Complementary role of CD4+ T cells and secondary lymphoid tissues for cross-presentation of tumor antigen to CD8+ T cells

CD8+ T cell activation in cancer comprises an initial activation phase in lymph nodes followed by effector differentiation within the tumor

Improvements in tumor immunotherapies depend on better understanding of the anti-tumor T cell response. By studying human tumor-draining lymph nodes (TDLNs), we found that activated CD8+ T cells in TDLNs shared functional, transcriptional, and epigenetic traits with TCF1+ stem-like cells in the tumor. The phenotype and TCR overlap suggested that these TDLN cells were precursors to tumor-resident stem-like CD8+ T cells. Murine tumor models revealed that tumor-specific CD8+ T cells were activated in TDLNs but lacked an effector phenotype. These stem-like cells migrated into the tumor, where additional co-stimulation from antigen-presenting cells drove effector differentiation. This model of CD8+ T cell activation in response to cancer is different from that of canonical CD8+ T cell activation to acute viruses, and it proposes two stages of tumor-specific CD8+ T cell activation: initial activation in TDLNs and subsequent effector program acquisition within the tumor after additional co-stimulation.

Adenovirus vaccine therapy with CD137L promotes CD8+ DCs-mediated multifunctional CD8+ T cell immunity and elicits potent anti-tumor activity

Renal carcinoma progresses aggressively in patients with metastatic disease while curative strategies are limited. Here, we constructed a recombinant non-replicating adenovirus (Ad) vaccine encoding an immune activator, CD137L, and a tumor antigen, CAIX, for treating renal carcinoma. In a subcutaneous tumor model, tumor growth was significantly suppressed in the Ad-CD137L/CAIX vaccine group compared with the single vaccine group. The induction and maturity of CD11C+ and CD8+CD11C+ dendritic cell (DC) subsets were promoted in Ad-CD137L/CAIX co-immunized mice. Furthermore, the Ad-CD137L/CAIX vaccine elicited stronger tumor-specific multifunctional CD8+ T cell immune responses as demonstrated by increased proliferation and cytolytic function of CD8+ T cells. Notably, depletion of CD8+ T cells greatly compromised the effective protection provided by Ad-CD137L/CAIX vaccine, suggesting an irreplaceable role of CD8+ T cells for the immunopotency of the vaccine. In both lung metastatic and orthotopic models, Ad-CD137L/CAIX vaccine treatment significantly decreased tumor metastasis and progression and increased the induction of tumor-specific multifunctional CD8+ T cells, in contrast to treatment with the Ad-CAIX vaccine alone. The Ad-CD137L/CAIX vaccine also augmented the tumor-specific multifunctional CD8+ T cell immune response in both orthotopic and metastatic models. These results indicated that Ad-CD137L/CAIX vaccine elicited a potent anti-tumor activity by inducing CD8+DC-mediated multifunctional CD8+ T cell immune responses. The potential strategy of CD137L-based vaccine might be served as a novel treatment for renal carcinoma or other malignant tumors.

An oral cancer vaccine using a Bifidobacterium vector suppresses tumor growth in a syngeneic mouse bladder cancer model

Cancer immunotherapy using immune-checkpoint inhibitors (ICIs) such as PD-1/PD-L1 inhibitors has been well established for various types of cancer. Monotherapy with ICIs, however, can achieve a durable response in only a subset of patients. There is a great unmet need for the ICI-resistant-tumors. Since patients who respond to ICIs should have preexisting antitumor T cell response, combining ICIs with cancer vaccines that forcibly induce an antitumor T cell response is a reasonable strategy. However, the preferred administration sequence of the combination of ICIs and cancer vaccines is unknown. In this study, we demonstrated that combining an oral WT1 cancer vaccine using a Bifidobacterium vector and following anti-PD-1 antibody treatment eliminated tumor growth in a syngeneic mouse model of bladder cancer. This vaccine induced T cell responses specific to multiple WT1 epitopes through the gut immune system. Moreover, in a tumor model poorly responsive to an initial anti-PD-1 antibody, this vaccine alone significantly inhibited the tumor growth, whereas combination with continuous anti-PD-1 antibody could not inhibit the tumor growth. These results suggest that this oral cancer vaccine alone or as an adjunct to anti-PD-1 antibody could provide a novel treatment option for patients with advanced urothelial cancer including bladder cancer.

Blood Vessels and Peripheral Nerves as Key Players in Cancer Progression and Therapy Resistance

Simple Summary

The interactions between cancer cells and the surrounding blood vessels and peripheral nerves are critical in all the phases of tumor development. Accordingly, therapies that specifically target vessels and nerves represent promising anticancer approaches. The first aim of this review is to document the importance of blood vessels and peripheral nerves in both cancer onset and local or distant growth of tumoral cells. We then focus on the state-of-the-art therapies that limit cancer progression through the impairment of blood vessels and peripheral nerves. The mentioned literature is helpful for the scientific community to appreciate the recent advances in these two fundamental components of tumors.

Abstract

Cancer cells continuously interact with the tumor microenvironment (TME), a heterogeneous milieu that surrounds the tumor mass and impinges on its phenotype. Among the components of the TME, blood vessels and peripheral nerves have been extensively studied in recent years for their prominent role in tumor development from tumor initiation. Cancer cells were shown to actively promote their own vascularization and innervation through the processes of angiogenesis and axonogenesis. Indeed, sprouting vessels and axons deliver several factors needed by cancer cells to survive and proliferate, including nutrients, oxygen, and growth signals, to the expanding tumor mass. Nerves and vessels are also fundamental for the process of metastatic spreading, as they provide both the pro-metastatic signals to the tumor and the scaffold through which cancer cells can reach distant organs. Not surprisingly, continuously growing attention is devoted to the development of therapies specifically targeting these structures, with promising initial results. In this review, we summarize the latest evidence that supports the importance of blood vessels and peripheral nerves in cancer pathogenesis, therapy resistance, and innovative treatments.

Tumor cells, rather than dendritic cells, deliver antigen to the lymph node for cross-presentation

It is widely accepted that generation of tumor specific CD8+ T-cell responses occur via cross-priming; however the source of tumor antigen for this event is unknown. We examined the source and form of tumor antigen required for cross-presentation in the local lymph node (LN) using a syngeneic mouse tumor model expressing a marker antigen. We found that cross-presentation of this model tumor antigen in the LN is dependent on continuous traffic of antigen from the tumor site, but without any detectable migration of tumor resident dendritic cells (DCs). Instead, small numbers of tumor cells metastasize to local LNs where they are exposed to a localized CTL attack, resulting in delivery of tumor antigen into the cross-presentation pathway.

Recent Advances in Hyperthermia Therapy-Based Synergistic Immunotherapy

The past decades have witnessed hyperthermia therapy (HTT) as an emerging strategy against malignant tumors. Nanomaterial-based photothermal therapy (PTT) and magnetic hyperthermia (MHT), as highly effective and noninvasive treatment models, offer advantages over other strategies in the treatment of different types of tumors. However, both PTT and MHT cannot completely cure cancer due to recurrence and distal metastasis. In recent years, cancer immunotherapy has attracted widespread attention owing to its capability to activate the body's own natural defense to identify, attack, and eradicate cancer cells. Significant efforts have been devoted to studying the activated immune responses caused by hyperthermia-ablated tumors. In this article, the synergistic mechanism of HTT in immunotherapy, including immunogenic cell death and reversal of the immunosuppressive tumor microenvironment is discussed. The reports of the combination of HTT or HTT-based multimodal therapy with immunotherapy, including immunoadjuvant exploitation, immune checkpoint blockade therapy, and adoptive cellular immunotherapy are summarized. As highlighted, these strategies could achieve synergistically enhanced therapeutic outcomes against both primary tumors and metastatic lesions, prevent cancer recurrence, and prolong the survival period. Finally, current challenges and prospective developments in HTT-synergized immunotherapy are also reviewed.

