Cross-priming in health and disease

Predicting pathway cross-talks in ankylosing spondylitis through investigating the interactions among pathways

Given that the pathogenesis of ankylosing spondylitis (AS) remains unclear, the aim of this study was to detect the potentially functional pathway cross-talk in AS to further reveal the pathogenesis of this disease. Using microarray profile of AS and biological pathways as study objects, Monte Carlo cross-validation method was used to identify the significant pathway cross-talks. In the process of Monte Carlo cross-validation, all steps were iterated 50 times. For each run, detection of differentially expressed genes (DEGs) between two groups was conducted. The extraction of the potential disrupted pathways enriched by DEGs was then implemented. Subsequently, we established a discriminating score (DS) for each pathway pair according to the distribution of gene expression levels. After that, we utilized random forest (RF) classification model to screen out the top 10 paired pathways with the highest area under the curve (AUCs), which was computed using 10-fold cross-validation approach. After 50 bootstrap, the best pairs of pathways were identified. According to their AUC values, the pair of pathways, antigen presentation pathway and fMLP signaling in neutrophils, achieved the best AUC value of 1.000, which indicated that this pathway cross-talk could distinguish AS patients from normal subjects. Moreover, the paired pathways of SAPK/JNK signaling and mitochondrial dysfunction were involved in 5 bootstraps. Two paired pathways (antigen presentation pathway and fMLP signaling in neutrophil, as well as SAPK/JNK signaling and mitochondrial dysfunction) can accurately distinguish AS and control samples. These paired pathways may be helpful to identify patients with AS for early intervention.

Macavirus latency-associated protein evades immune detection through regulation of protein synthesis in cis depending upon its glycin/glutamate-rich domain

Alcelaphine herpesvirus 1 (AlHV-1) is a γ-herpesvirus (γ-HV) belonging to the macavirus genus that persistently infects its natural host, the wildebeest, without inducing any clinical sign. However, cross-transmission to other ruminant species causes a deadly lymphoproliferative disease named malignant catarrhal fever (MCF). AlHV-1 ORF73 encodes the latency-associated nuclear antigen (LANA)-homolog protein (aLANA). Recently, aLANA has been shown to be essential for viral persistence in vivo and induction of MCF, suggesting that aLANA shares key properties of other γ-HV genome maintenance proteins. Here we have investigated the evasion of the immune response by aLANA. We found that a glycin/glutamate (GE)-rich repeat domain was sufficient to inhibit in cis the presentation of an epitope linked to aLANA. Although antigen presentation in absence of GE was dependent upon proteasomal degradation of aLANA, a lack of GE did not affect protein turnover. However, protein self-synthesis de novo was downregulated by aLANA GE, a mechanism directly associated with reduced antigen presentation in vitro. Importantly, codon-modification of aLANA GE resulted in increased antigen presentation in vitro and enhanced induction of antigen-specific CD8+ T cell responses in vivo, indicating that mRNA constraints in GE rather than peptidic sequence are responsible for cis-limitation of antigen presentation. Nonetheless, GE-mediated limitation of antigen presentation in cis of aLANA was dispensable during MCF as rabbits developed the disease after virus infection irrespective of the expression of full-length or GE-deficient aLANA. Altogether, we provide evidence that inhibition in cis of protein synthesis through GE is likely involved in long-term immune evasion of AlHV-1 latent persistence in the wildebeest natural host, but dispensable in MCF pathogenesis.

Herpes simplex virus 1 interferes with autophagy of murine dendritic cells and impairs their ability to stimulate CD8+ T lymphocytes

The MHC class I presentation is responsible for the presentation of viral proteins to CD8⁺ T lymphocytes and mainly depends on the classical antigen processing pathway. Recently, a second pathway involving autophagy has been implicated in this process. Here, we show an increase in the capacity of murine dendritic cells (DCs) to present viral antigens on MHC class I after infection with a mutant herpes simplex virus 1 (HSV-1-Δ34.5), lacking infected cell protein 34.5 (ICP34.5), when compared to its parental HSV-1 strain. The ICP34.5 protein counteracts host cell translational arrest and suppresses macroautophagy, and the lack of this protein resulted in a low viral protein abundance, which was processed and presented in an efficient way. Our study demonstrates an important role of autophagy in processing endogenous viral proteins in HSV-1-infected DCs.

Novel Checkpoints and Cosignaling Molecules in Cancer Immunotherapy

The recent demonstration of the antitumor efficacy of checkpoint protein inhibition has resulted in the approval of blocking antibodies against the programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway in multiple different histologic findings. Therapeutic successes with PD-1/PD-L1 antibodies in melanoma and lung cancer have been followed by approvals in bladder, renal, and head and neck cancers and Hodgkin lymphoma, with others undoubtedly to come. However, PD-1 is only one of many checkpoints and agonistic regulatory molecules expressed on T cells by which maintenance of the balance between costimulatory and coinhibitory signaling pathways is perturbed in cancer. The manipulation of many of these molecules in cancer patients might be associated with clinical benefit. The majority of the T-cell cosignaling receptors belong to either the immunoglobulin superfamily or the tumor necrosis factor receptor superfamily. A total of 29 immunoglobulin superfamily and 26 tumor necrosis factor receptor superfamily cosignaling receptors have been identified that are expressed on T cells, providing fertile ground for development of inhibitory or agonistic antibodies and small molecules as cancer therapeutics. In the current work, we focus on some of the most promising new checkpoints and agonistic or cosignaling molecules that are in early clinical development as single agents or in combinations with PD-1/PD-L1, cytotoxic T-lymphocyte-associated protein 4 blockade, or chemotherapy with an emphasis on those that have reached the clinic and on important targets that are in late preclinical development.

iTRAQ-based quantitative proteomic analysis reveals Bai-Hu-Tang enhances phagocytosis and cross-presentation against LPS fever in rabbit

ETHNOPHARMACOLOGICAL RELEVANCE

Bai-Hu-Tang (BHT), a classical anti-febrile Chinese formula comprising of liquorice, anemarrhena rhizome, gypsum and rice, has been traditionally used to anti-febrile treatment and promote the production of body fluid to relieve thirst. In this paper, we aim to explore anti-febrile mechanism of BHT at protein level through analyzing alteration of differentially expressed proteins (DEPs) both lipopolysaccharide (LPS) fever syndrome and that was treated with BHT in rabbits.

MATERIALS AND METHODS

Febrile model was induced by LPS injection (i.v.) in rabbits, and BHT (750mg dry extract/kg body weight) was gavaged to another group of LPS fever rabbits. After sacrifice of animals, total protein of liver tissue was isolated, and two-dimensional liquid chromatography (LC) - tandem mass spectrometry (MS) coupled with isobaric tags for relative and absolute quantification (iTRAQ) labeling analysis was employed to quantitatively identify differentially expressed proteins in two group animals, which were compared with control group. Then bioinformatic analysis of DEPs was conducted through hierarchical Clustering, Venn analysis, gene ontology (GO) annotation enrichment, and kyoto encyclopedia of genes and genomes (KEGG) pathways enrichment.

