immunoglobulin G1 (IgG1) monoclonal antibody (mAb). This 3-part study examines the safety, tolerability and efficacy of GSK315234 in patients with active RA. METHOD: This was a 3-part (Parts A, B and C), multicenter study. Part A and Part B were randomised, double-blind, placebo-controlled, Bayesian adaptive dose finding studies to investigate the safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of single (Part A) and 3 repeat (Part B) intravenous infusions of GSK315234 in patients with active RA on a background of methotrexate (MTX). Part C was a single dose, randomised, single-blind, placebo-controlled study to assess subcutaneously administered GSK315234 to patients with active RA on a background of MTX. RESULT: The primary endpoint of the study was mean change in DAS28 at Day 28 in Part A and Day 56 in Part B and C. All patients receiving at least one dose of GSK315234 were included in safety analysis. In Part A, there were statistically significant differences in DAS28 between 3 mg/kg and placebo at Day 56, 84 and 91. There was also a statistically significant difference in DAS28 between 0.3 mg/kg, 3 mg/kg and 10 mg/kg, as compared to placebo, at Day 84. Although these changes were small and occurred late, they supported progression to Part B and C to determine the therapeutic potential of GSK315234. For Part B, no significant difference was observed between 6 mg/kg and placebo. For Part C, a statistically significant difference in DAS28 was observed at Day 40, Day 84 and Day 100 between the 500 mg subcutaneous group, as compared to placebo. No significant findings were observed at any of the time points for EULAR response criteria, ACR20, ACR50 or ACR70. An exploratory analysis of clinical, pharmacokinetic and pharmacodynamics data suggests the lack of efficacy may be due to moderate binding affinity and rapid off-rate of GSK315234 as compared to the higher affinity OSM receptor causing a protein carrier effect prolonging the half life of OSM due to accumulation of the OSM/antibody complex in the serum and synovial fluid. CONCLUSION: Our data highlighted the importance of binding affinity and off-rate effect of a mAb to fully neutralize the target and how this may influence its efficacy and potentially worsen disease activity. Using an anti-OSM mAb with high affinity should test this hypothesis and examine the potential of OSM as a therapeutic target in RA. TRIAL REGISTRATION: ClinicalTrials.gov no: NCT00674635.

Induction of homologous rather than heterologous antigen-specific CD4 T cell responses is critical for functional CD8 T cell responses in mice transgenic for a foreign antigen.

The development of a successful cancer vaccine requires the ability to break immunological tolerance to self-Ags expressed on tumor cells. The transgenic rat insulin promoter (RIP) OVA(LOW) mouse model has been reported to be hyporesponsive for both OVA-specific CD4 and CD8 T cell responses. The experiments described in the current study show that this hyporesponsiveness can be overcome by inclusion of GM-CSF and the TLR7 agonist imiquimod as adjuvants in a DNA immunization regimen with OVA-encoding plasmids. High frequencies of OVA-specific CD8 and CD4 T cells, including a response to a CD4 T cell epitope seen only in the RIP OVA(LOW) mice, were generated by this regimen. These responses were associated with the development of autoimmunity and increased protection to tumor challenge in the RIP OVA(LOW) mice. Heterologous CD4 T cell help has been shown to improve functional CD8 T cell responses, and we confirmed that inclusion of the CD4 T cell epitope pan HLA-DR-binding epitope improved CD8 T cell responses compared with self-Ag alone. Addition of GM-CSF and imiquimod, however, resulted in dominance of the pan HLA-DR-binding epitope-specific response over the OVA-specific CD4 T cell responses, decreased OVA-specific CD8 T cell numbers and function in tolerant RIP OVA(LOW) mice, and failure to induce diabetes. The results of this study suggest that the use of heterologous help needs to be evaluated carefully in the context of specific immunization regimes and that a preferable approach may be adjuvantization of DNA vaccines.

Development of an Escherichia coli expressing listeriolysin-O vaccine against Wilms tumor gene 1-expressing tumors.

Through their ability to induce cytotoxic T-lymphocytes and inhibit Foxp3 T-regulatory cells, Escherichia coli expressing listeriolysin-O (LLO) and a model tumor antigen have been shown to exert strong antitumor activity. The aim of this study is to extend these observations to a self-protein and clinically relevant tumor antigen associated with most types of adult leukemia: Wilms tumor gene 1 (WT1). We demonstrate that an E. coli coexpressing LLO and WT1 is capable of inducing a strong antitumor effect against WT1-expressing tumors in vivo through its ability to induce cytotoxic T-lymphocytes and inhibit the function of Foxp3 T-regulatory cells. Furthermore, we have characterized the immunodominant epitope involved in this effect (NAPYLPSCL) and demonstrated that coinjection of NAPYLPSCL with E. coli-LLO resulted in an antitumor effect largely equivalent to that obtained with E. coli-LLO/WT1. Our data demonstrate that the results obtained with a clinically irrelevant model tumor antigen remain valid with a "real" tumor antigen and that the adjuvant properties of the E. coli-LLO vaccine can be exploited in conjunction with peptides. The results obtained in this study will facilitate the translation of this work to human studies by combining antigenic motifs relevant to specific human leukocyte antigen haplotypes with the adjuvant effect of E. coli-LLO.

