Transfection of dendritic cells with in vitro-transcribed CMV RNA induces polyclonal CD8+- and CD4+-mediated CMV-specific T cell responses

Immunotherapy with adoptive cytomegalovirus-specific T cells transfer: Summarizing latest gene engineering techniques

Cytomegalovirus (CMV) infection remains a major complication following allogeneic hematopoietic stem cell transplantation (HSCT). T cell response plays a critical role in inducing long-term immunity against CMV infection/reactivation that impairs during HSCT. Adoptive T cell therapy (ACT) via transferring CMV-specific T cells from a seropositive donor to the recipient can accelerate virus-specific immune reconstitution. ACT, as an alternative approach, can restore protective antiviral T cell immunity in patients. Different manufacturing protocols have been introduced to isolate and expand specific T cells for the ACT clinical setting. Nevertheless, HLA restriction, long-term manufacturing process, risk of alloreactivity, and CMV seropositive donor availability have limited ACT broad applicability. Genetic engineering has developed new strategies to produce TCR-modified T cells for diagnosis, prevention, and treatment of infectious disease. In this review, we presented current strategies required for ACT in posttransplant CMV infection. We also introduced novel gene-modified T cell discoveries in the context of ACT for CMV infection. It seems that these innovations are enabling to improvement and development of ACT utilization to combat posttransplant CMV infection.

Clinical and immunological effects of mRNA vaccines in malignant diseases

In vitro-transcribed messenger RNA-based therapeutics represent a relatively novel and highly efficient class of drugs. Several recently published studies emphasize the potential efficacy of mRNA vaccines in treating different types of malignant and infectious diseases where conventional vaccine strategies and platforms fail to elicit protective immune responses. mRNA vaccines have lately raised high interest as potent vaccines against SARS-CoV2. Direct application of mRNA or its electroporation into dendritic cells was shown to induce polyclonal CD4+ and CD8+ mediated antigen-specific T cell responses as well as the production of protective antibodies with the ability to eliminate transformed or infected cells. More importantly, the vaccine composition may include two or more mRNAs coding for different proteins or long peptides. This enables the induction of polyclonal immune responses against a broad variety of epitopes within the encoded antigens that are presented on various MHC complexes, thus avoiding the restriction to a certain HLA molecule or possible immune escape due to antigen-loss. The development and design of mRNA therapies was recently boosted by several critical innovations including the development of technologies for the production and delivery of high quality and stable mRNA. Several technical obstacles such as stability, delivery and immunogenicity were addressed in the past and gradually solved in the recent years.This review will summarize the most recent technological developments and application of mRNA vaccines in clinical trials and discusses the results, challenges and future directions with a special focus on the induced innate and adaptive immune responses.

New extracellular factors in glioblastoma multiforme development: neurotensin, growth differentiation factor-15, sphingosine-1-phosphate and cytomegalovirus infection

Recent years have seen considerable progress in understanding the biochemistry of cancer. For example, more significance is now assigned to the tumor microenvironment, especially with regard to intercellular signaling in the tumor niche which depends on many factors secreted by tumor cells. In addition, great progress has been made in understanding the influence of factors such as neurotensin, growth differentiation factor-15 (GDF-15), sphingosine-1-phosphate (S1P), and infection with cytomegalovirus (CMV) on the 'hallmarks of cancer' in glioblastoma multiforme. Therefore, in the present work we describe the influence of these factors on the proliferation and apoptosis of neoplastic cells, cancer stem cells, angiogenesis, migration and invasion, and cancer immune evasion in a glioblastoma multiforme tumor. In particular, we discuss the effect of neurotensin, GDF-15, S1P (including the drug FTY720), and infection with CMV on tumor-associated macrophages (TAM), microglial cells, neutrophil and regulatory T cells (T_reg), on the tumor microenvironment. In order to better understand the role of the aforementioned factors in tumoral processes, we outline the latest models of intratumoral heterogeneity in glioblastoma multiforme. Based on the most recent reports, we discuss the problems of multi-drug therapy in treating glioblastoma multiforme.

