Heat shock proteins transfer peptides during antigen processing and CTL priming

Molecular cloning and expression analysis of a heat shock protein (Hsp90) gene from black tiger shrimp (Penaeus monodon)

The techniques of homology cloning and anchored PCR were used to clone the Hsp90 gene from black tiger shrimp. The full length cDNA of black tiger shrimp Hsp90 (btsHsp90) contained a 5' untranslated region (UTR) of 72 bp, an ORF (open reading frame) of 2160 bp encoding a polypeptide of 720 amino acids with an estimated molecular mass of 83-kDa and a 3' UTR of 288 bp. The sequence of the coding region showed 90 and 84% homology with that of the Chiromantes haematocheir and Homo sapiens, respectively. Conserved signature sequences of Hsp90 gene family were found in the btsHsp90 deduced amino acid sequence. The temporal expressions of Hsp90 gene were constitutively in the black tiger shrimp tissues including liver, ovary, muscle, brain stomach, and heart, and their levels were markedly enhanced after 30-min heat treatment at 37 degrees C. In ovarian maturation stages, the expression of btsHsp90 was strongest in the second stage, weaker in the fourth and first stage.

DNA vaccine encoding heat shock protein 60 co-linked to HPV16 E6 and E7 tumor antigens generates more potent immunotherapeutic effects than respective E6 or E7 tumor antigens

OBJECTIVE

Vaccination based on tumor antigen is an attractive strategy for cancer prevention and therapy. Cervical cancer is highly associated with human papillomavirus, especially type 16. We developed DNA vaccines encoding heat shock protein 60 (HSP60) linked to HPV16 E6 or E7 to test if HSP60 chimeric DNA vaccines may generate strong E6 and/or E7-specific immune response and anti-tumor effects in vaccinated mice.

METHODS

In vivo antitumor effects such as preventive, therapeutic, and antibody depletion experiments were performed. In vitro assays such as intracellular cytokine stainings, ELISA for Ab responses, and direct and cross-priming effects, were also performed.

RESULTS

HSP60 chimeric DNA vaccines generated strong E6- or E7-specific immune responses and anti-tumor effects in vaccinated mice via direct and cross-priming effects. HSP60 was also linked with both E6 and E7 antigens and the HSP60/E6/E7 chimeric DNA vaccine generated more potent immunotherapeutic effects on E6- and E7-expressing tumors than HSP60/E6 or HSP60/E7 chimeric DNA vaccine alone.

CONCLUSION

Utilization of both E6 and E7 tumor antigens can advance the therapy of tumors associated with HPV-infections. The DNA vaccine encoding heat shock protein 60 co-linked to HPV16 E6 and E7 tumor antigens can generate more potent immunotherapeutic effects than E6 or E7 tumor antigens alone.

Biological Heterogeneity of the Peptide-binding Motif of the 70-kDa Heat Shock Protein by Surface Plasmon Resonance Analysis

70-kDa heat shock protein family is a molecular chaperone that binds to a variety of client proteins and peptides in the cytoplasm. Several studies have revealed binding motifs between 70-kDa heat shock protein family and cytoplasmic proteins by conventional techniques such as phage display library screening. However, little is known about the binding motif based on kinetic parameters determined by surface plasmon resonance analysis. We investigated the major inducible cytosolic 70-kDa heat shock protein (Hsp70)-binding motif with the human leukocyte antigen B*2702-derived peptide Bw4 (RENLRIALRY) by using a Biacore system based on surface plasmon resonance analysis. The K(D) value of Hsp70-Bw4 interaction was 1.8 x 10(-6) m. Analyses with truncated Bw4 variant peptides showed the binding motif of Hsp70 to be seven residues, LRIALRY. To further study the characteristics of this motif, 126 peptides derived from Bw4, each with single amino acid substitution, were synthesized and analyzed for Hsp70 binding affinity. Interestingly, the Hsp70 binding affinity was abrogated when the residues were substituted for by acidic (Asp and Glu) ones at any position. In contrast, if the substitute residue was aromatic (Trp, Tyr, and Phe) or an Arg residue at any position, Hsp70 binding affinity was maintained. Thus, this study presents a new binding motif between Hsp70 and peptides derived from the natural protein human leukocyte antigen B*2702 and may also elucidate some characteristics of the Hsp70 binding characteristic, enhancing our understanding of Hsp70-binding determinants that may influence diverse cellular and physiological processes.

Human ovarian tumour-derived chaperone-rich cell lysate (CRCL) elicits T cell responses in vitro

Tumour-derived chaperone-rich cell lysate (CRCL), which is made up of numerous heat shock proteins, has been used successfully to generate tumour-specific T cell responses and protective immunity against a wide range of murine tumours. In this study, we have investigated the potency of human ovarian cancer-derived CRCL to activate dendritic cells (DC) and to generate tumour-specific T cells in vitro. CRCL was generated from primary ovarian cancers and SKOV3-A2, a HER2/neu, Wilm's tumour gene 1 (WT1) and human leucocyte antigen (HLA)-A2 positive human ovarian tumour cell line. Peripheral blood mononuclear cells from both HLA-A2(+) healthy donors and HLA-A2(+) ovarian cancer patients were stimulated weekly with autologous DC loaded with ovarian tumour-derived CRCL. After four to six stimulations in vitro, specific cytokine secretion and cytotoxicity were measured. CRCL promoted interleukin (IL)-12 secretion and enhanced the immunostimulatory capacity of DC. T cells from healthy controls and from ovarian cancer patients secreted higher amounts of interferon-gamma following in vitro restimulation with ovarian cancer-derived CRCL than with HER2/neu or WT1 peptide-pulsed DC. We were also able to generate cytotoxic T lymphocyte activity against cancer-specific antigens such as HER2/neu and WT1 from all healthy donors, but from only one of the four ovarian cancer patients with bulky disease. These preliminary results substantiate further the concept that CRCL may prove to be a potent adjuvant for women suffering from ovarian cancer and that this personalized vaccine may be a promising approach for active immunotherapy.

Combined use of dendritic cells enhances specific antileukemia immunity by leukemia cell-derived heat shock protein 70 in a mouse model with minimal residual leukemia cells

We have reported that immunotherapy using leukemia cell-derived heat shock proteins (HSPs) is effective against minimal residual disease (MRD) after syngeneic stem cell transplantation (SCT) in mice. However, leukemia patients after SCT are usually immunocompromised and immunologically tolerant to leukemia cells. We investigated whether the use of dendritic cells (DCs) in combination with HSP70 enhances cytotoxicity against B-cell leukemia cell line A20 in mice after syngeneic SCT. All unimmunized mice died of leukemia early after A20 cell inoculation, whereas mice immunized with HSP70 or HSP70-pulsed DCs survived significantly longer. Although only 60% of the HSP70-immunized mice survived, all mice immunized with HSP70-pulsed DCs survived without MRD. In addition, the cytotoxicities against A20 cells for splenocytes from mice immunized with HSP70-pulsed DCs were significantly higher than those of HSP70-immunized mice, and the cytotoxicities against A20 cells were significantly blocked by anti-CD8 antibody and by major histocompatibility complex class I antibody, but not by anti-CD4 antibody. Moreover, abnormalities were detected in neither the biochemical data nor the histopathologic findings. These findings indicate that the combined use of DCs and leukemia cell-derived HSP70 enhances the antileukemia effect by inducing the specific cytotoxicities of CD8+ cytotoxic T-cells, thereby eradicating MRD effectively and safely, even in an immunocompromised state after syngeneic SCT. This approach may thus be useful for further application of HSP in leukemia patients after autologous SCT.

Serpin A1 and CD91 as host instruments against HIV-1 infection: are extracellular antiviral peptides acting as intracellular messengers?

