Novel birch pollen specific immunotherapy formulation based on contiguous overlapping peptides

Hot topics in allergen immunotherapy, 2023: Current status and future perspective

The importance of allergen immunotherapy (AIT) is multifaceted, encompassing both clinical and quality-of-life improvements and cost-effectiveness in the long term. Key mechanisms of allergen tolerance induced by AIT include changes in memory type allergen-specific T- and B-cell responses towards a regulatory phenotype with decreased Type 2 responses, suppression of allergen-specific IgE and increased IgG1 and IgG4, decreased mast cell and eosinophil numbers in allergic tissues and increased activation thresholds. The potential of novel patient enrolment strategies for AIT is taking into account recent advances in biomarkers discoveries, molecular allergy diagnostics and mobile health applications contributing to a personalized approach enhancement that can increase AIT efficacy and compliance. Artificial intelligence can help manage and interpret complex and heterogeneous data, including big data from omics and non-omics research, potentially predict disease subtypes, identify biomarkers and monitor patient responses to AIT. Novel AIT preparations, such as synthetic compounds, innovative carrier systems and adjuvants, are also of great promise. Advances in clinical trial models, including adaptive, complex and hybrid designs as well as real-world evidence, allow more flexibility and cost reduction. The analyses of AIT cost-effectiveness show a clear long-term advantage compared to pharmacotherapy. Important research questions, such as defining clinical endpoints, biomarkers of patient selection and efficacy, mechanisms and the modulation of the placebo effect and alternatives to conventional field trials, including allergen exposure chamber studies are still to be elucidated. This review demonstrates that AIT is still in its growth phase and shows immense development prospects.

Recombinant T-cell epitope conjugation: A new approach for Dermatophagoides hypoallergen design

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only clinical approach that can potentially cure some allergic diseases by inducing immunological tolerance. Dermatophagoides pteronyssinus is considered as the most important source of mite allergens worldwide, with high sensitization rates for the major allergens Der p 1, Der p 2 and Der p 23. The aim of this work is to generate a hypoallergenic hybrid molecule containing T-cell epitopes from these three major allergens.

METHODS

The hybrid protein termed Der p 2231 containing T-cell epitopes was purified by affinity chromatography. The human IgE reactivity was verified by comparing those with the parental allergens. The hybrid was also characterized immunologically through an in vivo mice model.

RESULTS

The hybrid rDer p 2231 stimulated in peripheral blood mononuclear cells (PBMCs) isolated from allergic patients with higher levels of IL- 2, IL-10, IL-15 and IFN-γ, as well as lower levels of IL-4, IL-5, IL-13, TNF-α and GM-CSF. The use of hybrid molecules as a therapeutic model in D. pteronyssinus allergic mice led to the reduction of IgE production and lower eosinophilic peroxidase activity in the airways. We found increased levels of IgG antibodies that blocked the IgE binding to the parental allergens in the serum of allergic patients. Furthermore, the stimulation of splenocytes from mice treated with rDer p 2231 induced higher levels of IL-10 and IFN-γ and decreased the secretion of IL-4 and IL-5, when compared with parental allergens and D. pteronyssinus extract.

CONCLUSIONS

rDer p 2231 has the potential to be used in AIT in patients co-sensitized with D. pteronyssinus major allergens, once it was able to reduce IgE production, inducing allergen-specific blocking antibodies, restoring and balancing Th1/Th2 immune responses, and inducing regulatory T-cells.

Preventive Administration of Non-Allergenic Bet v 1 Peptides Reduces Allergic Sensitization to Major Birch Pollen Allergen, Bet v 1

IgE-mediated allergy to birch pollen affects more than 100 million patients world-wide. Bet v 1, a 17 kDa protein is the major allergen in birch pollen responsible for allergic rhinoconjunctivitis and asthma in birch pollen allergic patients. Allergen-specific immunotherapy (AIT) based on therapeutic administration of Bet v 1-containing vaccines is an effective treatment for birch pollen allergy but no allergen-specific forms of prevention are available. We developed a mouse model for IgE sensitization to Bet v 1 based on subcutaneous injection of aluminum-hydroxide adsorbed recombinant Bet v 1 and performed a detailed characterization of the specificities of the IgE, IgG and CD4⁺ T cell responses in sensitized mice using seven synthetic peptides of 31-42 amino acids length which comprised the Bet v 1 sequence and the epitopes recognized by human CD4⁺ T cells. We then demonstrate that preventive systemic administration of a mix of synthetic non-allergenic Bet v 1 peptides to 3-4 week old mice significantly reduced allergic immune responses, including IgE, IgG, IgE-mediated basophil activation, CD4⁺ T cell and IL-4 responses to the complete Bet v 1 allergen but not to the unrelated major grass pollen allergen Phl p 5, without inducing Bet v 1-specific allergic sensitization or adaptive immunity. Our results thus demonstrate that early preventive administration of non-allergenic synthetic T cell epitope-containing allergen peptides could be a safe strategy for the prevention of allergen-specific IgE sensitization.

