IgE cross-reactivity between birch pollen, mugwort pollen and celery is due to at least three distinct cross-reacting allergens: immunoblot investigation of the birch-mugwort-celery syndrome

BACKGROUND

Allergy to celery is often associated with sensitization to birch and/or mugwort pollen.

OBJECTIVE AND METHODS

In a multi-centre study, sera from 23 patients suffering from type 1 allergy to celery and 15 patients with positive celery RAST but no clinical sensitization were compared. To examine whether cross-reactivity between celery and mugwort pollen includes cross-sensitization to birch pollen allergens, we determined cross-reacting structures in birch pollen, mugwort pollen and celery by means of immunoblotting. Inhibition studies were performed by preincubation of sera with extracts of birch pollen, mugwort pollen, and celery.

RESULTS

We identified three groups of proteins--homologues of Bet v 1 and birch profilin (Bet v 2) as well as a group of proteins with a molecular range of 46 to 60 kD--displaying IgE-cross-reactivity, which were shared by birch pollen and celery. Two of these groups of allergens (profilin and the 46 to 60 kD proteins) were also present in mugwort pollen. In this paper we demonstrate that most cross-reacting allergens present in mugwort pollen and celery can also be detected in birch pollen extract.

CONCLUSION

Therefore we propose, from a serological point of view, to extend the mugwort-celery syndrome to the birch-mugwort-celery syndrome.

High-level expression in Escherichia coli and purification of recombinant plant profilins: comparison of IgE-binding capacity and allergenic activity

Because of their structural similarity and ubiquitous distribution as actin binding proteins, plant profilins represent important cross-reactive allergens for almost 20% of patients suffering from Type I allergy to pollen and other plant products. The cDNAs coding for three birch profilin variants (Tyr44, Glu47, and Asn47), timothy grass profilin, and three tobacco profilin isoforms (ntprof1-3) were expressed at high levels in Escherichia coli as non-fusion proteins. The recombinant plant profilins were purified to homogeneity by poly (L-proline) affinity chromatography and showed comparable capacity to bind IgE-antibodies from profilin allergic patients. All recombinant plant profilins elicited dose-dependent histamine release from basophils of a profilin allergic patient and induced immediate type skin reactions. It is concluded that profilins from different plant species share IgE-epitopes and allergenic properties. Plant profilins therefore constitute a family of functional pan-allergens which may substitute each other for diagnosis and specific immunotherapy.

Sequence comparisons of the CDR3 hyper-variable loops of human T cell receptors specific for three major T cell epitopes of the birch pollen allergen Bet v 1

We have analysed the T cell receptor (TCR) alpha and beta chain sequences of 16 human CD4+ T cell clones (TCCs) specific for three important epitopes of the major birch pollen allergen Bet v 1. The TCCs were raised from the peripheral blood of eight patients with birch pollen allergy, showing allergic rhino-conjunctivitis and allergic asthma. The TCCs from these individuals were specific for Bet v 1-derived peptides: amino acids (aa)77-92 (epitope 1), aa93-108 (epitope 2) and aa113-126 (epitope 3). The DNA sequence analysis of the TCRAV and BV regions revealed heterogeneous repertoires for recognition of the peptides. Multiple combinations of AV/AJ and BV/BJ were used. However, some inter-individual restriction was evident. A limited selection of AVS and the normally infrequently used BV1S4 was obvious in TCCs specific for epitope 1. The TCRBV13 was more frequent in TCCs recognizing epitope 3. A very narrow distribution in length could be seen in the CDR3 sequences of the beta chain of TCRs with specificity for epitopes 1 and 2. Inter-individual positional micro-restriction was observed for the aa motif LR in the tCDR3 (epitope 1), for the aa residue M in the alphaCDR3 and for the aa residue G in the betaCDR3 (epitope 3). Our results illustrate clearly that each antigenic peptide derived from a single allergen, is capable of selecting different characteristics in the responding repertoire of TCRs, thus increasing the complexity of allergen-recognition by T lymphocytes. Therefore, our findings limit the potential use of TCR targeted therapeutical strategies in Type I allergy.

