Iscom--an immunostimulating complex.
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Adjuvants, Immunologic↗
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Feline immunodeficiency virus subunit vaccines that induce virus neutralising antibodies but no protection against challenge infection.
Three experimental vaccines against feline immunodeficiency virus (FIV), all based on viral antigens presented via immune stimulating complexes (iscoms), were tested for their capacity to induce protection in cats from FIV infection. The respective vaccines consisted of FIV propagated in Crandell feline kidney (CrFK) cells (FIV-iscoms); FIV-iscoms spiked with recombinant vaccinia virus expressed FIV envelope glycoprotein incorporated into iscoms (FIV-iscoms + vGR657x15-iscoms) and vGR657x15-iscoms spiked with recombinant FIV Gag protein incorporated into iscoms (vGR657x15-iscoms + FIV-Gag-iscoms). Simian immunodeficiency virus envelope glycoprotein incorporated into iscoms, iscoms prepared with uninfected CrFK cells, and PBS served as controls. All cats vaccinated with vGR657x15-iscoms combined with FIV-iscoms or FIV-Gag-iscoms developed Env-specific plasma antibody responses. These antibodies neutralised FIV infection in CrFK cells, but failed to neutralise FIV infection in primary feline thymocytes. FIV-iscoms induced poor Env-specific responses and only one out of six cats developed antibodies that neutralised FIV in the CrFK cell based assay. Four weeks after challenge all cats proved to be infected, showing that none of the vaccine preparations provided protection. In contrast, 2 weeks after infection, virus infected peripheral blood mononuclear cells were only observed in cats vaccinated with FIV-iscoms + vGR657x15-iscoms or CrFK-iscoms and to a lesser extent in cats vaccinated with FIV-iscoms and vGR657x15-iscoms + FIV-Gag-iscoms, but not in cats vaccinated with SIV-iscoms or PBS. The differences found in cell associated virus loads amongst the respective groups are discussed in the light of antibody mediated enhancement of infectivity and protective effects provided by Gag-specific T cell responses.
Animals↗
Antigen detection in vivo after immunization with different presentation forms of rabies virus antigen: involvement of marginal metallophilic macrophages in the uptake of immune-stimulating complexes.
Several mechanisms have been postulated to explain the relatively high immunogenicity of antigens presented in immune-stimulating complexes (iscom). Their potency can in part be explained by the specific targeting of these structures to cells presenting antigens to the immune system. However, until now no method for the subcellular detection of iscom in situ was available. In the present study, a novel, fast and simple method for the detection of iscoms in situ is demonstrated. By making use of the lipophilic fluorescent carbocyanine dyes, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) and 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO), rabies virus antigen and iscom prepared with this antigen were visualized with fluorescence microscopy. The labeled antigen and iscoms were observed in macrophages of spleen and liver of mice within 1-2 h after intravenous administration. When administered intramuscularly or in the footpad, uptake in macrophages of draining lymph nodes could be demonstrated. In the spleen, labeled inactivated virus antigen localized preferentially in the marginal zone macrophages and to a lesser extent in the red pulp macrophages. In contrast, antigen presented in iscom was taken up mainly by the marginal metallophilic macrophages and to a much lesser extend by marginal zone macrophages or follicular-dendritic and -B cells. This method enables the detection of iscom and membrane viruses and allows the analysis of their relation to antigen-presenting cells in situ. Here, we demonstrate that iscom containing rabies virus antigen are taken up by a subset of macrophages in the spleen distinct from those that take up inactivated rabies virus antigen not presented in iscom, thereby possibly explaining the observed difference in immunogenicity of these antigen preparations. Furthermore, we show a lower efficiency on the induction of humoral and cellular responses after intravenous immunization for both types of antigen when compared with subcutaneous immunization.
Animals↗
The immunomodulating properties of human respiratory syncytial virus and immunostimulating complexes containing Quillaja saponin components QH-A, QH-C and ISCOPREP703.