Identification of the Dominant T-Cell Epitopes of Lit v 1 Shrimp Major Allergen and Their Functional Overlap with Known B-Cell Epitopes

Development of efficient peptide-based immunotherapy for shrimp allergy relies on the identification of the dominant T-cell epitopes of its major allergen, tropomyosin. In this study, immunoinformatic tools, T-cell proliferation, cytokine release, IgG/IgE binding, and degranulation assays were used to identify and characterize the T-cell epitopes in Lit v 1 in comparison with previously validated B-cell epitopes. The results showed that of the six in silico predicted T-cell epitopes only one (T2: VQESLLKANIQLVEK, 60-74) promoted T-cell proliferation, the release of IL-2, and upregulated secretion of Th2-associated cytokines in the absence of IgG/IgE binding and degranulation activities. These findings support T2 as a candidate for the development of an efficient peptide-based vaccine for the immunotherapy for shrimp-allergic patients.

Advancement of antigen-specific immunotherapy: knowledge transfer between allergy and autoimmunity

Targeted restoration of immunological tolerance to self-antigens or innocuous environmental allergens represents the ultimate aim of treatment options in autoimmune and allergic disease. Antigen-specific immunotherapy (ASI) is the only intervention that has proven disease-modifying efficacy as evidenced by induction of long-term remission in a number of allergic conditions. Mounting evidence is now indicating that specific targeting of pathogenic T cells in autoinflammatory and autoimmune settings enables effective restoration of immune homeostasis between effector and regulatory cells and alters the immunological course of disease. Here, we discuss the key lessons learned during the development of antigen-specific immunotherapies and how these can be applied to inform future interventions. Armed with this knowledge and current high-throughput technology to track immune cell phenotype and function, it may no longer be a matter of ‘if’ but ‘when’ this ultimate aim of targeted tolerance restoration is realised.

DNA vaccines and recombinant allergens with reduced allergenic activity treat allergies

This review is intended to familiarize readers with major novel directions of developing allergy vaccines, their structure, as well as the mechanisms of forming a new immunological response in the course of the treating immunoglobulin E (IgE)-mediated allergic diseases. Currently, science offers a huge variety of new experimental forms of recombinant allergens with reduced allergenic activity and increased immunogenicity, or vice-versa, immune tolerance. Often, the mechanisms of their effect on the immune system are not fully understood. Scientific publications, including reviews covering this topic, allowed us identifying top priority areas in the development of allergy vaccines: recombinant hypoallergenic allergen derivatives, T cell epitope-based allergy vaccines, and B cell epitope-based allergy vaccines. In addition, the review discusses use of deoxyribonucleic acid (DNA) vaccines. Immunotherapy with DNA vaccines is the newest and least studied method of treating allergic diseases.

Bet v 1 contiguous overlapping peptides anchored to virosomes with TLR4 agonist enhance immunotherapy efficacy in mice

BACKGROUND

Whereas sublingual allergen immunotherapy (AIT) is routinely performed without any adjuvant or delivery system, there is a strong scientific rationale to better target the allergen(s) to oral dendritic cells known to support regulatory immune responses by using appropriate presentation platforms.

OBJECTIVE

To identify a safe presentation platform able to enhance allergen-specific tolerance induction.

METHODS

Virosomes with membrane-integrated contiguous overlapping peptides (COPs) of Bet v 1 and TLR4 or TLR2/TLR7 agonists were assessed for induction of Bet v 1-specific IgG1, IgG2a and IgE antibodies, hypersensitivity reactions and body temperature drop following subcutaneous injection in naive CD-1 mice. The most promising candidate, Bet v 1 COPs anchored to virosomes with membrane-incorporated TLR4 agonist (Vir.A-Bet v 1 COPs), was further evaluated by the sublingual route in a therapeutic setting in BALB/c mice with birch pollen-induced allergic asthma. Airway hyperresponsiveness, pro-inflammatory cells in bronchoalveolar lavages and polarization of Th cells in the lungs and spleen were then assessed.

RESULTS

Both types of adjuvanted virosomes coupled to Bet v 1 COPs triggered a boosted Th1 immunity. Given a more favourable safety profile, Vir.A-Bet v 1 COPs were further evaluated and shown to able to fully reverse asthma symptoms and lung inflammation in a sublingual therapeutic model of birch pollen allergy.

CONCLUSIONS AND CLINICAL RELEVANCE

We report herein for the first time on the capacity of a novel and safe presentation platform, that is virosomes with membrane-integrated TLR4 agonist, to improve dramatically sublingual AIT efficacy in a murine model due to its intrinsic dual properties of targeting and stimulating to further promote anti-allergic immune responses. As such, our study paves the ground for further clinical development of this allergen presentation platform for patients suffering from respiratory allergies.

Perspectives in Allergen-Specific Immunotherapy: Molecular Evolution of Peptide- and Protein-Based Strategies

Allergen-specific Immunotherapy (AIT), through repetitive subcutaneous or sublingual administrations of allergen extracts, represents up to now the unique treatment against allergic sensitizations. However, the clinical efficacy of AIT can be largely dependent on the quality of natural allergen extracts. Moreover, the long duration and adverse side effects associated with AIT negatively impact patient adherence. Tremendous progress in the field of molecular allergology has made possible the design of safer, shorter and more effective new immunotherapeutic approaches based on purified and characterized natural or recombinant allergen derivatives and peptides. This review will summarize the characteristics of these different innovative vaccines including their effects in preclinical studies and clinical trials.

