Therapeutic vaccines for chronic diseases: successes and technical challenges

Virus-like Particles as Vaccines for Allergen-Specific Therapy: An Overview of Current Developments

Immune engineering and modulation are the basis of a novel but powerful tool to treat immune diseases using virus-like particles (VLPs). VLPs are formed by the viral capsid without genetic material making them non-infective. However, they offer a wide variety of possibilities as antigen-presenting platforms, resulting in high immunogenicity and high efficacy in immune modulation, with low allergenicity. Both animal and plant viruses are being studied for use in the treatment of food allergies. These formulations are combined with adjuvants, T-stimulatory epitopes, TLR ligands, and other immune modulators to modulate or enhance the immune response toward the presented allergen. Here, the authors present an overview of VLP production systems, their immune modulation capabilities, and the applicability of actual VLP-based formulations targeting allergic diseases.

Proof of concept for a single-dose Group B Streptococcus vaccine based on capsular polysaccharide conjugated to Qβ virus-like particles

A maternal vaccine to protect neonates against Group B Streptococcus invasive infection is an unmet medical need. Such a vaccine should ideally be offered during the third trimester of pregnancy and induce strong immune responses after a single dose to maximize the time for placental transfer of protective antibodies. A key target antigen is the capsular polysaccharide, an anti-phagocytic virulence factor that elicits protective antibodies when conjugated to carrier proteins. The most prevalent polysaccharide serotypes conjugated to tetanus or diphtheria toxoids have been tested in humans as monovalent and multivalent formulations, showing excellent safety profiles and immunogenicity. However, responses were suboptimal in unprimed individuals after a single shot, the ideal schedule for vaccination during the third trimester of pregnancy. In the present study, we obtained and optimized self-assembling virus-like particles conjugated to Group B Streptococcus capsular polysaccharides. The resulting glyco-nanoparticles elicited strong immune responses in mice already after one immunization, providing pre-clinical proof of concept for a single-dose vaccine.

A novel vaccine targeting β1-adrenergic receptor

Beta-blockers are widely used in the treatment of hypertension, heart failure and ischemic heart disease. However, unstandardized medication results in diverse clinical outcomes in patients. The main causes are unattained optimal doses, insufficient follow-up and patients' poor adherence. To improve the medication inadequacy, our team developed a novel therapeutic vaccine targeting β1-adrenergic receptor (β1-AR). The β1-AR vaccine named ABRQβ-006 was prepared by chemical conjugation of a screened β1-AR peptide with Qβ virus like particle (VLP). The antihypertensive, anti-remodeling and cardio-protective effects of β1-AR vaccine were evaluated in different animal models. The ABRQβ-006 vaccine was immunogenic that induced high titers of antibodies against β1-AR epitope peptide. In the NG-nitro-L-arginine methyl ester (L-NAME) + Sprague Dawley (SD) hypertension model, ABRQβ-006 lowered systolic blood pressure about 10 mmHg and attenuated vascular remodeling, myocardial hypertrophy and perivascular fibrosis. In the pressure-overload transverse aortic constriction (TAC) model, ABRQβ-006 significantly improved cardiac function, decreased myocardial hypertrophy, perivascular fibrosis and vascular remodeling. In the myocardial infarction (MI) model, ABRQβ-006 effectively improved cardiac remodeling, reduced cardiac fibrosis and inflammatory infiltration, which was superior to metoprolol. Moreover, no significant immune-mediated damage was observed in immunized animals. The ABRQβ-006 vaccine targeting β1-AR showed the effects on hypertension and heart rate control, myocardial remodeling inhibition and cardiac function protection. These effects could be differentiated in different types of diseases with diverse pathogenesis. ABRQβ-006 could be a novel and promising method for the treatment of hypertension and heart failure with different etiologies.

A single-dose Qβ VLP vaccine against S100A9 protein reduces atherosclerosis in a preclinical model

The standard therapy for cardiovascular disease (CVD) is the administration of statins to reduce plasma cholesterol levels, but this requires lifelong treatment. We developed a CVD vaccine candidate that targets the pro-inflammatory mediator calprotectin by eliciting antibodies against the S100A9 protein. The vaccine, based on bacteriophage Qβ virus-like particles (VLPs) displaying S100A9 peptide epitopes, was formulated as a slow-release PLGA:VLP implant by hot-melt extrusion. The single-dose implant elicited S100A9-specific antibody titers comparable to a three-dose injection schedule with soluble VLPs. In an animal model of CVD (ApoE-/- mice fed on a high-fat diet), the implant reduced serum levels of calprotectin, IL-1β, IL-6 and MCP-1, resulting in less severe aortic lesions. This novel implant was therefore able to attenuate atherosclerosis over a sustained period and offers a novel and promising strategy to replace the repetitive administration of statins for the treatment of CVD.

A single-dose, implant-based, trivalent virus-like particle vaccine against "cholesterol checkpoint" proteins

Cardiovascular disease is the number one cause of death globally. Lowering cholesterol levels in plasma is the mainstay therapy; however lifelong treatment and adverse effects call for improved therapeutic interventions. We developed a trivalent vaccine candidate targeting proprotein convertase subtilisin/kexin-9 (PCSK9), apolipoprotein B (ApoB), and cholesteryl ester transfer protein (CETP). Vaccine candidates were developed using bacteriophage Qβ-based virus-like particles (VLPs) displaying antigens of PCKS9, ApoB, and CETP, respectively. Vaccine candidate mixtures were formulated as slow-release PLGA:VLP implants using hot-melt extrusion. The delivery of the trivalent vaccine candidate via the implant produced antibodies against the cholesterol checkpoint proteins at levels comparable to a three-dose injection schedule with soluble mixtures. The reduction in PCSK9 and ApoB levels in plasma, inhibition of CETP (in vitro), and total plasma cholesterol decrease was achieved. All-together, we present a platform technology for a single-dose multi-target vaccination platform targeting cholesterol checkpoint proteins.