Induced Regulatory T Cells Superimpose Their Suppressive Capacity with Effector T Cells in Lymph Nodes via Antigen-Specific S1p1-Dependent Egress Blockage

Regulatory T cells (Tregs) restrict overexuberant lymphocyte activation. While close proximity between Tregs and their suppression targets is important for optimal inhibition, and literature indicates that draining lymph nodes (LNs) may serve as a prime location for the suppression, signaling details orchestrating this event are not fully characterized. Using a protocol to enable peripheral generation of inducible antigen-specific Tregs (asTregs) to control allergen-induced asthma, we have identified an antigen-specific mechanism that locks asTregs within hilar LNs which in turn suppresses airway inflammation. The suppressive asTregs, upon antigen stimulation in the LN, downregulate sphingosine-1-phosphate receptor 1 egress receptor expression. These asTregs in turn mediate the downregulation of the same receptor on incoming effector T cells. Therefore, asTregs and effector T cells are locked in these draining LNs for prolonged interactions. Disruption of individual steps of this retention sequence abolishes the inflammation controlled by asTregs. Collectively, this study identifies a new requirement of spatial congregation with their suppression targets essential for asTreg functions and suggests therapeutic programs via Treg traffic control.

Unique CD8+ T Cell-Mediated Immune Responses Primed in the Liver

BACKGROUND

The liver immune environment is tightly regulated to balance immune activation with immune tolerance. Understanding the dominant immune pathways initiated in the liver is important because the liver is a site for cell transplantation, such as for islet and hepatocyte transplantation. The purpose of this study is to examine the consequences of alloimmune stimulation when allogeneic cells are transplanted to the liver in comparison to a different immune locale, such as the kidney.

METHODS

We investigated cellular and humoral immune responses when allogeneic hepatocytes are transplanted directly to the recipient liver by intraportal injection. A heterotopic kidney engraftment site was used for comparison to immune activation in the liver microenvironment.

RESULTS

Transplantation of allogeneic hepatocytes delivered directly to the liver, via recipient portal circulation, stimulated long-term, high magnitude CD8 T cell-mediated allocytotoxicity. CD8 T cells initiated significant in vivo allocytotoxicity as well as rapid rejection of hepatocytes transplanted to the liver even in the absence of secondary lymph nodes or CD4 T cells. In contrast, in the absence of recipient peripheral lymphoid tissue and CD4 T cells, CD8-mediated in vivo allocytotoxicity was abrogated, and rejection was delayed when hepatocellular allografts were transplanted to the kidney subcapsular site.

CONCLUSIONS

These results highlight the CD8-dominant proinflammatory immune responses unique to the liver microenvironment. Allogeneic cells transplanted directly to the liver do not enjoy immune privilege but rather require immunosuppression to prevent rejection by a robust and persistent CD8-dependent allocytotoxicity primed in the liver.

GUCY2C-directed CAR-T cells oppose colorectal cancer metastases without autoimmunity

Adoptive T-cell therapy (ACT) is an emerging paradigm in which T cells are genetically modified to target cancer-associated antigens and eradicate tumors. However, challenges treating epithelial cancers with ACT reflect antigen targets that are not tumor-specific, permitting immune damage to normal tissues, and preclinical testing in artificial xenogeneic models, preventing prediction of toxicities in patients. In that context, mucosa-restricted antigens expressed by cancers exploit anatomical compartmentalization which shields mucosae from systemic antitumor immunity. This shielding may be amplified with ACT platforms employing antibody-based chimeric antigen receptors (CARs), which mediate MHC-independent recog-nition of antigens. GUCY2C is a cancer mucosa antigen expressed on the luminal surfaces of the intestinal mucosa in mice and humans, and universally overexpressed by colorectal tumors, suggesting its unique utility as an ACT target. T cells expressing CARs directed by a GUCY2C-specific antibody fragment recognized GUCY2C, quantified by expression of activation markers and cytokines. Further, GUCY2C CAR-T cells lysed GUCY2C-expressing, but not GUCY2C-deficient, mouse colorectal cancer cells. Moreover, GUCY2C CAR-T cells reduced tumor number and morbidity and improved survival in mice harboring GUCY2C-expressing colorectal cancer metastases. GUCY2C-directed T cell efficacy reflected CAR affinity and surface expression and was achieved without immune-mediated damage to normal tissues in syngeneic mice. These observations highlight the potential for therapeutic translation of GUCY2C-directed CAR-T cells to treat metastatic tumors, without collateral autoimmunity, in patients with metastatic colorectal cancer.

Rational bases for the use of the Immunoscore in routine clinical settings as a prognostic and predictive biomarker in cancer patients

The American Joint Committee on Cancer/Union Internationale Contre le Cancer (AJCC/UICC) tumor, nodes, metastasis (TNM) classification system based on tumor features is used for prognosis estimation and treatment recommendations in most cancers. However, the clinical outcome can vary significantly among patients within the same tumor stage and TNM classification does not predict response to therapy. Therefore, many efforts have been focused on the identification of new markers. Multiple tumor cell-based approaches have been proposed but very few have been translated into the clinic. The recent demonstration of the essential role of the immune system in tumor progression has allowed great advances in the understanding of this complex disease and in the design of novel therapies. The analysis of the immune infiltrate by imaging techniques in large patient cohorts highlighted the prognostic impact of the in situ immune cell infiltrate in tumors. Moreover, the characterization of the immune infiltrates (e.g. type, density, distribution within the tumor, phenotype, activation status) in patients treated with checkpoint-blockade strategies could provide information to predict the disease outcome. In colorectal cancer, we have developed a prognostic score ('Immunoscore') that takes into account the distribution of the density of both CD3(+) lymphocytes and CD8(+) cytotoxic T cells in the tumor core and the invasive margin that could outperform TNM staging. Currently, an international retrospective study is under way to validate the Immunoscore prognostic performance in patients with colon cancer. The use of Immunoscore in clinical practice could improve the patients' prognostic assessment and therapeutic management.

Novel Humoral Prognostic Markers in Small-Cell Lung Carcinoma: A Prospective Study

Purpose

Favourable small cell lung carcinoma (SCLC) survival outcomes have been reported in patients with paraneoplastic neurological disorders (PNDs) associated with neuronal antibodies (Neur-Abs), but the presence of a PND might have expedited diagnosis. Our aim was to establish whether neuronal antibodies, independent of clinical neurological features, correlate with SCLC survival.

Experimental Design

262 consecutive SCLC patients were examined: of these, 24 with neurological disease were excluded from this study. The remaining 238 were tested for a broad array of Neur-Abs at the time of cancer diagnosis; survival time was established from follow-up clinical data.

Results

Median survival of the non-PND cohort (n = 238) was 9.5 months. 103 patients (43%) had one or more antigen-defined Neur-Abs. We found significantly longer median survival in 23 patients (10%) with HuD/anti-neuronal nuclear antibody type 1 (ANNA-1, 13.0 months P = 0.037), but not with any of the other antigen-defined antibodies, including the PND-related SOX2 (n = 56, 24%). An additional 28 patients (12%) had uncharacterised anti-neuronal nuclear antibodies (ANNA-U); their median survival time was longer still (15.0 months, P = 0.0048), contrasting with the survival time in patients with non-neuronal anti-nuclear antibodies (detected using HEp-2 cells, n = 23 (10%), 9.25 months). In multivariate analyses, both ANNA-1 and ANNA-U independently reduced the mortality hazard by a ratio of 0.532 (P = 0.01) and 0.430 (P<0.001) respectively.

Conclusions

ANNAs, including the newly described ANNA-U, may be key components of the SCLC immunome and have a potential role in predicting SCLC survival; screening for them could add prognostic value that is similar in magnitude to that of limited staging at diagnosis.