Comprehensive Analysis of Cytomegalovirus pp65 Antigen-Specific CD8+ T Cell Responses According to Human Leukocyte Antigen Class I Allotypes and Intraindividual Dominance

To define whether individual human leukocyte antigen (HLA) class I allotypes are used preferentially in human cytomegalovirus (CMV)-specific cytotoxic T lymphocyte responses, CD8⁺ T cell responses restricted by up to six HLA class I allotypes in an individual were measured in parallel using K562-based artificial antigen-presenting cells expressing both CMV pp65 antigen and one of 32 HLA class I allotypes (7 HLA-A, 14 HLA-B, and 11 HLA-C) present in 50 healthy Korean donors. The CD8⁺ T cell responses to pp65 in the HLA-C allotypes were lower than responses to those in HLA-A and -B allotypes and there was no difference between the HLA-A and HLA-B loci. HLA-A*02:01, -B*07:02, and -C*08:01 showed the highest magnitude and frequency of immune responses to pp65 at each HLA class I locus. However, HLA-A*02:07, -B*59:01, -B*58:01, -B*15:11, -C*03:02, and -C*02:02 did not show any immune responses. Although each individual has up to six different HLA allotypes, 46% of the donors showed one allotype, 24% showed two allotypes, and 2% showed three allotypes that responded to pp65. Interestingly, the frequencies of HLA-A alleles were significantly correlated with the positivity of specific allotypes. Our results demonstrate that specific HLA class I allotypes are preferentially used in the CD8⁺ T cell immune response to pp65 and that a hierarchy among HLA class I allotypes is present in an individual.

Implementing combinatorial immunotherapeutic regimens against cancer: The concept of immunological conditioning

Harnessing the host immune system to eradicate cancer has a high therapeutic potential. One paradigm of anticancer immunotherapy is represented by allogeneic stem cell transplantation. In this setting, the host must be conditioned prior to transplantation, allowing for engraftment and subsequent graft-vs.-tumor reactivity. Conditioning may also be a prerequisite for the efficacy of other immunotherapeutic regimens. In particular, tumor debulking followed by conditioning (aimed at blocking endogenous inhibitory stimuli, for instance upon the depletion of regulatory T cells or the inhibition of immune checkpoints) and subsequent immunization (for instance by means of patient-tailored vaccines) based on innovative adjuvants (such as RIG-I ligands) may allow for the elicitation of superior antitumor immune responses. Repetitive boosting might then maintain immunosurveillance. An intense wave of investigation on the optimal timing of immunostimulatory interventions with respect to the administration of immunogenic chemotherapeutics and on the use of small drugs that promote efficient antitumor immune responses will end up in the generation of highly effective immunotherapeutic anticancer regimens.

Regulation of dectin-1–mediated dendritic cell activation by peroxisome proliferator–activated receptor-gamma ligand troglitazone

Dectin-1 is the major receptor for fungal β-glucans. The activation of Dectin-1 leads to the up-regulation of surface molecules on dendritic cells (DCs) and cytokine secretion. Furthermore, Dectin-1 is important for the recruitment of leukocytes and the production of inflammatory mediators. Peroxisome proliferator–activated receptor-γ (PPAR-γ) and its ligands, cyclopentenone prostaglandins or thiazolidinediones, have modulatory effects on B-cell, T-cell, and DC function. In the present study, we analyzed the effects of troglitazone (TGZ), a high-affinity synthetic PPAR-γ ligand, on the Dectin-1–mediated activation of monocyte-derived human DCs. Dectin-1–mediated activation of DCs was inhibited by TGZ, as shown by down-regulation of costimulatory molecules and reduced secretion of cytokines and chemokines involved in T-lymphocyte activation. Furthermore, TGZ inhibited the T-cell–stimulatory capacity of DCs. These effects were not due to a diminished expression of Dectin-1 or to a reduced phosphorylation of spleen tyrosine kinase; they were mediated by the inhibition of downstream signaling molecules such as mitogen-activated protein kinases and nuclear factor-κB. Furthermore, curdlan-mediated accumulation of caspase recruitment domain 9 (CARD9) in the cytosol was inhibited by TGZ. Our data demonstrate that the PPAR-γ ligand TGZ inhibits Dectin-1–mediated activation by interfering with CARD9, mitogen-activated protein kinase, and nuclear factor-κB signaling pathways. This confirms their important role as negative-feedback regulators of potentially harmful inflammatory responses.