RESULT

The results demonstrated there were 63 and 109 DEPs in LPS fever group and BHT-treated group, respectively. Enrichment analysis of GO annotations indicated that BHT mainly regulated expression of some extracellular structural proteins for response to stimulus and stress. KEGG analysis showed that ribosome and phagosome were the most significant pathways. Thereinto, several proteins in phagosome pathway were significantly up-regulated by BHT, including F-actin, coronin, Rac, and major histocompatibility complex class I (MHC I), which work in phagocytosis and cross-presentation CONCLUSION: BHT may contribute to pyrogen clearance by boosting antigenic phagocytosis, degradation, and cross presentation in the liver.

The comings and goings of MHC class I molecules herald a new dawn in cross-presentation

MHC class I (MHC-I) molecules are the centerpieces of cross-presentation. They are loaded with peptides derived from exogenous sources and displayed on the plasma membrane to communicate with CD8 T cells, relaying a message of tolerance or attack. The study of cross-presentation has been focused on the relative contributions of the vacuolar versus cytosolic pathways of antigen processing and the location where MHC-I molecules are loaded. While vacuolar processing generates peptides loaded onto vacuolar MHC-I molecules, how and where exogenous peptides generated by the proteasome and transported by TAP meet MHC-I molecules for loading has been a matter of debate. The source and trafficking of MHC-I molecules in dendritic cells have largely been ignored under the expectation that these molecules came from the Endoplasmic reticulum (ER) or the plasma membrane. New studies reveal a concentrated pool of MHC-I molecules in the endocytic recycling compartment (ERC). These pools are rapidly mobilized to phagosomes carrying microbial antigens, and in a signal-dependent manner under the control of Toll-like receptors. The phagosome becomes a dynamic hub receiving traffic from multiple sources, the ER-Golgi intermediate compartment for delivering the peptide-loading machinery and the ERC for deploying MHC-I molecules that alert CD8 T cells of infection.

Intracellular recycling and cross-presentation by MHC class I molecules

Cross-presentation of internalized antigens by dendritic cells requires efficient delivery of Major Histocompatibility Complex (MHC) class I molecules to peptide-loading compartments. Strong evidence suggests that such loading can occur outside of the endoplasmic reticulum; however, the trafficking pathways and sources of class I molecules involved are poorly understood. Examination of non-professional, non-phagocytic cells has revealed a clathrin-independent, Arf6-dependent recycling pathway likely traveled by internalized optimally loaded (closed) class I molecules. Some closed and all open MHC class I molecules travel to late endosomes to be degraded but might also partly be re-loaded with peptides and recycled. Studies of viral interference revealed pathways in which class I molecules are directed to degradation in lysosomes upon ubiquitination at the surface, or upon AP-1 and HIV-nef-dependent misrouting from the Golgi network to lysosomes. While many observations made in non-professional cells remain to be re-examined in dendritic cells, available evidence suggests that both recycling and neo-synthesized class I molecules can be loaded with cross-presented peptides. Recycling molecules can be recruited to phagosomes triggered by innate signals such as TLR4 ligands, and may therefore specialize in loading with phagocytosed antigens. In contrast, AP-1-dependent accumulation at, or trafficking through, a Golgi compartment of newly synthesized molecules appears to be important for cross-presentation of soluble proteins and possibly of long peptides that are processed in the so-called vacuolar pathway. However, significant cell biological work will be required to confirm this or any other model and to integrate knowledge on MHC class I biochemistry and trafficking in models of CD8(+) T-cell priming by dendritic cells.

Pulmonary immunity to viruses

Mucosal surfaces, such as the respiratory epithelium, are directly exposed to the external environment and therefore, are highly susceptible to viral infection. As a result, the respiratory tract has evolved a variety of innate and adaptive immune defenses in order to prevent viral infection or promote the rapid destruction of infected cells and facilitate the clearance of the infecting virus. Successful adaptive immune responses often lead to a functional state of immune memory, in which memory lymphocytes and circulating antibodies entirely prevent or lessen the severity of subsequent infections with the same virus. This is also the goal of vaccination, although it is difficult to vaccinate in a way that mimics respiratory infection. Consequently, some vaccines lead to robust systemic immune responses, but relatively poor mucosal immune responses that protect the respiratory tract. In addition, adaptive immunity is not without its drawbacks, as overly robust inflammatory responses may lead to lung damage and impair gas exchange or exacerbate other conditions, such as asthma or chronic obstructive pulmonary disease (COPD). Thus, immune responses to respiratory viral infections must be strong enough to eliminate infection, but also have mechanisms to limit damage and promote tissue repair in order to maintain pulmonary homeostasis. Here, we will discuss the components of the adaptive immune system that defend the host against respiratory viral infections.

A comparative analysis between proteasome and immunoproteasome inhibition in cellular and humoral alloimmunity

Triggered by the successful administration of the proteasome inhibitor bortezomib in kidney transplant recipients with acute or chronic antibody-mediated rejection, we evaluated the effect of the proteasome inhibitor CEP-18770 and of the selective immunoproteasome inhibitor ONX-0914 on cellular and humoral alloimmunity. Cellular alloimmunity was assessed by cell proliferation in a two-way mixed lymphocyte reaction (MLR) with human peripheral blood mononuclear cells (PBMC). For assessing humoral alloimmunity we developed a method, where humoral alloimmunity was induced in one-way MLR. The de novo production of alloantibodies was measured with an antibody-mediated complement-dependent cytotoxicity assay, in which supernatants from the above MLRs were used against resting PBMC similar to the stimulator cells of the forementioned MLRs. In two-way MLRs ONX-0914 inhibited cell proliferation more than CEP-18770. In one-way MLRs CEP-18770 and ONX-0194 decreased alloantibody production to the same extent. Inhibition of the immunoproteasome is superior to inhibition of the proteasome in suppressing cellular alloimmunity, and equally effective as regards to humoral alloimmunity. Considering the selective expression of the immunoproteasome in immune cells and the expected restrictive toxicity of its inhibitors, these results render immunoproteasome an excellent target for the development of new immunosuppressive medications in the field of transplantation.

Targeting myeloid derived suppressor cells with all-trans retinoic acid is highly time-dependent in therapeutic tumor vaccination

Tumor immune escape is a critical problem which frequently accounts for the failure of therapeutic tumor vaccines. Among the most potent suppressors of tumor immunity are myeloid derived suppressor cells (MDSCs). MDSCs can be targeted by all-trans-retinoic-acid (atRA), which reduced their numbers and increased response rates in several vaccination studies. However, not much is known about the optimal administration interval between atRA and the vaccine as well as about its mode of action. Here we demonstrate in 2 different murine tumor models that mice unresponsive to a therapeutic vaccine harbored higher MDSC numbers than did responders. Application of atRA overcame MDSC-mediated immunosuppression and restored tumor control. Importantly, atRA was protective only when administered 3 d after vaccination (delayed treatment), whereas simultaneous administration even decreased the anti-tumor immune response and reduced survival. When analyzing the underlying mechanisms, we found that delayed, but not simultaneous atRA treatment with vaccination abrogated the suppressive capacity in monocytic MDSCs and instead caused them to upregulate MHC-class-II. Consistently, MDSCs from patients with colorectal carcinoma also failed to upregulate HLA-DR after ex vivo treatment with TLR-ligation. Overall, we demonstrate that atRA can convert non-responders to responders to vaccination by suppressing MDSCs function and not only by reducing their number. Moreover, we identify a novel, strictly time-dependent mode of action of atRA to be considered during immunotherapeutic protocols in the future.

