Immunobiology of the Tomatine adjuvant.

Soluble or sub-unit protein vaccines alone are incapable of generating antigen-specific cellular immune responses. This failure can be attributed to the manner in which the immune system processes antigen; endogenous antigens are cycled through the MHC class I pathway to stimulate CD8+ restricted responses and exogenous antigens are processed through the MHC class II pathway to generate humoral immunity. Traditionally sub-unit vaccines have been formulated with adjuvants to enhance immunogenicity, however in the last decade a number of adjuvants have been developed that effectively stimulate the generation of both humoral and cellular immune responses, although the manner in which they exert their effects has not been investigated. Here we describe Tomatine, a glycoalkaloid based adjuvant, capable of stimulating potent antigen-specific humoral and cellular immune responses that contribute to protection against malaria, Francisella tularensis and regression of experimental tumors. Using in vivo models we investigated the manner in which cellular immune responses were generated by Tomatine. We established that Tomatine did not require either lymph node or splenic macrophages to generate cytotoxic T lymphocytes (CTL) and delivered soluble protein into a pathway not dependant on the machinery of the classical MHC class I pathway. We also observed that at the molecular level Tomatine required both CD80 and CD86 costimulation to engender antigen-specific cellular immunity.

The apoptotic and necrotic effects of tomatine adjuvant.

Tomatine adjuvant, consisting of tomatine, n-octyl-beta-d-glucopyranoside (OGP), phosphatidylethanolamine and cholesterol is unique in that when combined with soluble protein antigen it elicits a cytotoxic T lymphocyte (CTL) response in immunized animals. The mechanisms underlying this property are unknown. In an attempt to understand how tomatine activates cellular immunity, we examined its potential to induce apoptosis. Thus in the present study, cell death of EL4 thymoma cells induced by whole adjuvant and the surface-active components in the formulation was examined. Cytotoxicity was monitored using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and lactate dehydrogenase release assays, apoptosis and necrosis were quantified by flow cytometry using Annexin V and propidium iodide staining, and morphology was examined by Hoechst 33342 staining. Flow cytometric analysis demonstrated the appearance of the sub-G1 phase in cells treated with these agents and Annexin V/PI staining showed that all three agents induced both apoptosis and necrosis in EL4 cells in a concentration-dependent manner. Tomatine was effective at much lower concentrations than OGP, suggesting that the majority of the effect of whole adjuvant could be attributed to this component. Microscopic examination of EL4 cells after treatment with these agents revealed morphological features of apoptosis, including chromatin condensation and DNA fragmentation. Pretreatment with zVAD-fmk did not block cell death induced by these agents, showing that tomatine adjuvant-induced EL4 cell apoptosis is caspase-independent.

Cell death induced by vaccine adjuvants containing surfactants.

Many vaccine adjuvants contain surface-active agents, but the immunological roles played by these components have been essentially ignored. The objective of this study was to examine possible apoptotic and necrotic effects of the surface-active agents, Pluronic L121 and Tween 80, which are components of L121-adjuvant (a formulation we synthesized with the aim of representing several commercially produced adjuvants), on EL4 lymphoma cells. Cell viability and cytolytic effects were analyzed using the MTT and LDH release assays, and the distribution of cells in different stages of the cell cycle after treatment with these agents was analyzed by propidium iodide (PI) staining and flow cytometry. L121-adjuvant was shown to induce cell cycle arrest and inhibit cell proliferation. Treatment of EL4 cells with surface-active agents resulted in a concentration-dependent increase in the apoptotic/necrotic cell populations. Fluorescence microscopy using Hoechst 33342 staining demonstrated chromosome condensation and DNA fragmentation in cells treated with surfactants or adjuvant. The apoptotic and necrotic effects of vaccine adjuvant containing surface-active agents were confirmed by Annexin V/propidium iodide staining and flow cytometric analysis. Pretreatment of EL4 cells with zVAD-fmk, a broad range caspase inhibitor, partially prevented apoptosis induced by Pluronic L121, but did not prevent the cell death induced by Tween 80 or L121-adjuvant. These findings suggested that Tween 80 and L121-adjuvant induced apoptosis in EL4 cells via a "non-classical" caspase-independent pathway. Results presented in this study suggest mechanisms of elicitation of CD8(+), class I-restricted CTL response by soluble antigens mediated by the vaccine adjuvant containing surface-active agents.