A successful vaccine against human RSV (HRSV) is likely to induce a Th1 or a balanced Th1/TH2 cytokine response. We tested a panel of HRSV immunostimulating complexes (ISCOMs) containing different Quillaja saponin fractions (QH-A, QH-C, and 703: a mixture of 70% QH-A and 30% QH-C) with different immunological properties for their capacity of inducing innate and acquired immune responses. The HRSV 703 ISCOMs induced the strongest innate and acquired immune responses, followed by RSV QH-C and QH-A ISCOMs. All three formulations induced various degrees of Th1 bias response with prominent production of IFN-gamma being 10-50 times higher than that of IL-4 and IL-5. The HRSV specific IgG isotype profile correlated with the predominant secretion of Th1 cytokines, with strong induction of IgG2a antibodies. The 703 ISCOMs induced the most pronounced Th1 profile followed by QH-C and QH-A ISCOMs. The high incorporation of F protein in these ISCOMs compared to G protein combined with the Th1 biased nature of ISCOM are likely to be the causes to promote a Th1 type of profile. The prospect to formulate an RSV ISCOM formulation with an optimal Th1/Th2 balance is in reach particularly in view of the versatile properties of the ISCOM concept.
Adjuvants, Immunologic↗
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.
Animals↗
Immune-stimulating complexes induce an IL-12-dependent cascade of innate immune responses.
The development of subunit vaccines requires the use of adjuvants that act by stimulating components of the innate immune response. Immune-stimulating complexes (ISCOMS) containing the saponin adjuvant Quil A are potential vaccine vectors that induce a wide range of Ag-specific responses in vivo encompassing both humoral and CD4 and CD8 cell-mediated immune responses. ISCOMS are active by both parenteral and mucosal routes, but the basis for their adjuvant properties is unknown. Here we have investigated the ability of ISCOMS to recruit and activate innate immune responses as measured in peritoneal exudate cells. The i.p. injection of ISCOMS induced intense local inflammation, with early recruitment of neutrophils and mast cells followed by macrophages, dendritic cells, and lymphocytes. Many of the recruited cells had phenotypic evidence of activation and secreted a number of inflammatory mediators, including nitric oxide, reactive oxygen intermediates, IL-1, IL-6, IL-12, and IFN-gamma. Of the factors that we investigated further only IL-12 appeared to be essential for the immunogenicity of ISCOMS, as IL-6- and inducible nitric oxide synthase knockout (KO) mice developed normal immune responses to OVA in ISCOMS, whereas these responses were markedly reduced in IL-12KO mice. The recruitment of peritoneal exudate cells following an injection of ISCOMS was impaired in IL-12KO mice, indicating a role for IL-12 in establishing the proinflammatory cascade. Thus, ISCOMS prime Ag-specific immune responses at least in part by activating IL-12-dependent aspects of the innate immune system.
Adjuvants, Immunologic↗
A lipid-conjugated immunostimulating complex subunit vaccine against Salmonella infection in turkeys.
Immunostaining complexes (ISCOMs) are multimeric particles and have been used successfully for presentation of membrane proteins. In this study, outer-membrane proteins (OMPs) from Salmonella heidelberg were incorporated into lipid-conjugated ISCOM particles and evaluated for their use in a vaccine for turkeys against homologous and heterologous Salmonella challenge. Two types of lipid-conjugated ISCOMs were examined: ISCOM-phospholipid and ISCOM-sphingolipid preparations. The turkeys were challenged with one of the three Salmonella serotypes: S. heidelberg, S. reading, or S. enteritidis. The turkeys were monitored for clinical signs, shedding pattern post-challenge, and clearance of the challenge Salmonella from selected internal organs. Vaccines containing OMP with either lipid-conjugated ISCOM preparation produced significantly greater (P < 0.01) immune response than OMP alone. Cloacal swabs from turkeys given OMP along with ISCOM-phospholipid and challenged with a homologous serotype were completely negative for Salmonella. A certain degree of cross-protection against heterologous Salmonella was afforded by both OMP-ISCOM vaccines. The isolation rate of Salmonella from internal organs was significantly lower (P < 0.0001) in vaccinated turkeys than in unvaccinated controls.
Animals↗
Antibody responses of chickens to inoculation with Mycoplasma gallisepticum membrane proteins in immunostimulating complexes.