Microenvironment of tumor-draining lymph nodes: opportunities for liposome-based targeted therapy

The World Health Organization (WHO) recently reported that the total number of global cancer cases in 2013 reached 14 million, a 10% rise since 2008, while the total number of cancer deaths reached 8.2 million, a 5.2% increase since 2008. Metastasis is the major cause of death from cancer, accounting for 90% of all cancer related deaths. Tumor-draining lymph nodes (TDLN), the sentinel nodes, are the first organs of metastasis in several types of cancers. The extent of metastasis in the TDLN is often used in disease staging and prognosis evaluation in cancer patients. Here, we describe the microenvironment of the TDLN and review the recent literature on liposome-based therapies directed to immune cells within the TDLN with the intent to target cancer cells.

Effective cancer vaccine platform based on attenuated salmonella and a type III secretion system

Vaccines explored for cancer therapy have been based generally on injectable vector systems used to control foreign infectious pathogens, to which the immune system evolved to respond naturally. However, these vectors may not be effective at presenting tumor-associated antigens (TAA) to the immune system in a manner that is sufficient to engender antitumor responses. We addressed this issue with a novel orally administered Salmonella-based vector that exploits a type III secretion system to deliver selected TAA in the cytosol of professional antigen-presenting cells in situ. A systematic comparison of candidate genes from the Salmonella Pathogenicity Island 2 (SPI2) locus was conducted in the vaccine design, using model antigens and a codon-optimized form of the human TAA survivin (coSVN), an oncoprotein that is overexpressed in most human cancers. In a screen of 20 SPI2 promoter:effector combinations, a PsifB::sseJ combination exhibited maximal potency for antigen translocation into the APC cytosol, presentation to CD8 T cells, and murine immunogenicity. In the CT26 mouse model of colon carcinoma, therapeutic vaccination with a lead PsifB::sseJ-coSVN construct (p8032) produced CXCR3-dependent infiltration of tumors by CD8 T cells, reversed the CD8:Treg ratio at the tumor site, and triggered potent antitumor activity. Vaccine immunogenicity and antitumor potency were enhanced by coadministration of the natural killer T-cell ligand 7DW8-5, which heightened the production of IL12 and IFNγ. Furthermore, combined treatment with p8032 and 7DW8-5 resulted in complete tumor regression in A20 lymphoma-bearing mice, where protective memory was demonstrated. Taken together, our results demonstrate how antigen delivery using an oral Salmonella vector can provide an effective platform for the development of cancer vaccines.

Bystander killing of cancer requires the cooperation of CD4(+) and CD8(+) T cells during the effector phase

Killing of nonmalignant stroma requires cooperation between CD4⁺ and CD8⁺ T cells during the effector phase in the tumor microenvironment.

Cancers frequently evade cytotoxic T lymphocyte–mediated destruction through loss or down-regulation of tumor antigens and antigen-presenting major histocompatibility complex molecules. Therefore, we have concentrated our efforts on immunological strategies that destroy nonmalignant stromal cells essential for the survival and growth of cancer cells. In this study, we developed a non–T cell receptor transgenic, immunocompetent tumor model to determine whether tumor-bearing hosts’ own immune systems could eliminate cancer cells through stromal targeting and what role CD4⁺ T cells play alongside CD8⁺ T cells in this process. We found that aggressive cancers could be eradicated by T cell targeting of tumor stroma. However, successful elimination required the cooperation of CD4⁺ and CD8⁺ T cells not only during the induction phase but also during the effector phase in the tumor microenvironment, implying a new role for CD4⁺ T cells that has not been previously described. Our study demonstrates the potential of stromal targeting as a cancer immunotherapy and suggests that successful anticancer strategies must facilitate cooperation between CD4⁺ and CD8⁺ T cells at the right times and the right places.

Evidence for immunosurveillance in intestinal premalignant lesions

The immunosurveillance theory argues that the immune system recognizes tumour-specific antigens expressed by transformed cells, which results in the destruction of cancer precursors before they become clinically manifest. As a model for the development of cancer, we set out to study premalignant lesions and immune responses in sentinel lymph nodes from patients with long-standing ulcerative colitis and progression of mucosal dysplasia. Mesenteric lymph nodes draining dysplastic and normal intestinal segments were identified by sentinel node technique during surgery in 13 patients with ulcerative colitis who were subjected to colectomy because of intestinal dysplasia. T cells were extracted from the lymph nodes and analysed by flow cytometry, and lymphocyte proliferation assays were set up in the presence of extracts from dysplastic and normal intestinal mucosa. Increase in CD4/CD8 ratio was observed in sentinel lymph nodes draining dysplastic epithelium compared to normal mucosa. The increase in CD4(+) T cells in relation to CD8(+) T cells correlated with the degree of dysplasia reflected by a significant increase in the ratio against low-grade dysplasia compared to indefinite dysplastic lesions. The T-cell response was specific to antigens from dysplastic epithelial lining as seen in proliferation assays. The observation suggests an important surveillance role for the immune system against premalignant intestinal lesions in patients with long-standing ulcerative colitis.

Novel cancer vaccine based on genes of Salmonella pathogenicity island 2

Although tumors express potentially immunogenic tumor-associated antigens (TAAs), cancer vaccines often fail because of inadequate antigen delivery and/or insufficient activation of innate immunity. Engineering nonpathogenic bacterial vectors to deliver TAAs of choice may provide an efficient way of presenting TAAs in an immunogenic form. In this study, we used genes of Salmonella pathogenicity island 2 (SPI2) to construct a novel cancer vaccine in which a TAA, survivin, was fused to SseF effector protein and placed under control of SsrB, the central regulator of SPI2 gene expression. This construct uses the type III secretion system (T3SS) of Salmonella and allows preferential delivery of tumor antigen into the cytosol of antigen-presenting cells for optimal immunogenicity. In a screen of a panel of attenuated strains of Salmonella, we found that a double attenuated strain of Salmonella typhimurium, MvP728 (purD/htrA), was not toxic to mice and effectively expressed and translocated survivin protein inside the cytosol of murine macrophages. We also found that a ligand for CD1d-reactive natural killer T (NKT) cells, alpha-glucuronosylceramide (GSL1), enhanced MvP728-induced interleukin-12 production in human dendritic cells and that in vivo coadministration of a NKT ligand with MvP728-Llo or MvP728-survivin enhanced effector-memory cytotoxic T lymphocyte (CTL) responses. Furthermore, combined use of MvP728-survivin with GSL1 produced antitumor activity in mouse models of CT26 colon carcinoma and orthotopic DBT glioblastoma. Therefore, the use of TAA delivery via SPI-2-regulated T3SS of Salmonella and NKT ligands as adjuvants may provide a foundation for new cancer vaccines.

Manipulation of indoleamine 2,3 dioxygenase; a novel therapeutic target for treatment of diseases

BACKGROUND

The discovery of indoleamine 2,3-dioxygenase (IDO) as a modulator for the maintenance of fetomaternal immuno-privileged state has been heralded as a significant step in further defining the role of IDO in immunobiology. IDO is an IFN-inducible, intracellular enzyme that catalyzes the initial and rate-limiting step in the degradation of the essential amino acid, tryptophan. It has been suggested that IDO has the capacity to regulate the immune system via two discrete mechanisms; firstly the deprivation of tryptophan, which is essential for T cell proliferation and via the cytotoxic effects of tryptophan metabolites on T(H)1 cell survival.

METHODS

The sources of information used to prepare the paper are published work on Pubmed/Medline. In this review, we examine the therapeutic role of modulating IDO activity a variety of disease states including tumour tolerance, chronic infection, transplant rejection, autoimmunity and asthma. We propose that IDO represents a novel therapeutic target for the treatment of these diseases. We also explore the diverse strategies which are being employed, either to augment or to inhibit IDO activity in order to modify various disease processes. The limitations associated with these strategies are also scrutinized.

