Receptor-mediated uptake of antigen/heat shock protein complexes results in major histocompatibility complex class I antigen presentation via two distinct processing pathways

Heat shock protein 70 protects the lungs from hyperoxic injury in a neonatal rat model of bronchopulmonary dysplasia

Hyperoxia plays a significant role in the pathogenesis of lung injury, such as bronchopulmonary dysplasia (BPD), in premature infants or newborns. BPD management aims to minimize further injury, provide an optimal environment to support growth and recovery. In clinic neonatal care, we need a new therapy for BPD. Heat shock protein 70 (Hsp70) inhibit cell apoptosis and promote cell repair allowing cells to survive lethal injury. We hypothesized that Hsp70 could be used to prevent hyperoxia related BPD in the neonatal rat model through its anti-apoptotic and anti-inflammatory effects. In this study, we explored the effect of Hsp70 on hyperoxia-induced lung injury using neonatal rats. Neonatal Wistar rats were delivered naturally at full term of gestation and were then pooled and randomly assigned to several groups to receive heat stimulation (41°C for 20 min) or room temperature conditions. The Hsp70 group received recombinant Hsp70 intraperitoneally (200 μg/kg, daily). All newborn rats were placed under hyperoxic conditions (85% oxygen) for 21 days. Survival rates in both heat-hyperoxia and Hsp70-hyperoxia groups were higher than those in the hyperoxia group (p < 0.05). Both endogenous and exogenous Hsp70 could reduce early apoptosis of alveolar cells under hyperoxia. Additionally, there were less macrophage infiltration in the lung of the Hsp70 groups (p < 0.05). Heat stress, heat shock proteins, and exogenous recombinant Hsp70 significantly increased the survival rate and reduced pathological hyperoxia induced lung injuries in the development of BPD. These results suggest that treating hyperoxia-induced lung injury with Hsp70 may reduce the risk of developing BPD.

Impact of preweaning vaccination on host gene expression and antibody titers in healthy beef calves

The impact of preweaning vaccination for bovine respiratory viruses on cattle health and subsequent bovine respiratory disease morbidity has been widely studied yet questions remain regarding the impact of these vaccines on host response and gene expression. Six randomly selected calves were vaccinated twice preweaning (T1 and T3) with a modified live vaccine for respiratory pathogens and 6 randomly selected calves were left unvaccinated. Whole blood samples were taken at first vaccination (T1), seven days later (T2), at revaccination and castration (T3), and at weaning (T4), and utilized for RNA isolation and sequencing. Serum from T3 and T4 was analyzed for antibodies to BRSV, BVDV1a, and BHV1. Sequenced RNA for all 48 samples was bioinformatically processed with a HISAT2/StringTie pipeline, utilizing reference guided assembly with the ARS-UCD1.2 bovine genome. Differentially expressed genes were identified through analyzing the impact of time across all calves, influence of vaccination across treatment groups at each timepoint, and the interaction of time and vaccination. Calves, regardless of vaccine administration, demonstrated an increase in gene expression over time related to specialized proresolving mediator production, lipid metabolism, and stimulation of immunoregulatory T-cells. Vaccination was associated with gene expression related to natural killer cell activity and helper T-cell differentiation, enriching for an upregulation in Th17-related gene expression, and downregulated genes involved in complement system activity and coagulation mechanisms. Type-1 interferon production was unaffected by the influence of vaccination nor time. To our knowledge, this is the first study to evaluate mechanisms of vaccination and development in healthy calves through RNA sequencing analysis.

Recombinant human Hsp110-gp100 chaperone complex vaccine is nontoxic and induces response in advanced stage melanoma patients

Heat shock proteins (hsp) are intracellular chaperones that possess extracellular immunostimulatory properties when complexed with antigens. A recombinant Hsp110-gp100 chaperone complex vaccine showed an antitumor response and prolonged survival in murine melanoma. A phase Ib dose-escalation study of a recombinant human Hsp110-gp100 vaccine in advanced-stage melanoma patients was performed to evaluate toxicity, immunostimulatory potential and clinical response. Patients with pretreated, unresectable stage IIIB/C/IV melanoma received the chaperone complex vaccine in a dose-escalation protocol; three vaccinations over a 43-day-period. Tumor response, clinical toxicity and immune response were measured. Ten patients (eight female, median age 70 years) were enrolled and two patients had grade 1 adverse events; minor skin rash, hyperhidrosis and fever (no grade 2 or higher adverse events). Median progression-free survival was longer for lower vaccine doses as compared to the maximum dose of 180 mcg (4.5 vs. 2.9 months; P = 0.018). The lowest dose patients (30 and 60 mcg) had clinical tumor responses (one partial response, one stable disease). CD8+ T cell interferon-γ responses to gp100 were greater in the clinically responding patients. A pattern of B cell responses to vaccination was not observed. Regulatory T cell populations and co-stimulatory molecules including cytotoxic T-lymphocyte-associated protein 4 and PD-1 appeared to differ in responders versus nonresponders. A fully recombinant human Hsp110-gp100 chaperone complex vaccine had minimal toxicity, measurable tumor responses at lower doses and produced peripheral CD8+ T cell activation in patients with advanced, pretreated melanoma. Combination with currently available immunotherapies may augment clinical responses.

Role of Laser Interstitial Thermal Therapy in the Management of Primary and Metastatic Brain Tumors

OPINION STATEMENT

Laser interstitial thermal therapy (LITT) is a minimally invasive treatment option for brain tumors including glioblastoma, other primary central nervous system (CNS) neoplasms, metastases, and radiation necrosis. LITT employs a fiber optic coupled laser delivery probe stabilized via stereotaxis to deliver thermal energy that induces coagulative necrosis in tumors to achieve effective cytoreduction. LITT complements surgical resection, radiation treatment, tumor treating fields, and systemic therapy, especially in patients who are high risk for surgical resection due to tumor location in eloquent regions or poor functional status. These factors must be balanced with the increased rate of cerebral edema post LITT compared to surgical resection. LITT has also been shown to induce transient disruption of the blood-brain barrier (BBB), especially in the peritumoral region, which allows for enhanced CNS delivery of anti-neoplastic agents, thus greatly expanding the armamentarium against brain tumors to include highly effective anti-neoplastic agents that have poor BBB penetration. In addition, hyperthermia-induced immunogenic cell death is another secondary side effect of LITT that opens up immunotherapy as an attractive adjuvant treatment for brain tumors. Numerous large studies have demonstrated the safety and efficacy of LITT against various CNS tumors and as the literature continues to grow on this novel technique so will its indications.

