Development of prophylactic and therapeutic vaccines using the ISCOMATRIX adjuvant

Saponin Nanoparticle Adjuvants Incorporating Toll-Like Receptor Agonists Improve Vaccine Immunomodulation

Over the past few decades, the development of potent and safe immune-activating adjuvant technologies has become the heart of intensive research in the constant fight against highly mutative and immune evasive viruses such as influenza, SARS-CoV-2, and HIV. Herein, we developed a highly modular saponin-based nanoparticle platform incorporating toll-like receptor agonists (TLRas) including TLR1/2a, TLR4a, TLR7/8a adjuvants and their mixtures. These various TLRa-SNP adjuvant constructs induce unique acute cytokine and immune-signaling profiles, leading to specific Th-responses that could be of interest depending on the target disease for prevention. In a murine vaccine study, the adjuvants greatly improved the potency, durability, breadth, and neutralization of both COVID-19 and HIV vaccine candidates, suggesting the potential broad application of these adjuvant constructs to a range of different antigens. Overall, this work demonstrates a modular TLRa-SNP adjuvant platform which could improve the design of vaccines for and dramatically impact modern vaccine development.

Saponin-based adjuvants enhance antigen cross-presentation in human CD11c+ CD1c+ CD5- CD163+ conventional type 2 dendritic cells

BACKGROUND

Adjuvants are key for effective vaccination against cancer and chronic infectious diseases. Saponin-based adjuvants (SBAs) are unique among adjuvants in their ability to induce robust cell-mediated immune responses in addition to antibody responses. Recent preclinical studies revealed that SBAs induced cross-presentation and lipid bodies in otherwise poorly cross-presenting CD11b+ murine dendritic cells (DCs).

METHOD

Here, we investigated the response of human DC subsets to SBAs with RNA sequencing and pathway analyses, lipid body induction visualized by laser scanning microscopy, antigen translocation to the cytosol, and antigen cross-presentation to CD8+ T cells.

RESULTS

RNA sequencing of SBA-treated conventional type 1 DC (cDC1) and type 2 DC (cDC2) subsets uncovered that SBAs upregulated lipid-related pathways in CD11c+ CD1c+ cDC2s, especially in the CD5- CD163+ CD14+ cDC2 subset. Moreover, SBAs induced lipid bodies and enhanced endosomal antigen translocation into the cytosol in this particular cDC2 subset. Finally, SBAs enhanced cross-presentation only in cDC2s, which requires the CD163+ CD14+ cDC2 subset.

CONCLUSIONS

These data thus identify the CD163+ CD14+ cDC2 subset as the main SBA-responsive DC subset in humans and imply new strategies to optimize the application of saponin-based adjuvants in a potent cancer vaccine.

Development of low-cost cage-like particles to formulate veterinary vaccines

Low-cost adjuvants are urgently needed for the development of veterinary vaccines able to trigger strong immune responses. In this work, we describe a method to obtain a low-cost cage-like particles (ISCOMATRIX-like) adjuvant useful to formulate veterinary vaccines candidates. The main components to form the particles are lipids and saponins, which were obtained from egg yolk by ethanolic extraction and by dialyzing a non-refined saponins extract, respectively. Lipids were fully characterized by thin layer chromatography (TLC) and gas-chromatography (GC) and enzymatic methods, and saponins were characterized by TLC, HPLC and MALDI-TOF. Cage-like particles were prepared with these components or with commercial inputs. Both particles and the traditional Alum used in veterinary vaccines were compared by immunizing mice with Ovalbumin (OVA) formulated with these adjuvants and assessing IgG1, IgG2a anti OVA antibodies and specific Delayed-type Hypersensitivity (DTH). In the yolk extract, a mixture of phospholipids, cholesterol and minor components of the extract (e.g. lyso-phospholipids) with suitable proportions to generate cage-like particles was obtained. Also, semi-purified saponins with similar features to those of the QuilA® were obtained. Cage-like particles prepared with these components have 40-50 nm and triggers similar levels of Anti-OVA IgG1 and DTH than with commercial inputs but higher specific-IgG2a. Both adjuvants largely increased the levels of IgG1, IgG2a and DTH in relation to the formulation with Alum. The methods described to extract lipids from egg yolk and saponins from non-refined extract allowed us to obtain an inexpensive and highly effective adjuvant.

Next-Generation Influenza HA Immunogens and Adjuvants in Pursuit of a Broadly Protective Vaccine

Influenza virus, a highly mutable respiratory pathogen, causes significant disease nearly every year. Current vaccines are designed to protect against circulating influenza strains of a given season. However, mismatches between vaccine strains and circulating strains, as well as inferior vaccine effectiveness in immunodeficient populations, represent major obstacles. In an effort to expand the breadth of protection elicited by influenza vaccination, one of the major surface glycoproteins, hemagglutinin (HA), has been modified to develop immunogens that display conserved regions from multiple viruses or elicit a highly polyclonal antibody response to broaden protection. These approaches, which target either the head or the stalk domain of HA, or both domains, have shown promise in recent preclinical and clinical studies. Furthermore, the role of adjuvants in bolstering the robustness of the humoral response has been studied, and their effects on the vaccine-elicited antibody repertoire are currently being investigated. This review will discuss the progress made in the universal influenza vaccine field with respect to influenza A viruses from the perspectives of both antigen and adjuvant, with a focus on the elicitation of broadly neutralizing antibodies.

Tumor ablation plus co-administration of CpG and saponin adjuvants affects IL-1 production and multifunctional T cell numbers in tumor draining lymph nodes

Background

Tumor ablation techniques, like cryoablation, are successfully used in the clinic to treat tumors. The tumor debris remaining in situ after ablation is a major antigen depot, including neoantigens, which are presented by dendritic cells (DCs) in the draining lymph nodes to induce tumor-specific CD8⁺ T cells. We have previously shown that co-administration of adjuvants is essential to evoke strong in vivo antitumor immunity and the induction of long-term memory. However, which adjuvants most effectively combine with in situ tumor ablation remains unclear.