Chimeric RHDV Virus-Like Particles Displaying Foot-and-Mouth Disease Virus Epitopes Elicit Neutralizing Antibodies and Confer Partial Protection in Pigs

Currently there is a clear trend towards the establishment of virus-like particles (VLPs) as a powerful tool for vaccine development. VLPs are tunable nanoparticles that can be engineered to be used as platforms for multimeric display of foreign antigens. We have previously reported that VLPs derived from rabbit hemorrhagic disease virus (RHDV) constitute an excellent vaccine vector, capable of inducing specific protective immune responses against inserted heterologous T-cytotoxic and B-cell epitopes. Here, we evaluate the ability of chimeric RHDV VLPs to elicit immune response and protection against Foot-and-Mouth disease virus (FMDV), one of the most devastating livestock diseases. For this purpose, we generated a set of chimeric VLPs containing two FMDV-derived epitopes: a neutralizing B-cell epitope (VP1 (140-158)) and a T-cell epitope [3A (21-35)]. The epitopes were inserted joined or individually at two different locations within the RHDV capsid protein. The immunogenicity and protection potential of the chimeric VLPs were analyzed in the mouse and pig models. Herein we show that the RHDV engineered VLPs displaying FMDV-derived epitopes elicit a robust neutralizing immune response in mice and pigs, affording partial clinical protection against an FMDV challenge in pigs.

Development of a Vaccine against SARS-CoV-2 Based on the Receptor-Binding Domain Displayed on Virus-Like Particles

The ongoing coronavirus disease (COVID-19) pandemic is caused by a new coronavirus (severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2)) first reported in Wuhan City, China. From there, it has been rapidly spreading to many cities inside and outside China. Nowadays, more than 110 million cases with deaths surpassing 2 million have been recorded worldwide, thus representing a major health and economic issues. Rapid development of a protective vaccine against COVID-19 is therefore of paramount importance. Here, we demonstrated that the recombinantly expressed receptor-binding domain (RBD) of the spike protein can be coupled to immunologically optimized virus-like particles derived from cucumber mosaic virus (CuMVTT). The RBD displayed CuMVTT bound to ACE2, the viral receptor, demonstrating proper folding of RBD. Furthermore, a highly repetitive display of the RBD on CuMVTT resulted in a vaccine candidate that induced high levels of specific antibodies in mice, which were able to block binding of the spike protein to ACE2 and potently neutralize SARS-CoV-2 virus in vitro.

Capsid-like particles decorated with the SARS-CoV-2 receptor-binding domain elicit strong virus neutralization activity

The rapid development of a SARS-CoV-2 vaccine is a global priority. Here, we develop two capsid-like particle (CLP)-based vaccines displaying the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. RBD antigens are displayed on AP205 CLPs through a split-protein Tag/Catcher, ensuring unidirectional and high-density display of RBD. Both soluble recombinant RBD and RBD displayed on CLPs bind the ACE2 receptor with nanomolar affinity. Mice are vaccinated with soluble RBD or CLP-displayed RBD, formulated in Squalene-Water-Emulsion. The RBD-CLP vaccines induce higher levels of serum anti-spike antibodies than the soluble RBD vaccines. Remarkably, one injection with our lead RBD-CLP vaccine in mice elicits virus neutralization antibody titers comparable to those found in patients that had recovered from COVID-19. Following booster vaccinations, the virus neutralization titers exceed those measured after natural infection, at serum dilutions above 1:10,000. Thus, the RBD-CLP vaccine is a highly promising candidate for preventing COVID-19.

Retinoic Acid-Loaded Poly(lactic-co-glycolic acid) Nanoparticle Formulation of ApoB-100-Derived Peptide 210 Attenuates Atherosclerosis

We developed a vaccine formulation containing ApoB derived P210 peptides as autoantigens, retinoic acid (RA) as an immune enhancer, both of which were delivered using PLGA nanoparticles. The formula was used to induce an immune response in 12-week-old male Apoe^-/- mice with pre-existing atherosclerotic lesions. The nanotechnology platform PRINT^® was used to fabricate PLGA nanoparticles that encapsulated RA inside and adsorbed the P210 onto the particle surface. In this study, we demonstrated that immunization of Apoe^-/- mice with the formulation was able to considerably attenuate atherosclerotic lesions, accompanied by increased P210 specific IgM and another oxidized lipid derived autoantigen, M2AA, specific IgG autoantibodies, and decreased the inflammatory response, as compared to the P210 group with Freund's adjuvant. Our formulation represents an exciting technology to enhance the efficacy of the P210 vaccine.

Cowpea Mosaic Virus (CPMV)-Based Cancer Testis Antigen NY-ESO-1 Vaccine Elicits an Antigen-Specific Cytotoxic T Cell Response

Cancer vaccines are promising adjuvant immunotherapies that can stimulate the immune system to recognize tumor-associated antigens and eliminate the residual or recurring disease. The aberrant and restricted expression of highly immunogenic cancer testis antigen NY-ESO-1 in several malignancies, including triple-negative breast cancer, melanoma, myelomas, and ovarian cancer, makes NY-ESO-1 an attractive antigenic target for cancer vaccines. This study describes a NY-ESO-1 vaccine based on a bio-inspired nanomaterial platform technology, specifically a plant virus nanoparticle. The 30 nm icosahedral plant virus cowpea mosaic virus (CPMV) displaying multiple copies of human HLA-A2 restricted peptide antigen NY-ESO-1157-165 exhibited enhanced uptake and activation of antigen-presenting cells and stimulated a potent CD8+ T cell response in transgenic human HLA-A2 expressing mice. CD8+ T cells from immunized mice exhibited antigen-specific proliferation and cancer cell cytotoxicity, highlighting the potential application of a CPMV-NY-ESO-1 vaccine against NY-ESO-1+ malignancies.