Effect of B7.1 costimulation on T-cell based immunity against TAP-negative cancer can be facilitated by TAP1 expression

Tumors deficient in expression of the transporter associated with antigen processing (TAP) usually fail to induce T-cell-mediated immunity and are resistant to T-cell lysis. However, we have found that introduction of the B7.1 gene into TAP-negative (TAP⁻) or TAP1-transfected (TAP1⁺) murine lung carcinoma CMT.64 cells can augment the capacity of the cells to induce a protective immune response against wild-type tumor cells. Differences in the strength of the protective immune responses were observed between TAP⁻ and TAP1⁺ B7.1 expressing CMT.64 cells depending on the doses of γ-irradiated cell immunization. While mice immunized with either high or low dose of B7.1-expressing TAP1⁺ cells rejected TAP⁻ tumors, only high dose immunization with B7.1-expressing TAP⁻ cells resulted in tumor rejection. The induced protective immunity was T-cell dependent as demonstrated by dramatically reduced antitumor immunity in mice depleted of CD8 or CD4 cells. Augmentation of T-cell mediated immune response against TAP⁻ tumor cells was also observed in a virally infected tumor cell system. When mice were immunized with a high dose of γ-irradiated CMT.64 cells infected with vaccinia viruses carrying B7.1 and/or TAP1 genes, we found that the cells co-expressing B7.1 and TAP1, but not those expressing B7.1 alone, induced protective immunity against CMT.64 cells. In addition, inoculation with live tumor cells transfected with several different gene(s) revealed that only B7.1- and TAP1-coexpressing tumor cells significantly decreased tumorigenicity. These results indicate that B7.1-provoked antitumor immunity against TAP⁻ cancer is facilitated by TAP1-expression, and thus both genes should be considered for cancer therapy in the future.

Targeting tumors with LIGHT to generate metastasis-clearing immunity

Metastatic diseases cause the majority of morbidity and mortality of cancer patients. Established tumors form both physical and immunological barriers to limit immune detection and destruction. Current immunotherapy of vaccination and adoptive transfer shows limited effect at least in part due to the existing barriers in the tumors and depending on the knowledge of tumor antigens. Tumor necrosis factor (TNF) superfamily (TNFSF) member 14 (TNFSF14) LIGHT interacts with stromal cells, dendritic cells (DCs), NK cells, naïve and activated T cells and tumor cells inside the tumor tissues via its two functional receptors, HVEM and lymphotoxin beta receptor (LTbetaR). Targeting tumor tissues with LIGHT leads to augmentation of priming, recruitment, and retention of effector cells at tumor sites, directly or indirectly, to induce strong anti-tumor immunity to inhibit the growth of primary tumors as well as eradicate metastases. Intratumor treatment would break tumor barriers and allow strong immunity against various tumors without defining tumor antigens. This review summarizes recent findings to support that LIGHT is a promising candidate for an effective cancer immunotherapy.

Requirement of secondary lymphoid tissues for the induction of primary and secondary T cell responses against Listeria monocytogenes

Activation of naive T cells is tightly controlled and depends on cognate interactions with professional antigen-presenting cells. We analyzed dependency on secondary lymphoid tissues for the activation of naive and memory CD4(+) and CD8(+) T cells following primary and secondary Listeria monocytogenes infection, respectively. In splenectomized lymphotoxin-beta receptor-deficient mice, lacking all secondary lymphoid tissues, oral infection with L. monocytogenes failed to induce bacteria-specific CD4(+) and CD8(+) T cell responses. Treatment of splenectomized wild-type mice with FTY720, a drug that prevents egress of T cells from lymph nodes, also reduced T cell responses after oral L. monocytogenes infection and blocked T cell responses after intravenous infection. FTY720-treated wild-type and lymphotoxin-beta receptor-deficient mice show only slightly impaired recall responses. However, T cell responses were profoundly inhibited when mice were splenectomized subsequently to recovery from primary infection. T cell transfer experiments demonstrated that the impaired secondary T cell response was not simply due to removal of a large fraction of memory T cells by splenectomy. Overall, these results indicate that not only primary T cell responses, but also secondary T cell responses, highly depend on the lymphoid environment for effective activation.

In situ expression of IFN-gamma-inducible T cell alpha chemoattractant in breast cancer mounts an enhanced specific anti-tumor immunity which leads to tumor regression

Increased evidence indicates that chemokines are involved in tumor growth. ITAC, a key member of chemokines, possesses the ability to recruit T cells and enhance immune responses. Therefore, ITAC might contribute to antitumor immunity. In this study, we evaluated the relationship between the expression of ITAC and human breast cancer advancement. We further investigated whether forced expression of ITAC in tumor sites could mediate enhanced antitumor immunity in a murine breast cancer model. Results showed that ITAC expression level was down-regulated in 31 breast cancer specimens compared to normal mammary tissues, and associated negatively with the stages of breast cancer. Contrarily, forced expression of ITAC in murine 4T1 tumor cells resulted in tumor regression after initial growth upon injection into naïve Balb/c mice. More lymphocytes were recruited to the site of tumor inoculated by 4T1-ITAC and more than 80% of these T cells expressed the ITAC receptor, CXCR3. ITAC-recruited TILs exhibited 4T1-specific proliferation and cytotoxicity, and an increased IFN-gamma but decreased IL-4 production. Importantly, forced expression of ITAC in 4T1 tumor nodules inhibited tumor growth. These findings demonstrated that the decreased expression of ITAC is associated with the advancement of breast cancer in patients. Forced expression of ITAC in tumor site not only induces increased T cell-recruitment and elicits a specific antitumor immunity, but also mediates regression of established 4T1 tumors, indicating the potential application of ITAC-expressing tumor cells in cancer immunotherapy and vaccine designing.

Targeting the primary tumor to generate CTL for the effective eradication of spontaneous metastases

Metastatic disease is the major cause of morbidity and mortality in cancer. Although surgery, chemotherapy, or radiation can often control primary tumor growth, successful eradication of disseminated metastases remains rare. We have now tested whether direct targeting tumor tissues to generate antitumor immune response before surgical excision produces sufficient CTL against micrometastases. One unsolved problem is whether such response allows coming CTL to be educated and then exit the tumor site. Another unsolved problem is whether these CTL can then patrol and effectively eliminate spontaneously metastasized tumor cells in the periphery. In this study, we have shown that adenovirus-expressing TNFSF14 [LIGHT (name derived from homologous to lymphotoxins, shows inducible expression, and competes with herpes simplex virus glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes); Ad-LIGHT] inoculated directly into primary 4T1 tumor, a highly aggressive, spontaneously metastasizing mammary carcinoma, followed by surgical removal of the primary tumor can eradicate established and disseminated metastatic tumor cells in the peripheral tissues. Furthermore, we clearly show with a fibrosarcoma model Ag104L(d) that local treatment can generate plenty of tumor-specific CTL that exit the primary tumor and infiltrate distal tumors to completely eradicate distal tumors. Therefore, targeting the primary tumor with Ad-LIGHT before surgical excision is a new strategy to elicit better immune response for the eradication of spontaneous metastases.

Indoleamine 2,3-dioxygenase and tumor-induced tolerance

Tumors arise from normal cells of the body through genetic mutation. Although such genetic mutation often leads to the expression of abnormal antigens, the immune system fails to respond effectively to these antigens; that is, it is tolerant of these antigens. This acquired state of tolerance must be overcome for cancer immunotherapy to succeed. Indoleamine 2,3-dioxygenase (IDO) is one molecular mechanism that contributes to tumor-induced tolerance. IDO helps create a tolerogenic milieu in the tumor and the tumor-draining lymph nodes, both by direct suppression of T cells and enhancement of local Treg-mediated immunosuppression. It can also function as an antagonist to other activators of antitumor immunity. Therefore, strategies to block IDO might enhance the effectiveness of tumor immunotherapy.