Serpin A1 (alpha1-antitrypsin, alpha1-proteinase inhibitor) has been shown to be a non-cytolytic antiviral factor present in blood and effective against HIV infection. The best known physiological role of serpin A1 is to inhibit neutrophil elastase, a proteinase which is secreted by neutrophils at sites of infection and inflammation. Decreased HIV-infectivity is associated with decreased density of membrane-associated elastase. The enzyme may facilitate binding of the HIV membrane protein gp120 to host cells, and it specifically cleaves SDF-1, the physiological ligand of the HIV-1 co-receptor CXCR4. It has been suggested that one of the actions of serpin A1 as antiviral agent is to reduce HIV infectivity, and this property could be due to elastase inhibition. However, the most dramatic effect of serpin A1 is inhibition of HIV production. In vitro experiments indicate that the C-terminal peptide of serpin A1, produced during the formation of the complex of serpin with serine proteinases, may be responsible for the inhibition of HIV-1 expression in infected cells. This peptide, an integral part of the serpin-enzyme complex, is internalized by several scavenger receptors. Peptides corresponding to the C-terminal section of serpin A1 inhibit HIV-1 long-terminal-repeat-driven transcription and interact with nuclear proteins, such as alpha1-fetoprotein transcription factor. LDL-receptor-related protein 1 (LRP1/CD91), the best known receptor for serpin-enzyme complexes, is up-regulated in monocytes of HIV-1-infected true non-progressors. CD91 could be one of the major players in host resistance against HIV-1. It has the capacity of internalizing antiviral peptides such as serpin C-terminal fragments and alpha-defensins, and is at the same time the receptor for heat-shock proteins in antigen-presenting cells, in which chaperoned viral peptides could lead to the induction of cytotoxic T-cell responses.

HSP70 gene fused with Hantavirus S segment DNA significantly enhances the DNA vaccine potency against hantaviral nucleocapsid protein in vivo

Heat shock proteins (HSPs) have been shown to act as adjuvants when coadministered with peptide antigens or given as fusion proteins and enhance the vaccination efficiency. To evaluate the enhancement of the potency of Hantaan virus (HTNV) nucleocapsid protein (NP) immunogenicity by heat shock protein 70 (HSP70), we developed a novel chimeric HTNV S-HSP70 DNA vaccine plasmid by genetically linking HSP70 gene to the full-length HTNV S segment DNA (HTNV S DNA). C57BL/6 mice were immunized with this plasmid followed by a subsequent boost with homologous recombinant protein. The levels of HTNV NP-specific antibody and cellular immune response were measured by use of ELISA, fluorescence activated cell sorter (FACS) analysis, cytotoxicity assay, and IFN-gamma ELISPOT assay. We found that HTNV S-HSP70 DNA vaccination significantly increased the levels of HTNV NP-specific antibody, IgG2a/IgG1 ratio, IFN-gamma producing CD8+ T-cell precursor frequencies, and cytotoxic T lymphocyte (CTL) response when compared with immunization with HTNV S DNA alone or HTNV S DNA physically mixed with HSP70 DNA. By contrast, HSP70 DNA or vector DNA immunization could not induce appreciable levels of specific antibodies and CTL response. Thus, we demonstrate for the first time that HSP70-based HTNV S DNA can induce both humoral and cellular immune response specific for HTNV NP and is a promising candidate DNA vaccine for HTNV infection.

Genetics of sarcoidosis: candidate genes and genome scans

Human leukocyte antigen class II allele associations and T-cell receptor beta chain bias in sarcoidosis suggest a specific disease-triggering antigen exposure in a genetically susceptible host. The cause of sarcoidosis has been elusive, but genetics provides one of the few promising avenues to further our understanding. We review the association studies and genome scans used to identify the genes involved in sarcoidosis.

Mouse CD40-transfected cell lines cannot exhibit the binding and RANTES-stimulating activity of exogenous heat shock protein 70

Here we demonstrate the inducible mouse Hsp72 binds markedly to lymphoid neoplastic macrophage-like P388D1 cells. To examine whether mouse CD40 can play a role in signaling exogenously administered HSP70 in a fashion similar to that of human CD40, we established mouse CD40-transfectants of both human 293 cells and murine-pro-B cell line Ba/F3. A small portion of mouse CD40 expressed on 293-derived transfectants was the mature form with a signal-transducible C-terminal domain, whereas a majority of expressed antigen showed the molecular size smaller than we expect. Flow cytometry showed that mouse Hsp72, but neither its deletion variants nor the related Escherichia coli DnaK, bound to the 293-derived transfectants regardless of CD40 expression. CD40 molecules expressed on the transfectants showed the binding of soluble form of CD40L but this binding was not inhibited by excess amount of HSP70. CD40L, but not any HSP70 recombinant proteins, stimulated the production of chemokine RANTES in the transfectants. Furthermore, no RANTES production was induced by HSP70-RCMLA complex in the transfectants, although it binds to 293-derived cells in a CD40-independent manner. No interaction between mouse CD40 and HSP70 recombinant proteins was detected by using the Ba/F3-derived transfectants that express the mature form of mouse CD40. The present results imply that mouse CD40 expressed on the transfectants differs from its human homolog in the binding of exogenously administered HSP70.

Apprêtement des antigénes présentés par les molecules de classe I du CMH

The immune defences of our organism against pathogens and malignant transformation rely to a large extent on surveillance by cytotoxic T lymphocytes. This surveillance in turn depends on the antigen processing system, which provides peptide samples of the cellular protein composition to MHC (major histocompatibility complex) class I molecules displayed on the cell surface. To continuously and almost in real time provide a representative sample of the array of proteins synthesized by the cell, this system exploits some fundamental pathways of the cellular metabolism, with the help of several dedicated players acting exclusively in antigen processing. Thus, a key element in the turnover of cellular proteins, protein degradation by cytosolic proteasome complexes, is exploited as source of peptides, by recruiting a minor fraction of the produced peptides as ligands for MHC class I molecules. These peptides can be further processed and adapted to the precise binding requirements of allelic MHC class I molecules by enzymes in the cytosol and endoplasmic reticulum. The latter compartment is equipped with several dedicated players helping peptide assembly with class I molecules. These include the TAP (transporter associated with antigen processing) membrane transporter pumping peptides into the ER, and tapasin, a chaperone with a structure similar to MHC molecules that tethers class I molecules awaiting peptide loading to the TAP transporter, and mediates optimization of MHC class I ligand by a still somewhat mysterious mechanism. Additional "house-keeping" chaperones that are known to act in concert in ER quality control, assist and control correct folding, oxidation and assembly of MHC class I molecules. While this processing system handles exclusively endogenous cellular proteins in most cells, dendritic cells employ one or several special pathways to shuttle exogenous, internalized proteins into the system, in a process referred to as cross-presentation. Deciphering the cell biological mechanism creating the link between the endosomal and secretory pathways that enables cross-presentation is one of the challenges faced by contemporary research in the field of MHC class I antigen processing.

Initiation of the Immune Response by Extracellular Hsp72: Chaperokine Activity of Hsp72

Heat shock proteins exert their beneficial effects via basically two modes of action depending on their relative location within the host. Intracellular heat shock proteins found within cells serve a cytoprotective role by chaperoning naïve, misfolded and/or denatured proteins in response to stressful stimuli by a process known as the stress response. However, stressful stimuli also induce the release of intracellular heat shock proteins into the extracellular milieu and circulation. The extracellular heat shock protein proteins serve a cytostimulatory role by initiating immune responses designed to fend off microbial infection and destroy neoplastic transformed cells. This review will briefly cover recent advances into elucidating the mechanism(s) by which stress induces the release of heat shock proteins into the circulation, how it initiates immune responses and suggest the possible biological significance of circulating Hsp to the host.

Therapeutic aspects of chaperones/heat-shock proteins in neuro-oncology

Tumors of the CNS frequently have devastating consequences in terms of cognitive and motor function, personality and mortality. Despite decades of work, current therapies have done little to alter the course of these deadly diseases. The discovery that chaperones/heat-shock proteins play an important role in tumor biology and immunology have sparked much interest in utilizing these proteins as targets of therapeutics, or as therapeutics themselves, in the treatments of a variety of cancers. Neuro-oncology has only recently taken notice of these entities, and the purpose of this review is to provide a background, an update and a view to the future for the roles of chaperones/heat-shock proteins in the treatment of brain tumors.

