Prevention of allergy by a recombinant multi-allergen vaccine with reduced IgE binding and preserved T cell epitopes

Abstract

Novel approaches for the prevention of allergy are required, because of the inevitably increasing prevalence of allergic diseases during the last 30 years. Here, a recombinant chimeric protein, which comprises the whole amino acid sequences of three bee venom major allergens has been engineered and used in prevention of bee venom sensitization in mice. Phospholipase A 2 (Api m 1), hyaluronidase (Api m 2) and melittin (Api m 3) fragments with overlapping amino acids were assembled in a different order in the Api m (1/2/3) chimeric protein, which preserved entire T cell epitopes, whereas B cell epitopes of all three allergens were abrogated. Accordingly, IgE cross-linking leading to mast cell and basophil mediator release was profoundly reduced in humans. Supporting these findings, the Api m (1/2/3) induced 100 to 1000 times less type-1 skin test reactivity in allergic patients. Treatment of mice with Api m (1/2/3) led to a significant reduction of specific IgE development towards native allergen, representing a protective vaccine effect in vivo. These results demonstrate a novel prototype of a preventive allergy vaccine, which preserves the entire T cell epitope repertoire, but bypasses induction of IgE against native allergen, and side effects related to mast cell/basophil IgE FceRI cross-linking in sensitized individuals.

Immunotherapy for allergic rhinitis

“…Attempts have been made to improve these adjuvants so as to enhance the therapeutic effects of vaccination. Most of these approaches have involved chemical conjugation of the allergen to so-called 'immune response modifiers' (Box 4), which typically target Toll-like receptors on the surface of antigen-presenting cells, thus increasing the Strategies to alter the shape of intact allergens Fusion of major allergens Several major allergens are fused and expressed as a recombinant protein, thus altering the shape of the individual allergens and reducing IgE binding while preserving T cell epiotpes [168] Chimeric allergens Fragments of major allergens are fused and expressed as a single protein, thus reducing IgE binding but preserving T cell epitopes (provided the fragments are sufficiently large) [169] Polymeric allergens Major allergens are polymerized, reducing IgE binding but preserving T cell epitopes [143] Unrefolded allergens Major recombinant allergens are denatured and then allowed to refold but in a manner different to the native conformation, reducing or abolishing IgE binding but preserving T cell epitopes [170] Strategies to fragment allergens Allergen fragments Major allergens are divided into fragments, thus abolishing IgE binding but preserving T cell epitopes [143] Allergen peptides Treatment is with a mixture of allergen-derived peptides covering the entire molecule or identified T cell epitopes, thus abolishing IgE binding [171] Conjugation of allergens to immune response modifiers Conjugation to CpG oligonucleotide Major allergen is bound to a Toll-like receptor ligand (in this case TLR9), thus skewing the induced innate and adaptive immune responses away from the Th2 phenotype [172] Conjugation to virus-like particles Allergens or allergen-derived peptides are coupled to virus capsid-like recombinant proteins, thus skewing the adaptive immune response and enhancing immunogenicity [173] Miscellaneous strategies Mixtures of recombinant allergens An attempt to rationalize allergen concentrations in vaccines by using mixtures of recombinant allergens of complete purity and known concentrations [92] Combination immunotherapy with anti-IgE therapy The rationale is to improve the safety of allergen immunotherapy by pretreatment with anti-IgE, thus reducing or abolishing the possibility of anaphylaxis; safety and efficacy are still under investigation [161,174] Intralymphatic vaccination Administration of immunotherapy vaccines directly into lymph nodes under ultrasound guidance, the aim being to deliver high concentrations of allergen directly into the secondary lymphoid system; safety and efficacy are currently being explored [159] c 2011 Blackwell Publishing Ltd, Clinical & Experimental Allergy, 41 : 1177-1200 immunogenicity of the allergen and, at least in theory, skewing the balance of the resulting T cell response away from the Th2 phenotype. As an alternative to chemically modifying the allergen, another approach is to inject it adsorbed onto a modified conventional adjuvant containing bacterial cell wall analogues such as monophosphoryl lipid A, which is again postulated to act as an immune response modifier …”

Allergen immunotherapy for allergic respiratory diseases

“…[142][143][144][145][146][147][148] Another strategy is the fragmentation of allergens to alter their structure while preserving T cell epitopes, or immunization with identified T cell epitopes. 137 This latter strategy may be problematic in that many allergenic substances (such as grass pollen) contain a mixture of many proteins to which most individuals (major allergens) or only a minority of individuals (minor allergens) may respond.…”

“…While this has been achieved successfully for some mixtures of allergens, 142 it is still problematic when extracts comprise many major and minor allergens. Although attractive in terms of allergen standardization, this strategy is likely to be expensive and not necessarily of therapeutic advantage.…”

Novel immunotherapy vaccine development

“…Allergen fragments, fusions, hybrids and chimeras [1, [3][4][5]31,32] are used to avoid recognition by conformation-dependent B-cell epitopes and utilize linear amino acid sequence of T-cell epitopes. These approaches provide the possibility to enhance the tolerogenic T-cell-dependent signal due to the administration of higher doses of preparation with the low risk of anaphylaxis [11,32].…”