Membrane proteins of Mycoplasma gallisepticum (MG) strain R were extracted with the detergent Mega-10 and incorporated into immunostimulating complexes (ISCOMs). A membrane protein of approximately 64 kD (p64) molecular weight was a major component of MG ISCOMs. Six-week-old specific-pathogen-free leghorn chickens were inoculated by various routes (subcutaneous; combined intranasal and eyedrop; and combined subcutaneous, intranasal, and eyedrop) with 10 micrograms MG proteins in ISCOMs, or inoculated subcutaneously with 10 micrograms MG proteins in Freund's adjuvant. Subcutaneous inoculation of MG ISCOMs, or MG Freund's adjuvant resulted in higher sero-positive rates (detected by enzyme-linked immunosorbent assay) in serum and respiratory tract washings, compared to combined routes of MG ISCOM inoculation. In chickens inoculated subcutaneously with MG ISCOMs antibodies were first detected at 31 days postinoculation (PI) and the sero-positive rate peaked at 56 days PI. Sero-positive rates started to decline at day 64 PI. In the Freund's adjuvant group, MG antibodies were first detected at day 21 PI, and the sero-positive rate peaked at day 39 PI and did not decline. MG antibodies were detected by ELISA in upper respiratory tract and tracheal washes from chickens inoculated subcutaneously with MG ISCOMs and MG Freund's adjuvant. Immunoblots to MG strain R whole cell proteins showed that respiratory tract washings and sera from chickens inoculated subcutaneously with MG ISCOMs contained immunoglobulins to MG proteins, with a prominent reaction to p64.
Animals↗
Immunomodulation by Quillaja saponaria adjuvant formulations: in vivo stimulation of interleukin 12 and its effects on the antibody response.
The capacity of adjuvants to activate Ag-presenting cells during the induction of the primary immune response is of critical importance for the development of protective immunity to a number of pathogens. In this context, interleukin 12 (IL-12) has a key role by controlling the differentiation of T helper cells and favouring the expansion of Th1 cells. The capacity of iscoms with influenza virus Ag (flu-iscoms) and iscom matrix with EBV gp340 Ag to induce IL-12 was analysed in mice. The flu-iscom drives the immune response towards a Th1 type subsequent to IL-12 induction as measured in the serum of H2b, H2d and H2k mice. The iscom presenting the Ag and adjuvant in the same particle was considerably more efficient than the formulation of matrix and Ag in separate particles. Inhibition experiments with mAb neutralizing IL-12, interferon gamma (IFN-gamma) or IL-4, the latter two cytokines representing the Th1 and Th2 type of responses, showed that iscoms induce a broader immune response than that involving IL-12. This was shown by the additional effect that IL-4 neutralization had on the immune response to iscoms. Anti-IL 12 reduced the specific total Ab as well as IgG1, IgG2a and IgG2b while anti-IL 4 influenced the response to iscom by decreasing IgG2a and increasing IgG1. Further, the neutralization experiments indicate that IL-12 has a broader effect than IFN-gamma on the Ab response by influencing the production of IgG1, IgG2a and IgG2b.
Adjuvants, Immunologic↗
Oral vaccination with immune stimulating complexes.
There is a need for non-living adjuvant vectors which will induce a full range of local and systemic immune responses to orally administered purified antigens. Here we describe our experience with lipophilic immune stimulating complexes (ISCOMS) containing the saponin adjuvant Quil A. When given orally, ISCOMS containing the model protein antigen ovalbumin (OVA) induce a wide range of systemic immune responses, including Th1 and Th2 CD4 dependent activity, class I MHC restricted cytotoxic T-cell responses and local production of secretory IgA antibodies. More recent results indicate that ISCOMS may act partly by enhancing the uptake of protein from the gut. In addition, intraperitoneal injection of ISCOMS recruits and activates many components of the innate immune system. including neutrophils, macrophages, and dendritic cells. In parallel, there is increased production of nitric oxide (NO), reactive oxygen intermediates (ROI), interleukins (IL) 1, 6, 12, and gamma interferon (gammaIFN). Of these factors, only IL12 is essential for the immunogenicity of ISCOMS in vivo, as mucosal and systemic responses to ISCOMS are reduced in IL12KO mice, but not in IL4KO, IL6KO, inducible NO synthase (iNOS) KO, or gammaIFN receptor KO mice. We propose that ISCOMS act by targetting antigen and adjuvant to macrophages and/or dendritic cells. This pathway may be amenable to exploitation for vaccine development, especially if combined with another vector with a different mucosal adjuvant profile, such as cholera toxin.
Adjuvants, Immunologic↗
Immunogenicity of various presentation forms of PorA outer membrane protein of Neisseria meningitidis in mice.