Converting Lymphoma Cells into Potent Antigen-Presenting Cells for Interferon-Induced Tumor Regression

Anti-hCD20 is a therapeutic mAb that is clinically used to treat B-cell lymphoma. Some lymphomas are resistant to anti-hCD20; others relapse after treatment with anti-hCD20. Using a syngeneic immunocompetent mouse model, we observed that targeting lymphoma with interferon-α (IFNα) abolished resistance of B-cell lymphoma to anti-CD20 while limiting interferon (IFN)-associated systemic toxicity in the host. Control of tumors by a fusion of anti-CD20 and IFNα (anti-CD20-IFNα) depended on existing tumor-infiltrating CD8⁺ T cells. Although lymphomas were resistant to IFN-directed killing, IFN-exposed tumor cells became the dominant antigen-presenting cells (APC) for the reactivation of tumor-infiltrating CD8⁺ T cells that then controlled those lymphomas. Anti-CD20-IFNα also abolished checkpoint blockade resistance in advanced B-cell lymphoma. Our findings indicate that anti-CD20-IFNα eradicates B-cell lymphoma by employing tumor cells as APCs to reactivate tumor-infiltrating CD8⁺ T cells and synergizing with anti-PD-L1 treatment. Cancer Immunol Res; 5(7); 560-70. ©2017 AACR.

Herpes Simplex Virus Glycoprotein D Targets a Specific Dendritic Cell Subset and Improves the Performance of Vaccines to Human Papillomavirus-Associated Tumors

Cervical cancer is a major public health problem and one of the leading causes of cancer deaths in women. Virtually all cases of cervical cancer, as well as a growing share of anal and head/neck tumors, are associated with human papillomavirus (HPV) infection. Despite the effectiveness, the available prophylactic vaccines do not benefit women with cervical lesions or cancer. Therefore, the search of new immunotherapeutic approaches to treat HPV-induced tumors is still a priority. The present study characterizes a therapeutic antitumor vaccine based on the genetic fusion of the Herpes simplex virus-1 (HSV-1) glycoprotein D (gD) with the E7 oncoprotein from HPV-16 (gDE7). Two subcutaneous doses of gDE7, admixed with poly (I:C), conferred complete and long-lasting therapeutic antitumor protection on mice previously challenged with tumor cells expressing the HPV-16 oncoproteins. The vaccine induced multifunctional E7-specific CD8⁺ T cells with cytotoxic activity and effector memory phenotype (CD44⁺ CD62L^low). In addition, gDE7 admixed with poly (I:C) vaccination controlled the expansion of tumor-induced regulatory T cells and myeloid-derived suppressor cells. More importantly, gDE7 activated mouse CD11c⁺ CD8α⁺ and human BDCA3⁺ dendritic cells (DC), specialized in antigen cross-presentation to CD8⁺ T cells, under in vitro conditions. These results indicated that the activation of a specific DC population, mediated by gD, improved the antigen-specific immune responses and the therapeutic performance induced by antitumor vaccines. These results open perspectives for the clinical testing of gDE7-based vaccines under the concept of active immunization as a tool for the therapeutic control of cancer. Mol Cancer Ther; 16(9); 1922-33. ©2017 AACR.

Liver sinusoidal endothelial cell cross-priming is supported by CD4 T cell-derived IL-2

BACKGROUND & AIMS

Liver sinusoidal endothelial cells (LSECs) are prominent liver-resident antigen (cross-)presenting cells. LSEC cross-priming of naïve CD8 T cells does not require CD4 T cell help in contrast to priming by dendritic cells (DC) but leads to the formation of memory T cells that is preceded by transient Granzyme B (GzmB) expression. Here we provide evidence for a so far unrecognized CD4 T helper cell function in LSEC-induced CD8 T cell activation.

METHODS

Naïve CD8 T cells and differentiated T helper 1 (T_h1) cells were stimulated by antigen-presenting LSEC, and GzmB expression in CD8 T cells was determined by flow cytometry. To identify molecular pathways mediating this GzmB expression, mechanistic proof-of-concept experiments were conducted using stimulatory anti-CD3 antibody together with Hyper-IL-6.

RESULTS

We demonstrate that LSECs simultaneously function in antigen co-presentation to CD8 and CD4 T cells. Such co-presentation revealed a function of T_h1 cells to increase GzmB expression in CD8 T cells after LSEC but not DC cross-priming. IL-2 released from T_h1 cells was required but not sufficient for rapid GzmB induction in CD8 T cells. T cell receptor together with IL-6 trans-signaling was necessary for IL-2 to mediate rapid GzmB induction.

CONCLUSIONS

Our findings indicate that LSECs can serve as a platform to facilitate CD4-CD8 T cell crosstalk enhancing the immune function of LSECs to cross-prime CD8 T cells. IL-6 trans-signaling-mediated responsiveness for IL-2 inducing sustained GzmB expression in CD8 T cells reveals unique mechanisms of CD4 T cell help and CD8 T cell differentiation through liver-resident antigen-presenting cells.

LAY SUMMARY

Our findings demonstrate that LSEC co-present antigen to CD8 and CD4 T cells and thereby enable CD4 T cell help for LSEC-priming of CD8 T cells. This CD4 T cell help selectively enhances the rapid upregulation of GzmB and effector function of LSEC-primed CD8 T cells thereby enhancing functional differentiation towards CD8 effector T cells.

Dying cells actively regulate adaptive immune responses

Dying cells have an important role in the initiation of CD8⁺ T cell-mediated immunity. The cross-presentation of antigens derived from dying cells enables dendritic cells to present exogenous tissue-restricted or tumour-restricted proteins on MHC class I molecules. Importantly, this pathway has been implicated in multiple autoimmune diseases and accounts for the priming of tumour antigen-specific T cells. Recent data have revealed that in addition to antigen, dying cells provide inflammatory and immunogenic signals that determine the efficiency of CD8⁺ T cell cross-priming. The complexity of these signals has been evidenced by the multiple molecular pathways that result in cell death and that have now been shown to differentially influence antigen transfer and immunity. In this Review, we provide a detailed summary of both the passive and active signals that are generated by dying cells during their initiation of CD8⁺ T cell-mediated immunity. We propose that molecules generated alongside cell death pathways - inducible damage-associated molecular patterns (iDAMPs) - are upstream immunological cues that actively regulate adaptive immunity.

