Debbie Drane

Immune responses to ISCOM® formulations in animal and primate models

ISCOMs are typically 40 nm cage-like structures comprising antigen, saponin, cholesterol and phospholipid. ISCOMs have been shown to induce antibody responses and activate T helper cells and cytolytic T lymphocytes in a number of animal species, including non-human primates. Recent clinical studies have demonstrated that ISCOMs are also able to induce antibody and cellular immune responses in humans. This review describes the current understanding of the ability of ISCOMs to induce immune responses and the mechanisms underlying this property. Recent progress in the characterisation and manufacture of ISCOMs will also be discussed.

Characterization of Hepatitis C Virus Core-Specific Immune Responses Primed in Rhesus Macaques by a Nonclassical ISCOM Vaccine

Current therapies for the treatment of hepatitis C virus (HCV) infection are only effective in a restricted number of patients. Cellular immune responses, particularly those mediated by CD8+ CTLs, are thought to play a role in the control of infection and the response to antiviral therapies. Because the Core protein is the most conserved HCV protein among genotypes, we evaluated the ability of a Core prototype vaccine to prime cellular immune responses in rhesus macaques. Since there are serious concerns about using a genetic vaccine encoding for Core, this vaccine was a nonclassical ISCOM formulation in which the Core protein was adsorbed onto (not entrapped within) the ISCOMATRIX, resulting in ∼1-μm particulates (as opposed to 40 nm for classical ISCOM formulations). We report that this Core-ISCOM prototype vaccine primed strong CD4+ and CD8+ T cell responses. Using intracellular staining for cytokines, we show that in immunized animals 0.30–0.71 and 0.32–2.21% of the circulating CD8+ and CD4+ T cells, respectively, were specific for naturally processed HCV Core peptides. Furthermore, this vaccine elicited a Th0-type response and induced a high titer of Abs against Core and long-lived cellular immune responses. Finally, we provide evidence that Core-ISCOM could serve as an adjuvant for the HCV envelope protein E1E2. Thus, these data provide evidence that Core-ISCOM is effective at inducing cellular and humoral immune responses in nonhuman primates.

NY-ESO-1 Protein Formulated in ISCOMATRIX Adjuvant Is a Potent Anticancer Vaccine Inducing Both Humoral and CD8+ T-Cell-Mediated Immunity and Protection against NY-ESO-1+ Tumors

NY-ESO-1 is a 180 amino-acid human tumor antigen expressed by many different tumor types and belongs to the family of “cancer-testis” antigens. In humans, NY-ESO-1 is one of the most immunogenic tumor antigens and NY-ESO-1 peptides have been shown to induce NY-ESO-1-specific CD8+ CTLs capable of altering the natural course of NY-ESO-1-expressing tumors in cancer patients. Here we describe the preclinical immunogenicity and efficacy of NY-ESO-1 protein formulated with the ISCOMATRIX adjuvant (NY-ESO-1 vaccine). In vitro, the NY-ESO-1 vaccine was readily taken up by human monocyte-derived dendritic cells, and on maturation, these human monocyte-derived dendritic cells efficiently cross-presented HLA-A2-restricted epitopes to NY-ESO-1-specific CD8+ T cells. In addition, epitopes of NY-ESO-1 protein were also presented on MHC class II molecules to NY-ESO-1-specific CD4+ T cells. The NY-ESO-1 vaccine induced strong NY-ESO-1-specific IFN-γ and IgG2a responses in C57BL/6 mice. Furthermore, the NY-ESO-1 vaccine induced NY-ESO-1-specific CD8+ CTLs in HLA-A2 transgenic mice that were capable of lysing human HLA-A2+ NY-ESO-1+ tumor cells. Finally, C57BL/6 mice, immunized with the NY-ESO-1 vaccine, were protected against challenge with a B16 melanoma cell line expressing NY-ESO-1. These data illustrate that the NY-ESO-1 vaccine represents a potent therapeutic anticancer vaccine.

Intranasal vaccination with ISCOMATRIX adjuvanted influenza vaccine.