The combination of artificial intelligence and systems biology for intelligent vaccine design

INTRODUCTION

A new body of evidence depicts the applications of artificial intelligence and systems biology in vaccine design and development. The combination of both approaches shall revolutionize healthcare, accelerating clinical trial processes and reducing the costs and time involved in drug research and development.

AREAS COVERED

This review explores the basics of artificial intelligence and systems biology approaches in the vaccine development pipeline. The topics include a detailed description of epitope prediction tools for designing epitope-based vaccines and agent-based models for immune system response prediction, along with a focus on their potentiality to facilitate clinical trial phases.

EXPERT OPINION

Artificial intelligence and systems biology offer the opportunity to avoid the inefficiencies and failures that arise in the classical vaccine development pipeline. One promising solution is the combination of both methodologies in a multiscale perspective through an accurate pipeline. We are entering an 'in silico era' in which scientific partnerships, including a more and more increasing creation of an 'ecosystem' of collaboration and multidisciplinary approach, are relevant for addressing the long and risky road of vaccine discovery and development. In this context, regulatory guidance should be developed to qualify the in silico trials as evidence for intelligent vaccine development.

Vaccination Against Amyloidogenic Aggregates in Pancreatic Islets Prevents Development of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a chronic progressive disease characterized by insulin resistance and insufficient insulin secretion to maintain normoglycemia. The majority of T2DM patients bear amyloid deposits mainly composed of islet amyloid polypeptide (IAPP) in their pancreatic islets. These-originally β-cell secretory products-extracellular aggregates are cytotoxic for insulin-producing β-cells and are associated with β-cell loss and inflammation in T2DM advanced stages. Due to the absence of T2DM preventive medicaments and the presence of only symptomatic drugs acting towards increasing hormone secretion and action, we aimed at establishing a novel disease-modifying therapy targeting the cytotoxic IAPP deposits in order to prevent the development of T2DM. We generated a vaccine based on virus-like particles (VLPs), devoid of genomic material, coupled to IAPP peptides inducing specific antibodies against aggregated, but not monomeric IAPP. Using a mouse model of islet amyloidosis, we demonstrate in vivo that our vaccine induced a potent antibody response against aggregated, but not soluble IAPP, strikingly preventing IAPP depositions, delaying onset of hyperglycemia and the induction of the associated pro-inflammatory cytokine Interleukin 1β (IL-1β). We offer the first cost-effective and safe disease-modifying approach targeting islet dysfunction in T2DM, preventing pathogenic aggregates without disturbing physiological IAPP function.

Virus-like particles for vaccination against cancer

Active immunotherapy of cancer aims to treat the disease by inducing effective cellular and humoral immune responses. Virus‐like particle‐based vaccines have evolved dramatically over the last few decades, greatly reducing morbidity and mortality of several infectious diseases and expectedly preventing cervical cancer caused by human papilloma virus. In contrast to these broad successes of disease prevention, therapeutic cancer vaccines remain to demonstrate clinical benefit. Yet, several preclinical and clinical trials have revealed promising results and are paving the way for medical breakthroughs. This study reviews and discusses the recent preclinical development and clinical trials in this field.

This article is categorized under:

Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Virus-Like Particles as Carrier Systems to Enhance Immunomodulation in Allergen Immunotherapy

PURPOSE OF REVIEW

Utilization of virus-like particles (VLPs) is considered to improve allergen-specific immunotherapy (AIT). AIT aims at the efficient uptake of the target allergen by antigen-presenting cells (APCs) subsequently inducing adaptive allergen-specific immune responses to induce tolerance. The purpose of this review is to describe the immune-modulating properties of VLPs per se and to summarize the application of VLPs as antigen carriers, preferably for Th2 cytokines or allergens, with and without simultaneous administration of adjuvants in order to modulate allergic immune responses.

RECENT FINDINGS

Currently, a broad variety of approaches considering the origin of the VLPs, the choice of the adjuvant and antigen, and the coupling of the antigen are under preclinical investigation. The data provide evidence that VLPs used as carrier for antigens/allergens strongly increase antigen immunogenicity, and might be suitable to prevent allergies. However, systematic studies in mice showing the immunological mechanism and data from clinical studies are scarce.

Antitumor Humoral and T Cell Responses by Mucin-1 Conjugates of Bacteriophage Qβ in Wild-type Mice

Mucin-1 (MUC1) is one of the top ranked tumor associated antigens. In order to generate effective anti-MUC1 immune responses as potential anticancer vaccines, MUC1 peptides and glycopeptides have been covalently conjugated to bacteriophage Qβ. Immunization of mice with these constructs led to highly potent antibody responses with IgG titers over one million, which are among the highest anti-MUC1 IgG titers reported to date. Furthermore, the high IgG antibody levels persisted for more than six months. The constructs also elicited MUC1 specific cytotoxic T cells, which can selectively kill MUC1 positive tumor cells. The unique abilities of Qβ-MUC1 conjugates to powerfully induce both antibody and cytotoxic T cell immunity targeting tumor cells bode well for future translation of the constructs as anticancer vaccines.

Eliminating Factor H-Binding Activity of Borrelia burgdorferi CspZ Combined with Virus-Like Particle Conjugation Enhances Its Efficacy as a Lyme Disease Vaccine

The spirochete Borrelia burgdorferi is the causative agent of Lyme disease, the most common tick-borne disease in the US and Europe. No potent human vaccine is currently available. The innate immune complement system is vital to host defense against pathogens, as complement activation on the surface of spirochetes results in bacterial killing. Complement system is inhibited by the complement regulator factor H (FH). To escape killing, B. burgdorferi produces an outer surface protein CspZ that binds FH to inhibit complement activation on the cell surface. Immunization with CspZ alone does not protect mice from infection, which we speculate is because FH-binding cloaks potentially protective epitopes. We modified CspZ by conjugating to virus-like particles (VLP-CspZ) and eliminating FH binding (modified VLP-CspZ) to increase immunogenicity. We observed greater bactericidal antibody titers in mice vaccinated with modified VLP-CspZ: A serum dilution of 1:395 (modified VLP-CspZ) vs 1:143 (VLP-CspZ) yielded 50% borreliacidal activity. Immunizing mice with modified VLP-CspZ cleared spirochete infection, as did passive transfer of elicited antibodies. This work developed a novel Lyme disease vaccine candidate by conjugating CspZ to VLP and eliminating FH-binding ability. Such a strategy of conjugating an antigen to a VLP and eliminating binding to the target ligand can serve as a general model for developing vaccines against other bacterial infectious agents.