[Serologic and skin test diagnosis of birch pollen allergy with recombinant Bet v 1, the chief allergen of birch]

BACKGROUND

Type I allergy represents a severe health problem in industrialized countries where up to 20% of the population suffers 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 1, 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 1. 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 1 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, Westernblot) or by skin testing (skin-prick, intradermal test) with recombinant Bet v 1.

CONCLUSION

Our results document that recombinant Bet v 1 produced in bacterial expression systems allows accurate in vitro and in vivo diagnosis of birch pollen allergy in > 95% of birch pollen allergic patients.

Comparison of recombinant timothy grass pollen allergens with natural extract for diagnosis of grass pollen allergy in different populations

BACKGROUND

Complementary DNAs coding for the major timothy grass pollen (Phleum pratense) allergens Phl p 1, Phl p 2, and Phl p 5 and birch profilin were isolated, expressed as recombinant nonfusion proteins in Escherichia coli, and purified.

OBJECTIVE

In this study the in vitro IgE-binding capacity of recombinant Phl p 1, Phl p 2, Phl p 5, and birch profilin and their IgE recognition frequencies were investigated by using sera from different populations.

METHODS

One hundred eighty-three sera from patients allergic to grass pollen were obtained from different populations in Europe, Japan, and Canada. The sera were selected according to clinical criteria, skin testing, and RAST (CAP system; Pharmacia, Uppsala, Sweden) and then tested for IgE reactivity with natural and purified recombinant timothy grass pollen allergens by ELISA and Western blot.

RESULTS

Most (94.5%) of the patients allergic to grass pollen could be diagnosed with a combination of recombinant Phl p 1, Phl p 2, Phl p 5, and profilin by means of ELISA. Sera that did not react with the recombinant allergens contained low levels of timothy grass pollen-specific IgE. Although considerable variability in IgE recognition frequency of the recombinant allergens was observed in certain populations, a good correlation was found between natural timothy CAP results and the combination of recombinant allergens in all 183 tested sera (r = 0.87).

CONCLUSIONS

Despite considerable variability in the IgE recognition frequency, purified recombinant timothy grass pollen allergens (Phl p 1, Phl p 2, Phl p 5) and profilin permitted successful in vitro diagnosis of grass pollen allergy in 94.5% of allergic individuals from different populations. The addition of other recombinant allergens (e.g., recombinant Phl p 4) would only slightly improve the in vitro test sensitivity.

Secondary structure and tertiary fold of the birch pollen allergen Bet v 1 in solution

Bet v 1 is the major birch pollen allergen and therefore the main cause of type I allergies observed in early spring. It is composed of 159 amino acid residues adding up to a molecular mass of 17 kDa. We determined the secondary structure and tertiary fold of full-length Bet v 1 by NMR spectroscopy. Two- and three-dimensional NMR measurements suggest that Bet v 1 is a globular monomer in solution with a high content of well defined secondary structure. Of the total of 159 residues, 135 could be sequentially assigned, using an improved assignment strategy based mainly on heteronuclear experiments. An improved strategy for structure calculation revealed three helices and two beta-sheets as major elements of secondary structure. The globular tertiary structure is mainly stabilized by two antiparallel beta-sheets. The two helices at the C terminus are in accordance with the results from the solution structure of the chemically synthesized peptide Bet v 1-(125-154). This peptide is composed of two helices connected by a hinge. The structural features of Bet v 1 are highly similar to those found in the Ambrosia allergen Amb t V.

