Induction of HCA587-specific antitumor immunity with HCA587 protein formulated with CpG and ISCOM in mice

HCA587 (also known as MAGE-C2) is a “cancer-testis” antigen highly expressed in a number of malignancies with unique immunological properties, making it a promising target for tumor immunotherapy. In this report, we demonstrated that HCA587 protein, when formulated with adjuvants CpG–containing oligodeoxynucleotides (CpG ODN) and ISCOM, was capable of inducing a potent cellular and humoral immune response as indicated by the presence of a large number of HCA587-specific, IFN-γ-producing CD4⁺ T cells and high levels of HCA587-specific antibodies. More importantly, vaccination with HCA587 conferred protection against challenge with HCA587-expressing B16 melanoma in prophylactic and therapeutic settings. In analysis of the mechanisms underlying the protective effect, we showed that the vaccination was followed by enhanced accumulation of tumor-infiltrating lymphocytes (TILs) with enrichment of conventional CD4⁺ T cells but reduced representation of Treg cells. Further, the antitumor effect was largely abrogated in mice either depleted of CD4⁺ T cells or deficient for IFN-γ. These results indicate that HCA587 protein vaccine possesses evident antitumor activity in a mouse model and holds promise for treatment of human cancers.

Adjuvant effects of saponins on animal immune responses

Vaccines require optimal adjuvants including immunopotentiator and delivery systems to offer long term protection from infectious diseases in animals and man. Initially it was believed that adjuvants are responsible for promoting strong and sustainable antibody responses. Now it has been shown that adjuvants influence the isotype and avidity of antibody and also affect the properties of cell-mediated immunity. Mostly oil emulsions, lipopolysaccharides, polymers, saponins, liposomes, cytokines, ISCOMs (immunostimulating complexes), Freund's complete adjuvant, Freund's incomplete adjuvant, alums, bacterial toxins etc., are common adjuvants under investigation. Saponin based adjuvants have the ability to stimulate the cell mediated immune system as well as to enhance antibody production and have the advantage that only a low dose is needed for adjuvant activity. In the present study the importance of adjuvants, their role and the effect of saponin in immune system is reviewed.

Partial protection against tissue cysts formation in pigs vaccinated with crude rhoptry proteins of Toxoplasma gondii

A vaccine containing crude Toxoplasma gondii rhoptry proteins incorporated in the immunostimulating complexes (ISCOM) adjuvant was tested in pigs for protecting against tissue cyst formation. For this, 38 mixed breed pigs were divided into four groups, G1 (vaccinated challenged, n=10) received two doses (100 microg/dose) of the rhoptry vaccine at days 0 and 21, G2 (vaccinated challenged, n=10) received viable tachyzoites (7 x 10(7)) of the RH strain at day 0, G3 (unvaccinated challenged, n=10) and G4 (unvaccinated unchallenged, n=8). Pigs were challenged with 4 x 10(4) VEG strain oocysts 57 days later. The G1 pigs produced high IgG antibody levels in the indirect enzyme-linked immunosorbent assay (ELISA) after the second dose of rhoptry vaccine, but were not clinically protected against a high dose oocyst challenge. Partial protection was observed in G1 at the chronic phase of infection, when compared with G3. Pigs in group 2 developed high antibody levels and were protected against clinic signs. T. gondii was not detected in two (G1) and three (G2) pigs by mouse bioassay. The results indicate partial protection in pigs vaccinated with a rhoptry vaccine.