Novel Adjuvant Based on the Pore-Forming Protein Sticholysin II Encapsulated into Liposomes Effectively Enhances the Antigen-Specific CTL-Mediated Immune Response

Vaccine strategies to enhance CD8⁺ CTL responses remain a current challenge because they should overcome the plasmatic and endosomal membranes for favoring exogenous Ag access to the cytosol of APCs. As a way to avoid this hurdle, sticholysin (St) II, a pore-forming protein from the Caribbean Sea anemone Stichodactyla helianthus, was encapsulated with OVA into liposomes (Lp/OVA/StII) to assess their efficacy to induce a CTL response. OVA-specific CD8⁺ T cells transferred to mice immunized with Lp/OVA/StII experienced a greater expansion than when the recipients were injected with the vesicles without St, mostly exhibiting a memory phenotype. Consequently, Lp/OVA/StII induced a more potent effector function, as shown by CTLs, in vivo assays. Furthermore, treatment of E.G7-OVA tumor-bearing mice with Lp/OVA/StII significantly reduced tumor growth being more noticeable in the preventive assay. The contribution of CD4⁺ and CD8⁺ T cells to CTL and antitumor activity, respectively, was elucidated. Interestingly, the irreversibly inactive variant of the StI mutant StI W111C, encapsulated with OVA into Lp, elicited a similar OVA-specific CTL response to that observed with Lp/OVA/StII or vesicles encapsulating recombinant StI or the reversibly inactive StI W111C dimer. These findings suggest the relative independence between StII pore-forming activity and its immunomodulatory properties. In addition, StII-induced in vitro maturation of dendritic cells might be supporting these properties. These results are the first evidence, to our knowledge, that StII, a pore-forming protein from a marine eukaryotic organism, encapsulated into Lp functions as an adjuvant to induce a robust specific CTL response.

Resident macrophages in the healthy and inflamed intestinal muscularis externa

Macrophages reside in a dense cellular network in the intestinal muscularis externa, and there is emerging evidence that the functionality of these cells determines the local microenvironment. Inflammatory responses during intestinal diseases change the homeostatic functionality of these cells causing inflammation and intestinal dysmotility. Such disturbances are not only induced by a change in the cellular composition in the intestinal muscularis but also by an altered crosstalk with the peripheral and central nervous system. In this review, we summarize the role of muscularis macrophages in the intestine in homeostasis and inflammation. We compare the functionality, the phenotype, and the origin of muscularis macrophages to their neighboring counterparts within the different layers of the intestine. We outline the cellular crosstalk with the enteric and the peripheral nervous system and summarize the current therapeutic approaches to modulate the functionality of these phagocytes.

Generation and functional characterization of MDSC-like cells

Myeloid-derived suppressor cells (MDSC) are critical in regulating immune responses by suppressing antigen presenting cells (APC) and T cells. We previously observed that incubation of peripheral blood monocytes with interleukin (IL)-10 during their differentiation to monocyte-derived dendritic cells (moDCs) results in the generation of an APC population with a CD14⁺HLA-DR^lowphenotype (IL-10-APC) with reduced stimulatory capacity similar to human MDSC. Co-incubation experiments now revealed that the addition of IL-10-APC to moDC caused a reduction of DC-induced T-cell proliferation, of the expression of maturation markers, and of secreted cytokines and chemokines such as TNF-α, IL-6, MIP-1α and Rantes. Addition of IL-10-APC increased the immunosuppressive molecule osteoactivin and its corresponding receptor syndecan-4 on moDC. Moreover, CD14⁺HLA-DR^low MDSC isolated from healthy donors expressed high levels of osteoactivin, which was even further upregulated by the auxiliary addition of IL-10. Using transcriptome analysis, we identified a set of molecules and pathways mediating these effects. In addition, we found that IL-10-APC as well as human isolated MDSC expressed higher levels of programmed death (PD)-1, PD-ligand-1 (PD-L1), glucocorticoid-induced-tumor-necrosis-factor-receptor-related-protein (GITR) and GITR-ligand. Inhibition of osteoactivin, syndecan-4, PD-1 or PD-L1 on MDSC by using blocking antibodies restored the stimulatory capacity of DC in co-incubation experiments. Activation of MDSC with Dectin-1 ligand curdlan reduced the expression of osteoactivin and PD-L1. Our results demonstrate that osteoactivin/syndecan-4 and PD-/PD-L1 are key molecules that are profoundly involved in the inhibitory effects of MDSC on DC function and might be promising tools for clinical application.

The Novel Toll-Like Receptor 2 Agonist SUP3 Enhances Antigen Presentation and T Cell Activation by Dendritic Cells

Dendritic cells (DCs) are highly specialized antigen-presenting cells that play crucial roles in innate and adaptive immunity. Previous studies suggested that Toll-like receptor (TLR) agonists could be used as potential adjuvants, as activation of TLRs can boost DC-induced immune responses. TLR2 agonists have been shown to enhance DC-mediated immune responses. However, classical TLR2 agonists such as Pam3CSK4 are not stable enough in vivo, which limits their clinical applications. In this study, a novel structurally stable TLR2 agonist named SUP3 was designed. Functional analysis showed that SUP3 induced much stronger antitumor response than Pam3CSK4 by promoting cytotoxic T lymphocytes activation in vivo. This effect was achieved through the following mechanisms: SUP3 strongly enhanced the ability of antigen cross-presentation by DCs and subsequent T cell activation. SUP3 upregulated the expression of costimulatory molecules on DCs and increased antigen deposition in draining lymph nodes. More interestingly, SUP3 induced less amount of pro-inflammatory cytokine production in vivo compared to other TLR agonists such as lipopolysaccharide. Taken together, SUP3 could serve as a novel promising immune adjuvant in vaccine development and immune modulations.

Cross-Presentation of Soluble and Cell-Associated Antigen by Murine Hepatocytes Is Enhanced by Collectrin Expression

Cross-presentation is a modular series of intracellular events dictating the internalization and subsequent MHC class I (MHC I) display of extracellular Ags. This process has been defined in dendritic cells and plays a fundamental role in the induction of CD8⁺ T cell immunity during viral, intracellular bacterial, and antitumor responses. Herein, acute viral infection of murine liver with adenovirus, a model for intrahepatic cross-presentation, confirms hepatocytes directly contribute to cross-presentation of Ags and priming the pool of naive CD8⁺ T cells within the liver microenvironment. Processing of soluble and cell-associated Ags into peptide displayed by MHC I is however defective in hepatocytes lacking collectrin, an intracellular chaperone protein that localizes within the endoplasmic reticulum-Golgi intermediate compartment. Loss of hepatic collectrin expression leads to the diminished cross-priming and expansion of cytolytic antiviral CD8⁺ T cells. This study demonstrates that collectrin positively regulates processing of engulfed Ags into MHC I:peptide complexes within hepatocytes. Collectrin-mediated cross-presentation supports intrahepatic adaptive antiviral immune responses and may lead to insights into the nature of how the liver acts as a primary site of CD8⁺ T cell activation.

Efferocytosis of Pathogen-Infected Cells

The prompt and efficient clearance of unwanted and abnormal cells by phagocytes is termed efferocytosis and is crucial for organism development, maintenance of tissue homeostasis, and regulation of the immune system. Dying cells are recognized by phagocytes through pathways initiated via "find me" signals, recognition via "eat me" signals and down-modulation of regulatory "don't eat me" signals. Pathogen infection may trigger cell death that drives phagocytic clearance in an immunologically silent, or pro-inflammatory manner, depending on the mode of cell death. In many cases, efferocytosis is a mechanism for eliminating pathogens and pathogen-infected cells; however, some pathogens have subverted this process and use efferocytic mechanisms to avoid innate immune detection and assist phagocyte infection. In parallel, phagocytes can integrate signals received from infected dying cells to elicit the most appropriate effector response against the infecting pathogen. This review focuses on pathogen-induced cell death signals that drive infected cell recognition and uptake by phagocytes, and the outcomes for the infected target cell, the phagocyte, the pathogen and the host.