Dendritic cell targeting of survivin protein in a xenogeneic form elicits strong CD4+ T cell immunity to mouse survivin

To determine whether strong CD4+ T cell immunity could be induced to a nonmutated self protein that is important for tumorigenesis, we selectively targeted the xenogeneic form of survivin, a survival protein overexpressed in tumors, to maturing dendritic cells in lymphoid tissues. Dendritic cell targeting via the DEC205 receptor in the presence of anti-CD40 and poly(I:C) as maturation stimuli, induced strong human and mouse survivin-specific CD4+ T cell responses, as determined by IFN-gamma, TNF-alpha, and IL-2 production, as well as the development of lytic MHC class II-restricted T cells and memory. Immunity was enhanced further by depletion of CD25+foxp3+ cells before vaccination. anti-DEC205-human survivin was superior in inducing CD4+ T cell responses relative to other approaches involving survivin plasmid DNA or survivin peptides with adjuvants. However, we were unable to induce CD8+ T cell immunity to survivin by two doses of DEC205-targeted survivin or the other strategies. Therefore, significant CD4+ T cell immunity to a self protein that is overexpressed in most human cancers can be induced by DEC205 targeting of the Ag in its xenogeneic form to maturing DCs.

Allogeneic retrovirally transduced, IL-2- and IFN-γ-secreting cancer cell vaccine in patients with hormone refractory prostate cancer—a phase I clinical trial

BACKGROUND

The purpose of this vaccine study was to determine the safety and feasibility of vaccination with an allogeneic prostate carcinoma cell line, LNCaP, expressing recombinant interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) and to evaluate the efficacy of inducing tumor-specific immune responses in HLA-A2-matched patients with hormone refractory prostate cancer (HRPC).

METHODS

In a dose-escalating phase I study, HLA-A2-matched HRPC patients received four vaccinations of irradiated allogeneic LNCaP cells retrovirally transduced to secrete IL-2 and IFN-gamma at study day 1, 15, 29 and 92 and subsequently every 91 days unless tumor progression was evident.

RESULTS

Three patients receiving the first dose level (7.5 million cells) showed no evidence of dose-limiting toxicity or vaccine-related adverse events including autoimmunity. One of three patients receiving the second dose level (15 million cells) developed a transient self-limiting grade 3 local injection site reaction (ulceration) after the eighth vaccination. Vaccine-induced immune responses against a broad array of prostate tumor associated antigens were detected in all six patients. Two of the three patients receiving the higher dose showed a decline in serum prostate-specific antigen (PSA) values of more than 50%, with one patient remaining on protocol for 3 years.

CONCLUSIONS

Immunisation with the allogeneic LNCaP/IL-2/IFN-gamma vaccine is safe and feasible without any dose-limiting toxicity or autoimmunity. A 50% PSA decline was achieved in two of the six patients. This encouraging data provides the scientific rationale for further investigation of the vaccine in a phase II trial.

The tumor-draining lymph node as an immune-privileged site

Lymph nodes that lie immediately downstream of tumors [tumor-draining lymph nodes (TDLNs)] undergo profound alterations due to the presence of the upstream tumor. The antigen-presenting cell population in TDLNs becomes modified such that tumor-derived antigens are cross-presented by host cells in a tolerizing fashion. In addition, the number and suppressor activity of regulatory T cells (Tregs) are increased in the TDLN. Emerging evidence suggests that some of these Tregs may be generated de novo against specific tumor-derived antigens, and thus they arise as a direct consequence of antigen presentation in the TDLN. Others may represent Tregs against self-antigens, which undergo preferential activation in the tolerogenic milieu of the TDLN. The TDLN thus becomes an anatomic context in which presentation of new antigens not only fails to elicit a protective immune response but also actively creates systemic tolerance. In this regard, the TDLN displays features analogous to classical immune privilege. Accumulating evidence thus suggests that the TDLNs, although small in size, may exert a profound tolerizing influence on the rest of the immune system. These mechanisms will need to be interrupted in order for clinical anti-tumor immunotherapy to be successful.

Cyclooxygenase-2 inhibition promotes enhancement of antitumor responses by transcutaneous vaccination with cytosine-phosphate-guanosine-oligodeoxynucleotides and model tumor antigen

One of the principal goals in tumor immune prophylaxis and tumor therapy is the induction of antitumor responses by generating sufficient numbers of tumor antigen-specific helper T (Th)1 cells and cytotoxic T lymphocytes (CTLs). We have demonstrated that the administration of cytosine-phosphate-guanosine-oligodeoxynucleotide (CpG-ODN) through tape-stripped skin induced a Th1-type immune response and suggested that the skin is a potential site for vaccination. CpG-ODN induces the expression of cyclooxygenase (COX)-2, and its product prostaglandin (PG) E2 underlies an immunosuppressive network, therefore it is a simple strategy to use a COX-2 inhibitor for tumor vaccination with CpG-ODN. In this study, we examined whether a COX-2 inhibitor enhances the antitumor immune response induced by CpG-ODN with model tumor antigen, ovalbumin (OVA), applied to tape-stripped skin in mice. The COX-2 inhibitor remarkably enhanced antigen-specific Th1-type immune responses and generation of CTLs induced by transcutaneous vaccination with CpG-ODN and OVA. PGE2 and IL-10 levels in the skin were significantly decreased and production of IL-12 was enhanced. This vaccination also induces an effective antitumor immunity in tumor-challenged mice. These results suggested that transcutaneous vaccination with a COX-2 inhibitor, CpG-ODN, and tumor antigen is a very simple and cost-effective strategy for tumor vaccine and may be readily achievable.

Endoglin (CD105) is a target for an oral DNA vaccine against breast cancer

Endoglin (CD105), a co-receptor in the TGF-beta receptor complex, is over-expressed on proliferating endothelial cells in the breast tumor neovasculature and thus offers an attractive target for anti-angiogenic therapy. Here we report the anti-angiogenic/anti-tumor effects achieved in a prophylactic setting with an oral DNA vaccine encoding murine endoglin, carried by double attenuated Salmonella typhimurium (dam-, AroA-) to a secondary lymphoid organ, i.e., Peyer's patches . We demonstrate that an endoglin vaccine elicited activation of antigen-presenting dendritic cells, coupled with immune responses mediated by CD8+ T cells against endoglin-positive target cells. Moreover, we observed suppression of angiogenesis only in mice administered with the endoglin vaccine as compared to controls. These data suggest that a CD8+ T cell-mediated immune response induced by this vaccine effectively suppressed dissemination of pulmonary metastases of D2F2 breast carcinoma cells presumably by eliminating proliferating endothelial cells in the tumor vasculature. It is anticipated that vaccine strategies such as this may contribute to future therapies for breast cancer.

Ii-Key/MHC class II epitope hybrids: a strategy that enhances MHC class II epitope loading to create more potent peptide vaccines

Life-threatening diseases, such as cancer and pandemic influenza, demand new efforts towards effective vaccine design. Peptides represent a simple, safe and adaptable basis for vaccine development; however, the potency of peptide vaccines is insufficient in most cases for significant therapeutic efficacy. Several methods, such as Ligand Epitope Antigen Presentation System and ISCOMATRIX, have been developed to enhance the potency of peptide vaccines. One way of increasing the loading of MHC class II peptides occurs through the use of Ii-Key technology. Ii-Key (LRMK), a portion of the MHC class II-associated invariant chain (Ii), facilitates the direct loading of epitopes to the MHC class II molecule groove. Linking the Ii-Key moiety via a simple polymethylene bridge to an MHC class II epitope, to generate an Ii-Key/MHC class II epitope hybrid, greatly enhances the vaccine potency of the tethered epitope. The combination of such Ii-Key/MHC class II epitope hybrids with MHC class I epitope-containing peptides might generate a potent peptide vaccine for malignancies and infectious diseases. The Ii-Key hybrid technology is compared with other methods that enhance the potency of a peptide vaccine.