Adjuvants and Antibody Production: Dispelling the Myths Associated with Freund's Complete and Other Adjuvants

Adjuvants have been used for more than 70 yr to enhance the immune response of the host animal to an antigen. Among the mechanisms that adjuvants use to enhance the immune response are the "depot" effect, antigen presentation, antigen targeting, immune activation/modulation, and cytotoxic lymphocyte induction. The immunostimulatory properties of adjuvants result in inflammation, tissue destruction, and the potential for resulting pain and distress in the host animal. The inflammatory lesions produced by adjuvants such as Freund's complete adjuvant (FCA) have led some to conclude that pain and distress are present, even in cases where the scientific evidence fails to support this conclusion. Recommendations and regulations in the literature, based on available scientific evidence, provide guidance on total adjuvant volumes, volumes per site, routes of injection, booster injections, and adjuvants used for antibody production. Among the numerous adjuvants that are used for experimental antibody production reviewed in this article, many claim to be less inflammatory, tissue destructive, and painful than FCA while producing equal or superior antibody responses. Although no adjuvant surpasses FCA for experimental antibody production against a wide range of antigenic molecules, many produce excellent antibody responses with less inflammation and tissue destruction. Balancing the requisite degree of immuno-stimulation and the extent of inflammation, necrosis, and potential pain and distress requires consideration of the nature of the antigen, the host immune responsiveness, the adjuvant's mechanisms of action, and the desired end-product. In cases where the antigen is a weak immunogen or has a very limited availability, the type and role of adjuvant becomes a critical component in producing an acceptable immune response and humoral antibody response.

A role for dendritic cells in the priming of antigen-specific CD4+ and CD8+ T lymphocytes by immune-stimulating complexes in vivo

Immune-stimulating complexes (ISCOMS) are adjuvant vectors which are unusual in being able to prime both CD4(+) and CD8(+) T cells by parenteral and mucosal routes. However, their mode of action is unclear and to define better the cellular interactions involved we have studied the ability of ISCOMS containing ovalbumin (OVA) to prime TCR transgenic CD4(+) or CD8(+) T cells in vivo. Immunization with OVA ISCOMS caused activation and clonal expansion of CD4(+) and CD8(+) T cells in the T cell areas of the draining lymph nodes, followed by the migration of both CD4(+) and CD8(+) T cells into the B cell follicle. The T cells were primed to proliferate and secrete IFN-gamma after re-stimulation in vitro with the appropriate OVA peptide and CD8(+) T cell priming occurred in the absence of CD4(+) T cells. Increasing the number of dendritic cells (DC) in vivo with flt3 ligand augmented the expansion and activation of the OVA-specific T cells, particularly CD8(+) T cells. These studies indicate DC play a central role in the priming of both CD4(+) and CD8(+) T cells in vivo, and suggest that an ability to target DC may allow ISCOMS to be powerful vaccine vectors for stimulating protective immunity.

A candidate phocid herpesvirus vaccine that provides protection against feline herpesvirus infection

Phocid herpesvirus type 1 (PhHV-1) causes significant morbidity and mortality among young and immunocompromised harbour seals. Therefore, the availability of an effective PhHV-1 vaccine would be of importance for orphanages and seal rehabilitation centres. Since possibilities to test PhHV-1 candidate vaccines in the target species are limited, a suitable animal model is needed. Given the close genetic and antigenic relationships between PhHV-1 and feline herpesvirus (FHV), the FHV cat system could be considered to test candidate PhHV-1 vaccines. Here we have tested a PhHV-1 based ISCOM vaccine for its protective efficacy against FHV infection in cats. To this end, three groups of cats were vaccinated thrice with ISCOM adjuvanted PhHV-1, FHV, and mock vaccines, respectively. One month after the last vaccination, all cats were challenged with a virulent FHV strain. All PhHV-1 and FHV vaccinated cats were protected from developing severe disease and excreted significantly less FHV than the mock vaccinated cats.

Local immune responses to influenza antigen are synergistically enhanced by the adjuvant ISCOMATRIX

The peripheral (draining) lymph node, as the primary site of immune induction, determines the course of systemic responses to an injected antigen. Lymphatic duct cannulation procedures in sheep were used to investigate local immunoreactivity to human influenza virus antigen (Flu ag) admixed with the adjuvant ISCOMATRIX (IMX). Compared to Flu ag or IMX alone, the co-administration of Flu ag and IMX (Flu ag+IMX) synergistically enhanced a number of immunological responses (lymphocyte and blast migration from the node, antigen-specific antibody levels and IL6 output in efferent lymph, and antigen-induced proliferation in cultured efferent lymph cells). Together, these results demonstrate that IMX is an immune modulator, and that lymphatic duct cannulation procedures may be used to evaluate antigen/adjuvant combinations for vaccine development.