In this study we compare different vaccine formulations containing meningococcal PorA outer membrane protein; purified PorA, outer membrane vesicles (OMV) and immune-stimulating complexes (iscom). Bactericidal antibodies could be generated by the OMV and iscom formulation but not with purified PorA using either A1PO4 or Quil-A as adjuvant. OMV and iscom formulations revealed similar immunogenicity when tested in a dose response manner, with respect to bactericidal as well as OMV-binding antibodies. The anti-OMV IgG subclass response induced by PorA in OMV formulation was found in all subclasses IgG1, IgG2a, IgG2b, IgG3. OMP-iscoms induced very high IgG1 anti-OMV antibodies but almost no IgG3 response. Also, OMP-iscoms appeared to be a potent inducer of antibodies directed against linear peptides corresponding to surface exposed loops of PorA. In addition, iscoms as well as purified PorA with Quil-A as adjuvant (but not with A1PO4) induced high levels of antibodies against purified PorA. In summary, in addition to the OMV formulation, only iscoms containing PorA are able to generate an anamnestic and bactericidal antibody response.
Amino Acid Sequence↗
Hydration of lipid films with an aqueous solution of Quil A: a simple method for the preparation of immune-stimulating complexes.
Immune-stimulating complexes (ISCOMs) are stable colloidal complexes of the adjuvant Quil A, cholesterol and phospholipid, which are effective carriers for subunit vaccines. The techniques currently available for the preparation of ISCOMs from the constituent components are rather complex and are based on either centrifugation or dialysis. This note reports a new simple procedure for the preparation of ISCOM matrices based on hydration of a cholesterol/phospholipid film with an aqueous solution of Quil A. It is demonstrated that ISCOM matrices do not form in the absence of phospholipid when prepared by this method. Further, the ratio by weight of phospholipid to either cholesterol or Quil A must be greater than that required for preparation by either dialysis or centrifugation. Photon correlation spectroscopy, negative stain transmission electron microscopy and centrifugation through a sucrose gradient demonstrate that ISCOM matrices can be prepared from cholesterol/lipid films by hydration with an aqueous solution of Quil A when the ratio of phospholipid:cholesterol:Quil A by weight is 6:1:4, respectively. Lower ratios of phospholipid:cholesterol reduce the efficiency of ISCOM formation while higher ratios produce systems containing a mixture of ISCOMs together with liposomes.
Cholesterol↗
The role of antigen-presenting cells and interleukin-12 in the priming of antigen-specific CD4+ T cells by immune stimulating complexes.
Immune stimulating complexes (ISCOMs) containing the saponin adjuvant Quil A are vaccine adjuvants that promote a wide range of immune responses in vivo, including delayed-type hypersensitivity (DTH) and the secretion of both T helper 1 (Th1) and Th2 cytokines. However, the antigen-presenting cell (APC) responsible for the induction of these responses has not been characterized. Here we have investigated the role of dendritic cells (DC), macrophages (Mphi) and B cells in the priming of antigen-specific CD4+ T cells in vitro by ISCOMs containing ovalbumin (OVA). OVA ISCOMs pulsed bone marrow (BM)-derived DC but not BM Mphi, nor naïve B cells prime resting antigen-specific CD4+ T cells, and this response is greatly enhanced if DC are activated with lipopolysaccharide (LPS). Of the APC found in the spleen, only DC had the capacity to prime resting antigen specific CD4+ T cells following exposure to OVA ISCOMs in vitro, while Mphi and B cells were ineffective. DC, but not B cells purified from the draining lymph nodes of mice immunized with OVA ISCOMs also primed resting antigen-specific CD4+ T cells in vitro, suggesting that DC are also critical in vivo. Using DC and T cells from interleukin (IL)-12 p40-/- mice, we also identified a crucial role for IL-12 in the priming of optimal CD4+ T cell responses by OVA ISCOMs. We suggest that DC are the principal APC responsible for the priming of CD4+ T cells by ISCOMs in vivo and that directed targeting of these vectors to DC may enhance their efficancy as vaccine adjuvants.
Adjuvants, Immunologic↗
Induction of protective immunity against Chlamydia trachomatis genital infection by a vaccine based on major outer membrane protein-lipophilic immune response-stimulating complexes.