Programmed death 1 expression during antiviral treatment of chronic hepatitis B: Impact of hepatitis B e-antigen seroconversion.

UNLABELLED: Hyperexpression of the programmed death 1 (PD-1) molecule is a hallmark of exhausted T-cells, having a negative impact on T-cell activation and function. We studied longitudinally 18 hepatitis B e antigen (HBeAg)-positive patients undergoing treatment with direct antivirals (telbivudine or lamivudine) to determine the relationship between treatment-induced viremia reduction and HBeAg seroconversion with respect to PD-1 levels and T-cell reactivity. PD-1 expression was assessed by (1) flow cytometry and (2) quantitative real-time polymerase chain reaction; hepatitis B virus (HBV)-specific CD8+ T-cells were quantitated by pentamer staining; T-cell reactivity to HBV antigens was determined by interferon gamma (IFNgamma) and interleukin 10 (IL-10) enzyme-linked immunosorbent spot (ELISPOT) assays; and central/effector memory phenotypes were defined by phenotypic markers. PD-1 expression correlated closely with viremia levels. On therapy, PD-1 decreased significantly on total CD8+ T-cells, HBV-specific CD8+ T-cells, and CD3+/CD8- T-cells both as the percentage of positive cells (P < 0.01) and as the mean fluorescent intensity (P < 0.05), and this was paralleled by a marked reduction of PD-1 messenger RNA levels (P = 0.001). HBeAg serocoversion (in 6/18 patients) resulted in a further PD-1 decrease with a 50% reduction in the frequency of PD-1+/CD8+ T-cells, which was not observed in patients remaining HBeAg-positive. The decrease in PD-1 expression was associated with increased frequencies of IFNgamma-producing T-cells and decreased frequencies of IL-10 producing T-cells. At baseline, PD-1 expression correlated directly with the frequency of hepatitis B core antigen (HBcAg) central and effector memory phenotypes, whereas an inverse correlation was observed between PD-1 expression and HBcAg-specific effector phenotypes. CONCLUSION: These results demonstrate that in chronic HBV infection, both viremia levels and HBeAg drive PD-1 expression and resulting T-cell impairment. Treatment-induced suppression of HBV replication reduces PD-1 expression; however, additional immunotherapeutic interventions are needed for restoration of T-cell functions.

Induced recruitment of NK cells to lymph nodes provides IFN-gamma for T(H)1 priming.

Naive T cells are stimulated by antigen-presenting dendritic cells (DCs) in secondary lymphoid organs, but whether other types of cell participate in T cell priming is unclear. Here we show in mice that natural killer (NK) cells, which are normally excluded from lymph nodes, are rapidly recruited in a CCR7-independent, CXCR3-dependent manner to lymph nodes on stimulation by the injection of mature DCs. Recruitment of NK cells is also induced by some, but not all, adjuvants and correlates with the induction of T helper cell type 1 (T(H)1) responses. NK cell depletion and reconstitution experiments show that NK cells provide an early source of interferon-gamma (IFN-gamma) that is necessary for T(H)1 polarization. Taken together, our results identify an induced pathway of NK cell migration in antigen-stimulated lymph nodes and a mechanism by which some adjuvants may facilitate T(H)1 responses.

Imiquimod and resiquimod in a mouse model: adjuvants for DNA vaccination by particle-mediated immunotherapeutic delivery.

Imiquimod, an immune response modifier and inducer of cytokines in vitro and in vivo, has been shown to have potent antiviral and antitumour activity and to act as an adjuvant for protein vaccination. We have undertaken studies in mice to investigate the potential of imiquimod and resiquimod to adjuvant DNA vaccination. These imidazoquinolines were administered by subcutaneous injection at the vaccination site immediately after particle-mediated immunotherapeutic delivery of plasmid DNA using a gene gun. Imiquimod was found to increase the number and maturation status of dendritic cells in draining lymph nodes, and to enhance antigen-specific CD4(+) and CD8(+) T cell responses, as assessed by analyses of clonal expansion, and the quantity and kinetics of cytokine production from these cells in lymph nodes and spleens collected after vaccination. A more substantial increase in IFN-gamma-producing, compared with IL-4-producing CD4(+) T cells suggested that imiquimod biased the immune response towards a predominance of Th1 cells. The analogue resiquimod was found to be to produce a similar Th1 biased immune response with a 10-fold reduced dose compared with imiquimod. Collectively, these studies suggest that both imiquimod and resiquimod may be suitable adjuvants for therapeutic DNA vaccines requiring induction of potent cytotoxic T cell responses.

Characterization of CC-chemokine receptor 7 expression on murine T cells in lymphoid tissues.