Advances in Food Allergy Treatment

Food allergies represent life-threatening diseases which are increasing in prevalence with no definitive treatments currently in place. Current treatments are no more than preventative avoidance and symptom management. Research within the field has focused on therapeutic developments to modify the immune response in allergen-specific and non-specific methods. This review of the advances made in treatments intends to cover methods such as oral immunotherapy, modified food protein vaccines as well as the use of alternative medicine. Thus, this review aims to inform and further extend discussion surrounding the potential clinical applications as well as novel routes for further research into an, as of yet, unsolved question.

[Recombinant allergens, peptides, and virus-like particles for allergy immunotherapy]

Currently, extract-based therapeutic allergens from natural allergen sources (e.g., house dust mites, tree and grass pollen) are used for allergen-specific immunotherapy (AIT), the only causative therapy that can exhibit positive disease-modifying effects by tolerance induction and prevention of disease progression. Due to variations in the natural composition of the starting materials and different manufacturing processes, there are variations in protein content, allergen composition, and allergenic activity of similar products, which poses specific challenges for their standardization. The identification of the nucleotide sequences of allergenic proteins led to the development of molecular AIT approaches. This allows for the application of exclusively relevant structures as chemically synthesized peptides, recombinant single allergens, or molecules with hypoallergenic properties that potentially allow for an up-dosing with higher allergen-doses without allergic side effects leading more quickly to effective cumulative doses. Further modifications of AIT preparations to improve allergenic and immunogenic properties may be achieved, e.g., by including the use of virus-like particles (VLPs). To date, the herein described therapeutic approaches have been tested in clinical trials only. This article provides an overview of published molecular approaches for allergy treatment used in clinical AIT studies. Their added value and challenges compared to established therapeutic allergens are discussed. The aim of these approaches is to develop highly effective and well-tolerated AIT preparations with improved patient acceptance and adherence.

Recombinant allergens for immunotherapy: state of the art

PURPOSE OF REVIEW

More than 30 years ago, the first molecular structures of allergens were elucidated and defined recombinant allergens became available. We review the state of the art regarding molecular AIT with the goal to understand why progress in this field has been slow, although there is huge potential for treatment and allergen-specific prevention.

RECENT FINDINGS

On the basis of allergen structures, several AIT strategies have been developed and were advanced into clinical evaluation. In clinical AIT trials, promising results were obtained with recombinant and synthetic allergen derivatives inducing allergen-specific IgG antibodies, which interfered with allergen recognition by IgE whereas clinical efficacy could not yet be demonstrated for approaches targeting only allergen-specific T-cell responses. Available data suggest that molecular AIT strategies have many advantages over allergen extract-based AIT.

SUMMARY

Clinical studies indicate that recombinant allergen-based AIT vaccines, which are superior to existing allergen extract-based AIT can be developed for respiratory, food and venom allergy. Allergen-specific preventive strategies based on recombinant allergen-based vaccine approaches and induction of T-cell tolerance are on the horizon and hold promise that allergy can be prevented. However, progress is limited by lack of resources needed for clinical studies, which are necessary for the development of these innovative strategies.

Production of allergen-specific immunotherapeutic agents for the treatment of food allergy

Allergen-specific immunotherapy (IT) is emerging as a viable avenue for the treatment of food allergies. Clinical trials currently investigate raw or slightly processed foods as therapeutic agents, as trials using food-grade agents can be performed without the strict regulations to which conventional drugs are subjected. However, this limits the ability of standardization and may affect clinical trial outcomes and reproducibility. Herein, we provide an overview of methods used in the production of immunotherapeutic agents for the treatment of food allergies, including processed foods, allergen extracts, recombinant allergens, and synthetic peptides, as well as the physical and chemical processes for the reduction of protein allergenicity. Commercial interests currently favor producing standardized drug-grade allergen extracts for therapeutic use, and clinical trials are ongoing. In the near future, recombinant production could replace purification strategies since it allows the manufacturing of pure, native allergens or sequence-modified allergens with reduced allergenicity. A recurring issue within this field is the inadequate reporting of production procedures, quality control, product physicochemical characteristics, allergenicity, and immunological properties. This information is of vital importance in assessing therapeutic standardization and clinical safety profile, which are central parameters for the development of future therapeutic agents.

Next generation immunotherapy for tree pollen allergies

Tree pollen induced allergies are one of the major medical and public health burdens in the industrialized world. Allergen-Specific Immunotherapy (AIT) through subcutaneous injection or sublingual delivery is the only approved therapy with curative potential to pollen induced allergies. AIT often is associated with severe side effects and requires long-term treatment. Safer, more effective and convenient allergen specific immunotherapies remain an unmet need. In this review article, we discuss the current progress in applying protein and peptide-based approaches and DNA vaccines to the clinical challenges posed by tree pollen allergies through the lens of preclinical animal models and clinical trials, with an emphasis on the birch and Japanese red cedar pollen induced allergies.

A randomized, double-blind, placebo-controlled, dose-finding trial with Lolium perenne peptide immunotherapy

Background

A novel subcutaneous allergen immunotherapy formulation (gpASIT+™) containing Lolium perenne peptides (LPP) and having a short up‐dosing phase has been developed to treat grass pollen–induced seasonal allergic rhinoconjunctivitis. We investigated peptide immunotherapy containing the hydrolysate from perennial ryegrass allergens for the optimum dose in terms of clinical efficacy, immunogenicity and safety.

