Protection against osteoporosis by active immunization with TRANCE/RANKL displayed on virus-like particles

Blackcurrants shape gut microbiota profile and reduce risk of postmenopausal osteoporosis via the gut-bone axis: Evidence from a pilot randomized controlled trial

This study aimed to investigate the effects of blackcurrant (BC) on gut microbiota abundance and composition, inflammatory and immune responses, and their relationship with bone mass changes. The effects of BC on bone mineral density (BMD), gut microbiota, and blood inflammatory and immune biomarkers were evaluated using DXA, stool and fasting blood collected from a pilot three-arm, randomized, double-blind, placebo-controlled clinical trial. Fifty-one peri- and early postmenopausal women aged 45-60 years were randomly assigned into one of three treatment groups for 6 months: control, low BC (392 mg/day) and high BC (784 mg/day); and 40 women completed the trial. BC supplementation for 6 months effectively mitigated the loss of whole-body BMD (P<.05). Six-month changes (%) in peripheral IL-1β (P=.056) and RANKL (P=.052) for the high BC group were marginally significantly lower than the control group. Six-month changes in whole-body BMD were inversely correlated with changes in RANKL (P<.01). In proteome analysis, four plasma proteins showed increased expression in the high BC group: IGFBP4, tetranectin, fetuin-B, and vitamin K-dependent protein S. BC dose-dependently increased the relative abundance of Ruminococcus 2 (P<.05), one of six bacteria correlated with BMD changes in the high BC group (P<.05), suggesting it might be the key bacteria that drove bone protective effects. Daily BC consumption for 6 months mitigated bone loss in this population potentially through modulating the gut microbiota composition and suppressing osteoclastogenic cytokines. Larger-scale clinical trials on the potential benefits of BC and connection of Ruminococcus 2 with BMD maintenance in postmenopausal women are warranted. Trial Registration: NCT04431960, https://classic.clinicaltrials.gov/ct2/show/NCT04431960.

Structural basis of epitope recognition by anti-alpha-synuclein antibodies MJFR14-6-4-2

Alpha-synuclein (α-syn) inclusions in the brain are hallmarks of so-called Lewy body diseases. Lewy bodies contain mainly aggregated α-syn together with some other proteins. Monomeric α-syn lacks a well-defined three-dimensional structure, but it can aggregate into oligomeric and fibrillar amyloid species, which can be detected using specific antibodies. Here we investigate the aggregate specificity of monoclonal MJFR14-6-4-2 antibodies. We conclude that partial masking of epitope in unstructured monomer in combination with a high local concentration of epitopes is the main reason for MJFR14-6-4-2 selectivity towards aggregates. Based on the structural insight, we produced mutant α-syn that when fibrillated is unable to bind MJFR14-6-4-2. Using these fibrils as a tool for seeding cellular α-syn aggregation, provides superior signal/noise ratio for detection of cellular α-syn aggregates by MJFR14-6-4-2. Our data provide a molecular level understanding of specific recognition of toxic amyloid oligomers, which is critical for the development of inhibitors against synucleinopathies.

Vaccine of RANKL mutant conjugated with KLH effectively stabilizing bone metabolism and preventing trabecular microstructural degeneration in osteoporotic rats

Receptor activator of nuclear factor kappa-B ligand (RANKL) is one of the key factors regulating the maturation of osteoclasts and an important target for osteoporosis treatment. A monoclonal antibody against RANKL showed effective therapeutic activity against osteoporosis by inhibiting bone resorption by osteoclasts. However, being an exogenous protein, its efficacy decreases after long-term use, and its discontinuation increases the risk of vertebral fractures. Here, we aimed to design an active immunotherapeutic agent to induce a T-cell dependent primary response. The agent, a mutant RANKL vaccine (mRv), was produced by cross-linking mutant RANKL, lacking the ability to stimulate osteoclast maturation, with the carrier protein keyhole limpet hemocyanin, a neo-antigen with a large molecular mass. Subcutaneous injection of mRv stimulated rats with ovariectomy-induced osteoporosis to produce high titers of anti-RANKL antibodies. The mutant RANKL vaccine decreased serum CTX-1 and BALP levels and inhibited the microstructural degeneration of trabecular bone in osteoporotic rats. mRv overcame immune system tolerance, stimulated rats to produce therapeutic antibodies, stabilized bone metabolism, and inhibited trabecular microstructural degeneration. These findings confirm the potential of the mutant RANKL vaccine to be developed into an effective preventive and therapeutic agent for osteoporosis.

A novel modified RANKL variant can prevent osteoporosis by acting as a vaccine and an inhibitor

BACKGROUND

The discovery of receptor activator of nuclear factor-ĸB ligand (RANKL) as the final effector in the pathogenesis of osteoporosis has led to a better understanding of bone remodeling. When RANKL binds to its receptor (RANK), osteoclastic differentiation and activation are initiated. Herein, we propose a strategy using a novel RANKL variant as a competitive inhibitor for RANKL. The RANKL variant activates LGR4 signaling, which competitively regulates RANK and acts as an immunogen that induces anti-RANKL antibody production.

METHODS

We modified the RANK-binding site on RANKL using minimal amino acid changes in the RANKL complex and its counterpart receptor RANK and tried to evaluate the inhibitory effects on osteoclastogenesis.