Peripheral blood dendritic cells express Fc epsilon RI as a complex composed of Fc epsilon RI alpha- and Fc epsilon RI gamma-chains and can use this receptor for IgE-mediated allergen presentation

Originally limited to basophils and mast cells, the spectrum of high affinity IgE receptor (Fc epsilon RI-bearing cells has expanded recently to include Langerhans cells, dermal dendritic cells (DC), monocytes, and eosinophils. As a result of studies on the distribution, structure, and function of Fc epsilon RI on APCs, we discovered a minor nonbasophil, nonmonocyte PBMC population that can bind IgE via Fc epsilon RI. This receptor occurs on the surface of these cells as a multimeric structure containing Fc epsilon RI alpha- and Fc epsilon RI gamma-chains but, unlike its counterpart on basophils, lacking Fc epsilon RI beta. Further experiments revealed that these Fc epsilon RI alpha gamma-expressing cells closely resemble peripheral blood DC by immunophenotype (HLA-DRhigh, HLA-DQhhigh; CD4+, CD11a+, CD32+, CD33+, B7/2 (CD86)+; CD11blow, CD14low, CD40low, CD54low, CD64low) and cell morphology. These features allowed us to isolate Fc epsilon RI-expressing DC from the peripheral blood and to investigate their immunostimulatory properties. We found Fc epsilon RI-positive DC to be efficient stimulators of both primary (allogeneic MLR) and Fc epsilon RI/IgE-dependent, secondary T cell responses at low cell numbers. Thus, Fc epsilon RI-expressing DC may not only amplify established type I allergic immune reactions but, unlike Fc epsilon RI-positive semiprofessional APCs, may be able to prime naive T cells to common and/or cryptic epitopes of IgE-reactive Ags.

Human IgG monoclonal antibodies that modulate the binding of specific IgE to birch pollen Bet v 1

Birch pollen allergy is a very frequent pathology in Europe and North America. More than 95% of the tree pollen allergic patients display IgE reactivity against Bet v 1, the major birch pollen allergen. Starting with PBL from a patient desensitized by immunotherapy, we have generated five B cell lines (BAB1 to BAB5) that secrete human IgG mAbs of high affinity for Bet v 1. Although competition studies indicated that these human IgG mAb recognized different epitopes, broad cross-reactivity was found with Bet v 1 homologous allergens present in tree pollens and plant-derived foods. When tested for interference with allergic patients' IgE, BAB1 inhibited (by 80-100%) the binding of IgE to nitrocellulose-blotted Bet v 1, while BAB2 enhanced it. The biologic significance of the ability of BAB1 to interfere with patients' IgE binding is indicated by the finding that BAB1 completely inhibited Bet v 1-induced histamine release from allergic patients' basophils. Allergen-specific human IgG mAbs such as BAB1, which presents high blocking activity in both immunochemical and cellular IgE competition experiments, might have therapeutical application.

Peripheral blood dendritic cells express Fc epsilon RI as a complex composed of Fc epsilon RI alpha- and Fc epsilon RI gamma-chains and can use this receptor for IgE-mediated allergen presentation

Originally limited to basophils and mast cells, the spectrum of high affinity IgE receptor (Fc epsilon RI-bearing cells has expanded recently to include Langerhans cells, dermal dendritic cells (DC), monocytes, and eosinophils. As a result of studies on the distribution, structure, and function of Fc epsilon RI on APCs, we discovered a minor nonbasophil, nonmonocyte PBMC population that can bind IgE via Fc epsilon RI. This receptor occurs on the surface of these cells as a multimeric structure containing Fc epsilon RI alpha- and Fc epsilon RI gamma-chains but, unlike its counterpart on basophils, lacking Fc epsilon RI beta. Further experiments revealed that these Fc epsilon RI alpha gamma-expressing cells closely resemble peripheral blood DC by immunophenotype (HLA-DRhigh, HLA-DQhhigh; CD4+, CD11a+, CD32+, CD33+, B7/2 (CD86)+; CD11blow, CD14low, CD40low, CD54low, CD64low) and cell morphology. These features allowed us to isolate Fc epsilon RI-expressing DC from the peripheral blood and to investigate their immunostimulatory properties. We found Fc epsilon RI-positive DC to be efficient stimulators of both primary (allogeneic MLR) and Fc epsilon RI/IgE-dependent, secondary T cell responses at low cell numbers. Thus, Fc epsilon RI-expressing DC may not only amplify established type I allergic immune reactions but, unlike Fc epsilon RI-positive semiprofessional APCs, may be able to prime naive T cells to common and/or cryptic epitopes of IgE-reactive Ags.