Preclinical development of a vaccine against oligomeric alpha-synuclein based on virus-like particles

Parkinson's disease (PD) is a progressive and currently incurable neurological disorder characterised by the loss of midbrain dopaminergic neurons and the accumulation of aggregated alpha-synuclein (a-syn). Oligomeric a-syn is proposed to play a central role in spreading protein aggregation in the brain with associated cellular toxicity contributing to a progressive neurological decline. For this reason, a-syn oligomers have attracted interest as therapeutic targets for neurodegenerative conditions such as PD and other alpha-synucleinopathies. In addition to strategies using small molecules, neutralisation of the toxic oligomers by antibodies represents an attractive and highly specific strategy for reducing disease progression. Emerging active immunisation approaches using vaccines are already being trialled to induce such antibodies. Here we propose a novel vaccine based on the RNA bacteriophage (Qbeta) virus-like particle conjugated with short peptides of human a-syn. High titres of antibodies were successfully and safely generated in wild-type and human a-syn over-expressing (SNCA-OVX) transgenic mice following vaccination. Antibodies from vaccine candidates targeting the C-terminal regions of a-syn were able to recognise Lewy bodies, the hallmark aggregates in human PD brains. Furthermore, antibodies specifically targeted oligomeric and aggregated a-syn as they exhibited 100 times greater affinity for oligomeric species over monomer a-syn proteins in solution. In the SNCA-OVX transgenic mice used, vaccination was, however, unable to confer significant changes to oligomeric a-syn bioburden. Similarly, there was no discernible effect of vaccine treatment on behavioural phenotype as compared to control groups. Thus, antibodies specific for oligomeric a-syn induced by vaccination were unable to treat symptoms of PD in this particular mouse model.

Rhesus macaque and mouse models for down-selecting circumsporozoite protein based malaria vaccines differ significantly in immunogenicity and functional outcomes

BACKGROUND

Non-human primates, such as the rhesus macaques, are the preferred model for down-selecting human malaria vaccine formulations, but the rhesus model is expensive and does not allow for direct efficacy testing of human malaria vaccines. Transgenic rodent parasites expressing genes of human Plasmodium are now routinely used for efficacy studies of human malaria vaccines. Mice have however rarely predicted success in human malaria trials and there is scepticism whether mouse studies alone are sufficient to move a vaccine candidate into the clinic.

METHODS

A comparison of immunogenicity, fine-specificity and functional activity of two Alum-adjuvanted Plasmodium falciparum circumsporozoite protein (CSP)-based vaccines was conducted in mouse and rhesus models. One vaccine was a soluble recombinant protein (CSP) and the other was the same CSP covalently conjugated to the Qβ phage particle (Qβ-CSP).

RESULTS

Mice showed different kinetics of antibody responses and different sensitivity to the NANP-repeat and N-terminal epitopes as compared to rhesus. While mice failed to discern differences between the protective efficacy of CSP versus Qβ-CSP vaccine following direct challenge with transgenic Plasmodium berghei parasites, rhesus serum from the Qβ-CSP-vaccinated animals induced higher in vivo sporozoite neutralization activity.

CONCLUSIONS

Despite some immunologic parallels between models, these data demonstrate that differences between the immune responses induced in the two models risk conflicting decisions regarding potential vaccine utility in humans. In combination with historical observations, the data presented here suggest that although murine models may be useful for some purposes, non-human primate models may be more likely to predict the human response to investigational vaccines.

Development of Autologous C5 Vaccine Nanoparticles to Reduce Intravascular Hemolysis in Vivo

The complement system is emerging as a new target for treating many diseases. For example, Eculizumab, a humanized monoclonal antibody against complement component 5 (C5), has been approved for paroxysmal nocturnal hemoglobinuria (PNH) in which patient erythrocytes are lysed by complement. In this study, we developed vaccines to elicit autologous anti-C5 antibody production in mice for complement inhibition. Immunization of mice with a conservative C5 xenoprotein raised high titers of IgG's against the xenogenous C5, but these antibodies did not reduce C5 activity in the blood. In contrast, an autologous mouse C5 vaccine containing multiple predicted epitopes together with a tolerance-breaking peptide was found to induce anti-C5 autoantibody production in vivo, resulting in decreased hemolytic activity in the blood. We further validated a peptide epitope within this C5 vaccine and created recombinant virus-like particles (VLPs) displaying this epitope fused with the tolerance breaking peptide. Immunizing mice with these novel nanoparticles elicited strong humoral responses against recombinant mouse C5, reduced hemolytic activity, and protected the mice from complement-mediated intravascular hemolysis in a model of PNH. This proof-of-concept study demonstrated that autologous C5-based vaccines could be an effective alternative or supplement for treating complement-mediated diseases such as PNH.

Lifestyle Vaccines and Public Health: Exploring Policy Options for a Vaccine to Stop Smoking

Experimental vaccines are being developed for the treatment of 'unhealthy lifestyles' and associated chronic illnesses. Policymakers and other stakeholders will have to deal with the ethical issues that this innovation path raises: are there morally justified reasons to integrate these innovative biotechnologies in future health policies? Should public money be invested in further research? Focusing on the case of an experimental nicotine vaccine, this article explores the ethical aspects of 'lifestyle vaccines' for public health. Based on findings from a qualitative study into a vaccine for smoking cessation, the article articulates possible value conflicts related to nicotine vaccination as an intervention in tobacco control. The 'vaccinization' of lifestyle disease piggybacks on the achievements of classic vaccines. Contrary to expectations of simplicity and success, quitting smoking with a vaccine requires a complex supportive network. Social justice and public trust may become important ethical challenges when deciding whether to use further public funds for research or whether to implement these innovative vaccines in the future.