Isolation of human leukocyte antigen (HLA)-associated peptide(s) in the absence of HLA-restricted specific cytolytic T lymphocytes.

BACKGROUND/METHODS: In this study, immunobead purification, dot-blot, immunocytochemical staining, and SDS-PAGE techniques in combination with high-performance liquid chromatography were used to isolate human leukocyte antigen (HLA) class I antigens and associated peptides from a bladder tumour cell line (Fen) before and after gene transfection. RESULTS: The results showed that: (1) Transfection of the class I negative Fen cell line with normal beta-microglobulin (beta(2)-m) gene resulted in the restoration of missing class I antigens. (2) The intact class I antigens could be isolated from lysate of the beta(2)-m gene transfected cells using Sepharose CNBr-W6/32 beads. (3) Dissociation of class I antigens from beads and analysis by the SDS-PAGE showed the presence of both free heavy and light chains of class I antigens. (4) More than 22 class I-associated peptides with a molecular weight of 700-3,000 daltons could be isolated from W6/32-loaded beads but only from lysate of HLA-positive Fen cell line. The data also showed that 1 x 10(6) of positive Fen cells contained about 200 microg total protein of which about 0.10 microg was class I and about 2 ng was class I-associated peptides. CONCLUSIONS: These findings demonstrated that the gene transfection approach could be used to restore missing class I antigens on an otherwise class I negative bladder tumour cell line. The results also showed the feasibility of using above techniques for isolation of HLA-associated peptides. These approaches may provide a realistic possibility for identification of putative tumour-specific peptide(s) from tumour specimens with the long-term aim to use such peptide(s) for immunotherapy in cancer patients.

Immunization with a DNA vaccine expressing a truncated form of varicella zoster virus glycoprotein E.

The gE glycoprotein of varicella zoster virus (VZV) is involved with cell entry and it is the most abundant glycoprotein produced in VZV-infected cells. It is also the first glycoprotein to be recognized by the immune system and induces neutralizing antibodies and cellular immunity. We have shown previously that immunization with a DNA vaccine encoding full length gE induces high antibody titres in BALB/c mice. In this study, we engineered a truncated form of gE to facilitate secretion of the glycoprotein, which is thought to increase the quantity of antigen available for B cells to mount an immune response. This hypothesis was tested by using inverse PCR mutagenesis (IPCRM) to engineer a mutated form of gE that was secreted from the cell. This construct was then evaluated as a potential DNA vaccine. Following immunization studies, the magnitude of the immune response induced with the mutant form of gE was found to be similar to that induced by membrane bound protein. This finding suggests that, in the case of VZV, a DNA vaccine expressing a secreted protein has no advantage over one expressing a membrane bound protein. However, mice immunized with the truncated form of gE (gED) displayed responses favouring IgG1 (Th2) in comparison with mice immunized with the full length gE construct, which generated an IgG2a (Th1) response. This observation indicates that immunization with a truncated form of a gene may induce immune modulation, a phenomenon that should be taken into account for the design of vaccines.

Helicobacter pylori vaccine strategies--triggering a gut reaction.

Helicobacter pylori causes peptic ulcer disease and some forms of gastric cancer; it is one of the most common chronic bacterial infections of humans. Although several prototype protein-based vaccines have shown promising results, they have not cleared infection and/or prevented reinfection. Nucleic acid vaccination offers a useful alternative to protein immunization, especially now that two complete H. pylori genome sequences are available, and facilitates the selection of antigenic targets.

Localized monocyte chemotactic protein-1 production correlates with T cell infiltration of synovium in patients with psoriatic arthritis.