Human IgG monoclonal antibodies that modulate the binding of specific IgE to birch pollen Bet v 1

Birch pollen allergy is a very frequent pathology in Europe and North America. More than 95% of the tree pollen allergic patients display IgE reactivity against Bet v 1, the major birch pollen allergen. Starting with PBL from a patient desensitized by immunotherapy, we have generated five B cell lines (BAB1 to BAB5) that secrete human IgG mAbs of high affinity for Bet v 1. Although competition studies indicated that these human IgG mAb recognized different epitopes, broad cross-reactivity was found with Bet v 1 homologous allergens present in tree pollens and plant-derived foods. When tested for interference with allergic patients' IgE, BAB1 inhibited (by 80-100%) the binding of IgE to nitrocellulose-blotted Bet v 1, while BAB2 enhanced it. The biologic significance of the ability of BAB1 to interfere with patients' IgE binding is indicated by the finding that BAB1 completely inhibited Bet v 1-induced histamine release from allergic patients' basophils. Allergen-specific human IgG mAbs such as BAB1, which presents high blocking activity in both immunochemical and cellular IgE competition experiments, might have therapeutical application.

High-level expression of tree pollen isoallergens in Escherichia coli

cDNAs coding for the major allergen of alder (Alnus glutinosa) pollen Aln g 1, for nine isoforms of Bet v 1, the major birch (Betula verrucosa) pollen allergen, and for four isoforms of Cor a 1, the major allergen of hazel (Corylus avellana) pollen, were inserted into the plasmid pMW175 or pMW 172 and expressed in Escherichia coli as recombinant non-fusion proteins. These constructs produced between 20 and 160 mg protein/l. The recombinant tree pollen isoallergens were tested in immunoblots for their antibody binding properties. For this purpose, we used two monoclonal antibodies (BIP 1 and BIP 4) raised against natural Bet v 1, a polyclonal rabbit anti-recombinant Bet v 1a, as well as serum IgE from allergic patients. Our results show that this expression system is suitable for the production of milligram amounts of tree pollen isoallergens which can be used for the characterization of allergenic epitopes recognized by T and B cells.

Characterization of Phl p 4, a major timothy grass (Phleum pratense) pollen allergen

BACKGROUND

Group 4 grass pollen allergens represent glycoproteins with a molecular weight of 50 to 60 kd, which are present in many grass species. Almost 75% of patients allergic to grass pollen display IgE reactivity to group 4 allergens, which hence can be regarded as major grass pollen allergens.

OBJECTIVE

In this study attempts were made to obtain information regarding the immunologic properties, localization, and occurrence of Phl p 4 and related allergens.

METHODS

Phl p 4 was detected in timothy grass pollen extracts by immunoblotting with serum IgE and monoclonal antibodies and was localized in pollen by immunoelectron microscopy. A peptide sequence from Phl p 4 was obtained by amino acid sequencing. The resistance of Phl p 4 against trypsin was analyzed after trypsin treatment of timothy grass pollen extracts with serum IgE and monoclonal antibodies. Cross-reactivities between Phl p 4 and Amb a 1, the major allergen of ragweed, were studied by using monoclonal antibodies and by IgE- inhibition studies.

RESULTS

Phl p 4 was characterized as a trypsin-resistant major timothy grass pollen allergen. By immunoelectron microscopy Phl p 4 was localized in the exine, cytoplasm, and amyloplast of timothy grass pollen. significant sequence similarities of a Phl p 4 10 amino acid peptide with Amb a 1, the major ragweed allergen, could be found. The immunologic similarity of Phl p 4 and Amb a 1 was confirmed by cross-reactivity of monoclonal antibodies and patients' IgE.

