Building better vaccines: how apoptotic cell death can induce inflammation and activate innate and adaptive immunity

Cancer vaccine strategies using self-replicating RNA viral platforms

The development and success of RNA-based vaccines targeting SARS-CoV-2 has awakened new interest in utilizing RNA vaccines against cancer, particularly in the emerging use of self-replicating RNA (srRNA) viral vaccine platforms. These vaccines are based on different single-stranded RNA viruses, which encode RNA for target antigens in addition to replication genes that are capable of massively amplifying RNA messages after infection. The encoded replicase genes also stimulate innate immunity, making srRNA vectors ideal candidates for anti-tumor vaccination. In this review, we summarize different types of srRNA platforms that have emerged and review evidence for their efficacy in provoking anti-tumor immunity to different antigens. These srRNA platforms encompass the use of naked RNA, DNA-launched replicons, viral replicon particles (VRP), and most recently, synthetic srRNA replicon particles. Across these platforms, studies have demonstrated srRNA vaccine platforms to be potent inducers of anti-tumor immunity, which can be enhanced by homologous vaccine boosting and combining with chemotherapies, radiation, and immune checkpoint inhibition. As such, while this remains an active area of research, the past and present trajectory of srRNA vaccine development suggests immense potential for this platform in producing effective cancer vaccines.

A Novel Rabies Vaccine Based on a Recombinant Bovine Herpes Virus Type 1 Expressing Rabies Virus Glycoprotein

Rabies is a highly prevalent zoonotic disease and a public health threat worldwide. Currently licensed rabies vaccines are effective but less is known which would protect cattle. This study describes the construction of a novel recombinant bovine herpes virus type I (BHV-1) expressing rabies virus glycoprotein (RABV G) instead of its gE glycoprotein (gE) by CRISPR-Cas9 and homologous recombination technology (BHV-1-ΔgE-G). Insertion of the RABV G gene is stable after 20 rounds of in vitro passaging and the recombinant virus replicates to high titers in MDBK cells. The RABV G expresses in the recombinant virus-infected cells and on the virion surface of BHV-1-ΔgE-G. One single immunization with BHV-1-ΔgE-G-activated dendritic cells (DCs) and B cells furthermore induced a protective immune response in mice against severe lethal challenge infection. A protective level of RABV-specific virus-neutralizing antibody (VNA) was detected in intramuscular immunized mice and cattle without any clinical symptoms. This research demonstrated that the BHV-1 vector-based RABV vaccine is a potential candidate for cattle.

The Emerging Roles of Silver nanoparticles to Target Viral Life-Cycle and Detect Viral Pathogens

Along the line of recent vaccine advancements, new antiviral therapeutics are compelling to combat viral infection‐related public health crises. Several properties of silver nanoparticles (AgNPs) such as low level of cytotoxicity, ease of tunability of the AgNPs in the ultra‐small nanoscale size and shape through different convenient bottom‐up chemistry approaches, high penetration of the composite with drug formulations into host cells has made AgNPs, a promising candidate for developing antivirals. In this review, we have highlighted the recent advancements in the AgNPs based nano‐formulations to target cellular mechanisms of viral propagation, immune modulation of the host, and the ability to synergistically enhance the activity of existing antiviral drugs. On the other hand, we have discussed the recent advancements on AgNPs based detection of viral pathogens from clinical samples using inherent physicochemical properties. This article will provide an overview of our current knowledge on AgNPs based formulations that has promising potential for developing a counteractive strategy against emerging and existing viruses.

Change in the Single Amino Acid Site 83 in Rabies Virus Glycoprotein Enhances the BBB Permeability and Reduces Viral Pathogenicity

Lab-attenuated rabies virus (RABV) is a highly cellular adaptation and less pathogenic than wild-type RABV. However, the molecular mechanisms that regulate the cellular adaptation and pathogenicity remain obscure. In this work, we isolated a wild-type RABV (CNIM1701) from a rabid bovine in northern China. The original CNIM1701 was lethal in adult mice and restricted replication in cell cultures. After 20 serial passages in the brains of suckling mice, the virus was renamed CNIM1701-P20, which was safe in adult mice and replicated well in cell cultures. In addition, sequence comparison analysis of the original CNIM1701 and CNIM1701-P20 identified 2 amino acid substitutions on G protein (Lys83 → Arg83 and Pro367 → Ser 367) related to pathogenesis and cellular adaptation. Using site-directed mutagenesis to exchange Lys83 with Arg83 and Pro367 with Ser 367 in the G protein of the RABV SAD strain, the pathogenicity of rSAD-K83R was significantly decreased. Our data indicate that the decreased pathogenicity of rSAD-K83R is due to increasing the expression of RABV-G, which also induced a higher level of apoptosis in infected cells. Furthermore, the K83 mutation induced high expression of MMP-2 and MMP-9 on DCs and promoted blood-brain barrier (BBB) permeability. These results demonstrate that the pathogenesis of RABV is partially dependent on G expression and BBB permeability, which may help in the design and development of highly safe, live-RABV vaccines.

Attenuated Herpes Simplex Virus 1 (HSV-1) Expressing a Mutant Form of ICP6 Stimulates a Strong Immune Response That Protects Mice against HSV-1-Induced Corneal Disease

We previously isolated a herpes simplex virus 1 (HSV-1) mutant, KOS-NA, that carries two nonsynonymous mutations in UL39, resulting in L393P and R950H amino acid substitutions in infected cell protein 6 (ICP6). Our published data studying KOS-NA pathogenesis strongly suggest that one of these ICP6 substitutions expressed from KOS-NA, R950H, severely impaired acute viral replication in the eyes and trigeminal ganglia of mice after inoculation onto the cornea and consequently impaired establishment and reactivation from latency. Because of its significant neuroattenuation, we tested KOS-NA as a potential prophylactic vaccine against HSV-1 in a mouse model of corneal infection. KOS-NA stimulated stronger antibody and T cell responses than a replication-competent ICP0-null mutant and a replication-incompetent ICP8-null mutant optimized for immunogenicity. Immunizations with the ICP0^-, ICP8^-, and KOS-NA viruses all reduced replication of wild-type HSV-1 challenge virus in the corneal epithelium to similar extents. Low immunizing doses of KOS-NA and the ICP8^- virus, but not the ICP0^- virus, protected mice against eyelid disease (blepharitis). Notably, only KOS-NA protected almost completely against corneal disease (keratitis) and greatly reduced latent infection by challenge virus. Thus, vaccination of mice with KOS-NA prior to corneal challenge provides significant protection against HSV-1-mediated disease of the eye, even at a very low immunizing dose. These results suggest that KOS-NA may be the foundation of an effective prophylactic vaccine to prevent or limit HSV-1 ocular diseases.IMPORTANCE HSV-1 is a ubiquitous human pathogen that infects the majority of the world's population. Although most infections are asymptomatic, HSV-1 establishes lifelong latency in infected sensory neurons, from which it can reactivate to cause deadly encephalitis or potentially blinding eye disease. No clinically effective vaccine is available. In this study, we tested the protective potential of a neuroattenuated HSV-1 mutant (KOS-NA) as a vaccine in mice. We compared the effects of immunization with KOS-NA to those of two other attenuated viruses, a replication-competent (ICP0^-) virus and a replication-incompetent (ICP8^-) virus. Our data show that KOS-NA proved superior to the ICP0- and ICP8-null mutants in protecting mice from corneal disease and latent infection. With its significant neuroattenuation, severe impairment in establishing latency, and excellent protective effect, KOS-NA represents a significant discovery in the field of HSV-1 vaccine development.