Lymph node - an organ for T-cell activation and pathogen defense

The immune system is a multicentered organ that is characterized by intimate interactions between its cellular components to efficiently ward off invading pathogens. A key constituent of this organ system is the distinct migratory activity of its cellular elements. The lymph node represents a pivotal meeting point of immune cells where adaptive immunity is induced and regulated. Additionally, besides barrier tissues, the lymph node is a critical organ where invading pathogens need to be eliminated in order to prevent systemic distribution of virulent microbes. Here, we explain how the lymph node is structurally and functionally organized to fulfill these two critical functions - pathogen defense and orchestration of adaptive immunity. We will discuss spatio-temporal aspects of cellular immune responses focusing on CD8 T cells and review how and where these cells are activated in the context of viral infections, as well as how viral antigen expression kinetics and different antigen presentation pathways are involved. Finally, we will describe how such responses are regulated and 'helped', and discuss how this relates to intranodal positioning and cellular migration of the various cellular components that are involved in these processes.

The role of liver sinusoidal cells in local hepatic immune surveillance

Although the liver's function as unique immune organ regulating immunity has received a lot of attention over the last years, the mechanisms determining hepatic immune surveillance against infected hepatocytes remain less well defined. Liver sinusoidal cells, in particular, liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), serve as physical platform for recruitment and anchoring of blood-borne immune cells in the liver. Liver sinusoidal cells also function as portal of entry for infectious microorganisms targeting the liver such as hepatotropic viruses, bacteria or parasites. At the same time, liver sinusoidal cells actively contribute to achieve immune surveillance against bacterial and viral infections. KCs function as adhesion hubs for CD8 T cells from the circulation, which initiates the interaction of virus-specific CD8 T cells with infected hepatocytes. Through their phagocytic function, KCs contribute to removal of bacteria from the circulation and engage in cross talk with sinusoidal lymphocyte populations to achieve elimination of phagocytosed bacteria. LSECs contribute to local immune surveillance through cross-presentation of viral antigens that causes antigen-specific retention of CD8 T cells from the circulation. Such cross-presentation of viral antigens activates CD8 T cells to release TNF that in turn triggers selective killing of virus-infected hepatocytes. Beyond major histocompatibility complex (MHC)-restricted T-cell immunity, CD1- and MR1-restricted innate-like lymphocytes are found in liver sinusoids whose roles in local immune surveillance against infection need to be defined. Thus, liver sinusoidal cell populations bear key functions for hepatic recruitment and for local activation of immune cells, which are both required for efficient immune surveillance against infection in the liver.

p38α has an important role in antigen cross-presentation by dendritic cells

The role of the p38 signaling pathway in the innate and adaptive immune responses has been well documented, especially in inflammatory cytokine production by dendritic cells (DCs). However, whether the p38 signaling pathway affects the important antigen (Ag) presentation function of DCs remains largely unknown. In this study, we reported that the deletion of p38α resulted in an impaired cross-presentation ability of CD8⁺ conventional DCs (cDCs) and a reduction in the direct presentation ability of CD8^- cDCs ex vivo. Further study revealed that p38α had a crucial role in Ag processing by CD8⁺ cDCs but did not affect the Ag uptake or co-stimulation of T cells. Moreover, p38α deficiency led to reduced cross-priming of T cells in vivo. The production of the IL-12p40 and IL-12p70 cytokines by p38α-deficient cDCs was also significantly reduced. Our study identified a new role for p38α in modulating the important antigen cross-presentation function of DCs.

Immunotherapy for Lung Malignancies: From Gene Sequencing to Novel Therapies

Harnessing the immune system to fight cancer is an exciting advancement in lung cancer therapy. Antitumor immunity can be augmented by checkpoint blockade therapy, which removes the inhibition/brakes imposed on the immune system by the tumor. Checkpoint blockade therapy with anti-programmed cell death protein 1 (anti-PD-1)/anti-programmed death ligand 1 (anti-PDL-1) antibodies causes tumor regression in about 25% of patients with lung cancer. In another approach, the immune system is forced or accelerated to attack the tumor through augmentation of the antitumor response against mutations carried by each lung tumor. This latter approach has become feasible since the advent of next-generation sequencing technology, which allows identification of the specific mutations that each individual lung tumor bears. Indeed lung cancers are now known to have high mutation rates, making them logical targets for mutation-directed immune therapies. We review how sequencing of lung cancer mutations leads to better understanding of how the immune system recognizes tumors, providing improved opportunities to track antitumor immunity and ultimately leading to the development of personalized vaccine strategies aimed at unleashing the host immune system to attack mutations in the tumor.

Trends and advances in tumor immunology and lung cancer immunotherapy

Among several types of tumor, lung cancer is considered one of the most fatal and still the main cause of cancer-related deaths. Although chemotherapeutic agents can improve survival and quality of life compared with symptomatic treatment, cancers usually still progress after chemotherapy and are often aggravated by serious side effects. In the last few years there has been a growing interest in immunotherapy for lung cancer based on promising preliminary results in achieving meaningful and durable treatments responses with minimal manageable toxicity. This article is divided into two parts, the first part discusses the role of human immune system in controlling and eradicating cancer and the mechanisms of immune response evasion by tumor. The second part reviews the recent progress made in immunotherapy for lung cancer with results from trials evaluating therapeutic vaccines in addition to immune checkpoint blockade, specifically cytotoxic T lymphocyte associated protein 4, programmed death receptor 1 pathway, using monoclonal antibodies.

Present Yourself! By MHC Class I and MHC Class II Molecules

Since the discovery of MHC molecules, it has taken 40 years to arrive at a coherent picture of how MHC class I and MHC class II molecules really work. This is a story of the proteases and MHC-like chaperones that support the MHC class I and II molecules in presenting peptides to the immune system. We now understand that the MHC system shapes both the repertoire of presented peptides and the subsequent T cell response, with important implications ranging from transplant rejection to tumor immunotherapies. Here we present an illustrated review of the ins and outs of MHC class I and MHC class II antigen presentation.

The Future of Combining Carbon-Ion Radiotherapy with Immunotherapy: Evidence and Progress in Mouse Models

After >60 years since the first treatment, particle radiation therapy (RT) is now used to treat various types of tumors worldwide. Particle RT results in favorable outcomes, especially in local control, because of its biological properties and excellent dose distribution. However, similar to other types of cancer treatment, metastasis control is a crucial issue. Notably, immunotherapy is used for cancer treatment with high risk for recurrence and/or metastasis. These 2 cancer therapies could be ideal, complementary partners for noninvasive cancer treatment. In this review, we will focus on preclinical studies combining particle RT, especially carbon ion RT, and immunotherapy.