RESULTS

The novel RANKL variant did not bind RANK in osteoclast progenitor cells, but activated LGR4 through the GSK3-β signaling pathway, thereby suppressing activated T cell cytoplasmic nuclear factor calcineurin-dependent 1 (NFATc1) expression and activity during osteoclastogenesis. Our RANKL variant generated high levels of RANKL-specific antibodies, blocked osteoclastogenesis, and inhibited osteoporosis in ovariectomized mouse models. Generated anti-RANKL antibodies showed a high inhibitory effect on osteoclastogenesis in vivo and in vitro.

CONCLUSIONS

We observed that the novel RANKL indeed blocks RANKL via LGR4 signaling and generates anti-RANKL antibodies, demonstrating an innovative strategy in the development of general immunotherapy.

Modification of the RANKL-RANK-binding site for the immunotherapeutic treatment of osteoporosis

Here, we proposed the use of mutated RANKL as an immunogen for active immunization and to induce anti-cytokine antibodies for osteoporosis treatment.

INTRODUCTION

Osteoclasts are responsible for bone resorption in bone-related disorders. Anti-cytokine therapeutic antibodies such as denosumab are effective for the treatment of osteoporosis. However, problems with antibody manufacturing and the immunogenicity caused by multiple antibody doses have led to the use of auto-cytokines as immunogens to induce anti-cytokine antibodies.

METHODS

RANKL was point-mutated based on the crystal structure of the complex of RANKL and its receptor RANK.

RESULTS

As a proof of concept, immunization with RANKL produced high levels of specific antibodies and blocked osteoclast development in vitro and inhibited osteoporosis in RANKL-treated or ovariectomized mouse models.

CONCLUSIONS

The results demonstrate the successful use of mutated RANKL as an immunogen for the induction of anti-RANKL immune response. This strategy is useful in general anti-cytokine immunotherapy to avoid toxic side effects of osteoporosis treatment.

Virus-Like Particles as an Immunogenic Platform for Cancer Vaccines

Virus-like particles (VLP) spontaneously assemble from viral structural proteins. They are naturally biocompatible and non-infectious. VLP can serve as a platform for many potential vaccine epitopes, display them in a dense repeating array, and elicit antibodies against non-immunogenic substances, including tumor-associated self-antigens. Genetic or chemical conjugation facilitates the multivalent display of a homologous or heterologous epitope. Most VLP range in diameter from 25 to 100 nm and, in most cases, drain freely into the lymphatic vessels and induce antibodies with high titers and affinity without the need for additional adjuvants. VLP administration can be performed using different strategies, regimens, and doses to improve the immunogenicity of the antigen they expose on their surface. This article summarizes the features of VLP and presents them as a relevant platform technology to address not only infectious diseases but also chronic diseases and cancer.

A novel recombinant RANKL vaccine prepared by incorporation of an unnatural amino acid into RANKL and its preventive effect in a murine model of collagen-induced arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammatory synovitis, bone atrophy, and subsequent progressive destruction of articular tissue. Targeted inhibition of receptor activator of NF-kB ligand (RANKL) has been highly successful in preventing RA-mediated bone erosion in animal models and patients, suggesting that development of a RANKL vaccine might be of therapeutic value. Our previous study has shown that the recombinant RANKL vaccine Y²³⁴pNO₂Phe, generated by replacement of a single tyrosine residue (Tyr²³⁴) in murine RANKL (mRANKL) with p-nitrophenylalanine (pNO₂Phe), induces a high titer antibody response and prevents ovariectomy (OVX)-induced bone loss in mice. This aim of this study was to further evaluate the vaccine's preventive effects in a murine model of collagen-induced arthritis. The results of this study showed that Y²³⁴pNO₂Phe not only induced a high titer antibody response and inhibited osteoclastogenesis but also significantly prevented bone erosion and ameliorated the severity of a collagen-induced arthritis (CIA) model in mice. Moreover, use of the vaccine improved the clinical situations of the CIA mice. These results suggest a potential application of an anti-RANKL vaccine in the treatment of RA-induced bone erosion.

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.

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.

The application of virus-like particles as vaccines and biological vehicles

Virus-like particles (VLPs) can be spontaneously self-assembled by viral structural proteins under appropriate conditions in vitro while excluding the genetic material and potential replication probability. In addition, VLPs possess several features including can be rapidly produced in large quantities through existing expression systems, highly resembling native viruses in terms of conformation and appearance, and displaying repeated cluster of epitopes. Their capsids can be modified via genetic insertion or chemical conjugation which facilitating the multivalent display of a homologous or heterogeneous epitope antigen. Therefore, VLPs are considered as a safe and effective candidate of prophylactic and therapeutic vaccines. VLPs, with a diameter of approximately 20 to 150 nm, also have the characteristics of nanometer materials, such as large surface area, surface-accessible amino acids with reactive moieties (e.g., lysine and glutamic acid residues), inerratic spatial structure, and good biocompatibility. Therefore, assembled VLPs have great potential as a delivery system for specifically carrying a variety of materials. This review summarized recent researches on VLP development as vaccines and biological vehicles, which demonstrated the advantages and potential of VLPs in disease control and prevention and diagnosis. Then, the prospect of VLP biology application in the future is discussed as well.