CONCLUSION

Phl p 4 represents a trypsin-resistant major timothy grass pollen allergen with immunologic similarities to the major ragweed allergen Amb a 1 and therefore must be considered an important cross-reactive component in grass pollen and weed pollen allergy.

Evidence for an alpha helical T cell epitope in the C-terminus of the main birch pollen allergen Bet V 1

Secondary structure prediction of the main birch pollen allergen Bet v 1 was found to be in good agreement with the secondary structural elements found by analysing the Bet v 1 circular dichroism data. According to both experiment and prediction, 32% of 160 amino acids participate in alpha helices, 21% in beta sheets, 24% in turns, and 23% in other structural motifs. The peptide LRAVESYLLAHS which represents one of the major T cell epitopes on Bet v 1 was shown to have a high propensity to form an alpha helix. Time-resolved fluorescence anisotropy measurements of the allergen revealed an overall rotational correlation time of 7.35 ns, which corresponds to a hydrodynamic molecular radius of 19.2 A. This refers to a monomeric Bet v 1 molecule in solution, which is also reflected in the narrow band width of the 1H-NMR spectrum. The results presented here are in good agreement with the recently solved NMR structure of Amb t 5: both allergens are monomers in solution with an extended C-terminal alpha helix containing a major T cell epitope.

Construction of a combinatorial IgE library from an allergic patient. Isolation and characterization of human IgE Fabs with specificity for the major timothy grass pollen allergen, Phl p 5

To characterize human IgE antibodies with specificity for a major allergen at the molecular level, we have constructed an IgE combinatorial library from a grass pollen allergic patient. cDNAs coding for IgE heavy chain fragments and for light chains were reverse-transcribed and polymerase chain reaction-amplified from RNA of peripheral blood lymphocytes and randomly combined in plasmid pComb3H to yield a combinatorial library of 5 x 10(7) primary clones. IgE Fabs with specificity for Phl p 5, a major timothy grass pollen allergen, were isolated by panning. Sequence analysis showed that the 4 of the Fabs used the same heavy chain fragments which had combined with different kappa light chains. Soluble recombinant IgE Fabs were purified by affinity chromatography to Phl p 5 and, like natural IgE antibodies, cross-reacted with group 5 allergens from different grass species. The described approach should facilitate studies on the molecular interaction between IgE antibodies and allergens and encourages the consideration of specific IgE Fabs that are capable of interfering with allergen-IgE binding as potential therapeutic tools.

Skin testing with recombinant allergens rBet v 1 and birch profilin, rBet v 2: diagnostic value for birch pollen and associated allergies

OBJECTIVE

This study assesses the value of two recombinant birch allergens for diagnosis of patients sensitized to birch pollen with or without associated food allergy.

METHODS

Fifty-one patients with positive skin test responses to Betulaceae and seven nonallergic control subjects were investigated; specific IgE antibodies were evaluated by specific immunoassay and blot immunodetection.

RESULTS

Among 51 patients, 47 reacted to rBet v 1 and 10 to rBet v 2. Seven patients reacted to both recombinant allergens. In skin prick tests we found a correlation between the wheal produced by the commercial birch extract and the wheal produced by rBet v 1. Among 47 patients with positive test responses to rBet v 1, 83% had IgE binding to the Bet v 1 protein as determined by immunoblotting. Among 10 patients sensitized to rBet v 2, six had IgE binding to Bet v 2. Eleven patients with negative results, as determined by immunoblotting, had low levels of birch IgE in the sera (less than 10 kU/L) and low concentrations of IgE to rBet v 1 or rBet v 2 in ELISA. The nonallergic control subjects (n = 7) did not react to rBet v 1 or rBet v 2 in skin prick tests, nor did they have detectable amounts of specific IgE to rBet v 1 or rBet v 2. Histamine release tests confirmed sensitization to Bet v 1 in two patients with discordant results; for Bet v 2, one patient had positive results only at a high concentration, and one had results that remained negative. Thirty-four patients had birch pollinosis, and all reacted to rBet v 1. Patients who were monosensitized to birch never reacted to rBet v 2. Sensitization to rBet v 2 was only found in patients who reacted to other pollens (mainly grass). Twenty-nine patients demonstrated allergy to apples, cherries, or hazelnuts; and all reacted to rBet v 1. Among 11 patients with allergy to Umbelliferae, only three reacted to rBet v 2.