Betulinic Acid Modulates the Expression of HSPA and Activates Apoptosis in Two Cell Lines of Human Colorectal Cancer

Betulinic acid (BA) is a pentacyclic triterpene usually isolated from botanical sources. Numerous studies have reported the inhibitory effect of BA against human colorectal cancer cells (CRC). However, its effect on the expression of the molecular chaperone HSPA is unclear. The aim of this research is to investigate the anti-cancer activities of BA purified from Piper retrofractum and study its effect on the expression of HSPA in colorectal cancer HCT116 and SW480 cells. The viability of both cancer cells was reduced after they were treated with an increasing dosage of BA. Flow cytometry assay revealed that levels of cell apoptosis significantly increased after incubation with BA in both cancer cells. Pro-apoptotic markers including Bax, cleaved-caspase-3 and cleaved-caspase-9 were increased while anti-apoptotic marker Bcl-2 was decreased after BA treatment. Western blot also showed that the expression of HSPA fluctuated upon BA treatment, whereby HSPA was increased at lower BA concentrations while at higher BA concentrations HSPA expression was decreased. Preliminary molecular docking assay showed that BA can bind to the nucleotide binding domain of the HSP70 at its ADP-bound state of the HSP70. Although further research is needed to comprehend the BA-HSPA interaction, our findings indicate that BA can be considered as potential candidate for the development of new treatment for colorectal cancer.

The Role of the NKG2D in Vitiligo

Vitiligo is an acquired multifactorial disease that affects melanocytes and results in skin depigmentation. In this review, we examine the role of cells stress and self-reactive T cells responses. Given the canonical and non-canonical functions of NKG2D, such as authenticating stressed target and enhance TCR signaling, we examine how melanocyte stress leads to the expression of ligands that are recognized by the activating receptor NKG2D, and how its signaling results in the turning of T cells against self (melanocyte suicide by proxy). We also discuss how this initiation phase is followed by T cell perpetuation, as NKG2D signaling results in self-sustained long-lasting T cells, with improved cytolytic properties.

Trial watch: Chemotherapy with immunogenic cell death inducers

The long-established notion that apoptosis would be immunologically silent, and hence it would go unnoticed by the immune system, if not tolerogenic, and hence it would actively suppress immune responses, has recently been revisited. In some instances, indeed, cancer cells undergo apoptosis while emitting a spatiotemporally-defined combination of signals that renders them capable of eliciting a long-term protective antitumor immune response. Importantly, only a few anticancer agents can stimulate such an immunogenic cell death. These include cyclophosphamide, doxorubicin and oxaliplatin, which are currently approved by FDA for the treatment of multiple hematologic and solid malignancies, as well as mitoxantrone, which is being used in cancer therapy and against multiple sclerosis. In this Trial Watch, we will review and discuss the progress of recent (initiated after January 2008) clinical trials evaluating the off-label use of cyclophosphamide, doxorubicin, oxaliplatin and mitoxantrone.

TLR-4 Signaling vs. Immune Checkpoints, miRNAs Molecules, Cancer Stem Cells, and Wingless-Signaling Interplay in Glioblastoma Multiforme-Future Perspectives

Toll-like-receptor (TLR) family members were detected in the central nervous system (CNS). TLR occurrence was noticed and widely described in glioblastomamultiforme (GBM) cells. After ligand attachment, TLR-4 reorients domains and dimerizes, activates an intracellular cascade, and promotes further cytoplasmatic signaling. There is evidence pointing at a strong relation between TLR-4 signaling and micro ribonucleic acid (miRNA) expression. The TLR-4/miRNA interplay changes typical signaling and encourages them to be a target for modern immunotherapy. TLR-4 agonists initiate signaling and promote programmed death ligand-1 (PD-1L) expression. Most of those molecules are intensively expressed in the GBM microenvironment, resulting in the autocrine induction of regional immunosuppression. Another potential target for immunotreatment is connected with limited TLR-4 signaling that promotes Wnt/DKK-3/claudine-5 signaling, resulting in a limitation of GBM invasiveness. Interestingly, TLR-4 expression results in bordering proliferative trends in cancer stem cells (CSC) and GBM. All of these potential targets could bring new hope for patients suffering from this incurable disease. Clinical trials concerning TLR-4 signaling inhibition/promotion in many cancers are recruiting patients. There is still a lot to do in the field of GBM immunotherapy.

Role of Heat Shock Proteins in Glaucoma

Glaucoma, one of the most common causes of blindness worldwide, is a multifactorial neurodegenerative disease characterized by damage of retinal ganglion cells and optic nerve degeneration. However, the exact mechanism leading to glaucoma is still not understood. Evidences suggest an immunological involvement in the pathogenesis. Among other immune responses, altered autoantibody patterns were found in glaucoma patients. Especially elevated antibody levels against heat shock proteins (HSPs), like HSP27 or HSP60, were identified. In an animal model, an immunization with these HSPs induced a pressure-independent retinal ganglion cell degeneration and axon loss, hence mimicking glaucoma-like damage. In addition, development of autoreactive antibodies, as well as a glia and T-cell activation, were described in these animals. Recently, we noted that intravitreal HSP27 injection likewise led to a degeneration of retinal ganglion cells and their axons. Therefore, HSP27 might have a direct damaging effect on retinal cells, and might play a key role in glaucoma.

Application of built-in adjuvants for epitope-based vaccines

Several studies have shown that epitope vaccines exhibit substantial advantages over conventional vaccines. However, epitope vaccines are associated with limited immunity, which can be overcome by conjugating antigenic epitopes with built-in adjuvants (e.g., some carrier proteins or new biomaterials) with special properties, including immunologic specificity, good biosecurity and biocompatibility, and the ability to vastly improve the immune response of epitope vaccines. When designing epitope vaccines, the following types of built-in adjuvants are typically considered: (1) pattern recognition receptor ligands (i.e., toll-like receptors); (2) virus-like particle carrier platforms; (3) bacterial toxin proteins; and (4) novel potential delivery systems (e.g., self-assembled peptide nanoparticles, lipid core peptides, and polymeric or inorganic nanoparticles). This review primarily discusses the current and prospective applications of these built-in adjuvants (i.e., biological carriers) to provide some references for the future design of epitope-based vaccines.

Transcriptomic insights into the early host-pathogen interaction of cat intestine with Toxoplasma gondii

Background

Although sexual reproduction of the parasite Toxoplasma gondii exclusively occurs in the cat intestine, knowledge about the alteration of gene expression in the intestine of cats infected with T. gondii is still limited. Here, we investigated the temporal transcriptional changes that occur in the cat intestine during T. gondii infection.

Methods

Cats were infected with 100 T. gondii cysts and their intestines were collected at 6, 12, 18, 24, 72 and 96 hours post-infection (hpi). RNA sequencing (RNA-Seq) Illumina technology was used to gain insight into the spectrum of genes that are differentially expressed due to infection. Quantitative RT-PCR (qRT-PCR) was also used to validate the level of expression of a set of differentially expressed genes (DEGs) obtained by sequencing.

Results

Our transcriptome analysis revealed 2363 DEGs that were clustered into six unique patterns of gene expression across all the time points after infection. Our analysis revealed 56, 184, 404, 508, 400 and 811 DEGs in infected intestines compared to uninfected controls at 6, 12, 18, 24, 72 and 96 hpi, respectively. RNA-Seq results were confirmed by qRT-PCR. DEGs were mainly enriched in catalytic activity and metabolic process based on gene ontology enrichment analysis. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that transcriptional changes in the intestine of infected cats evolve over the course of infection, and the largest difference in the enriched pathways was observed at 96 hpi. The anti-T. gondii defense response of the feline host was mediated by Major Histocompatibility Complex class I, proteasomes, heat-shock proteins and fatty acid binding proteins.