OBJECTIVE: To examine normal and psoriatic skin and synovial tissue from patients with psoriatic arthritis (PsA) for evidence of monocyte chemotactic protein-1 (MCP-1) mediated T cell chemotaxis. METHODS: Peripheral blood (PB), synovial fluid (SF), normal and psoriatic skin, and synovial biopsies were obtained from patients with PsA (n = 19) and compared to samples from normal (n = 5) and disease (n = 5) controls (NC, DC). Immune cell populations in PB and SF samples were assessed by immunofluorescent labeling and flow cytometry, levels of soluble MCP-1 were determined by quantitative ELISA, and immunohistochemistry was used to detect T cell subsets and macrophages and MCP-1 protein in frozen skin and synovial tissue sections. RESULTS: CD8+ but not CD4+ T cells were elevated in SF compared to PB, and the majority of these cells expressed CD45RO. Plasma MCP-1 levels in PsA were elevated relative to NC. MCP-1 levels were significantly higher than paired plasma samples in patients with recent onset (< 6 mo) synovitis (n = 10). A positive correlation was observed between synovial T cell numbers and MCP-1 levels in SF. MCP-1 protein was present in all tissues examined, but most intense expression was observed in synovium. CONCLUSION: Elevated concentrations of MCP-1 concomitant with memory T cell infiltration in PsA SF suggests that MCP-1 mediated chemotaxis is involved in the recruitment of T lymphocytes into the synovial compartment of patients with PsA.

Immunization with a DNA expression vector encoding the varicella zoster virus glycoprotein E (gE) gene via intramuscular and subcutaneous routes.

In this study we constructed a plasmid containing the gene encoding varicella-zoster virus transmembrane glycoprotein gE (VZV gE) and evaluated its utility for DNA immunization in mice. Our initial work demonstrates that intramuscular and subcutaneous injection of VZV gE DNA, without the use of costimulatory molecules or other adjuvant materials, results in the generation of antigen-specific antibodies of primarily the IgG2a subclass, indicating that this vaccine can stimulate Th1 type immunity. This is the first report of a prototype DNA vaccine for varicella-zoster virus.

Delivery systems for molecular vaccination.

Vaccination is one of the medical success stories of the 20th century, however, there are many diseases for which no prophylactic regimes are available. A major hindrance that has prevented the development of effective mass immunization programs is the inability to induce an appropriate, protective, immune response. For example, for vaccines against intracellular pathogens there is a requirement for cell-mediated immunity as characterized by cytolytic T-lymphocyte activity. However, such a response can be extremely difficult to elicit, especially those employing recombinant, soluble protein subunits. This deficiency is due to the inability of these antigens to access the machinery of the appropriate antigen-processing pathway. Following an improved understanding of the mechanisms underlying such processing, as well as the realization that delivery systems can affect, quantitatively and qualitatively, the resulting immune response, the last decade has witnessed an intense research effort in this field. In this article we will review the major developments in the area of antigen delivery as related to vaccination.

Anti-tumour activity against B16-F10 melanoma with a GM-CSF secreting allogeneic tumour cell vaccine.

Genetic modification of tumour cells with the GM-CSF encoding gene renders these cells more potent, as autologous tumour cell vaccine, than their wild-type counterparts. However, autologous vaccines are impractical for wide-scale clinical use and we have therefore investigated the efficacy of the GM-CSF genetic modification approach with an allogeneic whole cell tumour vaccine. In this report, we show that the allogeneic K1735-M2 (H-2k) melanoma cell vaccine induces a specific protective anti-tumour response against the syngeneic B16-F10 (H-2b) melanoma tumour in C57BL/6J mice. In vitro T cell work demonstrated that vaccination of animals with the allogeneic cell vaccine generated cytotoxic T cells specific for the autologous tumour. In vivo T cell subset depletion experiments also illustrated that this anti-tumour effect was mediated by both CD4+ve and CD8+ve T cells, suggesting that the allogeneic vaccine may operate through the 'cross-priming' phenomenon whereby tumour antigens are processed and presented to T cells by the host's own antigen presenting cells (APC). Thus, we transduced K1735-M2 cells with a GM-CSF expressing retroviral vector and showed anti-tumour activity of the GM-CSF secreting K1735-M2 cells as a therapeutic vaccine against the syngeneic B16-F10 tumour. Our data imply that GM-CSF genetically modified allogeneic whole cell tumour vaccines could be successful in the clinic. In addition, more potent combination gene therapy strategies could be tested using this therapeutic allogeneic vaccine model.

Generation of antigen specific CD8+ cytotoxic T cells following immunization with soluble protein formulated with novel glycoside adjuvants.