Rinderpest virus (RPV) ISCOM vaccine induces protection in cattle against virulent RPV challenge

Rinderpest virus (RPV), a member of genus Morbillivirus in the family Paramyxoviridae, causes an acute and often fatal disease in cattle and other large ruminants. A subunit rinderpest vaccine consisting of an immune-stimulating complex (ISCOM) incorporating the RPV haemaggulutinin (H) protein, was examined for its ability to induce protective immunity in cattle, the natural host of RPV. All of four cattle vaccinated with the ISCOM vaccine survived challenge with virulent virus. Three were solidly protected, showing no clinical signs of infection, while the fourth animal developed only mild and transient symptoms. Virus neutralizing antibodies were produced at a significant level in all vaccinated cattle. These results indicate that this ISCOM vaccine is effective in producing protective immunity in cattle and should be a suitable means of delivering glycoprotein antigens from other morbilliviruses.

A randomized, double blind study in young healthy adults comparing cell mediated and humoral immune responses induced by influenza ISCOM vaccines and conventional vaccines

Although current influenza vaccines have been shown to reduce influenza-related morbidity and mortality, there is a desire to develop more efficacious products. Vaccines which can induce CD8(+) cytotoxic T cell (CTL) responses in addition to strong antibody responses may be more effective in preventing disease since it has been demonstrated that CTL contribute to protective immunity, even against drift variants of influenza A viruses. The immunogenicity of two types of experimental influenza vaccines, which were based on immune stimulating complexes (ISCOM), were evaluated and compared with a conventional non-adjuvanted inactivated split virion vaccine, after immunization of human volunteers. In this randomized, double blind study, it was shown that the ISCOM vaccines altered the kinetics of the serum antibody response, resulting in more rapid titer rises against the vaccine strains. This accelerated antibody response coincided with enhanced in vitro proliferative T cell responses, which were observed shortly after vaccination. In addition, CTL responses were observed in a higher proportion of the vaccinees receiving an ISCOM vaccine, than in vaccinees receiving the conventional influenza vaccine.

Preparation and characterisation of quillaja saponin with less heterogeneity than Quil-A

Immunisation against pathogens remains one of the most effective ways of preventing or reducing losses due to infectious diseases in animal husbandry. When inactivated vaccines are used, adjuvants are most often required to obtain satisfactory immune responses. One such type of adjuvant is saponin derived from the bark of Quillaja saponaria Molina, a tree of the rose family. A few different commercial sources exist, but due to the structural complexity and heterogeneity of these saponin preparations, it has been difficult to establish exactly which components are responsible for the adjuvant activity. By carefully selecting the bark source, we have succeeded in preparing a much less heterogeneous preparation of quillaja saponin. In this report we describe the preparation, in terms of structural complexity, hemolytic activity, adjuvant activity, and its ability to form ISCOM matrix. This new preparation could have implications for use per se, or as starting material for more effective preparation of pure substances.