Virus-based nanoparticles as platform technologies for modern vaccines

Nanoscale engineering is revolutionizing the development of vaccines and immunotherapies. Viruses have played a key role in this field because they can function as prefabricated nanoscaffolds with unique properties that are easy to modify. Viruses are immunogenic via multiple pathways, and antigens displayed naturally or by engineering on the surface can be used to create vaccines against the cognate virus, other pathogens, specific molecules or cellular targets such as tumors. This review focuses on the development of virus-based nanoparticle systems as vaccines indicated for the prevention or treatment of infectious diseases, chronic diseases, cancer, and addiction. WIREs Nanomed Nanobiotechnol 2016, 8:554-578. doi: 10.1002/wnan.1383 For further resources related to this article, please visit the WIREs website.

Interleukin-1β-Targeted Vaccine Improves Glucose Control and β-Cell Function in a Diabetic KK-Ay Mouse Model

Interleukin-1β (IL-1β) has been implicated as a key proinflammatory cytokine involved in the pancreatic islet inflammation of type 2 diabetes mellitus (T2DM). Excess IL-1β impairs islet function by inducing insulin resistance and β-cell apoptosis. Therefore, specifically reducing IL-1β activity provides a therapeutic improvement for T2DM by sustaining the inhibition of IL-1β-mediated islet inflammation. In this study, we developed an IL-1β-targeted epitope peptide vaccine adjuvanted with polylactic acid microparticles (1βEPP) and applied it to a diabetic KK-Ay mouse model. Results showed that the 1βEPP elicited high antibody responses, which neutralized the biological activity of IL-1β, and induced barely detectable inflammatory activity. 1βEPP immunization reduced body weight gain, protected KK-Ay mice from hyperglycemia, improved glucose tolerance and insulin sensitivity, and decreased the serum levels of free fatty acids, total cholesterol and triglyceride. Moreover, 1βEPP restored β-cell mass; inhibited β-cell apoptosis; decreased the expression of IL-1β; and interrupted NF-κB activation by reducing IKKβ and pRelA levels. These studies indicated that the IL-1β-targeted vaccine may be a promising immunotherapeutic for T2DM treatment.

The effect of preexisting anti-carrier immunity on subsequent responses to CRM197 or Qb-VLP conjugate vaccines

CONTEXT

Certain antigens, such as haptens (small molecules), short peptides, and carbohydrates (e.g. bacterial polysaccharides) are non- or poorly immunogenic unless conjugated to a carrier molecule that provides a structural scaffold for antigen presentation as well as T cell help required for B-cell activation and maturation. However, the carriers themselves are immunogenic and resulting carrier-specific immune responses may impact the immunogenicity of other conjugate vaccines using the same carrier that are administered subsequently.

OBJECTIVE

Herein, using two different carriers (cross-reactive material 197, CRM and Qb-VLP), we examined in mice the impact that preexisting anti-carrier antibodies (Ab) had on subsequent immune responses to conjugates with either the same or a different carrier.

METHOD

For this purpose, we used two nicotine hapten conjugates (NIC7-CRM or NIC-Qb), two IgE peptide conjugates (Y-CRM or Y-Qb), and a pneumococcal polysaccharide conjugate (Prevnar 13(®)).

RESULTS

Prior exposure to CRM or Qb-VLP significantly reduced subsequent responses to the conjugated antigen having the homologous carrier, with the exception of Prevnar 13® where anti-polysaccharide responses were similar to those in animals without preexisting anti-carrier Ab.

CONCLUSION

Collectively, the data suggest that the relative sizes of the antigen and carrier, as well as the conjugation density for a given conjugate impact the extent of anti-carrier suppression. All animals developed anti-carrier responses with repeat vaccination and the differences in Ab titer between groups with and without preexisting anti-carrier responses became less apparent; however, anti-carrier effects were more durable for Ab function.

Beyond passive immunization: toward a nanoparticle-based IL-17 vaccine as first in class of future immune treatments

Nanoparticles occur naturally as part of repetitive molecular structures forming virus-like particles (VLPs). VLPs are powerful immune activators. Specifically, VLP can elicit a direct activation of B lymphocytes to trigger production of antibodies targeted at molecules chemically linked to the VLP. We here review recent data from genetics research, large-scale genomic sequencing, as well as clinical trials which suggest that a VLP-based vaccine against the signaling molecule IL-17 will be safe and effective in the common skin disease psoriasis, as well as other conditions. Active vaccination against IL-17 is capable of replacing the costly manufacture of antibodies currently in clinical use with huge implications for treatment availability and health economics.

Anti-IgE Qb-VLP Conjugate Vaccine Self-Adjuvants through Activation of TLR7

Qb bacteriophage virus-like particles (Qb-VLP) are utilized as carriers to enhance immune responses to weakly or non-immunogenic antigens such as peptides and haptens. Qb-VLPs are formed through the self-assembly of multiple Qb capsid protein monomers, a process which traps a large amount of bacterial RNA in the core of the VLP. Bacterial RNA is known to activate the innate immune system via TLR 7 and 8 found within the endosomes of certain immune cells and has been shown to contribute to the immunogenicity of Qb-VLP vaccines. Herein, we evaluated an anti-IgE vaccine comprised of two IgE peptides (Y and P) conjugated to Qb-VLP (Qb-Y and Qb-P, respectively) for in vitro stimulation of human PBMCs and in vivo immunogenicity in mice. The in vitro secretion of IFN-α from human PBMCs exposed to Qb-Y is consistent with TLR7 activation. Immunization of mice with the IgE peptide Qb-VLP conjugates induced high titers of anti-IgE antibodies in wild-type mice, but significantly lower titers in TLR7 knockout mice, supporting the self-adjuvanting role of the RNA. Inclusion of alum and alum/CpG as adjuvants partially or completely compensated for the lack of TLR7 activation in TLR7-deficient mice. Our study demonstrates the key role that TLR7 plays in the immunogenicity of the IgE peptide Qb-VLP conjugate vaccine.