Conclusions

This study revealed novel host factors, which may be critical for the successful establishment of an intracellular niche during T. gondii infection in the definitive feline host.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3179-8) contains supplementary material, which is available to authorized users.

Endocytosed soluble cowpox virus protein CPXV012 inhibits antigen cross-presentation in human monocyte-derived dendritic cells

Viruses may interfere with the MHC class I antigen presentation pathway in order to avoid CD8⁺ T cell-mediated immunity. A key target within this pathway is the peptide transporter TAP. This transporter plays a central role in MHC class I-mediated peptide presentation of endogenous antigens. In addition, TAP plays a role in antigen cross-presentation of exogenously derived antigens by dendritic cells (DCs). In this study, a soluble form of the cowpox virus TAP inhibitor CPXV012 is synthesized for exogenous delivery into the antigen cross-presentation route of human monocyte-derived (mo)DCs. We show that soluble CPXV012 localizes to TAP⁺ compartments that carry internalized antigen and is a potent inhibitor of antigen cross-presentation. CPXV012 stimulates the prolonged deposition of antigen fragments in storage compartments of moDCs, as a result of reduced endosomal acidification and reduced antigen proteolysis when soluble CPXV012 is present. Thus, a dual function can be proposed for CPXV012: inhibition of TAP-mediated peptide transport and inhibition of endosomal antigen degradation. We propose this second function for soluble CPXV012 can serve to interfere with antigen cross-presentation in a peptide transport-independent manner.

Hsp70: A Cancer Target Inside and Outside the Cell

Heat shock protein 70 (Hsp70) is the most ubiquitous stress-inducible chaperone. It accumulates in the cells in response to a wide variety of physiological and environmental insults including anticancer chemotherapy, thus allowing the cell to survive to lethal conditions. Intracellular Hsp70 is viewed as a cytoprotective protein. Indeed, this protein can inhibit key effectors of the apoptotic and autophagy machineries. In cancer cells, the expression of Hsp70 is abnormally high, and Hsp70 may participate in oncogenesis and in resistance to chemotherapy. In rodent models, Hsp70 overexpression increases tumor growth and metastatic potential. Depletion or inhibition of Hsp70 frequently reduces the size of the tumors and can even cause their complete involution. However, HSP70 is also found in the extra-cellular space where it may signal via membrane receptors or endosomes to alter gene transcription and cellular function. Overall, Hsp70 extracellular function is believed to be immnunogenic and the term chaperokine to define the extracellular chaperones such as Hsp70 has been advanced. In this chapter the knowledge to date, as well as some emerging paradigms about the intra- and extra-cellular functions of Hsp70, are presented. The strategies targeting Hsp70 that are being developed in cancer therapy will also be discussed.

Innate and Adaptive Mucosal Immunity in Protection against HIV Infection

The appalling toll on the populations of developing countries as a result of the HIV epidemic shows no signs of abatement. While costly drug therapies are effective in developed nations, the sheer scale of the epidemic elsewhere makes the need for a vaccine an ever more urgent goal. The prevalent DNA prime-viral boost strategy aims to elicit cytotoxic lymphocytes (CTL) against HIV, but this approach is undermined by the rapid mutation of HIV, which thereby escapes CTL control. Alloimmunity has been found to be protective in vertical transmission from infected mothers to their babies, in alloimmunization of women with their partners’ mononuclear cells, and in monkeys immunized with SIV grown in human T-cells. Vaginal mucosal immunization, as a result of unprotected sex with a regular partner, induced in vitro protection against HIV infection, and this was confirmed in macaques. The second type of natural protection is found in persons with the homozygous Δ32 CCR5 mutation, a 32-base-pair deletion of the CCR5 gene, which results in a lack of cell-surface expression of CCR5, which is associated with an increase in CC chemokines and the development of CCR5 antibodies. These two ‘experiments of nature’ have been used to develop vaccine strategies—first, in vaginal immunization of macaques with CCR5 peptides, in addition to HIV envelope (env) and SIV core (gag) antigens, all of which were linked to the 70-kD heat-shock protein (HSP70); and second, in mucosal allo-immunization of macaques, which also gave rise to in vitro protection from infection. Immunization with this vaccine elicited serum and vaginal IgG and IgA antibodies, IFNγ- and IL-12-producing cells, and increased concentrations of CCL-3 and CCL-4. Vaginal challenge with a simian immunodeficiency virus engineered to carry a human envelope protein (SHIV 89.6) showed significant clearance of SHIV in the immunized macaques. This platform strategy will now be developed to activate the co-stimulatory pathways with the aim of enhancing the primary allogeneic and CCR5-directed responses which are involved in natural protection against HIV infection. Abbreviations: IFN-γ, gamma interferon; IL-12, interleukin 12; MIP-1 α,β, Macrophage inflammatory protein-1; RANTES, Regulated on activation normal T-cell expressed and secreted; SDF-1, stromal-derived factor 1; SIV, simian immunodeficiency virus; and SHIV, engineered SIV carrying a human envelope protein.

Targeting Hsp70: A possible therapy for cancer

In all organisms, heat-shock proteins (HSPs) provide an ancient defense system. These proteins act as molecular chaperones by assisting proper folding and refolding of misfolded proteins and aid in the elimination of old and damaged cells. HSPs include Hsp100, Hsp90, Hsp70, Hsp40, and small HSPs. Through its substrate-binding domains, Hsp70 interacts with wide spectrum of molecules, ranging from unfolded to natively folded and aggregated proteins, and provides cytoprotective role against various cellular stresses. Under pathophysiological conditions, the high expression of Hsp70 allows cells to survive with lethal injuries. Increased Hsp70, by interacting at several points on apoptotic signaling pathways, leads to inhibition of apoptosis. Elevated expression of Hsp70 in cancer cells may be responsible for tumorigenesis and for tumor progression by providing resistance to chemotherapy. In contrast, inhibition or knockdown of Hsp70 reduces the size of tumors and can cause their complete regression. Moreover, extracellular Hsp70 acts as an immunogen that participates in cross presentation of MHC-I molecules. The goals of this review are to examine the roles of Hsp70 in cancer and to present strategies targeting Hsp70 in the development of cancer therapeutics.

Combinatorial prospects of nano-targeted chemoimmunotherapy

Despite the significant increase in our knowledge on cancer initiation and progression, and the development of novel cancer treatments, overall patient survival rates have thus far only marginally improved. However, it can be expected that lasting tumor control will be attainable for an increasing number of cancer patients in the foreseeable future, which is likely to be achieved by combining cancer chemotherapy with anticancer immunotherapy. A plethora of new cancer chemotherapy reagents are expected to become accessible to the clinic in the coming years which can then be used for efficient tumor debulking and aid in antigen exposure to the immune system. Durable remission and the eradication of micrometastases are likely to be achieved with specialized monoclonal antibodies and therapeutic cancer vaccines that modulate the immune system to overcome immunosuppression and kill distant cancer cells. Moreover, the method of drug delivery to tumors, stromal and immune cells is expected to shift largely from conventional 'free' drug molecules to encapsulated in targeted nano-vehicles, therapeutics often referred to or considered part of "nanomedicine". Several biocompatible nano-vehicles, such as metal-nanoparticles, biodegradable-nanoparticles, liposomes or dendrimers are potential candidates for targeted drug delivery but may also serve additional purposes. A dexterous combination of nanomedicine, cancer immunotherapy and chemotherapeutic engineering are likely to become the basis for new hope in the form of targeted cancer therapies that could attack tumors early in their development. One can envision nano-vehicles that would selectively deliver effective doses of chemotherapeutic agents to cancer cells while leaving healthy cells untouched. Furthermore, given that after chemotherapeutic treatment there often remains a limited number of chemo-resistant tumor cells, which go on to drive tumor progression, nano-vehicles could also be engineered to provoke an appropriate immune response to destroy these cells. Here, we discuss the potential of the combinatorial role of cancer chemotherapy, cancer immunotherapy and the prospective of nanotechnology for the targeted delivery of chemoimmunotherapeutic agents.