Methamphetamine modulates the production of interleukin-6 and tumor necrosis factor-alpha via the cAMP/PKA/CREB signaling pathway in lipopolysaccharide-activated microglia

Methamphetamine (METH) elicits neuroinflammatory effects that may implicate its regulatory role on the microglial immune response. However, the mechanism underlying this remains unclear. In the present study, the effects of METH on lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) productions were tested in BV-2 cells and primary microglial cells. Additionally, western blot analysis was used to examine the phosphorylation of mitogenactivated protein kinases (MAPKs). Next, we detected the alterations in cAMP content and the phosphorylation levels of CREB in microglial cells to determine the involvement of the cAMP/CREB signaling pathway. We also used an adenylyl cyclase (AC) agonist (forskolin) and antagonist (MDL-12330A) and a PKA antagonist (H89) to confirm their participation. We observed that METH alone did not affect the production of IL-6 or TNF-α. In contrast, METH augmented the IL-6 production and inhibited the TNF-α production induced by LPS. A similar effect of forskolin was also observed in BV-2 cells. While MAPK activation was not influenced by METH alone, the LPS-induced phosphorylation of p38, JNK and ERK1/2 were all reduced by METH. Both the concentration of cAMP and the phosphorylation of CREB were increased by METH in LPS-activated microglial cells. The effects of METH were altered by MDL-12330A and H89. Moreover, the inhibition of the phosphorylation of ERK1/2 by METH was also reversed. These results suggest that the differential regulation of IL-6 and TNF-α by METH in LPS-activated microglial cells may be attributable to the cAMP/PKA/CREB signaling pathway.

Strategies to Improve Vaccine Efficacy against Tuberculosis by Targeting Innate Immunity

The global tuberculosis epidemic is the most common cause of death after infectious disease worldwide. Increasing numbers of infections with multi- and extensively drug-resistant variants of the Mycobacterium tuberculosis complex, resistant even to newly discovered and last resort antibiotics, highlight the urgent need for an efficient vaccine. The protective efficacy to pulmonary tuberculosis in adults of the only currently available vaccine, M. bovis BCG, is unsatisfactory and geographically diverse. More importantly, recent clinical studies on new vaccine candidates did not prove to be better than BCG, yet. Here, we propose and discuss novel strategies to improve efficacy of existing anti-tuberculosis vaccines. Modulation of innate immune responses upon vaccination already provided promising results in animal models of tuberculosis. For instance, neutrophils have been shown to influence vaccine efficacy, both, positively and negatively, and stimulate specific antibody secretion. Modulating immune regulatory properties after vaccination such as induction of different types of innate immune cell death, myeloid-derived suppressor or regulatory T cells, production of anti-inflammatory cytokines such as IL-10 may have beneficial effects on protection efficacy. Incorporation of lipid antigens presented via CD1 molecules to T cells have been discussed as a way to enhance vaccine efficacy. Finally, concepts of dendritic cell-based immunotherapies or training the innate immune memory may be exploitable for future vaccination strategies against tuberculosis. In this review, we put a spotlight on host immune networks as potential targets to boost protection by old and new tuberculosis vaccines.

Role of Autophagy and Apoptosis in the Postinfluenza Bacterial Pneumonia

The risk of influenza A virus (IAV) is more likely caused by secondary bacterial infections. During the past decades, a great amount of studies have been conducted on increased morbidity from secondary bacterial infections following influenza and provide an increasing number of explanations for the mechanisms underlying the infections. In this paper, we first review the recent research progress that IAV infection increased susceptibility to bacterial infection. We then propose an assumption that autophagy and apoptosis manipulation are beneficial to antagonize post-IAV bacterial infection and discuss the clinical significance.

An interaction quantitative trait loci tool implicates epistatic functional variants in an apoptosis pathway in smallpox vaccine eQTL data

Expression quantitative trait loci (eQTL) studies have functionalized nucleic acid variants through the regulation of gene expression. Although most eQTL studies only examine the effects of single variants on transcription, a more complex process of variant-variant interaction (epistasis) may regulate transcription. Herein, we describe a tool called interaction QTL (iQTL) designed to efficiently detect epistatic interactions that regulate gene expression. To maximize biological relevance and minimize the computational and hypothesis testing burden, iQTL restricts interactions such that one variant is within a user-defined proximity of the transcript (cis-regulatory). We apply iQTL to a data set of 183 smallpox vaccine study participants with genome-wide association study and gene expression data from unstimulated samples and samples stimulated by inactivated vaccinia virus. While computing only 0.15% of possible interactions, we identify 11 probe sets whose expression is regulated through a variant-variant interaction. We highlight the functional epistatic interactions among apoptosis-related genes, DIABLO, TRAPPC4 and FADD, in the context of smallpox vaccination. We also use an integrative network approach to characterize these iQTL interactions in a posterior network of known prior functional interactions. iQTL is an efficient, open-source tool to analyze variant interactions in eQTL studies, providing better understanding of the function of epistasis in immune response and other complex phenotypes.

Toll-like receptor agonist therapy can profoundly augment the antitumor activity of adoptively transferred CD8(+) T cells without host preconditioning

Background

Lymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial components, such as LPS, are key mediators of total body irradiation (TBI) enhancement, but our ability to strategically use these toll-like receptor (TLR) agonists to bolster the potency of T cell-based therapies for cancer remains elusive. Herein, we used TLR4 agonist LPS as a tool to address how and when to use TLR agonists to effectively improve cancer immunotherapy.

Methods

To determine the mechanisms of how innate immune activation via lymphodepletion potentiated antitumor T cell immunity, we utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were preconditioned with 5Gy TBI and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8⁺ T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated based on tumor growth and the phenotype of recovered splenocytes by flow cytometry. We also evaluated the role of non-toxic and clinically used TLR4 and TLR9 agonists—monophosphoryl lipid A (MPL) and CpG Oligodeoxynucleotide (CpG ODN), respectively— for ACT therapy.

Results

Here we report that while exogenous administration of LPS was able to enhance adoptively transferred CD8⁺ T cells’ tumor destruction, LPS treatment alone did not replace individual components of the tripartite ACT regimen, or obviate TBI. Moreover, we found that sequentially administering LPS during or one day prior to ACT therapy compromised tumor regression. In contrast, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred tumor-specific CD8⁺ T cells over host CD4⁺ T cells. We also found that non-toxic TLR agonists MPL and CpG potentiated the antitumor activity of infused CD8⁺ T cells. Finally, TBI was no longer needed to regress tumors in mice who were depleted of host CD4⁺ T cells, given a tripartite ACT regimen and then treated with low dose LPS.

Conclusions

Collectively, our results identify how and when to administer TLR agonists to augment T cell-based immunotherapy in the absence or presence of host preconditioning for treatment of advanced malignancies. Our findings have clinical implications for the design of next generation immune-based therapies for patients with cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0110-8) contains supplementary material, which is available to authorized users.