Head-to-Head Comparison of Soluble vs. Qβ VLP Circumsporozoite Protein Vaccines Reveals Selective Enhancement of NANP Repeat Responses

Circumsporozoite protein (CSP) of Plasmodium falciparum is a promising malaria vaccine target. RTS,S, the most advanced malaria vaccine candidate consists of the central NANP repeat and carboxy-terminal region of CSP displayed on a hepatitis B virus-like particle (VLP). To build upon the success of RTS,S, we produced a near full-length Plasmodium falciparum CSP that also includes the conserved amino-terminal region of CSP. We recently showed that this soluble CSP, combined with a synthetic Toll-like-receptor-4 (TLR4) agonist in stable oil-in-water emulsion (GLA/SE), induces a potent and protective immune response in mice against transgenic parasite challenge. Here we have investigated whether the immunogenicity of soluble CSP could be further augmented by presentation on a VLP. Bacteriophage Qβ VLPs can be readily produced in E.coli, they have a diameter of 25 nm and contain packaged E. coli RNA which serves as a built in adjuvant through the activation of TLR7/8. CSP was chemically conjugated to Qβ and the CSP-Qβ vaccine immunogenicity and efficacy were compared to adjuvanted soluble CSP in the C57Bl/6 mouse model. When formulated with adjuvants lacking a TLR4 agonist (Alum, SE and Montanide) the Qβ-CSP induced higher anti-NANP repeat titers, higher levels of cytophilic IgG2b/c antibodies and a trend towards higher protection against transgenic parasite challenge as compared to soluble CSP formulated in the same adjuvant. The VLP and soluble CSP immunogenicity difference was most pronounced at low antigen dose, and within the CSP molecule, the titers against the NANP repeats were preferentially enhanced by Qβ presentation. While a TLR4 agonist enhanced the immunogenicity of soluble CSP to levels comparable to the VLP vaccine, the TLR4 agonist did not further improve the immunogenicity of the Qβ-CSP vaccine. The data presented here pave the way for further improvement in the Qβ conjugation chemistry and evaluation of both the Qβ-CSP and soluble CSP vaccines in the non-human primate model.

Particle-based platforms for malaria vaccines

Recombinant subunit vaccines in general are poor immunogens likely due to the small size of peptides and proteins, combined with the lack or reduced presentation of repetitive motifs and missing complementary signal(s) for optimal triggering of the immune response. Therefore, recombinant subunit vaccines require enhancement by vaccine delivery vehicles in order to attain adequate protective immunity. Particle-based delivery platforms, including particulate antigens and particulate adjuvants, are promising delivery vehicles for modifying the way in which immunogens are presented to both the innate and adaptive immune systems. These particle delivery platforms can also co-deliver non-specific immunostimodulators as additional adjuvants. This paper reviews efforts and advances of the Particle-based delivery platforms in development of vaccines against malaria, a disease that claims over 600,000 lives per year, most of them are children under 5 years of age in sub-Sahara Africa.

Anti-nicotine vaccines: Comparison of adjuvanted CRM197 and Qb-VLP conjugate formulations for immunogenicity and function in non-human primates

Anti-nicotine vaccines comprise nicotine-like haptens conjugated to a carrier protein plus adjuvant(s). Unfortunately, those tested clinically have failed to improve overall long term quit rates. We had shown in mice that carrier, hapten, linker, hapten load (number of haptens per carrier molecule), aggregation and adducts, as well as adjuvants influence the function of antibodies (Ab) induced. Herein, we tested an optimized antigen, NIC7-CRM, comprised of 5-aminoethoxy-nicotine (NIC7) conjugated to genetically detoxified diphtheria toxin (CRM197), with hapten load of ~16, no aggregation (~100% monomer) and minimal adducts. NIC7-CRM was tested in non-human primates (NHP) and compared to NIC-VLP, which has the same hapten and carrier as the clinical-stage CYT002-NicQb but a slightly different linker and lower hapten load. With alum as sole adjuvant, NIC7-CRM was superior to NIC-VLP for Ab titer, avidity and ex vivo function (83% and 27% nicotine binding at 40ng/mL respectively), but equivalent for in vivo function after intravenous [IV] nicotine challenge (brain levels reduced ~10%). CpG adjuvant added to NIC7-CRM/alum further enhanced the Ab responses and both ex vivo function (100% bound) and in vivo function (~80% reduction in brain). Thus, both optimal antigen design and CpG adjuvant were required to achieve a highly functional vaccine. The compelling NHP data with NIC7-CRM with alum/CpG supported human testing, currently underway.

Antigen delivery by virus-like particles for immunotherapeutic vaccination

Virus-like particles (VLPs) are an effective means of establishing both prophylactic and therapeutic immunity against their source virus or heterologous antigens. The particulate nature and repetitive structure of VLPs makes them ideal for stimulating potent immune responses. Epitopes delivered by VLPs can be presented on MHC-II for stimulation of a humoral immune response, or cross-presented onto MHC-I leading to cell-mediated immunity. VLPs as particulate subunit vaccine carriers are showing promise in preclinical and clinical trials for the treatment of many conditions including cancer, autoimmunity, allergies and addiction. Supporting the delivery of almost any form of antigenic material, VLPs are ideal candidate vectors for development of future vaccines.