Immunomodulation by iscoms, immune stimulating complexes

The iscom is a uniform stable complex consisting of cholesterol, phospholipid, adjuvant-active saponin, and antigen. The iscom matrix is a particulate complex with identical composition, shape, and morphology, but lacking the incorporated antigen. The assembly of the complex is based on hydrophobic interactions, but antigens that are not hydrophobic can be conjugated with a hydrophobic tail or hidden hydrophobic regions can be exposed, e.g., by acid treatment, to facilitate the incorporation into iscoms. The functional aspects of iscoms are described emphasizing immunomodulation in mouse models. Iscoms prominently enhance the antigen targeting, uptake, and activity of antigen presenting cells including dendritic and B cells and macrophages resulting in the production of proinflammatory cytokines, above all interleukin (IL)-1, IL-6, and IL-12. The expression of costimulatory molecules major histocompatibility complex (MHC) class II, B7.1 and B7.2, is also enhanced. The latter partly explains why the iscom is an efficient adjuvant for elderly mice. Iscoms enhance the Th1 type of response with increased production of IL-2 and interferon gamma. However, with some antigens and particularly in monkeys immunized with HIV iscoms, the production of IL-4 was enhanced. IL-4, IL-2, and interferon gamma (IFNgamma) together with the beta chemokines MIP-1alpha and MIP-1beta correlated with protection against challenge infection with a chimeric virus (simian immunodeficiency virus-human immunodeficiency virus). Iscoms were also shown to induce a potent immune response in the newborn and to be an efficient delivery system for mucosal administration. Technical information is given about formulation of iscoms and about handling of antigens to optimize their incorporation into iscoms.

Comparison of immunity generated by nucleic acid-, MF59-, and ISCOM-formulated human immunodeficiency virus type 1 vaccines in Rhesus macaques: evidence for viral clearance

The kinetics of T-helper immune responses generated in 16 mature outbred rhesus monkeys (Macaca mulatta) within a 10-month period by three different human immunodeficiency virus type 1 (HIV-1) vaccine strategies were compared. Immune responses to monomeric recombinant gp120SF2 (rgp120) when the protein was expressed in vivo by DNA immunization or when it was delivered as a subunit protein vaccine formulated either with the MF59 adjuvant or by incorporation into immune-stimulating complexes (ISCOMs) were compared. Virus-neutralizing antibodies (NA) against HIV-1SF2 reached similar titers in the two rgp120SF2 protein-immunized groups, but the responses showed different kinetics, while NA were delayed and their levels were low in the DNA-immunized animals. Antigen-specific gamma interferon (IFN-gamma) T-helper (type 1-like) responses were detected in the DNA-immunized group, but only after the fourth immunization, and the rgp120/MF59 group generated both IFN-gamma and interleukin-4 (IL-4) (type 2-like) responses that appeared after the third immunization. In contrast, rgp120/ISCOM-immunized animals rapidly developed marked IL-2, IFN-gamma (type 1-like), and IL-4 responses that peaked after the second immunization. To determine which type of immune responses correlated with protection from infection, all animals were challenged intravenously with 50 50% infective doses of a rhesus cell-propagated, in vivo-titrated stock of a chimeric simian immunodeficiency virus-HIVSF13 construct. Protection was observed in the two groups receiving the rgp120 subunit vaccines. Half of the animals in the ISCOM group were completely protected from infection. In other subunit vaccinees there was evidence by multiple assays that virus detected at 2 weeks postchallenge was effectively cleared. Early induction of potent type 1- as well as type 2-like T-helper responses induced the most-effective immunity.

Immunological adjuvants and their modes of action

New adjuvant formulations contain a vehicle, which carries antigens to antigen-presenting cells. Examples of vehicles are liposomes, immune-stimulating complexes and microfluidized squalene-in-water emulsions. Adjuvant formulations may contain immunomodulators, which augment cytokine production, such as a synthetic muramyl dipeptide analog or monophosphoryl lipid A. In a primary cascade of cytokine production at the site of antigen + adjuvant injection, TNF-alpha promotes the migration of dendritic cells (DC) to lymphoid tissues while GM-CSF accelerates the differentiation of DC into efficient presenters of antigens to T cells. Adjuvants also up-regulate a secondary cascade of cytokines in lymphoid tissues responding to antigenic stimulation: IL-12 augments the production of IFN-gamma, which favors the production of antibodies of protective isotypes (IgG2a in the mouse). Thus adjuvants can regulate immune responses qualitatively as well as quantitatively. Adjuvant formulations can also activate complement, generating C3d, which binds CD21 on follicular dendritic cells (FDC) and B cells. FDC targeting favors the generation of B lymphocyte memory, which is important for vaccination.