Cancer stem cell vaccine expressing ESAT-6-gpi and IL-21 inhibits melanoma growth and metastases

Tumor vaccines may induce antitumor efficacy, however, weak immunogenicity of tumor antigens is one of the prime obstacles for excitation of the antitumor immune responses. Therefore, strategies that enhance immunogenicity of tumor vaccines are of particular interest. In this study, a novel melanoma B16F10 CD133(+)CD44(+) cancer stem cell (CSC) vaccine expressing 6 kDa early secreted antigenic target (ESAT-6) in the glycosylphosphatidylinositol (GPI)-anchored form and secreting interleukin (IL)-21 was developed. Its anti-melanoma efficacy and mechanisms were investigated in mice. The results demonstrated that the B16F10-ESAT-6-gpi/IL-21 CD133(+)CD44(+) CSC vaccine exhibited enhanced anti-melanoma efficacy as determined by inhibited melanoma growth, prolonged survival of melanoma bearing mice. The anti-melanoma immunity was associated with elevated levels of serum anti-ESAT-6 and interferon (IFN)-γ as well as increased cytotoxic activities of natural killer cells, splenocytes, and complement dependent cytotoxicity. Furthermore, this CSC-based vaccine apparently inhibited melanoma lung metastasis by decreasing the level of Vimentin while increasing the level of E-cadherin expression, suggesting an inhibited epithelial mesenchymal transition. Thus, the B16F10-ESAT-6-gpi/IL-21 CD133(+)CD44(+) CSC vaccine may be used to reactivate the anti-tumor immunity and for treatment of melanoma.

Apoptosis in HEp-2 cells infected with Ureaplasma diversum

BACKGROUND

Bacterial pathogens have many strategies for infecting and persisting in host cells. Adhesion, invasion and intracellular life are important features in the biology of mollicutes. The intracellular location of Ureaplasma diversum may trigger disturbances in the host cell. This includes activation or inhibition of pro and anti-apoptotic factors, which facilitate the development of host damage. The aim of the present study was to associate U. diversum infection in HEp-2 cells and apoptosis induction. Cells were infected for 72hs with four U. diversum clinical isolates and an ATCC strain. The U. diversum invasion was analyzed by Confocal Laser Scanning Microscopy and gentamicin invasion assay. The apoptosis was evaluated using pro-apoptotic and anti-apoptotic gene expression, and FITC Annexin V/Dead Cell Apoptosis Kit.

RESULTS

The number of internalized ureaplasma in HEp-2 cells increased significantly throughout the infection. The flow cytometry analysis with fluorochromes to detect membrane depolarization and gene expression for caspase 2, 3 and 9 increased in infected cells after 24 hours. However, after 72 hours a considerable decrease of apoptotic cells was observed.

CONCLUSIONS

The data suggests that apoptosis may be initially induced by some isolates in association with HEp-2 cells, but over time, there was no evidence of apoptosis in the presence of ureaplasma and HEp-2 cells. The initial increase and then decrease in apoptosis could be related to bacterial pathogen-associated molecular pattern (PAMPS). Moreover, the isolates of U. diversum presented differences in the studied parameters for apoptosis. It was also observed that the amount of microorganisms was not proportional to the induction of apoptosis in HEp-2 cells.

Vaccine immunotherapy in breast cancer treatment: promising, but still early

Cancer vaccine-based immunotherapy should potentiate immunosurveillance function, preventing and protecting against growing tumors. Tumor cells usually activate the immune system, including T lymphocytes and natural killer cells, which are able to eliminate the transformed cells. Immunosubversion mechanisms related to tumor cells antigenic immunoediting induces mechanisms of tolerance and immunoescape. This condition impairs not only host-generated immunosurveillance, but also attempts to harness the immune response for therapeutic purposes. Most trials evaluating breast cancer vaccines have been carried out in patients in the metastatic and adjuvant setting. The aim of this review is to analyze the activity of vaccination strategies in current clinical trials. We summarize the differential approaches, protein-based and cell-based vaccines, focusing on vaccines targeting HER2/neu protein. Another focus of the review is to provide the reader with future challenges in the field, taking into account both the immunological and clinical aspects to better target the goal.

ESAT-6-gpi DNA vaccine augmented the specific antitumour efficacy induced by the tumour vaccine B16F10-ESAT-6-gpi/IL-21 in a mouse model

In this study, we hypothesized that the mice immunized with the glycosylphosphatidylinositol (GPI) anchored 6-kDa early-secreted antigenic target (ESAT-6) DNA vaccine (ESAT-6-gpi) and the tumour vaccine B16F10-ESAT-6-gpi/IL-21 might significantly enhance immune responses and antimelanoma efficacy. Our experimental results indicated that the anti-ESAT-6 antibody induced by the DNA vaccine ESAT-6-gpi bound ESAT-6 to the surface of tumour vaccine to activate a complement classical pathway and resulted in the B16F10 tumour cell lysis and apoptosis, which served as a potential trigger for breaking melanomatous immune tolerance to elicit an initiation of natural antimelanoma immunity. Our innovative approach of using the DNA vaccine ESAT-6-gpi priming and the tumour vaccine B16F10-ESAT-6-gpi/IL-21 boosting induced strong antimelanoma immunity that inhibited melanomatous growth. These findings highlighted the DNA vaccine ESAT-6-gpi as an immune enhancer to augment the immune efficacy of the tumour vaccine B16F10-ESAT -6-gpi/IL-21 against melanoma in a mouse model.

Apoptotic-like tumor cells and apoptotic neutrophils in mitochondrion-rich gastric adenocarcinomas: a comparative study with light and electron microscopy between these two forms of cell death

Mitochondrion-rich adenocarcinomas represent a rare variant of gastric adenocarcinomas composed predominantly of columnar adenocarcinoma cells with eosinophilic cytoplasm, a strong supranuclear immunoreactivity for antimitochondrial antibody, and a marked neutrophil infiltration associated to tumor cell death. The purpose of this work is to investigate, using correlated light and electron microscopy, mitochondrion-rich gastric adenocarcinomas focusing on the nature of the death in neoplastic cells and in infiltrating neutrophils. Adenocarcinoma cells, single or in small clusters, showed convoluted nuclei, irregularly condensed chromatin, loss of microvilli, and nuclear envelope dilatation. No nuclear fragmentation was observed in these dying cells and the plasma membrane did not show signs of disruption. These ultrastructural findings represent intermediate aspects between apoptosis and necrosis and are compatible with apoptosis-like programmed cell death. By contrast, some infiltrating neutrophils showed ultrastructural signs of classic apoptosis such as chromatin condensation into compact geometric (globular, crescentshaped) figures, tightly packed cytoplasmic granules and intact cell membrane. Our study provides ultrastructural evidence of apoptosislike tumour cell death in mitochondrion-rich gastric carcinomas and confirms that stereotyped outcome either as apoptosis or necrosis of tumor cells cannot always be expected in human neoplasms.