Phase I/II trial of a dendritic cell vaccine transfected with DNA encoding melan A and gp100 for patients with metastatic melanoma

This trial tested a dendritic cell (DC) therapeutic cancer vaccine in which antigen is loaded using a novel non-viral transfection method enabling the uptake of plasmid DNA condensed with a cationic peptide. Proof of principle required the demonstration of diverse T lymphocyte responses following vaccination, including multiple reactivities restricted through both major histocompatibility complex (MHC) class I and II. Patients with advanced melanoma were offered four cycles of vaccination with autologous DC expressing melan A and gp100. Disease response was measured using Response Evaluation Criteria in Solid Tumours. Circulating MHC class I- and II-restricted responses were measured against peptide and whole antigen targets using interferon-γ ELIspot and enzyme-linked immunosorbent assay assays, respectively. Responses were analyzed across the trial population and presented descriptively for some individuals. Twenty-five patients received at least one cycle. Vaccination was well tolerated. Three patients had reduction in disease volume. Across the trial population, vaccination resulted in an expansion of effector responses to both antigens, to the human leukocyte antigen A2-restricted modified epitope, melan A ELAGIGILTV, and to a panel of MHC class I- and II-restricted epitopes. Vaccination with mature DC non-virally transfected with DNA encoding antigen had biological effect causing tumour regression and inducing diverse T lymphocyte responses.

Intradermal vaccinations with RNA coding for TAA generate CD8+ and CD4+ immune responses and induce clinical benefit in vaccinated patients

The aim of this phase I/II nonrandomized trial was to assess feasibility, safety as well as immunological and clinical responses of a mRNA-based vaccination in patients with stage IV renal cell cancer using granulocyte-macrophage colony stimulating factor (GM-CSF) as adjuvant. Intradermal injections of in vitro transcribed naked mRNA, which was generated using plasmids coding for the tumor-associated antigens mucin 1(MUC1), carcinoembryonic (CEA), human epidermal growth factor receptor 2 (Her-2/neu), telomerase, survivin, and melanoma-associated antigen 1 (MAGE-A1) were performed in 30 enrolled patients. In the first 14 patients (cohort A) vaccinations were administered on days 0, 14, 28, and 42 (20 µg/antigen) while in the consecutive 16 patients (cohort B) an intensified protocol consisting of injections at days 0-3, 7-10, 28, and 42 (50 µg/antigen) was used. In both cohorts, after this induction period, vaccinations were repeated monthly until tumor progression analyzed by Response Evaluation Criteria In Solid Tumors criteria (RECIST). Vaccinations were well tolerated with no severe side effects and induced clinical responses [six stable diseases (SD) and one partial response in cohort A and nine SD in cohort B]. In cohort A, 35.7% survived 4 years (median survival 24 months) compared to 31.25% in cohort B (median survival 29 months). Induction of CD4(+) and CD8(+) T cell responses was shown for several tumor-associated antigens (TAA) using interferon-γ (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) and Cr-release assays.

Pneumonitis in human cytomegalovirus infection

Human cytomegalovirus (HCMV) is a beta herpes virus with a double stranded DNA genome of 240kbp. The virus is prevalent and establishes a latent infection in most adults. HCMV is an opportunistic pathogen for patients with impaired cellular immunity. HCMV pneumonia is a common presentation of HCMV disease in immunocompromised patients. The incidence of HCMV pneumonitis can be as high as 90% in lung transplant recipients. This paper takes a fresh look at the challenging perspectives of molecular, immunologic, cellular, diagnostic, clinical, and therapeutic characteristics of HCMV infection as future targets for development of antiviral strategies.

Cross-presentation of HCMV chimeric protein enables generation and measurement of polyclonal T cells

CD8(+) T cell immunity has a critical function in controlling human cytomegalovirus (HCMV) infection. In immunocompromized individuals, HCMV reactivation or disease can lead to increased morbidity and mortality, particularly in transplant recipients. In this setting, adoptive transfer of HCMV-specific CD8(+) T cells is a promising vaccine strategy to restore viral immunity, with most clinical approaches focussing on the use of peptides for the generation of single epitope-specific CD8(+) T cells. We show that using an IE1-pp65 chimeric protein as the antigen source promotes effective cross-presentation, by monocyte-derived dendritic cells (MoDCs), to generate polyclonal CD8(+) T cell epitopes. By exploring human leukocyte antigen (HLA)-restricted immunodominance hierarchies both within and across two immunodominant proteins, we show that HLA-B7 epitopes elicit higher CD8(+) T cell responses compared with HLA-A1, -A2 or -B8. This study provides important evidence highlighting both the efficacy of the IE1-pp65 chimeric protein and the importance of immunodominance in designing future therapeutic vaccines.