The administration route is decisive for the ability of the vaccine adjuvant CAF09 to induce antigen-specific CD8(+) T-cell responses: The immunological consequences of the biodistribution profile

A prerequisite for vaccine-mediated induction of CD8⁺ T-cell responses is the targeting of dendritic cell (DC) subsets specifically capable of cross-presenting antigen epitopes to CD8⁺ T cells. Administration of a number of cationic adjuvants via the intraperitoneal (i.p.) route has been shown to result in strong CD8⁺ T-cell responses, whereas immunization via e.g. the intramuscular (i.m.) or subcutaneous (s.c.) routes often stimulate weak CD8⁺ T-cell responses. The hypothesis for this is that self-drainage of the adjuvant/antigen to the lymphoid organs, which takes place upon i.p. immunization, is required for the subsequent activation of cross-presenting lymphoid organ-resident CD8α⁺ DCs. In contrast, s.c. or i.m. immunization usually results in the formation of a depot at the site of injection (SOI), which hinders the self-drainage and targeting of the vaccine to cross-presenting CD8α⁺ DCs. We investigated this hypothesis by correlating the biodistribution pattern and the adjuvanticity of the strong CD8⁺ T-cell inducing liposomal cationic adjuvant formulation 09 (CAF09), which is composed of dimethyldioctadecylammonium bromide/monomycoloyl glycerol liposomes with polyinosinic:polycytidylic acid electrostatically adsorbed to the surface. Biodistribution studies with radiolabeled CAF09 and a surface-adsorbed model antigen [ovalbumin (OVA)] showed that a significantly larger fraction of the vaccine dose localized in the draining lymph nodes (dLNs) and the spleen 6 h after i.p. immunization, as compared to after i.m. immunization. Studies with fluorescently labelled OVA + CAF09 demonstrated a preferential association of OVA + CAF09 to DCs/monocytes, as compared to macrophages and B cells, following i.p. immunization. Administration of OVA + CAF09 via the i.p. route did also result in DC activation, whereas no DC activation could be measured within the same period with unadjuvanted OVA and OVA + CAF09 administered via the s.c. or i.m. routes. In the dLNs, the highest level of activated, cross-presenting CD8α⁺ DCs was detected at 24 h post immunization, whereas an influx of activated, migrating and cross-presenting CD103⁺ DCs to the dLNs could be measured after 48 h. This suggests that the CD8α⁺ DCs are activated by self-draining OVA + CAF09 in the lymphoid organs, whereas the CD103⁺ DCs are stimulated by the OVA + CAF09 at the SOI. These results support the hypothesis that the self-drainage of OVA + CAF09 to the draining LNs is required for the activation of CD8α⁺ DCs, while the migratory CD103⁺ DCs may play a role in sustaining the subsequent induction of strong CD8⁺ T-cell responses.

Evaluation of novel synthetic TLR7/8 agonists as vaccine adjuvants

Small-molecule adjuvants that boost and direct adaptive immunity provide a powerful means to increase the effectiveness of vaccines. Through rational design several novel imidazoquinoline and oxoadenine TLR7/8 agonists, each with unique molecular modifications, were synthesized and assessed for their ability to augment adaptive immunity. All agonists bound human TLR7 and TLR8 and induced maturation of both human mDCs and pDCs. All agonists prompted production of type I interferon and/or proinflammatory cytokines, albeit with varying potencies. In most in vitro assays, the oxoadenine class of agonists proved more potent than the imidazoquinolines. Therefore, an optimized oxoadenine TLR7/8 agonist that demonstrated maximal activity in the in vitro assays was further assessed in a vaccine study with the CRM197 antigen in a porcine model. Antigen-specific antibody production was greatly enhanced in a dose dependent manner, with antibody titers increased 800-fold compared to titers from pigs vaccinated with the non-adjuvanted vaccine. Moreover, pigs vaccinated with antigen containing the highest dose of adjuvant promoted a 13-fold increase in the percentage of antigen-specific CD3(+)/CD8(+) T cells over pigs vaccinated with antigen alone. Together this work demonstrates the promise of these novel TLR7/8 agonists as effective human vaccine adjuvants.

Integrating conventional and antibody-based targeted anticancer treatment into immunotherapy

In advanced cancer, current conventional therapies or immunotherapies cannot eradicate all tumor cells for most patients. Integration of these two treatments for synergistic effects could eradicate more tumor cells and increase overall survival rates. But proper integration is a challenge, partly due to a poor understanding of the impact of conventional treatment on immune responses. Intensive chemo/radiotherapy may impair ongoing immune responses whilst lower intensity of therapy might not kill enough tumor cells, both leading to tumor relapse. Current understanding of mechanisms of resistance to conventional and targeted cancer therapies has focused on cell intrinsic pathways that trigger DNA damage/repair or signaling pathways related to cell growth. Recent reports show that host T cells properly primed against tumor specific antigens after conventional treatment can integrate with direct cytotoxic effects induced by radiation or chemotherapy to profoundly control tumors. Following cytotoxic anticancer treatment, tumor derived DAMPs (damage-associated molecular patterns) can be sensed by innate cells which drives type I interferon (IFNs production) for cross priming of CD8⁺ T cells. Some types and protocols of chemotherapy or radiation can increase tumor infiltrating lymphocytes that overcome resistance to immunotherapy. As such, a deeper understanding to the immune mechanisms of conventional and targeted cancer therapies will lead toward novel combinatorial anticancer strategies with improved clinical benefit.

Polymer-Based DNA Delivery Systems for Cancer Immunotherapy

The use of gene delivery systems for the expression of antigenic proteins is an established means for activating a patient’s own immune system against the cancer they carry. Since tumor cells are poor antigen-presenting cells, cross-presentation of tumor antigens by dendritic cells (DCs) is essential for the generation of tumor-specific cytotoxic T-lymphocyte responses. A number of polymer-based nanomedicines have been developed to deliver genes into DCs, primarily by incorporating tumor-specific, antigen-encoding plasmid DNA with polycationic molecules to facilitate DNA loading and intracellular trafficking. Direct in vivo targeting of plasmid DNA to DC surface receptors can induce high transfection efficiency and long-term gene expression, essential for antigen loading onto major histocompatibility complex molecules and stimulation of T-cell responses. This chapter summarizes the physicochemical properties and biological information on polymer-based non-viral vectors used for targeting DCs, and discusses the main challenges for successful in vivo gene transfer into DCs.

STAT2 Is Required for TLR-Induced Murine Dendritic Cell Activation and Cross-Presentation

TLR-stimulated cross-presentation by conventional dendritic cells (cDCs) is important in host defense and antitumor immunity. We recently reported that cDCs lacking the type I IFN signaling molecule STAT2 are impaired in cross-presenting tumor Ags to CD8(+) T cells. To investigate how STAT2 affects cross-presentation, we determined its requirements for dendritic cell activation. In this study, we report that STAT2 is essential for the activation of murine female cDCs upon TLR3, -4, -7, and -9 stimulation. In response to various TLR ligands, Stat2(-/-) cDCs displayed reduced expression of costimulatory molecules and type I IFN-stimulated genes. The cDC responses to exogenous IFN-α that we evaluated required STAT2 activation, indicating that the canonical STAT1-STAT2 heterodimers are the primary signaling transducers of type I IFNs in cDCs. Interestingly, LPS-induced production of IL-12 was STAT2 and type I IFN receptor (IFNAR) dependent, whereas LPS-induced production of TNF-α and IL-6 was STAT2 and IFNAR independent, suggesting a specific role of the IFNAR-STAT2 axis in the stimulation of proinflammatory cytokines by LPS in cDCs. In contrast, R848- and CpG-induced cytokine production was less influenced by the IFNAR-STAT2 axis. Short kinetics and IFNAR blockade studies showed that STAT2 main function is to transduce signals triggered by autocrine type I IFNs. Importantly, Stat2(-/-) cDCs were deficient in cross-presenting to CD8(+) T cells in vitro upon IFN-α, CpG, and LPS stimulation, and also in cross-priming and licensing cytotoxic T cell killers in vivo. We conclude that STAT2 plays a critical role in TLR-induced dendritic cell activation and cross-presentation, and thus is vital in host defense.

