Advances in Immunotherapeutics in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) accounts for up to 95% of all pancreatic cancer cases and is the seventh-leading cause of cancer death. Poor prognosis is a result of late presentation, a lack of screening tests and the fact some patients develop resistance to chemotherapy and radiotherapy. Novel therapies like immunotherapeutics have been of recent interest in pancreatic cancer. However, this field remains in its infancy with much to unravel. Immunotherapy and other targeted therapies have yet to yield significant progress in treating PDAC, primarily due to our limited understanding of the disease immune mechanisms and its intricate interactions with the tumour microenvironment (TME). In this review we provide an overview of current novel immunotherapies which have been studied in the field of pancreatic cancer. We discuss their mechanisms, evidence available in pancreatic cancer as well as the limitations of such therapies. We showcase the potential role of combining novel therapies in PDAC, postulate their potential clinical implications and the hurdles associated with their use in PDAC. Therapies discussed with include programmed death checkpoint inhibitors, Cytotoxic T-lymphocyte-associated protein 4, Chimeric Antigen Receptor-T cell therapy, oncolytic viral therapy and vaccine therapies including KRAS vaccines, Telomerase vaccines, Gastrin Vaccines, Survivin-targeting vaccines, Heat-shock protein (HSP) peptide complex-based vaccines, MUC-1 targeting vaccines, Listeria based vaccines and Dendritic cell-based vaccines.

Cancer cell-derived extracellular vesicles activate hepatic stellate cells in colorectal cancer

Colorectal cancer (CRC) is the 2nd leading cause of cancer-related deaths worldwide, primarily due to the development of metastatic disease. The liver is the most frequently affected site. The metastatic cascade relies on a complex interaction between the immune system, tumor, and distant organs. Communication between the tumor and the metastatic site can be mediated by tumor-derived extracellular vesicles (EVs) and their cargo. The mechanisms underlying this process are starting to be understood through research that has rapidly expanded over the past 15 years. One crucial aspect is the remodeling of the microenvironment at the site of metastasis, which is essential for the formation of a premetastatic niche and the subsequent establishment of metastatic deposits. In the evaluated study, the authors use cellular experiments and a mouse model to investigate how tumour derived extracellular vesicles and their microRNA contents interact with hepatic stellate cells (HSCs). They demonstrate how this may lead to remodelling of the microenvironment and the formation of colorectal liver metastasis using their experimental model. In this mini review, we examine the current evidence surrounding tumour derived EVs and their effect on the tumour microenvironment to highlight potential areas for future research in CRC and other malignancies.

Analysis of ICAM-1 Expression on Bladder Carcinoma Cell Lines and Infectivity and Oncolysis by Coxsackie Virus A21

Oncolytic viruses are biological agents which can easily be delivered at high doses directly to the bladder through a catheter (intravesical), with low risk of systemic uptake and toxicity. To date, a number of viruses have been delivered intravesically in patients and in murine models with bladder cancer and antitumour effects demonstrated. Here, we describe in vitro methods to evaluate Coxsackie virus, CVA21, as an oncolytic virus for the treatment of human bladder cancer by determining the susceptibility of bladder cancer cell lines expressing differing levels of ICAM-1 surface receptor to CVA21.

HOX and PBX gene dysregulation as a therapeutic target in glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM) is the most common high-grade malignant brain tumour in adults and arises from the glial cells in the brain. The prognosis of treated GBM remains very poor with 5-year survival rates of 5%, a figure which has not improved over the last few decades. Currently, there is a modest 14-month overall median survival in patients undergoing maximum safe resection plus adjuvant chemoradiotherapy. HOX gene dysregulation is now a widely recognised feature of many malignancies.

METHODS

In this study we have focused on HOX gene dysregulation in GBM as a potential therapeutic target in a disease with high unmet need.

RESULTS

We show significant dysregulation of these developmentally crucial genes and specifically that HOX genes A9, A10, C4 and D9 are strong candidates for biomarkers and treatment targets for GBM and GBM cancer stem cells. We evaluated a next generation therapeutic peptide, HTL-001, capable of targeting HOX gene over-expression in GBM by disrupting the interaction between HOX proteins and their co-factor, PBX. HTL-001 induced both caspase-dependent and -independent apoptosis in GBM cell lines.