Generation of antigen-specific CTL responses using RGS1 mRNA transfected dendritic cells

Advances in tumor immunology and Identification of tumor-associated antigens (TAAs) provide a basis for the development of novel immunotherapies to treat malignant diseases. In order to identify novel TAAs, we performed comparative microarray analysis of (heterogeneous) tissues and found regulator of G protein-signaling 1 (RGS1) extensively up-regulated in renal cell carcinoma (RCC) tissues. To examine the possible function of this molecule as a novel, broadly applicable TAA, synthetic full-length RGS1-mRNA was synthesized for the transfection of monocyte-derived dendritic cells (DCs). These modified antigen-presenting cells (APCs) were then used to induce RGS1-specific cytotoxic T cells (CTLs) in vitro. The CTLs generated from several healthy donors and a patient with chronic lymphocytic leukemia (CLL) elicited an antigen-specific and HLA-A2- and -A3-restricted cytolytic activity against tumor cells endogenously expressing the RGS1 protein including renal cell carcinomas (RCCs), melanoma, ovarian carcinoma and the primary autologous CLL-blasts. In conclusion, our study demonstrates that the in vitro induction of RGS1-specific CTLs by RNA-transfected DCs is feasible and highly effective. Since this molecule is (over-) expressed in a broad variety of malignancies it might represent an interesting novel TAA in the context of cancer vaccines designed to target RGS1 expressing tumor cells.

Strategic use of an adenoviral vector for rapid and efficient ex vivo-generation of cytomegalovirus pp65-reactive cytolytic and helper T cells

Cytomegalovirus (CMV) reactivation can cause severe complications for transplant patients. Such patients can be protected against CMV-associated diseases through reconstitution of donor-derived CMV-reactive cytolytic and helper T cells. We have developed a strategic protocol for efficient simultaneous generation of CMV-reactive CD8+ and CD4+ T cells ex vivo. The protocol uses peripheral blood lymphocytes (PBLs), antigen-modified mature dendritic cells (DCs) generated in only 3 d and an adenoviral vector encoding the CMV pp65 antigen (Adpp65) both as an endogenous and exogenous source of antigen. PBLs stimulated once with Adpp65-transduced DCs (endogenously expressed pp65) resulted in preferential activation and expansion of pp65-specific CD8+ T cells while PBLs stimulated with DCs pulsed with cell lysate from Adpp65-transduced autologous monocytes (exogenously expressed pp65) yielded pp65-specific CD4+ T cells. Stimulation with double-modified DCs efficiently activated and expanded cytolytic and helper T cells simultaneously. The frequency of T cells producing interferon-gamma in response to pp65 increased after one stimulation on average 9.6-fold to 4.3% for CD8+ T cells and 25.8-fold to 6.5% for CD4+ T cells. This implies that sufficient number of pp65-specific cytolytic and helper T cells for adoptive transfer may be obtained in only 2 weeks.

Simultaneous ex vivo quantification of antigen-specific CD4+ and CD8+ T cell responses using in vitro transcribed RNA

Assessment of antigen-specific T-cell responses has been greatly facilitated by development of ELISPOT and intracellular cytokine flow cytometry (CFC) assays. The use of autologous antigen presenting cells transfected with in vitro transcribed RNA as stimulators allows in principle quantification of antigen-specific T-cells independent of the knowledge of the epitopes. We describe here a cytokine secretion assay that enables simultaneous assessment of both antigen-specific CD4+ as well as CD8+ T-cells directly from clinical samples without the need for generation of dendritic cells. To this aim, bulk PBMCs were electroporated with RNA encoding the antigen fused to trafficking signal sequences derived from a MHC class I molecule and used as stimulators. With human cytomegalovirus (HCMV) phosphoprotein 65 (pp65) as antigen we show that for measuring ex vivo T-cell responses in ELISPOT and CFC such stimulators are superior or at least equivalent to a pool of overlapping peptides representing the entire pp65 sequence as well as to untagged pp65 encoding RNA. This approach avoids the time consuming generation of dendritic cells as immune stimulators and, in particular when used in the context of the CFC, is robust, broadly applicable and fast.

Identification and characterization of T-cell epitopes deduced from RGS5, a novel broadly expressed tumor antigen

PURPOSE

Identification of tumor-associated antigens and advances in tumor immunology resulted in the development of vaccination strategies to treat patients with malignant diseases. In a novel experimental approach that combined comparative mRNA expression analysis of defined cell types with the characterization of MHC ligands by mass spectrometry, we found that regulator of G protein signaling 5 (RGS5) is extensively up-regulated in a broad variety of malignant cells, and we identified two HLA-A2- and HLA-A3-binding peptides derived from the RGS5 protein. Interestingly, RGS5 was recently shown to be involved in tumor angiogenesis.

