Maturation pathways of dendritic cells determine TAP1 and TAP2 levels and cross-presenting function

Dendritic Cells: A Bridge between Tolerance Induction and Cancer Development in Transplantation Setting

Dendritic cells (DCs) are a heterogeneous group of antigen-presenting cells crucial for fostering allograft tolerance while simultaneously supporting host defense against infections and cancer. Within the tumor microenvironment, DCs can either mount an immune response against cancer cells or foster immunotolerance, presenting a dual role. In immunocompromised individuals, posttransplant malignancies pose a significant health concern, with DCs serving as vital players in immune responses against cancer cells. Both recipient- and donor-derived DCs play a critical role in the rejection process, infiltrating the transplanted organ and sustaining T-cell responses. The use of immunosuppressive drugs represents the predominant approach to control this immunological barrier in transplanted organs. Evidence has shed light on the immunopharmacology of these drugs and novel strategies for manipulating DCs to promote allograft survival. Therefore, comprehending the mechanisms underlying this intricate microenvironment and the effects of immunosuppressive therapy on DCs is crucial for developing targeted therapies to reduce graft failure rates. This review will delve into the fundamental immunobiology of DCs and provide a detailed exploration of their clinical significance concerning alloimmune responses and posttransplant malignancies.

Targeting the pericyte antigen DLK1 with an alpha type-1 polarized dendritic cell vaccine results in tumor vascular modulation and protection against colon cancer progression

Despite the availability of various treatment options, colorectal cancer (CRC) remains a significant contributor to cancer-related mortality. Current standard-of-care interventions, including surgery, chemotherapy, and targeted agents like immune checkpoint blockade and anti-angiogenic therapies, have improved short-term patient outcomes depending on disease stage, but survival rates with metastasis remain low. A promising strategy to enhance the clinical experience with CRC involves the use of dendritic cell (DC) vaccines that incite immunity against tumor-derived blood vessels, which are necessary for CRC growth and progression. In this report, we target tumor-derived pericytes expressing DLK1 with a clinically-relevant alpha type-1 polarized DC vaccine (αDC1) in a syngeneic mouse model of colorectal cancer. Our pre-clinical data demonstrate the αDC1 vaccine's ability to induce anti-tumor effects by facilitating cytotoxic T lymphocyte activity and ablating the tumor vasculature. This work, overall, provides a foundation to further interrogate immune-mediated mechanisms of protection in order to help devise efficacious αDC1-based strategies for patients with CRC.

Pathways of MHC I cross-presentation of exogenous antigens

Phagocytes, particularly dendritic cells (DCs), generate peptide-major histocompatibility complex (MHC) I complexes from antigens they have collected from cells in tissues and report this information to CD8 T cells in a process called cross-presentation. This process allows CD8 T cells to detect, respond and eliminate abnormal cells, such as cancers or cells infected with viruses or intracellular microbes. In some settings, cross-presentation can help tolerize CD8 T cells to self-antigens. One of the principal ways that DCs acquire tissue antigens is by ingesting this material through phagocytosis. The resulting phagosomes are key hubs in the cross-presentation (XPT) process and in fact experimentally conferring the ability to phagocytize antigens can be sufficient to allow non-professional antigen presenting cells (APCs) to cross-present. Once in phagosomes, exogenous antigens can be cross-presented (XPTed) through three distinct pathways. There is a vacuolar pathway in which peptides are generated and then bind to MHC I molecules within the confines of the vacuole. Ingested exogenous antigens can also be exported from phagosomes to the cytosol upon vesicular rupture and/or possibly transport. Once in the cytosol, the antigen is degraded by the proteasome and the resulting oligopeptides can be transported to MHC I molecule in the endoplasmic reticulum (ER) (a phagosome-to-cytosol (P2C) pathway) or in phagosomes (a phagosome-to-cytosol-to-phagosome (P2C2P) pathway). Here we review how phagosomes acquire the necessary molecular components that support these three mechanisms and the contribution of these pathways. We describe what is known as well as the gaps in our understanding of these processes.

The Early Immune Response of Lymphoid and Myeloid Head-Kidney Cells of Rainbow Trout (Oncorhynchus mykiss) Stimulated with Aeromonas salmonicida

The teleost head kidney is a highly relevant immune organ, and myeloid cells play a major role in this organ’s innate and adaptive immune responses. Because of their complexity, the early phases of the innate immune reaction of fish against bacteria are still poorly understood. In this study, naïve rainbow trout were stimulated with inactivated A. salmonicida and sampled at 12 h, 24 h and 7 d poststimulation. Cells from the head kidney were magnetically sorted with a monoclonal antibody mAB21 to obtain one (MAb21-positive) fraction enriched with myeloid cells and one (MAb21-negative) fraction enriched with lymphocytes and thrombocytes. The gene expression pattern of the resulting cell subpopulations was analysed using a panel of 43 immune-related genes. The results show an overall downregulation of the complement pathway and cytokine production at the considered time points. Some of the selected genes may be considered as parameters for diagnosing bacterial furunculosis of rainbow trout.

A single-cell map of intratumoral changes during anti-PD1 treatment of patients with breast cancer

Immune-checkpoint blockade (ICB) combined with neoadjuvant chemotherapy improves pathological complete response in breast cancer. To understand why only a subset of tumors respond to ICB, patients with hormone receptor-positive or triple-negative breast cancer were treated with anti-PD1 before surgery. Paired pre- versus on-treatment biopsies from treatment-naive patients receiving anti-PD1 (n = 29) or patients receiving neoadjuvant chemotherapy before anti-PD1 (n = 11) were subjected to single-cell transcriptome, T cell receptor and proteome profiling. One-third of tumors contained PD1-expressing T cells, which clonally expanded upon anti-PD1 treatment, irrespective of tumor subtype. Expansion mainly involved CD8⁺ T cells with pronounced expression of cytotoxic-activity (PRF1, GZMB), immune-cell homing (CXCL13) and exhaustion markers (HAVCR2, LAG3), and CD4⁺ T cells characterized by expression of T-helper-1 (IFNG) and follicular-helper (BCL6, CXCR5) markers. In pre-treatment biopsies, the relative frequency of immunoregulatory dendritic cells (PD-L1⁺), specific macrophage phenotypes (CCR2⁺ or MMP9⁺) and cancer cells exhibiting major histocompatibility complex class I/II expression correlated positively with T cell expansion. Conversely, undifferentiated pre-effector/memory T cells (TCF7⁺, GZMK⁺) or inhibitory macrophages (CX3CR1⁺, C3⁺) were inversely correlated with T cell expansion. Collectively, our data identify various immunophenotypes and associated gene sets that are positively or negatively correlated with T cell expansion following anti-PD1 treatment. We shed light on the heterogeneity in treatment response to anti-PD1 in breast cancer.