Mucosal delivery of inactivated vaccines that are able to elicit protective immune responses against respiratory diseases has been a long time goal of vaccinologists. Such vaccines would enable a more appropriate means of vaccination against respiratory diseases than those currently delivered by a parenteral route. The intranasal delivery of inactivated influenza vaccine plus the ISCOMATRIX (IMX) adjuvant, simply mixed together, was able to induce serum haemagglutination inhibition (HAI) titres in mice far superior to those obtained with unadjuvanted vaccine delivered subcutaneously. Furthermore, the IMX adjuvanted vaccine delivered intranasally induced mucosal IgA responses in the lung, nasal passages and large intestine, together with high levels of serum IgA. Intranasal delivery of IMX adjuvanted influenza vaccine in sheep gave antibody responses in both serum and nasal secretions that surpassed the levels obtained with unadjuvanted vaccine administered subcutaneously. These observations suggest that it may be possible to induce effective immunity to influenza in humans by intranasal vaccination with an IMX adjuvanted inactivated vaccine.

ISCOMATRIX™ adjuvant for prophylactic and therapeutic vaccines

The ISCOMATRIX™ adjuvant has antigen-delivery and -presentation properties, as well as immunomodulatory capabilities that combine to provide enhanced and accelerated immune responses. The responses are broad, including a range of subclasses of antibodies as well as both CD4+ and CD8+ T cells. A range of ISCOMATRIX vaccines (ISCOMATRIX adjuvant combined with antigen) have been evaluated in clinical trials. The results of these completed and ongoing studies indicate that the ISCOMATRIX adjuvant is safe and generally well tolerated and increases the vaccine immune responses.

Priming of CD4+ and CD8+ T cell responses using a HCV core ISCOMATRIX vaccine: a phase I study in healthy volunteers.

The disease burden and public health impact of chronic HCV infection continues to be a major problem globally. Current treatment for chronic HCV infection is not effective in all patients and is frequently associated with unacceptable side effects. Clearly a need exists for improved treatments and one such strategy is the use of therapeutic vaccines. Although still not completely understood, emerging data indicate that the generation of CD4+ and CD8+ T cells are important for the clearance of HCV. We have developed a prototype vaccine with the HCV Core protein and ISCOMATRIX™ adjuvant (HCV Core ISCOMATRIX™ vaccine). ISCOMATRIX™ vaccines have been shown to induce CD4+ and CD8+ T cell responses to a range of antigens in both animal models and in human studies. Additionally, ISCOMATRIX™ vaccines have been shown to be safe and generally well tolerated in several clinical trials. Preliminary studies demonstrated that the prototype HCV Core ISCOMATRIX™ vaccine induced strong CD4+ and CD8+ T cell responses in monkeys following immunisation. Here we show the results of a Phase I placebo controlled, dose escalation clinical study designed to evaluate the safety, tolerability and immunogenicity of the HCV Core ISCOMATRIX™ vaccine in healthy individuals. The 30 subjects received 3 immunisations of HCV Core ISCOMATRIX™ vaccines or placebo vaccine on days 0, 28 and 56. The HCV Core ISCOMATRIX™ vaccines contained 5, 20 or 50 μg HCV Core protein with 120 μg ISCOMATRIX™ adjuvant. The adverse events reported were generally mild to moderate in severity, of short duration and self-limiting. The most common adverse events were injection site reactions such as pain and redness as well as myalgia. Antibody responses were detected in all but one of the participants receiving the HCV Core ISCOMATRIX™ vaccine and there was no indication of a dose response. CD8+ T cell responses were only detected in 2 of the 8 participants receiving the highest dose. T cell cytokines were detected in 7 of the 8 participants in the highest dose group. The results of this study support the further evaluation of this prototype HCV Core ISCOMATRIX™ vaccine in HCV infected subjects.