Generation of anti-tumor immunity using mammalian heat shock protein 70 DNA vaccines for cancer immunotherapy

In this study, we explored the protective anti-tumor potency of mouse (self) Hsp70 or Hsp110-based DNA vaccination approach targeting a tumor-associated antigen, human papilloma virus (HPV) type 16 E7 protein. Linkage of E7 to the N-terminus of the mouse Hsp70 not only elicits an E7-specific cytotoxic T cell (CTL) response, but also protects mice against challenge with E7 expressing tumors. CD8+ T-cells are crucial in both priming and effector phases for the induction of tumor immunity, whereas CD4+ T-cells and NK cells do not appear to play a major role. Furthermore, the ATP-binding domain deletion mutant Hsp70(382-641), when fused to E7, was immunologically effective, suggesting that the peptide-binding region, not the ATPase domain of Hsp70, is required for the vaccine activity of the E7-Hsp70 DNA. This study demonstrates that autologous Hsp70 is highly potent in enhancing antigen-specific immune responses. Functional domain mapping and orientation of the E7 and Hsp70 in the fusion gene may have clinical implications for the design and optimization of Hsp70-based DNA vaccines.

Sindbis virus replicon particles encoding calreticulin linked to a tumor antigen generate long-term tumor-specific immunity

Alphavirus vectors have emerged as a promising strategy for the development of cancer vaccines and gene therapy applications. In this study, we used the replication-defective vaccine vector SIN replicon particles from a new packaging cell line (PCL) to develop SIN replicon particles encoding calreticulin (CRT) linked to a model tumor antigen, human papillomavirus type 16 (HPV16) E7 protein. The linkage of CRT to E7 in SIN replicon particles resulted in a significant increase in E7-specific CD8(+) T-cell precursors and a strong antitumor effect against E7-expressing tumors in vaccinated mice. SINrep5-CRT/E7 replicon particles enhanced presentation of E7 through the major histocompatibility complex (MHC) class I pathway by infecting dendritic cells (DCs) directly and pulsing DCs with lysates of cells infected by SINrep5-CRT/E7 replicons. Vaccination of immunocompromised (BALB/c nu/nu) mice with SINrep5-CRT/E7 replicon particles also generated significant reduction of lung tumor nodules, suggesting that antiangiogenesis may contribute to the antitumor effect of SINrep5-CRT/E7 replicon particles. Furthermore, SINrep5-CRT/E7 replicon particles generated long-term in vivo tumor protection effects and antigen-specific memory immunities. We concluded that the CRT strategy used in the context of SIN replicon particles facilitated the generation of a highly effective vaccine for cancer prophylaxis and immunotherapy.

Recombined DNA vaccines encoding calreticulin linked to HPV6bE7 enhance immune response and inhibit angiogenic activity in B16 melanoma mouse model expressing HPV 6bE7 antigen

Calreticulin (CRT) has been reported to have an effect of upregulating MHC class I presentation as well as inhibiting angiogenesis in vitro and in vivo. Combination of dual mechanisms of enhanced immunogenicity of human papillomavirus (HPV) 6bE7 antigen and antiangiogenesis may be introduced in the strategy of vaccines against condyloma acuminatum (CA) resulting from HPV infection. Therefore, we constructed DNA vaccines by employing different lengths of CRT chimerically linked to a model antigen HPV6bE7 and investigated the immunological and antiangiogenic effects of these vaccines in a B16 melanoma model that express HPV6bE7 antigen. Our results showed that vaccination with CRT180/HPV6bE7 or CRT120/HPV6bE7 enhanced the presence of CD8(+) T cells and TCRgammadelta T cells in vivo, increased the specific lysis activity against E7-expressing cells and secretion levels of IL-2 and IFN-gamma by activating T cells in vitro significantly. Moreover, recombined CRT180 or CRT120 with HPV6bE7 vaccines could elicit a more efficient E7-specific immune response than HPV6bE7 alone. The similarity of immunological enhancement of CRT180/HPV6bE7 and CRT120/HPV6bE7 implies that the immunologically active region mainly exist in fragment 1-120 aa. Furthermore, CRT180/HPV6bE7 and CRT180 displayed remarkable superiority over CRT120/HPV6bE7 in vivo angiogenesis assay, suggesting that the antiangiogenic activity of CRT resides in a domain between aa 120 and 180. Vaccination with CRT180/HPV6bE7 generated the best protective effect of delaying tumor formation and reduction of tumor size in tumor growth inhibition experiment among all DNA constructs. Therefore, CRT180/HPV6bE7 vaccine may enhance the immunological response to HPV6bE7 and inhibit angiogenesis. This construct may be useful in preventing HPV-associated dermatosis and may be developed as a promising strategy to control CA.

Molecular chaperones and cancer immunotherapy

As one of the most abundant and evolutionally conserved intracellular proteins, heat shock proteins, also known as stress proteins or molecular chaperones, perform critical functions in maintaining cell homeostasis under physiological as well as stress conditions. Certain chaperones in extracellular milieu are also capable of modulating innate and adaptive immunity due to their ability to chaperone polypeptides and to interact with the host's immune system, particularly professional antigen-presenting cells. The immunomodulating properties of chaperones have been exploited for cancer immunotherapy. Clinical trials using chaperone-based vaccines to treat various malignancies are ongoing.

Immunotherapy for human cancer using heat shock protein-peptide complexes

Heat shock proteins (HSPs) are primordial and abundant molecules expressed in all cells. Publications starting in 1984 have shown that immunization of mice, rats, and frogs with purified preparations of selected HSPs isolated from cancers leads to protective immunity against the cancer used as the source of the HSP. The basis of the tumor-specific immunogenicity of these molecules lies not in the molecules themselves but in the array of peptides, including antigenic peptides chaperoned by them. These experiments and the ideas derived from them form the basis of an approach to immunotherapy for human cancer that began in 1995 and is now in full swing.

A role for the Hsp90 molecular chaperone family in antigen presentation to T lymphocytes via major histocompatibility complex class II molecules

The heat shock protein (HSP) Hsp90 is known to chaperone cytosolic peptides for MHC class I (MHCI)-restricted antigen presentation to T lymphocytes. We now demonstrate a role for Hsp90 activity in presentation of antigens on MHCII. Treatment of mouse antigen-presenting cells (APC) with the pharmacological Hsp90 inhibitor, geldanamycin, inhibited MHCII-mediated presentation of endocytosed and cytosolic proteins as well as synthetic peptides to specific T cells. Ectopic expression of human Hsp90 in APC enhanced MHCII-mediated antigen presentation. Further, pharmacological Hsp90 inhibition reduced, while retroviral Hsp90 overexpression enhanced, the levels of stable compact MHCII heterodimers correlating with the antigen presentation phenotype. Pharmacological inhibition of Hsp90 activity in IFN-gamma-treated APC resulted in severe abrogation of MHCII-restricted presentation of cytosolic antigen, but only partially inhibited exogenous antigen presentation. Our data suggest a major role for Hsp90 activity in MHCII-mediated antigen presentation pathways, and implicate IFN-gamma-inducible Hsp90-independent mechanisms.

HSP70-hom gene single nucleotide (+2763 G/A and +2437 C/T) polymorphisms in sarcoidosis

In the present study, two coding polymorphisms within the heat shock protein 70-hom gene (HSP70-hom) were analysed. One hundred and thirty-eight individuals were studied, including 42 Polish patients with sarcoidosis, 13 of which presented with Löfgren's syndrome (LS), and 94 control subjects. Dimorphisms at positions +2763 (A/G) and +2437 (C/T) of the HSP70-hom gene were typed using amplification refractory mutation system and polymerase chain reaction-restriction fragment length polymorphism technique, respectively. A significant prevalence of the HSP(+2437)-C allele and the HSP(+2437)-CC homozygous genotype was observed in patients with sarcoidosis and in those presenting with LS as compared to controls (P < 0.001 in all comparisons made). A majority of HLA-DRB1*03-positive patients with LS were carrying both HSP(+2437)-C and (+2763)-G alleles, and the concomitant presence of these three genetic factors was more frequent among patients with LS as compared to patients without LS (0.54 vs. 0.17, P < 0.05) and controls (0.54 vs. 0.01, P < 0.001). The association of the HSP(+2437)-C allele with sarcoidosis and LS appeared to be independent of the presence of DRB1*03, although this HLA specificity was associated with LS manifestation. The HSP(+2763)-G allele was independently associated with neither sarcoidosis nor LS. However, this HSP(+2763)-G allele was present with either DRB1*03 or HSP(+2437)-C within the same haplotypes in the patients and this might explain the observed prevalence of DRB1*03, HSP(+2437)-C and (+2763)-G in patients with LS. In conclusion, HSP(+2437)-C allele was found as a factor associating with susceptibility to sarcoidosis and LS.