Evaluation of transduced dendritic cells expressing HIV-1 p24-Nef antigens in HIV-specific cytotoxic T cells induction as a therapeutic candidate vaccine

Various approaches have been investigated to prevent or eliminate HIV-1 since 1981. However, the virus has been affecting human population worldwide with no effective vaccine yet. The conserved regions among the viral genes are suitable targets in mutable viruses to induce the immune responses via an effective delivery platform. In this study, we aimed at evaluation of p24 and nef in two forms of full and truncated genes as two fusion antigenic forms according to our previous bioinformatics analysis. The designed antigens were then transferred through ex vivo generated dendritic cells and also proteins in BALB/c to assess and compare immunogenicity. p24 and Nef amino acid sequences were aligned, then, the most conserved regions were selected and two fusion forms as the truncated (p24:80-231aa-Nef:120-150aa) and the full from (p24-Nef) were cloned and expressed in prokaryotic and eukaryotic systems. Lentiviral vectors were applied to generate recombinant virions harboring the genes of interest to transduce generated murine dendritic cells. BALB/c mice received the recombinant DCs or recombinant proteins according to the defined schedule. IgG development was assessed to determine humoral immune activity and cellular immune responses were evaluated by IL-5 and IFN-y induction. Granzyme B secretion was also investigated to determine CTL activity in different immunized groups. The data showed high induction of cellular immune responses in dendritic cell immunization specifically in immunized mice with the truncated form of the p24 and Nef by high secretion of IFN-y and strong CTL activity. Moreover, protein/ DC prime-boost formulation led to stronger Th1 pathway and strong CTL activation in comparison with other formulations. The generated recombinant dendritic cells expressing p24-Nef induced humoral and cellular immunity in a Th1 pathway specifically with the in silico predicted truncated antigen which could be of high value as a dendritic cell therapeutic vaccine candidate against HIV-1.

Non-steroidal anti-inflammatory drugs induce immunogenic cell death in suppressing colorectal tumorigenesis

Use of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with reduced risk of colorectal cancer (CRC). However, the mechanism by which NSAIDs suppress colorectal tumorigenesis remains unclear. We previously showed that NSAIDs selectively kill emerging tumor cells via death receptor (DR) signaling and a synthetic lethal interaction mediated by the proapoptotic Bcl-2 family protein BID. In this study, we found NSAIDs induce endoplasmic reticulum (ER) stress to activate DR signaling and BID in tumor suppression. Importantly, our results unveiled an ER stress- and BID-dependent immunogenic effect of NSAIDs, which may be critical for tumor suppression. NSAID treatment induced hallmarks of immunogenic cell death (ICD) in CRC cells and colonic epithelial cells upon loss of APC tumor suppressor, and elevated tumor-infiltrating lymphocytes (TILs) in the polyps of APCMin/+ mice. ER stress inhibition or BID deletion abrogated the antitumor and immunogenic effects of NSAIDs. Furthermore, increased ER stress and TILs were detected in human advanced adenomas from NSAID-treated patients. Together, our results suggest that NSAIDs induce ER stress- and BID-mediated ICD to restore immunosurveillance and suppress colorectal tumor formation.

The Superior Ability of Human BDCA3+ (CD141+) Dendritic Cells (DCs) to Cross-Present Antigens Derived From Necrotic Lung Cancer Cells

Dendritic cells (DCs) play a key role in initiating and regulating the immune responses to pathogens, self-antigens, and cancers. Human blood DCs comprise a family of different subsets: plasmacytoid DCs (pDCs) and CD16⁺, CD1c/BDCA1⁺, and BDCA3⁺ (CD141⁺) myeloid DCs and possess different phenotypes and functional characteristics. Lung cancer is the most common cancer, with the highest morbidity and mortality in the world. However, which DC subset plays a leading role in the lung cancer immune responses is unclear. We reanalyzed C-type lectin domain family 9 member A (CLEC9A) and CD141 (THBD) gene expression profiles from the Cancer Genome Atlas (TCGA) database and performed the Kaplan-Meier survival analysis of overall survival for several cancers according to their expression levels. Next, we investigated the capacities of five human blood DC subsets to stimulate T cell proliferation and capture, process and (cross-) present tumor antigen. Human BDCA3⁺ (CD141⁺) DCs have a superior capacity to stimulate allogeneic CD4⁺T cells proliferation and induce superior Th1 response compared with other DC subsets. Interestingly, toll-like receptor (TLR) agonists have little effect on DCs to induce the proliferation of naïve CD4⁺ T cells, but contribute to their differentiation. Importantly, BDCA3⁺ (CD141⁺) DCs possess the most potent ability to cross-present human tumor antigen after their uptake of necrotic lung cancer cells despite their lower antigen uptake. These findings suggest that human BDCA3⁺ (CD141⁺) DCs are critical mediators of cytotoxic T lymphocyte responses against EGFR-positive lung cancer. Therefore, our findings may provide theoretical basis for the development of DC-based antitumor vaccines.

Role of Dendritic Cells in Exposing Latent HIV-1 for the Kill

The development of effective yet nontoxic strategies to target the latent human immunodeficiency virus-1 (HIV-1) reservoir in antiretroviral therapy (ART)-suppressed individuals poses a critical barrier to a functional cure. The ‘kick and kill’ approach to HIV eradication entails proviral reactivation during ART, coupled with generation of cytotoxic T lymphocytes (CTLs) or other immune effectors equipped to eliminate exposed infected cells. Pharmacological latency reversal agents (LRAs) that have produced modest reductions in the latent reservoir ex vivo have not impacted levels of proviral DNA in HIV-infected individuals. An optimal cure strategy incorporates methods that facilitate sufficient antigen exposure on reactivated cells following the induction of proviral gene expression, as well as the elimination of infected targets by either polyfunctional HIV-specific CTLs or other immune-based strategies. Although conventional dendritic cells (DCs) have been used extensively for the purpose of inducing antigen-specific CTL responses in HIV-1 clinical trials, their immunotherapeutic potential as cellular LRAs has been largely ignored. In this review, we discuss the challenges associated with current HIV-1 eradication strategies, as well as the unharnessed potential of ex vivo-programmed DCs for both the ‘kick and kill’ of latent HIV-1.