Using viruses as nanomedicines

The field of nanomedicine involves the design and fabrication of novel nanocarriers for the intracellular delivery of therapeutic cargo or for use in molecular diagnostics. Although traditionally recognized for their ability to invade and infect host cells, viruses and bacteriophages have been engineered over the past decade as highly promising molecular platforms for the targeted delivery and treatment of many human diseases. Inherently biodegradable, the outer capsids of viruses are composed entirely of protein building blocks, which can be genetically or chemically engineered with molecular imaging reagents, targeting ligands and therapeutic molecules. While there are several examples of viruses as in vitro molecular cargo carriers, their potential for applications in nanomedicine has only recently emerged. Here we highlight recent developments towards the design and engineering of viruses for the treatment of cancer, bacterial infections and immune system-related diseases.

Is The Allergen Really Needed in Allergy Immunotherapy?

Immunotherapy for type I allergies is well established and is regarded to be the most efficient treatment option besides allergen avoidance. As of today, different forms of allergen preparations are used in this regard, as well as different routes of application. Virus-like particles (VLPs) represent a potent vaccine platform with proven immunogenicity and clinical efficacy. The addition of toll-like receptor ligands and/or depot-forming adjuvants further enhances activation of innate as well as adaptive immune responses. CpG motifs represent intensively investigated and potent direct stimulators of plasmacytoid dendritic cells and B cells, while T cell responses are enhanced indirectly through increased antigen presentation and cytokine release. This article will focus on the function of VLPs loaded with DNA rich in nonmethylated CG motifs (CpGs) and the clinical experience gained in the treatment of allergic rhinitis, demonstrating clinical efficacy also if administered without allergens. Several published studies have demonstrated a beneficial impact on allergic symptoms by treatment with CpG-loaded VLPs. Subcutaneous injection of VLPs loaded with CpGs was tested with or without the adjuvant alum in the presence or absence of an allergen. The results encourage further investigation of VLPs and CpG motifs in immunotherapy, either as a stand-alone product or as adjuvants for allergen-specific immunotherapy.

Plant-Based Vaccines as a Global Vaccination Approach: Current Perspectives

This chapter provides a perspective on the evolution of the field of plant-based vaccine from the limitations identified in initial developments as to how this biotechnological approach has become sophisticated via the development of new technologies and has gained industry interest. Perspectives for the field at both the basic research and the industrial level are emphasized. Perspectives considered of relevance in terms of basic research include (1) advancing the development of oral formulations, (2) expanding the modalities of expression of immunogens, (3) diversifying production platforms, particularly those performed under full containment, and (4) targeting a broader number of diseases. These goals are expected to multiply the expectations for benefits derived from plant-based vaccine-production technology. On the other hand, technology transfer and regulatory issues represent a critical hurdle to this technology becoming a reality. It is also critical to achieve social acceptance as well as implement initiatives for the exploitation of the technology for humanitarian purposes and for the benefit of poor countries. This overview predicts considerable potential for plant-based vaccines to positively impact the field of vaccinology in the near future.

The contribution of vaccination to global health: past, present and future

Vaccination has made an enormous contribution to global health. Two major infections, smallpox and rinderpest, have been eradicated. Global coverage of vaccination against many important infectious diseases of childhood has been enhanced dramatically since the creation of WHO's Expanded Programme of Immunization in 1974 and of the Global Alliance for Vaccination and Immunization in 2000. Polio has almost been eradicated and success in controlling measles makes this infection another potential target for eradication. Despite these successes, approximately 6.6 million children still die each year and about a half of these deaths are caused by infections, including pneumonia and diarrhoea, which could be prevented by vaccination. Enhanced deployment of recently developed pneumococcal conjugate and rotavirus vaccines should, therefore, result in a further decline in childhood mortality. Development of vaccines against more complex infections, such as malaria, tuberculosis and HIV, has been challenging and achievements so far have been modest. Final success against these infections may require combination vaccinations, each component stimulating a different arm of the immune system. In the longer term, vaccines are likely to be used to prevent or modulate the course of some non-infectious diseases. Progress has already been made with therapeutic cancer vaccines and future potential targets include addiction, diabetes, hypertension and Alzheimer's disease.

Plant-based vaccines for Alzheimer's disease: an overview

Plants are considered advantageous platforms for biomanufacturing recombinant vaccines. This constitutes a field of intensive research and some plant-derived vaccines are expected to be marketed in the near future. In particular, plant-based production of immunogens targeting molecules with implications on the pathology of Alzheimer's has been explored over the last decade. These efforts involve targeting amyloid beta and β-secretase with several immunogen configurations that have been evaluated in test animals. The results of these developments are analyzed in this review. Perspectives on the topic are identified, such as exploring additional antigen configurations and adjuvants in order to improve immunization schemes, characterizing in detail the elicited immune responses, and immunological considerations in the achievement of therapeutic humoral responses via mucosal immunization. Safety concerns related to these therapies will also be discussed.

Prophylactic and therapeutic vaccines for obesity

Chronic diseases such as obesity and diabetes are major causes of death and disability throughout the world. Many causes are known to trigger these chronic diseases, and infectious agents such as viruses are also pathological factors. In particular, it is considered that adenovirus 36 infections may be associated with obesity. If this is the case, a vaccine against adenovirus 36 may be a form of prophylaxis to combat obesity. Other types of therapeutic vaccines to combat obesity are also being developed. Recently, hormones such as glucagon-like peptide-1, ghrelin, and peptide YY have been studied as treatments to prevent obesity. This review describes the ongoing development of therapeutic vaccines to treat obesity, and the possibility of using inactivated adenovirus 36 as a vaccine and an anti-obesity agent.