Chaperone-rich cell lysates, immune activation and tumor vaccination

We have utilized a free-solution-isoelectric focusing technique (FS-IEF) to obtain chaperone-rich cell lysates (CRCL) fractions from clarified tumor homogenates. The FS-IEF technique for enriching multiple chaperones from tumor lysate is relatively easy and rapid, yielding sufficient immunogenic material for clinical use. We have shown that tumor-derived CRCL carry antigenic peptides. Dendritic cells (DCs) uptake CRCL and cross-present the chaperoned peptides to T cells. Tumor-derived CRCL induce protective immune responses against a diverse range of murine tumor types in different genetic backgrounds. When compared to purified heat shock protein 70 (HSP70), single antigenic peptide or unfractionated lysate, CRCL have superior ability to activate/mature DCs and are able to induce potent, long lasting and tumor specific T-cell-mediated immunity. While CRCL vaccines were effective as stand-alone therapies, the enhanced immunogenicity arising from CRCL-pulsed DC as a vaccine indicates that CRCL could be the antigen source of choice for DC-based anti-cancer immunotherapies. The nature of CRCL's enhanced immunogenicity may lie in the broader antigenic peptide repertoire as well as the superior immune activation capacity of CRCL. Exongenous CRCL also supply danger signals in the context of apoptotic tumor cells and enhance the immunogenicity of apoptotic tumor cells, leading to tumor-specific T cell dependent long-term immunity. Moreover, CRCL based vaccines can be effectively combined with chemotherapy to treat cancer. Our findings indicate that CRCL have prominent adjuvant effects and are effective sources of tumor antigens for pulsing DCs. Tumor-derived CRCL are promising anti-cancer vaccines that warrant clinical research and development.

Cancer immunotherapy based on intracellular hyperthermia using magnetite nanoparticles: a novel concept of "heat-controlled necrosis" with heat shock protein expression

Heat shock proteins (HSPs) are highly conserved proteins whose syntheses are induced by a variety of stresses, including heat stress. Since the expression of HSPs, including HSP70, protects cells from heat-induced apoptosis, HSP expression has been considered to be a complicating factor in hyperthermia. On the other hand, recent reports have shown the importance of HSPs, such as HSP70, HSP90 and glucose-regulated protein 96 (gp96), in immune reactions. If HSP expression induced by hyperthermia is involved in tumor immunity, novel cancer immunotherapy based on this novel concept can be developed. In such a strategy, a tumor-specific hyperthermia system, which can heat the local tumor region to the intended temperature without damaging normal tissue, would be highly advantageous. To achieve tumor-specific hyperthermia, we have developed an intracellular hyperthermia system using magnetite nanoparticles. This novel hyperthermia system can induce necrotic cell death via HSP expression, which induces antitumor immunity. In the present article, cancer immunology and immunotherapy based on hyperthermia, and HSP expression are reviewed and discussed.

More efficient induction of HLA-A*0201-restricted and carcinoembryonic antigen (CEA)-specific CTL response by immunization with exosomes prepared from heat-stressed CEA-positive tumor cells

PURPOSE

Tumor-derived exosomes are proposed as a new type of cancer vaccine. Heat shock proteins are potent Th1 adjuvant, and heat stress can induce heat shock protein and MHC-I expression in tumor cells, leading to the increased immunogenicity of tumor cells. To improve the immunogenicity of exosomes as cancer vaccine, we prepared exosomes from heat-stressed carcinoembryonic antigen (CEA)-positive tumor cells (CEA+/HS-Exo) and tested the efficacy of these exosomes in the induction of CEA-specific antitumor immunity.

EXPERIMENTAL DESIGN

First, we identified the composition of CEA+/HS-Exo and observed their effects on human dendritic cell maturation. Then, we evaluated their ability to induce a CEA-specific immune response in vivo in HLA-A2.1/Kb transgenic mice and CEA-specific CTL response in vitro in HLA-A*0201+ healthy donors and HLA-A*0201+CEA+ cancer patients.

RESULTS

CEA+/HS-Exo contained CEA and more heat shock protein 70 and MHC-I and significantly induced dendritic cell maturation. Immunization of HLA-A2.1/Kb transgenic mice with CEA+/HS-Exo was more efficient in priming a CEA-specific CTL, and the CTL showed antitumor effect when adoptively transferred to SW480-bearing nude mice. Moreover, in vitro incubation of lymphocytes from HLA-A*0201+ healthy donors and HLA-A*0201+CEA+ cancer patients with CEA+/HS-Exo-pulsed autologous dendritic cells induces HLA-A*0201-restricted and CEA-specific CTL response.

CONCLUSIONS

Our results show that CEA+/HS-Exo has superior immunogenicity than CEA+/Exo in inducing CEA-specific CTL response and suggest that exosomes derived from heat-stressed tumor cells may be used as efficient vaccine for cancer immunotherapy.

Targeting heat shock proteins for immunotherapy in multiple myeloma: generation of myeloma-specific CTLs using dendritic cells pulsed with tumor-derived gp96

PURPOSE

To develop effective immunotherapies for patients with multiple myeloma, it is important to use novel tumor antigens. Recent studies in solid tumors show that tumor-derived heat shock proteins (Hsp) can be used as immunogen; however, no such study has yet been reported in multiple myeloma.

EXPERIMENTAL DESIGN

We examined whether myeloma-derived Hsp gp96 can be used as a myeloma antigen. Specific CTL lines were obtained after repeatedly stimulating T cells with autologous, HLA-A*0201+ dendritic cells pulsed with gp96 derived from HLA-A*0201+ human myeloma cell line (HMCL) U266 or primary myeloma cells.

RESULTS

These T cells lysed not only gp96-pulsed dendritic cells, U266, and other HLA-A*0201+ HMCLs IM-9 and XG1 but also effectively killed HLA-A*0201+ primary myeloma cells from patients. No killing was observed against unpulsed dendritic cells, dendritic cells pulsed with control gp96, HLA-A*0201- HMCLs, and primary myeloma cells, or HLA-A*0201+ nonmyeloma cells. Cytotoxicity was mainly MHC class I/HLA-A*0201 restricted, suggesting that the CTLs recognized gp96-chaperoned peptides on HLA-A*0201 that were derived from shared myeloma antigens and that myeloma cells naturally present these peptides in the context of their surface MHC molecules. Upon antigen stimulation, these T cells secreted IFN-gamma and tumor necrosis factor-alpha, indicating that they belong to type 1 T-cell subsets.

CONCLUSION

These results show that these T cells are potent CTLs that are able to effectively lyse myeloma cells but not normal blood cells and also suggest that Hsps from allogeneic tumor cells may be used as vaccines to immunize patients.

Releasing signals, secretory pathways, and immune function of endogenous extracellular heat shock protein 72

Heat shock proteins (Hsp) were first characterized as intracellular proteins, which function to limit protein aggregation, facilitate protein refolding, and chaperone proteins. During times of cellular stress, intracellular Hsp levels increase to provide cellular protection. Recently, it has been recognized that Hsp, particularly Hsp72, are also found extracellularly (eHsp72), where they exhibit potent immunomodulatory effects on innate and acquired immunity. Circulating eHsp72 levels also greatly increase during times of stress (i.e., when an organism is exposed to a physical/psychological stressor or suffers from various pathological conditions). It has been proposed that elevated eHsp72 serves a protective role by facilitating immunological responses during times of increased risk of pathogenic challenge and/or tissue damage. This review focuses on the in vivo releasing signals and immunomodulatory function(s) of endogenous eHsp72. In addition, we present data that emphasize the importance of caution when conducting in vitro immunological tests of Hsp72 function.