Methods and results

Here, we show that simultaneous administration of cytidyl guanosyl (CpG) with saponin-based adjuvants following cryoablation affects multifunctional T-cell numbers and interleukin (IL)-1 induced polymorphonuclear neutrophil recruitment in the tumor draining lymph nodes, relative to either adjuvant alone. The combination of CpG and saponin-based adjuvants induces potent DC maturation (mainly CpG-mediated), antigen cross-presentation (mainly saponin-based adjuvant mediated), while excretion of IL-1β by DCs in vitro depends on the presence of both adjuvants. Most strikingly, CpG/saponin-based adjuvant exposed DCs potentiate antigen-specific T-cell proliferation resulting in multipotent T cells with increased capacity to produce interferon (IFN)γ, IL-2 and tumor necrosis factor-α in vitro. Also in vivo the CpG/saponin-based adjuvant combination plus cryoablation increased the numbers of tumor-specific CD8⁺ T cells showing enhanced IFNγ production as compared with single adjuvant treatments.

Conclusions

Collectively, these data indicate that co-injection of CpG with saponin-based adjuvants after cryoablation induces an increased amount of tumor-specific multifunctional T cells. The combination of saponin-based adjuvants with toll-like receptor 9 adjuvant CpG in a cryoablative setting therefore represents a promising in situ vaccination strategy.

FMD empty capsids combined with the Immunostant Particle Adjuvant -ISPA or ISA206 induce protective immunity against foot and mouth disease virus

Foot and Mouth Disease Virus (FMDV) causes economy losses and is controlled by vaccination in many countries. Vaccine formulations based on empty capsids or Virus-Like Particles (VLPs) have the advantage of avoiding the biological hazard of using infectious FMDV, albeit are poorly immunogenic. Recently, we have described that ISPA a new Immune Stimulating Complex adjuvant, is useful to improve the response against FMD of vaccines that use inactivated virus. Now, the adjuvant effects of ISPA and ISA 206 (water/oil/water) on a VLPs-based FMD vaccine were evaluated. VLPs (strain A/Argentina/2001) were obtained in mammalian cell cultures and their elicitation of an immune response against FMDV with and without ISPA or ISA 206 was evaluated in mice as a first approach. Notably, VLPs-ISPA and VLPs-ISA 206 vaccines induced protection against viral challenge in 100 % of mice, while protection induced by VLPs alone was of 40 %. Total and neutralizing FMDV antibodies were higher in the VLPs-ISPA and VLPs-ISA 206 groups compared to the VLPs group. VLPs-ISPA induced significantly higher (p < 0.001) IgG1, IgG2a, IgG2b and IgG3 titers than the VLPs vaccine. Moreover, in comparison with non-adjuvanted VLPs, VLPs-ISPA and VLPs-ISA 206 elicited an increased virus-specific T response, including higher IFNγ+/CD8 + lymphocyte production in mice. When these vaccines were tested in calves, antibody titers reached an Expected Percentage of Protection (EPP) above 90 % in the case of the VLPs-ISPA and VLPs-ISA 206 vaccines, while, in the VLPs group, EPP reached 25 %. IFNγ levels secreted by mononuclear cells of VLP-ISPA-vaccinated cattle were significantly higher than in the VLPs group. Overall, the results demonstrate that VLPs-ISPA or VLPs-ISA 206 are promising formulations for the development of a novel FMD vaccine.

Neutralizing Antibody Responses Induced by HIV-1 Envelope Glycoprotein SOSIP Trimers Derived from Elite Neutralizers

The induction of broadly neutralizing antibodies (bNAbs) is a major goal in vaccine research. HIV-1-infected individuals that develop exceptionally strong bNAb responses, termed elite neutralizers, can inform vaccine design by providing blueprints for the induction of similar bNAb responses. We describe a new recombinant native-like envelope glycoprotein (Env) SOSIP trimer, termed AMC009, based on the viral founder sequences of an elite neutralizer. The subtype B AMC009 SOSIP protein formed stable native-like trimers that displayed multiple bNAb epitopes. Overall, its structure at 4.3-Å resolution was similar to that of BG505 SOSIP.664. The AMC009 trimer resembled one from a second elite neutralizer, AMC011, in having a dense and complete glycan shield. When tested as immunogens in rabbits, the AMC009 trimers did not induce autologous neutralizing antibody (NAb) responses efficiently while the AMC011 trimers did so very weakly, outcomes that may reflect the completeness of their glycan shields. The AMC011 trimer induced antibodies that occasionally cross-neutralized heterologous tier 2 viruses, sometimes at high titer. Cross-neutralizing antibodies were more frequently elicited by a trivalent combination of AMC008, AMC009, and AMC011 trimers, all derived from subtype B viruses. Each of these three individual trimers could deplete the NAb activity from the rabbit sera. Mapping the polyclonal sera by electron microscopy revealed that antibodies of multiple specificities could bind to sites on both autologous and heterologous trimers. These results advance our understanding of how to use Env trimers in multivalent vaccination regimens and the immunogenicity of trimers derived from elite neutralizers.IMPORTANCE Elite neutralizers, i.e., individuals who developed unusually broad and potent neutralizing antibody responses, might serve as blueprints for HIV-1 vaccine design. Here, we studied the immunogenicity of native-like recombinant envelope glycoprotein (Env) trimers based on viral sequences from elite neutralizers. While immunization with single trimers from elite neutralization did not recapitulate the breadth and potency of neutralization observed in these infected individuals, a combination of three subtype B Env trimers from elite neutralizers resulted in some neutralization breadth within subtype B viruses. These results should guide future efforts to design vaccines to induce broadly neutralizing antibodies.

Development of a subcutaneous ear implant to deliver an anaplasmosis vaccine to dairy steers

Bovine anaplasmosis is the most prevalent tick-transmitted disease of cattle worldwide and a major obstacle to profitable beef production. Use of chlortetracycline-medicated feed to control active anaplasmosis infections during the vector season has raised concerns about the potential emergence of antimicrobial resistance in bacteria that may pose a risk to human health. Furthermore, the absence of effectiveness data for a commercially available, conditionally licensed anaplasmosis vaccine is a major impediment to implementing anaplasmosis control programs. The primary objective of this study was to develop a single-dose vaccine delivery platform to produce long-lasting protective immunity against anaplasmosis infections. Twelve Holstein steers, aged 11 to 12 wk, were administered a novel 3-stage, single-dose vaccine against Anaplasma marginale, a major surface protein 1a. The vaccine consisted of a soluble vaccine administered subcutaneously (s.c.) for immune priming, a vaccine depot of a biodegradable polyanhydride rod with intermediate slow release of the vaccine for boosting immune response, and an immune-isolated vaccine platform for extended antigen release (VPEAR implant) deposited s.c. in the ear. Six calves were randomly assigned to 2 vaccine constructs (n = 3) that featured rods and implants containing a combination of 2 different adjuvants, diethylaminoethyl (DEAE)-Dextran and Quil-A (Group A). The remaining 6 calves were randomly assigned to 2 vaccine constructs (n = 3) that featured rods and implants containing the same adjuvant (either DEAE-Dextran or Quil A) (Group B). Twenty-one months post-implantation, calves were challenged intravenously with A. marginale stabilate and were monitored weekly for signs of fever, decreased packed cell volume (PCV) and bacteremia. Data were analyzed using a mixed-effects model and chi-squared tests (SAS v9.04.01, SAS Institute, Cary, NC). Calves in Group A had higher PCV than calves in Group B (P = 0.006) at day 35 post-infection. Calves in Group A were less likely to require antibiotic intervention compared with calves in Group B (P = 0.014). Results indicate that calves exhibited diminished clinical signs of anaplasmosis when antigen was delivered with a combination of adjuvants as opposed to a single adjuvant. This demonstrates the feasibility of providing long-lasting protection against clinical bovine anaplasmosis infections using a subcutaneous ear implant vaccine construct.