CONCLUSION

In vivo biodistribution studies confirmed that the peptide was able to cross the blood brain barrier. Systemic delivery of HTL-001 resulted in improved control of subcutaneous murine and human xenograft tumours and improved survival in a murine orthotopic model.

O-OGC07 Endoscopically derived oesophageal adenocarcinoma organoids to assess potential response to neo-adjuvant therapy and virotherapy

Background

Organoids are 3D models that retain the architecture and function of the organ from which they are derived. Culture of oesophageal adenocarcinoma organoids from individual’s standard endoscopic biopsies to assess response to therapy could dramatically alter the neo-adjuvant treatment paradigm, giving clarity over who will benefit from therapy, including novel treatment methodologies. Immune checkpoint blockade (ICB) has been shown to be effective in oesophageal adenocarcinoma. Combining Oncolytic Virotherapy with ICB could enhance the action of ICB alone, through selective infection of tumour cells accompanied by immunogenic cell death, with release of neo-tumour antigens and alteration of the tumour microenvironment.

Methods

This study uses organoids derived from endoscopic biopsies to assess the viability of an oncolytic herpes simplex virus in the treatment of oesophageal adenocarcinoma. Samples were taken at staging endoscopy using standard biopsy forceps. Tissue specimens were dissociated using the Miltenyi tumour dissociation kit before being suspended in Matrigel in conditioned media. Media was changed every 48 hours with domes being split every 7-10 days. After >6 passages organoids were incubated with an oncolytic herpes simplex virus lacking ICP 34.5 and 47. Growth was monitored, and green fluorescence protein expression measured using the Incucyte SX5 Live Cell Analysis system.

Results

Organoids were successfully established and cultured beyond 6 passages for patients with oesophageal adenocarcinoma. Organoids incubated with an oncolytic herpes simplex virus demonstrated significantly reduced growth compared to untreated organoids with increased expression of green fluorescence protein indicating viral infection.

Conclusions

We have demonstrated a successful methodology to culture Oesophageal adenocarcinoma organoids from endoscopic biopsies. Further work to determine their responses to standard chemotherapy used in the perioperative phase will help to assess their potential for providing bespoke therapy in the future. Oncolytic herpes simplex virus is able to infect and cause lysis of OAC organoids supporting its potential use in driving an increased inflammatory tumour microenvironment which could be combined with immune checkpoint blockade to induce durable responses for patients.

Abstract P3-10-15: Therapeutic targeting of HOX gene dysregulation in triple negative breast cancer

Introduction: Triple Negative Breast Cancer (TNBC) is a heterogeneous disease, clinically defined for its aggressive tumour behaviour, metastatic ability and poor prognosis. Homeobox (HOX) genes are a family of homeodomain-containing transcription factors, which establish and maintain the identity and fate of cells and tissues during normal embryogenesis and organ development. A total of 39 HOX genes exist, located in four clusters (A-D) on different chromosomes. HOX genes are dysregulated in most cancers and they have an established role in driving key processes in breast carcinogenesis, including the regulation of the cell cycle, apoptosis, angiogenesis and metastasis. In this study, we evaluated the anti-tumour efficacy of a novel inhibitor of HOX protein function, HTL-001, which antagonizes the interactions between HOX proteins and their PBX cofactors. HTL-001, developed by HOX Therapeutics Ltd, is a synthetic peptide of 18 amino acids, comprised of a hexapeptide sequence, which resembles that on HOX proteins of paralogs 1-9, and a short C-terminal polyarginine sequence for cell penetration. We evaluated the efficacy of HTL-001 in vitro as a monotherapy in all cell lines representing all molecular classifications of breast cancer and in combination with chemotherapeutics for TNBC therapy. Most importantly, HTL-001 was examined in MDA-MB-231-BR cells, which have a propensity to metastasise to the brain, reflecting the disease course frequently observed in human patients.