Presentation of peptide on MHC class I molecules is essential to elicit cytolytic T cell (CTL) activity. Such peptides are a result of the cytosolic, or class I, antigen processing pathway. Due to the segregation of the class I and the exogenous processing pathway, soluble protein cannot enter the class I pathway and is thus incapable of inducing CTL. However careful formulation with adjuvants can overcome this obstacle. In this study we evaluated the capacity of two novel amphiphilic adjuvants, better termed delivery vehicles, to elicit CTL activity in a C57Bl/6 murine model with ovalbumin (OVA) as an antigen. Incomplete Freund's adjuvant and aluminium hydroxide (Alhydrogel) were used as reference adjuvants. In addition the oil-in-water emulsion Provax was used throughout as a positive control adjuvant. Both amphiphile preparations were capable of eliciting potent CTL activity after administration of one immunizing dose of ovalbumin. CTL were CD8+ restricted as assessed by in vitro depletion of CD8+ and CD4+ T cells. CTL activity was also MHC-restricted as well as specific for the H-2Kb OVA motif SIINFEKL.

Comparison of four strategies for tumour vaccination in the B16-F10 melanoma model.

We have compared four cell-based tumour vaccine strategies in prevention experiments using the B16-F10 melanoma model. Two of these are thought to favour the direct antigen presentation pathway (B16-F10 expressing B7.1 and hybrids made between B16-F10 cells and macrophages) and the other two strategies are thought to act by an indirect pathway of presentation (allogeneic tumour cells and autologous tumour cells combined with a powerful adjuvant (Provax-IDEC Pharmaceuticals)). Only the two latter vaccines promoted antitumour activity, whereas the vaccines consisting of B7.1-expressing tumour cells or the hybrid vaccine failed to provide any antitumour activity. Recently human trials have commenced using transfection of the B7.1 molecule, as well as employing the hybrid technology to make tumour-B cell hybrids or tumour and dendritic cell hybrids. Our results suggest that these approaches could be disappointing in the clinics if not optimised.

Desensitization of the inflammatory response in humans: changes in response to cardiopulmonary bypass.

Although circulating levels of interleukin 8 (IL-8), a potent pro-inflammatory chemokine, and many other inflammatory mediators increase in response to cardiopulmonary bypass, only a small proportion of patients develop a clinically significant systemic inflammatory response. The natural mechanisms that control the inflammatory response are poorly understood. To investigate the role of IL-8 in a human inflammatory model, 15 adult patients undergoing cardiopulmonary bypass for elective coronary artery bypass grafting were studied. Following reperfusion, plasma IL-8 levels increased significantly from 58 pg/mL (pre-bypass) and 66 pg/mL (after 20 min of bypass) to 98 pg/mL (p = .02 and .04, respectively), but this was accompanied by a concomitant threefold decrease in the IL-8 binding affinity of circulating neutrophils (Dissociation constant (KL) post-reperfusion/KL pre-bypass = 3.2; KL post-reperfusion/KL after 20 min of bypass = 2.8). IL-8-triggered release of myeloperoxidase and elastase by peripheral blood neutrophils ex vivo was also down-regulated following reperfusion. There were no significant changes in beta 2 integrin expression or inositol polyphosphate metabolism of peripheral blood neutrophils. These changes in receptor affinity and neutrophil responsiveness to IL-8 may represent an important in vivo regulatory mechanism which serves to prevent excessive tissue injury from inflammatory triggers.

The integrin-triggered rescue of T lymphocyte apoptosis is blocked in HIV-1-infected individuals.