CONCLUSIONS

Use of the two recombinant allergens (rBet v 1 and rBet v 2) always permits the diagnosis of birch sensitization. Sensitization to rBet v 1 is specific for birch and Rosaceae allergies, whereas sensitization to birch profilin, Bet v 2, is encountered in multisensitized subjects and is not always related to Umbelliferae allergy.

Immunological and structural similarities among allergens: prerequisite for a specific and component-based therapy of allergy

It is known that allergic patients are frequently co-sensitized against different allergen sources. Progress made in the field of allergen characterization by molecular biological techniques has now revealed that sensitization against different allergen sources can be explained as cross-reactivity of IgE antibodies with structurally and immunologically related components present in these allergen sources. This review defines groups of cross-reactive plant allergens with significant sequence homology. The similarities among allergens may facilitate allergy diagnosis by using a few representative cross-reactive allergens to determine the patient's IgE reactivity profile (allergogram). According to that typing, a few cross-reactive allergens, carrying most of the relevant IgE epitopes, may then be selected for patient-tailored specific therapy.

Expression of Zm13, a pollen specific maize protein, in Escherichia coli reveals IgE-binding capacity and allergenic potential

Plant proteins belong to the most frequent elicitors of type I allergic symptoms in industrialized countries. Several relevant plant allergens have been found to be either specifically expressed or highly upregulated in mature pollen. The cDNA coding for a pollen specific maize protein, Zm13, shows significant sequence homology with a number of pollen or anther specific proteins from monocot and dicot plants as well as with recently described allergens from olive and rye grass. To test whether the Zm13 protein might possess IgE-binding capacity, Zm13 was expressed in E. coli. The coding region of Zm13 was PCR amplified from a genomic clone and expressed as a glutathione-S-transferase fusion protein. The recombinant Zm13 fusion protein bound a Zm13 specific rabbit antiserum and reacted with serum IgE from grass pollen allergic patients indicating that Zm13 and homologous proteins represent a family of conserved plant allergens.

Immunologic characterization of purified recombinant timothy grass pollen (Phleum pratense) allergens (Phl p 1, Phl p2, Phl p 5)

BACKGROUND

Grass pollen allergens belong to the potent elicitors of type I allergy. Approximately 40% of allergic individuals display IgE reactivity with grass pollen allergens. In previous studies we have reported the complementary DNA cloning and expression in Escherichia coli of three of the most relevant timothy grass pollen allergens: Phl p 1, Phl p 2, and Phl p 5.

OBJECTIVE

To achieve high level expression of immunologically active timothy grass pollen allergens in E. coli, the cDNAs were inserted into expression plasmids.

METHODS

The three recombinant grass pollen allergens were expressed at high levels in E. coli as recombinant nonfusion proteins, purified by conventional protein chemical methods and tested for their IgE-binding capacity by immunoblot and ELISA, as well as in histamine release assays.

RESULTS

Milligram amounts of pure recombinant allergens were obtained from cultured E. coli. IgE binding to purified recombinant Phl p 1, Phl p 2, and Phl p 5 could be demonstrated by immunoblot and ELISA. With ELISAs the percentage of grass pollen-specific IgE directed against the individual recombinant allergens could be estimated. In addition, the purified recombinant timothy grass pollen allergens induced dose-dependent and specific histamine release from patients' blood basophils.

CONCLUSION

Purified recombinant timothy grass pollen allergens represent useful tools for diagnosis and therapy of grass pollen allergy.