ISCOMATRIX: a novel adjuvant for use in prophylactic and therapeutic vaccines against infectious diseases

The ISCOMATRIX adjuvant has antigen delivery and presentation properties as well as immunomodulatory capabilities, which combine to provide enhanced and accelerated immune responses. The responses are broad, including a range of subclasses of antibodies as well as CD4(+) and CD8(+) T-cells. A range of ISCOMATRIX vaccines (ISCOMATRIX adjuvant combined with antigen) have now been tested in clinical trials and have been shown to be generally safe and well tolerated as well as immunogenic, generating both antibody (Ab) and T-cell responses. The mechanisms by which ISCOMATRIX adjuvant facilitates its immune effects are the scope of significant study and indicate that ISCOMATRIX adjuvant (i) rapidly traffics antigen into the cytosol of multiple dendritic cell subsets, (ii) induces the induction of an array of cytokines and chemokines and (iii) links the innate and adaptive immune responses in vivo in a Toll-like-receptor-independent but MyD88-dependent manner. These data highlight the clinical utility of ISCOMATRIX adjuvant in the development of prophylactic and therapeutic vaccines for infectious disease.

ISCOMATRIX vaccines mediate CD8+ T-cell cross-priming by a MyD88-dependent signaling pathway.

Generating a cytotoxic CD8+ T‐cell response that can eradicate malignant cells is the primary objective of cancer vaccine strategies. In this study we have characterized the innate and adaptive immune response to the ISCOMATRIX adjuvant, and the ability of vaccine antigens formulated with this adjuvant to promote antitumor immunity. ISCOMATRIX adjuvant led to a rapid innate immune cell response at the injection site, followed by the activation of natural killer and dendritic cells (DC) in regional draining lymph nodes. Strikingly, major histocompatibility complex (MHC) class I cross‐presentation by CD8α+ and CD8α− DCs was enhanced by up to 100‐fold when antigen was formulated with ISCOMATRIX adjuvant. These coordinated features enabled efficient CD8+ T‐cell cross‐priming, which exhibited prophylactic and therapeutic tumoricidal activity. The therapeutic efficacy of an ISCOMATRIX vaccine was further improved when co‐administered with an anti‐CD40 agonist antibody, suggesting that ISCOMATRIX‐based vaccines may combine favorably with other immune modifiers in clinical development to treat cancer. Finally, we identified a requirement for the myeloid differentiation primary response gene 88 (MyD88) adapter protein for both innate and adaptive immune responses to ISCOMATRIX vaccines in vivo. Taken together, our findings support the utility of the ISCOMATRIX adjuvant for use in the development of novel vaccines, particularly those requiring strong CD8+ T‐cell immune responses, such as therapeutic cancer vaccines.

Development of prophylactic and therapeutic vaccines using the ISCOMATRIX adjuvant

Adjuvants are components that when added to subunit antigen (Ag) vaccines boost their immunogenicity and thus immune efficacy. However, there are few adjuvants that are approved for clinical use resulting in a critical need for the development of safe and effective adjuvants for use in both prophylactic and therapeutic vaccines. The paucity of appropriate adjuvants is more chronic for the development of therapeutic vaccines for cancer and chronic infectious disease, which need to induce cytotoxic T‐cell responses via cross‐presentation of the vaccine Ag by dendritic cells. The ISCOMATRIX adjuvant represents a unique adjuvant system that facilitates Ag delivery and presentation as well as immunomodulation to provide enhanced and accelerated immune responses. The immune responses generated are of broad specificity to the vaccine Ag, and include robust antibody responses of multiple subclasses as well as both CD4+ and CD8+ T‐cell responses. Here we discuss our understanding of the mechanisms of action by which ISCOMATRIX adjuvant may facilitate these integrated immune responses and touch on insights gained through its clinical experience.

Intranasal immunisation with influenza-ISCOM induces strong mucosal as well as systemic antibody and cytotoxic T-lymphocyte responses.

Intranasal administration of vaccines is preferred for induction of mucosal immune responses. In this study, mice were immunised intranasally and subcutaneously with influenza-immuno stimulating complexes (influenza-ISCOM). The intranasal dose was 15-times the subcutaneous dose. All mice dosed with influenza-ISCOMs survived challenge with live virus and comparable serum antibody and splenic cytotoxic T-lymphocyte responses were detected in both groups. Induction of mucosal IgA was significantly higher with intranasal immunisation and was comparable to responses induced with the heat labile enterotoxin of Escherichia coli as adjuvant. These findings demonstrate that intranasal administration of high dose influenza-ISCOM results in potent systemic and mucosal immune responses.