Suppression of established hepatocarcinoma in adjuvant only immunotherapy: alum triggers anti-tumor CD8+ T cell response

Dendritic cell-based immunotherapy is a new weapon in our battle against malignancies in human. Recent trials in human and research work in model animals have shown various degrees of success, suggesting its great potential for clinical use. While protocols vary, a common scheme in this category of treatment involves activation of dendritic cells, with the purpose of increasing antigen presentation and cellular immunity. Therefore, proper use of immune adjuvant is a central subject of study. We report here an unexpected finding that injection of alum, the most widely used human adjuvant, into mice carrying H22 hepatocarcinoma resulted in a significant reduction of tumor growth with extended animal survival. This effect was associated with an increased specific CD8(+) T cell activation and an inflammatory environment, yet with minimal overt side effects. Our finding suggests that use of adjuvant alone in certain established tumors can invoke protective host immune activation against the same target, which may be of value in our development of new cancer immunotherapies.

CD28-mediated T cell response is upregulated by exogenous application of autologous Hsp70-peptide complex in a tumor-bearing host

Hsp70, a highly conserved protein, has gained plenty of attention by virtue of its adjuvant capability to induce peptide-specific cytotoxic T lymphocyte responses. In this study, we have investigated the effect of autologous Hsp70-peptide complex (or simply autologous Hsp70) on the expression of CD28 on T cells and its effector functions through macrophage activation. Further, we investigated the effect of Hsp70 on the expression of CD80 and CD86 on macrophages isolated from normal and tumor-bearing host to provide costimulatory signal for T cell activation and secretion of IL-2 and IFN-γ during interaction. We found that treatment of autologous Hsp70 effectively activated TAMs to induce higher expression of CD28 on T cells through T cells-macrophage interaction. Treatment of autologous Hsp70 induces higher expression of CD80 and CD86 on TAMs, as a result, increases B7/CD28 interaction, which in turns activates T cells and induces higher production of IL-2 and IFN-γ, thereby increasing antigen-specific T cell proliferation. With our novel study, we have provided the strong insights into the role of extracellular Hsp70 on the expression of CD28 costimulatory molecule on T cells, which helps in the activation and generation of antigen-specific T cell effector functions in a tumor-bearing host to curb malignancy.

Heat shock protein vaccines against glioblastoma: from bench to bedside

Current adjuvant treatment regimens available for the treatment of glioblastoma are widely ineffective and offer a dismal prognosis. Advancements in conventional treatment strategies have only yielded modest improvements in overall survival. Immunotherapy remains a promising adjuvant in the treatment of GBM through eliciting tumor specific immune responses capable of producing sustained antitumor response while minimizing systemic toxicity. Heat shock proteins (HSP) function as intracellular chaperones and have been implicated in the activation of both innate and adaptive immune systems. Vaccines formulated from HSP-peptide complexes, derived from autologous tumor, have been applied to the field of immunotherapy for glioblastoma. The results from the phase I and II clinical trials have been promising. Here we review the role of HSP in cellular function and immunity, and its application in the treatment of glioblastoma.

Endotoxin-minimized HIV-1 p24 fused to murine hsp70 activates dendritic cells, facilitates endocytosis and p24-specific Th1 response in mice

Heat shock proteins hsp70 and gp96 have been confirmed as adjuvants enabling induction of cell- and antibody-mediated immunity specific to associated protein or peptide antigens due to the activation of naive dendritic cells and supporting cross-presentation of associated antigen. An efficacious vaccine preventing HIV-1 infection should induce (1) antibodies neutralizing HIV-1 Env protein, preventing virus spreading and (2) CD4(+) Th1 and CD8(+) T cells specific to viral proteins, especially gag p24, important for elimination of HIV-1 infected cells. As p24 is relatively poorly recognized by dendritic cells, its targeting to DC is important for enhancement of vaccine efficacy. In this study, a p24 protein fused to the C- or N-terminus of murine hsp70 was produced as a recombinant protein and administered without any adjuvant to experimental BALB/c mice. Consequently, p24-specific cellular and humoral immune responses were measured. To minimize the effect of bacterial endotoxin, each protein was subjected to a repeated endotoxin phase extraction until each preparation contained less than 2.5 endotoxin unit (EU) per mg of antigen. In addition, endocytosis of p24 fused to hsp70 by dendritic cells and their activation were characterized. The fusion to hsp70 protein enhanced endocytosis of p24 as well as activation of dendritic cells in vitro. After immunization of mice, hsp70-p24 fusion protein induced the strongest p24-specific CD4(+) and CD8(+) T cells (IFN-γ production) and humoral (IgG2b) responses corresponding to Th1 type dominance, whereas p24-hsp70 or p24 itself induced weaker responses.

Hyperthermic intraperitoneal chemotherapy leads to an anticancer immune response via exposure of cell surface heat shock protein 90

The occurrence of peritoneal carcinomatosis is a major cause of treatment failure in colorectal cancer and is considered incurable. However, new therapeutic approaches have been proposed, including cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC). Although HIPEC has been effective in selected patients, it is not known how HIPEC prolongs a patient's lifespan. Here, we have demonstrated that HIPEC-treated tumor cells induce the activation of tumor-specific T cells and lead to vaccination against tumor cells in mice. We have established that this effect results from the HIPEC-mediated exposure of heat shock protein (HSP) 90 at the plasma membrane. Inhibition or blocking of HSP90, but not HSP70, prevented the HIPEC-mediated antitumoral vaccination. Our work raises the possibility that the HIPEC procedure not only kills tumor cells but also induces an efficient anticancer immune response, therefore opening new opportunities for cancer treatment.

MHC structure and function - antigen presentation. Part 2

The second part of this review deals with the molecules and processes involved in the processing and presentation of the antigenic fragments to the T-cell receptor. Though the nature of the antigens presented varies, the most significant class of antigens is proteins, processed within the cell to be then recognized in the form of peptides, a mechanism that confers an extraordinary degree of precision to this mode of immune response. The efficiency and accuracy of this system is also the result of the myriad of mechanisms involved in the processing of proteins and production of peptides, in addition to the capture and recycling of alternative sources aiming to generate further diversity in the presentation to T-cells.

