Protective effect of the DNA vaccine encoding the major house dust mite allergens on allergic inflammation in the murine model of house dust mite allergy

Airborne indoor allergen serine proteases and their contribution to sensitisation and activation of innate immunity in allergic airway disease

Common airborne allergens (pollen, animal dander and those from fungi and insects) are the main triggers of type I allergic disorder in the respiratory system and are associated with allergic rhinitis, allergic asthma, as well as immunoglobulin E (IgE)-mediated allergic bronchopulmonary aspergillosis. These allergens promote IgE crosslinking, vasodilation, infiltration of inflammatory cells, mucosal barrier dysfunction, extracellular matrix deposition and smooth muscle spasm, which collectively cause remodelling of the airways. Fungus and insect (house dust mite and cockroaches) indoor allergens are particularly rich in proteases. Indeed, more than 40 different types of aeroallergen proteases, which have both IgE-neutralising and tissue-destructive activities, have been documented in the Allergen Nomenclature database. Of all the inhaled protease allergens, 85% are classed as serine protease activities and include trypsin-like, chymotrypsin-like and collagenolytic serine proteases. In this article, we review and compare the allergenicity and proteolytic effect of allergen serine proteases as listed in the Allergen Nomenclature and MEROPS databases and highlight their contribution to allergic sensitisation, disruption of the epithelial barrier and activation of innate immunity in allergic airways disease. The utility of small-molecule inhibitors of allergen serine proteases as a potential treatment strategy for allergic airways disease will also be discussed.

Optimization of a Der p 2-based prophylactic DNA vaccine against house dust mite allergy

DNA vaccines encoding allergens are promising immunotherapeutics to prevent or to treat allergy through induction of allergen-specific Th1 responses. Despite anti-allergy effects observed in small rodents, DNA-based vaccines are weak immunogens in primates and humans and particularly when administered by conventional injection. The goal of the present study was to improve the immunogenicity of a prophylactic vaccine encoding the major house dust mite allergen Der p 2. In this context, we evaluated the influence of different DNA backbones including notably intron and CpG enriched sequence, the DNA dose, the in vivo delivery by electroporation as well as the heterologous prime boost regimen on the vaccine efficiency. We found that a minimal allergen expression level threshold must be reached to induce the production of specific antibodies but beyond this limit, the intensity of the immune response was independent on the DNA dose and allergen expression. The in vivo DNA delivery by electroporation drastically enhanced the production of specific antibodies but not the IFNg secretion. Vaccination of naïve mice with DNA encoding Der p 2 delivered by electroporation even at very low dose (2μg) prevented the development of house dust mite allergy through Th1-skewed immune response characterized by the drastic reduction of allergen-specific IgE, IL-5 and lung inflammation together with the induction of strong specific IgG2a titers and IFNg secretion. CpG cassette in the DNA backbone does not play a critical role in the efficient prophylaxis. Finally, comparable protective immune responses were observed when using heterologous DNA prime/protein boost or homologous DNA prime/boost. Taken together, these data suggest that the potent Th1 response induced by DNA-based vaccine encoding allergens through electroporation provides the rationale for the evaluation of DNA encoding Der p 2 into HDM allergy clinical trials.

Adjuvants for allergy vaccines

Allergen-specific immunotherapy is currently performed via either the subcutaneous or sublingual routes as a treatment for type I (IgE dependent) allergies. Aluminum hydroxide or calcium phosphate are broadly used as adjuvants for subcutaneous allergy vaccines, whereas commercial sublingual vaccines rely upon high doses of aqueous allergen extracts in the absence of any immunopotentiator. Adjuvants to be included in the future in products for allergen specific immunotherapy should ideally enhance Th1 and CD4+ regulatory T cell responses. Imunomodulators impacting dendritic or T cell functions to induce IL10, IL12 and IFNγ production are being investigated in preclinical allergy models. Such candidate adjuvants encompass synthetic or biological immunopotentiators such as glucocorticoids, 1,25-dihydroxy vitamin D3, selected probiotic strains (e.g., Lactobacillus and Bifidobacterium species) as well as TLR2 (Pam3CSK4), TLR4 (monophosphoryl lipid A, synthetic lipid A analogs) or TLR9 (CpGs) ligands. Furthermore, the use of vector systems such as mucoadhesive particules, virus-like particles or liposomes are being considered to enhance allergen uptake by tolerogenic antigen presenting cells present in mucosal tissues.