A New Cage-Like Particle Adjuvant Enhances Protection of Foot-and-Mouth Disease Vaccine

Foot-and-Mouth Disease (FMD) is an acute viral disease that causes important economy losses. Vaccines with new low-cost adjuvants that stimulate protective immune responses are needed and can be assayed in a mouse model to predict their effectiveness in cattle. Immunostimulant Particle Adjuvant (ISPA), also known as cage-like particle adjuvant, consisting of lipid boxes of dipalmitoyl-phosphatidylcholine, cholesterol, sterylamine, alpha-tocopherol, and QuilA saponin, was shown to enhance protection of a recombinant vaccine against Trypanosoma cruzi in a mouse model. Thus, in the present work, we studied the effects on the magnitude and type of immunity elicited in mice and cattle in response to a vaccine based on inactivated FMD virus (iFMDV) formulated with ISPA. It was demonstrated that iFMDV–ISPA induced protection in mice against challenge and elicited a specific antibody response in sera, characterized by a balanced Th1/Th2 profile. In cattle, the antibody titers reached corresponded to an expected percentage of protection (EPP) higher than 80%. EPP calculates the probability that livestock would be protected against a 10,000 bovine infectious doses challenge after vaccination. Moreover, in comparison with the non-adjuvanted iFMDV vaccine, iFMDV–ISPA elicited an increased specific T-cell response against the virus, including higher interferon gamma (IFNγ)+/CD8+ lymphocyte production in cattle. In this work, we report for first time that an inactivated FMDV serotype A vaccine adjuvanted with ISPA is capable of inducing protection against challenge in a murine model and of improving the specific immune responses against the virus in cattle.

Foamy matters: an update on Quillaja saponins and their use as immunoadjuvants

Immunoadjuvant Quillaja spp. tree saponins stimulate both cellular and humoral responses, significantly widening vaccine target pathogen spectra. Host toxicity of specific saponins, fractions and extracts may be rather low and further reduced using lipid-based delivery systems. Saponins contain a hydrophobic central aglycone decorated with several sugar residues, posing a challenge for viable chemical synthesis. These, however, may provide simpler analogs. Saponin chemistry affords characteristic interactions with cell membranes, which are essential for its mechanism of action. Natural sources include Quillaja saponaria barks and, more recently, Quillaja brasiliensis leaves. Sustainable large-scale supply can use young plants grown in clonal gardens and elicitation treatments. Quillaja genomic studies will most likely buttress future synthetic biology-based saponin production efforts.

Induction of Plasmodium-Specific Immune Responses Using Liposome-Based Vaccines

In the development of vaccines, the ability to initiate both innate and subsequent adaptive immune responses need to be considered. Live attenuated vaccines achieve this naturally, while inactivated and sub-unit vaccines generally require additional help provided through delivery systems and/or adjuvants. Liposomes present an attractive adjuvant/delivery system for antigens. Here, we review the key aspects of immunity against Plasmodium parasites, liposome design considerations and their current application in the development of a malaria vaccine.

Innate Immune Stimulation in Cancer Therapy

The innate immune system has evolved as a first line of defense against invading pathogens and acts via classes of germline-encoded receptor systems to respond with proinflammatory cytokines. Innate immune cells, predominantly cells of the myeloid compartment, are capable of providing a potent basis for boosting adaptive immunity in malignant diseases. The authors review their current understanding of the molecular mechanisms whereby innate pattern recognition receptors participate in immunosurveillance of cancer cells. They discuss how innate effector mechanisms are currently being targeted pharmacologically and how improved understanding of the biology of these pathways is leading to novel immunotherapies of cancer.

Quillaja brasiliensis saponin-based nanoparticulate adjuvants are capable of triggering early immune responses

Commercially available saponins are extracted from Quillaja saponaria barks, being Quil A® the most widely used. Nanoparticulate immunostimulating complexes (ISCOMs or ISCOMATRIX) formulated with these, are able to stimulate strong humoral and cellular immune responses. Recently, we formulated novel ISCOMs replacing QuilA® by QB-90 (IQB-90), a Quillaja brasiliensis leaf-extracted saponin fraction, and reported that IQB-90 improved antigen uptake, and induced systemic and mucosal antibody production, and T-cell responses. However, its mechanism of action remains unclear. In this study we provide a deeper insight into the immune stimulatory properties of QB-90 and ISCOMATRIX-like based on this fraction (IMXQB-90). We show herein that, when used as a viral vaccine adjuvant, QB-90 promotes an "immunocompetent environment". In addition, QB-90 and IMXQB-90 induce immune-cells recruitment at draining-lymph nodes and spleen. Subsequently, we prove that QB-90 or IMXQB-90 stimulated dendritic cells secret IL-1β by mechanisms involving Caspase-1/11 and MyD88 pathways, implying canonical inflammasome activation. Finally, both formulations induce a change in the expression of cytokines and chemokines coding genes, many of which are up-regulated. Findings reported here provide important insights into the molecular and cellular mechanisms underlying the adjuvant activity of Q. brasiliensis leaf-saponins and its respective nanoparticles.