Distinguishing Features of Cetuximab and Panitumumab in Colorectal Cancer and Other Solid Tumors

Cetuximab and panitumumab are two distinct monoclonal antibodies (mAbs) targeting the epidermal growth factor receptor (EGFR), and both are widely used in combination with chemotherapy or as monotherapy to treat patients with RAS wild-type metastatic colorectal cancer. Although often considered interchangeable, the two antibodies have different molecular structures and can behave differently in clinically relevant ways. More specifically, as an immunoglobulin (Ig) G1 isotype mAb, cetuximab can elicit immune functions such as antibody-dependent cell-mediated cytotoxicity involving natural killer cells, T-cell recruitment to the tumor, and T-cell priming via dendritic cell maturation. Panitumumab, an IgG2 isotype mAb, does not possess these immune functions. Furthermore, the two antibodies have different binding sites on the EGFR, as evidenced by mutations on the extracellular domain that can confer resistance to one of the two therapeutics or to both. We consider a comparison of the properties of these two antibodies to represent a gap in the literature. We therefore compiled a detailed, evidence-based educational review of the known molecular, clinical, and functional differences between the two antibodies and concluded that they are distinct therapeutic agents that should be considered individually during treatment planning. Available data for one agent can only partly be extrapolated to the other. Looking to the future, the known immune activity of cetuximab may provide a rationale for this antibody as a combination partner with investigational chemotherapy plus immunotherapy regimens for colorectal cancer.

Arming Filamentous Bacteriophage, a Nature-Made Nanoparticle, for New Vaccine and Immunotherapeutic Strategies

The pharmaceutical use of bacteriophages as safe and inexpensive therapeutic tools is collecting renewed interest. The use of lytic phages to fight antibiotic-resistant bacterial strains is pursued in academic and industrial projects and is the object of several clinical trials. On the other hand, filamentous bacteriophages used for the phage display technology can also have diagnostic and therapeutic applications. Filamentous bacteriophages are nature-made nanoparticles useful for their size, the capability to enter blood vessels, and the capacity of high-density antigen expression. In the last decades, our laboratory focused its efforts in the study of antigen delivery strategies based on the filamentous bacteriophage 'fd', able to trigger all arms of the immune response, with particular emphasis on the ability of the MHC class I restricted antigenic determinants displayed on phages to induce strong and protective cytotoxic responses. We showed that fd bacteriophages, engineered to target mouse dendritic cells (DCs), activate innate and adaptive responses without the need of exogenous adjuvants, and more recently, we described the display of immunologically active lipids. In this review, we will provide an overview of the reported applications of the bacteriophage carriers and describe the advantages of exploiting this technology for delivery strategies.

Ilixadencel - an Allogeneic Cell-Based Anticancer Immune Primer for Intratumoral Administration

Intratumoral administration of an immune primer is a therapeutic vaccine strategy aimed to trigger dendritic cell (DC)-mediated cross-presentation of cell-associated tumor antigens to cytotoxic CD8+ T cells without the need for tumor antigen characterization. The prevailing view is that these cross-presenting DCs have to be directly activated by pathogen-associated molecular patterns (PAMPS), including Toll-like receptor ligands or live microbial agents like oncolytic viruses. Emerging data are however challenging this view, indicating that the cross-presenting machinery in DCs is suboptimally activated by direct PAMP recognition, and that endogenous inflammatory factors are the main drivers of DC-mediated cross-presentation within the tumor. Here we present preclinical mode of action data, CMC and regulatory data, as well as initial clinical data on ilixadencel. This cell-based drug product is an off-the-shelf immune primer, consisting of pro-inflammatory allogeneic DCs secreting high amounts of pro-inflammatory chemokines and cytokines at the time of intratumoral administration. The mechanism of action of ilixadencel is to induce recruitment and activation of endogenous immune cells, including NK cells that subsequently promotes cross-presentation of cell-associated tumor antigens by co-recruited DCs.

Targeted Therapies: Immunologic Effects and Potential Applications Outside of Cancer

Two pharmacologic approaches that are currently at the forefront of treating advanced cancer are those that center on disrupting critical growth/survival signaling pathways within tumor cells (commonly referred to as "targeted therapies") and those that center on enhancing the capacity of a patient's immune system to mount an antitumor response (immunotherapy). Maximizing responses to both of these approaches requires an understanding of the oncogenic events present in a given patient's tumor and the nature of the tumor-immune microenvironment. Although these 2 modalities were developed and initially used independently, combination regimens are now being tested in clinical trials, underscoring the need to understand how targeted therapies influence immunologic events. Translational studies and preclinical models have demonstrated that targeted therapies can influence immune cell trafficking, the production of and response to chemokines and cytokines, antigen presentation, and other processes relevant to antitumor immunity and immune homeostasis. Moreover, because these and other effects of targeted therapies occur in nonmalignant cells, targeted therapies are being evaluated for use in applications outside of oncology.

Nimotuzumab Induces NK Cell Activation, Cytotoxicity, Dendritic Cell Maturation and Expansion of EGFR-Specific T Cells in Head and Neck Cancer Patients

Survival benefit and long-term duration of clinical response have been seen using the epidermal growth factor receptor (EGFR)-targeted monoclonal antibody (mAb) nimotuzumab. Blocking EGFR signaling may not be the only mechanism of action underlying its efficacy. As an IgG1 isotype mAb, nimotuzumab's capacity of killing tumor cells by antibody dependent cellular cytotoxicity (ADCC) and to induce an immune response in cancer patients have not been studied. ADCC-induced by nimotuzumab was determined using a ⁵¹Cr release assay. The in vitro effect of nimotuzumab on natural killer (NK) cell activation and dendritic cell (DC) maturation and the in vivo frequency of circulating regulatory T cells (Tregs) and NK cells were assessed by flow cytometry. Cytokine levels in supernatants were determined by ELISA. ELISpot was carried out to quantify EGFR-specific T cells in nimotuzumab-treated head and neck cancer (HNSCC) patients. Nimotuzumab was able to kill EGFR+ tumor cells by NK cell-mediated ADCC. Nimotuzumab-activated NK cells promoted DC maturation and EGFR-specific CD8+ T cell priming. Interestingly, nimotuzumab led to upregulation of some immune checkpoint molecules on NK cells (TIM-3) and DC (PD-L1), to a lower extent than another EGFR mAb, cetuximab. Furthermore, circulating EGFR-specific T cells were identified in nimotuzumab-treated HNSCC patients. Notably, nimotuzumab combined with cisplatin-based chemotherapy and radiation increased the frequency of peripheral CD4+CD39+FOXP3+Tregs which otherwise were decreased to baseline values when nimotuzumab was used as monotherapy. The frequency of circulating NK cells remained constant during treatment. Nimotuzumab-induced, NK cell-mediated DC priming led to induction of anti-EGFR specific T cells in HNSCC patients. The association between EGFR-specific T cells and patient clinical benefit with nimotuzumab treatment should be investigated.