ISCOMs vaccine against experimental leishmaniasis

The major surface glycoprotein (gp63) of Leishmania major incorporated into the immunostimulating complexes (ISCOMs) was used to protect Balb/c mice against experimental infection. Two intraperitoneal vaccinations with low doses of gp63 into ISCOMs (gp63-ISCOMs) induced protective immunity in vaccinated mice as indicated by reduced inflammation and suppressed lesions after experimental challenge. An augmented IgG-specific secretion and a specific switching towards the IgG2a isotype was observed in the serum of vaccinated mice. Gp63-ISCOMs primed spleen cells restimulated in vitro with soluble Leishmania antigen (SLA) or live parasites displayed strong gp63-specific proliferative responses and secreted high levels of interleukin-2, interferon gamma and interleukin-10 but not interleukin-4. No delayed type hypersensitivity response to either SLA or LV39 was detected. These data indicate that gp63-ISCOMs induced a protective immunity in the susceptible Balb/c mice against Leishmania challenge, modulating the immune response towards a Th1 rather than Th2 type.

Kinetics, localization and characteristics of B- and T-cell responses to iscoms containing human influenza virus glycoproteins

B- and T-cell responses have been studied after primary and secondary immunizations of mice with iscoms containing influenza virus envelope glycoproteins. After primary immunization both B- and T-cell responses were initiated in the draining lymph nodes. T-cells showed peak activity with respect to proliferation and cytokine production after five to eight days and the highest number of IgG secreting cells (IgG-SC) was recorded at day seven. The responses in the spleen developed slowly but were of longer duration. Cytokines produced by spleen cells included high levels of IFN-gamma and IL-2. After a secondary immunization the frequencies of IgG-SC were drastically increased in both LN and spleen, but decreased rapidly with time. At day eight after the secondary immunization high numbers of IgG-SC were detected in the bone marrow. High titres of IgG1 and IgG2a and substantial titres of IgG2b and IgG3 were detected in serum.

Induction of a Th1 immune response and simultaneous lack of activation of a Th2 response are required for generation of immunity to leishmaniasis

Experimental systems based on immunization with plasmid DNA or immune-stimulating complexes were used to delineate the requirements for generation of protective immunity against murine leishmaniasis. Vaccination with plasmid DNA encoding the host-protective Leishmania major parasite surface Ag-2 primed for an essentially exclusive Th1 response that protected mice against L. major infection. In contrast, parasite surface Ag-2 in immune-stimulating complexes generated an immune response with mixed Th1-like and Th2-like properties that was not protective despite the activation of large numbers of CD4+ T cells secreting IFN-gamma. These results indicate that a Th1 response is sufficient to protect against cutaneous leishmaniasis, but the induction of a simultaneous Th2 response abrogates the Th1 effector function. DNA vaccines may therefore have an advantage for diseases in which protection depends on the induction of Th1 responses.

Effects of carbohydrate modification of Quillaja saponaria Molina QH-B fraction on adjuvant activity, cholesterol-binding capacity and toxicity

The iscom is an efficient antigen-presenting system for various antigens inducing both MHC class I and class II restricted immune responses. Protective immunity has been evoked against a variety of infectious agents. The saponin adjuvant Quil A, which was originally used to form iscoms, is composed of a mixture of structurally similar triterpenoids from Quillaja saponaria Molina having different biological activities. A purified, toxic Quillaja triterpenoid fraction with strong adjuvant activity, designated QH-B, was used to study whether modification of the carbohydrate moiety with sodium periodate would alter the toxicity without harming adjuvant activity and cholesterol-binding capacity. Most sugars, and in particular Api, Gal and Xyl, were modified by periodate treatment with only minor changes of the molecular weights indicating no loss of sugar residues. The adjuvant activity of QH-B was reduced in a dose-related manner, and at a concentration of 25 mM sodium periodate a significant reduction in toxicity was observed. The differences in both toxicity and adjuvant activity of the periodate-treated QH-B could be derived from alterations in the structure of the sugars Gal and Xyl, while modification of Api may influence adjuvant activity but not toxicity in vivo. The cholesterol-binding capacity, a prerequisite for iscom formation, was not affected by periodate oxidation at the doses tested. However, the use of modified QH-B as described in the present study for iscom-matrix formation resulted in "saponin-lipid complexes" which, to a various degree or totally, deviated from the characteristic iscom morphology.