EXPERIMENTAL DESIGN

We used monocyte-derived dendritic cells pulsed with these novel antigenic peptides or transfected with RGS5-mRNA for the in vitro induction of CTLs, generated from healthy donors, to analyze the presentation of RGS5-deduced epitopes by malignant cells.

RESULTS

The generated CTL lines elicited an antigen-specific and HLA-restricted cytolytic activity against tumor cells endogenously expressing the RGS5 protein. Furthermore, we were able to induce RGS5-specific CTLs using peripheral blood mononuclear cells from a patient with acute myeloid leukemia capable of recognizing the autologous leukemic blasts while sparing nonmalignant cells.

CONCLUSIONS

These results indicate that the RGS5 peptides represent interesting candidates for the development of cancer vaccines designed to target malignant cells and tumor vessels.

hDectin-1 is involved in uptake and cross-presentation of cellular antigens

Human Dectin-1 (hDectin-1) is a member of the C-type lectin-like receptor family that was shown to be the major receptor for fungal beta-glucans and to play an important role in the cellular responses mediated by these carbohydrates. In this study, we demonstrate that hDectin-1 is involved in the uptake and cross-presentation of cellular antigens. Furthermore, activation of monocyte-derived dendritic cells (MDCs) with toll-like receptor 3 (TLR3) ligand but not with TLR2 ligand or TLR7 ligand resulted in down-regulation of hDectin-1 expression and reduced phagocytosis of apoptotic tumor cells as well as presentation of pp65-derived T-cell epitopes upon engulfment of cytomegalovirus (CMV)-infected human foreskin fibroblasts.

BCR-ABL Activity Is Critical for the Immunogenicity of Chronic Myelogenous Leukemia Cells

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder caused by excessive granulopoiesis due to the formation of the constitutively active tyrosine kinase BCR-ABL. An effective drug against CML is imatinib mesylate, a tyrosine kinase inhibitor acting on Abl kinases, c-KIT, and platelet-derived growth factor receptor. Recently, a study revealed that patients treated with imatinib showed impaired CTL responses compared with patients treated with IFN-alpha, which might be due to a treatment-induced reduction in immunogenicity of CML cells or immunosuppressive effects. In our study, we found that inhibition of BCR-ABL leads to a down-regulation of immunogenic antigens on the CML cells in response to imatinib treatment, which results in the inhibition of CML-directed immune responses. By treating CML cells with imatinib, we could show that the resulting inhibition of BCR-ABL leads to a decreased expression of tumor antigens, including survivin, adipophilin, hTERT, WT-1, Bcl-x(L), and Bcl-2 in correlation to a decreased development of CML-specific CTLs. In contrast, this reduction in immunogenicity was not observed when a CML cell line resistant to the inhibitory effects of imatinib was used, but could be confirmed by transfection with specific small interfering RNA against BCR-ABL or imatinib treatment of primary CML cells.

TLR ligands differentially affect uptake and presentation of cellular antigens

Dendritic cells (DCs) have the unique ability to efficiently present T-cell epitopes from exogenous antigens on MHC class I molecules, a process called cross-presentation. In our study we demonstrate that stimulation of monocyte-derived DCs with Toll-like receptor (TLR) ligands differentially affects the uptake and cross-presentation of cellular antigens. Activation of DCs with TLR3 or TLR4 but not with TLR2 or TLR7/8 ligands inhibited phagocytosis of apoptotic tumor cells and resulted in a reduced cross-presentation of pp65-derived T-cell epitopes on MHC class I molecules upon engulfment of cytomegalovirus (CMV)–infected fibroblasts. These results have an important impact on the understanding of the interactions between the immune system and pathogens and the development of vaccination strategies to treat malignant diseases.

MHC–peptide specificity and T-cell epitope mapping: where immunotherapy starts

The evaluation and characterization of epitope-specific human leukocyte antigen (HLA)-restricted memory T-cell reactivity is an important step for the development of preventive vaccines and peptide-based immunotherapies for viral and tumor diseases. The past decade has witnessed the use of HLA-restricted peptides as tools to activate strong immune responses of naïve or memory T cells specifically. This has fuelled an active search for methodological approaches focusing on HLA and peptide associations. Here, we outline new perspective on the emerging opportunity of evaluating HLA and peptide restriction by using novel approaches, such as quantitative real-time PCR, that can identify epitope specificities that are potentially useful in clinical settings.