Medical application of functionalized magnetic nanoparticles

Since magnetic particles have unique features, the development of a variety of medical applications has been possible. The most unique feature of magnetic particles is their reaction to a magnetic force, and this feature has been utilized in applications such as drug targeting and bioseparation including cell sorting. Recently, magnetic nanoparticles have attracted attention because of their potential as contrast agents for magnetic resonance imaging (MRI) and heating mediators for cancer therapy (hyperthermia). Magnetite cationic liposomes (MCLs), one of the groups of cationic magnetic particles, can be used as carriers to introduce magnetite nanoparticles into target cells since their positively charged surface interacts with the negatively charged cell surface; furthermore, they find applications to hyperthermic treatments. Magnetite nanoparticles conjugated with antibodies (antibody-conjugated magnetoliposomes, AMLs) are also applied to hyperthermia and have enabled tumor-specific contrast enhancement in MRI via systemic administration. Since magnetic nanoparticles are attracted to a high magnetic flux density, it is possible to manipulate cells labeled with magnetic nanoparticles using magnets; this feature has been applied in tissue engineering. Magnetic force and MCLs were used to construct multilayered cell structures and a heterotypic layered 3D coculture system. Thus, the applications of these functionalized magnetic nanoparticles with their unique features will further improve medical techniques.

Complexity, contradictions, and conundrums: studying post-proteasomal proteolysis in HLA class I antigen presentation

The vast majority of the peptides produced during protein degradation by the cytosolic proteasome-ubiquitin system are consecutively hydrolyzed to single amino acids by multiple cytosolic peptidases preferring intermediate length or short substrates. The small fraction of peptides surviving the aggressive cytosolic environment can be recruited for presentation by major histocompatibility complex (MHC) class I molecules. However, such peptides may frequently have to be adapted to the strict MHC class I-binding requirements by one or several N-terminal-trimming steps. A recent model proposes that an initial step, in which peptides of 15 or more residues are shortened by cytosolic tripeptidylpeptidase II, is followed by additional trimming by cytosolic or endoplasmic reticulum (ER) aminopeptidases. In humans, at least two ER resident aminopeptidases, ERAP1 and ERAP2, contribute to trimming of human leukocyte antigen class I ligands. These interferon-gamma-regulated metallopeptidases show distinct substrate preferences and may have to act in a concerted fashion to remove some complex or longer N-terminal extensions and to trim the full spectrum of precursor peptides. This task is likely facilitated by the formation of presumably heterodimeric ERAP1-2 complexes. RNA interference experiments suggest that both enzymes are important for normal antigen presentation, but precise determination of the extent and the cellular context of their requirement will be left to future experimentation.

Patterns of heat shock protein (HSP70) expression and Kupffer cell activity following thermal ablation of liver and colorectal liver metastases

The time course and extent of thermal ablative injury differs in liver compared to tumour tissue. This may be influenced by differences in the expression of heat shock proteins (HSP) and the response of Kupffer cells to thermal injury. This study determines the expression and response of HSP70 and Kupffer cells to thermal ablative injury in a Murine model of colorectal liver metastases. Thermal ablation by laser (Nd-YAG wavelength 1064 nm) was induced in liver and colorectal cancer liver metastases in CBA strain mice. Laser energy was applied at 2 W for 50 s and produced incomplete tumour ablation. Established tissue injury was assessed in separate groups of animals at time points ranging from 12 h to 21 days following therapy. HSP70 and Kupffer cell expression at the margins of coagulated tissue was determined by immunohistochemical staining for HSP70 and F4/80 antigens, respectively. HSP70 was faintly expressed in the cytoplasm of all tumour cells, with distinct clusters exhibiting intense cytoplasmic and nuclear HSP70 staining (130+/-19 cells mm-2). Comparatively, HSP70 expression was uncommon in untreated control liver specimens (2+/-2 cells mm-2, p<0.001). Thermal ablation increased expression of HSP70 at coagulated tissue margins. The peak response in tumours occurred at 2 days post-ablation and was significantly greater than the peak response in liver, occurring at 12 h (809+/-80 cells mm-2 vs. 454+/-52 cells mm-2, p<0.001). HSP70 expression remained significantly elevated for 7 days following therapy in tumour tissue, compared to 3 days in liver. Kupffer cell numbers in untreated control tumours were significantly lower than in untreated control livers (285+/-23 cells mm-2 vs. 451+/-30 cells mm-2, p<0.001). Following thermal ablation, there was an initial decrease in Kupffer cell numbers at the margin of coagulation with subsequent persistent increases thereafter. In liver tissue, the peak Kupffer cell response occurred at 5 days post-therapy and was significantly greater than the peak response in tumour tissue 3 days post-thermal ablation (1074+/-34 cells mm-2 vs. 860+/-53 cells mm-2, p=0.007). Thermal ablation produces a greater and more prolonged HSP70 response in colorectal liver metastases than in liver tissue. It also induces persistent increases in Kupffer cell activity in liver and tumour tissue.

Cross-presentation: underlying mechanisms and role in immune surveillance

It was originally thought that a cell's major histocompatibility complex (MHC) class I molecules presented peptides derived exclusively from proteins synthesized by the cell itself. However, in some circumstances, antigens from the extracellular environment can be presented on MHC class I molecules and stimulate CD8(+) T-cell immunity, a process termed cross-presentation. Cross-presentation was originally discovered as an obscure phenomenon in transplantation immunity. However, it is now clear that it is a major mechanism by which the immune system monitors tissues and phagocytes for the presence of foreign antigen. Cross-presentation is the only pathway by which the immune system can detect and respond to viral infections or mutations that exclusively occur in parenchymal cells rather than in bone marrow-derived antigen-presenting cells (APCs). Professional APCs, such as dendritic cells, are the principal cells endowed with the capacity to cross-present antigens. In this process, the APCs acquire proteins from other tissue cells through endocytic mechanisms, especially phagocytosis or macropinocytosis. The internalized antigen can then be processed through at least two different mechanisms. In one pathway, the antigen is transferred from the phagosome into the cytosol, where it is hydrolyzed by proteasomes into oligopeptides that are then transported by the transporter associated with antigen processing to MHC class I molecules in the endoplasmic reticulum or phagosomes. In a second pathway, the antigen is cleaved into peptides by endosomal proteases, particularly cathepsin S, and bound by class I molecules probably in the endocytic compartment itself. Depending on the nature of the antigen, one or both of these pathways can contribute to cross-presentation in vivo. The outcome of cross-presentation can be either tolerance or immunity. Which of these outcomes occurs is thought to depend on whether antigens are acquired by themselves alone, leading to tolerance, or with immunostimulatory signals, leading to immunity. One source of such signals is from dying cells that release immunostimulatory 'danger' signals that promote the generation of immunity to their cellular antigens. In addition to the critical role of cross-presentation in normal immune physiology, this pathway has considerable potential for being exploited for developing subunit vaccines that elicit both CD4(+) and CD8(+) T-cell immunity.

Chaperone proteins and brain tumors: potential targets and possible therapeutics

Chaperone proteins are most notable for the proteo- and cyotoprotective capacities they afford during cellular stress. Under conditions of cellular normalcy, chaperones still play integral roles in the folding of nascent polypeptides into functional entities, in assisting in intracellular/intraorganellar transport, in assembly and maintenance of multi-subunit protein complexes, and in aiding and abetting the degradation of senescent proteins. Tumors frequently have relatively enhanced needs for chaperone number and activity because of the stresses of rapid proliferation, increased metabolism, and overall genetic instability. Thus, it may be possible to take advantage of this reliance that tumor cells have on chaperones by pharmacologic and biologic means. Certain chaperones are abundant in the brain, which implies important roles for them. While it is presumed that the requirements of brain tumors for chaperone proteins are similar to those of any other cell type, tumor or otherwise, very little inquiry has been directed at the possibility of using chaperone proteins as therapeutic targets or even as therapeutic agents against central nervous system malignancies. This review highlights some of the research on the functions of chaperone proteins, on what can be done to modify those functions, and on the physiological responses that tumors and organisms can have to chaperone-targeted or chaperone-based therapies. In particular, this review will also underscore areas of research where brain tumors have been part of the field, although in general those instances are few and far between. This relative dearth of research devoted to chaperone protein targets and therapeutics in brain tumors reveals much untrodden turf to explore for potential treatments of these dreadfully refractive diseases.