In vivo and in vitro induction of IL-6 by Quillaja saponaria molina triterpenoid formulations

Quillaja saponaria Molina and some of the defined Quillaja components are potent adjuvants. An important function of adjuvants is the activation of antigen-presenting cells (APC), a prerequisite for the development of immune responses. Interleukin 6 (IL-6) has been identified as a key factor in the generation of cytolytic T lymphocytes, which constitute an important effector mechanism elicited by immuno-stimulatory complex (iscom)-borne antigens. To identify factors relevant to the unique property of iscoms to mediate CTL responses, we analysed the capacity of different defined Quillaja triterpenoid components in various formulations to stimulate production of IL-6 by APC in vitro and in vivo. The iscom formed with Quillaja adjuvant and incorporated influenza virus envelope proteins elicited the highest secretion of IL-6. The production of IL-6 was also stimulated by the antigen free matrix of the iscom and even by the Quillaja triterpenoids as free components albeit to a significantly lesser extent. Among the various combinations of QH-A and QH-C tested and also the original semipurified spikoside, the QH 7.0.3 matrix was the most efficient formulation for activation of IL-6 production by APC. In general, an increasing proportion of QH-A vs QH-C increases the capacity to activate APC. The results demonstrate that the incorporated antigen and the adjuvant component in the same particle have the synergistic effects on immunogenicity.

Iscoms containing purified Quillaja saponins upregulate both Th1-like and Th2-like immune responses

The immune stimulating complex (iscom) is built up by antigen, cholesterol, phospholipids, and adjuvant active Quillaja saponins. Previous studies have shown that iscoms containing Quil A (a semipurified preparation of saponins) efficiently induce antibody and cell-mediated immune responses. In this study, we demonstrate that iscoms containing a mixture of two purified low toxicity Quillaja saponin fractions (ISCOPREP 703) are able to upregulate both Th1-like and Th2-like immune responses. Thus, ovalbumin (OVA) iscoms induced higher levels of antigen-specific IgG1 and IgG2a antibodies and increased the production of both IFN-gamma and IL-4 compared with OVA administered without adjuvant. In contrast, OVA formulated in Al(OH)3 elicited IgG1 and IgE antibodies and primed spleen cells producing IL-4 and IL-10, suggesting the activation of primarily Th2-like cells. These findings underline that adjuvants are able to alter the character of immune responses and may be used to generate responses with desired properties.

In vitro activation of antigen-presenting cells (APC) by defined composition of Quillaja saponaria Molina triterpenoids

The capacity of adjuvants to stimulate cytokine production by APC is important for the initiation of the immune response. Novel adjuvant formulations based on the iscom technology have been developed using selected triterpenoid components from Quillaja saponaria Molina. Five of these new Quillaja formulations were used to prepare matrix (an antigen-free particle) and tested for their capacity to stimulate IL-1 secretion by murine peritoneal cells in vitro. The formulation denominated QH 7.0.3 was superior to the other matrix formulations, including the original spikoside matrix. The QH 7.0.3 formulation in iscoms containing influenza virus envelope antigens induced IL-1 secretion more efficiently than the antigen-free matrix, or a mixture of matrix and viral antigens, or the free Quillaja components of similar composition. Compared with adjuvants known as IL-1 inducers, QH 7.0.3 flu-iscoms were as efficient as the most prominent IL-1 inducer, i.e. lipopolysaccharide (LPS) and superior to cholera toxin (CT) and muramyl dipeptide (MDP). These results indicate that the composition per se of triterpenoids included in iscoms or matrix has a prominent influence on the level of APC activation which may result in qualitatively different immune responses in vivo.