Methods: The differential expression of HOX and PBX genes in all subtypes of breast cancer was evaluated using bioinformatics analysis of TCGA and Oncomine data. The sensitivity to HTL-001 of breast cancer-derived cell lines of different molecular classifications, was determined using Cell Proliferation (MTS) Assay and FACS-based Annexin Assay. The anti-tumour effect of HTL-001 in combination with various chemotherapeutics was assessed and analysed for synergy using Bliss Analysis. The expression of genes previously shown to respond to HOX/PBX inhibition was measured from extracted RNA and protein using RT-qPCR and western blotting, respectively. The in vivo efficacy of HTL-001 will be investigated using a mouse flank tumour xenograft model with MDA-MB-231-BR cells, representative of TNBC.

Results: TCGA and Oncomine data analysis showed TNBC tumours have a unique signature of HOX gene dysregulation, different to that of all other types of breast tumours, relative to normal breast tissues; most importantly upregulation in HOXB2 and HOXB3 genes. Targeting HOX/PBX dimers with HTL-001, induced apoptotic cell death in all breast cancer cell lines including; MCF-7, ZR-75-1, MDA-MB-231, BT-20 and SK-BR-3, with the highest sensitivity seen in brain seeking MDA-MB-231-BR cells. HTL-001 significantly upregulated the expression of key apoptotic and anti-survival genes including; AIF, cFOS, and DUSP1, resulting in the induction of apoptotic cell death in all breast cancer cell lines tested. Furthermore, we observed high levels of synergy between HTL-001 and the chemotherapeutic agents, Paclitaxel, Palbociclib and 5-Fluorouracil.

Conclusion: HTL-001 is a novel inhibitor of HOX and PBX protein interactions capable of marked in vitro cytotoxicity in all types of breast cancer cells, particularly in TNBC. HTL-001 induced rapid apoptosis and triggered a downstream unique signature after target engagement. HTL-001 is currently the only therapy which targets HOX gene dysregulation and in doing so, may help address the current urgent unmet therapeutic need in TNBC through its unique mechanism of action and high levels of synergy with conventional anti-cancer agents.

Citation Format: Einthavy Arunachalam, Guy R Simpson, Carla Sofia Möller-Levet, Nicola Annels, Richard Morgan, Timothy Robert Crook, Hardev Singh Pandha. Therapeutic targeting of HOX gene dysregulation in triple negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-15.

Rationale and design of the POLEM trial: avelumab plus fluoropyrimidine-based chemotherapy as adjuvant treatment for stage III mismatch repair deficient or POLE exonuclease domain mutant colon cancer: a phase III randomised study

BACKGROUND

10%-15% of early-stage colon cancers harbour either deficient mismatch repair (dMMR), microsatellite instability high (MSI-H) or POLE exonuclease domain mutations, and are characterised by high tumour mutational burden and increased lymphocytic infiltrate. Metastatic dMMR colon cancers are highly sensitive to immune checkpoint inhibition, and recent data show POLE-mutant tumours are similarly responsive. We are conducting a phase III randomised trial to determine if the addition of the anti-PD-L1 antibody avelumab following adjuvant chemotherapy improves disease-free survival (DFS) in patients with stage III dMMR/MSI-H or POLE mutant colon cancer and is a cost-effective approach for the UK National Health Service (NHS).

METHODS

We are recruiting patients with completely resected, stage III colon cancer confirmed to have dMMR/MSI-H, locally or POLE exonuclease domain mutation on central testing. Eligible patients are randomised in a 1:1 ratio to standard fluoropyrimidine-based chemotherapy (capecitabine, oxaliplatin for 12 weeks or capecitabine for 24 weeks) or chemotherapy, followed by avelumab (10 mg/kg, 2 weekly for 24 weeks). Stratification is by chemotherapy received and MMR/MSI-H status. The primary endpoint is DFS. Secondary endpoints include overall survival, toxicity, quality of life and health resource use. The 3-year DFS rate in the control arm is expected to be ~75%. Avelumab is expected to improve the 3-year DFS rate by 12% (ie, 87%). Target accrual is 402 patients, which provides 80% power to detect an HR of 0.48 for DFS at a two-sided alpha of 0.05. This national, multicentre phase III trial is sponsored by the Royal Marsden NHS Foundation Trust and it is anticipated that approximately 40 centres in the UK will participate. This study opened to recruitment in August 2018.