Trans-sialidase overcomes many antigens to be used as a vaccine candidate against Trypanosoma cruzi

AIM

The development of vaccines against Trypanosoma cruzi remains in an exploratory stage. Despite several antigen candidates have been evaluated, a comparison among the performance of the immunogens cannot be carried out because the available reports differ in formulations and infection model. In this work, we compared the protective capacity of seven T. cruzi antigens in the same model of five new antigens and two well-established candidates. Materials & methods: We evaluated highly immunogenic proteins that contain tandem repeats (FRA [flagelar repetitive protein], Tc3, Tc6); enzymes involved in metabolic pathways critical for parasite survival (cytosolic tryparedoxin peroxidase and tryparedoxin peroxidase); and enzymes involved in parasite invasion (trans-sialidase [TS] and cruzipain). All these antigens were formulated with Freund's adjuvant and protection against the parasite infection was assessed in BALB/c mice.

RESULTS

Tc3, cytosolic tryparedoxin peroxidase, cruzipain and TS showed the best outcome after infection in survival level and parasitemia. According to these data, these groups were also assessed using the ISCOMATRIX™ adjuvant which is being used in clinical trials.

CONCLUSION

Taken together, our results showed that the TS overcomes the performance of other antigens when the same model is employed, confirming that TS is a promising antigen that could be used as a vaccine against T. cruzi.

Development and assessment of a new cage-like particle adjuvant

OBJECTIVES

To obtain and assess stable cage-like particles with low surface charge density, which can be prepared using a standardized, economic and scalable method.

METHODS

To form these nanoparticles, the lipid composition and proportion as well the method were modified in relation to cage-like particles previously described elsewhere. Bovine albumin was used to compare ISPA performance with that of other adjuvants in mice and to assess stability. Adjuvant efficacy was analysed using a mouse model of Trypanosoma cruzi infection, which shows protection against an intracellular infection that needs a strong cellular response.

KEY FINDINGS

The new particles were better in terms of level, kinetics and profile of humoral responses than Freund Adjuvant, aluminium hydroxide and Montanide TM ISA 206; they also tended to improve ISCOMATRIX^™ performance. Particle size and adjuvant performance were conserved during the 6-month period assessed after preparation. In the model of Trypanosoma cruzi infection, mice immunized with ISPA and trans-sialidase developed high protection.

CONCLUSIONS

The obtained nanoparticles were stable and outperformed the other assessed adjuvants in joining together the capacity of most adjuvants to enhance the immune response against specific antigen, to reduce the number of doses, to homogenize the response between individuals and to reach a balanced TH1/TH2 response.

Translational nanoparticle engineering for cancer vaccines

Conventional cancer treatments remain insufficient to treat many therapy-resistant tumors.¹ Cancer vaccines attempt to overcome this resistance by activating the patient's immune system to eliminate tumor cells without the toxicity of systemic chemotherapy and radiation. Nanoparticles (NPs) are promising as customizable, immunostimulatory carriers to protect and deliver antigen. Although many NP vaccines have been investigated in preclinical settings, a few have advanced into clinical application, and still fewer have demonstrated clinical benefit. This review incorporates observations from NP vaccines that have been evaluated in early phase clinical trials to make recommendations for the next generation of NP-based cancer vaccines.

The CD8⁺ T Cell-Mediated Immunity Induced by HPV-E6 Uploaded in Engineered Exosomes Is Improved by ISCOMATRIXTM Adjuvant

We recently described the induction of an efficient CD8⁺ T cell-mediated immune response against a tumor-associated antigen (TAA) uploaded in engineered exosomes used as an immunogen delivery tool. This immune response cleared tumor cells inoculated after immunization, and controlled the growth of tumors implanted before immunization. We looked for new protocols aimed at increasing the CD8⁺ T cell specific response to the antigen uploaded in engineered exosomes, assuming that an optimized CD8⁺ T cell immune response would correlate with a more effective depletion of tumor cells in the therapeutic setting. By considering HPV-E6 as a model of TAA, we found that the in vitro co-administration of engineered exosomes and ISCOMATRIX^TM adjuvant, i.e., an adjuvant composed of purified ISCOPREP^TM saponin, cholesterol, and phospholipids, led to a stronger antigen cross-presentation in both B- lymphoblastoid cell lines ( and monocyte-derived immature dendritic cells compared with that induced by the exosomes alone. Consistently, the co-inoculation in mice of ISCOMATRIX^TM adjuvant and engineered exosomes induced a significant increase of TAA-specific CD8⁺ T cells compared to mice immunized with the exosomes alone. This result holds promise for effective usage of exosomes as well as alternative nanovesicles in anti-tumor therapeutic approaches.

Saponin-based adjuvants induce cross-presentation in dendritic cells by intracellular lipid body formation

Saponin-based adjuvants (SBAs) are being used in animal and human (cancer) vaccines, as they induce protective cellular immunity. Their adjuvant potency is a factor of inflammasome activation and enhanced antigen cross-presentation by dendritic cells (DCs), but how antigen cross-presentation is induced is not clear. Here we show that SBAs uniquely induce intracellular lipid bodies (LBs) in the CD11b+ DC subset in vitro and in vivo. Using genetic and pharmacological interference in models for vaccination and in situ tumour ablation, we demonstrate that LB induction is causally related to the saponin-dependent increase in cross-presentation and T-cell activation. These findings link adjuvant activity to LB formation, aid the application of SBAs as a cancer vaccine component, and will stimulate development of new adjuvants enhancing T-cell-mediated immunity.

Saponin-based adjuvants are being explored as vaccine components as they induce high levels of antigen cross-presentation, but it is unknown how. Here the authors show that these adjuvants enhance cross-presentation by driving production of lipid bodies inside CD11b dendritic cells.

Meta-Analysis on Randomized Controlled Trials of Vaccines with QS-21 or ISCOMATRIX Adjuvant: Safety and Tolerability

BACKGROUND AND OBJECTIVES

QS-21 shows in vitro hemolytic effect and causes side effects in vivo. New saponin adjuvant formulations with better toxicity profiles are needed. This study aims to evaluate the safety and tolerability of QS-21 and the improved saponin adjuvants (ISCOM, ISCOMATRIX and Matrix-M™) from vaccine trials.

METHODS

A systematic literature search was conducted from MEDLINE, EMBASE, Cochrane library and Clinicaltrials.gov. We selected for the meta-analysis randomized controlled trials (RCTs) of vaccines adjuvanted with QS-21, ISCOM, ISCOMATRIX or Matrix-M™, which included a placebo control group and reported safety outcomes. Pooled risk ratios (RRs) and their 95% confidence intervals (CIs) were calculated using a random-effects model. Jadad scale was used to assess the study quality.