CD8 T cell recall responses are regulated by the tissue tropism of the memory cell and pathogen

Whether memory CD8 T cells can be reactivated in nonlymphoid tissues is unclear. Using mice lacking the spleen, lymph nodes, or both, we show that the secondary T cell response, but not homeostatic maintenance of memory cells, required lymphoid tissue. Whereas primary and secondary CD8 T cell responses to vesicular stomatitis virus infection were lymph node dependent, responses to Listeria monocytogenes infection were driven primarily in the spleen. Memory cell subset reactivation was also regulated by location of the responding population and the pathogen. Thus, CD62Llow effector memory T cells (TEM) cells responded nearly as well as CD62Lhigh central memory T cells (TCM) and TCM cells after L. monocytogenes infection, and both subsets generated equivalent populations of secondary memory cells. In contrast, TCM cells, but not TEM cells, mounted a robust response to vesicular stomatitis virus infection. TCM and TEM cells also required lymphoid tissue to mount recall responses, and the bone marrow did not contribute significantly to the response of either subset. Our findings indicated that characteristics of the infectious agent and the migratory preferences of memory cells dictated the secondary lymphoid tissue requirement for the recall response to infection.

Regulation of allergic airway inflammation by class I-restricted allergen presentation and CD8 T-cell infiltration

BACKGROUND

CD8 T cells are known to respond to exogenous antigens through cross-presentation. The importance of the CD8 cell response in the lung after inhalation of allergen and its effects on asthmatic inflammation are less clear.

OBJECTIVE

We sought to determine the dynamics, nature, and immunoregulatory activities of the class I CD8 T-cell response to inhaled allergen.

METHODS

We studied a murine model of respiratory allergen sensitization, adoptive transfer of transgenic T cells, and flow cytometric analysis of lung infiltrates.

RESULTS

Class I-restricted CD8 T cells responded rapidly to inhaled allergen and dominated the acute infiltration of T cells into the lung after secondary exposure. CD8 cells in the lung expressed a type 1 phenotype and suppressed the systemic IgE response to subsequent immunization. Dendritic cells purified from conducting airways or lung tissue were highly efficient at cross-presentation of antigen into the class I pathway after intranasal challenge. Adoptive transfer of transgenic antigen-specific CD8, but not CD4, cells resulted in increased IL-12 levels and reduced IL-13 and IL-5 levels in bronchoalveolar lavage fluid, coupled with substantially reduced airway eosinophilia after repeated allergen inhalation, a process mimicked by intranasal administration of IL-12 and inhibited by anti-IL-12 antibody.

CONCLUSION

The data suggest that CD8 cells specific for inhaled allergens are generated in draining lymph nodes but suppress allergic airway inflammation through induction of IL-12 in the lung during interaction with respiratory dendritic cells.

CLINICAL IMPLICATIONS

Novel peptide immunotherapeutics targeting the class I-restricted CD8 T-cell response to allergen represent a promising strategy for extrinsic asthma.

Effects of the tumor microenvironment on the efficacy of tumor immunotherapy

Cancer immunotherapy utilizes vaccines targeting tumor antigens or tumor endothelium to prevent or regress tumors. Many cancer vaccines are designed to induce antigen-specific effector T cells that migrate to the tumor site. In an optimal situation, the effector T cells penetrate the tumor, release their effector molecules, induce tumor cell death and tumor regression. However, the tumor microenvironment is frequently immunosuppressive and contributes to a state of immune ignorance, impacting on the vaccine's ability to break tolerance to tumor antigen/s. This review discusses the factors in the tumor microenvironment that can affect the efficacy of cancer vaccines. In particular, the review focuses on pathways leading to effector T cell penetration of tumors or the inhibition of this process.

Toll-like receptor-9 expression induced by tape-stripping triggers on effective immune response with CpG-oligodeoxynucleotides

Recently, there has been a lot of interest in the potential of non-invasive routes, such as via the skin, for vaccine delivery. CpG-oligodeoxynucleotides (ODN) are an effective adjuvant for the induction of cellular and humoral immunities when administered with an antigen. We demonstrated here that tape-stripping induces the expression of toll-like receptor (TLR)-9 in the skin, and enhances the Th1-type immune response triggered by CpG-ODN administered through the tape-stripped skin. Tape-stripping induces expression of TLR-9 and tumor necrosis factor (TNF)-alpha in the skin, and CpG-ODN treatment through the tape-stripped skin enhances the migration of antigen presenting cells (APCs) to the draining lymph nodes. On the other hand, TLR-9 mRNA and TNF-alpha mRNA were not observed in the skin when CpG-ODN was injected intradermally in a volume of 10 microL, or in a Th1-type immune response. The transdermal application of CpG-ODN with an antigen through the tape-stripped skin is an effective way to induce a Th1-type immune response, and is also a simple, cost-effective and needle-free vaccination system.

Targeted in vivo expression of IFN-gamma-inducible protein 10 induces specific antitumor activity

Although it is known that the chemoattractant effect of IFN-gamma inducible protein 10 (IP-10), a CXC chemokine (CXCL10), plays an important role in T cell-mediated antitumor immunity in vivo, whether IP-10 is involved in modulating the proliferation, survival and functional activation of tumor-specific T cells remains poorly investigated. Using an experimental mouse tumor model, we demonstrated that the in vivo growth of 4T1 tumor cells harboring IP-10 gene (4T1-IP-10) was inhibited. Mice inoculated with 4T1-IP-10 tumor cells expressing functional IP-10 survived over 90 days, whereas mice injected with control parental 4T1 cells and mice of control 4T1 cells transduced with control plasmid all succumbed to the tumor by day 38 after tumor inoculation. Mechanical analysis showed that targeted expression of IP-10 in 4T1 tumor cells markedly enhanced the infiltration of tumor-specific T cells into the 4T1-IP-10 tumor. These tumor infiltrating T lymphocytes (TILs) recruited by IP-10 were potent cytolytic killers against 4T1 tumor cells and were able to proliferate and produce high levels of IFN-gamma in response to 4T1 cells. In vivo administration of IP-10-recruited TILs induced vigorous proliferation of these TILs in situ in the 4T1-IP-10 tumor but not in the 4T1-pcDNA3 and parental 4T1 tumors. Furthermore, culture of TILs together with recombinant IP-10 significantly enhanced the proliferation and expansion of IP-10-recruited TILs in response to 4T1 tumor antigens. These results suggest that IP-10 is not only able to chemoattract tumor-specific T cells into the local tissue, but also enhance the proliferation, survival, and functional activation of these TILs, leading to the tumor regression. Thus, targeted expression of IP-10 in vivo will allow for the development of a novel approach for immunotherapy of tumor.

Future directions for vaccine-based therapies

During recent years, cancer vaccines have made encouraging progress toward becoming a clinically relevant form of biologic therapy. However, current vaccine approaches have shown only limited success in patients with cancer because of inadequate immune activation. Recent insights into the elements that regulate immune responsiveness have provided new opportunities to enhance the efficacy of cancer vaccines through multiple pathways that involve afferent and efferent arms of the immune system. This article presents a set of emerging strategies that have resulted from our recent efforts to boost tumor-associated antigen-specific immunity and improve patient outcome. These new insights represent important consideration for the design and development of more effective immunotherapies during the next decade.