TRIAL REGISTRATION NUMBER

NCT03827044.

Oncolytic Immunotherapy for Bladder Cancer Using Coxsackie A21 Virus: Using a Bladder Tumor Precision-Cut Slice Model System to Assess Viral Efficacy

Oncolytic viruses are anticancer agents that selectively target and kill cancer cells by direct lysis, while at the same time stimulating a tumor antigen-specific adaptive immune response. These promising therapeutic agents target multiple cancers and have already proven to be an effective treatment option for solid malignancies. One such agent, T-Vec (Talimogene laherparepvec) has been licensed and is in routine clinical use for treatment of malignant melanoma.Non-muscle invasive bladder cancer (NMIBC) is an ideal potential target for oncolytic immunotherapy as locally instilled live biological therapy using Bacille Calmette-Guerin (BCG) is already well established in the clinical setting. Coxsackievirus A21 (CVA21) is a novel intercellular adhesion molecule-1 (ICAM-1)-targeted immunotherapeutic virus. We have investigated CVA21-induced cytotoxicity in a panel of human bladder cancer cell lines, revealing a range of sensitivities largely correlating with expression of the viral receptor ICAM-1. CVA21 in combination with low doses of mitomycin-C enhanced CVA21 viral replication and oncolysis by increasing surface expression levels of ICAM-1. In addition to cell lines and an animal model a key component of our studies into oncolytic immunotherapy for bladder cancer was the use of a bladder tumor precision slice preclinical model system which represents tumor architecture, heterogeneity, and the complexity of a tumor in vitro. Results seen in cell lines were reflected in the tumor slice model whereby levels of virus protein expression and induction of apoptosis were enhanced with prior exposure to mitomycin-C. In this chapter we demonstrate the utility of the precision cut tumor slice model as a unique organotypic model to test oncolytic viruses. We will describe how to prepare and slice the tumor using a vibrating microtome together with the optimum culture and conditions for treatment.

Engrailed-2 (EN2) - a novel biomarker in epithelial ovarian cancer

Background

Epithelial ovarian cancer is a common malignancy, with no clinically approved diagnostic biomarker. Engrailed-2 (EN2) is a homeodomain-containing transcription factor, essential during embryological neural development, which is dysregulated in several cancer types. We evaluated the expression of EN2 in Epithelial ovarian cancer, and reviewed its role as a biomarker.

Methods

We evaluated 8 Epithelial ovarian cancer cell lines, along with > 100 surgical specimens from the Royal Surrey County Hospital (2009–2014). In total, 108 tumours and 5 normal tissue specimens were collected. En2 mRNA was evaluated by semi-quantitative RT-PCR. Histological sub-type, and platinum-sensitive/−resistant status were compared. Protein expression was assessed in cell lines (immunofluorescence), and in > 150 tumours (immunohistochemistry).

Results

En2 mRNA expression was elevated in serous ovarian tumours compared with normal ovary (p < 0.001), particularly in high-grade serous ovarian cancer (p < 0.0001) and in platinum-resistant tumours (p = 0.0232). Median Overall Survival and Progression-free Survival were reduced with high En2 expression (OS = 28 vs 42 months, p = 0.0329; PFS = 8 vs 27 months; p = 0.0004). Positive cytoplasmic EN2 staining was demonstrated in 78% of Epithelial ovarian cancers, with absence in normal ovary. EN2 positive high-grade serous ovarian cancer patients had a shorter PFS (10 vs 17.5 months; p = 0.0103).

Conclusion

The EN2 transcription factor is a novel ovarian cancer biomarker. It demonstrates prognostic value, correlating with worse Overall Survival and Progression-free Survival. It is hoped that further work will validate its use as a biomarker, and provide insight into the role of EN2 in the development, progression and spread of ovarian cancer.