RESULTS

Nine RCTs were eligible for the meta-analysis: six trials on QS-21-adjuvanted vaccines and three trials on ISCOMATRIX-adjuvanted, with 907 patients in total. There were no studies on ISCOM or Matrix-M™ adjuvanted vaccines matching the inclusion criteria. Meta-analysis identified an increased risk for diarrhea in patients receiving QS21-adjuvanted vaccines (RR 2.55, 95% CI 1.04-6.24). No increase in the incidence of the reported systemic AEs was observed for ISCOMATRIX-adjuvanted vaccines. QS-21- and ISCOMATRIX-adjuvanted vaccines caused a significantly higher incidence of injection site pain (RR 4.11, 95% CI 1.10-15.35 and RR 2.55, 95% CI 1.41-4.59, respectively). ISCOMATRIX-adjuvanted vaccines also increased the incidence of injection site swelling (RR 3.43, 95% CI 1.08-10.97).

CONCLUSIONS

Our findings suggest that vaccines adjuvanted with either QS-21 or ISCOMATRIX posed no specific safety concern. Furthermore, our results indicate that the use of ISCOMATRIX enables a better systemic tolerability profile when compared to the use of QS-21. However, no better local tolerance was observed for ISCOMATRIX-adjuvanted vaccines in immunized non-healthy subjects. This meta-analysis is limited by the relatively small number of individuals recruited in the included trials, especially in the control groups.

Novel ISCOMs from Quillaja brasiliensis saponins induce mucosal and systemic antibody production, T-cell responses and improved antigen uptake

In the last decades, significant efforts have been dedicated to the search for novel vaccine adjuvants. In this regard, saponins and its formulations as "immunostimulating complexes" (ISCOMs) have shown to be capable of stimulating potent humoral and cellular immune responses, enhanced cytokine production and activation of cytotoxic T cells. The immunological activity of ISCOMs formulated with a saponin fraction extracted from Quillaja brasiliensis (QB-90 fraction) as an alternative to classical ISCOMs based on Quil A(®) (IQA) is presented here. The ISCOMs prepared with QB-90, named IQB-90, typically consist of 40-50 nm, spherical, cage-like particles, built up by QB-90, cholesterol, phospholipids and antigen (ovalbumin, OVA). These nanoparticles were efficiently uptaken in vitro by murine bone marrow-derived dendritic cells. Subcutaneously inoculated IQB-90 induced strong serum antibody responses encompassing specific IgG1 and IgG2a, robust DTH reactions, significant T cell proliferation and increases in Th1 (IFN-γ and IL-2) cytokine responses. Intranasally delivered IQB-90 elicited serum IgG and IgG1, and mucosal IgA responses at distal systemic sites (nasal passages, large intestine and vaginal lumen). These results indicate that IQB-90 is a promising alternative to classic ISCOMs as vaccine adjuvants, capable of enhancing humoral and cellular immunity to levels comparable to those induced by ISCOMs manufactured with Quillaja saponaria saponins.

Presenting native-like HIV-1 envelope trimers on ferritin nanoparticles improves their immunogenicity

Background

Presenting vaccine antigens in particulate form can improve their immunogenicity by enhancing B cell activation.

Findings

We describe ferritin-based protein nanoparticles that display multiple copies of native-like HIV-1 envelope glycoprotein trimers (BG505 SOSIP.664). Trimer-bearing nanoparticles were significantly more immunogenic than trimers in both mice and rabbits. Furthermore, rabbits immunized with the trimer-bearing nanoparticles induced significantly higher neutralizing antibody responses against most tier 1A viruses, and higher responses (but not significantly), to several tier 1B viruses and the autologous tier 2 virus than when the same trimers were delivered as soluble proteins.

Conclusions

This or other nanoparticle designs may be practical ways to improve the immunogenicity of envelope glycoprotein trimers.

HIV-1 VACCINES. HIV-1 neutralizing antibodies induced by native-like envelope trimers

A challenge for HIV-1 immunogen design is the difficulty of inducing neutralizing antibodies (NAbs) against neutralization-resistant (tier 2) viruses that dominate human transmissions. We show that a soluble recombinant HIV-1 envelope glycoprotein trimer that adopts a native conformation, BG505 SOSIP.664, induced NAbs potently against the sequence-matched tier 2 virus in rabbits and similar but weaker responses in macaques. The trimer also consistently induced cross-reactive NAbs against more sensitive (tier 1) viruses. Tier 2 NAbs recognized conformational epitopes that differed between animals and in some cases overlapped with those recognized by broadly neutralizing antibodies (bNAbs), whereas tier 1 responses targeted linear V3 epitopes. A second trimer, B41 SOSIP.664, also induced a strong autologous tier 2 NAb response in rabbits. Thus, native-like trimers represent a promising starting point for the development of HIV-1 vaccines aimed at inducing bNAbs.

ISCOMATRIX™ adjuvant promotes epitope spreading and antibody affinity maturation of influenza A H7N9 virus like particle vaccine that correlate with virus neutralization in humans

In a previously reported phase I clinical trial, subjects vaccinated with two doses of an unadjuvanted H7N9 virus like particle (VLP) vaccine responded poorly (15.6% seroconversion rates with 45μg hemagglutinin (HA) dose). In contrast, 80.6% of subjects receiving H7N9 VLP vaccine (5μg HA) with ISCOMATRIX™ adjuvant developed hemagglutination-inhibition (HI) responses. To better understand the role of adjuvant, complete antibody epitope repertoires of post-vaccination sera were investigated using Whole Genome Fragment Phage Display Library (GFPDL). In addition, antibody affinity maturation following vaccination was measured against HA1 and HA2 antigenic domains using real time Surface Plasmon Resonance (SPR) based kinetic assays. Unadjuvanted H7N9-VLP vaccine generated primarily antibodies targeting the C-terminus of the HA1 domain, predicted to be mostly buried on the native HA spikes, while adjuvanted VLP vaccine generated antibodies against large epitopes in the HA1 spanning the receptor binding domain (RBD). SPR analysis using a functional H7-HA1 domain demonstrated that sera from adjuvanted H7N9-VLP vaccine induced higher total binding antibodies and significantly higher antibody affinity maturation to HA1 compared to sera from unadjuvanted vaccine. Total antibody binding and affinity to the HA1 (but not HA2) domain correlated with HI and neutralization titers. This study demonstrates that ISCOMATRIX™ adjuvanted vaccine promotes higher quality antibody immune response against avian influenza in naïve humans.