The significance of delivery systems in modern vaccine design strategies is underscored by the fact that a promising vaccine formulation may fail in vivo due to an inappropriate delivery method. We evaluated the immunogenicity and efficacy of a candidate vaccine comprising the major outer membrane protein (MOMP) of Chlamydia trachomatis delivered with the lipophilic immune response-stimulating complexes (ISCOMs) as a vehicle with adjuvant properties, in a murine model of chlamydial genital infection. Immunocompetent BALB/c mice were immunized intranasally (IN) or intramuscularly (IM) with MOMP, MOMP-ISCOMs, and live or heat-inactivated C. trachomatis serovar D. The level of local genital mucosal Th1 response was measured by assaying for antigen-specific Th1 cell induction and recruitment into the genital mucosa at different times after immunization. Immunization with MOMP-ISCOMs by the IM route induced the greatest and fastest local genital mucosal Th1 response, first detectable 2 weeks after exposure. Among the other routes and regimens tested, only IN immunization with MOMP-ISCOMs induced detectable and statistically significant levels of local genital mucosal Th1 response during the 8-week test period (P < 0.001). In addition, when T cells from immunized mice were adoptively transferred into syngeneic naive animals and challenged intravaginally with Chlamydia, recipients of IM immunization of MOMP-ISCOMs cleared their infection within 1 week and were resistant to reinfection. Animals that received IN immunization of MOMP-ISCOMs were partially protected, shedding fewer chlamydiae than did control mice. Altogether, the results suggested that IM delivery of MOMP-ISCOMs may be a suitable vaccine regimen potentially capable of inducing protective mucosal immunity against C. trachomatis infection.
Adjuvants, Immunologic↗
Immuno-stimulating complexes prepared by ethanol injection.
This study describes the formulation of immuno-stimulating complexes (ISCOMs) utilising the ethanol injection technique. Cholesterol and phosphatidylcholine were dissolved in ethanol and the resulting solution was rapidly injected into a stirred, aqueous solution of the triterpene-saponin mixture Quil-A. The reversed experiment was also carried out by adding the aqueous Quil-A solution to a solution of cholesterol/phosphatidylcholine dissolved in ethanol. This was done by either rapid injection or dropwise addition of the aqueous Quil-A solution. The colloidal dispersions obtained by ethanol injection and reversed addition were compared with formulations obtained by the dialysis and lipid-film hydration methods. In a further experiment, the preparation of ISCOMs from liposomes as precursor structures was investigated. Transmission electron microscopy was used to analyse the resulting colloidal dispersions. Samples were also compared with respect to homogeneity of obtained particle species. The ethanol injection technique led to formation of ISCOMs in high numbers within 2 h post formulation. The reversed rapid injection resulted in a similar colloidal dispersion, differing from the former mainly due to the presence of some helical micellar structures. The reversed, dropwise addition led to the formation of helices as the predominant colloidal structure. Of the three previously established methods, only dialysis led to the formation of ISCOMs within 48 h. The lipid-film hydration method and the approach using liposomes as precursor structures did not produce ISCOMs under the conditions and within the time periods investigated. However, it is known that dispersions prepared by the hydration method equilibrate towards ISCOMs after longer storage. Ethanol injection and reversed rapid injection are simple, cost-effective and quick methods to produce ISCOMs.
Chemistry, Pharmaceutical↗
Protection of rhesus macaques from SIV infection by immunization with different experimental SIV vaccines.
The immunogenicity and efficacy of an inactivated whole SIVmac (32H) preparation adjuvanted with muramyl dipeptide (SIV-MDP) and a gp120-enriched SIVmac (32H) ISCOM preparation (SIV-ISCOM), were compared by immunizing four rhesus macaques (Macaca mulatta) four times with SIV-MDP and four others in the same way with SIV-ISCOM. Two monkeys immunized with whole inactivated measles virus (MV) adjuvanted with MDP (MV-MDP) and two monkeys immunized with MV-ISCOM served as controls. In the SIV-ISCOM-immunized monkeys higher SIV-specific serum antibody titres were found than in the SIV-MDP-immunized monkeys. In contrast to the MV-immunized monkeys all SIV-MDP- and SIV-ISCOM-immunized monkeys were protected against intravenous challenge 2 weeks after the last immunization with 10 median monkey infectious doses (MID50) of a cell-free SIVmac (32H) challenge stock propagated in the human T-cell line C8166. After 43 weeks the protected monkeys were reboosted and 2 weeks later rechallenged with 10 MID50 of the same virus produced in peripheral blood mononuclear cells (PBMC) from a rhesus macaque. None of these animals proved to be protected against this challenge. In a parallel experiment in which the same numbers of monkeys were immunized in the same way, the animals were challenged intravenously with 10 MID50 of PBMC from an SIVmac (32H)-infected rhesus macaque. Two out of four SIV-MDP- and two out of four SIV-ISCOM-immunized monkeys proved to be protected from SIV infection.