Dendritic cell immunotherapy in soft tissue sarcoma

Soft tissue sarcomas represent a rare but diverse family of tumors affecting patients of all ages. Conventional chemotherapy rarely eradicates metastatic disease and newer targeted agents are successful in only very specific histologic subgroups. Therefore, scientists and clinicians are investigating immunotherapy techniques, primarily involving cellular immunity focused on the T-cell response to tumor antigens. In both animal models and human sarcoma trials, dendritic cells have been shown to induce an effective antitumor immune response. Radiotherapy, particularly when delivered in a hypofractionated manner prior to sarcoma excision, may potentiate the function of the dendritic cells through the induction of apoptosis. The synergistic effect may carry over to other cancer types and warrants further multidisciplinary investigation.

Possible roles of proinflammatory and chemoattractive cytokines produced by human fetal membrane cells in the pathology of adverse pregnancy outcomes associated with influenza virus infection

Pregnant women are at an increased risk of influenza-associated adverse outcomes, such as premature delivery, based on data from the latest pandemic with a novel influenza A (H1N1) virus in 2009-2010. It has been suggested that the transplacental transmission of influenza viruses is rarely detected in humans. A series of our study has demonstrated that influenza virus infection induced apoptosis in primary cultured human fetal membrane chorion cells, from which a factor with monocyte differentiation-inducing (MDI) activity was secreted. Proinflammatory cytokines, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-β, were identified as a member of the MDI factor. Influenza virus infection induced the mRNA expression of not only the proinflammatory cytokines but also chemoattractive cytokines, such as monocyte chemoattractant protein (MCP)-1, regulated on activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1β, IL-8, growth-regulated oncogene (GRO)-α, GRO-β, epithelial cell-derived neutrophil-activating protein (ENA)-78, and interferon inducible protein (IP)-10 in cultured chorion cells. These cytokines are postulated to associate with human parturition. This paper, therefore, reviews (1) lessons from pandemic H1N1 2009 in pregnancy, (2) production of proinflammatory and chemoattractive cytokines by human fetal membranes and their functions in gestational tissues, and (3) possible roles of cytokines produced by human fetal membranes in the pathology of adverse pregnancy outcomes associated with influenza virus infection.

Cellular immunotherapy for soft tissue sarcomas

Soft tissue sarcomas are rare neoplasms, with approximately 9000 new cases in the USA every year. Unfortunately, during the past two decades, there has been little progress in the treatment of metastatic soft tissue sarcomas beyond the standard approaches of surgery, chemotherapy and radiation. Immunotherapy is a modality complementary to conventional therapy. It is appealing because functional antitumor activity could affect both local-regional and systemic disease, and act over a prolonged period of time. In this report, we review immunotherapeutic investigative strategies that are being developed, including several tumor vaccine, antigen vaccine and dendritic cell vaccine strategies.

Poly(I:C)-induced tumour cell death leads to DC maturation and Th1 activation

Dendritic cells (DCs) have the ability to generate peptide epitopes for MHC class I molecules derived from apoptotic tumour cells for direct recognition by cytotoxic T cells. This function has lead to DCs being used in vaccine strategies. In this study, we investigate the effect of inducing apoptosis in tumour cell lines using IFN-γ and poly(I:C), the subsequent maturation of the endocytosing DC and its ability to direct the resulting T cell response. We show that uptake of poly(I:C)-induced apoptotic tumour cells leads to DC maturation and activation with a Th1 cell polarising capacity. In contrast, these effects are not seen by DCs loaded with γ-irradiated apoptotic tumour cells. We propose that the manner in which tumour cells are induced to die can have a profound effect on the endocytosing DC and the resulting T cell response.

Vaxfectin: a versatile adjuvant for plasmid DNA- and protein-based vaccines

IMPORTANCE OF THE FIELD

Many vaccines require the use of an adjuvant to achieve immunity. So far, few adjuvants have advanced successfully through clinical trials to become part of licensed vaccines. Vaxfectin® (Vical, CA, USA) represents a next-generation adjuvant with promise as a platform technology, showing utility with both plasmid DNA (pDNA) and protein-based vaccines.

AREAS COVERED IN THIS REVIEW

This review describes the chemical, physical, preclinical and clinical development of Vaxfectin for pDNA-based vaccines. Also included is the preclinical development of Vaxfectin-adjuvanted protein- and peptide-based vaccines.

WHAT THE READER WILL GAIN

The reader will gain knowledge of vaccine adjuvant development from bench to bedside.

TAKE HOME MESSAGE

Vaxfectin has effectively boosted the immune response against a range of pDNA-expressed pathogenic antigens in preclinical models extending from rodents to non-human primates. In the clinic, Vaxfectin-adjuvanted pDNA-based H5N1 influenza vaccines have been shown to be well tolerated and to result in durable immune responses within the predicted protective range reported for protein-based vaccines.

Immunogenicity and safety of recombinant rabies viruses used for oral vaccination of stray dogs and wildlife

Rabies is a zoonotic disease and stray dogs, wild carnivores and bats are the natural reservoirs of rabies. Oral immunization with live vaccines is the only practical approach to eradicate rabies in free ranging terrestrial animals. We have developed the double glycoprotein (G) rabies virus (RV) variant SPBNGAS-GAS that has great promise to be used as a live-attenuated vaccine. Oral immunization of rodents and several target animal species with this double G RV variant resulted in the induction of protective immunity, superior to that induced by a single RV G variant (SPBNGAS). The high oral efficacy of SPBNGAS-GAS is likely because of its increased ability to infect monocytes or immature dendritic cells (DCs), thereby inducing their conversion into mature DCs. Furthermore, infection of DCs with the double G variant resulted in a strong up-regulation of the expression of genes related to the NFjB signalling pathway including IFN-α and IFN-β, which might underlie the protection conferred by this live RV vaccine. A potential problem associated with the use of live RVs for oral vaccination could rest in the possibility of reversion to the pathogenic phenotype because of the high mutation rate characteristic for all RNA viruses. In this respect, the presence of a second non-pathogenic G gene decreases considerably the risk of reversion to the pathogenic phenotype because a nonpathogenic G is dominant over a pathogenic G in determining the pathogenicity of the double G RV variant. Because of its excellent efficacy and safety, the SPBNGAS-GAS vaccine may provide a distinct advantage over other live RV vaccine in its ability to vaccinate a broad range of mammalian species.

Modulation of plasmid DNA vaccine antigen clearance by caspase 12 RNA interference potentiates vaccination

The magnitude of the immune responses elicited by plasmid DNA vaccines might be limited, in part, by the duration of vaccine antigen expression in vivo. To explore strategies for improving plasmid DNA vaccine efficacy, we studied the apoptotic process in myocytes of mice vaccinated intramuscularly. We found that after vaccination, the proapoptotic protein caspase 12 (Casp12) was upregulated in myocytes coincident with the loss of vaccine antigen expression. To harness this observation to improve plasmid DNA vaccine efficacy, we used RNA interference technology, coadministering plasmid DNA expressing a short hairpin RNA (shRNA) of Casp12 with plasmid DNA vaccine constructs. This treatment with shRNA Casp12, administered twice within the first 10 days following vaccine administration, increased antigen expression 7-fold, the antigen-specific CD8(+) T cell immune response 6-fold, and antigen-specific antibody production 5-fold. This study demonstrates the critical role for Casp12 in plasmid DNA vaccine-induced immune responses and shows that increased antigen expression mediated by down-modulation of Casp12 can be used to potentiate vaccine efficacy.