Extracellular HSPs: The Complicated Roles of Extracellular HSPs in Immunity

Extracellular heat-shock proteins (HSPs) interact with the immune system in a very complex manner. Many such HSPs exert powerful effects on the immune response, playing both stimulatory and regulatory roles. However, the influence of the HSPs on immunity appears to be positive or negative in nature – rarely neutral. Thus, the HSPs can act as dominant antigens and can comprise key components of antitumor vaccines. They can also function as powerful immunoregulatory agents and, as such, are employed to treat inflammatory diseases or to extend the lifespan of tissue transplants. Small modifications in the cellular milieu have been shown to flip the allegiances of HSPs from immunoregulatory agents toward a potent inflammatory alignment. These mutable properties of HSPs may be related to the ability of these proteins to interact with multiple receptors often with mutually confounding properties in immune cells. Therefore, understanding the complex immune properties of HSPs may help us to harness their potential in treatment of a range of conditions.

Immunological functions of liver sinusoidal endothelial cells

Liver sinusoidal endothelial cells (LSECs) line the liver sinusoids and separate passenger leukocytes in the sinusoidal lumen from hepatocytes. LSECs further act as a platform for adhesion of various liver-resident immune cell populations such as Kupffer cells, innate lymphoid cells or liver dendritic cells. In addition to having an extraordinary scavenger function, LSECs possess potent immune functions, serving as sentinel cells to detect microbial infection through pattern recognition receptor activation and as antigen (cross)-presenting cells. LSECs cross-prime naive CD8 T cells, causing their rapid differentiation into memory T cells that relocate to secondary lymphoid tissues and provide protection when they re-encounter the antigen during microbial infection. Cross-presentation of viral antigens by LSECs derived from infected hepatocytes triggers local activation of effector CD8 T cells and thereby assures hepatic immune surveillance. The immune function of LSECs complements conventional immune-activating mechanisms to accommodate optimal immune surveillance against infectious microorganisms while preserving the integrity of the liver as a metabolic organ.

CD103+ Kidney Dendritic Cells Protect against Crescentic GN by Maintaining IL-10-Producing Regulatory T Cells

Kidney dendritic cells (DCs) regulate nephritogenic T cell responses. Most kidney DCs belong to the CD11b⁺ subset and promote crescentic GN (cGN). The function of the CD103⁺ subset, which represents <5% of kidney DCs, is poorly understood. We studied the role of CD103⁺ DCs in cGN using several lines of genetically modified mice that allowed us to reduce the number of these cells. In all lines, we detected a reduction of FoxP3⁺ intrarenal regulatory T cells (T_regs), which protect against cGN. Mice lacking the transcription factor Batf3 had a more profound reduction of CD103⁺ DCs and T_regs than did the other lines used, and showed the most profound aggravation of cGN. The conditional reduction of CD103⁺ DC numbers by 50% in Langerin-DTR mice halved T_reg numbers, which did not suffice to significantly aggravate cGN. Mice lacking the cytokine Flt3L had fewer CD103⁺ DCs and T_regs than Langerin-DTR mice but exhibited milder cGN than did Batf3^-/- mice presumably because proinflammatory CD11b⁺ DCs were somewhat depleted as well. Conversely, Flt3L supplementation increased the number of CD103⁺ DCs and T_regs, but also of proinflammatory CD11b⁺ DCs. On antibody-mediated removal of CD11b⁺ DCs, Flt3L supplementation ameliorated cGN. Mechanistically, CD103⁺ DCs caused cocultured T cells to differentiate into T_regs and produced the chemokine CCL20, which is known to attract T_regs into the kidney. Our findings show that CD103⁺ DCs foster intrarenal FoxP3⁺ T_reg accumulation, thereby antagonizing proinflammatory CD11b⁺ DCs. Thus, increasing CD103⁺ DC numbers or functionality might be advantageous in cGN.

Inflammatory microenvironment and human papillomavirus-induced carcinogenesis

More than 15% of the global cancer burden is attributable to infectious agents. Pathogens that cause persistent infections are strongly associated with cancer, inflammation being a major component of the chronic infections as revealed by basic, clinical and epidemiological studies. Persistent infection and viral oncoproteins induce specific cellular pathways modifications that promote tumorigenesis. Deregulated and continuous immune response leads to severe tissue and systemic damage, impaired tumor surveillance and consequent carcinogenesis promotion by selecting for metastatic and therapeutically resistant tumor phenotypes. In this review, the role of inflammatory microenvironment in the HPV-induced carcinogenesis is addressed, with a specific focus on the involvement of the immune molecules and microRNAs as well as their delivery through the microvesicle cargo.

Staying local-antigen presentation in the liver

The liver is known as organ with unique immune competence. Besides its unique microenvironment that is determined by gut-derived portal venous blood constituents and the presence of enzymes with immune regulatory properties, liver antigen presenting cell populations regulate antigen-specific immunity in a local fashion. In addition to bone marrow-derived dendritic cells and myeloid cells such as macrophages and monocytes, also truly liver-resident cell populations function as antigen presenting cells such as liver sinusoidal endothelial cells and hepatocytes. The functional outcome of antigen-presentation by these cell populations is diverse and ranges from generation of regulatory CD4 cells, to induction of memory CD8 T cells or deletional tolerance, which generates a complex network of antigen-presenting cells that determines hepatic immune regulation and local immune surveillance against viral infection.

Pathogen-Associated Molecular Patterns Induced Crosstalk between Dendritic Cells, T Helper Cells, and Natural Killer Helper Cells Can Improve Dendritic Cell Vaccination

A coordinated cellular interplay is of crucial importance in both host defense against pathogens and malignantly transformed cells. The various interactions of Dendritic Cells (DC), Natural Killer (NK) cells, and T helper (Th) cells can be influenced by a variety of pathogen-associated molecular patterns (PAMPs) and will lead to enhanced CD8⁺ effector T cell responses. Specific Pattern Recognition Receptor (PRR) triggering during maturation enables DC to enhance Th1 as well as NK helper cell responses. This effect is correlated with the amount of IL-12p70 released by DC. Activated NK cells are able to amplify the proinflammatory cytokine profile of DC via the release of IFN-γ. The knowledge on how PAMP recognition can modulate the DC is of importance for the design and definition of appropriate therapeutic cancer vaccines. In this review we will discuss the potential role of specific PAMP-matured DC in optimizing therapeutic DC-based vaccines, as some of these DC are efficiently activating Th1, NK cells, and cytotoxic T cells. Moreover, to optimize these vaccines, also the inhibitory effects of tumor-derived suppressive factors, for example, on the NK-DC crosstalk, should be taken into account. Finally, the suppressive role of the tumor microenvironment in vaccination efficacy and some proposals to overcome this by using combination therapies will be described.