Recombinant virus-like particles elicit protective immunity against avian influenza A(H7N9) virus infection in ferrets

In March 2013, diagnosis of the first reported case of human infection with a novel avian-origin influenza A(H7N9) virus occurred in eastern China. Most human cases have resulted in severe respiratory illness and, in some instances, death. Currently there are no licensed vaccines against H7N9 virus, which continues to cause sporadic human infections. Recombinant virus-like particles (VLPs) have been previously shown to be safe and effective vaccines for influenza. In this study, we evaluated the immunogenicity and protective efficacy of a H7N9 VLP vaccine in the ferret challenge model. Purified recombinant H7N9 VLPs morphologically resembled influenza virions and elicited high-titer serum hemagglutination inhibition (HI) and neutralizing antibodies specific for A/Anhui/1/2013 (H7N9) virus. H7N9 VLP-immunized ferrets subsequently challenged with homologous virus displayed reductions in fever, weight loss, and virus shedding compared to these parameters in unimmunized control ferrets. H7N9 VLP was also effective in protecting against lung and tracheal infection. The addition of either ISCOMATRIX or Matrix-M1 adjuvant improved immunogenicity and protection of the VLP vaccine against H7N9 virus. These results provide support for the development of a safe and effective human VLP vaccine with potent adjuvants against avian influenza H7N9 virus with pandemic potential.

Slc15a4 function is required for intact class switch recombination to IgG2c in response to TLR9 stimulation

Signalling through Toll-like receptors (TLRs) by endogenous components of viruses or bacteria can promote antibody (Ab) isotype switching to IgG2a/c. Multiple cell types are capable of responding to TLR stimulation in vivo and the processes underlying TLR-induced Ab isotype switching are not fully defined. Here, we used feeble mice, which are deficient in the peptide/histidine transporter solute carrier family 15 member 4 (Slc15a4), and fail to produce cytokines including interferon alpha (IFNα) in response to TLR9 stimulation, to study Ab isotype switching to IgG2c in response to vaccination. We demonstrate that the production of IgG2c in response to CpGA-adjuvanted vaccines was severely reduced in feeble mice, while a more subtle defect was observed for CpGB. The reduced IgG2c production in feeble could not be ascribed to defective plasmacytoid dendritic cell (pDC) responses alone as we found that splenic cDCs and B cells from feeble mice were also defective in response to TLR9 ligation ex vivo. We conclude that Slc15a4 is required for intact function of TLR9-expressing cells and for effective Ab isotype switching to IgG2c in response to CpG-adjuvanted vaccines.

Inflammasome-dependent and -independent IL-18 production mediates immunity to the ISCOMATRIX adjuvant

Adjuvants are an essential component of modern vaccines and used for their ability to elicit immunity to coadministered Ags. Many adjuvants in clinical development are particulates, but how they drive innate and adaptive immune responses remains poorly understood. Studies have shown that a number of vaccine adjuvants activate inflammasome pathways in isolated APCs. However, the contribution of inflammasome activation to vaccine-mediated immunity in vivo remains controversial. In this study, we evaluated immune cell responses to the ISCOMATRIX adjuvant (IMX) in mice. Like other particulate vaccine adjuvants, IMX potently activated the NALP-3-ASC-Caspase-1 inflammasome in APCs, leading to IL-1β and IL-18 production. The IL-18R pathway, but not IL-1R, was required for early innate and subsequent cellular immune responses to a model IMX vaccine. APCs directly exposed to IMX underwent an endosome-mediated cell-death response, which we propose initiates inflammatory events locally at the injection site. Importantly, both inflammasome-related and -unrelated pathways contributed to IL-18 dependence in vivo following IMX administration. TNF-α provided a physiological priming signal for inflammasome-dependent IL-18 production by APCs, which correlated with reduced vaccine-mediated immune cell responses in TNF-α- or TNFR-deficient mice. Taken together, our findings highlight an important disconnect between the mechanisms of vaccine adjuvant action in vitro versus in vivo.

Coadministration of polyinosinic:polycytidylic acid and immunostimulatory complexes modifies antigen processing in dendritic cell subsets and enhances HIV gag-specific T cell immunity

Currently approved adjuvants induce protective Ab responses but are more limited for generating cellular immunity. In this study, we assessed the effect of combining two adjuvants with distinct mechanisms of action on their ability to prime T cells: the TLR3 ligand, polyinosinic:polycytidylic acid (poly I:C), and immunostimulatory complexes (ISCOMs). Each adjuvant was administered alone or together with HIV Gag protein (Gag), and the magnitude, quality, and phenotype of Gag-specific T cell responses were assessed. For CD8 T cells, all adjuvants induced a comparable response magnitude, but combining poly I:C with ISCOMs induced a high frequency of CD127(+), IL-2-producing cells with decreased expression of Tbet compared with either adjuvant alone. For CD4 T cells, combining poly I:C and ISCOMs increased the frequency of multifunctional cells, producing IFN-γ, IL-2, and TNF, and the total magnitude of the response compared with either adjuvant alone. CD8 or CD4 T cell responses induced by both adjuvants mediated protection against Gag-expressing Listeria monocytogenes or vaccinia viral infections. Poly I:C and ISCOMs can alter Ag uptake and/or processing, and we therefore used fluorescently labeled HIV Gag and DQ-OVA to assess these mechanisms, respectively, in multiple dendritic cell subsets. Poly I:C promoted uptake and retention of Ag, whereas ISCOMs enhanced Ag degradation. Combining poly I:C and ISCOMs caused substantial death of dendritic cells but persistence of degraded Ag. These data illustrate how combining adjuvants, such as poly I:C and ISCOMs, that modulate Ag processing and have potent innate activity, can enhance the magnitude, quality, and phenotype of T cell immunity.

Serum cytokine profiles associated with specific adjuvants used in a DNA prime-protein boost vaccination strategy

In recent years, heterologous prime-boost vaccines have been demonstrated to be an effective strategy for generating protective immunity, consisting of both humoral and cell-mediated immune responses against a variety of pathogens including HIV-1. Previous reports of preclinical and clinical studies have shown the enhanced immunogenicity of viral vector or DNA vaccination followed by heterologous protein boost, compared to using either prime or boost components alone. With such approaches, the selection of an adjuvant for inclusion in the protein boost component is expected to impact the immunogenicity and safety of a vaccine. In this study, we examined in a mouse model the serum cytokine and chemokine profiles for several candidate adjuvants: QS-21, Al(OH)3, monophosphoryl lipid A (MPLA) and ISCOMATRIX™ adjuvant, in the context of a previously tested pentavalent HIV-1 Env DNA prime-protein boost formulation, DP6-001. Our data revealed that the candidate adjuvants in the context of the DP6-001 formulation are characterized by unique serum cytokine and chemokine profiles. Such information will provide valuable guidance in the selection of an adjuvant for future AIDS vaccine development, with the ultimate goal of enhancing immunogenicity while minimizing reactogenicity associated with the use of an adjuvant. More significantly, results reported here will add to the knowledge on how to include an adjuvant in the context of a heterologous prime-protein boost vaccination strategy in general.

