Diversity of human T cell receptor sequences of T cell clones with specificity for Bet v 1 peptide/MHC II complexes

T cell clones (TCC) were raised from the peripheral blood of patients suffering from tree pollen allergy. All TCC were restricted by HLA-DR molecules. In order to investigate possible intervention targets in Type I allergic diseases, we have examined T cell receptor (TCR) alpha- and beta-chain nucleotide sequences of several allergen-reactive human CD4+ TCC specific for four frequently found epitopes of Bet v 1, the major birch pollen allergen. In general, TCC specific for the 4 epitopes investigated, used diverse TCRAV and TCRBV gene segments. Moreover, the junctional regions encoding the third complementarity determining regions (CDR3) of the TCR showed striking heterogeneities in length and amino acid composition. A more restricted use of two J gene segments (TCRBJ1S4 and 2S7) was only observed in the beta-chain of TCR used by TCC specific for epitope 1. In addition, all TCC specific for epitope 4 showed an arginine residue in the N-terminal region of their TCRBV CDR3 loops despite their sequence diversities. In view of the striking heterogeneities found, therapeutical strategies aimed at the clonal deletion of allergen-specific T cell clones, providing help for IgE synthesis, may not be feasible. Moreover, our results cast a doubt on the theory, that the CDR3 exclusively provides the primary contact with the peptide bound in the major histocompatibility (MHC) groove, and suggest additional interaction with MHC class II.

Food allergy to honey: pollen or bee products? Characterization of allergenic proteins in honey by means of immunoblotting

OBJECTIVE

To characterize the allergenic components of honey, 23 patients allergic to honey were investigated. All displayed allergic symptoms after ingestion of honey or honey-containing products, ranging from itching in the oral mucosa to severe systemic symptoms to anaphylactic shock.

METHODS AND RESULTS

Immunoblot analyses of the patients' sera revealed IgE binding to proteins at a molecular mass of 54 kd, 60 kd, 72 kd, or to a 30 kd/33 kd double band, or to both in sunflower honey extracts. The three bands corresponding to higher molecular mass proteins could also be detected in the three other kinds of honey (locust tree, European chestnut and forest honey) that were tested and represented bee products because IgE binding to these proteins was inhibited by extracts of honeybee heads and extracts of isolated bee venom sacs. The 30 kd/33 kd bands could be identified as sunflower honey-specific. When testing sera from patients allergic to bee venom with honey extracts, in seven of 10 cases IgE binding to bee-specific components could be observed.

CONCLUSION

Both proteins derived from secretions of pharyngeal and salivary glands of honeybee heads and pollen proteins contained in the honey cause allergic reactions to honey.

Detection of allergen-specific IgE in tears of grass pollen-allergic patients with allergic rhinoconjunctivitis

BACKGROUND

Allergic conjunctivitis is a common symptom amongst Type I (IgE-mediated) allergic diseases; and most frequently seen as rhinoconjunctivitis. However, the site of production and the significance of allergen specific IgE needs further elucidation.

OBJECTIVE

We investigated whether the presence of IgE in tears of grass pollen allergic patients correlated with disease and clinical symptoms, whether the IgE binding pattern to the different grass pollen antigens was different in sera and tears, and whether IgA antibodies to grass pollen allergens were present in tears. Finally, we looked whether specific IgE was produced locally or was exudated from serum.

METHODS

Sera from 44 grass pollen allergic patients suffering from either allergic rhinitis (n = 11) or allergic rhinoconjunctivitis (n = 33) and from healthy controls (n = 7) were used for the experiments. Binding of specific IgE and IgA antibodies to the different groups of grass pollen allergens (Phleum pratense) was evaluated by means of immunoblotting.

RESULTS

Specific IgE was detected in sera as well as in tears of allergic patients, whereby tear-derived allergen-specific IgE exerted similar specificities to the corresponding IgE from serum. The correlation between symptoms of ocular allergy and the presence of allergen-specific IgE in tears was highly significant (P < 0.0001). In contrast, only a poor correlation was found between specific and/or total IgE in sera and the manifestation of ocular allergy (P = 0.73).