Harnessing the immune response to treat cancer

It is well established that the immune system has the capacity to attack malignant cells. During malignant transformation cells acquire numerous molecular and biochemical changes that render them potentially vulnerable to immune cells. Yet it is self-evident that a growing tumour has managed to evade these host defence mechanisms. The exact ways in which the immune system interacts with tumour cells and how cancers are able to escape immunological eradication have only recently started to be fully elucidated. Understanding the relationship between the tumour and the anti-tumour immune response and how this can be altered with conventional treatments and immune-targeted therapies is crucial to developing new treatments for patients with cancer. In this review, focusing on the anti-tumour T-cell response, we summarize our understanding of how tumours, cancer treatments and the immune system interact, how tumours evade the immune response and how this process could be manipulated for the benefit of patients with cancer.

Dendritic cells infected by recombinant rabies virus vaccine vector expressing HIV-1 Gag are immunogenic even in the presence of vector-specific immunity

Dendritic cells (DC) are the most potent antigen presenting cells whose ability to interact with T cells, B cells and NK cells has led to their extensive use in vaccine design. Here, we designed a DC-based HIV-1 vaccine using an attenuated rabies virus vector expressing HIV-1 Gag (RIDC-Gag). To test this, BALB/c mice were immunized with RIDC-Gag, and the primary, secondary as well as humoral immune responses were monitored. Our results indicate that RIDC-Gag stimulated HIV-1 Gag-specific immune responses in mice. When challenged with vaccinia virus (VV) expressing HIV-1 Gag, they elicited a potent Gag-specific recall response characterized by CD8+ T cells expressing multiple cytokines that were capable of specifically lysing Gag-pulsed target cells. Moreover, RIDC-Gag also enhanced CD8+ T cell responses via a homologous prime-boost regimen. These results show that a DC-based vaccine using live RV is immunogenic and a potential candidate for a therapeutic HIV-1 vaccine.

Molecular basis of neurovirulence of flury rabies virus vaccine strains: importance of the polymerase and the glycoprotein R333Q mutation

The molecular mechanisms associated with rabies virus (RV) virulence are not fully understood. In this study, the RV Flury low-egg-passage (LEP) and high-egg-passage (HEP) strains were used as models to explore the attenuation mechanism of RV. The results of our studies confirmed that the R333Q mutation in the glycoprotein (G(R333Q)) is crucial for the attenuation of Flury RV in mice. The R333Q mutation is stably maintained in the HEP genome background but not in the LEP genome background during replication in mouse brain tissue or cell culture. Further investigation using chimeric viruses revealed that the polymerase L gene determines the genetic stability of the G(R333Q) mutation during replication. Moreover, a recombinant RV containing the LEP G protein with the R333Q mutation and the HEP L gene showed significant attenuation, genetic stability, enhancement of apoptosis, and immunogenicity. These results indicate that attenuation of the RV Flury strain results from the coevolution of G and L elements and provide important information for the generation of safer and more effective modified live rabies vaccine.

Increased intensity lymphodepletion enhances tumor treatment efficacy of adoptively transferred tumor-specific T cells

Lymphodepletion before adoptive cell transfer (ACT)-based immunotherapies can enhance anti-tumor responses by augmenting innate immunity, by increasing access to homeostatic cytokines, and by depressing the numbers of regulatory T cells and myeloid-derived suppressor cells. Although it is clear that high-dose total body irradiation given together with hematopoietic stem cell (HSC) transplantation effectively enhances ACT, the relationship between the intensity of lymphodepletion and tumor treatment efficacy has not been systematically studied. Using the pmel-1 mouse model of self/tumor-reactive CD8 T cells, we observed a strong correlation between the intensity of the conditioning regimen and the efficacy of ACT-based treatments using linear regression analysis. This was the case for preparative total body irradiation administered either as a single dose (R=0.97, P<0.001) or in fractionated doses (R=0.94, P<0.001). Increased amounts of preparative total body irradiation were directly correlated with progressively more favorable ratios of transferred tumor-reactive CD8 T cells toward endogenous cells with the potential for inhibitory activity including: CD4 cells (potentially T regulatory cells); Gr1 cells (which are capable of functioning as myeloid-derived suppressor cells); and endogenous CD8 and natural killer 1.1 cells (that can act as "sinks" for homeostatic cytokines in the postablative setting). With increasing ablation, we also observed elevated lipopolysaccharide levels in the sera and heightened levels of systemic inflammatory cytokines. Thus, increased intensity lymphodepletion triggers enhanced tumor treatment efficacy and the benefits of high-dose total body irradiation must be titrated against its risks.

Combining conventional therapies with intratumoral injection of autologous dendritic cells and activated T cells to treat patients with advanced cancers

Dendritic cells (DCs) are potent antigen-presenting cells that have been used in cancer immunotherapy. To take advantage of the ability of DCs to acquire antigenic materials from their environment and generate primary as well as recall immune responses, 37 patients with advanced cancers were enrolled in a series of protocols based on direct intratumoral injection of immature DCs. To augment antigen uptake and antitumor immune response, DC injection was combined with radiotherapy or chemotherapy and/or injection of activated T cells. Treatments were well tolerated with no adverse reactions. Clinical responses were based on Response Evaluation Criteria in Solid Tumors, with the majority of patients showing stable disease. One of two patients who also received local radiation achieved a sustained complete response at injected and metastatic sites. The clinical responses observed in cancer patients with advanced disease suggest potential effectiveness of combination strategies and establish the basis for the current treatment protocol that is underway.

Tumor apoptotic bodies inhibit CTL responses and antitumor immunity via membrane-bound transforming growth factor-beta1 inducing CD8+ T-cell anergy and CD4+ Tr1 cell responses

Tumor cell apoptosis induced by radiation therapy results in apoptotic tumor cells and apparition of membrane blebs termed apoptotic bodies (APB). The immune responses induced by apoptotic tumor cells have been extensively studied. However, the role of APB in modulation of tumor immune responses is elusive. In this study, we induced apoptosis in 90% ovabumin-expressing EG7 tumor cells by in vitro irradiation (9,000 rad) of tumor cells with a subsequent cell culture for 9 hours. APB purified from irradiation-induced apoptotic EG7 cell culture supernatant by differential ultracentrifugation were vesicles with 50 to 90 nm in diameter and expressed apoptosis-specific Annexin V, 14-3-3, and Histone H3. We then investigated its potential modulation in DC(OVA)-induced T-cell responses and antitumor immunity. We found that EG7-derived APB were tolerogenic and capable of suppressing DC(OVA)-stimulated CD8+ CTL responses and antitumor immunity via its induction of CD8+ T-cell anergy and type 1 regulatory CD4+ T-cell responses. Analysis of apoptotic tumor cells and APB revealed the expression of membrane-bound transforming growth factor (TGF)-beta1 associated with irradiation-induced apoptosis formation, which is a result from activation of transcriptional factor NF-AT specific for TGF-beta1 promoters. Our data further elucidate that it is the membrane-bound TGF-beta1 expression on APB that contributes to its in vitro antiproliferative effect as shown by using neutralizing TGF-beta1-specific antibody. Administration of anti-TGF-beta1 antibody in vivo also blocked APB-mediated immune suppression of CD8+ CTL responses and antitumor immunity. Therefore, our study may have great impact in designing a combined radiation therapy with immunotherapy of cancer.