Increased PD-1+ and TIM-3+ TILs during Cetuximab Therapy Inversely Correlate with Response in Head and Neck Cancer Patients

Despite emerging appreciation for the important role of immune checkpoint receptors in regulating the effector functions of T cells, it is unknown whether their expression is involved in determining the clinical outcome in response to cetuximab therapy. We examined the expression patterns of immune checkpoint receptors (including PD-1, CTLA-4, and TIM-3) and cytolytic molecules (including granzyme B and perforin) of CD8⁺ tumor-infiltrating lymphocytes (TIL) and compared them with those of peripheral blood T lymphocytes (PBL) in patients with head and neck cancer (HNSCC) during cetuximab therapy. The frequency of PD-1 and TIM-3 expression was significantly increased in CD8⁺ TILs compared with CD8⁺ PBLs (P = 0.008 and P = 0.02, respectively). This increased CD8⁺ TIL population coexpressed granzyme B/perforin and PD-1/TIM-3, which suggests a regulatory role for these immune checkpoint receptors in cetuximab-promoting cytolytic activities of CD8⁺ TILs. Indeed, the increased frequency of PD-1⁺ and TIM-3⁺ CD8⁺ TILs was inversely correlated with clinical outcome of cetuximab therapy. These findings support the use of PD-1 and TIM-3 as biomarkers to reflect immune status of CD8⁺ T cells in the tumor microenvironment during cetuximab therapy. Blockade of these immune checkpoint receptors might enhance cetuximab-based cancer immunotherapy to reverse CD8⁺ TIL dysfunction, thus potentially improving clinical outcomes of HNSCC patients. Cancer Immunol Res; 5(5); 408-16. ©2017 AACR.

HLA class II antigen-processing pathway in tumors: Molecular defects and clinical relevance

The human leukocyte antigen (HLA) class II antigen-processing machinery (APM) presents to cognate CD4⁺ T-cells antigenic peptides mainly generated from exogeneous proteins in the endocytic compartment. These CD4⁺ T cells exert helper function, but may also act as effector cells, thereby recognizing HLA class II antigen-expressing tumor cells. Thus, HLA class II antigen expression by tumor cells influences the tumor antigen (TA)-specific immune responses and, depending on the cancer type, the clinical course of the disease. Many types of human cancers express HLA class II antigens, although with marked differences in their frequency. Some types of cancer lack HLA class II antigen expression, which could be due to structural defects or deregulation affecting different components of the complex HLA class II APM and/or from lack of cytokine(s) in the tumor microenvironment. In this review, we have summarized the information about HLA class II antigen distribution in normal tissues, the structural organization of the HLA class II APM, their expression and regulation in malignant cells, the defects, which have been identified in malignant cells, and their functional and clinical relevance.

CD137 Stimulation Enhances Cetuximab-Induced Natural Killer: Dendritic Cell Priming of Antitumor T-Cell Immunity in Patients with Head and Neck Cancer

PURPOSE

Cetuximab, an EGFR-specific antibody (mAb), modestly improves clinical outcome in patients with head and neck cancer (HNC). Cetuximab mediates natural killer (NK) cell:dendritic cell (DC) cross-talk by cross-linking FcγRIIIa, which is important for inducing antitumor cellular immunity. Cetuximab-activated NK cells upregulate the costimulatory receptor CD137 (4-1BB), which, when triggered by agonistic mAb urelumab, might enhance NK-cell functions, to promote T-cell-based immunity.

EXPERIMENTAL DESIGN

CD137 expression on tumor-infiltrating lymphocytes was evaluated in a prospective cetuximab neoadjuvant trial, and CD137 stimulation was evaluated in a phase Ib trial, in combining agonistic urelumab with cetuximab. Flow cytometry and cytokine release assays using NK cells and DC were used in vitro, testing the addition of urelumab to cetuximab-activated NK, DC, and cross presentation to T cells.

RESULTS

CD137 agonist mAb urelumab enhanced cetuximab-activated NK-cell survival, DC maturation, and tumor antigen cross-presentation. Urelumab boosted DC maturation markers, CD86 and HLA DR, and antigen-processing machinery (APM) components TAP1/2, leading to increased tumor antigen cross-presentation. In neoadjuvant cetuximab-treated patients with HNC, upregulation of CD137 by intratumoral, cetuximab-activated NK cells correlated with FcγRIIIa V/F polymorphism and predicted clinical response. Moreover, immune biomarker modulation was observed in an open label, phase Ib clinical trial, of patients with HNC treated with cetuximab plus urelumab.

CONCLUSIONS

These results suggest a beneficial effect of combination immunotherapy using cetuximab and CD137 agonist in HNC. Clin Cancer Res; 23(3); 707-16. ©2016 AACR.

Effective Cytotoxic T Lymphocyte Targeting of Persistent HIV-1 during Antiretroviral Therapy Requires Priming of Naive CD8+ T Cells

Curing HIV-1 infection will require elimination of persistent cellular reservoirs that harbor latent virus in the face of combination antiretroviral therapy (cART). Proposed immunotherapeutic strategies to cure HIV-1 infection include enhancing lysis of these infected cells by cytotoxic T lymphocytes (CTL). A major challenge in this strategy is overcoming viral immune escape variants that have evaded host immune control. Here we report that naive CD8⁺ T cells from chronic HIV-1-infected participants on long-term cART can be primed by dendritic cells (DC). These DC must be mature, produce high levels of interleukin 12p70 (IL-12p70), be responsive to CD40 ligand (CD40L), and be loaded with inactivated, autologous HIV-1. These DC-primed CD8⁺ T cell responders produced high levels of gamma interferon (IFN-γ) in response to a broad range of both conserved and variable regions of Gag and effectively killed CD4⁺ T cell targets that were either infected with the autologous latent reservoir-associated virus or loaded with autologous Gag peptides. In contrast, HIV-1-specific memory CD8⁺ T cells stimulated with autologous HIV-1-loaded DC produced IFN-γ in response to a narrow range of conserved and variable Gag peptides compared to the primed T cells and most notably, displayed significantly lower cytolytic function. Our findings highlight the need to selectively induce new HIV-1-specific CTL from naive precursors while avoiding activation of existing, dysfunctional memory T cells in potential curative immunotherapeutic strategies for HIV-1 infection.