Redirecting soluble antigen for MHC class I cross-presentation during phagocytosis

Peptides presented by MHC class I molecules are mostly derived from proteins synthesized by the antigen-presenting cell itself, while peptides presented by MHC class II molecules are predominantly from materials acquired by endocytosis. External antigens can also be presented by MHC class I molecules in a process referred to as cross-presentation. Here, we report that mouse dendritic cell (DC) engagement to a phagocytic target alters endocytic processing and inhibits the proteolytic activities. During phagocytosis, endosome maturation is delayed, shows less progression toward the lysosome, and the endocytosed soluble antigen is targeted for MHC class I cross-presentation. The antigen processing in these arrested endosomes is under the control of NAPDH oxidase associated ROS. We also show that cathepsin S is responsible for the generation of the MHC class I epitope. Taken together, our results suggest that in addition to solid structure uptake, DC phagocytosis simultaneously modifies the kinetics of endosomal trafficking and maturation. As a consequence, external soluble antigens are targeted into the MHC class I cross-presentation pathway.

Trial watch: Chemotherapy with immunogenic cell death inducers

It is now clear that the immune system plays a critical role not only during oncogenesis and tumor progression, but also as established neoplastic lesions respond to therapy. Selected cytotoxic chemicals can indeed elicit immunogenic cell death, a functionally peculiar type of apoptosis that stimulates tumor-specific cognate immune responses. Such immunogenic chemotherapeutics include cyclophosphamide, doxorubicin and oxaliplatin (which are approved by FDA for the treatment of various hematological and solid malignancies), mitoxantrone (which is currently employed both as an anticancer agent and against multiple sclerosis) and patupilone (a microtubular poison in clinical development). One year ago, in the second issue of OncoImmunology, we discussed the scientific rationale behind immunogenic chemotherapy and reviewed the status of recent clinical trials investigating the off-label use of cyclophosphamide, doxorubicin, oxaliplatin and mitoxantrone in cancer patients. Here, we summarize the latest developments in this area of clinical research, covering both high-impact studies that have been published during the last 13 months and clinical trials that have been initiated in the same period to assess the antineoplastic profile of immunogenic chemotherapeutics.

Effect of vaginal immunization with HIVgp140 and HSP70 on HIV-1 replication and innate and T cell adaptive immunity in women

The international effort to prevent HIV-1 infection by vaccination has failed to develop an effective vaccine. The aim of this vaccine trial in women was to administer by the vaginal mucosal route a vaccine consisting of HIV-1 gp140 linked to the chaperone 70-kDa heat shock protein (HSP70). The primary objective was to determine the safety of the vaccine. The secondary objective was to examine HIV-1 infectivity ex vivo and innate and adaptive immunity to HIV-1. Protocol-defined female volunteers were recruited. HIV-1 CN54gp140 linked to HSP70 was administered by the vaginal route. Significant adverse reactions were not detected. HIV-1 was significantly inhibited ex vivo in postimmunization CD4(+) T cells compared with preimmunization CD4(+) T cells. The innate antiviral restrictive factor APOBEC3G was significantly upregulated, as were CC chemokines which induce downregulation of CCR5 in CD4(+) T cells. Indeed, a significant inverse correlation between the proportion of CCR5(+) T cells and the concentration of CCL-3 or CCL-5 was found. Importantly, the upregulation of APOBEC3G showed a significant inverse correlation, whereas CCR5 exhibited a trend to correlate with inhibition of HIV-1 infection (r = 0.51). Furthermore, specific CD4(+) and CD8(+) T cell proliferative responses were significantly increased and CD4(+) T cells showed a trend to have an inverse correlation with the viral load (r = -0.60). However, HIVgp140-specific IgG or IgA antibodies were not detected. The results provide proof of concept that an innate mechanism consisting of CC chemokines, APOBEC3G, and adaptive immunity by CD4 and CD8 T cells might be involved in controlling HIV-1 infectivity following vaginal mucosal immunization in women. (This study has been registered at ClinicalTrials.gov under registration no. NCT01285141.) Importance: Vaginal immunization of women with a vaccine consisting of HIVgp140 linked to the 70-kDa heat shock protein (HSP70) elicited ex vivo significant inhibition of HIV-1 replication in postimmunization CD4(+) T cells compared with that in preimmunization peripheral blood mononuclear cells. There were no significant adverse events. The vaccine induced the significant upregulation of CC chemokines and the downmodulation of CCR5 expression in CD4(+) T cells, as well as an inverse correlation between them. Furthermore, the level of CCR5 expression was directly correlated with the viral load, consistent with the protective mechanism in which a decrease in CCR5 molecules on CD4(+) T cells decreases HIV-1 envelope binding. Expression of the antiviral restriction factor APOBEC3G was inversely correlated with the viral load, suggesting that it may inhibit intracellular HIV-1 replication. Both CD4(+) and CD8(+) T cells showed HIVgp140- and HSP70-specific proliferation. A strong inverse correlation between the proportion of CC chemokine-modulated CCR5-expressing CD4(+) T cells and the stimulation of CD4(+) or CD8(+) T cell proliferation by HIVgp140 was found, demonstrating a significant interaction between innate and adaptive immunity. This is the first clinical trial of vaginal immunization in women using only HIVgp140 and HSP70 administered by the mucosal route (3 times) in which a dual innate protective mechanism was induced and enhanced by significant adaptive CD4(+) and CD8(+) T cell proliferative responses.

The impact of macroautophagy on CD8(+) T-cell-mediated antiviral immunity

Macroautophagy is a catabolic recycling pathway, which can be induced by various stress stimuli. Viruses are able to manipulate autophagy in the cells that they infect. The impact of autophagy on the innate immune response to viruses and its stimulatory role in antigen presentation to CD4(+) T cells are well documented. Herein, we present the impact of autophagy on the activation of cytotoxic T lymphocyte (CTL)-mediated antiviral immune responses, which are required for the eradication or control of multiple viruses. We first discuss the general mechanisms by which viruses can either induce or block autophagy in cells. We then explore the cross-talk between autophagy and innate immune processes, which are both first line defenses against viruses; and constitute crucial steps for the initiation of potent adaptive immune responses. We describe the impact of autophagy on the presentation of viral peptide antigens on class I major histocompatibility complex (MHC I), a prerequisite for the priming of CTL responses. In sum, our review highlights the interplay between viruses and three integrated host response pathways - autophagy, innate and adaptive immunity - providing a framework for future mechanistic and pathogenesis-based research.

Heat-shock proteins-based immunotherapy for advanced melanoma in the era of target therapies and immunomodulating agents

INTRODUCTION

Heat-shock proteins (HSPs) are highly conserved, stress-induced proteins that function as chaperones, stabilizing proteins and delivering peptides. Tumor-derived HSP peptide complexes (HSPPCs) induced immunity against several malignancies in preclinical models, exhibiting activity across tumor types.

AREAS COVERED

HSPPC-based vaccination showed clinical activity in subsets of patients with different malignancies (e.g., gastric, colorectal, pancreatic, ovarian cancer, and glioblastoma). In Phase III clinical trials for advanced melanoma and renal cell carcinoma patients, HSPPC-based vaccine demonstrated an excellent safety profile, thus emerging as a flexible tumor- and patient-specific therapeutic approach.

EXPERT OPINION

Melanoma, renal clear cell carcinoma, and glioblastoma are among suitable targets for HSP-based treatment as demonstrated by immune responses and clinical activity observed in subsets of patients, mainly those with early stage of disease and limited tumor burden. In order to further improve clinical activity, combinations of HSPPC-based vaccines with mutation-driven therapies, antiangiogenic agents, or immunomodulating monoclonal antibodies should be tested in controlled clinical trials.