A RANKL mutant used as an inter-species vaccine for efficient immunotherapy of osteoporosis

Anti-cytokine therapeutic antibodies have been demonstrated to be effective in the treatment of several auto-immune disorders. However, The problems in antibody manufacture and the immunogenicity caused by multiple doses of antibodies inspire people to use auto-cytokine as immunogen to induce anti-cytokine antibodies. Nevertheless, the tolerance for inducing immune response against self-antigen has hindered the wide application of the strategy. To overcome the tolerance, here we proposed a strategy using the inter-species cytokine as immunogen for active immunization (TISCAI) to induce anti-cytokine antibody. As a proof of concept, an inter-species cytokine RANKL was successfully used as immunogen to induce anti-RANKL immune response. Furthermore, to prevent undesirable side-effects, the human RANKL was mutated based on the crystal structure of the complex of human RANKL and its rodent counterpart receptor RANK. We found, the antibodies produced blocked the osteoclast development in vitro and osteoporosis in OVX rat models. The results demonstrated this strategy adopted is very useful for general anti-cytokine immunotherapy for different diseases settings.

Enhanced neutralizing antibody titers and Th1 polarization from a novel Escherichia coli derived pandemic influenza vaccine

Influenza pandemics can spread quickly and cost millions of lives; the 2009 H1N1 pandemic highlighted the shortfall in the current vaccine strategy and the need for an improved global response in terms of shortening the time required to manufacture the vaccine and increasing production capacity. Here we describe the pre-clinical assessment of a novel 2009 H1N1 pandemic influenza vaccine based on the E. coli-produced HA globular head domain covalently linked to virus-like particles derived from the bacteriophage Qβ. When formulated with alum adjuvant and used to immunize mice, dose finding studies found that a 10 µg dose of this vaccine (3.7 µg globular HA content) induced antibody titers comparable to a 1.5 µg dose (0.7 µg globular HA content) of the licensed 2009 H1N1 pandemic vaccine Panvax, and significantly reduced viral titers in the lung following challenge with 2009 H1N1 pandemic influenza A/California/07/2009 virus. While Panvax failed to induce marked T cell responses, the novel vaccine stimulated substantial antigen-specific interferon-γ production in splenocytes from immunized mice, alongside enhanced IgG2a antibody production. In ferrets the vaccine elicited neutralizing antibodies, and following challenge with influenza A/California/07/2009 virus reduced morbidity and lowered viral titers in nasal lavages.

Follicular dendritic cells in health and disease

Follicular dendritic cells (FDCs) are unique immune cells that contribute to the regulation of humoral immune responses. These cells are located in the B-cell follicles of secondary lymphoid tissues where they trap and retain antigens (Ags) in the form of highly immunogenic immune complexes (ICs) consisting of Ag plus specific antibody (Ab) and/or complement proteins. FDCs multimerize Ags and present them polyvalently to B-cells in periodically arranged arrays that extensively crosslink the B-cell receptors for Ag (BCRs). FDC-FcγRIIB mediates IC periodicity, and FDC-Ag presentation combined with other soluble and membrane bound signals contributed by FDCs, like FDC-BAFF, -IL-6, and -C4bBP, are essential for the induction of the germinal center (GC) reaction, the maintenance of serological memory, and the remarkable ability of FDC-Ags to induce specific Ab responses in the absence of cognate T-cell help. On the other hand, FDCs play a negative role in several disease conditions including chronic inflammatory diseases, autoimmune diseases, HIV/AIDS, prion diseases, and follicular lymphomas. Compared to other accessory immune cells, FDCs have received little attention, and their functions have not been fully elucidated. This review gives an overview of FDC structure, and recapitulates our current knowledge on the immunoregulatory functions of FDCs in health and disease. A better understanding of FDCs should permit better regulation of Ab responses to suit the therapeutic manipulation of regulated and dysregulated immune responses.

Virus like particle based strategy to elicit HIV-protective antibodies to the alpha-helic regions of gp41

Natural antibodies to gp41 inhibit HIV-1 replication through the recognition of two different regions, corresponding to the leucine zipper motif in the HR1 alpha-helix and to another motif within HR2 region, hosting 2F5 and 4E10 epitope. This study aimed at reproducing such protective responses through VLP vaccination. Six regions covering the alpha-helical regions of gp41 were conjugated to the surface of AP205 phage-based VLPs. Once administered in mice via systemic or mucosal route, these immunogens elicited high titers of gp41-specific IgG. Immunogenicity and HIV infectivity reduction were obtained either with HR2 regions or with peptides where aminoacid strings were added to either the C-terminus or N-terminus of core epitope in HR1 region. Antibody-dependent cell cytotoxicity (ADCC) activity was induced by one of the HR2 epitopes only. These results may have relevant implications for the development of new vaccinal approaches against HIV infection.

Therapeutic vaccines for chronic diseases: successes and technical challenges

Chronic, non-communicable diseases are the major cause of death and disability worldwide and have replaced infectious diseases as the major burden of society in large parts of the world. Despite the complexity of chronic diseases, relatively few predisposing risk factors have been identified by the World Health Organization. Those include smoking, alcohol abuse, obesity, high cholesterol and high blood pressure as the cause of many of these chronic conditions. Here, we discuss several examples of vaccines that target these risk factors with the aim of preventing the associated diseases and some of the challenges they face.