Induction of homologous virus neutralizing antibodies in guinea-pigs immunized with two human immunodeficiency virus type 1 glycoprotein gp120-iscom preparations. A comparison with other adjuvant systems

The immunogenicity in guinea-pigs of the human immunodeficiency virus type 1 envelope glycoprotein gp120 in immune stimulating complex (iscom) was compared to that of gp120 adjuvanted with QuilA-matrix (iscom without attached antigen), aluminium hydroxide (alum) and the Ribi adjuvant system. Gp120 was either incorporated into iscoms by covalent conjugation (iscom(c)) or by acid treatment of gp120 (iscom(a) and both these preparations induced high ELISA antibody titres to gp120. Virus neutralizing (VN) antibodies were most frequently induced by gp120 in iscom(c), iscom(a) or in alum and correlated to high titres to the V3-region of gp120. Further, antibodies induced by gp120-iscom(c) most efficiently inhibited binding of a VN monoclonal antibody GP13 to the CD4 binding region of gp120 whereas gp120-iscom(a) induced the highest mean titre of antibodies blocking the binding of [125I]gp120 to CD4. These results suggest that the gp120-iscom preparations efficiently induced high levels of gp120 specific antibodies and that the adjuvant formulation of gp120 affect the specificity and functional properties of elicited antibodies.

Antigen presentation by naive macrophages, dendritic cells and B cells to primed T lymphocytes and their cytokine production following exposure to immunostimulating complexes

Influenza virus envelope proteins incorporated into immunostimulating complexes (iscoms) are taken up and processed by various kinds of antigen-presenting cells (APC), encompassing peritoneal cells (PEC), unfractionated splenocytes, splenic dendritic cells (DC) or B cells. The iscom-pulsed naive APC stimulated primed T cells to proliferate and produce cytokine in vitro. In contrast, only DC and B cells pulsed with the same antigen (Ag) in the micelle form functioned as accessory cells stimulating the primed T cells to proliferate and produce cytokine. In general, iscoms were better inducers of cell proliferation than micelles. Iscoms stimulated more secretion of IL-2 and interferon-gamma (IFN-gamma) than the micelles, but both antigenic forms stimulated secretion of IL-4. DC and B cells pulsed with iscoms stimulated most efficiently the secretion of IL-2 and IFN-gamma. DC were superior to the other APC in stimulating primed T cells to secrete IFN-gamma. On the other hand, micelles stimulated more efficiently than iscoms splenic T cells from micelle-primed as well as iscom-primed mice to secrete IL-10. These data indicate that influenza virus envelope proteins incorporated in iscoms stimulate a broad T cell response, possibly emphasizing a Th1 type of response. The same Ag in a micelle form induce a more prominent Th2 type of T cell response. The results indicate that the administration of an Ag in an adjuvant formulation can superimpose a different cytokine profile on the immune response than that induced by the protein Ag alone.

Adjuvant activity of non-toxic Quillaja saponaria Molina components for use in ISCOM matrix

It is well established that ISCOMs function efficiently as an antigen-presenting system and protective immunity has been evoked against a variety of infectious agents. The built-in saponin adjuvant from Quillaja saponaria Molina is responsible for the strong immunoenhancing activity displayed by the ISCOM. However, to allow the use of ISCOMs in human vaccines it is necessary to determine the immunological properties and toxicity of chemically defined Quillaja components. Thus, the present study was carried out in a mouse model to determine the adjuvant activity and toxicity of "free", isolated Quillaja components, as well as formulated into particles, i.e. ISCOM matrix. The purified Quillaja components and the ISCOM matrix formulations were examined for their adjuvant activity in a model system consisting of purified influenza virus antigen and Quillaja saponins. It was demonstrated that a Quillaja component, designated QH-C, either as a "free" component or in an ISCOM matrix, has a strong adjuvant activity, but little or no toxicity in the doses tested. In addition, QH-C in the form of ISCOM matrix does not induce any local reactions at the site of injection. Thus, ISCOMs containing the QH-C component, devoid of toxicity, but with strong adjuvant activity, can prove to be useful in adjuvant formulations for human use.