Induction of specific humoral and cellular immune responses in a mouse model following gene fusion of HSP70C and Hantaan virus Gn and S0.7 in an adenoviral vector

Heat shock proteins (HSPs) display adjuvant functions when given as fusion proteins to enhance vaccination efficiency. To evaluate enhanced potency of Hantaan virus (HTNV) glycoprotein (GP) and nucleocapsid protein (NP) immunogenicity by heat shock protein 70 (HSP70), a recombinant adenovirus rAd-GnS0.7-pCAG-HSP70C expression vector was developed by genetically linking the HSP70 C-terminal gene (HSP70 359-610 aa, HSP70C) to the Gn and 0.7 kb fragment of the NP (aa1-274-S0.7). C57BL/6 mice were immunized with these recombinant adenoviral vectors. A series of immunological assays determined the immunogenicity of the recombinant adenoviral vectors. The results showed that rAd-GnS0.7-pCAG-HSP70C induced a stronger humoral and cellular immune response than other recombinant adenoviruses (rAd-GnS0.7-pCAG and rAd-GnS0.7) and the HFRS vaccine control. Animal protection experiments showed that rAd-GnS0.7-pCAG-HSP70C was effective at protecting C57BL/6 mice from HTNV infection. The results of the immunological experiments showed that HSP70C lead to enhanced vaccine potency, and suggested significant potential in the development of genetically engineered vaccines against HTNV.

Fusion of Hsp70 to Mage-a1 enhances the potency of vaccine-specific immune responses

Background

Heat shock proteins (HSPs) are capable of promoting antigen presentation of chaperoned peptides through interactions with receptors on antigen presenting cells. This property of HSPs suggests a potential function as an adjuvant-free carrier to stimulate immune responses against a covalently linked fusion partner. MAGE-A1 is a likely candidate for tumor immunotherapy due to its abundant immunogenic epitopes and strict tumor specificity. To analyze the influence of HSP70 conjugation to MAGE-A1, towards developing a novel effective vaccine against MAGE-expressing tumors, we cloned the murine counterpart of the human HSP70 and MAGE-A1 genes.

Methods

Recombinant proteins expressing Mage-a1 (aa 118–219), Hsp70, and Mage-a1-Hsp70 fusion were purified and used to immunize C57BL/6 mice. The humoral and cellular responses elicited against Mage-a1 were measured by ELISA, IFN-γ ELISPOT assay, and cytotoxicity assay.

Results

Immunization of mice with Mage-a1-Hsp70 fusion protein elicited significantly higher Mage-a1-specific antibody titers than immunization with either Mage-a1 alone or a combination of Mage-a1 + Hsp70. The frequency of IFN-γ-producing cells and the cytotoxic T lymphocyte (CTL) activity was also elevated. Consistent with the elevated immune response, immunization with fusion protein induced potent in vivo antitumor immunity against MAGE-a1-expressing tumors.

Conclusions

These results indicate that the fusion of Hsp70 to Mage-a1 can enhance immune responses and anti-tumor effects against Mage-a1-expressing tumors. Fusion of HSP70 to a tumor antigen may greatly enhance the potency of protein vaccines and can potentially be applied to other cancer systems with known tumor-specific antigens. These findings provide a scientific basis for the development of a novel HSP70 and MAGE fusion protein vaccine against MAGE-expressing tumors.

High molecular weight stress proteins: Identification, cloning and utilisation in cancer immunotherapy

Although the large stress/heat shock proteins (HSPs), i.e. Hsp110 and Grp170, were identified over 30 years ago, these abundant and highly conserved molecules have received much less attention compared to other conventional HSPs. Large stress proteins act as molecular chaperones with exceptional protein-holding capability and prevent the aggregation of proteins induced by thermal stress. The chaperoning properties of Hsp110 and Grp170 are integral to the ability of these molecules to modulate immune functions and are essential for developing large chaperone complex vaccines for cancer immunotherapy. The potent anti-tumour activity of the Hsp110/Grp170-tumour protein antigen complexes demonstrated in preclinical studies has led to a phase I clinical trial through the National Cancer Institute's rapid access to intervention development (RAID) programme that is presently underway. Here we review aspects of the structure and function of these large stress proteins, their roles as molecular chaperones in the biology of cell stress, and prospects for their use in immune regulation and cancer immunotherapy. Lastly, we will discuss the recently revealed immunosuppressive activity of scavenger receptor A that binds to Hsp110 and Grp170, as well as the feasibility of targeting this receptor to promote T-cell activation and anti-tumour immunity induced by large HSP vaccines and other immunotherapies.

Heat shock proteins: stimulators of innate and acquired immunity

Adjuvants were reintroduced into modern immunology as the dirty little secret of immunologists by Janeway and thus began the molecular definition of innate immunity. It is now clear that the binding of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) on antigen presenting cells (APCs) activates the innate immune response and provides the host with a rapid mechanism for detecting infection by pathogens and initiates adaptive immunity. Ironically, in addition to advancing the basic science of immunology, Janeway's revelation on induction of the adaptive system has also spurred an era of rational vaccine design that exploits PRRs. Thus, defined PAMPs that bind to known PRRs are being specifically coupled to antigens to improve their immunogenicity. However, while PAMPs efficiently activate the innate immune response, they do not mediate the capture of antigen that is required to elicit the specific responses of the acquired immune system. Heat shock proteins (HSPs) are molecular chaperones that are found complexed to client polypeptides and have been studied as potential cancer vaccines. In addition to binding PRRs and activating the innate immune response, HSPs have been shown to both induce the maturation of APCs and provide chaperoned polypeptides for specific triggering of the acquired immune response.

Hsp72 mediates stronger antigen-dependent non-classical MHC class Ib anti-tumor responses than hsc73 in Xenopus laevis

The heat shock proteins (HSPs) gp96 and HSP70 mediate potent antigen-dependent anti-tumor T cell responses in both mammals and Xenopus laevis. We have shown that frogs immunized with total HSP70 generate CD8+ T cell responses against the Xenopus thymic lymphoid tumor 15/0 that expresses several non-classical MHC class Ib (class Ib) genes, but no classical MHC class Ia (class Ia). In the absence of class Ia, we hypothesized that hsp72 can prime class Ib-mediated anti-tumor unconventional CD8+ T cells in an antigen-dependent manner. To test this, we produced Xenopus recombinant HSP70 proteins (both the cognate hsc73 and the inducible hsp72) from stable 15/0 tumor transfectants. We used an in vivo cross-presentation assay to prime animals by adoptive transfer of HSP-pulsed antigen-presenting cells (APCs) and showed that both hsp72-and hsc73-Ag complexes have a similar potential to elicit class Ia-mediated T cell responses against minor histocompatibility (H) Ag skin grafts. In contrast, our in vivo cross-presentation assay revealed that hsp72 was more potent than hsc73 in generating protective immune responses against the class Ia-negative 15/0 tumors in an Ag-dependent and class Ib-mediated manner. These results suggest that hsp72 can stimulate class Ib-mediated immune responses and represents a promising candidate for immunotherapy against malignancies with downregulated class Ia expression.