Immunodrugs: breaking B- but not T-cell tolerance with therapeutic anticytokine vaccines

Pathology in most chronic inflammatory diseases is characterized by an imbalance in cytokine expression. Targeting cytokines with monoclonal antibodies has proven to be a highly effective treatment. However, monoclonal antibody therapy has disadvantages such as high production costs, generation of antimonoclonal antibodies and the inconvenience of frequent injections. Therapeutic vaccines have the potential to overcome these limitations. The aim of active vaccination is to induce B-cell responses and obtain autoantibodies capable of neutralizing the interaction of the targeted cytokine with its receptor. In order to achieve this, therapeutic vaccines need to circumvent the potent tolerance mechanisms that exist to prevent immune responses against self-molecules. This article focuses on the tolerance mechanisms of the B- and T-cell compartments and how these may be manipulated to obtain high-affinity autoantibodies without inducing potentially dangerous autoreactive T-cell responses.

A VLP-based vaccine targeting domain III of the West Nile virus E protein protects from lethal infection in mice

Background

Since its first appearance in the USA in 1999, West Nile virus (WNV) has spread in the Western hemisphere and continues to represent an important public health concern. In the absence of effective treatment, there is a medical need for the development of a safe and efficient vaccine. Live attenuated WNV vaccines have shown promise in preclinical and clinical studies but might carry inherent risks due to the possibility of reversion to more virulent forms. Subunit vaccines based on the large envelope (E) glycoprotein of WNV have therefore been explored as an alternative approach. Although these vaccines were shown to protect from disease in animal models, multiple injections and/or strong adjuvants were required to reach efficacy, underscoring the need for more immunogenic, yet safe DIII-based vaccines.

Results

We produced a conjugate vaccine against WNV consisting of recombinantly expressed domain III (DIII) of the E glycoprotein chemically cross-linked to virus-like particles derived from the recently discovered bacteriophage AP205. In contrast to isolated DIII protein, which required three administrations to induce detectable antibody titers in mice, high titers of DIII-specific antibodies were induced after a single injection of the conjugate vaccine. These antibodies were able to neutralize the virus in vitro and provided partial protection from a challenge with a lethal dose of WNV. Three injections of the vaccine induced high titers of virus-neutralizing antibodies, and completely protected mice from WNV infection.

Conclusions

The immunogenicity of DIII can be strongly enhanced by conjugation to virus-like particles of the bacteriophage AP205. The superior immunogenicity of the conjugate vaccine with respect to other DIII-based subunit vaccines, its anticipated favourable safety profile and low production costs highlight its potential as an efficacious and cost-effective prophylaxis against WNV.

Kinoids: a family of immunogens for active anticytokine immunotherapy applied to autoimmune diseases and cancer

The complex homeostasis of tissues is coordinated by the cytokine network and imbalances in this network may result in chronic immune disorders. Key specific cytokines, such as TNF-α, IFN-α, IL-4 or VEGF have been demonstrated to be overproduced or abnormally released in the microenvironment of pathologic tissues. These findings have opened up the way to passive immunotherapy with anticytokine monoclonal antibodies. Even though passive immunotherapy has proved to be efficient, it is hampered by specific limitations. The discovery of a family of immunogens, the kinoids, consisting of inactivated cytokine derivatives, has led some to propose them for active immunotherapy as an alternative to passive immunotherapy. This review focuses on kinoids – on their validation in experimental mouse models and ongoing clinical trials. The advantages offered by this active immune therapy in terms of efficacy, safety and patient compliance will be stressed.

Versatile virus-like particle carrier for epitope based vaccines

BACKGROUND

Recombinant proteins and in particular single domains or peptides are often poorly immunogenic unless conjugated to a carrier protein. Virus-like-particles are a very efficient means to confer high immunogenicity to antigens. We report here the development of virus-like-particles (VLPs) derived from the RNA bacteriophage AP205 for epitope-based vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Peptides of angiotensin II, S.typhi outer membrane protein (D2), CXCR4 receptor, HIV1 Nef, gonadotropin releasing hormone (GnRH), Influenza A M2-protein were fused to either N- or C-terminus of AP205 coat protein. The A205-peptide fusions assembled into VLPs, and peptides displayed on the VLP were highly immunogenic in mice. GnRH fused to the C-terminus of AP205 induced a strong antibody response that inhibited GnRH function in vivo. Exposure of the M2-protein peptide at the N-terminus of AP205 resulted in a strong M2-specific antibody response upon immunization, protecting 100% of mice from a lethal influenza infection.

CONCLUSIONS/SIGNIFICANCE

AP205 VLPs are therefore a very efficient and new vaccine system, suitable for complex and long epitopes, of up to at least 55 amino acid residues in length. AP205 VLPs confer a high immunogenicity to displayed epitopes, as shown by inhibition of endogenous GnRH and protective immunity against influenza infection.