Synthesis of a Liposomal MUC1 Glycopeptide-Based Immunotherapeutic and Evaluation of the Effect of l-Rhamnose Targeting on Cellular Immune Responses

Generation of a CD8(+) response to extracellular antigen requires processing of the antigen by antigen presenting cells (APC) and cross-presentation to CD8(+) T cell receptors via MHC class I molecules. Cross-presentation is facilitated by efficient antigen uptake followed by immune-complex-mediated maturation of the APCs. We hypothesize that improved antigen uptake of a glycopeptide sequence containing a CD8(+) T cell epitope could be achieved by delivering it on a liposome surface decorated with an immune complex-targeting ligand, an l-Rhamnose (Rha) epitope. We synthesized a 20-amino-acid glycopeptide TSAPDT(GalNAc)RPAPGSTAPPAHGV from the variable number tandem repeat region of the tumor marker MUC1 containing an N-terminal azido moiety and a tumor-associated α-N-acetyl galactosamine (GalNAc) at the immunogenic DTR motif. The MUC1 antigen was attached to Pam3Cys, a Toll-like receptor-2 ligand via copper(I)-catalyzed azido-alkyne cycloaddition (CuAAc) chemistry. The Rha-decorated liposomal Pam3Cys-MUC1-Tn 4 vaccine was evaluated in groups of C57BL/6 mice. Some groups were previously immunized to generate anti-Rha antibodies. Anti-Rha antibody expressing mice that received the Rha liposomal vaccine showed higher cellular immunogenicity compared to the control group while maintaining a strong humoral response.

The Role of Adaptive Immunity in the Efficacy of Targeted Cancer Therapies

Accumulating evidence indicates that the efficacy of tumor-targeted therapies relies on the host immune response, including targeted small-molecule and antibody approaches that were not previously thought to have an immune component. Here, we review the current understanding of how targeted therapies on tumor cells could have a major impact on the immune response, and how this relates to the therapeutic efficacy of these approaches. In this context, we evaluate different strategies that combine targeted therapies with immunotherapy approaches, and discuss past and ongoing clinical trials. We highlight gaps in knowledge, and argue that significant progress for combined therapies will require a better understanding of the complex interactions between immune cells, the tumor, and the tumor microenvironment (TME) in different cancer settings.

Immunological Effects of Conventional Chemotherapy and Targeted Anticancer Agents

The tremendous clinical success of checkpoint blockers illustrates the potential of reestablishing latent immunosurveillance for cancer therapy. Although largely neglected in the clinical practice, accumulating evidence indicates that the efficacy of conventional and targeted anticancer agents does not only involve direct cytostatic/cytotoxic effects, but also relies on the (re)activation of tumor-targeting immune responses. Chemotherapy can promote such responses by increasing the immunogenicity of malignant cells, or by inhibiting immunosuppressive circuitries that are established by developing neoplasms. These immunological "side" effects of chemotherapy are desirable, and their in-depth comprehension will facilitate the design of novel combinatorial regimens with improved clinical efficacy.

Automatic Generation of Validated Specific Epitope Sets

Accurate measurement of B and T cell responses is a valuable tool to study autoimmunity, allergies, immunity to pathogens, and host-pathogen interactions and assist in the design and evaluation of T cell vaccines and immunotherapies. In this context, it is desirable to elucidate a method to select validated reference sets of epitopes to allow detection of T and B cells. However, the ever-growing information contained in the Immune Epitope Database (IEDB) and the differences in quality and subjects studied between epitope assays make this task complicated. In this study, we develop a novel method to automatically select reference epitope sets according to a categorization system employed by the IEDB. From the sets generated, three epitope sets (EBV, mycobacteria and dengue) were experimentally validated by detection of T cell reactivity ex vivo from human donors. Furthermore, a web application that will potentially be implemented in the IEDB was created to allow users the capacity to generate customized epitope sets.

T cells in tumor microenvironment

Tumors progress in a specific area, which supports its development, spreading or shrinking in time with the presence of different factors that effect the fate of the cancer cells. This specialized site is called "tumor microenvironment" and has a composition of heterogenous materials. The immune cells are also residents of this stromal, cancerous, and inflammatory environment, and their types, densities, or functional differences are one of the key factors that mediate the fate of a tumor. T cells as a vital part of the immune system also are a component of tumor microenvironment, and their roles have been elucidated in many studies. In this review, we focused on the immune system components by focusing on T cells and detailed T helper cell subsets in tumor microenvironment and how their behaviors affect either the tumor or the patient's outcome.

Aging Impairs the Ability of Conventional Dendritic Cells to Cross-Prime CD8+ T Cells upon Stimulation with a TLR7 Ligand

The aging process is accompanied by altered immune system functioning and an increased risk of infection. Dendritic cells (DCs) are antigen-presenting cells that play a key role in both adaptive and innate immunity, but how aging affects DCs and their influence on immunity has not been thoroughly established. Here we examined the function of conventional DCs (cDCs) in old mice after TLR7 stimulation, focusing on their ability to cross-prime CD8⁺ T cells. Using polyU, a synthetic ssRNA analog, as TLR7 ligand and OVA as an antigen (Ag) model, we found that cDCs from old mice have a poor ability to stimulate a CD8⁺ T cell-mediated cytotoxic response. cDCs from old mice exhibit alterations in Ag-processing machinery and TLR7 activation. Remarkably, CD8α⁺ cDCs from old mice have an impaired ability to activate naïve CD8⁺ T cells and, moreover, a lower capacity to mature and to process exogenous Ag. Taken together, our results suggest that immunosenescence impacts cDC function, affecting the activation of naïve CD8⁺ T cells and the generation of effector cytotoxic T cells.

RIPK1 and NF-κB signaling in dying cells determines cross-priming of CD8⁺ T cells

Dying cells initiate adaptive immunity by providing both antigens and inflammatory stimuli for dendritic cells, which in turn activate CD8(+) T cells through a process called antigen cross-priming. To define how different forms of programmed cell death influence immunity, we established models of necroptosis and apoptosis, in which dying cells are generated by receptor-interacting protein kinase-3 and caspase-8 dimerization, respectively. We found that the release of inflammatory mediators, such as damage-associated molecular patterns, by dying cells was not sufficient for CD8(+) T cell cross-priming. Instead, robust cross-priming required receptor-interacting protein kinase-1 (RIPK1) signaling and nuclear factor κB (NF-κB)-induced transcription within dying cells. Decoupling NF-κB signaling from necroptosis or inflammatory apoptosis reduced priming efficiency and tumor immunity. Our results reveal that coordinated inflammatory and cell death signaling pathways within dying cells orchestrate adaptive immunity.

Dendritic Cells and Macrophages: Sentinels in the Kidney

The mononuclear phagocytes (dendritic cells and macrophages) are closely related immune cells with central roles in anti-infectious defense and maintenance of organ integrity. The canonical function of dendritic cells is the activation of T cells, whereas macrophages remove apoptotic cells and microbes by phagocytosis. In the kidney, these cell types form an intricate system of mononuclear phagocytes that surveys against injury and infection and contributes to organ homeostasis and tissue repair but may also promote progression of CKD. This review summarizes the general functions and classification of dendritic cells and macrophages in the immune system and recapitulates why overlapping definitions and historically separate research have created controversy about their tasks. Their roles in acute kidney disease, CKD, and renal transplantation are described, and therapeutic strategy to modify these cells for therapeutic purposes is discussed.