HIV infection is associated with a disease status-dependent impairment of Ag-specific T cell responses, resulting in anergy or unchecked apoptotic cell death. beta1 integrins play an important role in the induction of T lymphocyte responses to antigenic challenge by providing a T cell costimulatory signal, and have been shown to rescue various cell types from undergoing apoptosis. We examined the integrin-triggered cell survival signal and associated pathways in CD3+ T cells derived from 69 HIV-1-infected individuals in comparison with healthy controls. We found beta1 integrin-mediated costimulation of TCR-induced T cell proliferation and protection from aberrant cell death to be absent in the majority of patients with AIDS, but intact in asymptomatic, infected individuals. The lack of integrin-mediated rescue may be partly due to an early impairment of TCR/integrin-costimulated secretion of IFN-gamma, a type 1 lymphokine that protects against TCR-induced apoptosis of T cells from HIV-seropositive donors, but not loss of integrin expression. The mechanism of integrin hyporesponsiveness appeared to correlate with a failure of the integrin-generated signal to induce pp125FAK mRNA and protein expression. Protein kinase C activation in CD3+ T cells following integrin stimulation was also impaired in HIV-infected individuals, mostly among the symptomatic/AIDS patients. Protein kinase C inactivation in T cells was shown to have a destabilizing effect in vitro on pp125FAK mRNA that contains an AUUUA motif in the 3'-untranslated region, a consensus sequence for the AU-rich elements responsible for mRNA destabilization. These aberrant changes in pp125FAK expression may have direct significance to the overall immunopathogenesis during infection with HIV-1.

Comparison of IL-2- and IL-4-transfected B16-F10 cells with a novel oil-microemulsion adjuvant for B16-F10 whole cell tumour vaccine.

The use of whole cell tumour vaccines in the treatment of malignant melanoma has given mixed results. Cytokine-transfected tumour cells as vaccine have shown efficacy in animal models but need to be compared with other means of enhancing a systemic anti-tumour immune response. A new generation of immunological adjuvants claimed to be more effective than the conventional adjuvants is now available for assessment. We have investigated the action of an oil-microemulsion adjuvant formulation (IDEC antigen formulation (IDEC-AF)) in the B16-F10 murine melanoma model. After standardisation of the whole cell tumour vaccination protocol we showed that mice vaccinated with whole irradiated cells combined with IDEC-AF produced a significant inhibition of tumour growth, following a challenge with live tumour cells, when compared with mice vaccinated with whole cell vaccine alone. IDEC-AF was superior to two conventional adjuvants, namely alum and incomplete Freund's adjuvant and a more reliable response was achieved with the oil-microemulsion adjuvant compared with IL-2-transfected cells. In addition, the adjuvant was comparable in efficacy to IL-4-transfected B16-F10 cells. Given the practical difficulty in using cytokine-transfected tumour cells and the limited therapeutic range of some cytokines, a cheap and easy to deliver adjuvant formulation proved equally or more effective than some of the currently clinically used transfected cytokines.

Adhesion co-receptor expression and intracellular signalling in HIV disease: implications for immunotherapy.

OBJECTIVES: To investigate, in lymphocytes from HIV-1-infected individuals, the phenotypic expression of various adhesion co- or counter-receptors [lymphocyte function-associated antigen (LFA)-3, LFA-1 and intercellular adhesion molecule (ICAM)-1] involved in providing the co-stimulatory signal through the phospholipase C-gamma pathway in relation to inositol polyphosphate metabolism. DESIGN AND METHODS: Cell adhesion molecule profiles of peripheral blood lymphocytes (PBL) from 39 HIV-1-infected individuals at various stages of infection and 20 healthy laboratory controls were studied using flow cytometry. These were studied in 14 patients with late-stage disease in conjunction with their inositol polyphosphate metabolic profiles measured by high performance liquid chromatography. Levels of HIV-1 present in cell lysates were concurrently measured by a p24 antigen capture assay. In addition, the effects of a specific anti-ICAM-1 antisense oligonucleotide on the intracellular phosphatase activities of lymphocytes from a separate group of eight HIV-1-infected individuals were examined. RESULTS: The expression of LFA-1, a beta 2 integrin, was upregulated among patient PBL in parallel with disease progression, whereas that of LFA-3 (CD58) was found to be significantly reduced among the CD4+ lymphocyte subset in all stages of infection. The 5-phosphatase activity, which we previously observed to be defective in HIV disease, was found to correlate linearly with the expression of both LFA-1 and its ligand, ICAM-1. Treatment of patient lymphocytes with an antisense oligonucleotide, which reduced the cell surface expression of ICAM-1 by blocking the translation of its mRNA, resulted in further reduction of intracellular phosphatase activities. CONCLUSIONS: Our results suggest a pivotal role for adhesion co- and counter-receptors in influencing lymphocyte signalling and hence cellular response to recall antigens in HIV-1-infected individuals.

Induction of antigen-specific class I-restricted cytotoxic T cells by soluble proteins in vivo.