Carrier induced epitopic suppression of antibody responses induced by virus-like particles is a dynamic phenomenon caused by carrier-specific antibodies

Pre-existing immunity against vaccine carrier proteins has been reported to inhibit the immune response against antigens conjugated to the same carrier by a process termed carrier induced epitopic suppression (CIES). Hence understanding the phenomenon of CIES is of major importance for the development of conjugate vaccines. Virus-like particles (VLPs) are a novel class of potent immunological carriers which have been successfully used to enhance the antibody response to virtually any conjugated antigen. In the present study we investigated the impact of a pre-existing VLP-specific immune response on the development of antibody responses against a conjugated model peptide after primary, secondary and tertiary immunization. Although VLP-specific immune responses led to reduced peptide-specific antibody titers, we showed that CIES against peptide-VLP conjugates could be overcome by high coupling densities, repeated injections and/or higher doses of conjugate vaccine. Furthermore we dissected VLP-specific immunity by adoptively transferring VLP-specific antibodies, B-cells or T(helper) cells separately into naïve mice and found that the observed CIES against peptide-VLP conjugates was mainly mediated by carrier-specific antibodies.

Combined vaccination against IL-5 and eotaxin blocks eosinophilia in mice

Interleukin-5 (IL-5) is a cytokine which is essential for the maturation of eosinophils in bone marrow and for their release into the blood. Eotaxin is a CC type chemokine implicated in the recruitment of eosinophils in a variety of inflammatory disorders. Since eosinophil-activity is governed by these two pathways, we targeted both IL-5 and eotaxin by active vaccination to block eosinophilia. We produced two vaccines by chemically cross-linking IL-5 or eotaxin to a virus-like particle (VLP) derived from the bacteriophage Qbeta, yielding highly repetitive arrays of these cytokines on the VLP surface. Both vaccines overcame self-tolerance and induced high antibody titers against the corresponding self-molecules in mice. Immunization with either of the two vaccines reduced eosinophilic inflammation of the lung in an ovalbumin (OVA) based mouse model of allergic airway inflammation. Animals immunized with the two vaccines at the same time developed high antibody titers against both cytokines and also reduced eosinophil-infiltration of the lung. These data demonstrate that targeting either IL-5 or eotaxin may lower eosinophilia. Simultaneous immunization against IL-5 and eotaxin demonstrates that such a therapeutic approach may be used to treat complex disorders in which multiple mediators are involved.

RANKL inhibition for the management of patients with benign metabolic bone disorders

The receptor activator of NF-kappaB ligand (RANKL) is a member of the TNF receptor superfamily, essential for osteoclastogenesis. It binds to its receptor activator of NF-kappaB on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, while it activates mature osteoclasts and inhibits their apoptosis. The effects of RANKL are counteracted by osteoprotegerin (OPG), a neutralizing decoy receptor. Derangement of the balance in RANKL/OPG action is implicated in the pathophysiology of metabolic bone diseases, including osteoporosis. Current therapies used to prevent or treat metabolic bone diseases are thought to act, at least in part, through modification of the RANKL/OPG dipole. The idea of using a molecule that could specifically bind and neutralize RANKL to decrease bone resorption and subsequent bone loss is appealing. Recombinant OPG was initially tested. Denosumab, a fully human monoclonal antibody against RANKL, is a promising antiresorptive agent under investigation. It rapidly decreases bone turnover markers resulting in a significant increase in bone mineral density and reduction in fracture risk. However, because receptor activator of NF-kappaB activation by RANKL is also essential for T-cell growth and dendritic-cell function, inhibition of its action could simultaneously affect the immune system, leading to susceptibility in infections or malignancies.

Displaying Fel d1 on virus-like particles prevents reactogenicity despite greatly enhanced immunogenicity: a novel therapy for cat allergy

Allergen-specific desensitization is the only disease-modifying therapy currently available for the treatment of allergies. These therapies require application of allergen over several years and some may induce life-threatening anaphylactic reactions. An ideal vaccine for desensitization should be highly immunogenic and should alleviate allergic symptoms upon few injections while being nonreactogenic. We describe such a vaccine for the treatment of cat allergy, consisting of the major cat allergen Fel d1 coupled to bacteriophage Qβ-derived virus-like particles (Qβ–Fel d1). Qβ–Fel d1 was highly immunogenic, and a single vaccination was sufficient to induce protection against type I allergic reactions. Allergen-specific immunoglobulin G antibodies were shown to be the critical effector molecules and alleviated symptoms by two distinct mechanisms. Although allergen-induced systemic basophil degranulation was inhibited in an FcγRIIb-dependent manner, inhibition of local mast cell degranulation in tissues occurred independently of FcγRIIb. In addition, treatment with Qβ–Fel d1 abolished IgE memory responses upon antigen recall. Despite high immunogenicity, the vaccine was essentially nonreactogenic and vaccination induced neither local nor systemic anaphylactic reactions in sensitized mice. Moreover, Qβ–Fel d1 did not induce degranulation of basophils derived from human volunteers with cat allergies. These data suggest that vaccination with Qβ–Fel d1 may be a safe and effective treatment for cat allergy.