Prostate cancer vaccines

In 2010, the US FDA approved the first therapeutic cancer vaccine for the treatment of castration refractory prostate cancer - sipuleucel-T. Prostate cancer is an ideal model for cancer vaccine development based on the ready demonstration of humoral and cellular immunity to a range of cancer antigens as well as often slow progression which means that patients who are otherwise well may have a radiologically evaluable minor progression, after conventional treatment and can undergo vaccine therapy over sufficient periods of time, so as to allow the generation of a robust antitumor response. The association of prostate cancer with one of the few serum cancer biomarkers in general use has also allowed assessment of response and risk stratification of patients. In this review, we will examine key aspects of the evolution of prostate cancer vaccines, which provides an accurate prototype for other cancers, and the challenges we face.

Abstract 3638: Detecting prostate cancer in BRCA1 and BRCA2 mutation carriers: A role for EN2

EN2 is part of the HOX gene family and plays a role in foetal development. More recently a potential oncogenic role for the protein has been postulated and its utility as a cancer biomarker has been explored in prostate cancer (PrCa) and breast cancer. Carriers of mutations in the BRCA1 and BRCA2 genes have an increased risk of PrCa (1.8-fold and 5-fold respectively) and their tumours tend to be more aggressive and advanced than sporadic cases. Currently there is no national screening program for BRCA mutation carriers in the UK, and the IMPACT study was set up to evaluate PSA screening in this particular group. Here we analyse the efficacy of the urinary EN2 protein and auto-antibody against EN2 in serum and urine as markers of early cancer detection within this higher risk group. Urine and serum were taken from the IMPACT screening study which enrolled individuals aged between 40 and 69 who were unaffected by PrCa at time of enrolment into the study (n= 418). All participants were from families harbouring a BRCA1 or BRCA2 mutation and were either BRCA mutation carriers themselves or controls with a negative predictive BRCA genetic test. They underwent annual PSA test with a PSA of &gt; 3.0 ng/ml triggering a diagnostic biopsy. Annual urine and serum samples were collected from this cohort. EN2 protein was measured in the urine using an ELISA; (positive = &gt; 42.5ng/ml). The autoantibody was measured in serum and urine; (positive = measurement of 2 standard deviations above the mean value when measured in a cohort of healthy volunteers). Using detection of EN2 protein in urine alone our initial results demonstrated the test had a sensitivity of 71.4% and a specificity of 75.4% when discriminating between those with a positive biopsy and those with a negative biopsy; the ROC AUC was 0.767. The difference in EN2 level between those diagnosed with cancer and those who were not was significant (p = &lt;0.001). EN2 antibody measured in serum was less sensitive but more specific that the urinary protein (33.3% and 83.6% respectively), when combined with urinary protein the sensitivity is 85.7% with a specificity of 63.3% and ROC AUC 0.745. Further samples are in the process of being analysed and data and results of these will be presented. In addition a new assay to measure urinary antibody is currently under development and results from this test will be also shown. EN2 protein and auto-antibody measurement warrants further investigation as a PrCa biomarker in this higher risk group with genetic predisposition to PrCa.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3638. doi:1538-7445.AM2012-3638

Abstract A67: Increased circulating HLA-DRneg, Lin1 lo/neg, CD33+ CD11b+ myeloidderived suppressor cells correlate with increased arginase levels in patients with prostate cancer

Due to our increased understanding of tumor immunology a number of immunotherapeutic approaches have been successfully introduced into the clinic and further promising therapeutic strategies are being investigated in on-going clinical trials. However, evaluation of anti-tumor immunity in such trials as in animal models has shown that tumor escape from immune recognition and tumor-mediated suppression of anti-tumor immunity can pose a significant obstacle to successful cancer therapy.