Toll-like receptor 4 mediates tolerance in macrophages stimulated with Toxoplasma gondii-derived heat shock protein 70

Peritoneal macrophages (PMs) from toll-like receptor 4 (TLR4)-deficient and wild-type (WT) mice were responsive to recombinant Toxoplasma gondii-derived heat shock protein 70 (rTgHSP70) and natural TgHSP70 (nTgHSP70) in NO release, but those from TLR2-, myeloid differentiation factor 88 (MyD88)-, and interleukin-1R-associated kinase 4 (IRAK4)-deficient mice were not. Polymyxin B did not inhibit PM activation by TgHSP70 and nTgHSP70 from WT and TLR4-deficient mice, while it inhibited PM activation by lipopolysaccharide. Pretreatment of PMs from WT but not from TLR4-deficient mice with rTgHSP70 resulted in suppression of NO release on restimulation with rTgHSP70. Similarly, pretreatment of PMs from WT but not TLR4-deficient mice with nTgHSP70 resulted in suppression of NO release on restimulation with nTgHSP70. Polymyxin B did not inhibit rTgHSP70- and nTgHSP70-induced tolerance of PMs from TLR4-deficient mice. Furthermore, PMs from WT mice increased suppressor of cytokine-signaling-1 (SOCS-1) expression after restimulation with rTgHSP70, while those from TLR4-deficient mice did not. Phosphorylation of JNK and I-kappaBalpha occurred in rTgHSP70-induced tolerance of PMs from TLR4-deficient mice, but not in that from WT mice. These data indicated that TgHSP70 signaling mechanisms were mediated by TLR2, MyD88, and IRAK4, but not by TLR4. On the other hand, signaling of TgHSP70-induced tolerance was mediated by TLR4, and the expression of SOCS-1 suppressed the TLR2 signaling pathway.

MHC Class I–Associated Peptides Identified From Normal Platelets and From Individuals With Idiopathic Thrombocytopenic Purpura

Major histocompatibility complex (MHC) class I molecules bind and display peptide antigens on the cell surface. CD8(+) T lymphocytes recognize peptides in association with class I proteins to initiate a cytotoxic immune response. To understand the specificity of such immune responses and to facilitate the development of therapies for disease, it is important to identify MHC-presented peptides. In this study, platelets, easily obtainable and often associated with immune-mediated disease, were selected to identify MHC class I-associated peptides. MHC-associated peptides presented on platelets of normal individuals and individuals with idiopathic thrombocytopenic purpura (ITP) were characterized. ITP is characterized by the premature immune destruction of platelets. It is associated with the production of antiplatelet autoantibodies, most often targeting platelet membrane GPIIb/IIIa or GPIb/IX. In addition to characterizing five fully and several partially sequenced peptides from platelets, the peptide GPRGA(L/I)S(L/I)(L/I) was identified from four of the five ITP patients. The anchor motif of this peptide correlates with the presence of the HLA-B7 allele. A BLAST search identified this peptide as GPIb (4-12). In conclusion, platelets from normal and ITP individuals can present peptides from general cellular proteins and platelet specific proteins, such as GPIb, to the immune system via MHC class I.

Mechanisms of Focal Heat Destruction of Liver Tumors

BACKGROUND

Focal heat destruction has emerged as an effective treatment strategy in selected patients with malignant liver tumors. Radiofrequency ablation, interstitial laser thermotherapy, and microwave treatment are currently the most widely applied thermal ablative techniques. A major limitation of these therapies is incomplete tumor destruction and overall high recurrences. An understanding of the mechanisms of tissue injury induced by focal hyperthermia is essential to ensure more complete tumor destruction. Here, the currently available scientific literature concerning the underlying mechanisms involved in the destruction of liver tumors by focal hyperthermia is reviewed.

METHODS

Medline was searched from 1960 to 2004 for literature regarding the use of focal hyperthermia for the treatment of liver tumors. All relevant literature was searched for further references.

RESULTS

Experimental evidence suggests that focal hyperthermic injury occurs in two distinct phases. The first phase results in direct heat injury that is determined by the total thermal energy applied, tumor biology, and the tumor microenvironment. Tumors are more susceptible to heat injury than normal cells as the result of specific biological features, reduced heat dissipating ability, and lower interstitial pH. The second phase of hyperthermic injury is indirect tissue damage that produces a progression of tissue injury after the cessation of the initial heat stimulus. This progressive injury may involve a balance of several factors, including apoptosis, microvascular damage, ischemia-reperfusion injury, Kupffer cell activation, altered cytokine expression, and alterations in the immune response. Blood flow modulation and administration of thermosensitizing agents are two methods currently used to increase the extent of direct thermal injury. The processes involved in the progression of thermal injury and therapies that may potentially modulate them remain poorly understood.

CONCLUSION

Focal hyperthermia for the treatment of liver tumors involves complex mechanisms. Evidence suggests that focal hyperthermia produces both direct and indirect tissue injury by differing underlying processes. Methods to enhance the effects of treatment to achieve complete tumor destruction should focus on manipulating these processes.

Heat shock proteins: new keys to the development of cytoprotective therapies

All cells, from bacterial to human, have a common, intricate response to stress that protects them from injury. Heat shock proteins (Hsps), also known as stress proteins and molecular chaperones, play a central role in protecting cellular homeostatic processes from environmental and physiologic insult by preserving the structure of normal proteins and repairing or removing damaged ones. An understanding of the interplay between Hsps and cell stress tolerance will provide new tools for treatment and drug design that maximise preservation or restoration of health. For example, the increased vulnerability of tissues to injury in some conditions, such as ageing, diabetes mellitus and menopause, or with the use of certain drugs,, such as some antihypertensive medications, is associated with an impaired Hsp response. Additionally, diseases that are associated with tissue oxidation, free radical formation, disorders of protein folding, or inflammation, may be improved therapeutically by elevated expression of Hsps. The accumulation of Hsps, whether induced physiologically, pharmacologically, genetically, or by direct administration of the proteins, is known to protect the organism from a great variety of pathological conditions, including myocardial infarction, stroke, sepsis, viral infection, trauma, neurodegenerative diseases, retinal damage, congestive heart failure, arthritis, sunburn, colitis, gastric ulcer, diabetic complications and transplanted organ failure. Conversely, lowering Hsps in cancer tissues can amplify the effectiveness of chemo- or radiotherapy. Treatments and agents that induce Hsps include hyperthermia, heavy metals (zinc and tin), salicylates, dexamethasone, cocaine, nicotine, alcohol, alpha-adrenergic agonists, PPAR-gamma agonists, bimoclomol, geldanamycin, geranylgeranylacetone and cyclopentenone prostanoids. Compounds that suppress Hsps include quercetin (a bioflavinoid), 15-deoxyspergualin (an immunosuppressive agent) and retinoic acid. Researchers who are cognisant of the Hsp-related effects of these and other agents will be able to use them to develop new therapeutic paradigms.

Mechanisms of action of DNA vaccines

The field of DNA vaccines can trace its inception to two papers which demonstrated that administration of plasmid DNA vectors expressing proteins resulted in expression in situ. Thereafter, the possible application of this technique to vaccine development was demonstrated through the induction of antibody responses in mice against a foreign protein, cellular immune responses against a viral antigen and protective efficacy in an infectious disease challenge model. Subsequently, the general utility of DNA vaccines in animal models of infectious and non-infectious disease has been established (for review, see [5]). Initially, most efforts were directed toward demonstration of effectiveness in particular disease models. Recently, however, more attention has been paid to gaining a better understanding of some of the underlying mechanisms of DNA vaccines. This review will focus on this new information and discuss it in the context of how it could benefit the development of more effective DNA vaccines.

Screening of cytokines to enhance vaccine effects of heat shock protein 70-rich tumor cell lysate

Heat shock proteins (HSPs) have been recognized as significant participants in immune reactions. We have previously reported that heat-treated cells expressing HSP70 can mediate potent antitumor immune responses. As successful immunotherapy is dependent on the host immune system, the present study evaluated whether systemic administration of immunocyte stimulatory and growth promoting cytokines could enhance heat-treated cell lysate vaccine (HCLV) immunization to further promote the antitumor immunity. After heating mouse melanoma B16 cells (43 degrees C, 30 min) to elicit increased HSP70 expression, cells were lysed by freeze thawing to prepare HCLV. In approaches using a poorly immunogenic melanoma B16, the effects of various cytokines (IL-1beta, -2, -4, -6 and -12, IFN-beta and -gamma, GM-CSF and TNF-alpha) were assessed in combination with HCLV. Syngenic C57BL/6 mice were immunized subcutaneously with HCLV twice, on days -14 and -7, while cytokines were injected intraperitoneally on day -7. Subcutaneous B16 cell challenge was performed on day 0. IL-12 significantly enhanced the efficacy of HCLV, compared to non-heated cell lysate vaccine (CLV) and non-vaccination. Systemic administration of recombinant IL-12 augmented the efficacy of HCLV, inducing protective immunity against tumor challenge and enhancing cytotoxicity assessed in primed splenocytes against B16 cells in treated mice. These results suggest that IL-12 represents an important modulator of antitumor immune responses induced by HCLV, and may facilitate further efforts to develop novel cancer immunotherapies based on HSP70-mediated vaccination.