Immunodrugs: therapeutic VLP-based vaccines for chronic diseases

Worldwide, the prevalence of noncommunicable chronic diseases is increasing. The use of vaccines to induce autoantibodies that neutralize disease-related proteins offers a means to effectively and affordably treat such diseases. Twenty vaccines designed to induce therapeutic autoantibodies were clinically tested in the past 12 years. Immunodrugs are therapeutic vaccines comprising virus-like particles (VLPs) covalently conjugated with self-antigens that induce neutralizing autoantibody responses. Four such VLP-based vaccines have been clinically tested and one has achieved proof of principle: a reduction of blood pressure in hypertensive patients. To facilitate preliminary clinical testing, novel nonclinical study programs have been developed. Safety study designs have considered the underlying B and T cell immunology and have examined potential toxicities of vaccine components and primary and secondary pharmacodynamic action of the vaccines.

Emerging applications of anticytokine vaccines

Most chronic inflammatory diseases have an unknown etiology but all involve cytokine cascade in their development. Several cytokines have been identified as major targets in various autoimmune diseases, resulting in the development of monoclonal antibodies against those cytokines. Even if monoclonal antibodies are indeed efficient, passive immunotherapies present some disadvantages and are expensive. To counter this, several strategies have been developed, including active immunotherapy, based on vaccination principles. The aim of such a strategy is to induce a B-cell response and to obtain autoantibodies able to neutralize the interaction of the self-cytokine to its receptor. Efficient vaccines have to induce a short-term response to avoid permanent inhibition of a given cytokine. This review focuses on the different therapeutic vaccination strategies with cytokines in preclinical studies; the benefit-risk ratio of such a strategy and the present development of clinical trials in some autoimmune diseases are also discussed.

Vaccination against GIP for the treatment of obesity

BACKGROUND

According to the WHO, more than 1 billion people worldwide are overweight and at risk of developing chronic illnesses, including cardiovascular disease, type 2 diabetes, hypertension and stroke. Current therapies show limited efficacy and are often associated with unpleasant side-effect profiles, hence there is a medical need for new therapeutic interventions in the field of obesity. Gastric inhibitory peptide (GIP, also known as glucose-dependent insulinotropic polypeptide) has recently been postulated to link over-nutrition with obesity. In fact GIP receptor-deficient mice (GIPR(-/-)) were shown to be completely protected from diet-induced obesity. Thus, disrupting GIP signaling represents a promising novel therapeutic strategy for the treatment of obesity.

METHODOLOGY/PRINCIPAL FINDINGS

In order to block GIP signaling we chose an active vaccination approach using GIP peptides covalently attached to virus-like particles (VLP-GIP). Vaccination of mice with VLP-GIP induced high titers of specific antibodies and efficiently reduced body weight gain in animals fed a high fat diet. The reduction in body weight gain could be attributed to reduced accumulation of fat. Moreover, increased weight loss was observed in obese mice vaccinated with VLP-GIP. Importantly, despite the incretin action of GIP, VLP-GIP-treated mice did not show signs of glucose intolerance.

CONCLUSIONS/SIGNIFICANCE

This study shows that vaccination against GIP was safe and effective. Thus active vaccination may represent a novel, long-lasting treatment for obesity. However further preclinical safety/toxicology studies will be required before the therapeutic concept can be addressed in humans.

Immunogenic display of diverse peptides on virus-like particles of RNA phage MS2

The high level of immunogenicity of peptides displayed in dense repetitive arrays on virus-like particles makes recombinant VLPs promising vaccine carriers. Here, we describe a platform for vaccine development based on the VLPs of RNA bacteriophage MS2. It serves for the engineered display of specific peptide sequences, but will also allow the construction of random peptide libraries from which specific binding activities can be recovered by affinity selection. Peptides representing the V3 loop of HIV gp120 and the ECL2 loop of the HIV coreceptor, CCR5, were inserted into a surface loop of MS2 coat protein. Both insertions disrupted coat VLP assembly, apparently by interfering with protein folding, but these defects were suppressed efficiently by genetically fusing coat protein's two identical polypeptides into a single-chain dimer. The resulting VLPs displayed the V3 and ECL2 peptides on their surfaces where they showed the potent immunogenicity that is the hallmark of VLP-displayed antigens. Experiments with random-sequence peptide libraries show the single-chain dimer to be highly tolerant of six, eight and ten amino acid insertions. MS2 VLPs support the display of a wide diversity of peptides in a highly immunogenic format, and they encapsidate the mRNAs that direct their synthesis, thus establishing the genotype/phenotype linkage necessary for recovery of affinity-selected sequences. The single-chain MS2 VLP therefore unites in a single structural platform the selective power of phage display with the high immunogenicity of VLPs.

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin regulation of bone remodeling in health and disease

Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor kappaB ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis.