Nonreplicating vaccines can protect african green monkeys from the memphis 37 strain of respiratory syncytial virus

BACKGROUND

We evaluated the immunological responses of African green monkeys immunized with multiple F and G protein-based vaccines and assessed protection against the Memphis 37 strain of respiratory syncytial virus (RSV).

METHODS

Monkeys were immunized with F and G proteins adjuvanted with immunostimulatory (CpG) oligodeoxyribonucleotides admixed with either Alhydrogel or ISCOMATRIX adjuvant. Delivery of F and G proteins via replication incompetent recombinant vesicular stomatitis viruses (VSVs) and human adenoviruses was also evaluated. Mucosally or parenterally administered recombinant adenoviruses were used in prime-boost regimens with adjuvanted proteins or recombinant DNA.

RESULTS

Animals primed by intranasal delivery of recombinant adenoviruses, and boosted by intramuscular injection of adjuvanted F and G proteins, developed neutralizing antibodies and F/G protein-specific T cells and were protected from RSV infection. Intramuscular injections of Alhydrogel (plus CpG) adjuvanted F and G proteins reduced peak viral loads in the lungs of challenged monkeys. Granulocyte numbers were not significantly elevated, relative to controls, in postchallenge bronchoalveolar lavage samples from vaccinated animals.

CONCLUSIONS

This study has validated the use of RSV (Memphis 37) in an African green monkey model of intranasal infection and identified nonreplicating vaccines capable of eliciting protection in this higher species challenge model.

CpG ODN and ISCOMATRIX adjuvant: a synergistic adjuvant combination inducing strong T-Cell IFN-γ responses

For the induction of robust humoral and cellular immune responses, a strong rationale exists to use vaccine-adjuvant combinations possessing both immune modulatory and enhanced delivery capabilities. Herein, we evaluated the combination of 2 different adjuvants, a TLR9 agonist, composed of synthetic oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs (CpG), and ISCOMATRIX adjuvant (ISCOMATRIX), composed of saponin, phospholipid, and cholesterol, which possesses both immunostimulatory and delivery properties. While both individual adjuvants have been shown effective in numerous preclinical and clinical studies, it is likely that for optimal adjuvant activity a combined adjuvant approach will be necessary. Herein, using three different antigens, namely, hepatitis B surface antigen (HBsAg), ovalbumin (OVA), and influenza A haemagglutinin antigen (HA), we show in mice that some adjuvant effects of CpG and ISCOMATRIX are further enhanced if they are used in combination. In particular, with all three antigens, IFN-γ levels were greatly increased with the CpG/ISCOMATRIX combination. The ability of the CpG/ISCOMATRIX combination to induce antitumor responses when administered with OVA following administration to mice of a highly metastatic OVA-secreting tumor cell line (B16-OVA melanoma) was also demonstrated. Thus the CpG/ISCOMATRIX combination may prove to be a valuable tool in the development of novel or improved vaccines.

Global transcriptional response to ISCOM-Matrix adjuvant at the site of administration and in the draining lymph node early after intramuscular injection in pigs

ISCOM vaccines induce a balanced Th1/Th2 response, long-lasting antibody responses and cytotoxic T lymphocytes. The mode of action for the adjuvant component, the ISCOM-Matrix, is known to some extent but questions remain regarding its mechanism of action. The Affymetrix GeneChip® Porcine Genome Array was applied to study the global transcriptional response to ISCOM-Matrix in pigs at the injection site and in the draining lymph node 24h after i.m. injection. Gene enrichment analysis revealed inflammation, innate immunity and antigen processing to be central in the ISCOM-Matrix response. At the injection site, 594 genes were differentially expressed, including up-regulation of the cytokines osteopontin (SPP1), IL-10 and IL-18 and the chemokines CCL2, CCL19 and CXCL16. Of the 362 genes differentially expressed in the lymph node, IL-1β and CXCL11 were up-regulated whereas IL18, CCL15 and CXCL12 were down-regulated. ISCOM-Matrix also modulated genes for pattern recognition receptors at the injection site (TLR2, TLR4, MRC1, PTX3, LGALS3) and in the lymph node (TLR4, RIG-I, MDA5, OAS1, EIF2AK2, LGALS3). A high proportion of up-regulated interferon-regulated genes indicated an interferon response. Thus, several genes, genetic pathways and biological processes were identified that are likely to shape the early immune response elicited by ISCOM-based vaccines.

Mechanisms of environmental influence on human autoimmunity: a National Institute of Environmental Health Sciences expert panel workshop

The mechanisms leading to autoimmune diseases remain largely unknown despite numerous lines of experimental inquiry and epidemiological evidence. The growing number of genome-wide association studies and the largely incomplete concordance for autoimmune diseases in monozygotic twins support the role of the environment (including infectious agents and chemicals) in the breakdown of tolerance leading to autoimmunity via numerous mechanisms. The present article reviews the major theories on the mechanisms of the environmental influence on autoimmunity by addressing the different degrees of confidence that characterize our knowledge. The theories discussed herein include (i) the role of innate immunity mediated by toll-like receptors in triggering the autoimmune adaptive response characterizing the observed pathology; (ii) changes in spleen marginal zone B cells in autoantibody production with particular focus on the B10 subpopulation; (iii) Th17 cell differentiation and T regulatory cells in the aryl hydrocarbon receptor model; (iv) self antigen changes induced by chemical and infectious agents which could break tolerance by post-translational modifications and molecular mimicry; and finally (v) epigenetic changes, particularly DNA methylation, that are induced by environmental stimuli and may contribute to autoimmunity initiation. We are convinced that these working hypotheses, in most cases supported by solid evidence, should be viewed in parallel with animal models and epidemiological observations to provide a comprehensive picture of the environmental causes of autoimmune diseases.