HSP70-hom gene polymorphism in allogeneic hematopoietic stem-cell transplant recipients correlates with the development of acute graft-versus-host disease

BACKGROUND

A number of genetic polymorphisms have been shown to be associated with the outcome after allogeneic hematopoietic stem-cell transplantation (HSCT). In the present study, HSP70-hom polymorphism (+2763 G/A) was analyzed in the patients and donors of allogeneic HSCT in relation to transplantation outcome, susceptibility for generation of severe toxic lesions, and acute (a) graft-versus-host disease (GVHD).

METHODS

One hundred thirty-three recipients of allogeneic hematopoietic stem cells and 64 haploidentical and matched unrelated donors were investigated. All these individuals were typed for dimorphism within the HSP70-hom gene (+2763 G/A) with the use of amplification refractory mutation system technique. RESULTS.: Patients with the HSP-AA homozygous genotype presented more frequently with grade II to IV toxic lesions (12 of 14 vs. 61 of 105, P = 0.039) and aGVHD (12 of 16 vs. 56 of 114, P = 0.045). Conversely, DRB1*11 was associated with a lower risk of aGVHD manifestation (10 of 31 vs. 58 of 99, P = 0.009). These contrary associations of HSP-AA and DRB1*11 with the risk of aGVHD were confirmed using logistic regression modeling in multivariable analysis (HSP-AA, odds ratio [OR] = 3.833, P = 0.004; DRB1*11, OR = 0.224, P = 0.048). None of donor HSP genotypes or patient-donor incompatibility within HSP alleles was associated with susceptibility to toxic complications or aGVHD.

CONCLUSIONS

Polymorphism of the HSP70-hom gene is associated with the development of posttransplant complications. Recipient HSP-AA homozygous genotype is a risk factor for aGVHD.

Peptides chaperoned by heat-shock proteins are a necessary and sufficient source of antigen in the cross-priming of CD8+ T cells

The form in which antigens are transferred from cancer cells or infected cells to antigen-presenting cells as a part of the process of priming CD8(+) T cells has been a longstanding unresolved issue. Intact proteins or protein fragments in the form of free peptides or peptides chaperoned by heat-shock protein are possible sources of antigen. We address this here using beta-galactosidase and ovalbumin. Immunization with cell lysates containing intact proteins and heat-shock protein-peptide complexes or with cell lysates depleted of either component demonstrated that protein fragments chaperoned by heat-shock protein and not intact protein were the necessary and sufficient source of antigen transferred to antigen-presenting cells for priming CD8(+) T cell responses.

Potent selection of antigen loss variants of B16 melanoma following inflammatory killing of melanocytes in vivo

We have reported that i.d. injection of plasmids encoding hsp70 and a suicide gene transcriptionally targeted to melanocytes generates specific proinflammatory killing of melanocytes. The resulting CD8+ T cell response eradicates systemically established B16 tumors. Here, we studied the consequences of that CD8+ T cell response on the phenotype of preexisting tumor. In suboptimal protocols, the T cell response selected B16 variants, which grow extremely aggressively, are amelanotic and have lost expression of the tyrosinase and tyrosinase-related protein 2 (TRP-2) antigens. However, expression of other melanoma-associated antigens, such as gp100, was not affected. Antigen loss could be reversed by long-term growth in culture away from immune-selective pressures or within 96 hours by treatment with the demethylating agent 5-azacytidine (5-Aza). When transplanted back into syngeneic animals, variants were very poorly controlled by further vaccination. However, a combination of vaccination with 5-Aza to reactivate antigen expression in tumors in situ generated highly significant improvements in therapy over treatment with vaccine or 5-Aza alone. These data show that inflammatory killing of normal cells activates a potent T cell response targeted against a specific subset of self-antigens but can also lead to the immunoselection of tumor variants. Moreover, our data indicate that emergence of antigen loss variants may often be due to reversible epigenetic mechanisms within the tumor cells. Therefore, combination therapy using vaccination and systemic treatment with 5-Aza or other demethylating agents may have significant therapeutic benefits for antitumor immunotherapy.

The messenger and the message: gp96 (GRP94)-peptide interactions in cellular immunity

Vaccination of mice with tumor-derived stress proteins, such as Hsp70 and gp96 (GRP94), can elicit antitumor immune responses, yielding a marked suppression of tumor growth and metastasis. The molecular basis for this response is proposed to reflect a peptide-binding function for these proteins. In this view, stress proteins bind the antigenic peptide repertoire of their parent cell, and when provided to the immune system, tumor-derived stress protein-peptide complexes are processed by antigen-presenting cells (APCs) to yield the subsequent activation of tumor-directed cytotoxic T lymphocyte activity. This model predicts that stress proteins, whose primary intracellular function concerns the proper folding and assembly of nascent polypeptides, intersect with the cellular pathways responsible for the generation, processing, or assembly (or all) of peptide antigens onto nascent major histocompatability class I molecules. Recent insights into the pathways for peptide generation now allow this hypothesis to be critically examined, which is the subject of this review.

Stress cytokines: pivotal proteins in immune regulatory networks; Opinion

Stress proteins have three immunological regulatory functions: within the cell, on the cell membrane as signalling receptors, and in the extracellular environment as stress cytokines. They can activate the immune system by providing danger signals or they may downregulate immune and inflammatory responses. In addition, they can modulate immune responses by acting as chaperones for antigenic peptides while they themselves are processed and presented to T cells as self-peptides. We predict that the exploitation of the downregulatory properties of stress cytokines will have therapeutic applications in the treatment of human chronic inflammatory diseases, such as rheumatoid arthritis.

The heat-shock protein receptors: some answers and more questions

The existence of heat-shock protein (HSP) receptors on antigen-presenting cells (APCs) was hypothesized in 1994. The first such receptor, CD91 or LRP, was identified and characterized in 2000. The pace of attribution has quickened since and during the last three years alone, six putative HSP receptors have been identified. These include CD40, LOX-1, CD36, Toll-like receptor-2 (TLR-2), TLR-4 and SR-A. The literature on HSP receptors on APCs is critically examined in this review and future directions are imagined.

Effective photoimmunotherapy of murine colon carcinoma induced by the combination of photodynamic therapy and dendritic cells

PURPOSE

The unique mechanism of tumor destruction by photodynamic therapy (PDT), resulting from apoptotic and necrotic killing of tumor cells accompanied by local inflammatory reaction and induction of heat shock proteins (HSPs), prompted us to investigate the antitumor effectiveness of the combination of PDT with administration of immature dendritic cells (DCs).

EXPERIMENTAL DESIGN

Confocal microscopy and Western blotting were used to investigate the influence of PDT on the induction of apoptosis and expression of HSP expression in C-26 cells. Confocal microscopy and flow cytometry studies were used to examine phagocytosis of PDT-treated C-26 cells by DCs. Secretion of interleukin (IL)-12 was measured with ELISA. Cytotoxic activity of lymph node cells was evaluated in a standard (51)Cr-release assay. The antitumor effectiveness of PDT in combination with administration of DCs was investigated in in vivo model.

RESULTS

PDT treatment resulted in the induction of apoptotic and necrotic cell death and expression of HSP27, HSP60, HSP72/73, HSP90, HO-1, and GRP78 in C-26 cells. Immature DCs cocultured with PDT-treated C-26 cells efficiently engulfed killed tumor cells, acquired functional features of maturation, and produced substantial amounts of IL-12. Inoculation of immature DCs into the PDT-treated tumors resulted in effective homing to regional and peripheral lymph nodes and stimulation of cytotoxic activity of T and natural killer cells. The combination treatment with PDT and administration of DCs produced effective antitumor response.

CONCLUSIONS

The feasibility and antitumor effectiveness demonstrated in these studies suggest that treatment protocols involving the administration of immature DCs in combination with PDT may have clinical potential.