Current immunotherapeutic approaches aim to enhance antiviral immunity against the HIV-1 reservoir; however, it has yet to be shown whether T cells from persons on cART can recognize and eliminate virus-infected cells. We show that in persons on cART a personalized medicine approach using their dendritic cells to stimulate their naive T cells induces potent effector CTL in vitro that recognize and eradicate HIV-1-infected CD4⁺ T cells. Additionally, we show that the same stimulation of existing memory T cells results in cytokine secretion but limited effector function. Our study demonstrates that the naive T cell repertoire can recognize persistent HIV-1 during cART and supports immunotherapy strategies for an HIV-1 cure that targets naive T cells, rather than existing, dysfunctional, memory T cells.

Impact of the Type I Interferon Receptor on the Global Gene Expression Program During the Course of Dendritic Cell Maturation Induced by Polyinosinic Polycytidylic Acid

Dendritic cell (DC) maturation involves widespread changes in cellular function and gene expression. The regulatory role of IFNAR in the program of DC maturation remains incompletely defined. Thus, the time evolution impact of IFNAR on this process was evaluated. Changes in DC phenotype, function, and gene expression induced by poly I:C were measured in wild-type and IFNAR(-/-) DC at 9 time points over 24 h. Temporal gene expression profiles were filtered on consistency and response magnitude across replicates. The number of genes whose expression was altered by poly I:C treatment was greatly reduced in IFNAR(-/-) DC, including the majority of the downregulated gene expression program previously observed in wild-type (WT) DC. Furthermore, the number of genes upregulated was almost equal between WT and IFNAR(-/-) DC, yet the identities of those genes were distinct. Integrating these data with protein-protein interaction data revealed several novel subnetworks active during maturation, including nucleotide synthesis, metabolism, and repair. A subnetwork associated with redox activity was uniquely identified in IFNAR(-/-) DC. Overall, temporal gene expression and network analyses identified many genes regulated by the type I interferon response and revealed previously unidentified aspects of the DC maturation process.

STAT1-Induced HLA Class I Upregulation Enhances Immunogenicity and Clinical Response to Anti-EGFR mAb Cetuximab Therapy in HNC Patients

The goal of this study was to characterize the molecular mechanisms underlying cetuximab-mediated upregulation of HLA class I antigen-processing machinery components in head and neck cancer (HNC) cells and to determine the clinical significance of these changes in cetuximab-treated HNC patients. Flow cytometry, signaling studies, and chromatin immunoprecipitation (ChIP) assays were performed using HNC cells treated with cetuximab alone or with Fcγ receptor (FcγR)-bearing lymphocytes to establish the mechanism of EGFR-dependent regulation of HLA APM expression. A prospective phase II clinical trial of neoadjuvant cetuximab was used to correlate HLA class I expression with clinical response in HNC patients. EGFR blockade triggered STAT1 activation and HLA upregulation, in a src homology-containing protein (SHP)-2-dependent fashion, more prominently in HLA-B/C than in HLA-A alleles. EGFR signaling blockade also enhanced IFNγ receptor 1 (IFNAR) expression, augmenting induction of HLA class I and TAP1/2 expression by IFNγ, which was abrogated in STAT1(-/-) cells. Cetuximab enhanced HNC cell recognition by EGFR853-861-specific CTLs, and notably enhanced surface presentation of a non-EGFR peptide (MAGE-3271-279). HLA class I upregulation was significantly associated with clinical response in cetuximab-treated HNC patients. EGFR induces HLA downregulation through SHP-2/STAT1 suppression. Reversal of HLA class I downregulation was more prominent in clinical responders to cetuximab therapy, supporting an important role for adaptive immunity in cetuximab antitumor activity. Abrogating EGFR-induced immune escape mechanisms and restoring STAT1 signaling to reverse HLA downregulation using cetuximab should be combined with strategies to enhance adaptive cellular immunity.

Therapeutic cancer vaccines and combination immunotherapies involving vaccination

Recent US Food and Drug Administration approvals of Provenge(®) (sipuleucel-T) as the first cell-based cancer therapeutic factor and ipilimumab (Yervoy(®)/anticytotoxic T-lymphocyte antigen-4) as the first "checkpoint blocker" highlight recent advances in cancer immunotherapy. Positive results of the clinical trials evaluating additional checkpoint blocking agents (blockade of programmed death [PD]-1, and its ligands, PD-1 ligand 1 and 2) and of several types of cancer vaccines suggest that cancer immunotherapy may soon enter the center stage of comprehensive cancer care, supplementing surgery, radiation, and chemotherapy. This review discusses the current status of the clinical evaluation of different classes of therapeutic cancer vaccines and possible avenues for future development, focusing on enhancing the magnitude and quality of cancer-specific immunity by either the functional reprogramming of patients' endogenous dendritic cells or the use of ex vivo-manipulated dendritic cells as autologous cellular transplants. This review further discusses the available strategies aimed at promoting the entry of vaccination-induced T-cells into tumor tissues and prolonging their local antitumor activity. Finally, the recent improvements to the above three modalities for cancer immunotherapy (inducing tumor-specific T-cells, prolonging their persistence and functionality, and enhancing tumor homing of effector T-cells) and rationale for their combined application in order to achieve clinically effective anticancer responses are addressed.

Tumor antigen-specific monoclonal antibodies and induction of T-cell immunity

For decades the primary available cancer therapies were relatively nonspecific cytotoxic agents which, while effective in some patients, were limited by narrow therapeutic indices, extensive toxicity and development of resistance, likely due to tumor heterogeneity. Although these chemotherapies remain common tools of conventional treatment, the approval of a growing number of tumor antigen (TA)-specific monoclonal antibodies (mAbs) by the US Food and Drug Administration has driven a shift in the paradigm of cancer therapy. For a subset of patients with lymphoma, colorectal, head and neck, and breast cancers, the inclusion of rituximab (anti-CD20), cetuximab (anti-human epidermal growth factor 1), and trastuzumab (anti-human epidermal growth factor 2) has resulted in overall improved clinical response rates and survival advantages. The mechanisms that contribute to these effects are limited not only to inhibition of signaling pathways but also include cell-mediated cytotoxicity by innate immune cells and priming of effector cells of adoptive immunity triggered by the TA-specific mAb. However, as the use of these therapeutic mAbs has become more widespread, it has been observed that there is significant variability of response in patients treated with these agents. Thus, the factors that mediate this variability in clinical responses must be elucidated to optimize the use of TA-specific mAbs.

Novel tumor antigen-specific monoclonal antibody-based immunotherapy to eradicate both differentiated cancer cells and cancer-initiating cells in solid tumors

A growing body of experimental and clinical evidence strongly suggests that the resistance of cancer-initiating cells (CICs) to conventional therapies represents a major obstacle to the successful treatment of a malignant disease. To overcome this limitation a novel combinatorial tumor antigen (TA)-specific monoclonal antibody (mAb) strategy has been developed. In this strategy TA-specific mAbs are combined with chemotherapeutic agents and/or small molecules that inhibit aberrantly activated signaling pathways in cancer cells and especially in CICs. The in vitro results we have obtained indicate that this strategy is very effective in eradicating both differentiated cancer cells and CICs in several types of malignant disease. If the in vitro results have in vivo relevance, the strategy we have designed may have an impact on the treatment of malignant diseases.