Methods

This prospective, double‐blind, placebo‐controlled, phase IIb, parallel, four‐arm, dose‐finding study randomized 198 grass pollen–allergic adults to receive placebo or cumulative doses of 70, 170 or 370 μg LPP. All patients received weekly subcutaneous injections, with the active treatment groups reaching assigned doses within 2, 3 and 4 weeks, respectively. Efficacy was assessed by comparing conjunctival provocation test (CPT) reactions at baseline, after 4 weeks and after completion. Grass pollen–specific immunoglobulins were analysed before and after treatment.

Results

Conjunctival provocation test (CPT) response thresholds improved from baseline to V7 by at least one concentration step in 51.2% (170 μg; P = .023), 46.3% (370 μg), and 38.6% (70 μg) of patients receiving LPP vs 25.6% of patients receiving placebo (modified per‐protocol set). Also, 39% of patients in the 170‐μg group became nonreactive to CPT vs 18% in the placebo group. Facilitated allergen‐binding assays revealed a highly significant (P < .001) dose‐dependent reduction in IgE allergen binding across all treatment groups (70 μg: 17.1%; 170 μg: 18.8%; 370 μg: 26.4%). Specific IgG₄ levels increased to 1.6‐fold (70 μg), 3.1‐fold (170 μg) and 3.9‐fold (370 μg) (mPP).

Conclusion

Three‐week immunotherapy with 170 μg LPP reduced CPT reactivity significantly and increased protective specific antibodies.

Modified Allergens for Immunotherapy

PURPOSE OF REVIEW

During the past few decades, modified allergens have been developed for use in allergen-specific immunotherapy (AIT) with the aim to improve efficacy and reduce adverse effects. This review aims to provide an overview of the different types of modified allergens, their mechanism of action and their potential for improving AIT.

RECENT FINDINGS

In-depth research in the field of allergen modifications as well as the advance of recombinant DNA technology have paved the way for improved diagnosis and research on human allergic diseases. A wide range of structurally modified allergens has been generated including allergen peptides, chemically altered allergoids, adjuvant-coupled allergens, and nanoparticle-based allergy vaccines. These modified allergens show promise for the development of AIT regimens with improved safety and long-term efficacy. Certain modifications ensure reduced IgE reactivity and retained T cell reactivity, which facilities induction of immune tolerance to the allergen. To date, multiple clinical trials have been performed using modified allergens. Promising results were obtained for the modified cat, grass and birch pollen, and house dust mite allergens. The use of modified allergens holds promise for improving AIT efficacy and safety. There is however a need for larger clinical studies to reliably assess the added benefit for the patient of using modified allergens for AIT.

Safety and efficacy of immunotherapy with the recombinant B-cell epitope-based grass pollen vaccine BM32

Background

BM32 is a grass pollen allergy vaccine based on recombinant fusion proteins consisting of nonallergenic peptides from the IgE-binding sites of the 4 major grass pollen allergens and the hepatitis B preS protein.

Objective

We sought to study the safety and clinical efficacy of immunotherapy (allergen immunotherapy) with BM32 in patients with grass pollen–induced rhinitis and controlled asthma.

Methods

A double-blind, placebo-controlled, multicenter allergen immunotherapy field study was conducted for 2 grass pollen seasons. After a baseline season, subjects (n = 181) were randomized and received 3 preseasonal injections of either placebo (n = 58) or a low dose (80 μg, n = 60) or high dose (160 μg, n = 63) of BM32 in year 1, respectively, followed by a booster injection in autumn. In the second year, all actively treated subjects received 3 preseasonal injections of the BM32 low dose, and placebo-treated subjects continued with placebo. Clinical efficacy was assessed by using combined symptom medication scores, visual analog scales, Rhinoconjunctivitis Quality of Life Questionnaires, and asthma symptom scores. Adverse events were graded according to the European Academy of Allergy and Clinical Immunology. Allergen-specific antibodies were determined by using ELISA, ImmunoCAP, and ImmunoCAP ISAC.

Results

Although statistical significance regarding the primary end point was not reached, BM32-treated subjects, when compared with placebo-treated subjects, showed an improvement regarding symptom medication, visual analog scale, Rhinoconjunctivitis Quality of Life Questionnaire, and asthma symptom scores in both treatment years. This was accompanied by an induction of allergen-specific IgG without induction of allergen-specific IgE and a reduction in the seasonally induced increase in allergen-specific IgE levels in year 2. In the first year, more grade 2 reactions were observed in the active (n = 6) versus placebo (n = 1) groups, whereas there was almost no difference in the second year.

Conclusions

Injections of BM32 induced allergen-specific IgG, improved clinical symptoms of seasonal grass pollen allergy, and were well tolerated.

Perspectives in allergen immunotherapy: 2017 and beyond

The Future of the Allergists and Specific Immunotherapy (FASIT) workshop provides a regular platform for global experts from academia, allergy clinics, regulatory authorities and industry to review developments in the field of allergen immunotherapy (AIT). The most recent meeting, held in February 2017, had two main themes: advances in AIT and hot topics in AIT from the regulatory point of view. The first theme covered opportunities for personalized AIT, advances in adjuvants and delivery systems, and the development of new molecules and future vaccines for AIT. Key topics in the second part of the meeting were the effects of the enactment of European Directive 2001/83 on the availability of allergens for therapy and diagnosis across the EU, the challenges of conducting Phase 3 studies in the field, the future role of allergen exposure chambers in AIT studies and specific considerations in performing AIT studies in the paediatric population. Finally, the group highlighted the forthcoming EAACI guidelines and their particular importance for the standardization of practice in the treatment of allergies. This review presents a comprehensive insight into those panel discussions and highlights unmet needs and also possible solutions to them for the future.