Pathways of antigen processing

T cell recognition of antigen-presenting cells depends on their expression of a spectrum of peptides bound to major histocompatibility complex class I (MHC-I) and class II (MHC-II) molecules. Conversion of antigens from pathogens or transformed cells into MHC-I- and MHC-II-bound peptides is critical for mounting protective T cell responses, and similar processing of self proteins is necessary to establish and maintain tolerance. Cells use a variety of mechanisms to acquire protein antigens, from translation in the cytosol to variations on the theme of endocytosis, and to degrade them once acquired. In this review, we highlight the aspects of MHC-I and MHC-II biosynthesis and assembly that have evolved to intersect these pathways and sample the peptides that are produced.

CD91-Dependent Modulation of Immune Responses by Heat Shock Proteins: A Role in Autoimmunity

Heat shock proteins (HSPs) have been known for decades for their ability to protect cells under stressful conditions. In the 1980s a new role was ascribed for several HSPs given their ability to elicit specific immune responses in the setting of cancer and infectious disease. These immune responses have primarily been harnessed for the immunotherapy of cancer in the clinical setting. However, because of the ability of HSPs to prime diverse immune responses, they have also been used for modulation of immune responses during autoimmunity. The apparent dichotomy of immune responses elicited by HSPs is discussed here on a molecular and cellular level. The potential clinical application of HSP-mediated immune responses for therapy of autoimmune diseases is reviewed.

An anti-nucleic acid antibody delivers antigen to the cross-presentation pathway in dendritic cells and potentiates therapeutic antitumor effects

Cross-presentation is important for initiating CTL responses against tumors. Delivery of exogenous Ags to the cross-presentation pathway in dendritic cells (DCs), using a number of different carriers, has been attempted to further understand the mechanisms underlying cross-presentation and to develop therapeutic tumor vaccines. The present study reports a new antigenic carrier molecule: a single-chain V region fragment (scFv) of a nucleic acid-hydrolyzing Ab, 3D8. A fusion protein comprising 3D8 scFv and the CTL epitope OVA(250-264) (chicken OVA aa 250-264) was internalized by DC2.4 DCs and processed via a proteasome-dependent, brefeldin- and cycloheximide-sensitive, chloroquine- and primaquine-insensitive pathway, resulting in loading of the CTL epitope onto H-2K(b). In vivo cross-presentation and cross-priming were efficient, even without adjuvant; injection of mice with 3D8 scFv-OVA(250-264) induced cross-presentation of the CTL epitope by draining lymph node CD11c(+) B7.1(+) MHC class II(high) DCs, elicited a CTL response, and suppressed the growth of tumors expressing the OVA epitope. This report shows that an anti-nucleic acid Ab is used to deliver exogenous Ag to the cross-presentation pathway and inhibit in vivo tumor growth.

Increasing the efficacy of tumor cell vaccines by enhancing cross priming

Cancer immunotherapy has been attempted for more than a century, and investment has intensified in the last 20 years. The complexity of the immune system is exemplified by the myriad of immunotherapeutic approaches under investigation. While anti-tumor immunity has been achieved experimentally with multiple effector cells and molecules, particular promise is shown for harnessing the CD8 T cell response. Tumor cell-based vaccines have been employed in hundreds of clinical trials to date and offer several advantages over subunit and peptide vaccines. However, tumor cell-based vaccines, often aimed at cross priming tumor-reactive CD8 T cells, have shown modest success in clinical trials. Here we review the mechanisms of cross priming and discuss strategies to increase the efficacy of tumor cell-based vaccines. A synthesis of recent findings on tissue culture conditions, cell death, and dendritic cell activation reveals promising new avenues for clinical investigation.

In contrast to conventional inactivated influenza vaccines, 4xM2e.HSP70c fusion protein fully protected mice against lethal dose of H1, H3 and H9 influenza A isolates circulating in Iran

Ideal vaccines against influenza viruses should elicit not only a humoral response, but also a cellular response. Mycobacterium tuberculosis HSP70 (mHSP70) have been found to promote immunogenic APCs function, elicit a strong cytotoxic T lymphocyte (CTL) response, and prevent the induction of tolerance. Moreover, it showed linkage of antigens to the C-terminus of mHSP70 (mHSP70c) can represent them as vaccines resulted in more potent, protective antigen specific responses in the absence of adjuvants or complex formulations. Hence, recombinant fusion protein comprising C-terminus of mHSP70 genetically fused to four tandem repeats of the ectodomain of the conserved influenza matrix protein M2 (M2e) was expressed in Escherichia coli, purified under denaturing condition, refolding, and then confirmed by SDS-PAGE, respectively. The recombinant fusion protein, 4xM2e.HSP70c, retained its immunogenicity and displayed the protective epitope of M2e by ELISA and FITC assays. A prime-boost administration of 4xM2e.HSP70c formulated in F105 buffer by intramuscular route in mice (Balb/C) provided full protection against lethal dose of mouse-adapted H1N1, H3N2, or H9N2 influenza A isolates from Iran compared to 0-33.34% survival rate of challenged unimmunized and immunized mice with the currently in use conventional vaccines designated as control groups. However, protection induced by immunization with 4xM2e.HSP70c failed to prevent weight loss in challenged mice; they experienced significantly lower weight loss, clinical symptoms and higher lung viral clearance in comparison with protective effects of conventional influenza vaccines in challenged mice. These data demonstrate that C-terminal domain of mHSP70 can be a superior candidate to deliver the adjuvant function in M2e-based influenza A vaccine in order to provide significant protection against multiple influenza A virus strains.

DNA immunization with HBsAg-based particles expressing a B cell epitope of amyloid β-peptide attenuates disease progression and prolongs survival in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is an incurable and progressive neurodegenerative senile disorder associated with the brain accumulation of Aβ plaques. Although vaccines that reduce Aβ plaques can control AD, the rationale for their use at the onset of the disease remains debatable. Old humans and mice usually respond poorly to vaccines due to presumably age-related immunological impairments. Here, we report that by modifying vaccines, the poor responsiveness of old mice can be reversed. Unlike the Aβ peptide vaccine, DNA immunizations with the amino-terminal Aβ(1-11) fragment exposed on the surface of HBsAg particles elicit high levels of anti-Aβ antibody both in young and old mice. Importantly, in AD model 3xTgAD mice, the vaccine reduced Aβ plaques, ameliorated cognitive impairments and, surprisingly, significantly increased life span. Hence, we propose that vaccines targeting Aβ(1-11) can efficiently combat AD-induced pathological alterations and provide survival benefit in patients with AD.

Heat shock protein 70/peptide complexes: potent mediators for the generation of antiviral T cells particularly with regard to low precursor frequencies

Background

Heat shock protein 70 (HSP70) has gained major attention as an adjuvant capable of inducing antigen-specific CD8⁺ and CD4⁺ T-cell responses. The ability of HSP70/peptide complexes to elicit cytotoxic T-cell (CTL) responses by cross-presentation of exogenous antigens via HLA class I molecules is of central interest in immunotherapy. We examined the role of HSP70/CMVpp65_495-503-peptide complex (HSP70/CMV-PC) in HLA class I-restricted cross-presentation for ex vivo expansion of CMV-specific CTLs.