CONCLUSION

Allergen-specific IgE antibodies in tears seem to be produced locally rather than exudated from serum. IgE in tears seems to be responsible for allergic conjunctivitis. IgA in tears cannot exert a protective function since the IgA antibodies recognize different antigens in a grass pollen (Phleum pratense) extract than IgE antibodies. The highly significant correlation between allergic conjunctivitis and the presence of specific tear IgE emphasizes the diagnostic value of immunoblots with tear IgE, especially in cases in which serum provides inconclusive results.

Serological and skin-test diagnosis of birch pollen allergy with recombinant Bet v I, the major birch pollen allergen

BACKGROUND

Type I allergy represents a severe health problem in industrialized countries where up to 20% of the population suffer from allergic rhinitis, conjunctivitis and allergic asthma bronchiale and in severe cases from anaphylaxis, leading to death.

OBJECTIVE

The aim of this study was to evaluate recombinant Bet v I, the major birch pollen allergen for in vivo and in vitro diagnosis of birch pollen allergy.

METHODS

A group of 51 birch pollen allergic patients and eight non-allergic control individuals were tested for birch pollen allergy by skin-prick and intradermal testing, comparing commercial birch pollen extracts with recombinant Bet v I. Quantitative and qualitative serological testing was done with natural and recombinant allergens by radioallergosorbent test (RAST), enzyme-linked immunosorbent assay (ELISA) and immunoblotting.

RESULTS

Recombinant Bet v I allowed accurate in vivo and in vitro diagnosis of tree pollen allergy in 49/51 patients tested. No false positive results were obtained in any in vitro assay system (ELISA, Western blot) or by skin testing (skin-prick, intradermal test) with recombinant Bet v I.

CONCLUSION

Our results document that recombinant Bet v I produced in bacterial expression systems allows accurate in vitro and in vivo diagnosis of birch pollen allergy in > 95% of birch pollen allergic patients.

IgE cross-reactivities against albumins in patients allergic to animals

BACKGROUND

Type I allergic symptoms and severe asthma in particular are frequently caused by animal hair/dander proteins, among which albumins are possible cross-sensitizing allergenic components.

METHODS

The significance and degree of IgE-cross-reactivities against various albumins were studied in a representative number (n = 200) of patients allergic to animals with hair/dander extracts, purified albumins from different animals, and a recombinant dog albumin fragment expressed in lysogenic Escherichia coli Y1089 and purified as a beta-galactosidase fusion protein.

RESULTS

Despite a high degree of sequence homology among different albumins, a remarkable variability of IgE cross-reactivities was observed, indicating that some patients were sensitized preferentially against certain albumins. Most of the patients allergic to albumins, however, reacted to dog, cat, and horse albumin, which also bound a high percentage of albumin-specific IgE.

CONCLUSION

The purified recombinant dog albumin fragment, representing 265 amino acids of the mature protein, bound IgE from all 15 patients allergic to albumin tested suggesting its potential usefulness for diagnosis and perhaps therapy.

Recombinant allergens for diagnosis and therapy of allergic diseases

A considerable number of cDNAs coding for allergens have been isolated and expressed. Structural and immunological similarities between recombinant allergens and natural allergens indicate that a sufficient panel of recombinant allergens can be produced for diagnosis and therapy of allergic diseases. Recent studies document the successful in vitro and in vivo determination of a patient's allergen profile (allergogram) with recombinant allergens and encourage the use of recombinant allergens for specific therapy.

T-cell epitopes of Phl p 1, major pollen allergen of timothy grass (Phleum pratense): evidence for crossreacting and non-crossreacting T-cell epitopes within grass group I allergens

BACKGROUND

The use of peptides representing T-cell epitopes of allergens is a modern concept for improvement of specific immunotherapy. A prerequisite for this approach is the identification of T-cell epitopes of atopic allergens.

METHODS

T-cell lines and 40 T-cell clones (TCC) specific for Phl p 1, the group I allergen of timothy grass (Phleum pratense), were established from the peripheral blood of nine patients allergic to grass pollen and mapped for epitope specificity by using overlapping dodecapeptides. Phenotype and cytokine production profile of TCC were investigated. Representative TCC were analyzed for HLA-restriction, T-cell receptor V beta gene usage, and crossreactivity with grass pollen extracts from Dactylis glomerata, Poa pratensis, Lolium perenne, Secale cereale, and selected amino acid sequence-derived peptides.