House dust mite allergy in Korea: the most important inhalant allergen in current and future

The house-dust mite (HDM), commonly found in human dwellings, is an important source of inhalant and contact allergens. In this report, the importance of HDM allergy in Korea and the characteristics of allergens from dust mite are reviewed with an emphasis on investigations performed in Korea. In Korea, Dermatophagoides farinae is the dominant species of HDM, followed by D. pteronyssinus. Tyrophagus putrescentiae is also found in Korea, but its role in respiratory allergic disease in Korea is controversial. The relatively low densities of mite populations and concentrations of mite major allergens in dust samples from Korean homes, compared to westernized countries, are thought to reflect not only different climatic conditions, but also cultural differences, such as the use of 'ondol' under-floor heating systems in Korean houses. HDM are found in more than 90% of Korean houses, and the level of exposure to HDM is clinically significant. About 40%-60% of Korean patients suffering from respiratory allergies, and more than 40% of patients suffering from atopic dermatitis, are sensitized to HDM. Mite allergens can be summarized according to their inherent auto-adjuvant activities and/or their binding affinities to the adjuvant-like substances: proteolytic enzymes, lipid binding proteins, chitin binding proteins, and allergens not associated with adjuvant-like activity. In general, allergens with a strong adjuvant-like activity or adjuvant-binding activity elicit potent IgE reactivity. In Korea, Der f 2 is the most potent allergen, followed by Der f 1. Immune responses are modulated by the properties of the allergen itself and by the adjuvant-like substances that are concomitantly administered with the antigens. Characterization of allergenic molecules and elucidation of mechanisms by which adjuvant-like molecules modulate allergic reactions, not only in Korea but also worldwide, will provide valuable information on allergic diseases, and are necessary for the development of diagnostic tools and therapeutic strategies.

New types of immunotherapy in children

Injection immunotherapy has been shown to be particularly beneficial in treating allergic rhinitis, mild to moderate asthma, and anaphylaxis caused by bee and wasp venom. It also produces a long-term, antigen-specific, protective immune effect and is the only treatment that offers the possibility of reducing the risk of asthma development in children with allergic rhinitis. Nonetheless, the potentially severe side effects associated with this form of immunotherapy limit its widespread use. Diverse preparations are being developed to increase its safety and improve its efficacy. These include alternative routes of administration, particularly the sublingual route; use of novel adjuvants, such as CpG oligonucleotides and mycobacterial vaccines; and other approaches, such as peptide immunotherapy, recombinant allergens, DNA vaccination, and combined therapy. Some of these immunotherapy forms have been evaluated in children.

Novel vaccines and adjuvants for allergen-specific immunotherapy

Advances in genetic engineering and biotechnology, in parallel to increased understanding of disease processes and mechanisms of protective immunity, have facilitated the development of novel rational vaccination concepts for allergy. The spectrum ranges from utilizing recombinant proteins, peptides, new adjuvants, immunomodulatory therapy and DNA vaccines, to use of new application routes for both prophylaxis and treatment of allergic disease. New therapeutic concepts based on patient-tailored immunotherapy using recombinant allergens, anti-IgE and sublingual immunotherapies are slowly moving from the bench to the clinics. The additive value of new treatments above existing therapies must be, however, focused on the improvement of efficacy for long-term cure and increased patient compliance to warrant a broad applicability that has to compete with the symptomatic control of allergic and asthmatic diseases of currently available drugs.