Diverse and highly cross-reactive T-cell responses in ragweed allergic patients independent of geographical region.

BACKGROUND: Ragweed frequently causes seasonal allergies in North America and Europe. In the United States, several related ragweed species with diverse geographical distribution cause allergic symptoms. Cross-reactivity towards related ragweed species of IgE and treatment-induced IgG4 has been demonstrated previously. However, less is known about the underlying T-cell cross-reactivity. METHODS: The allergen content of ragweed extracts was determined by mass spectrometry and related to T-cell epitopes of Amb a allergens (group 1, 3, 4, 5, 8 and 11) in 20 American ragweed allergic patients determined by FluoroSpot and proliferation assays. T-cell responses to 50 frequently recognized Amb a-derived T-cell epitopes and homologous peptides from western ragweed (Amb p), giant ragweed (Amb t) and mugwort (Art v) were investigated in an additional 11 American and 14 Slovakian ragweed allergic donors. RESULTS: Ragweed extracts contained all known allergens and isoallergens thereof. Donor T-cell responses were diverse and directed against all Amb a 1 isoallergens and to most minor allergens investigated. Similar response patterns were seen in American and Slovakia donors. Several epitopes were cross-reactive between isoallergens and ragweed species, some even including mugwort. T-cell cross-reactivity generally correlated with allergen sequence homology. CONCLUSION: T-cell epitopes of multiple allergens/isoallergens are involved in the diverse T-cell responses in ragweed allergic individuals. T-cell lines were highly cross-reactive to epitopes of related ragweed species without any apparent geographical response bias. These data support that different ragweed species can be considered an allergen homology group with Amb a as the representative species regarding diagnosis as well as allergy immunotherapy.

Chemical modification of birch allergen extract leads to a reduction in allergenicity as well as immunogenicity.

BACKGROUND: In Europe, specific immunotherapy is currently conducted with vaccines containing allergen preparations based on intact extracts. In addition to this, chemically modified allergen extracts (allergoids) are used for specific allergy treatment. Reduced allergenicity and thereby reduced risk of side effects in combination with retained ability to activate T cells and induce protective allergen-specific antibody responses has been claimed for allergoids. In the current study, we compared intact allergen extracts and allergoids with respect to allergenicity and immunogenicity. METHODS: The immunological response to birch allergen extract, alum-adsorbed extract, birch allergoid and alum-adsorbed allergoid was investigated in vitro in human basophil histamine release assay and by stimulation of human allergen-specific T cell lines. In vivo, Bet v 1-specific IgG titers in mice were determined after repetitive immunizations. RESULTS: In all patients tested (n = 8), allergoid stimulations led to reduced histamine release compared to the intact allergen extract. However, the allergoid preparations were not recognized by Bet v 1-specific T cell lines (n = 7), which responded strongly to the intact allergen extract. Mouse immunizations showed a clearly reduced IgG induction by allergoids and a strongly potentiating effect of the alum adjuvant. Optimal IgG titers were obtained after 3 immunizations with intact allergen extracts, while 5 immunizations were needed to obtain maximal response to the allergoid. CONCLUSION: The reduced histamine release observed for allergoid preparations may be at the expense of immunological efficacy because the chemical modifications lead to a clear reduction in T cell activation and the ability to induce allergen-specific IgG antibody responses.

Kinetics and mode of peptide delivery via the respiratory mucosa determine the outcome of activation versus TH2 immunity in allergic inflammation of the airways.

BACKGROUND: Specific immunotherapy involving systemic injection of allergen, though highly effective, can cause severe side effects due to IgE-mediated activation of effector cells. Allergen-derived peptides might provide a safer alternative. We have investigated the use of mucosally delivered peptide to induce CD4(+) T(H)2 cell tolerance and thus protect against allergen-induced airway inflammation. OBJECTIVE: The purpose of this study was to investigate whether intranasal administration of an allergen-derived peptide, either alone or adsorbed to chitosan, can prevent the induction of T(H)2-mediated pulmonary inflammation after sensitization and challenge of the airways with allergen. METHODS: Mice were given (intranasally) a peptide containing an immunodominant epitope of the Dermatophagoides pteronyssinus (Der p) 1 allergen, either as soluble antigen or adsorbed to chitosan, before sensitization and allergen challenge. Pulmonary inflammation, antigen-specific CD4(+) T-cell responses, and antibody levels in sera were then determined. RESULTS: Mice given peptide adsorbed to chitosan had significant reductions in airway eosinophilia, which correlated with reduced levels of IL-4 and IL-5 in the bronchoalveolar lavage fluid. There was decreased recruitment of activated CD4(+) T cells into the airways after allergen challenge, which correlated with a loss of Der p 1-specific T-cell cytokine responses in the periphery and the localized production of IL-10 by antigen-specific T cells in bronchial lymph nodes. Induction of peripheral T-cell tolerance was preceded by transient T-cell activation and IFN-gamma production. CONCLUSION: Our data demonstrate that suppression of airway inflammation by intranasal administration of peptide antigen adsorbed to chitosan is initiated by transient T-cell activation and maintained by the production of IL-10 by antigen-specific T cells in the draining lymph nodes.

Allergy vaccine engineering: epitope modulation of recombinant Bet v 1 reduces IgE binding but retains protein folding pattern for induction of protective blocking-antibody responses.

Human type 1 immediate allergic response symptoms are caused by mediator release from basophils and mast cells. This event is triggered by allergens aggregating preformed IgE Abs bound to the high-affinity receptor (FcepsilonRI) on these cells. Thus, the allergen/IgE interaction is crucial for the cascade leading to the allergic and anaphylactic response. Two genetically engineered forms of the white birch pollen major allergen Bet v 1 with point mutations directed at molecular surfaces have been characterized. Four and nine point mutations led to a significant reduction of the binding to human serum IgE, suggesting a mutation-induced distortion of IgE-binding B cell epitopes. In addition, the mutated allergens showed a decrease in anaphylactic potential, because histamine release from human basophils was significantly reduced. Retained alpha-carbon backbone folding pattern of the mutated allergens was indicated by x-ray diffraction analysis and circular dichroism spectroscopy. The rBet v 1 mutants were able to induce proliferation of T cell lines derived from birch pollen allergic patients. The stimulation indices were similar to the indices of nonmutated rBet v 1 and natural Bet v 1 purified from birch pollen. The ability of anti-rBet v 1 mutant specific mouse IgG serum to block binding of human serum IgE to rBet v 1 demonstrates that the engineered rBet v 1 mutants are able to induce Abs reactive with nonmodified Bet v 1. rBet v 1 mutants may constitute vaccine candidates with improved efficacy/safety profiles for safer allergy vaccination.