RESULTS

Patients displayed IgE binding to all grass species investigated. Forty TCC were established. Fifteen T-cell epitopes could be identified on Phl p 1. Of 40 TCC, 39 displayed the helper cell (Th) phenotype; one clone was CD8+. Specific stimulation induced a Th2-like type of cytokine production in 20 of 39 TCC. Crossreactivity studies revealed crossreacting and non-crossreacting T-cell epitopes.

CONCLUSION

Phl p 1, a major grass pollen allergen, harbors multiple T-cell epitopes. Species-specific and crossreacting T-cell epitopes exist among group I allergens of grasses. Epitope recognition patterns could not be correlated with particular HLA haplotypes. A restricted T-cell receptor V beta gene usage was not observed.

Molecular characterization of Api g 1, the major allergen of celery (Apium graveolens), and its immunological and structural relationships to a group of 17-kDa tree pollen allergens

Individuals suffering from immediate hypersensitivity (type-I allergy) to a particular pollen frequently display intolerance to several foods of plant origin. In this respect, individuals sensitized to birch pollen and/or mugwort pollen frequently display type-I allergic symptoms after ingestion of celery. In this study, we expressed the major allergenic protein of celery, Api g 1, which is responsible for the birch-celery syndrome, in the form of a non-fusion protein. The open reading frame of the cDNA of Api g 1 codes for a protein of 153 amino acids with a molecular mass of 16.2 kDa and 40% identity (60% similarity) to the major allergen of birch pollen, Bet v 1. Furthermore, Api g 1 exhibited similar characteristics to (a) two proteins in parsley induced by fungal infection, (b) the major tree pollen allergens and (c) pathogenesis-related and stress-induced proteins in other plant species. The reactivity of recombinant Api g 1 with IgE antibodies present in sera from celery intolerant patients was comparable to that of the natural celery allergen. Cross-reactivity with Bet v 1 was proven by cross-inhibition experiments, which provides further support for the existence of the birch-celery syndrome and for the suggestion that allergies to some vegetable foods are epiphenomena to allergies caused by inhalation of tree pollen.

High level expression of birch pollen profilin (Bet v 2) in Escherichia coli: purification and characterization of the recombinant allergen

Up to 20% of the population in industrialized countries suffer from type I allergic symptoms (rhinitis, conjunctivitis, and bronchial asthma). The cDNA coding for birch pollen profilin, a highly conserved cross-reactive allergen and actin-binding protein was expressed in Escherichia coli. Upon induction with IPTG up to 30 mg recombinant profilin per liter culture could be obtained. A single step purification protocol based on the high affinity of profilin to poly-(L-proline) Sepharose was used to obtain large amounts of soluble and pure recombinant birch profilin. Recombinant birch pollen profilin specifically bound IgE, elicited dose dependent histamine release from patients basophils and could be used for skin prick testing without toxic effects. The results indicate that by using purified recombinant profilin, specific diagnosis of type I allergy might be improved.

Cloning and sequencing of Mal d 1, the major allergen from apple (Malus domestica), and its immunological relationship to Bet v 1, the major birch pollen allergen

The number of tree-pollen-allergic patients showing allergic reactions to apples, various vegetables and nuts is increasing. In this paper the molecular characterization of the major apple allergen, Mal d 1, is reported. The cDNA coding for Mal d 1 was cloned and sequenced. Its open reading frame codes for a protein of 159 amino acids with a predicted molecular mass of 17.7 kDa and a predicted pI of 5.9. Sequence comparison to Bet v 1, the major birch pollen allergen, revealed 64.5% identity on the amino acid level and 55.6% identity on the nucleic acid level. Recombinant Mal d 1 was expressed in the plasmid pMW 175 in E. coli BL 21 (DE3) and its immunological properties were tested. Crossreactivity with Bet v 1 was shown by inhibition assays.

Effects of IL-4 and IL-13 on total and allergen specific IgE production by cultured PBMC from allergic patients determined with recombinant pollen allergens

BACKGROUND

Interleukin (IL)-4 and IL-13 have been shown to be potent switch factors for IgE synthesis in human B cells.

OBJECTIVE

In this study we investigated the effects of recombinant human IL-4 and IL-13 on total and allergen specific IgE synthesis by peripheral blood mononuclear cells (PBMC) from pollen allergic patients and healthy control individuals.