Methods

CMV-specific T cells generated from PBMCs of HLA-A*02:01/CMV-seropositive donors were stimulated for 21 days with HSP70/CMV-PC and analyzed in functional assays. As a control PBMCs were cultured in the presence of CMVpp65_495-503 peptide or HSP70. Increase of CMV-specific CTLs was visualized by pentameric HLA-A*02:01/CMVpp65_495-503 complex.

Results

About 90% of HSP70/CMV-PC generated T cells were CMV-specific and exhibited significantly higher IFN-γ secretion, cytotoxic activity, and an increased heme oxygenase 1 (HO-1) gene expression as compared to about 69% of those stimulated with CMVpp65_495-503 peptide. We decided to classify the HLA-A*02:01/CMV-seropositive donors as weak, medium, and strong responder according to the frequency of generated A2/CMV-pentamer-positive CD8⁺ T cells. HSP70/CMV-PC significantly induces strong antiviral T-cell responses especially in those donors with low memory precursor frequencies. Blockage of CD91 with α2-macroglobulin markedly reduced proliferation of antiviral T cells suggesting a major role of this receptor in the uptake of HSP70/CMV-PC.

Conclusion

This study clearly demonstrates that HSP70/CMV-PC is a potent mediator to induce stronger T-cell responses compared to antiviral peptides. This simple and efficient technique may help to generate significant quantities of antiviral CTLs by cross-presentation. Thus, we propose HSP70 for chaperoning peptides to reach an efficient level of cross-presentation. HSP70/peptide complexes may be particularly useful to generate stronger T-cell responses in cases of low precursor frequencies and may help to improve the efficiency of antigen-specific T-cell therapy for minor antigens.

Safety and immunogenicity of long HSV-2 peptides complexed with rhHsc70 in HSV-2 seropositive persons

HSV-2, the primary causative agent of genital herpes, establishes latency in sensory ganglia and reactivates causing recurrent lesions and viral shedding. Induction or expansion of CD4(+) and CD8(+) T cell responses are expected to be important for a successful therapeutic vaccine against HSV-2. A candidate vaccine consisting of 32 synthetic 35mer HSV-2 peptides non-covalently complexed with recombinant human Hsc70 protein (named HerpV, formerly AG-707) was tested for safety and immunogenicity in a Phase I study. These peptides are derived from 22 HSV-2 proteins representative of all phases of viral replication. Thirty-five HSV-2 infected participants were randomized and treated in one of four groups: HerpV+QS-21 (saponin adjuvant), HerpV, QS-21, or vehicle. The vaccine was well tolerated and safe. All seven participants with evaluable samples who were administered HerpV with QS-21 demonstrated a statistically significant CD4(+) T cell response to HSV-2 antigens, and the majority of such participants demonstrated a statistically significant CD8(+) T cell response as well. To our knowledge, this is the first candidate vaccine against HSV-2 to demonstrate a broad CD4(+) and CD8(+) T cell response in HSV-2(+) participants, and the first HSP-based vaccine to show immune responses against viral antigens in humans.

Pheophorbide a-Mediated Photodynamic Therapy Triggers HLA Class I-Restricted Antigen Presentation in Human Hepatocellular Carcinoma

The immunomodulatory effects of photodynamic therapy (PDT) have been reported in several photosensitizers. Pheophorbide a (Pa), a chlorophyll derivative, shows antitumor effects on a number of human cancers in a PDT approach (Pa-PDT); however, the potential effect of Pa-PDT on the anticancer immunity has never been studied. In the present work, the underlying action mechanism of Pa-PDT was systemically investigated with a human hepatoma cell line HepG2. We found that Pa-PDT significantly inhibited the growth of HepG2 cells with a half maximal inhibitory concentration/endoplasmic reticulum of 0.35 microM at 24 hours by the induction of apoptosis, as shown by externalization of phosphatidylserine, release of mitochondrial cytochrome c, and activation of the caspases cascade in the treated cells. Interestingly, using two-dimensional polyacrylamide gel electrophoresis analysis, a 57-kDa disulfide-isomerase-like ER resident protein (ERp57) that belongs to the HLA class I-restricted antigen-processing machinery was found to be mediated during the Pa-PDT treatment. This activation of antigen presentation was confirmed by Western blot analysis and immunostaining. Furthermore, a cross-presentation of antigen with HLA class I proteins and 70-kDa heat shock protein was found in Pa-PDT-treated cells, as shown by the confocal microscopic observation and immunoprecipitation assay. Nevertheless, the immunogenicity of HepG2 cells was increased by Pa-PDT treatment that triggered phagocytic capture by human macrophages. Our findings provide the first evidence that Pa-PDT can trigger both apoptosis and cancer immunity in the tumor host.

Antigen cross-presentation: extending recent laboratory findings to therapeutic intervention

The initiation of adaptive immune responses requires antigen presentation to lymphocytes. In particular, dendritic cells (DCs) are equipped with specialized machinery that promote effective display of peptide/major histocompatibility complexes (MHC), rendering them the most potent stimulators of naive T lymphocytes. Antigen cross-presentation to CD8(+) T cells is an important mechanism for the development of specific cytotoxic T lymphocyte (CTL) responses against tumours and viruses that do not infect antigen-presenting cells. Here, we review recent findings concerning antigen cross-presentation to CD8(+) T lymphocytes. Specific subtypes of DCs in the mouse have been defined as being especially endowed for antigen cross-presentation, and a human homologue of these DCs has recently been described. DC vaccination strategies for the prevention and treatment of human diseases have been under investigation in recent years, but have not generally reached satisfying results. We here provide an overview of new findings in antigen cross-presentation research and how they can be used for development of the next generation of human DC vaccines.

Extracellular heat shock protein 90 plays a role in translocating chaperoned antigen from endosome to proteasome for generating antigenic peptide to be cross-presented by dendritic cells

Extracellular heat shock protein can deliver associated antigens into the MHC class I presentation pathway of antigen-presenting cells, a process called cross-presentation, thus inducing antigen-specific CD8(+) T-cell responses; however, the precise mechanism for intracellular antigen translocation and the processing pathway has not been fully elucidated. Here we demonstrate that cross-presentation of extracellular Hsp90-ovalbumin (OVA) protein complexes to specific CD8(+) T cells involves both classical proteasome-transporter-associated antigen processing (TAP)-dependent and TAP-independent-endosomal pathways. Using confocal microscopy, we found that the internalized extracellular Hsp90 and OVA co-localized with cytosolic proteasomes. When anti-Hsp90 mAb was introduced to dendritic cells (DCs), we observed that the co-localization of internalized Hsp90-chaperoned OVA and proteasomes was abolished, resulting in the inhibition of TAP-dependent cross-presentation of OVA. Thus, extracellular Hsp90 may play a pivotal role for the translocation of chaperoned antigens for proteasomal degradation in the cytosol. In contrast, OVA chaperoned by Hsp90 was not presented by MHC class II molecules in vitro or in vivo, although the antigen was exogenously loaded onto DCs. Our data indicate that extracellular Hsp90 might be essential for the translocation of chaperoned antigens from the extracellular milieu into cytosol, resulting in proteasomal degradation for cross-presentation.