Utility and Comparative Efficacy of Recombinant Allergens Versus Allergen Extract

Allergy immunotherapy (AIT) is the only disease-modifying therapy for the treatment of allergic diseases. Although its efficacy and utility are well-established, the potential for serious adverse events, cumbersome and lengthy treatment protocols, and variability of natural allergen preparations have limited its widespread application. Recent advances in recombinant technology have opened new avenues for the development of AIT vaccines. The purpose of this review is to highlight recent evidence on the use of novel recombinant vaccines and review the mechanisms, efficacy, safety, and limitations of AIT. Emerging evidence suggests that recombinant vaccines may provide a viable treatment alternative that improves on the limitations of natural extract therapy while maintaining efficacy.

Novel approaches and perspectives in allergen immunotherapy

In this review, we report on relevant current topics in allergen immunotherapy (AIT) which were broadly discussed during the first Aarhus Immunotherapy Symposium (Aarhus, Denmark) in December 2015 by leading clinicians, scientists and industry representatives in the field. The aim of this symposium was to highlight AIT-related aspects of public health, clinical efficacy evaluation, mechanisms, development of new biomarkers and an overview of novel therapeutic approaches. Allergy is a public health issue of high socioeconomic relevance, and development of evidence-based action plans to address allergy as a public health issue ought to be on national and regional agendas. The underlying mechanisms are in the focus of current research that lays the ground for innovative therapies. Standardization and harmonization of clinical endpoints in AIT trials as well as current knowledge about potential biomarkers have substantiated proof of effectiveness of this disease-modifying therapeutic option. Novel treatments such as peptide immunotherapy, intralymphatic immunotherapy and use of recombinant allergens herald a new age in which AIT may address treatment of allergy as a public health issue by reaching a large fraction of patients.

Therapeutic vaccines for allergic disease

Allergic diseases are highly prevalent worldwide and affect all age groups, contributing to a high personal and socioeconomic burden. Treatment with an “allergy vaccine” or allergen immunotherapy aims to provide long-lasting benefits by inducing unresponsiveness to the relevant antigen. The consequences of the therapy are considered disease modifying and range from dampening of the immediate immune responses to the reduction of secondary tissue remodeling. Furthermore, allergen immunotherapy interventions have a potential to slow or cease the development of additional allergic manifestations with a long-term overall effect on morbidity and quality of life. Here, we review proposed mechanisms underlying the therapeutic effects of immunotherapy for allergic diseases. Further, we discuss both standard and novel approaches and possible future directions in the development of allergen immunotherapy.

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides – leading to the formation of altered peptide ligands (APLs) – might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

Efficacy of a therapeutic treatment using gas-filled microbubble-associated phospholipase A2 in a mouse model of honeybee venom allergy

BACKGROUND

Venom immunotherapy is efficient to desensitize people suffering from insect sting allergies. However, the numerous injections required over several years and important risks of severe side reactions complicate the widespread use of immunotherapy. In the search for novel approaches to blunt the overwhelming pro-allergic Th2 response, we evaluated the therapeutic efficacy of a treatment based on a denatured form of the major allergen, phospholipase A2, associated with microbubbles (PLA2denat -MB) in a mouse model of honeybee venom allergy.

METHODS

Antibodies measured by ELISA, T-cell responses assessed by CFSE-based proliferation assays and ELISA, and basophil degranulation were examined after PLA2denat -MB-based therapeutic treatment of sensitized mice. Mice were challenged with a lethal dose of PLA2 to evaluate protection against anaphylaxis.

RESULTS

Therapeutic subcutaneous administration of two different PLA2denat -MB formulations, in contrast to PLA2denat alone, reduced allergic symptoms and protected all mice from anaphylaxis-mediated death after allergen challenge. At the functional level, the use of PLA2denat decreased IgE-mediated basophil degranulation as compared to the native form of the allergen. In comparison with PLA2denat alone, both PLA2denat -MB formulations decreased allergen-specific Th2 CD4 T-cell reactivity. At the mechanistic level, PLA2denat -MB containing 20% palmitic acid and PEG induced PLA2-specific IgA and increased Foxp3(+) Treg frequencies and TGF-β production, whereas the formulation bearing 80% palmitic acid triggered the production of IFN-γ, IgG2a, and IgG3.

CONCLUSIONS

In contrast to conventional PLA2 subcutaneous immunotherapy, the therapeutic administration of PLA2-MB treatment to mice that already had established allergy to PLA2 protects all subsequently challenged animals.

Efficacy of 2 months of allergen-specific immunotherapy with Bet v 1-derived contiguous overlapping peptides in patients with allergic rhinoconjunctivitis: Results of a phase IIb study

BACKGROUND

An immunotherapy formulation consisting of 3 contiguous overlapping peptides (COPs) derived from Bet v 1, the major birch pollen allergen, showed good clinical tolerability in a previous phase I/IIa clinical trial.

OBJECTIVES

We sought to evaluate the efficacy and safety of allergen-specific immunotherapy using 2 dose regimens of Bet v 1 COPs versus placebo in subjects with birch pollen-induced allergic rhinoconjunctivitis.