Animals↗
Pseudo-ternary phase diagrams of aqueous mixtures of Quil A, cholesterol and phospholipid prepared by the lipid-film hydration method.
Pseudo-ternary phase diagrams of the polar lipids Quil A, cholesterol (Chol) and phosphatidylcholine (PC) in aqueous mixtures prepared by the lipid film hydration method (where dried lipid film of phospholipids and cholesterol are hydrated by an aqueous solution of Quil A) were investigated in terms of the types of particulate structures formed therein. Negative staining transmission electron microscopy and polarized light microscopy were used to characterize the colloidal and coarse dispersed particles present in the systems. Pseudo-ternary phase diagrams were established for lipid mixtures hydrated in water and in Tris buffer (pH 7.4). The effect of equilibration time was also studied with respect to systems hydrated in water where the samples were stored for 2 months at 4 degrees C. Depending on the mass ratio of Quil A, Chol and PC in the systems, various colloidal particles including ISCOM matrices, liposomes, ring-like micelles and worm-like micelles were observed. Other colloidal particles were also observed as minor structures in the presence of these predominant colloids including helices, layered structures and lamellae (hexagonal pattern of ring-like micelles). In terms of the conditions which appeared to promote the formation of ISCOM matrices, the area of the phase diagrams associated with systems containing these structures increased in the order: hydrated in water/short equilibration period<hydrated in buffer/short equilibration period<hydrated in water/prolonged equilibration period. ISCOM matrices appeared to form over time from samples, which initially contained a high concentration of ring-like micelles suggesting that these colloidal structures may be precursors to ISCOM matrix formation. Helices were also frequently found in samples containing ISCOM matrices as a minor colloidal structure. Equilibration time and presence of buffer salts also promoted the formation of liposomes in systems not containing Quil A. These parameters however, did not appear to significantly affect the occurrence and predominance of other structures present in the pseudo-binary systems containing Quil A. Pseudo-ternary phase diagrams of PC, Chol and Quil A are important to identify combinations which will produce different colloidal structures, particularly ISCOM matrices, by the method of lipid film hydration. Colloidal structures comprising these three components are readily prepared by hydration of dried lipid films and may have application in vaccine delivery where the functionality of ISCOMs has clearly been demonstrated.
Adjuvants, Immunologic↗
Different respiratory syncytial virus and Quillaja saponin formulations induce murine peritoneal cells to express different proinflammatory cytokine profiles.
The recognition of a pathogen or a vaccine antigen formulation by cells in the innate immune system leads to production of proinflammatory cytokines, which will determine the ensuing acquired immune response quantitatively and qualitatively. Tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 and IL-6 are the first set of cytokines produced upon such an encounter, which have roles both in protective immunity and immunopathogenesis evident with respiratory syncytial virus (RSV). RSV antigens in different physical adjuvant-vaccine formulations were analysed for their capacity to provoke cultured murine peritoneal cells to produce these three proinflammatory cytokines. RSV immunostimulating complex (ISCOM), i.e. both antigen and adjuvant are incorporated in the same particle, induced high levels of IL-1alpha being of the same magnitude or higher than those of live RSV and lipopolysaccharide (LPS). Live virus and LPS induced higher levels of IL-6 and TNF-alpha than ISCOM and so did non-adjuvanted UV-inactivated RSV but only at high doses. ISCOM-Matrix, i.e. ISCOM without antigens, admixed as a separate entity to inactivated RSV, downregulated or blocked the cytokine response to the inactivated RSV in contrast to ISCOM. Kinetic studies showed that ISCOM induced cytokine production first detected at hours 1, 2, 4 for TNF-alpha, IL-6 and IL-1alpha respectively, which was earlier than for the other antigen formulations containing corresponding doses of antigen and/or Quillaja adjuvant. Peak values for production of TNF-alpha and IL-6 were at 8 h and for IL-1alpha at 72 h following stimulation with ISCOM. The delayed appearance of IL-1alpha may reflect the cell-bound nature of this cytokine.
Adjuvants, Immunologic↗