Undefined-antigen vaccines

Our knowledge of the immune system and how it interacts with tumor cells continues to grow. With each advance in basic science comes a new opportunity to develop an effective treatment strategy. Many such opportunities have arisen in the past few decades and this chapter has attempted to describe how these new advances have been combined with a variety of undefined cellular antigen preparations in an attempt to develop effective cancer vaccines. None of the strategies described in this chapter have been sufficiently effective to become part of standard therapy. However, the approaches tested have generally been well-tolerated by patients with advanced cancer and the evidence of immunologic activity and examples of impressive clinical activity in a wide variety of malignancies, suggests that these strategies can be the building blocks upon which new advances are added and effective treatments developed.

Potent tumor-specific immunity induced by an in vivo heat shock protein-suicide gene-based tumor vaccine

Tumor cells harbor a repertoire of unique, mutated antigens and shared self-antigens but generally are incapable of provoking an effective immune response, likely because of inadequate antigen presentation by professional antigen-presenting cells. Heat shock proteins (HSPs) play important roles in eliciting innate and adaptive immunity by chaperoning peptides for antigen presentation and providing endogenous danger signaling. Although effective in inducing tumor-specific immunity in mice and in some clinical trials, tumor-derived HSPs have many limitations like vaccines, such as the technical difficulty of ex vivo preparation of adequate quantities of HSPs from the resected tumors of individual patients. Here we have developed an in vivo HSP-suicide gene tumor vaccine by generating a recombinant replication-defective adenovirus (Ad-HT) that coexpresses HSP70 and a herpes simplex virus thymidine kinase suicide gene. The combination of HSP70 overexpression in situ and tumor killing by thymidine kinase/ganciclovir treatment, but neither strategy alone, provoked potent systemic antitumor activities after intratumor injection of Ad-HT. Tumor-specific CD4+ and CD8+ T-cell responses were induced by Ad-HT intratumor injection. CD11c+ dendritic cells (DCs) isolated from mice treated with Ad-HT were able to prime tumor-specific CTLs. Collectively, these results indicate that the combination of tumor killing by activation of a suicide gene to release tumor antigens and in situ HSP70 overexpression to enhance DC antigen presentation overcomes host immune tolerance to tumor antigens, leading to the induction of potent antitumor immunity. Our findings may have broad relevance to the use of the in vivo HSP/suicide gene tumor vaccine in therapy for human solid tumors.

Proteomics shows Hsp70 does not bind peptide sequences indiscriminately in vivo

Heat shock protein 70 (Hsp70) binds peptide and has several functions that include protein folding, protein trafficking, and involvement with immune function. However, endogenous Hsp70-binding peptides had not previously been identified. Therefore, we eluted and identified several hundred endogenously bound peptides from Hsp70 using liquid chromatography ion trap mass spectrophotometry (LC-ITMS). Our work shows that the peptides are capable of binding Hsp70 as previously described. They are generally 8-26 amino acids in length and correspond to specific regions of many proteins. Through computationally assisted analysis of peptides eluted from Hsp70 we determined variable amino acid sequences, including a 5 amino acid core sequence that Hsp70 favorably binds. We also developed a computer algorithm that predicts Hsp70 binding within proteins. This work helps to define what peptides are bound by Hsp70 in vivo and suggests that Hsp70 facilitates peptide selection by aiding a funneling mechanism that is flexible but allows only a limited number of peptides to be processed.

Heat shock protein 70 gene therapy combined with hyperthermia using magnetic nanoparticles

Heat shock proteins (HSPs) are recognized as significant participants in immune reactions. We previously reported that expression of HSP70 in response to hyperthermia, produced using our original magnetite cationic liposomes (MCLs), induces antitumor immunity. In the present study, we examine whether the antitumor immunity induced by hyperthermia is enhanced by hsp70 gene transfer. A human hsp70 gene mediated by cationic liposomes was injected into a B16 melanoma nodule in C57BL/6 mice in situ. At 24 hours after the injection of the hsp70 gene, MCLs were injected into melanoma nodules in C57BL/6 mice, which were subjected to an alternating magnetic field for 30 minutes. The temperature at the tumor reached 43 degrees C and was maintained by controlling the magnetic field intensity. The combined treatment strongly arrested tumor growth over a 30-day period, and complete regression of tumors was observed in 30% (3/10) of mice. Systemic antitumor immunity was induced in the cured mice. This study demonstrates that this novel therapeutic strategy combining the use of hsp70 gene therapy and hyperthermia using MCLs may be applicable to patients with advanced malignancies.

Heat shock proteins in the regulation of apoptosis: new strategies in tumor therapy: a comprehensive review

Heat shock proteins (Hsp) form the most ancient defense system in all living organisms on earth. These proteins act as molecular chaperones by helping in the refolding of misfolded proteins and assisting in their elimination if they become irreversibly damaged. Hsp interact with a number of cellular systems and form efficient cytoprotective mechanisms. However, in some cases, wherein it is better if the cell dies, there is no reason for any further defense. Programmed cell death is a widely conserved general phenomenon helping in many processes involving the reconstruction of multicellular organisms, as well as in the elimination of old or damaged cells. Here, we review some novel elements of the apoptotic process, such as its interrelationship with cellular senescence and necrosis, as well as bacterial apoptosis. We also give a survey of the most important elements of the apoptotic machinery and show the various modes of how Hsp interact with the apoptotic events in detail. We review caspase-independent apoptotic pathways and anoikis as well. Finally, we show the emerging variety of pharmacological interventions inhibiting or, just conversely, inducing Hsp and review the emergence of Hsp as novel therapeutic targets in anticancer protocols.

Cytotoxic T Cell Responses against Mesothelioma by Apoptotic Cell-pulsed Dendritic Cells

Malignant pleural mesothelioma is an uncommon tumor largely confined to the thoracic cavity, which is resistant to conventional therapies, therefore prompting an intensive search for effective treatment alternatives. This study focuses on dendritic cell (DC) vaccination for malignant pleural mesothelioma and evaluates the in vitro efficacy of antigen-loaded DC-based vaccines for the induction of major histocompatibility complex Class I-restricted antimesothelioma cytotoxic T lymphocyte responses. The source of tumor-associated antigens for HLA-A2(+) DCs from healthy donors was apoptotic HLA-A2(-) mesothelioma cells either lacking or expressing heat shock protein 70 according to whether tumor cells were heat shocked or not before ultraviolet-mediated apoptosis. Our results show that both apoptotic preparations were equivalent regarding the responsiveness of DCs to combined treatment with tumor necrosis factor-alpha and poly(inosinic-cytidylic) acid, as determined by similar increased expression of costimulatory molecules and interleukin-12 production. However, only DCs loaded with apoptotic heat shock protein 70-expressing cells were found to be potent in vitro inducers of cytotoxic T lymphocyte activity against HLA-A2(+) mesothelioma cells. Such elicited cytotoxic T lymphocytes also exhibit cytotoxic activity against an HLA-A2(+) melanoma cell line, suggesting recognition of shared antigens. These findings therefore carry the potential of offering an alternative, promising approach for the therapy of patients with malignant pleural mesothelioma.

Heat shock proteins: to present or not, that is the question

The contribution of major histocompatibility complex (MHC) I and II to the adaptive immune response has been well documented. In 1996, Peter Doherty and Rolf Zinkernagel were awarded the Nobel Prize, for their fundamental observations concerning the genetic elements involved in specific antigen (Ag) recognition. These elements encode molecules that present self and non-self peptide fragments to both CD4+ and CD8+ cytolytic T lymphocytes (CTL). The recognition by Srivastava and coworkers that heat shock proteins (HSPs) might also present Ag in chemically induced sarcomas brought about many new questions concerning the central dogma of Ag processing and presentation. HSPs, in particular glucose-regulated peptide 94 (GRP94), HSP70 and to a lesser extent HSP90, bind peptides that are immunogenic in vitro and in vivo. There is mounting evidence that these HSP-peptide complexes provide alternative Ag-specific recognition in many systems. Whether a separate genetic program evolved in addition to MHC that increases the antigenic repertoire of the cell or if this newly observed function of HSP is predominantly a laboratory-based phenomena and/or a normal chaperone function of this family of proteins remains to be answered. Nevertheless, there are clinical therapeutic strategies that involve HSP-derived peptides isolated from various tumors that look extremely promising.