Efficient induction of mucosal and systemic immune responses by virus-like particles administered intranasally: implications for vaccine design

Intranasal (i.n.) immunization aims to induce local as well as systemic immune responses. In the present study, we assessed a vaccine platform based on virus-like particles (VLP) derived from the RNA phage Qbeta for i.n. immunization. We found that both i.n. and subcutaneous (s.c.) administration of Qbeta-VLP elicited strong and comparable specific IgG responses in serum and lung. Surprisingly, both routes also induced high levels of specific IgA in serum. In contrast, only i.n. administration of Qbeta-VLP resulted in local IgA production in the lung. Efficient induction of B cell responses by i.n. administration of VLP was further supported by the presence of large numbers of germinal centers (GC) as well as memory B cells in the spleen and plasma cells in the bone marrow. Results obtained for the VLP itself could be extended to an antigen covalently attached to it. Specifically, i.n. immunization of mice with VLP displaying the influenza virus derived ectodomain of the M2 protein resulted in strong M2-specific antibody responses as well as anti-viral protection. In contrast, i.n. immunization with VLP displaying p33 peptide, the major CTL epitope of lymphocytic choriomeningitis virus, induced relatively inefficient cytotoxic T cell responses, resulting in low numbers of specific T cells and poor effector cell differentiation. Taken together, these results suggest that effective antibody-based vaccines are achievable by i.n. administration of Qbeta-VLP displaying specific antigens.

Pattern recognition by B cells: the role of antigen repetitiveness versus Toll-like receptors

Viruses induce excellent antibody responses due to several intrinsic features. Their repetitive, organised structure is optimal for the activation of the B cell receptor (BCR), leading to an increased humoral response and a decreased dependence on T cell help. Viruses also trigger Toll-like receptors (TLRs), which in addition to increasing overall Ig levels, drive the switch to the IgG2a isotype. This isotype is more efficient in viral and bacterial clearance and will activate complement, which in turn lowers the threshold of BCR activation. Exploiting these characteristics in vaccine design may help us to create vaccines which are as safe as a recombinant vaccine yet still as effective as a virus in inducing B cell responses.

Virus-like particles: flexible platforms for vaccine development

Virus-like particles (VLPs) consist of viral structural proteins that, when overexpressed, spontaneously self-assemble into particles that are antigenically indistinguishable from infectious virus or subviral particles. VLPs can be considered as dense, repetitive arrays of one or more protein subunits with properties that are highly advantageous for use as stand-alone vaccines or as vaccine platforms. This review discusses the development of VLP-based platform technologies for vaccines against pathogens, as well as nontraditional targets such as self-antigens involved in chronic diseases.

A Virus-Like Particle-Based Vaccine Selectively Targeting Soluble TNF-α Protects from Arthritis without Inducing Reactivation of Latent Tuberculosis

Neutralization of the proinflammatory cytokine TNF-alpha by mAbs or soluble receptors represents an effective treatment for chronic inflammatory disorders such as rheumatoid arthritis, psoriasis, or Crohn's disease. In this study, we describe a novel active immunization approach against TNF-alpha, which results in the induction of high titers of therapeutically active autoantibodies. Immunization of mice with virus-like particles of the bacteriophage Qbeta covalently linked to either the entire soluble TNF-alpha protein (Qbeta-C-TNF(1-156)) or a 20-aa peptide derived from its N terminus (Qbeta-C-TNF(4-23)) yielded specific Abs, which protected from clinical signs of inflammation in a murine model of rheumatoid arthritis. Whereas mice immunized with Qbeta-C-TNF(1-156) showed increased susceptibility to Listeria monocytogenes infection and enhanced reactivation of latent Mycobacterium tuberculosis, mice immunized with Qbeta-C-TNF(4-23) were not immunocompromised with respect to infection with these pathogens. This difference was attributed to recognition of both transmembrane and soluble TNF-alpha by Abs elicited by Qbeta-C-TNF(1-156), and a selective recognition of only soluble TNF-alpha by Abs raised by Qbeta-C-TNF(4-23). Thus, by specifically targeting soluble TNF-alpha, Qbeta-C-TNF(4-23) immunization has the potential to become an effective and safe therapy against inflammatory disorders, which might overcome the risk of opportunistic infections associated with the currently available TNF-alpha antagonists.

Vaccination against IL-17 suppresses autoimmune arthritis and encephalomyelitis

Interleukin 17 is a T cell-derived cytokine that induces the release of pro-inflammatory mediators in a wide range of cell types. Recently, a subset of IL-17-producing T helper cells (Th17) distinct from Th1 and Th2 cells has been described, which constitutes a new T cell polarization state. Aberrant Th17 responses and overexpression of IL-17 have been implicated in a number of autoimmune disorders including rheumatoid arthritis and multiple sclerosis. Molecules blocking IL-17 such as IL-17-specific monoclonal antibodies have proved to be effective in ameliorating disease in animal models. Hitherto, active immunization targeting IL-17 is an untried approach. Herein we explore the potential of neutralizing IL-17 by active immunization using virus-like particles conjugated with recombinant IL-17 (IL-17-VLP). Immunization with IL-17-VLP induced high levels of anti-IL-17 antibodies thereby overcoming natural tolerance, even in the absence of added adjuvant. Mice immunized with IL-17-VLP had lower incidence of disease, slower progression to disease and reduced scores of disease severity in both collagen-induced arthritis and experimental autoimmune encephalomyelitis. Active immunization against IL-17 therefore represents a novel therapeutic approach for the treatment of chronic inflammatory diseases.