Enterocyte shedding and epithelial lining repair following ischemia of the human small intestine attenuate inflammation

Background

Recently, we observed that small-intestinal ischemia and reperfusion was found to entail a rapid loss of apoptotic and necrotic cells. This study was conducted to investigate whether the observed shedding of ischemically damaged epithelial cells affects IR induced inflammation in the human small gut.

Methods and Findings

Using a newly developed IR model of the human small intestine, the inflammatory response was studied on cellular, protein and mRNA level. Thirty patients were consecutively included. Part of the jejunum was subjected to 30 minutes of ischemia and variable reperfusion periods (mean reperfusion time 120 (±11) minutes). Ethical approval and informed consent were obtained. Increased plasma intestinal fatty acid binding protein (I-FABP) levels indicated loss in epithelial cell integrity in response to ischemia and reperfusion (p<0.001 vs healthy). HIF-1α gene expression doubled (p = 0.02) and C3 gene expression increased 4-fold (p = 0.01) over the course of IR. Gut barrier failure, assessed as LPS concentration in small bowel venous effluent blood, was not observed (p = 0.18). Additionally, mRNA expression of HO-1, IL-6, IL-8 did not alter. No increased expression of endothelial adhesion molecules, TNFα release, increased numbers of inflammatory cells (p = 0.71) or complement activation, assessed as activated C3 (p = 0.14), were detected in the reperfused tissue.

Conclusions

In the human small intestine, thirty minutes of ischemia followed by up to 4 hours of reperfusion, does not seem to lead to an explicit inflammatory response. This may be explained by a unique mechanism of shedding of damaged enterocytes, reported for the first time by our group.

Graft rejection occurring in post-liver transplant patients receiving cytotoxic chemotherapy: a case series

Liver transplant recipients are known to be at increased risk for the development of de novo neoplasms or the recurrence of preexisting malignancies, and this is possibly related to the use of immunosuppressive medication. Little is known about the effects of cytotoxic chemotherapy on graft function after transplantation. A retrospective chart and pathology database review was undertaken to identify post-liver transplant patients developing rejection during chemotherapy. All liver biopsies were reviewed by a hepatopathologist. Three patients were identified. All patients were diagnosed with cancer within 7 years of liver transplantation; two-thirds died soon after the diagnosis of malignancy. Rejection occurred soon after chemotherapy was started. All patients were receiving prednisone and tacrolimus (trough levels: 2.1-4.8 ng/mL). One patient developed plasma cell hepatitis (de novo autoimmune hepatitis). There was no histologic evidence of hepatotoxicity due to the chemotherapeutic agents. Cytotoxic chemotherapy should be used in liver transplant recipients with caution, and immunosuppressant doses should be maintained at therapeutic levels, as patients may be at risk for allograft rejection. Treatment of rejection or plasma cell hepatitis in this setting should be undertaken in a timely and aggressive fashion to prevent chronic ductopenic rejection.

Ag-specific type 1 CD8 effector cells enhance methotrexate-mediated antitumor responses by modulating endogenous CD49b-expressing CD4 and CD8 T effector cell subpopulations producing IL-10

The chemotherapeutic agent methotrexate is widely used in the treatment of breast cancer. Although its mechanism-of-action has been defined, less is known about its interaction with Ag-specific T cell-mediated antitumor responses. Type 1 CD8 T cell-mediated immune responses (Tc1) are cytolytic, produce IFN-gamma and are associated with effective antitumor responses. Using a murine transgenic TCR tumor model, we show that single-dose-treatment with methotrexate enhanced CD8-mediated type 1 antitumor responses when administered three days prior to Tc1 effector cell transfer. Co-treatment with methotrexate not only enhanced donor Tc1 cell accumulation and persistence at sites of primary tumor growth, but also promoted elevated levels of activated CD25(+) expressing donor TIL cells. This correlated with a marked decrease in the appearance of endogenous differentiated (CD44(High)) CD3/CD8/CD49b and CD3/CD4/CD49b tumor-infiltrating effector T cells at both early (Days 1-8) and late (Days 12-20) stages following treatment when compared to that of corresponding groups receiving either MTX or Tc1 cell transfer alone. Moreover, such cellular response kinetics appeared to further correlate with the down-regulation of endogenous CD4/CD44(High)/CD49b effector T cells producing IL-10 and delays in tumor growth in vivo. This suggested that Ag-specific Tc1 cell transfer, in combination with chemotherapy, can enhance antitumor responses by modulating select CD49b-expressing T effector/memory cell subpopulations involved in homeostasis and immune tolerance within the tumor environment. These studies offer insight into mechanisms that enhance T cell-based immunotherapy in cancer. Supplementary materials are available for this article. Go to the publisher's online edition of Immunological Investigations for the following free supplemental resource(s): Addendum 1.

Histone deacetylase regulation of immune gene expression in tumor cells

Epigenetic modifications of chromatin, such as histone acetylation, are involved in repression of tumor antigens and multiple immune genes that are thought to facilitate tumor escape. The status of acetylation in a cell is determined by the balance of the activities of histone acetyltransferases and histone deacetylases. Inhibitors of histone deacetylase (HDACi) can enhance the expression of immunologically important molecules in tumor cells and HDACi treated tumor cells are able to induce immune responses in vitro and in vivo. Systemic HDACi are in clinical trails in cancer and also being used in several autoimmune disease models. To date, 18 HDACs have been reported in human cells and more than thirty HDACi identified, although only a few immune targets of these inhibitors have been identified. Here, we discuss the molecular pathways employed by HDACi and their potential role in inducing immune responses against tumors. We review data suggesting that selection of target specific HDACi and combinations with other agents and modalities, including those that activate stress pathways, may further enhance the efficacy of epigenetic therapies.

Ag-specific type 1 CD8 effector cells enhance methotrexate-mediated antitumor responses by modulating differentiated T cell localization, activation and chemokine production in established breast cancer

The chemotherapeutic agent methotrexate is widely used in the treatment of breast cancer. Although its mechanism-of-action has been defined, less is known about its interaction with T cell-mediated antitumor responses. Type 1 CD8 T cell-mediated immune responses (Tc1) are cytolytic, produce IFN-gamma and are associated with effective antitumor responses. Using a murine transgenic TCR tumor model, we show that single-dose treatment with methotrexate enhanced CD8-mediated type 1 antitumor responses when administered 3 days prior to Tc1 effector cell transfer. Co-treatment with methotrexate not only enhanced donor Tc1 cell accumulation and persistence at sites of primary tumor growth, but also promoted elevated levels of activated donor TIL cells. This markedly enhanced the appearance of endogenous differentiated (CD44(High)) CD8 tumor-infiltrating cells when compared to that of corresponding groups receiving either MTX or Tc1 cell transfer alone. Such cells were acutely activated as defined by co-expression of surface markers associated with TCR engagement (CD69) and T cell activation (CD25) at both early (days 1-8) and late (days 12-20) stages following treatment. Conversely, such animals showed an early decrease in CD4(+)/CD44(High)/CD25(+)/CD69(+) T cells that correlated with delays in tumor growth in vivo. Moreover, cellular response kinetics appeared to further correlate with the up-regulation of endogenous T cells producing the chemokine IP-10 in vivo. This suggested that Tc1 cell transfer, in combination with chemotherapy, can enhance antitumor responses by modulating immunoregulatory T cells involved in homeostasis and immune tolerance within the tumor environment. These studies offer insight into mechanisms that enhance T cell-based immunotherapy in cancer.