Principles of dendritic cell-based immunotherapy in myeloid leukemia

Persistent presence of minimal residual disease in myeloid leukemia carries the risk of a relapse of the disease. In the setting of allogeneic transplants, leukemic cells have been proven to be susceptible to the action of immunocompetent T cells. Thus, an immunotherapeutic approach might hold promise in the attempt to eradicate or control residual leukemia cells. Dendritic cells (DCs) are very potent stimulators of immune responses and these cells have been widely used to target other types of malignancies. This review discusses the function and the applicability of leukemia-derived DCs for active specific immunotherapy in myeloid leukemia including possible pitfalls, and describes options to optimize DC-based vaccines.

Tumor-infiltrating T lymphocytes: friends or foes?

The prognostic significance of tumor-infiltrating lymphocytes (TILs) has been a longstanding topic of debate. In cases where TILs have improved patient outcome, T lymphocytes are recognized as the main effectors of antitumor immune responses. However, recent studies have revealed that a subset of CD4(+) T cells, referred to as CD4(+)CD25(+) regulatory T cells (Treg), may accumulate in the tumor environment and suppress tumor-specific T-cell responses, thereby hindering tumor rejection. Hence, predicting tumor behavior on the basis of an indiscriminate evaluation of tumor-infiltrating T cells may result in inconsistent prognostic accuracy. The presence of infiltrating CD4(+)CD25(+) Treg may be detrimental to the host defense against the tumor, while the presence of effector T lymphocytes, including CD8(+) T cells and non-regulatory CD4(+) helper T cells may be beneficial. Enhanced recruitment of antitumor effector T lymphocytes to tumor tissue in addition to inhibition of local Treg, may therefore be an ideal target for improving cancer immunotherapy. This article reviews the antitumor functions of T-lymphocytes, with special attention given to CD4(+) regulatory T-cells within the tumor environment.

Innate NKT lymphocytes confer superior adaptive immunity via tumor-capturing dendritic cells

If irradiated tumor cells could be rendered immunogenic, they would provide a safe, broad, and patient-specific array of antigens for immunotherapies. Prior approaches have emphasized genetic transduction of live tumor cells to express cytokines, costimulators, and surrogate foreign antigens. We asked if immunity could be achieved by delivering irradiated, major histocompatibility complex–negative plasmacytoma cells to maturing mouse dendritic cells (DCs) within lymphoid organs. Tumor cells injected intravenously (i.v.) were captured by splenic DCs, whereas subcutaneous (s.c.) injection led only to weak uptake in lymph node or spleen. The natural killer T (NKT) cells mobilizing glycolipid α-galactosyl ceramide, used to mature splenic DCs, served as an effective adjuvant to induce protective immunity. This adjuvant function was mimicked by a combination of poly IC and agonistic αCD40 antibody. The adjuvant glycolipid had to be coadministered with tumor cells i.v. rather than s.c. Specific resistance was generated both to a plasmacytoma and lymphoma. The resistance afforded by a single vaccination lasted >2 mo and required both CD4⁺ and CD8⁺ T cells. Mature tumor capturing DCs stimulated the differentiation of P1A tumor antigen-specific, CD8⁺ T cells and uniquely transferred tumor resistance to naive mice. Therefore, the access of dying tumor cells to DCs that are maturing to activated NKT cells efficiently induces long-lived adaptive resistance.

An Essential Role of Antigen-Presenting Cell/T-Helper Type 1 Cell-Cell Interactions in Draining Lymph Node during Complete Eradication of Class II–Negative Tumor Tissue by T-Helper Type 1 Cell Therapy

Prior studies have shown that transfer of ovalbumin (OVA)-specific T helper type 1 (Th1) cells into mice bearing MHC class II+ OVA-expressing tumor cells (A20-OVA) causes complete tumor rejection. Here we show that, although Th1 cell therapy alone was not effective against MHC class II- OVA-expressing tumor cells (EG-7), treatment of mice bearing established EG-7 tumors by i.v. transfer of Th1 cells combined with i.t. injection of the model tumor antigen OVA induced complete tumor rejection. Transferred Th1 cells enhanced the migration of tumor-infiltrating antigen-presenting cells (APC) that had processed OVA into the draining lymph node (DLN). Although transferred Th1 cells were randomly distributed in DLN, distal LN, spleen, and tumor tissue, active proliferation of Th1 cells always initiated in DLN, where Th1 cells efficiently interacted with APC that presented OVA. In parallel, OVA-tetramer+ CTLs, showing EG-7-specific cytotoxicity, were highly induced in DLN and the local tumor site. The OVA-tetramer+ CTL functioned systemically because two bilateral tumor masses were both completely rejected on treatment of one tumor. Furthermore, either active proliferation of transferred Th1 cells or generation of tetramer+ CTL was not induced in MHC class II-deficient mice and LN-deficient Aly/Aly mice. These results indicate that DLN is an indispensable organ for initiating active APC/Th1 cell interactions, which is critical for inducing complete eradication of tumor mass by tumor-specific CTL.

Vaccination with IFN-inducible T cell alpha chemoattractant (ITAC) gene-modified tumor cell attenuates disseminated metastases of circulating tumor cells

Immunotherapeutic strategies for metastatic diseases are being developed. IFN-inducible T cell alpha chemoattractant (ITAC) has been demonstrated to be able to induce Th1-type immune response. However, the effects of ITAC on the tumor metastasis have not been fully understood. In the present study, the ITAC-modified tumor cell vaccine in inhibiting the disseminated pulmonary metastasis was evaluated. ITAC-modified tumor cell vaccine 4T1-ITAC was developed by stably transfecting 4T1 cells with pcDNA3-ITAC plasmid. Mice were vaccinated with 4T1-ITAC. Mice vaccinated with 4T1-pcDNA3 and 4T1 were used as controls. Specific cellular immune responses against 4T1 were tested by in vitro proliferation, cytokine production and cytotoxic assay. The number of clonogenic metastatic tumor cells and metastatic forci on the surface of lung were counted by histological examination. Results showed that a significant enhancement of proliferative and cytotoxic activities accompanied with increased IFN-gamma and TNF-alpha production as well as decreased IL-4 production were obtained from the mice vaccinated with 4T1-ITAC. The number of clonogenic metastatic tumor cells in the mice vaccinated with 4T1-ITAC cells reduced markedly and no visible metastasis was found in the lungs of the 4T1-ITAC vaccinated mice. Consequently, the survival rate was dramatically increased in these mice. Taken together, our results demonstrated that ITAC-modified tumor cell vaccine can enhance the anti-tumor immunity and reduce the incidence of disseminated metastasis.

Natural Killer Cells License Dendritic Cell Cross-Presentation of B Lymphoma Cell–Associated Antigens

PURPOSE

Presentation of exogenous antigen by MHC class I molecules, or cross-presentation, is a property of dendritic cells, which is considered crucial for the priming of cytotoxic T-cell response to tumor antigens. However, the precise mechanisms of this process are not fully understood.

EXPERIMENTAL DESIGN AND RESULTS

We show here in a human in vitro system, using B lymphoma cells as a tumor model, that the cross-presentation of cell-associated antigens to T cells by dendritic cells requires "help" from natural killer cells. When autologous dendritic cells that had taken up apoptotic B lymphoma cells and induced to a fully mature state were used to stimulate nonadherent cells of peripheral blood mononuclear cells from healthy donors, they induced strong cytotoxicity against B lymphoma cells in a HLA-A0201-restricted manner. The cells failed to induce cytotoxicity, however, when purified T cells were used as effector cells. Depletion of CD56+ cells, but not CD14+ or CD19+ cells, abrogated the cytotoxicity of nonadherent cells, showing that the help was provided by natural killer cells. Further, when natural killer cells were present in the cultures, a strong and persistent production of interleukin-18, but not interleukin-12 and interleukin-15, was observed. Blocking interleukin-18 significantly reduced the cytotoxicity of nonadherent cells against B lymphoma cells.