One of the main cell types that have emerged as potent suppressors of T cell-mediated immunity are myeloid derived suppressor cells (MDSCs). MDSCs are a heterogeneous population of immature cells of myeloid origin with a wide repertoire of effector mechanisms. While there are published data on circulating MDSC in cancer patients with diverse primary tumors, there is little published data investigating MDSCs specifically in prostate cancer. Following on from our recent study looking at HLADR- Lin1low/− CD33+ CD11b+ MDSCs in pancreatic, esophageal and gastric cancer patients we sought to determine whether this population of MDSCs also played a role in prostate cancer. Peripheral blood was collected from 75 prostate cancer patients and 50 healthy controls. PBMC were harvested with subsequent flow cytometric analysis of MDSC. MDSCs were highly statistically significantly elevated in prostate cancer patients compared with healthy controls (p&lt;0.0001). In this cohort there was no evidence of increasing MDSC % with stage of disease. MDSCs exert their immunosuppressive activity through multiple mechanisms, including arginine depletion. MDSC expressing arginase I deplete L-arginine from the microenvironment and profoundly inhibit T-cell function. Analysis of arginase I levels by ELISA on the plasma from the same prostate cancer patient cohort showed that Arginase I levels were also highly statistically significantly elevated in prostate cancer patients compared with controls (p&lt;0.0001). There was a clear association between increasing Arginase I level and increasing MDSC percentage (p=0.0195). In contrast to our finding in upper gastrointestinal cancers where significant elevations of the Th2 cytokine interleukin-13 (IL-13) were found and correlated with MDSC levels, we were unable to detect IL-13 in the plasma of prostate cancer patients. This probably reflects the diverse combinations of cytokines produced by different tumors and the large number of potential MDSC-inducing and MDSC activating factors.

These data not only add to our understanding of the immunobiology of prostate cancer but provide the rationale for combining immunotherapy studies with MDSC inhibition strategies.

Citation Format: Nicola Annels, Rachel Gabitass, Gary Middleton, Hardev Pandha. Increased circulating HLA-DRneg, Lin1 lo/neg, CD33+ CD11b+ myeloidderived suppressor cells correlate with increased arginase levels in patients with prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A67.

Engrailed-2 (EN2): a tumor specific urinary biomarker for the early diagnosis of prostate cancer

PURPOSE

Prostate cancer (PC) is the second most common cause of cancer related death in men. A number of key limitations with prostate specific antigen (PSA), currently the standard detection test, has justified evaluation of new biomarkers. We have assessed the diagnostic potential of Engrailed-2 (EN2) protein, a homeodomain-containing transcription factor expressed in PC cell lines and secreted into the urine by PC in men.

EXPERIMENTAL DESIGN

EN2 expression in PC cell lines and prostate cancer tissue was determined by semi-quantative RT-PCR and immunohistochemistry. First pass urine [without prior digital rectal examination (DRE)] was collected from men presenting with urinary symptoms (referred to exclude/confirm the presence of prostate cancer) and from controls. EN2 protein was measured by ELISA in urine from men with PC (n = 82) and controls (n = 102).

RESULTS

EN2 was expressed and secreted by PC cell lines and PC tissue but not by normal prostate tissue or stroma. The presence of EN2 in urine was highly predictive of PC, with a sensitivity of 66% and a specificity of 88.2%, without requirement for DRE. There was no correlation with PSA levels. These results were confirmed independently by a second academic center.

CONCLUSIONS

Urinary EN2 is a highly specific and sensitive candidate biomarker of prostate cancer. A larger multicenter study to further evaluate the diagnostic potential of EN2 is justified.

Langerhans cell histiocytosis reveals a new IL-17A-dependent pathway of dendritic cell fusion

IL-17A is a T cell-specific cytokine that is involved in chronic inflammations, such as Mycobacterium infection, Crohn's disease, rheumatoid arthritis and multiple sclerosis. Mouse models have explained the molecular basis of IL-17A production and have shown that IL-17A has a positive effect not only on granuloma formation and neurodegeneration through unknown mechanisms, but also on bone resorption through Receptor activator of NF-kappaB ligand (RANKL) induction in osteoblasts. Langerhans cell histiocytosis (LCH) is a rare disease of unknown etiology, lacking an animal model, that cumulates symptoms that are found separately in various IL-17A-related diseases, such as aggressive chronic granuloma formation, bone resorption and soft tissue lesions with occasional neurodegeneration. We examined IL-17A in the context of LCH and found that there were high serum levels of IL-17A during active LCH and unexpected IL-17A synthesis by dendritic cells (DCs), the major cell type in LCH lesions. We also found an IL-17A-dependent pathway for DC fusion, which was highly potentiated by IFN-gamma and led to giant cells expressing three major tissue-destructive enzymes: tartrate resistant acidic phosphatase and matrix metalloproteinases 9 and 12. IFN-gamma expression has been previously documented in LCH and observed in IL-17A-related diseases. Notably, serum IL-17A-dependent fusion activity correlates with LCH activity. Thus, IL-17A and IL-17A-stimulated DCs represent targets that may have clinical value in the treatment of LCH and other IL-17A-related inflammatory disorders.