Toll-like receptors in tumor immunotherapy

Lymphodepletion with chemotherapeutic agents or total body irradiation (TBI) before adoptive transfer of tumor-specific T cells is a critical advancement in the treatment of patients with melanoma. More than 50% of patients that are refractory to other treatments experience an objective or curative response with this approach. Emerging data indicate that the key mechanisms underlying how TBI augments the functions of adoptively transferred T cells include (a) the depletion of regulatory T cells (T(reg)) and myeloid-derived suppressor cells that limit the function and proliferation of adoptively transferred cells; (b) the removal of immune cells that act as "sinks" for homeostatic cytokines, whose levels increase after lymphodepletion; and (c) the activation of the innate immune system via Toll-like receptor 4 signaling, which is engaged by microbial lipopolysaccharide that translocated across the radiation-injured gut. Here, we review these mechanisms and focus on the effect of Toll-like receptor agonists in adoptive immunotherapy. We also discuss alternate regimens to chemotherapy or TBI, which might be used to safely treat patients with advanced disease and promote tumor regression.

An epigenetic vaccine model active in the prevention and treatment of melanoma

Background

Numerous immune genes are epigenetically silenced in tumor cells and agents such as histone deacetylase inhibitors (HDACi), which reverse these effects, could potentially be used to develop therapeutic vaccines. The conversion of cancer cells to antigen presenting cells (APCs) by HDACi treatment could potentially provide an additional pathway, together with cross-presentation of tumor antigens by host APCs, to establish tumor immunity.

Methods

HDACi-treated B16 melanoma cells were used in a murine vaccine model, lymphocyte subset depletion, ELISpot and Cytotoxicity assays were employed to evaluate immunity. Antigen presentation assays, vaccination with isolated apoptotic preparations and tumorigenesis in MHC-deficient mice and radiation chimeras were performed to elucidate the mechanisms of vaccine-induced immunity.

Results

HDACi treatment enhanced the expression of MHC class II, CD40 and B7-1/2 on B16 cells and vaccination with HDACi-treated melanoma cells elicited tumor specific immunity in both prevention and treatment models. Cytotoxic and IFN-γ-producing cells were identified in splenocytes and CD4⁺, CD8⁺ T cells and NK cells were all involved in the induction of immunity. Apoptotic cells derived from HDACi treatments, but not H₂O₂, significantly enhanced the effectiveness of the vaccine. HDACi-treated B16 cells become APCs in vitro and studies in chimeras defective in cross presentation demonstrate direct presentation in vivo and short-term but not memory responses and long-term immunity.

Conclusion

The efficacy of this vaccine derives mainly from cross-presentation which is enhanced by HDACi-induced apoptosis. Additionally, epigenetic activation of immune genes may contribute to direct antigen presentation by tumor cells. Epigenetically altered cancer cells should be further explored as a vaccine strategy.

The immune system--is it relevant to cancer development, progression and treatment?

The ability of the immune system to effectively respond to human tumours is a matter of long-term controversy. There is an increasing body of recent evidence to support a role for the immune system in eliminating pre-clinical cancers, an old concept termed 'immunosurveillance'. 'Immunoediting' is an updated hypothesis, in which selection pressures applied by the immune response to tumours modulate tumour immunogenicity and growth. Tumour infiltration by immune cells has been shown to have powerful prognostic significance in a host of cancer types. Paradoxically, in some circumstances the immune system can promote tumour development. Cytotoxic therapies, including radiotherapy and chemotherapy, induce potentially immunogenic cell death, releasing tumour-associated antigens in the context of a 'danger' signal to the immune system. An understanding of the interaction between immune cells, tumour cells and treatment modalities will therefore guide the future combination of immunotherapy with conventional therapy to achieve optimal anti-tumour effects.

Current status of monocyte differentiation-inducing (MDI) factors derived from human fetal membrane chorion cells undergoing apoptosis after influenza virus infection

Influenza virus infection induces apoptosis and the expression of a set of pro-inflammatory cytokine genes, such as interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, interferon (IFN)-beta and IFN-gamma, in cultured human fetal membrane chorion cells. Monocyte differentiation-inducing (MDI) activity in culture supernatants is simultaneously increased by the virus infection. The MDI activity is predominantly influenced by IL-6 molecule in culture supernatants, and partly by TNF-alpha and IFN-beta, but not IFN-gamma, molecules. The MDI factors are able to induce the mRNA expression of macrophage class A scavenger receptor (SR-A), which is one of adhesion and apoptotic cell-recognizing molecules, and gp91(phox), which is a catalytic subunit of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzyme complex, on monocytic cells. As a result, monocytes are initiated to differentiate into well-matured macrophages capable of adhering and producing superoxide through NADPH oxidase. The matured macrophages, obtained from human monocytic leukemia THP-1 cells by the treatment with MDI factors, phagocytose apoptotic chorion cell debris resulting from the virus infection. Subsequent to phagocytosis, an abrupt increase of superoxide production by macrophages may occur. In this article, we summarize recent knowledge about the MDI factors derived from human fetal membrane chorion cells undergoing apoptosis after influenza virus infection, and discuss their possible pathological roles during pregnancy.

T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies

Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect. In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly, 7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic sites. More strikingly, depletion of CD8(+) and CD4(+) T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant. This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction of an adjuvant effect.

GM-CSF-secreting cancer immunotherapies: preclinical analysis of the mechanism of action

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting tumor cell immunotherapies have demonstrated long-lasting, and specific anti-tumor immune responses in animal models. The studies reported here specifically evaluate two aspects of the immune response generated by such immunotherapies: the persistence of irradiated tumor cells at the immunization site, and the breadth of the immune response elicited to tumor associated antigens (TAA) derived from the immunotherapy. To further define the mechanism of GM-CSF-secreting cancer immunotherapies, immunohistochemistry studies were performed using the B16F10 melanoma tumor model. In contrast to previous reports, our data revealed that the irradiated tumor cells persisted and secreted high levels of GM-CSF at the injection site for more than 21 days. Furthermore, dense infiltrates of dendritic cells were observed only in mice treated with GM-CSF-secreting B16F10 cells, and not in mice treated with unmodified B16F10 cells with or without concurrent injection of rGM-CSF. In addition, histological studies also revealed enhanced neutrophil and CD4+ T cell infiltration, as well as the presence of apoptotic cells, at the injection site of mice treated with GM-CSF-secreting tumor cells. To evaluate the scope of the immune response generated by GM-CSF-secreting cancer immunotherapies, several related B16 melanoma tumor cell subclones that exist as a result of genetic drift in the original cell line were used to challenge mice previously immunized with GM-CSF-secreting B16F10 cells. These studies revealed that GM-CSF-secreting cancer immunotherapies elicit T cell responses that effectively control growth of related but antigenically distinct tumors. Taken together, these studies provide important new insights into the mechanism of action of this promising novel cancer immunotherapy.