METHODS

A randomized, double-blind, placebo-controlled phase IIb clinical trial was performed to assess the efficacy of Bet v 1 COP immunotherapy during the 2013 birch pollen season. Before the season, Bet v 1 COPs (50 and 100 μg in aluminum hydroxide) or placebo (saline and aluminum hydroxide) were administered as 5 subcutaneous injections to 239 adults with allergic rhinoconjunctivitis to birch pollen. Bet v 1 COPs at 25 or 50 μg were administered on day 1, and 50 or 100 μg was administered on days 8, 15, 29, and 57, respectively. Patients were monitored for adverse events during the treatment period and assessed for combined rhinoconjunctivitis symptom and medication scores, as well as quality of life.

RESULTS

Rhinoconjunctivitis symptom and medication scores improved in both Bet v 1 COP-treated groups, reaching statistical significance over placebo in the 50-μg group (least squares mean, -0.23; 26% improvement; P = .015). Both active groups showed significant improvement in quality of life and nighttime nasal symptom scores, supporting the primary end point findings. Bet v 1 COP injections were well tolerated, with a higher frequency of systemic adverse events in the 100-μg group.

CONCLUSION

Two months of preseasonal immunotherapy with 3 COPs derived from Bet v 1 at a 50-μg dose showed promising efficacy, small risk for systemic reactions, and immunomodulatory changes in this single-season, dose-finding, phase IIb trial in patients allergic to birch pollen.

Allergen immunotherapy for birch pollen-allergic patients: recent advances

As of today, allergen immunotherapy is performed with aqueous natural allergen extracts. Recombinant allergen vaccines are not yet commercially available, although they could provide patients with well-defined and highly consistent drug substances. As Bet v 1 is the major allergen involved in birch pollen allergy, with more than 95% of patients sensitized to this allergen, pharmaceutical-grade recombinant Bet v 1-based vaccines were produced and clinically tested. Herein, we compare the clinical results and modes of action of treatments based on either a birch pollen extract or recombinant Bet v 1 expressed as hypoallergenic or natural-like molecules. We also discuss the future of allergen immunotherapy with improved drugs intended for birch pollen-allergic patients suffering from rhinoconjunctivitis.

Allergen Immunotherapy: Past, Present, and Future

Allergen-specific immunotherapy (AIT), although in clinical use for more than a century, is still the only causal treatment of allergic diseases. The safety and efficacy of AIT has been demonstrated in a large number of clinical trials. In addition to allergy symptom reduction AIT plays an essential role in preventing new allergies and asthma and shows long-term effects after discontinuation of treatment. Ideally, it is capable of curing allergy. However, AIT is not effective in all allergic individuals and is not equally effective in the treatment of various hypersensitivities to different allergens. For many years, the route of administration and the vaccine compositions have been evolving. Still there is a strong need for research in the field of new AIT modalities to increase its effectiveness and safety. Growing evidence on immunological effects of AIT, especially new T cell subsets involved in antigen/allergen tolerance, provides novel concepts for safer and more effective vaccination. Pharmacoeconomic studies have demonstrated a clear advantage of AIT over pharmacologic therapies.

T Cell Epitope Peptide Therapy for Allergic Diseases

Careful selection of dominant T cell epitope peptides of major allergens that display degeneracy for binding to a wide array of MHC class II molecules allows induction of clinical and immunological tolerance to allergen in a refined treatment strategy. From the original concept of peptide-induced T cell anergy arising from in vitro studies, proof-of-concept murine models and flourishing human trials followed. Current randomized, double-blind, placebo-controlled clinical trials of mixtures of T cell-reactive short allergen peptides or long contiguous overlapping peptides are encouraging with intradermal administration into non-inflamed skin a preferred delivery. Definitive immunological mechanisms are yet to be resolved but specific anergy, Th2 cell deletion, immune deviation, and Treg induction seem implicated. Significant efficacy, particularly with short treatment courses, in a range of aeroallergen therapies (cat, house dust mite, grass pollen) with inconsequential non-systemic adverse events likely heralds a new class of therapeutic for allergy, Synthetic Peptide Immuno-Regulatory Epitopes (SPIRE).

Novel immunotherapy vaccine development

PURPOSE OF REVIEW

Allergen-specific immunotherapy is the only curative treatment for allergic diseases. In spite of the great progress in both vaccine development and the methods of allergen immunotherapy (AIT) in recent years, several key problems related to limited efficacy, side-effects, low patient adherence and the relatively high costs due to the long duration (3-5 years) remain to be solved. The current approaches aiming at optimization of AIT are reviewed, including both conceptual studies in experimental models and proof-of-concept - as well as large, multicenter clinical studies.

RECENT FINDINGS

The most promising approaches to improve efficacy and safety of vaccine-based AIT include bypassing IgE binding and targeting allergen-specific T cells using hypoallergenic recombinant allergen derivatives and immunogenic peptides, the use of new adjuvants and stimulators of the innate immune response, the fusion of allergens to immune modifiers and peptide carrier proteins and new routes of vaccine administration.

SUMMARY

The cloning of allergen proteins and genetic engineering enabled the production of vaccines that have well defined molecular, immunologic and biologic characteristics as well as modified molecular structure. These new compounds along with new immunization protocols can bring us closer to the ultimate goal of AIT, that is, complete cure of a large number of allergic patients.

