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.

Standardization of allergen products: 2. Detailed characterization of GMP-produced recombinant Phl p 5.0109 as European Pharmacopoeia reference standard.

BACKGROUND: The Biological Standardization Programme of the European Directorate for Quality of Medicines and Healthcare (EDQM) aims at the establishment of well-characterized reference standards based on recombinant allergens and validated assays for the quantification of major allergen content. The objective of this study was to examine the detailed physicochemical and immunological characterization of recombinant Phl p 5.0109, the second available allergen reference standard. METHODS: Recombinant Phl p 5.0109 PP5ar06007 was produced under GMP conditions and analyzed by an array of physicochemical and immunological methods for identity, quantity, homogeneity, and folding stability in bulk solution, as well as thermal denaturation, aggregation state, and biological activity when formulated for long-time storage. RESULTS: PP5ar06007 revealed as a highly homogeneous, monomeric, well-folded preparation of rPhl p 5.0109, as documented by mass spectrometry, SDS-PAGE, isoelectric focusing, size-exclusion chromatography with light scattering, circular dichroism, and infrared spectroscopy. Upon storage at +4°C, PP5ar06007 retained the monomeric state for at least 2 months. A protein quantity of 1.56 ± 0.03 mg/ml was determined by amino acid analysis in PP5ar06007, and its biological activity was shown to be comparable to natural Phl p 5 in terms of basophil activation and T-cell reactivity. CONCLUSIONS: Recombinant Phl p 5.0109 PP5ar06007 was characterized extensively at the physicochemical and immunological level. It revealed to be a highly stable, monomeric, and immunologically equivalent of its natural counterpart. PP5ar06007 is now available as European Pharmacopoeia allergen reference standard for grass pollen products.

An Aß concatemer with altered aggregation propensities.

We present an analysis of the conformational and aggregative properties of an Aß concatemer (Con-Alz) of interest for vaccine development against Alzheimer's disease. Con-Alz consists of 3 copies of the 43 residues of the Aß peptide separated by the P2 and P30 T-cell epitopes from the tetanus toxin. Even in the presence of high concentrations of denaturants or fluorinated alcohols, Con-Alz has a very high propensity to form aggregates which slowly coalesce over time with changes in secondary, tertiary and quaternary structure. Only micellar concentrations of SDS were able to inhibit aggregation. The increase in the ability to bind the fibril-binding dye ThT increases without lag time, which is characteristic of relatively amorphous aggregates. Confirming this, electron microscopy reveals that Con-Alz adopts a morphology resembling truncated protofibrils after prolonged incubation, but it is unable to assemble into classical amyloid fibrils. Despite its high propensity to aggregate, Con-Alz does not show any significant ability to permeabilize vesicles, which for fibrillating proteins is taken to be a key factor in aggregate cytotoxicity and is attributed to oligomers formed at an early stage in the fibrillation process. Physically linking multiple copies of the Aß-peptide may thus sterically restrict Con-Alz against forming cytotoxic oligomers, forcing it instead to adopt a less well-organized assembly of intermeshed polypeptide chains.

Active vaccination against IL-5 bypasses immunological tolerance and ameliorates experimental asthma.

Current therapeutic approaches to asthma have had limited impact on the clinical management and resolution of this disorder. By using a novel vaccine strategy targeting the inflammatory cytokine IL-5, we have ameliorated hallmark features of asthma in mouse models. Delivery of a DNA vaccine encoding murine IL-5 modified to contain a promiscuous foreign Th epitope bypasses B cell tolerance to IL-5 and induces neutralizing polyclonal anti-IL-5 Abs. Active vaccination against IL-5 reduces airways inflammation and prevents the development of eosinophilia, both hallmark features of asthma in animal models and humans. The reduced numbers of inflammatory T cells and eosinophils in the lung also result in a marked reduction of Th2 cytokine levels. Th-modified IL-5 DNA vaccination reduces the expression of IL-5 and IL-4 by approximately 50% in the airways of allergen-challenged mice. Most importantly, Th-modified IL-5 DNA vaccination restores normal bronchial hyperresponsiveness to beta-methacholine. Active vaccination against IL-5 reduces key pathological events associated with asthma, such as Th2 cytokine production, airways inflammation, and hyperresponsiveness, and thus represents a novel therapeutic approach for the treatment of asthma and other allergic conditions.

The significance of isoallergenic variations in present and future specific immunotherapy.

The isoallergenic variation of the tree pollen major allergens has been studied by 2D gel electrophoresis, and by analysis of several recombinant clones. The studies have included both antibody-based and T cell stimulation assays. Bet v 1, the major allergen of birch, forms at least 24 spots when conventional extracts are analyzed by 2D gel electrophoresis. Comparison of Bet v 1-encoding DNA sequences reveals a considerable number of amino acid substitutions. This sequence variation can theoretically account for the number of spots observed in 2D gels. Whereas pools of serum from allergic individuals and monospecific antibodies raised in rabbits bind to most if not all spots in 2D gels, analyses of individual serum and/or murine monoclonal antibodies show individual patterns of reactivity with various subsets of spots. These observations point to a model in which amino acid substitutions induce local perturbations of the allergen surface, causing differences in epitope structure. Furthermore, analysis of pollen from individual trees shows that each tree produces individual subsets of Bet v 1 spots. When analyzed in stimulation assays, T cell clones also display differences in reactivity to different isoallergens. In conclusion, we have shown that Bet v 1 is heterogeneous, and that individual trees produce various subsets of isoallergens which display differences in reactivity both towards antibodies and T cells. A careful selection of isoform may therefore be of major importance if recombinant allergens or synthetic peptides are to be used for conventional immunotherapy.

Group V allergens in grass pollens: IV. Similarities in amino acid compositions and NH2-terminal sequences of the group V allergens from Lolium perenne, Poa pratensis and Dactylis glomerata.

Monoclonal antibodies (PpV4) raised against Phleum pratense group V allergen were used for immuno-affinity chromatography of cross-reacting group V allergens from related grass species. Fractions enriched in group V allergen were obtained from Lolium perenne, Poa pratense and Dactylis glomerata extracts. The major components in these fractions were found in the Mwr range 25-28 kD. IgE binding to these components was shown using a pool of grass allergic sera, by SDS-PAGE immunoblotting. These fractions were electroblotted from tricine SDS-PAGE gels onto a polyvinylidene-difluoride membrane and selected group V bands were directly cut out and used for amino acid analysis and NH2-terminal sequencing. Both the amino acid compositions and the NH2-terminal sequences obtained for each group V allergen were almost similar to each other and to the sequence and composition of the previously described allergen Phl p V from Phleum pratense. A common trait of the investigated allergens, is the very high contents of alanine (25-32%) and the presence of the modified amino acid, hydroxyproline.