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

A, Hussain SM, Viswanad V, Nasr MH, Sahu RK, Khan J. Modulation of immune response by nanoparticle-based immunotherapy against food allergens

The increasing prevalence of food allergies worldwide and the subsequent life-threatening anaphylactic reactions often have sparse treatment options, providing only symptomatic relief. Great strides have been made in research and in clinics in recent years to offer novel therapies for the treatment of allergic disorders. However, current allergen immunotherapy has its own shortcomings in terms of long-term efficacy and safety, due to the local side effects and the possibility of anaphylaxis. Allergen-specific immunotherapy is an established therapy in treating allergic asthma, allergic rhinitis, and allergic conjunctivitis. It acts through the downregulation of T cell, and IgE-mediated reactions, as well as desensitization, a process of food tolerance without any allergic events. This would result in a protective reaction that lasts for approximately 3 years, even after the withdrawal of therapy. Furthermore, allergen-specific immunotherapy also exploits several routes such as oral, sublingual, and epicutaneous immunotherapy. As the safety and efficacy of allergen immunotherapy are still under research, the exploration of newer routes such as intra-lymphatic immunotherapy would address unfulfilled needs. In addition, the existence of nanoparticles can be exploited immensely in allergen immunotherapy, which would lead to safer and efficacious therapy. This manuscript highlights a novel drug delivery method for allergen-specific immunotherapy that involves the administration of specific allergens to the patients in gradual increasing doses, to induce desensitization and tolerance, as well as emphasizing different routes of administration, mechanism, and the application of nanoparticles in allergen-specific immunotherapy.

Future directions in allergen immunotherapy

Both subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) are effective clinically against allergic rhinitis and allergic asthma, and modify the underlying immunologic abnormalities. Despite this, many patients who could benefit from receiving SCIT and SLIT do not because of concerns about safety and the inconvenience in receiving SCIT, and the long duration of treatment with both, 3-4 years being required for lasting benefit. Attempts to improve the efficacy and safety, and to shorten the course of allergen immunotherapy have taken many approaches. Some approaches have generated great enthusiasm, only to fail in larger trials and be discarded. Other approaches show some promise but perhaps not enough to achieve regulatory approval. Those approaches that seem to have the best chance of becoming available in the next few years include the following: intralymphatic and epicutaneous immunotherapy, vitamin D in patients with insufficient serum 25 hydroxy vitamin D, probiotics, and allergoids, but all require further studies before being ready for nonexperimental use or, where necessary, for regulatory approval.

Peptide Allergen Immunotherapy: A New Perspective in Olive-Pollen Allergy

Allergic diseases are highly prevalent disorders, mainly in industrialized countries where they constitute a high global health problem. Allergy is defined as an immune response “shifted toward a type 2 inflammation” induced by the interaction between the antigen (allergen) and IgE antibodies bound to mast cells and basophils that induce the release of inflammatory mediators that cause the clinical symptoms. Currently, allergen-specific immunotherapy (AIT) is the only treatment able to change the course of these diseases, modifying the type 2 inflammatory response by an allergenic tolerance, where the implication of T regulatory (Treg) cells is considered essential. The pollen of the olive tree is one of the most prevalent causes of respiratory allergic diseases in Mediterranean countries, inducing mainly nasal and conjunctival symptoms, although, in areas with a high antigenic load, olive-tree pollen may cause asthma exacerbation. Classically, olive-pollen allergy treatment has been based on specific immunotherapy using whole-olive pollen extracts. Despite extracts standardization, the effectiveness of this strategy varies widely, therefore there is a need for more effective AIT approaches. One of the most attractive is the use of synthetic peptides representing the B- or T-cell epitopes of the main allergens. This review summarizes experimental evidence of several T-cell epitopes derived from the Ole e 1 sequence to modulate the response to olive pollen in vitro, associated with several possible mechanisms that these peptides could be inducing, showing their usefulness as a safe preventive tool for these complex diseases.

Mapping Human Monoclonal IgE Epitopes on the Major Dust Mite Allergen Der p 2

IgE Abs drive the symptoms of allergic disease upon cross-linking allergens on mast cells or basophils. If the IgE binding sites on the allergens could be identified, it may be useful for creating new forms of immunotherapy. However, direct knowledge of the human IgE (hIgE) epitopes is limited because of the very low frequency of IgE-producing B cells in blood. A new hybridoma technology using human B cells from house dust mite-allergic patients was used to identify four Der p 2-specific hIgE mAbs. Their relative binding sites were assessed and compared by immunoassays with three previously studied murine IgG mAbs. Immunoassays showed that the recognition of Der p 2 by the first three hIgE was inhibited by a single murine IgG, but the fourth hIgE recognized a different epitope from all the other mAbs. The functional ability of the hIgE that bind different epitopes to cross-link Der p 2 was demonstrated in a mouse model of passive systemic anaphylaxis. Nuclear magnetic resonance analyses of Der p 2 in complex with IgG and IgE Abs were used to identify specific residues in the epitopes. To our knowledge, the combination of immunoassays to distinguish overlapping epitopes and nuclear magnetic resonance analyses to identify specific residues involved in Ab binding provided the first epitope mapping of hIgE mAbs to an allergen. The technologies developed in this study will be useful in high-resolution mapping of human epitopes on other Ags and the design of improved therapeutics.

Molecular approaches to allergen-specific immunotherapy: Are we so far from clinical implementation?

Conventional allergen-specific immunotherapy (AIT), based on administrations of allergen extracts, represents up to now the unique protocol for the desensitization of allergic patients. Whereas the effectiveness of AIT was evidenced for the treatment of allergic rhinitis and allergic asthma, such strategy remains experimental for food allergies up to now. However, important issues are commonly associated with AIT as the quality of natural allergen extracts, the long duration and adverse side-effects which negatively affect successful desensitization together with the patient compliance. The rapid progression of molecular allergology made possible the quest of safer, shorter and more effective immunotherapeutic approaches. The aim of this review was to provide an update on these different innovative recombinant derivatives including their efficacy but also their limitations. Despite promising preclinical and early clinical studies, the absence of convincing data in large phase III trials precludes so far the translation of these immunotherapeutic candidates into the clinic.