Neutralization of IL-17 by active vaccination inhibits IL-23-dependent autoimmune myocarditis

The most common reason for heart failure in young adults is dilated cardiomyopathy often resulting from myocarditis. Clinical studies and animal models provide evidence that an autoimmune response against heart myosin is the underlying reason for the disease. IL-12 has been suggested to play a key role in development of experimental autoimmune myocarditis (EAM), as IL-12p40 and IL-12Rbeta1 knockouts are protected from disease. In this study, we have compared IL-12p40-/- mice, IL-12p35-/- mice and mice treated with a neutralizing IL-23 antibody in EAM and found that in fact IL-23, not IL-12, is responsible for inflammatory heart disease. However, these cytokines appear to have redundant activity for priming and expansion of autoreactive CD4 T cells, as specific T cell proliferation was only defective in the absence of both cytokines. IL-23 has been suggested to promote a pathogenic IL-17-producing T cell population. We targeted IL-17 by capitalizing on an active vaccination approach that effectively breaks B cell tolerance. Neutralization of IL-17 reduced myocarditis and heart autoantibody responses, suggesting that IL-17 is the critical effector cytokine responsible for EAM. Thus, targeting of IL-23 and IL-17 by passive and active vaccination strategies holds promise as a therapeutic approach to treat patients at risk for development of dilated cardiomyopathy.

A novel DNA vaccine targeting macrophage migration inhibitory factor protects joints from inflammation and destruction in murine models of arthritis

OBJECTIVE

Previous studies have demonstrated that neutralization of macrophage migration inhibitory factor (MIF) by anti-MIF antibodies decreases joint inflammation and destruction in a type II collagen-induced arthritis model in mice. The aim of this study was to develop and describe a simple and effective method of active immunization that induces anti-MIF autoantibodies, which may neutralize MIF bioactivity.

METHODS

We developed a MIF DNA vaccine by introducing oligonucleotides encoding a tetanus toxoid (TTX) Th cell epitope into the complementary DNA sequence of murine MIF. Mice were injected with this construct in conjunction with electroporation. The ability of this immunization to inhibit the development of collagen antibody-induced arthritis (CAIA) in BALB/c mice and spontaneous autoimmune arthritis in interleukin-1 receptor antagonist (IL-1Ra)-deficient mice was then evaluated.

RESULTS

Mice that received the MIF/TTX DNA vaccine developed high titers of autoantibodies that reacted to native MIF. Compared with unvaccinated mice, vaccinated mice also produced less serum tumor necrosis factor alpha after receiving an intravenous injection of lipopolysaccharide. In addition, vaccination with MIF/TTX DNA resulted in significant amelioration of both CAIA in BALB/c mice and symptoms of autoimmune arthritis in IL-1Ra-knockout mice.

CONCLUSION

These results suggest that MIF/TTX DNA vaccination may be useful for ameliorating the symptoms of rheumatoid arthritis.

Osteoclasts, rheumatoid arthritis, and osteoimmunology

PURPOSE OF REVIEW

Osteoclasts are terminally differentiated cells of the monocyte/macrophage lineage that resorb bone matrix. Bone destruction in rheumatoid arthritis is mainly attributable to the abnormal activation of osteoclasts, and studies on activation of osteoclasts by the immune system have led to the new research field called osteoimmunology. This interdisciplinary field is very important to biologic research and to the treatment of diseases associated with the bone and immune systems.

RECENT FINDINGS

The T-cell-mediated regulation of osteoclast differentiation is dependent on cytokines and membrane-bound factors expressed by T cells. The cross-talk between receptor activator of nuclear factor-kappaB ligand and interferon-gamma has been shown to be crucial for the regulation of osteoclast formation in arthritic joints. Recent studies indicate that an increasing number of immunomodulatory factors are associated with the regulation of bone metabolism: nuclear factor of activated T cells c1 has been shown to be the key transcription factor for osteoclastogenesis, the activation of which requires calcium signaling induced by the immunoglobulin-like receptors.

SUMMARY

New findings in osteoimmunology will be instrumental in the development of strategies for research into the treatment of various diseases afflicting the skeletal and immune systems.

A second vaccine revolution for the new epidemics of the 21st century

Non-communicable, chronic diseases are currently the major cause of death and disability worldwide, and many of these maladies have reached epidemic proportions. According to the World Health Organization (WHO) these disorders, including cardiovascular and respiratory diseases, diabetes, obesity and cancer, now account for about half of the global disease burden as well as deaths worldwide. The WHO identifies comparatively few risk factors, namely smoking, alcohol abuse, obesity, high cholesterol and high blood pressure, as the cause of many of these chronic conditions. A new class of medicines, based on vaccine approaches, are now in clinical trials and hold significant promise to treat both risk factors and their associated chronic diseases.

[New pathophysological relevant metabolic pathways in osteoporosis. Future innovative therapies?]

Osteoporosis is characterized by low bone mass and by changes in the microarchitecture of the bone. This leads to reduced bone stability and altered suscebtibility to fractures. Bone remodelling in healthy persons is characterized by a balance between bone resorption and bone formation. At the cellular level, bone remodelling is regulated by osteoclast and osteoblast activity. During bone loss, there is an imbalance, osteoclast activity being more pronounced. Therefore, the influende of estrogens, Wnt and the RANK/ RANKL/OPG system on osteoclastogenesis and osteoclast activity has been investigated. The RANK/RANKL/OPG-System is actively involved in the differentiation and function of osteoclasts and seems to play a central part in most pathophysiological mechanisms that are active in osteoporosis.