Phase I dendritic cell p53 peptide vaccine for head and neck cancer

BACKGROUND

p53 accumulation in head and neck squamous cell carcinoma (HNSCC) cells creates a targetable tumor antigen. Adjuvant dendritic cell (DC)-based vaccination against p53 was tested in a phase I clinical trial.

EXPERIMENTAL METHODS

Monocyte-derived DC from 16 patients were loaded with two modified HLA-class I p53 peptides (Arm 1), additional Th tetanus toxoid peptide (Arm 2), or additional Th wild-type (wt) p53-specific peptide (Arm 3). Vaccine DCs (vDC) were delivered to inguinal lymph nodes at three time points. vDC phenotype, circulating p53-specific T cells, and regulatory T cells (Treg) were serially monitored by flow cytometry and cytokine production by Luminex. vDC properties were compared with those of DC1 generated with an alternative maturation regimen.

RESULTS

No grade II-IV adverse events were observed. Two-year disease-free survival of 88% was favorable. p53-specific T-cell frequencies were increased postvaccination in 11 of 16 patients (69%), with IFN-γ secretion detected in four of 16 patients. Treg frequencies were consistently decreased (P = 0.006) relative to prevaccination values. The phenotype and function of DC1 were improved relative to vDC.

CONCLUSION

Adjuvant p53-specific vaccination of patients with HNSCC was safe and associated with promising clinical outcome, decreased Treg levels, and modest vaccine-specific immunity. HNSCC patients' DC required stronger maturation stimuli to reverse immune suppression and improve vaccine efficacy.

Intratumoral regulatory T cells upregulate immunosuppressive molecules in head and neck cancer patients

Background:

Although regulatory T cells (Treg) are highly enriched in human tumours compared with peripheral blood, expression of the immune-checkpoint receptors, immunosuppressive molecules and function of Treg in these two sites remains undefined.

Methods:

Tumour-infiltrating lymphocytes and peripheral blood lymphocytes were isolated from a cohort of head and neck squamous cell carcinoma (HNSCC) patients. The immunosuppressive phenotypes and function of intratumoral Treg were compared with those of peripheral blood Treg.

Results:

The frequency of immune-checkpoint receptor-positive cells was higher on intratumoral FOXP3⁺CD25^hi Treg compared with circulating Treg (CTLA-4, P=0.002; TIM-3, P=0.002 and PD-1, P=0.002). Immunosuppressive effector molecules, LAP and ectonucleotidase CD39 were also upregulated on intratumoral FOXP3⁺ Treg (P=0.002 and P=0.004, respectively). CTLA-4 and CD39 were co-expressed on the majority of intratumoral FOXP3⁺CD4⁺ Treg, suggesting that these molecules have a key role in regulatory functions of these cells in situ. Notably, intratumoral Treg exhibited more potently immunosuppressive activity than circulating Treg.

Conclusion:

These results indicate that intratumoral Treg are more immunosuppressive than circulating Treg and CTLA-4 and CD39 expressed can be potential target molecules to inhibit suppressive activities of intratumoral Treg in situ.

Dendritic cells in cancer immunotherapy: vaccines and combination immunotherapies

Dendritic cells (DCs) are specialized immunostimulatory cells involved in the induction and regulation of immune responses. The feasibility of large-scale ex vivo generation of DCs from patients' monocytes allows for therapeutic application of ex vivo-cultured DCs to bypass the dysfunction of endogenous DCs, restore immune surveillance, induce cancer regression or stabilization or delay or prevent its recurrence. While the most common paradigm of the therapeutic application of DCs reflects their use as cancer 'vaccines', additional and potentially more effective possibilities include the use of patients' autologous DCs as parts of more comprehensive therapies involving in vivo or ex vivo induction of tumor-reactive T cells and the measures to counteract systemic and local immunosuppression in tumor-bearing hosts. Ex vivo-cultured DCs can be instructed to acquire distinct functions relevant for the induction of effective cancer immunity (DC polarization), such as the induction of different effector functions or different homing properties of tumor-specific T cells (delivery of 'signal 3' and 'signal 4'). These considerations highlight the importance of the application of optimized conditions for the ex vivo culture of DCs and the potential combination of DC therapies with additional immune interventions to facilitate the entry of DC-induced T cells to tumor tissues and their local antitumor functions.

TLR3 agonists improve the immunostimulatory potential of cetuximab against EGFR+ head and neck cancer cells

Toll-like receptor 3 (TLR3) agonists have been extensively used as adjuvants for anticancer vaccines. However, their immunostimulatory effects and precise mechanisms of action in the presence of antineoplastic monoclonal antibodies (mAbs) have not yet been evaluated. We investigated the effect of TLR3 agonists on cetuximab-mediated antibody-dependent cellular cytotoxicity (ADCC) against head and neck cancer (HNC) cells, as well as on dendritic cell (DC) maturation and cross-priming of epidermal growth factor receptor (EGFR)-specific CD8⁺ T cells. The cytotoxic activity of peripheral blood mononuclear cells (PBMCs) or isolated natural killer (NK) cells expressing polymorphic variants (at codon 158) of the Fcγ receptor IIIa (FcγIIIa) was determined in ⁵¹Cr release assays upon incubation with the TLR3 agonist poly-ICLC. NK cell stimulation was measured based on activation and degranulation markers, while DC maturation in the presence of poly-ICLC was assessed using flow cytometry. The DC-mediated cross priming of EGFR-specific CD8⁺ T cells was monitored upon in vitro stimulation with tetramer-based flow cytometry. TLR3-stimulated, unfractionated PBMCs from HNC patients mediated robust cetuximab-dependent ADCC, which was abrogated by NK-cell depletion. The cytolytic activity of TLR3-stimulated NK cells differed among cells expressing different polymorphic variants of FcγRIIIa, and NK cells exposed to both poly-ICLC and cetuximab expressed higher levels of CD107a and granzyme B than their counterparts exposed to either stimulus alone. Poly-ICLC plus cetuximab also induced a robust upregulation of CD80, CD83 and CD86 on the surface of DCs, a process that was partially NK-cell dependent. Furthermore, DCs matured in these conditions exhibited improved cross-priming abilities, resulting in higher numbers of EGFR-specific CD8⁺ T cells. These findings suggest that TLR3 agonists may provide a convenient means to improve the efficacy of mAb-based anticancer regimens.