Immunopotentiation of local and systemic humoral immune responses by ISCOMs, liposomes and FCA: role in protection against influenza A in mice

The immunogenicity and protective efficacy of an influenza A subunit vaccine preparation administered to mice in an aqueous form, or presented as immunostimulatory complexes (ISCOMs), liposomes or with Freund's complete adjuvant (FCA), were assessed in comparative studies with live infectious virus. Both intranasal and parenteral routes of administration were assessed. An enzyme-linked immunosorbent assay (ELISA) was used to measure nasal wash and serum antibody responses in groups of unprimed mice, while protection was determined by the recovery of homologous influenza virus from mouse nasal washes and lung homogenates following challenge infection by the intranasal route. The results showed that parenteral administration of the influenza antigen preparations induced variable levels of both local and systemic antibodies at weeks 3, 7 and 22 postimmunization. Although the overall greatest levels of antibody and protection were elicited in mice following live virus infection, formulation of influenza surface haemagglutinin (HA) and neuraminidase (NA) proteins into ISCOMs elicited high and persistent antibody responses and provided relatively good protection of the upper and lower respiratory tracts of these animals. The results also show a relatively poor effect of the subunit antigen preparations in promoting humoral immune responses and protection irrespective of the nature of their presentation, when given by the intranasal route.

Effects of adjuvants and multiple antigen peptides on humoral and cellular immune responses to gp160 of HIV-1

The capacity of five different adjuvants, AlPO4, a muramyldipeptide formulation (MDP.TSL), Freund's adjuvant, immunostimulating complex and its matrix components to elicit humoral and cellular responses in rabbits immunized with the human immunodeficiency virus type 1 (HIV-1) envelope protein rgp160IIIB was compared. The highest antibody titers against gp160 and gp41/gp120 epitopes were seen with rgp160 in MDP.TSL or Freund's adjuvant, whereas the broadest responses were seen in rabbits immunized with rgp160 in matrix or MDP.TSL. The broadest spectrum of high-avidity antibodies was also induced by rgp160 in MDP.TSL. Neutralizing titers against HIV-1IIIB, low titers to HIV-1MN, and the most efficient inhibition of viral cell-to-cell spread was seen with rgp160 in MDP.TSL. The strongest and most persisting cellular responses were induced by rgp160 in AlPO4 or MDP.TSL. Using MDP.TSL as the adjuvant, we also improved the immune response against gp120 epitopes by boosting rgp160-primed rabbits with rgp160, multiple antigenic peptides (MAPs), or unconjugated peptides. The MAPs induced high neutralizing titers and were superior to rgp160 alone in inducing both humoral and cellular reactivity. MAPs are therefore strong candidates for inclusion into future HIV-1 vaccines.

Adjuvants--a balance between toxicity and adjuvanticity

Adjuvants have been used to augment the immune response in experimental immunology as well as in practical vaccination for more than 60 years. The chemical nature of adjuvants, their mode of action and the profile of their side effects are highly variable. Some of the side effects can be ascribed to an unintentional stimulation of different mechanisms of the immune system whereas others may reflect general adverse pharmacological reactions. The most common adjuvants for human use today are still aluminium hydroxide, aluminium phosphate and calcium phosphate although oil emulsions, products from bacteria and their synthetic derivatives as well as liposomes have also been tested or used in humans. In recent years monophosphoryl lipid A, ISCOMs with Quil-A and Syntex adjuvant formulation (SAF) containing the threonyl derivative of muramyl dipeptide have been under consideration for use as adjuvants in humans. At present the choice of adjuvants for human vaccination reflects a compromise between a requirement for adjuvanticity and an acceptable low level of side effects.