METHODS

Peripheral blood mononuclear cells (PBMC) from allergic patients were investigated for their capacity to produce allergen specific IgE in vitro. Total protein extracts from birch pollen and timothy grass pollen as well as purified recombinant birch pollen allergens, Bet v I, birch profilin (Bet v II) and recombinant timothy grass pollen allergens, Phl p I, Phl p II, and Phl p V were used to measure specific IgE-antibody synthesis in cell culture supernatants by IgE-immunoblot and ELISA.

RESULTS

PBMC obtained from allergic patients spontaneously secreted allergen specific IgE in the culture supernatants. Addition of Interleukin 4, Interleukin 13 and anti-CD40 antibody to the cultures alone or in combinations significantly induced total IgE production whereas allergen specific IgE production was not affected.

CONCLUSION

Our results indicate that the peripheral blood of allergic individuals contains long lived allergen specific B cells which have already switched to IgE production and which are not sensitive to IL-4 and IL-13 treatment. These results may have implications on attempts to use cytokines or cytokine antagonists in therapy of Type I allergy.

Hydrocortisone enhances total IgE levels--but not the synthesis of allergen-specific IgE--in a monocyte-dependent manner

Recently, hydrocortisone (HC), when combined with human IL-4, has been reported to increase IgE levels in supernatants (SN) of in vitro cultured leucocytes. In this study we investigated the influence of HC on allergen-specific IgE synthesis. Moreover, we examined the relevance of different cell types in this respect. Peripheral blood mononuclear cells (PBMC), T-cell depleted PBMC, CD14-depleted PBMC and highly purified B cells from 10 allergic (birch pollen and/or grass pollen) patients and five non-allergic individuals were investigated. The cells were incubated with HC and/or recombinant human IL-4 (rIL-4) for 8 days. A considerable increase of total IgE was observed in HC/rIL-4-stimulated cultures compared with rIL-4 alone, HC alone or non-stimulated cultures. We demonstrate that this effect depends on the presence of monocytes in in vitro cultures. These results were seen in every experiment, irrespective of healthy or atopic state of the blood donor. The increase of IgE could not be attributed to a rise of birch pollen-and/or grass pollen-specific IgE in patients allergic to these allergens, as shown by IgE-immunoblot. Radio-allergosorbent test (RAST) investigations of HC/rIL-4-stimulated cells cultures from allergic and non-allergic patients confirmed that HC/rIL-4-induced elevated IgE production was also not due to increased production of IgE, specific for important aero-allergens (pollens, house dust mite or animal dander). Therefore we conclude that newly synthesized IgE is not specific for allergens, but that sequential isotype switching in human B cells leads to increased polyclonal IgE production.

Allergen-specific IgE production of committed B cells from allergic patients in vitro

The allergen-specific in vitro IgE synthesis in blood leukocytes from patients with allergy was monitored outside the pollen season with recombinant and natural pollen allergens and was compared with the total IgE production. The addition of interleukin-4 (IL-4) and antibody to CD40 increased the amount of total IgE by up to 20-fold in the culture supernatants of peripheral blood leukocytes from patients with allergy that could be antagonized by a neutralizing anti-IL-4 antibody in a dose-dependent manner. In contrast to total IgE, the amount of allergen-specific IgE was not affected by IL-4, and anti-CD40 or anti-IL-4, treatment. With oligonucleotides specific for IgE, complementary DNA from the amino terminal of the IgE heavy chain could be reversely transcribed and amplified by polymerase chain reaction from RNA of patients' unstimulated blood leukocytes, indicating that the IgE secretion in the cultures is due to a de novo IgE synthesis. It is concluded that the peripheral blood of patients with allergy contains long-lived allergen-specific B cells, which are not responsive to IL-4-mediated signals. These results may have implications for attempts to modulate specific IgE production in allergic patients with cytokines or cytokine antagonists.

The high affinity IgE receptor (Fc epsilon RI) mediates IgE-dependent allergen presentation

The discovery that the high affinity IgE receptor (Fc epsilon RI) is expressed on APCs of patients with atopic diseases raised the possibility that the functional importance of Fc epsilon RI in the pathogenesis of atopy may extend beyond its role in type I allergic reactions. Here we show that, following removal of in vivo-bound IgE by lactic acid treatment, targeting of allergens to monocytes by Ag-specific IgE critically depends on Fc epsilon RI expression. Even more importantly, lactic acid-treated, monocyte-enriched PBMCs present allergen to T cells 100- to 1000-fold more effectively if the allergen has been targeted to Fc epsilon RI on these cells via allergen-specific IgE. This mechanism may critically lower the atopic individual's threshold to mount allergen-specific T cell responses capable of promoting IgE production and delayed-type hypersensitivity reactions.