Expression of the lymph node homing and CC-chemokine receptor 7 (CCR7), with L-selectin (CD62L), has been shown to divide human memory T cells into two functionally distinct subsets. We generated a polyclonal antibody against murine CCR7 and used this antibody to study CCR7 expression on murine T-cell subsets. Using flow cytometric staining of T cells for visualisation expression of CCR7 in association with CD62L and CD44, a major population of CD4 or CD8 T cells expressing CCR7 were found to be CD62Lhigh CD44low, which would suggest a naïve cell phenotype. By analogy with human studies, memory cells could be subdivided into CCR7high CD62Lhigh CD44high (central memory) and CCR7low CD62Llow CD44high (effector memory). The proportions of these populations were different in lymph node, blood and spleen. Functional, short-term in vitro polyclonal stimulation of blood, spleen and lymph node cells from naive mice demonstrated that CCR7high CD4 T cells produced predominantly interleukin (IL)-2, whereas CCR7low CD4 T cells produced both IL-2 and interferon-gamma (IFN-gamma). However, in contrast to previously published reports, the CCR7high CD8 T-cell subpopulation produced both IFN-gamma and IL-2. Analysis of effector T cells, induced by immunization in vivo, showed that a proportion of activated naïve CD4 T cells down-regulated CCR7 only after multiple cell divisions, and this coincided with the down-regulation of CD62L and production of IL-4 and IFN-gamma. Finally, analysis of effector T cells during the phase of maximal clonal expansion of secondary immune responses in vivo indicated that the vast majority of both IL-2- and IFN-gamma-producing cells are CCR7low, while few cytokine-expressing CCR7high T cells were detected. Our results support the hypothesis, developed from studies with human cells, that CCR7 may separate functionally different murine memory T-cell subpopulations, but indicate additional complexity in that CCR7high CD8 T cells also may produce IFN-gamma.

Infection of mouse bone marrow-derived dendritic cells with recombinant adenovirus vectors leads to presentation of encoded antigen by both MHC class I and class II molecules-potential benefits in vaccine design.

Dendritic cells (DCs) are highly specialised antigen-presenting cells (APCs) that are essential for the initiation and modulation of T cell-mediated immune responses. In order to induce effective CTL responses against most infections and tumours, DCs must prime both CD4(+) and CD8(+) antigen-specific T cells. It is, therefore, important in vaccine design to produce antigen-delivery systems that lead to the simultaneous presentation of multiple histocompatibility complex (MHC) class I- and class II-restricted antigenic peptides by DCs. In this study, the infection of immature mouse bone marrow-derived DCs (BMDCs) with recombinant adenovirus (rAd) vectors led to a marked upregulation of surface costimulatory molecules, IL-12 p40 production and capacity to stimulate both allogeneic and antigen-specific T cells. Furthermore, infection of immature and mature BMDCs with a rAd encoding chicken ovalbumin (OVA) led to presentation of the antigen to TCR-transgenic OVA-specific CD4(+) and CD8(+) T cells. In addition, the activation state of responding CD8(+) T cells was further amplified if they recognised antigen on rAd-transduced BMDCs in the presence of antigen-specific CD4(+) T cells. The results suggest that rAd-encoded OVA protein is secreted by BMDCs, taken up by endocytosis and presented in association with MHC class II molecules for activation of OVA-specific CD4(+) T cells. Consequently, rAd-transduced immature BMDCs become better stimulators of antigen-specific CD4(+) T cells than rAd-infected mature BMDCs. Taken together, these data have important implications for vaccine design, and suggest that infection of immature DCs with rAd encoding MHC class I and class II-restricted T cell epitopes could be an efficient means of inducing effective immune responses.

Perturbation of naive TCR transgenic T cell functional responses and upstream activation events by anti-CD4 monoclonal antibodies.

It is well established that non-depleting anti-CD4 monoclonal antibodies (mAb) have potent immunomodulatory properties in vivo and as such can induce a profound state of tolerance. Receptor blockade, CD4 modulation, or the transmission of a negative signal have all been proposed to explain their effects, however their precise mechanism of action, particularly at the level of cellular signaling, remains obscure. Experiments were thus carried out to examine the underlying mechanisms of action of two non-depleting anti-mouse CD4 mAb, YTS177 and KT6, which differ in their ability to modulate CD4 expression. The effects of the mAb were examined on CD4(+) T cells derived from D0.11.10 TCR transgenic mice. Functional studies revealed that both mAb could effectively block antigen-driven proliferation and IL-2 production but had only modest effects at higher peptide doses. Importantly, mAb pre-treatment of T cells stimulated by sub-optimal peptide seemed to induce an anergy-like state making them unresponsive to subsequent re-stimulation. Analysis of intracellular signaling demonstrated that certain key upstream events such as the phosphorylation of Zap-70 and LAT were also blocked by mAb pretreatment which may be due to interference with stable T cell-APC conjugate formation.