Off-the-shelf adenoviral-mediated immunotherapy via bicistronic expression of tumor antigen and iMyD88/CD40 adjuvant

Recent modest successes in ex vivo dendritic cell (DC) immunotherapy have motivated continued innovation in the area of DC manipulation and activation. Although ex vivo vaccine approaches continue to be proving grounds for new DC manipulation techniques, the intrinsic limits of ex vivo therapy, including high cost, minimal standardization, cumbersome delivery, and poor accessibility, incentivizes the development of vaccines compatible with in vivo DC targeting. We describe here a method to co-deliver both tumor-specific antigen (TSA) and an iMyD88/CD40 adjuvant (iMC), to DCs that combines toll-like receptor (TLR) and CD40 signaling. In this study, we demonstrate that simple TSA delivery via adenoviral vectors results in strong antitumor immunity. Addition of iMC delivered in a separate vector is insufficient to enhance this effect. However, when delivered simultaneously with TSA in a single bicistronic vector (BV), iMC is able to significantly enhance antigen-specific cytotoxic T-cell (CTL) responses and inhibit established tumor growth. This study demonstrates the spatial-temporal importance of concurrent DC activation and TSA presentation. Further, it demonstrates the feasibility of in vivo molecular enhancement of DCs necessary for effective antitumor immune responses.

Long-term antibody and immune memory response induced by pulmonary delivery of the influenza Iscomatrix vaccine

Pulmonary delivery of an influenza Iscomatrix adjuvant vaccine induces a strong systemic and mucosal antibody response. Since an influenza vaccine needs to induce immunological memory that lasts at least 1 year for utility in humans, we examined the longevity of the immune response induced by such a pulmonary vaccination, with and without antigen challenge. Sheep were vaccinated in the deep lung with an influenza Iscomatrix vaccine, and serum and lung antibody levels were quantified for up to 1 year. The immune memory response to these vaccinations was determined following antigen challenge via lung delivery of influenza antigen at 6 months and 1 year postvaccination. Pulmonary vaccination of sheep with the influenza Iscomatrix vaccine induced antigen-specific antibodies in both sera and lungs that were detectable until 6 months postimmunization. Importantly, a memory recall response following antigenic challenge was detected at 12 months post-lung vaccination, including the induction of functional antibodies with hemagglutination inhibition activity. Pulmonary delivery of an influenza Iscomatrix vaccine induces a long-lived influenza virus-specific antibody and memory response of suitable length for annual vaccination against influenza.

Melanoma vaccines: developments over the past 10 years

Decades of preclinical evaluation and clinical trials into melanoma vaccines have yielded spectacular progress in our understanding of melanoma antigens and the immune mechanisms of tumor rejection. Key insights and the results of their clinical evaluation are reviewed in this article. Unfortunately, durable clinical benefit following vaccination remains uncommon. Two recent clinical advances that will impact on melanoma vaccine development are trials with inhibitors of CTLA-4 and oncogenic BRAF. Long-term therapeutic control of melanoma will require integration of specific active immunotherapy with these emerging successful therapies from the disparate fields of immune regulation and signal transduction.

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.

An overview on the field of micro- and nanotechnologies for synthetic Peptide-based vaccines

The development of synthetic peptide-based vaccines has many advantages in comparison with vaccines based on live attenuated organisms, inactivated or killed organism, or toxins. Peptide-based vaccines cannot revert to a virulent form, allow a better conservation, and are produced more easily and safely. However, they generate a weaker immune response than other vaccines, and the inclusion of adjuvants and/or the use of vaccine delivery systems is almost always needed. Among vaccine delivery systems, micro- and nanoparticulated ones are attractive, because their particulate nature can increase cross-presentation of the peptide. In addition, they can be passively or actively targeted to antigen presenting cells. Furthermore, particulate adjuvants are able to directly activate innate immune system in vivo. Here, we summarize micro- and nanoparticulated vaccine delivery systems used in the field of synthetic peptide-based vaccines as well as strategies to increase their immunogenicity.

Vaccine adjuvants: putting innate immunity to work

Adjuvants enhance immunity to vaccines and experimental antigens by a variety of mechanisms. In the past decade, many receptors and signaling pathways in the innate immune system have been defined and these innate responses strongly influence the adaptive immune response. The focus of this review is to delineate the innate mechanisms by which adjuvants mediate their effects. We highlight how adjuvants can be used to influence the magnitude and alter the quality of the adaptive response in order to provide maximum protection against specific pathogens. Despite the impressive success of currently approved adjuvants for generating immunity to viral and bacterial infections, there remains a need for improved adjuvants that enhance protective antibody responses, especially in populations that respond poorly to current vaccines. However, the larger challenge is to develop vaccines that generate strong T cell immunity with purified or recombinant vaccine antigens.

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

Combined mucosal and systemic immunity following pulmonary delivery of ISCOMATRIX adjuvanted recombinant antigens

Deep pulmonary delivery of an influenza ISCOMATRIX vaccine has previously been shown to induce a combined mucosal and systemic antibody response. To explore whether this combined response is influenced by intrinsic properties of the component antigen, we examined the efficacy of deep pulmonary delivery of ISCOMATRIX vaccines containing different recombinant antigens, specifically gB glycoprotein from cytomegalovirus and a fragment of catalase from Helicobacter pylori. Both these vaccines induced antigen-specific mucosal and systemic immunity, as well as antigen-specific proliferative cellular responses. Pulmonary immunisation with ISCOMATRIX vaccines may therefore be a generic way of inducing combined systemic and mucosal immunity.

A self-assembling peptide acting as an immune adjuvant

The development of vaccines and other immunotherapies has been complicated by heterogeneous antigen display and the use of incompletely defined immune adjuvants with complex mechanisms of action. We have observed strong antibody responses in mice without the coadministration of any additional adjuvant by noncovalently assembling a T and B cell epitope peptide into nanofibers using a short C-terminal peptide extension. Self-assembling peptides have been explored recently as scaffolds for tissue engineering and regenerative medicine, but our results indicate that these materials may also be useful as chemically defined adjuvants. In physiological conditions, these peptides self-assembled into long, unbranched fibrils that displayed the epitope on their surfaces. IgG1, IgG2a, and IgG3 were raised against epitope-bearing fibrils in levels similar to the epitope peptide delivered in complete Freund's adjuvant (CFA), and IgM production was even greater for the self-assembled epitope. This response was dependent on self-assembly, and the self-assembling sequence was not immunogenic by itself, even when delivered in CFA. Undetectable levels of interferon-gamma, IL-2, and IL-4 in cultures of peptide-challenged splenocytes from immunized mice suggested that the antibody responses did not involve significant T cell help.