Immunoregulatory T cell epitope peptides: the new frontier in allergy therapy

Allergen immunotherapy (AIT) has been practised since 1911 and remains the only therapy proven to modify the natural history of allergic diseases. Although efficacious in carefully selected individuals, the currently licensed whole allergen extracts retain the risk of IgE-mediated adverse events, including anaphylaxis and occasionally death. This together with the need for prolonged treatment regimens results in poor patient adherence. The central role of the T cell in orchestrating the immune response to allergen informs the choice of T cell targeted therapies for down-regulation of aberrant allergic responses. Carefully mapped short synthetic peptides that contain the dominant T cell epitopes of major allergens and bind to a diverse array of HLA class II alleles, can be delivered intradermally into non-inflamed skin to induce sustained clinical and immunological tolerance. The short peptides from allergenic proteins are unable to cross-link IgE and possess minimal inflammatory potential. Systematic progress has been made from in vitro human models of allergen T cell epitope-based peptide anergy in the early 1990s, through proof-of-concept murine allergy models and early human trials with longer peptides, to the current randomized, double-blind, placebo-controlled clinical trials with the potential new class of synthetic short immune-regulatory T cell epitope peptide therapies. Sustained efficacy with few adverse events is being reported for cat, house dust mite and grass pollen allergy after only a short course of treatment. Underlying immunological mechanisms remain to be fully delineated but anergy, deletion, immune deviation and Treg induction all seem contributory to successful outcomes, with changes in IgG4 apparently less important compared to conventional AIT. T cell epitope peptide therapy is promising a safe and effective new class of specific treatment for allergy, enabling wider application even for more severe allergic diseases.

Peptide Immunotherapy in Vaccine Development: From Epitope to Adjuvant

Vaccines are designed to educate the host immune system to prevent infectious disease or to fight against various diseases such as cancers. Peptides were first employed to provide specific immune responses while minimizing unintended allergenic or reactogenic adverse effects. Discoveries of virus or cancer-specific antigens and the advanced knowledge of immunology accelerate the peptide vaccine development. Despite the overwhelming research pipelines, a very few of them reached to market approvals or phase III clinical trials, because of the lack of efficacy. Several strategies for the next generation peptide vaccines are devised to overcome the weak immunogenicity and the poor delivery. In this review, we discuss the new promising strategies of peptide vaccine development which are recently developed in preclinical and/or clinical stage focusing the roles of peptides in the vaccine formulation from epitope to adjuvant. Additionally, we discuss the future perspectives of peptide vaccine and immunotherapy.

Immunotherapy with B cell epitopes ameliorates inflammatory responses in Balb/c mice

Osmotin, a protein from the pathogenesis-related family (PR-5), has been identified as an allergen based on in-silico and in-vitro studies. In the present study, three B cell epitopes of osmotin with single and double amino acid modifications were studied for immunotherapy in a murine model. The single-modification peptides (P-1-1, P-2-1 and P-3-1) and double-modification peptides (P-1-2, P-2-2 and P-3-2) showed significantly lower immunoglobulin (Ig)E binding with patients' sera compared to osmotin (P < 0·01). These peptides showed reduced IgE binding compared to the unmodified peptides (B cell epitopes) P-1, P-2 and P-3. Among the modified peptides, P-2-1, P-3-1, P-2-2 and P-3-2 showed significant reduction in IgE binding and were used for immunotherapy in mice. The sera of mice group treated with peptides showed a significant increase in IgG2a level and a significant decrease in IgE and IgG1 levels (P < 0·05). The mice that received peptide immunotherapy showed a shift from a T helper type 2 (Th2) to Th1 type where interferon (IFN)-γ and interleukin (IL)-10 levels were elevated, with a significant increase in groups treated with peptides P-3-1 and P-3-2 (P < 0·05). There was a reduction in the IL-4 and IL-5 levels in bronchoalveolar lavage fluid (BALF) in the peptide-treated mice groups. Total cell count and eosinophil count in BALF of the peptide-treated groups was also reduced compared to the phosphate-buffered saline (PBS)-treated group. Lung histology showed a significant reduction in cellular infiltrate in mice treated with P-2-2 and P-3-2 compared to PBS. In conclusion, peptides P-2-2 and P-3-2 lowered inflammatory responses and induced a Th1 response in mice.

Modified allergens and their potential to treat allergic disease

Allergen-specific immunotherapy is the only treatment of allergic diseases that aims at modifying the underlying immune mechanism. Current protocols are long and at risk of anaphylactic reactions. The main aim of current research is decreasing the risk of side effects and increasing efficacy, in particular targeting reduction of treatment duration. Since the advent of molecular biology, extracts can be replaced by recombinant hypo-allergens, peptides, or fusion proteins. In addition, different routes of administration are being pursued as well as the addition of new adjuvants that are targeted at skewing the immune system away from a Th2 to a more Th1 or regulatory T cell phenotype. In this review, we summarize the recent advances in this field focusing on the allergen modifications and new adjuvants.