CONCLUSIONS

These results suggest that capture of tumor cells and a full maturation status of dendritic cells are not sufficient to cross-prime CD8 T cells. Effective cross-priming requires further activation of dendritic cells by natural killer cells and an abundant production of interleukin-18, which, along with other yet undefined mechanisms, contribute to the generation of CTL response against B-cell lymphoma.

Generation of antifungal effector CD8+ T cells in the absence of CD4+ T cells during Cryptococcus neoformans infection

Immunity to the opportunistic fungus Cryptococcus neoformans is dependent on cell-mediated immunity. Individuals with defects in cellular immunity, CD4(+) T cells in particular, are susceptible to infection with this pathogen. In host defense against a number of pathogens, CD8(+) T cell responses are dependent upon CD4(+) T cell help. The goal of these studies was to determine whether CD4(+) T cells are required for the generation of antifungal CD8(+) T cell effectors during pulmonary C. neoformans infection. Using a murine intratracheal infection model, our results demonstrated that CD4(+) T cells were not required for the expansion and trafficking of CD8(+) T cells to the site of infection. CD4(+) T cells were also not required for the generation of IFN-gamma-producing CD8(+) T cell effectors in the lungs. In CD4(-) mice, depletion of CD8(+) T cells resulted in increased intracellular infection of pulmonary macrophages by C. neoformans, increasing the pulmonary burden of the infection. Neutralization of IFN-gamma in CD4(-)CD8(+) mice similarly increased macrophage infection by C. neoformans, thereby blocking the protection provided by CD8(+) T cells. Altogether, these data support the hypothesis that effector CD8(+) T cell function is independent of CD4(+) T cells and that IFN-gamma production from CD8(+) T cells plays a role in controlling C. neoformans by limiting survival of C. neoformans within macrophages.

NK cells help to induce CD8(+)-T-cell immunity against Toxoplasma gondii in the absence of CD4(+) T cells

CD8(+) T-cell immunity plays an important role in protection against intracellular infections. Earlier studies have shown that CD4(+) T-cell help was needed for launching in vivo CD8(+) T-cell activity against these pathogens and tumors. However, recently CD4(+) T-cell-independent CD8 responses during several microbial infections including those with Toxoplasma gondii have been described, although the mechanism is not understood. We now demonstrate that, in the absence of CD4(+) T cells, T. gondii-infected mice exhibit an extended NK cell response, which is mediated by continued interleukin-12 (IL-12) secretion. This prolonged NK cell response is critical for priming parasite-specific CD8(+) T-cell immunity. Depletion of NK cells inhibited the generation of CD8(+) T-cell immunity in CD4(-/-) mice. Similarly neutralization of IL-12 reduces NK cell numbers in infected animals and leads to the down-regulation of CD8(+) T-cell immunity against T. gondii. Adoptive transfer of NK cells into the IL-12-depleted animals restored their CD8(+) T-cell immune response, and animals exhibited reduced mortality. NK cell gamma interferon was essential for cytotoxic T-lymphocyte priming. Our studies for the first time demonstrate that, in the absence of CD4(+) T cells, NK cells can play an important role in induction of primary CD8(+) T-cell immunity against an intracellular infection. These observations have therapeutic implications for immunocompromised individuals, including those with human immunodeficiency virus infection.

Caspase-3-dependent beta-cell apoptosis in the initiation of autoimmune diabetes mellitus

beta-Cell apoptosis is a key event contributing to the pathogenesis of type 1 diabetes mellitus. In addition to apoptosis being the main mechanism by which beta cells are destroyed, beta-cell apoptosis has been implicated in the initiation of type 1 diabetes mellitus through antigen cross-presentation mechanisms that lead to beta-cell-specific T-cell activation. Caspase-3 is the major effector caspase involved in apoptotic pathways. Despite evidence supporting the importance of beta-cell apoptosis in the pathogenesis of type 1 diabetes, the specific role of caspase-3 in this process is unknown. Here, we show that Caspase-3 knockout (Casp3(-/-) mice were protected from developing diabetes in a multiple-low-dose streptozotocin autoimmune diabetes model. Lymphocyte infiltration of the pancreatic islets was completely absent in Casp3(-/-) mice. To determine the role of caspase-3-dependent apoptosis in disease initiation, a defined antigen-T-cell receptor transgenic system, RIP-GP/P14 double-transgenic mice with Casp3 null mutation, was examined. beta-cell antigen-specific T-cell activation and proliferation were observed only in the pancreatic draining lymph node of RIP-GP/P14/Casp3(+/-) mice, but not in mice lacking caspase-3. Together, our findings demonstrate that caspase-3-mediated beta-cell apoptosis is a requisite step for T-cell priming, a key initiating event in type 1 diabetes.

Intratumor depletion of CD4+ cells unmasks tumor immunogenicity leading to the rejection of late-stage tumors

Tumor environment can be critical for preventing the immunological destruction of antigenic tumors. We have observed a selective accumulation of CD4(+)CD25(+) T cells inside tumors. In a murine fibrosarcoma L(d)-expressing Ag104, these cells made up the majority of tumor-infiltrating lymphocytes at the late stage of tumor progression, and their depletion during the effector phase, rather than priming phase, successfully enhanced antitumor immunity. We show here that CD4(+)CD25(+) T cells suppressed the proliferation and interferon-gamma production of CD8(+) T cells in vivo at the local tumor site. Blockade of the effects of IL-10 and TGF-beta partially reversed the suppression imposed by the CD4(+) cells. Furthermore, local depletion of CD4(+) cells inside the tumor resulted in a change of cytokine milieu and led to the eradication of well-established highly aggressive tumors and the development of long-term antitumor memory. Therefore, CD4(+)CD25(+) T cells maintained an environment in the tumor that concealed the immunogenicity of tumor cells to permit progressive growth of antigenic tumors. Our study illustrates that the suppression of antitumor immunity by regulatory T cells occurs predominantly at the tumor site, and that local reversal of suppression, even at a late stage of tumor development, can be an effective treatment for well-established cancers.

Homing phenotypes of tumor-specific CD8 T cells are predetermined at the tumor site by crosspresenting APCs

Expression of tissue-specific homing molecules directs antigen-experienced T cells to particular peripheral tissues. In studies using soluble antigens that focused on skin and gut, antigen-presenting cells (APCs) within regional lymphoid tissues were proposed to be responsible for imprinting homing phenotypes. Whether this occurs in other sites and after physiologic antigen processing and presentation is unknown. We define in vivo imprinting of distinct homing phenotypes on monospecific T cells responding to antigens expressed by tumors in intracerebral, subcutaneous, and intraperitoneal sites with efficient brain-tropism of CD8 T cells crossprimed in the cervical lymph nodes (LNs). Multiple imprinting programs could occur simultaneously in the same LN when tumors were present in more than one site. Thus, the identity of the LN is not paramount in determining the homing phenotype; this critical functional parameter is dictated upstream at the site of antigen capture by crosspresenting APCs.

Cutting edge: persistence of transferred lymphocyte clonotypes correlates with cancer regression in patients receiving cell transfer therapy

The lack of persistence of transferred autologous mature lymphocytes in humans has been a major limitation to the application of effective cell transfer therapies. The results of a pilot clinical trial in 13 patients with metastatic melanoma suggested that conditioning with nonmyeloablative chemotherapy before adoptive transfer of activated tumor-reactive T cells enhances tumor regression and increases the overall rates of objective clinical responses. The present report examines the relationship between T cell persistence and tumor regression through analysis of the TCR beta-chain V region gene products expressed in samples obtained from 25 patients treated with this protocol. Sequence analysis demonstrated that there was a significant correlation between tumor regression and the degree of persistence in peripheral blood of adoptively transferred T cell clones, suggesting that inadequate T cell persistence may represent a major factor limiting responses to adoptive immunotherapy.