Triggering of dendritic cell responses after exposure to activated, but not resting, apoptotic PBMCs

Dendritic cells (DCs) can be activated by signaling via pathogen receptors, by interaction with activated T cells or by exposure to inflammatory mediators. Clearance of apoptotic cells by DCs is generally considered a silent event that is not associated with an inflammatory response. Necrotic cell death, in contrast, leads to induction of inflammation. However, emerging data challenge the view of apoptotic cells as inherently nonimmunogenic. In this study, we report that the activation state of the apoptotic cell may determine whether the exposed DC becomes activated and rendered proficient in Ag presentation. We show that coculture with activated, but not resting, apoptotic PBMCs leads to up-regulation of surface expression of the costimulatory molecules CD80, CD83, and CD86 in human DCs as well as release of proinflammatory cytokines. Furthermore, we show that DCs exposed to allogeneic, activated apoptotic PBMCs induce proliferation and IFN-gamma production in autologous T cells. Together, these findings show that activated apoptotic PBMCs per se provide an activation/maturation signal to DCs, suggesting that activated apoptotic PBMCs possess endogenous adjuvant properties.

PERK eIF2 alpha kinase is required to regulate the viability of the exocrine pancreas in mice

Background

Deficiency of the PERK eIF2α kinase in humans and mice results in postnatal exocrine pancreatic atrophy as well as severe growth and metabolic anomalies in other organs and tissues. To determine if the exocrine pancreatic atrophy is due to a cell-autonomous defect, the Perk gene was specifically ablated in acinar cells of the exocrine pancreas in mice.

Results

We show that expression of PERK in the acinar cells is required to maintain their viability but is not required for normal protein synthesis and secretion. Exocrine pancreatic atrophy in PERK-deficient mice was previously attributed to uncontrolled ER-stress followed by apoptotic cell death based on studies in cultured fibroblasts. However, we have found no evidence for perturbations in the endoplasmic reticulum or ER-stress and show that acinar cells succumb to a non-apoptotic form of cell death, oncosis, which is associated with a pronounced inflammatory response and induction of the pancreatitis stress response genes. We also show that mice carrying a knockout mutation of PERK's downstream target, ATF4, exhibit pancreatic deficiency caused by developmental defects and that mice ablated for ATF4's transcriptional target CHOP have a normal exocrine pancreas.

Conclusion

We conclude that PERK modulates secretory capacity of the exocrine pancreas by regulating cell viability of acinar cells.

Necrotic tumor cell death in vivo impairs tumor-specific immune responses

The manner in which cells die is believed to have a major impact on the nature of immune responses to their released Ags. In this study, we present the first direct analysis of tumor-specific immune responses to in vivo occurring tumor cell death through apoptosis or necrosis. Mice bearing thymidine kinase-transfected tumors were treated either with ganciclovir to induce tumor cell apoptosis in vivo or a vascular targeting agent, ZD6126, to induce tumor cell necrosis in vivo. In contrast to tumor apoptosis, induction of necrosis reduced the frequency and impaired the function of tumor-specific CD8(+) T cells. Adoptive transfer of lymphocytes from mice with apoptotic tumors into tumor-challenged mice resulted in a significant tumor protection, which was absent when splenocytes were transferred from mice with necrotic tumors. Anti-CD40 treatment reversed impaired Ag-specific CD8(+) T cell responses in these mice. These observations have not only fundamental importance for the development of immunotherapy protocols but also help to understand the underlying mechanism of in vivo immune responses to tumor cell death.

Epigenetic regulation of immune escape genes in cancer

According to the concept of immune surveillance, the appearance of a tumor indicates that it has earlier evaded host defenses and subsequently must have escaped immunity to evolve into a full-blown cancer. Tumor escape mechanisms have focused mainly on mutations of immune and apoptotic pathway genes. However, data obtained over the past few years suggest that epigenetic silencing in cancer may be as frequent a cause of gene inactivation as are mutations. Here, we discuss the evidence that tumor immune evasion is mediated by non-mutational epigenetic events involving chromatin and that epigenetics collaborates with mutations in determining tumor progression. Since epigenetic changes are potentially reversible, the relative contribution of mutations and epigenetics, to the gene defects in any given tumor, may be a factor in determining the efficacy of treatments. We review new developments in basic chromatin mechanisms and in this context describe the rationale for the current use of epigenetic agents in cancer therapy and for a novel epigenetically generated tumor vaccine model. We emphasize that epigenetic cancer treatments are currently a 'blunt-sword' and suggest future directions for designing chromatin-based programs of potential value in the diagnosis and treatment of cancer.

Progress in tuberculosis vaccine development

The first tuberculosis vaccine candidates have reached clinical testing. Novel subunit vaccine candidates aimed at boosting previous BCG-prime vaccination and novel viable attenuated vaccine candidates aimed at substituting BCG have both completed the preclinical stage. Despite these achievements, rational vaccine design against tuberculosis has not come to an end. Novel findings in basic immunology and microbiology will advance further improvements in vaccine development. These include the potential role of crosspriming to induce more potent T-cell responses, the role of memory T cells and regulatory T cells in sustaining or curtailing optimal immune responses, respectively, as well as the involvement of cytokines in T-cell migration to nonimmunologic tissue sites and in the generation of memory. Knowledge about basic mechanisms underlying optimum protection will not only have a direct impact on future vaccine design against tuberculosis but also help in the formulation of a set of biomarkers with predictive value for vaccine efficacy assessment.

Humoral and cellular immune response to RNA immunization with flavivirus replicons derived from tick-borne encephalitis virus

A new vaccination principle against flaviviruses, based on a tick-borne encephalitis virus (TBEV) self-replicating noninfectious RNA vaccine that produces subviral particles, has recently been introduced (R. M. Kofler, J. H. Aberle, S. W. Aberle, S. L. Allison, F. X. Heinz, and C. W. Mandl, Proc. Natl. Acad. Sci. USA 7:1951-1956, 2004). In this study, we evaluated the potential of the self-replicating RNA vaccine in mice in comparison to those of live, attenuated vaccines and a formalin-inactivated whole-virus vaccine (ImmunInject). For this purpose, mice were immunized using gene gun-mediated application of the RNA vaccine and tested for CD8+ T-cell responses, long-term duration, neutralizing capacity, and isotype profile of specific antibodies and protection against lethal virus challenge. We demonstrate that the self-replicating RNA vaccine induced a broad-based, humoral and cellular (Th1 and CD8+ T-cell response) immune response comparable to that induced by live vaccines and that it protected mice from challenge. Even a single immunization with 1 microg of the replicon induced a long-lasting antibody response, characterized by high neutralizing antibody titers, which were sustained for at least 1 year. Nevertheless, it was possible to boost this response further by a second injection with the RNA vaccine, even in the presence of a concomitant CD8+ T-cell response. In this way it was possible to induce a balanced humoral and cellular immune response, similar to infection-induced immunity but without the safety hazards of infectious agents. The results also demonstrate the value of TBEV replicon RNA for inducing protective long-lasting antiviral responses.