Cetuximab-activated natural killer and dendritic cells collaborate to trigger tumor antigen-specific T-cell immunity in head and neck cancer patients

PURPOSE

Tumor antigen-specific monoclonal antibodies (mAb) block oncogenic signaling and induce Fcγ receptor (FcγR)-mediated cytotoxicity. However, the role of CD8(+) CTL and FcγR in initiating innate and adaptive immune responses in mAb-treated human patients with cancer is still emerging.

EXPERIMENTAL DESIGN

FcγRIIIa codon 158 polymorphism was correlated with survival in 107 cetuximab-treated patients with head and neck cancer (HNC). Flow cytometry was carried out to quantify EGF receptor (EGFR)-specific T cells in cetuximab-treated patients with HNC. The effect of cetuximab on natural killer (NK) cell, dendritic cell (DC), and T-cell activation was measured using IFN-γ release assays and flow cytometry.

RESULTS

FcγRIIIa polymorphism did not predict clinical outcome in cetuximab-treated patients with HNC; however, elevated circulating EGFR(853-861)-specific CD8(+) T cells were found in cetuximab-treated patients with HNC (P < 0.005). Cetuximab promoted EGFR-specific cellular immunity through the interaction of EGFR(+) tumor cells and FcγRIIIa on NK cells but not on the polymorphism per se. Cetuximab-activated NK cells induced IFN-γ-dependent expression of DC maturation markers, antigen processing machinery components such as TAP-1/2 and T-helper cell (T(H)1) chemokines through NKG2D/MICA binding. Cetuximab initiated adaptive immune responses via NK cell-induced DC maturation, which enhanced cross-presentation to CTL specific for EGFR as well as another tumor antigen, MAGE-3.

CONCLUSION

Cetuximab-activated NK cells promote DC maturation and CD8(+) T-cell priming, leading to tumor antigen spreading and TH1 cytokine release through "NK-DC cross-talk." FcγRIIIa polymorphism did not predict clinical response to cetuximab but was necessary for NK-DC interaction and mAb-induced cross-presentation. EGFR-specific T cells in cetuximab-treated patients with HNC may contribute to clinical response.

IRX-2, a novel immunotherapeutic, enhances functions of human dendritic cells

Background

In a recent phase II clinical trial for HNSCC patients, IRX-2, a cell-derived biologic, promoted T-cell infiltration into the tumor and prolonged overall survival. Mechanisms responsible for these IRX-2-mediated effects are unknown. We hypothesized that IRX-2 enhanced tumor antigen-(TA)-specific immunity by up-regulating functions of dendritic cells (DC).

Methodology/Principal Findings

Monocyte-derived DC obtained from 18 HNSCC patients and 12 healthy donors were matured using IRX-2 or a mix of TNF-α, IL-1β and IL-6 (“conv. mix”). Multicolor flow cytometry was used to study the DC phenotype and antigen processing machinery (APM) component expression. ELISPOT and cytotoxicity assays were used to evaluate tumor-reactive cytotoxic T lymphocytes (CTL). IL-12p70 and IL-10 production by DC was measured by Luminex® and DC migration toward CCL21 was tested in transwell migration assays. IRX-2-matured DC functions were compared with those of conv. mix-matured DC. IRX-2-matured DC expressed higher levels (p<0.05) of CD11c, CD40, CCR7 as well as LMP2, TAP1, TAP2 and tapasin than conv. mix-matured DC. IRX-2-matured DC migrated significantly better towards CCL21, produced more IL-12p70 and had a higher IL12p70/IL-10 ratio than conv. mix-matured DC (p<0.05 for all). IRX-2-matured DC carried a higher density of tumor antigen-derived peptides, and CTL primed with these DC mediated higher cytotoxicity against tumor targets (p<0.05) compared to the conv. mix-matured DC.

Conclusion

Excellent ability of IRX-2 to induce ex vivo DC maturation in HNSCC patients explains, in part, its clinical benefits and emphasizes its utility in ex vivo maturation of DC generated for therapy.

Immunotherapy of cancer in 2012

The immunotherapy of cancer has made significant strides in the past few years due to improved understanding of the underlying principles of tumor biology and immunology. These principles have been critical in the development of immunotherapy in the laboratory and in the implementation of immunotherapy in the clinic. This improved understanding of immunotherapy, enhanced by increased insights into the mechanism of tumor immune response and its evasion by tumors, now permits manipulation of this interaction and elucidates the therapeutic role of immunity in cancer. Also important, this improved understanding of immunotherapy and the mechanisms underlying immunity in cancer has fueled an expanding array of new therapeutic agents for a variety of cancers. Pegylated interferon-α2b as an adjuvant therapy and ipilimumab as therapy for advanced disease, both of which were approved by the United States Food and Drug Administration for melanoma in March 2011, are 2 prime examples of how an increased understanding of the principles of tumor biology and immunology have been translated successfully from the laboratory to the clinical setting. Principles that guide the development and application of immunotherapy include antibodies, cytokines, vaccines, and cellular therapies. The identification and further elucidation of the role of immunotherapy in different tumor types, and the development of strategies for combining immunotherapy with cytotoxic and molecularly targeted agents for future multimodal therapy for cancer will enable even greater progress and ultimately lead to improved outcomes for patients receiving cancer immunotherapy.

Natural killer (NK): dendritic cell (DC) cross talk induced by therapeutic monoclonal antibody triggers tumor antigen-specific T cell immunity

Tumor antigen (TA)-targeted monoclonal antibodies (mAb), trastuzumab, cetuximab, panitumumab, and rituximab, have been among the most successful new therapies in the present generation. Clinical activity is observed as a single agent, or in combination with radiotherapy or chemotherapy, against metastatic colorectal cancer, head and neck cancer, breast cancer, and follicular lymphoma. However, the activity is seen only in a minority of patients. Thus, an intense need exists to define the mechanism of action of these immunoactive mAb. Here, we discuss some of the likely immunological events that occur in treated patients: antibody-dependent cellular cytotoxicity (ADCC), cross talk among immune cells including NK cells and dendritic cells (DCs), and generation of TA-specific T lymphocyte responses. We present evidence supporting the induction of "NK:DC cross talk," leading to priming of TA-specific cellular immunity. These observations show that mAb-mediated NK cell activation can be greatly enhanced by the action of stimulatory cytokines and surface molecules on maturing DC and that NK:DC interaction facilitates the recruitment of both NK cells and DC to the tumor site(s). The cooperative, reciprocal stimulatory activity of both NK cells and DC can modulate both the innate immune response in the local tumor microenvironment and the adaptive immune response in secondary lymphoid organs. These events likely contribute to clinical activity, as well as provide a potential biomarker of response to mAb therapy.