Cytotoxic T lymphocytes (CTL) are induced specifically against viral and tumor antigens presented by major histocompatibility complex class I molecules on the surface of infected or transformed cells. Intracellular synthesized antigens are processed and associated with class I antigens within cells before presentation on the cell surface. Because of this special requirement for CTL induction, exogenous soluble antigens do not, in general, induce specific CTL responses. To overcome this problem, various laboratories have resorted to the use of vaccinia virus and other replicating expression vectors for intracellular antigen delivery leading to the stimulation of humoral and cell-mediated immunity to specific proteins. However, for human use it is safer to use purified and defined antigens for inducing immune responses. Using soluble ovalbumin and human immunodeficiency virus glycoprotein gp120, we have explored the possibility of using an antigen formulation consisting of squalane and Tween 80 to elicit antigen-specific CTL responses in mice. We have demonstrated that this antigen formulation is a potent inducer of CD8+, class I-restricted, antigen-specific CTLs. The CTL priming induced by soluble antigen in squalane/Tween 80 resembles the reported response to the vaccinia recombinant containing human immunodeficiency virus envelope protein and by splenocytes cytoplasmically loaded with soluble ovalbumin. The ramifications of these findings for vaccine development are discussed.

Murine monoclonal anti-idiotope antibody breaks unresponsiveness and induces a specific antibody response to human melanoma-associated proteoglycan antigen in cynomolgus monkeys.

The mouse monoclonal antibody MEM136 (mAb1) is directed against an epitope on human melanoma-associated proteoglycan antigen (MPG). This epitope is also present on various normal human and subhuman tissues. A monoclonal murine anti-idiotope (anti-Id) antibody (mAb2), designated I-Mel-2, was generated against MEM136 and used as a surrogate antigen for the MPG molecule. I-Mel-2 was tested in cynomolgus monkeys (Macaca fascicularis) for its ability to induce anti-MPG humoral responses. All monkeys immunized with Ab2 developed specific anti-anti-idiotype (Ab3) responses that were capable of inhibiting binding of Ab2 to Ab1. Furthermore, I-Mel-2 immune monkey serum contained anti-MPG antibodies (Ab1') that bound to MPG-positive but not to MPG-negative melanoma cell lines. Monkeys immunized with Colo38 melanoma cells (membrane-bound MPG antigen) did not contain anti-MPG antibodies that inhibited the binding of two distinct anti-MPG mAb 125I-labeled MEM136 or 125I-labeled 225.28 to Colo38 cells. The induction of anti-MPG responses in monkeys did not cause any apparent side effects in animals, despite the fact that the MPG antigen is expressed by many normal tissues. The affinity-purified, I-Mel-2 idiotype-specific, Ab3 immunoprecipitated MPG antigen from melanoma cells. Furthermore, the I-Mel-2-induced Ab3 inhibited melanoma cell invasion in an in vitro assay, implying that these antibodies have biological significance.

Synthetic peptides from a conserved region of gp120 induce broadly reactive anti-HIV responses.

In our efforts to identify products that might be used for active immunotherapy in human immunodeficiency virus (HIV) infection, we have studied synthetic peptides derived from the CD4 attachment site of gp120. Two peptides have emerged with particularly interesting properties. The first (B138) is linear and spans the envelope residues 421-438; the second (1005/45) encompasses amino acids 418-445 and is cyclized by way of a disulphide bond joining its terminal cysteines. Both species have been shown to inhibit syncytial formation in a conventional bioassay, B138 being the most efficient. Both peptides elicit high titres of anti-peptide antibodies in immunized mice, rabbits and goats, with titres exceeding 1:10(5) in many cases. A substantial portion of this response is directed against gp120 as determined by enzyme-linked immunosorbent assay (ELISA). Analysis by flow cytometry has demonstrated that the antisera are broadly reactive with multiple diverse strains of HIV. The anti-gp120 activity of the anti-peptide antiserum was further confirmed by radioimmuno-precipitation (RIP) assays. Furthermore, RIP analysis and inhibition experiments in a GD4-gp120 binding assay have revealed that anti-peptide sera contain antibodies directed against the CD4 attachment site on gp120 and interfere with this receptor-ligand interaction.