Recombinant allergens for pollen immunotherapy

Specific immunotherapy (IT) represents the only potentially curative therapeutic intervention of allergic diseases capable of suppressing allergy-associated symptoms not only during treatment, but also after its cessation. Presently, IT is performed with allergen extracts, which represent a heterogeneous mixture of allergenic, as well as nonallergenic, compounds of a given allergen source. To overcome many of the problems associated with extract-based IT, strategies based on the use of recombinant allergens or derivatives thereof have been developed. This review focuses on recombinant technologies to produce allergy therapeuticals, especially for allergies caused by tree, grass and weed pollen, as they are among the most prevalent allergic disorders affecting the population of industrialized societies. The reduction of IgE-binding of recombinant allergen derivatives appears to be mandatory to increase the safety profile of vaccine candidates. Moreover, increased immunogenicity is expected to reduce the dosage regimes of the presently cumbersome treatment. In this regard, it has been convincingly demonstrated in animal models that hypoallergenic molecules can be engineered to harbor inherent antiallergenic immunologic properties. Thus, strategies to modulate the allergenic and immunogenic properties of recombinant allergens will be discussed in detail. In recent years, several successful clinical studies using recombinant wild-type or hypoallergens as active ingredients have been published and, currently, novel treatment forms with higher safety and efficacy profiles are under investigation in clinical trials. These recent developments are summarized and discussed.

Molecular approach to allergy diagnosis and therapy

Presently, allergy diagnosis and therapy procedures are undergoing a transition phase in which allergen extracts are being step-by-step replaced by molecule-based products. The new developments will allow clinicians to obtain detailed information on sensitization patterns, more accurate interpretation of allergic symptoms, and thus improved patients' management. In this respect, recombinant technology has been applied to develop this new generation of molecule-based allergy products. The use of recombinant allergens allows full validation of identity, quantity, homogeneity, structure, aggregation, solubility, stability, IgE-binding and the biologic potency of the products. In contrast, such parameters are extremely difficult to assay and standardize for extract-based products. In addition to the possibility of bulk production of wild type molecules for diagnostic purposes, recombinant technology opened the possibility of developing safer and more efficacious products for allergy therapy. A number of molecule-based hypoallergenic preparations have already been successfully evaluated in clinical trials, bringing forward the next generation of allergy vaccines. In this contribution, we review the latest developments in allergen characterization, molecule-based allergy diagnosis, and the application of recombinant allergens in therapeutic setups. A comprehensive overview of clinical trials using recombinant allergens as well as synthetic peptides is presented.

Immunotherapy of type-1 allergies with virus-like particles and CpG-motifs

Immunotherapy of type-I-allergies is regarded as the most efficient treatment option besides allergen avoidance. Different forms of allergen preparations are used as well as different routes of application. Virus-like particles 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 immune cell activation. This article will focus on the function of virus-like particles loaded with DNA rich in CpG-motifs and discuss clinical experience in treatment of allergic rhinitis. Evidence will be presented that clinically effective treatment can be obtained even in the absence of allergens. Results encourage further investigation of virus-like particles and CpG-motifs in immunotherapy, either as a stand alone product, or as adjuvants for allergen-specific immunotherapy.

Immunotherapy in allergy and cellular tests: state of art

The basophil activation test (BAT) is an in vitro assay where the activation of basophils upon exposure to various IgE-challenging molecules is measured by flow cytometry. It is a cellular test able to investigate basophil behavior during allergy and allergy immunotherapy. A panoply of critical issues and suggestive advances have rendered this assay a promising yet puzzling tool to endeavor a full comprehension of innate immunity of allergy desensitization and manage allergen or monoclonal anti-IgE therapy. In this review a brief state of art of BAT in immunotherapy is described focusing onto the analytical issue pertaining BAT performance in allergy specific therapy.

Molecular biomarkers for grass pollen immunotherapy

Grass pollen allergy represents a significant cause of allergic morbidity worldwide. Component-resolved diagnosis biomarkers are increasingly used in allergy practice in order to evaluate the sensitization to grass pollen allergens, allowing the clinician to confirm genuine sensitization to the corresponding allergen plant sources and supporting an accurate prescription of allergy immunotherapy (AIT), an important approach in many regions of the world with great plant biodiversity and/or where pollen seasons may overlap. The search for candidate predictive biomarkers for grass pollen immunotherapy (tolerogenic dendritic cells and regulatory T cells biomarkers, serum blocking antibodies biomarkers, especially functional ones, immune activation and immune tolerance soluble biomarkers and apoptosis biomarkers) opens new opportunities for the early detection of clinical responders for AIT, for the follow-up of these patients and for the development of new allergy vaccines.

Allergen Peptides, Recombinant Allergens and Hypoallergens for Allergen-Specific Immunotherapy

Allergic diseases are among the most common health issues worldwide. Specific immunotherapy has remained the only disease-modifying treatment, but it is not effective in all patients and may cause side effects. Over the last 25 years, allergen molecules from most prevalent allergen sources have been isolated and produced as recombinant proteins. Not only are these molecules useful in improved allergy diagnosis, but they also have the potential to revolutionize the treatment of allergic disease by means of immunotherapy. Panels of unmodified recombinant allergens have already been shown to effectively replace natural allergen extracts in therapy. Through genetic engineering, several molecules have been designed with modified immunological properties. Hypoallergens have been produced that have reduced IgE binding capacity but retained T cell reactivity and T cell peptides which stimulate allergen-specific T cells, and these have already been investigated in clinical trials. New vaccines have been recently created with both reduced IgE and T cell reactivity but retained ability to induce protective allergen-specific IgG antibodies. The latter approach works by fusing per se non-IgE reactive peptides derived from IgE binding sites of the allergens to a virus protein, which acts as a carrier and provides the T-cell help necessary for immune stimulation and protective antibody production. In this review, we will highlight the different novel approaches for immunotherapy and will report on prior and ongoing clinical studies.