Dendritic cells in cancer immunotherapy: vaccines or autologous transplants?

Dendritic cells (DCs) are the most powerful immunostimulatory cells specialized in the induction and regulation of immune responses. Their properties and the feasibility of their large-scale ex vivo generation led to the application of ex vivo-educated DCs to bypass the dysfunction of endogenous DCs in cancer patients and to induce therapeutic anti-cancer immunity. While multiple paradigms of therapeutic application of DCs reflect their consideration as cancer "vaccines", numerous features of DC-based vaccination resemble those of autologous transplants, resulting in challenges and opportunities that distinguish them from classical vaccines. In addition to the functional heterogeneity of DC subsets and plasticity of the individual DC types, the unique features of DCs are the kinetic character of their function, limited functional stability, and the possibility to imprint in maturing DCs distinct functions relevant for the induction of effective cancer immunity, such as the induction of different effector functions or different homing properties of tumor-specific T cells (delivery of "signal 3" and "signal 4"). These considerations highlight the importance of the application of optimized, potentially patient-specific conditions of ex vivo culture of DCs and their delivery, with the logistic and regulatory implications shared with transplantation and other surgical procedures.

Serum antibodies critically affect virus-specific CD4+/CD8+ T cell balance during respiratory syncytial virus infections

Following infection with respiratory syncytial virus (RSV), reinfection in healthy individuals is common and presumably due to ineffective memory T cell responses. In peripheral blood of healthy adults, a higher CD4(+)/CD8(+) memory T cell ratio was observed compared with the ratio of virus-specific effector CD4(+)/CD8(+) T cells that we had found in earlier work during primary RSV infections. In mice, we show that an enhanced ratio of RSV-specific neutralizing to nonneutralizing Abs profoundly enhanced the CD4(+) T cell response during RSV infection. Moreover, FcγRs and complement factor C1q contributed to this Ab-mediated enhancement. Therefore, the increase in CD4(+) memory T cell response likely occurs through enhanced endosomal Ag processing dependent on FcγRs. The resulting shift in memory T cell response was likely amplified by suppressed T cell proliferation caused by RSV infection of APCs, a route important for Ag presentation via MHC class I molecules leading to CD8(+) T cell activation. Decreasing memory CD8(+) T cell numbers could explain the inadequate immunity during repeated RSV infections. Understanding this interplay of Ab-mediated CD4(+) memory T cell response enhancement and infection mediated CD8(+) memory T cell suppression is likely critical for development of effective RSV vaccines.

Tumor antigen-targeted, monoclonal antibody-based immunotherapy: clinical response, cellular immunity, and immunoescape

PURPOSE

Tumor antigen (TA) -targeted monoclonal antibodies (mAb), rituximab, trastuzumab, and cetuximab, are clinically effective for some advanced malignancies, especially in conjunction with chemotherapy and/or radiotherapy. However, these results are only seen in a subset (20% to 30%) of patients. We discuss the immunologic mechanism(s) underlying these clinical findings and their potential role in the variability in patients' clinical response.

METHODS

We reviewed the evidence indicating that the effects of TA-targeted mAb-based immunotherapy are mediated not only by inhibition of signaling pathways, but also by cell-mediated cytotoxicity triggered by the infused TA-targeted mAb. We analyzed the immunologic variables that can influence the outcome of antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro and in animal model systems. We also analyzed the correlation reported between these variables and the clinical response to mAb-based immunotherapy.

RESULTS

Of the variables that influence ADCC mediated by TA-targeted mAb, only polymorphisms of Fcγ receptors (FcγR) expressed by patients' lymphocytes were correlated with clinical efficacy. However, this correlation is not absolute and is not observed in all malignancies. Thus other variables may be responsible for the antitumor effects seen in mAb-treated patients. We discuss the evidence that triggering of TA-specific cellular immunity by TA-targeted mAb, in conjunction with immune escape mechanisms used by tumor cells, may contribute to the differential clinical responses to mAb-based immunotherapy.

CONCLUSION

Identification of the mechanism(s) underlying the clinical response of patients with cancer treated with TA-targeted mAb is crucial to optimizing their application in the clinic and to selecting the patients most likely to benefit from their use.

Dendritic cells reveal a broad range of MHC class I epitopes for HIV-1 in persons with suppressed viral load on antiretroviral therapy

Background

HIV-1 remains sequestered during antiretroviral therapy (ART) and can resume high-level replication upon cessation of ART or development of drug resistance. Reactivity of memory CD8⁺ T lymphocytes to HIV-1 could potentially inhibit this residual viral replication, but is largely muted by ART in relation to suppression of viral antigen burden. Dendritic cells (DC) are important for MHC class I processing and presentation of peptide epitopes to memory CD8⁺ T cells, and could potentially be targeted to activate memory CD8⁺ T cells to a broad array of HIV-1 epitopes during ART.

Principal Findings

We show for the first time that HIV-1 peptide-loaded, CD40L-matured DC from HIV-1 infected persons on ART induce IFN gamma production by CD8⁺ T cells specific for a much broader range and magnitude of Gag and Nef epitopes than do peptides without DC. The DC also reveal novel, MHC class I restricted, Gag and Nef epitopes that are able to induce polyfunctional T cells producing various combinations of IFN gamma, interleukin 2, tumor necrosis factor alpha, macrophage inhibitory protein 1 beta and the cytotoxic de-granulation molecule CD107a.

Significance

There is an underlying, broad antigenic spectrum of anti-HIV-1, memory CD8⁺ T cell reactivity in persons on ART that is revealed by DC. This supports the use of DC-based immunotherapy for HIV-1 infection.

Polarized dendritic cells as cancer vaccines: directing effector-type T cells to tumors

Ex vivo generation and antigen loading of dendritic cells (DCs) from cancer patients helps to bypass the dysfunction of endogenous DCs. It also allows to control the process of DC maturation and to imprint in maturing DCs several functions essential for induction of effective forms of cancer immunity. Recent reports from several groups including ours demonstrate that distinct conditions of DC generation and maturation can prime DCs for preferential interaction with different (effector versus regulatory) subsets of immune cells. Moreover, differentially-generated DCs have been shown to imprint different effector mechanisms in CD4(+) and CD8(+) T cells (delivery of "signal three") and to induce their different homing properties (delivery of "signal four"). These developments allow for selective induction of tumor-specific T cells with desirable effector functions and tumor-relevant homing properties and to direct the desirable types of immune cells to tumors.