The high affinity IgE receptor (Fc epsilon RI) mediates IgE-dependent allergen presentation

The discovery that the high affinity IgE receptor (Fc epsilon RI) is expressed on APCs of patients with atopic diseases raised the possibility that the functional importance of Fc epsilon RI in the pathogenesis of atopy may extend beyond its role in type I allergic reactions. Here we show that, following removal of in vivo-bound IgE by lactic acid treatment, targeting of allergens to monocytes by Ag-specific IgE critically depends on Fc epsilon RI expression. Even more importantly, lactic acid-treated, monocyte-enriched PBMCs present allergen to T cells 100- to 1000-fold more effectively if the allergen has been targeted to Fc epsilon RI on these cells via allergen-specific IgE. This mechanism may critically lower the atopic individual's threshold to mount allergen-specific T cell responses capable of promoting IgE production and delayed-type hypersensitivity reactions.

Identification of allergens in fruits and vegetables: IgE cross-reactivities with the important birch pollen allergens Bet v 1 and Bet v 2 (birch profilin)

BACKGROUND

In this study serum samples collected from 20 patients with birch pollen allergy were investigated. All patients had experienced allergic symptoms after contact with or ingestion of particular fresh fruits and vegetables known as birch pollen-related foods.

METHODS

Serum samples were tested by means of immunoblotting for IgE reactivities with proteins in extracts of birch pollen, apple, pear, celery, carrot, and potato. Anti-Bet v 1 and anti-Bet v 2 antibodies were used to investigate cross-reactivity. Inhibition studies were performed by preincubation of sera with recombinant Bet v 1 and Bet v 2.

RESULTS

IgE binding to proteins, corresponding to the major birch pollen allergen Bet v 1 and to Bet v 2 (birch pollen profilin) could be observed. An allergen homologous to Bet v 1 could be detected in apple, pear, and celery when a Bet v 1-specific monoclonal antibody was used. Testing a polyclonal rabbit anti-Bet v 2 antibody with extracts of the respective plants revealed the presence of profilins in every source tested. Inhibition with recombinant Bet v 1 and Bet v 2 led to complete blocking or marked reduction of IgE binding to proteins of comparable molecular weights in the respective food extracts, indicating IgE cross-reactivity.

CONCLUSION

Our results indicate that many plant-derived food agents contain proteins with high homology to the birch pollen allergens Bet v 1 and Bet v 2 and must therefore be considered as potentially threatening for patients with tree pollen allergy.

Diversity of TCRAV and TCRBV sequences used by human T-cell clones specific for a minimal epitope of Bet v 1, the major birch pollen allergen

T-cell clones (TCC) were raised from the peripheral blood of patients suffering from tree pollen allergy. All TCC were restricted by HLA-DR molecules. In order to investigate possible intervention targets in Type I allergic diseases, we examined T-cell receptor (TCR) alpha and beta chain nucleotide sequences of five allergen-reactive human CD4+ TCC specific for a C-terminal epitope (BV 144) of Bet v 1, the major birch pollen allergen. Proliferation assays using synthetic peptides revealed the 10-mer LRAVESYLLA as minimal epitope for three TCC; two TCC also displayed reactivity with the nonapeptide LRAVESYLL. Two TCC expressed TCRBV2S3, all other BV144-specific TCC used diverse TCRAV and TCRBV gene segments. Moreover, the junctional regions encoding the third complementary determining regions (CDR3) of the TCR showed a striking heterogeneity in length and amino acid composition. Nevertheless, all TCC showed an arginine residue in the N-terminal region of their TCRBV CDR3 loops. Therefore, therapeutical strategies aimed at the clonal deletion of allergen-specific T-cell clones, providing help for IgE synthesis, will not be feasible. Our results cast a doubt on the theory that the CDR3 exclusively provides the primary contact with the peptide bound in the major histocompatibility (MHC) groove, and suggest additional interaction with MHC class II.