Multi-therapeutic potential of autoantibodies induced by immune complexes trapped on follicular dendritic cells

Induction of autoantibodies (autoAbs) targeting disease drivers / mediators is emerging as a potential immunotherapeutic strategy. Auto-immune complex (IC)-retaining follicular dendritic cells (FDCs) critically regulate pathogenic autoAb production in autoreactive germinal centers (GCs); however, their ability to induce potentially therapeutic autoAbs has not been explored. We hypothesized that deliberate display of clinically targeted antigens (Ags) in the form of ICs on FDC membranes induces target-specific autoreactive GCs and autoAbs that may be exploited therapeutically. To test our hypothesis, three therapeutically relevant Ags: TNF-α, HER2/neu and IgE, were investigated. Our results indicated that TNF-α-, HER2/neu- and IgE-specific autoAbs associated with strong GC reactions were induced by TNF-α-, HER2/neu- and IgE-IC retention on FDCs. Moreover, the induced anti-TNF-α autoAbs neutralized mouse and human TNF-α with half maximal Inhibitory Concentration (IC₅₀) of 7.1 and 1.6 nM respectively. In addition, we demonstrated that FDC-induced Ab production could be non-specifically inhibited by the IgG-specific Endo-S that accessed the light zones of GCs and interfered with FDC-IC retention. In conclusion, the ability of FDCs to productively present autoAgs raises the potential for a novel immunotherapeutic platform targeting mediators of autoimmune disorders, allergic diseases, and Ab responsive cancers.

VLPs and particle strategies for cancer vaccines

Effective delivery of tumor antigens to APCs is one of the key steps for eliciting a strong and durable immune response to tumors. Several cancer vaccines have been evaluated in clinical trials, based on soluble peptides, but results have not been fully satisfactory. To improve immunogenicity particles provide a valid strategy to display and/or incorporate epitopes which can be efficiently targeted to APCs for effective induction of adaptive immunity. In the present review, we report some leading technologies for developing particulate vaccines employed in cancer immunotherapy, highlighting the key parameters for a rational design to elicit both humoral and cellular responses.

Design of novel vaccines based on virus-like particles or chimeric virions

Virus-like particles (VLPs) are formed by viral structural proteins that, when overexpressed, spontaneously self-assemble into particles that are antigenically indistinguishable from infectious virus or subviral particles. VLPs are appealing as vaccine candidates because their inherent properties (i.e., virus-sized, multimeric antigens, highly organised and repetitive structure, not infectious) are suitable for the induction of safe and efficient humoral and cellular immune responses. VLP-based vaccines have already been licensed for human and veterinary use, and many more vaccine candidates are currently in late stages of evaluation. Moreover, the development of VLPs as platforms for foreign antigen display has further broadened their potential applicability both as prophylactic and therapeutic vaccines. This chapter provides an overview on the design and use of VLPs for the development of new generation vaccines.

Construction and characterization of virus-like particles: a review

Over the last three decades, virus-like particles (VLPs) have evolved to become a widely accepted technology, especially in the field of vaccinology. In fact, some VLP-based vaccines are currently used as commercial medical products, and other VLP-based products are at different stages of clinical study. Several remarkable advantages have been achieved in the development of VLPs as gene therapy tools and new nanomaterials. The analysis of published data reveals that at least 110 VLPs have been constructed from viruses belonging to 35 different families. This review therefore discusses the main principles in the cloning of viral structural genes, the relevant host systems and the purification procedures that have been developed. In addition, the methods that are used to characterize the structural integrity, stability, and components, including the encapsidated nucleic acids, of newly synthesized VLPs are analyzed. Moreover, some of the modifications that are required to construct VLP-based carriers of viral origin with defined properties are discussed, and examples are provided.

Vaccines and future global health needs

Increased international support for both research into new vaccines and their deployment in developing countries has been evident over the past decade. In particular, the GAVI Alliance has had a major impact in increasing uptake of the six common infant vaccines as well as those against hepatitis B and yellow fever. It further aims to introduce pneumococcal and rotavirus vaccines in the near future and several others, including those against human papillomavirus, meningococcal disease, rubella and typhoid not long after that. In addition, there is advanced research into vaccines against malaria, HIV/AIDS and tuberculosis. By 2030, we may have about 20 vaccines that need to be used in the developing world. Finding the requisite funds to achieve this will pose a major problem. A second and urgent question is how to complete the job of global polio eradication. The new strategic plan calls for completion by 2013, but both pre-eradication and post-eradication challenges remain. Vaccines will eventually become available beyond the field of infectious diseases. Much interesting work is being done in both autoimmunity and cancer. Cutting across disease groupings, there are issues in methods of delivery and new adjuvant formulations.

Twenty-first century vaccines

In the twentieth century, vaccination has been possibly the greatest revolution in health. Together with hygiene and antibiotics, vaccination led to the elimination of many childhood infectious diseases and contributed to the increase in disability-free life expectancy that in Western societies rose from 50 to 78-85 years (Crimmins, E. M. & Finch, C. E. 2006 Proc. Natl Acad. Sci. USA 103, 498-503; Kirkwood, T. B. 2008 Nat. Med 10, 1177-1185). In the twenty-first century, vaccination will be expected to eliminate the remaining childhood infectious diseases, such as meningococcal meningitis, respiratory syncytial virus, group A streptococcus, and will address the health challenges of this century such as those associated with ageing, antibiotic resistance, emerging infectious diseases and poverty. However, for this to happen, we need to increase the public trust in vaccination so that vaccines can be perceived as the best insurance against most diseases across all ages.

Vaccines and global health

Vaccines have made a major contribution to global health in recent decades but they could do much more. In November 2011, a Royal Society discussion meeting, 'New vaccines for global health', was held in London to discuss the past contribution of vaccines to global health and to consider what more could be expected in the future. Papers presented at the meeting reviewed recent successes in the deployment of vaccines against major infections of childhood and the challenges faced in developing vaccines against some of the world's remaining major infectious diseases such as human immunodeficiency virus (HIV), malaria and tuberculosis. The important contribution that development of more effective veterinary vaccines could make to global health was also addressed. Some of the social and financial challenges to the development and deployment of new vaccines were reviewed. The latter issues were also discussed at a subsequent satellite meeting, 'Accelerating vaccine development', held at the Kavli Royal Society International Centre. Delegates at this meeting considered challenges to the more rapid development and deployment of both human and veterinary vaccines and how these might be addressed. Papers based on presentations at the discussion meeting and a summary of the main conclusions of the satellite meeting are included in this issue of Philosophical Transactions of the Royal Society B.