The flow cytometric analysis of telomere length in antigen-specific CD8+ T cells during acute Epstein-Barr virus infection

Acute infectious mononucleosis (AIM) induced by Epstein-Barr virus (EBV) infection is characterized by extensive expansion of antigen-specific CD8+ T cells. One potential consequence of this considerable proliferative activity is telomere shortening, which predisposes the EBV-specific cells to replicative senescence. To investigate this, a method was developed that enables the simultaneous identification of EBV specificity of the CD8+ T cells, using major histocompatibility complex (MHC) class I/peptide complexes, together with telomere length, which is determined by fluorescence in situ hybridization. Despite the considerable expansion, CD8+ EBV-specific T cells in patients with AIM maintain their telomere length relative to CD8+ T cells in normal individuals and relative to CD4+ T cells within the patients themselves and this is associated with the induction of the enzyme telomerase. In 4 patients who were studied up to 12 months after resolution of AIM, telomere lengths of EBV-specific CD8+ T cells were unchanged in 3 but shortened in one individual, who was studied only 5 months after initial onset of infection. Substantial telomere shortening in EBV-specific CD8+ T cells was observed in 3 patients who were studied between 15 months and 14 years after recovery from AIM. Thus, although telomerase activation may preserve the replicative potential of EBV-specific cells in AIM and after initial stages of disease resolution, the capacity of these cells to up-regulate this enzyme after restimulation by the persisting virus may dictate the extent of telomere maintenance in the memory CD8+ T-cell pool over time.

T cell selection during the evolution of CD8+ T cell memory in vivo

Memory T cell responses are frequently highly restricted in terms of receptor usage. How and when such clonotypic dominance is established remains poorly understood. Here we have investigated the evolution of the T cell responses to an epitope from Epstein-Barr virus (EBV), (FLRGRAYGL), by analyzing TCR use of clones specific for this epitope, derived from peripheral blood mononuclear cells taken from individuals early during primary EBV infection and up to 3 years later. We show that, in a given individual, particular T cell clonotypes are selected early during the primary response to this epitope and that the same clonotypes dominate the late memory response. In one individual direct analysis of HLA-B8-restricted FLRGRAYGL-specific T cells, isolated from peripheral blood lymphocytes taken during primary EBV infection using a tetrameric MHC-peptide complex, confirmed the early selection of the dominant clonotypes.

Direct visualization of antigen-specific CD8+ T cells during the primary immune response to Epstein-Barr virus In vivo

Primary infection with virus can stimulate a vigorous cytotoxic T cell response. The magnitude of the antigen-specific component versus the bystander component of a primary T cell response remains controversial. In this study, we have used tetrameric major histocompatibility complex-peptide complexes to directly visualize antigen-specific cluster of differentration (CD)8+ T cells during the primary immune response to Epstein-Barr virus (EBV) infection in humans. We show that massive expansion of activated, antigen-specific T cells occurs during the primary response to this virus. In one individual, T cells specific for a single EBV epitope comprised 44% of the total CD8+ T cells within peripheral blood. The majority of the antigen-specific cells had an activated/memory phenotype, with expression of human histocompatibility leukocyte antigen (HLA) DR, CD38, and CD45RO, downregulation of CD62 leukocyte (CD62L), and low levels of expression of CD45RA. After recovery from AIM, the frequency of antigen-specific T cells fell in most donors studied, although populations of antigen-specific cells continued to be easily detectable for at least 3 yr.