Common IgE-epitopes of recombinant Phl p I, the major timothy grass pollen allergen and natural group I grass pollen isoallergens

Grass pollen allergens are potent elicitors of Type I allergy. More than 95% of grass pollen allergic patients display IgE-cross-reactivity to group I grass pollen allergens of different grass species. A cDNA coding for the major timothy grass pollen allergen, Phl p I, was isolated previously. To investigate the presence of common IgE-epitopes among naturally occurring group I grass pollen isoallergens, Phl p I was expressed in Escherichia coli and used for IgE-absorption experiments. Recombinant Phl p I was able to inhibit IgE-binding to most of group I isoallergens from seven grass species as identified by two dimensional electrophoresis. When tested in competitive ELISA experiments, recombinant Phl p I bound a high percentage of grass pollen specific IgE. The results indicate that recombinant Phl p I shares many of the IgE-epitopes with natural group I grass pollen allergens and hence may represent a useful tool for specific diagnosis and therapy of grass pollen allergy.

Dissection of immunoglobulin E and T lymphocyte reactivity of isoforms of the major birch pollen allergen Bet v 1: potential use of hypoallergenic isoforms for immunotherapy

We dissected the T cell activation potency and the immunoglobulin (Ig) E-binding properties (allergenicity) of nine isoforms of Bet v 1 (Bet v 1a-Bet v 1l), the major birch pollen allergen. Immunoblot experiments showed that Bet v 1 isoforms differ in their ability to bind IgE from birch pollen-allergic patients. All patients tested displayed similar IgE-binding patterns toward each particular isoform. Based on these experiments, we grouped Bet v 1 isoforms in three classes: molecules with high IgE-binding activity (isoforms a, e, and j), intermediate IgE-binding (isoforms b, c, and f), and low/no IgE-binding activity (isoforms d, g, and 1). Bet v 1a, a recombinant isoform selected from a cDNA expression library using IgE immunoscreening exhibited the highest IgE-binding activity. Isoforms a, b, d, e, and 1 were chosen as representatives from the three classes for experimentation. The potency of each isoallergen to activate T lymphocytes from birch pollen-allergic patients was assayed using peripheral blood mononuclear cells, allergen-specific T cell lines, and peptide-mapped allergen-specific T cell clones. Among the patients, some displayed a broad range of T cell-recognition patterns for Bet v 1 isoforms whereas others seemed to be restricted to particular isoforms. In spite of this variability, the highest scores for T cell proliferative responses were observed with isoform d (low IgE binder), followed by b, 1, e, and a. In vivo (skin prick) tests showed that the potency of isoforms d and 1 to induce typical urticarial type 1 reactions in Bet v 1-allergic individuals was significantly lower than for isoforms a, b, and e. Taken together, our results indicate that hypoallergenic Bet v 1 isoforms are potent activators of allergen-specific T lymphocytes, and Bet v 1 isoforms with high in vitro IgE-binding activity and in vivo allergenicity can display low T cell antigenicity. Based on these findings, we propose a novel approach for immunotherapy of type I allergies: a treatment with high doses of hypoallergenic isoforms or recombinant variants of atopic allergens. We proceed on the assumption that this measure would modulate the quality of the T helper cell response to allergens in vivo. The therapy form would additionally implicate a reduced risk of anaphylactic side effects.

Toward selective elicitation of TH1-controlled vaccination responses: vaccine applications of bacterial surface layer proteins

Bacterial surface layer proteins have been utilized as combined vaccine carrier/adjuvants and offer a number of advantages in these applications. The crystalline protein arrays contain functional groups in precisely defined orientations for coupling of haptens. Conventional applications of S-layer vaccines do not cause observable trauma or side effects. Depending on the nature of the S-layer preparations, antigenic conjugates will induce immune responses of a predominantly cellular or predominantly humoral nature. Immune responses to S-layer-hapten conjugates are also observed following oral/nasal application. In the present contribution, the status of investigations with S-layer conjugates in three main immunological projects is reviewed. In a project aimed at immunotherapy of cancer, conjugates of S-layer with small, tumor-associated oligosaccharides have been found to elicit hapten-specific DTH responses. An enlarged program of chemical synthesis has now been initiated to prepare a complete set of mucin-derived, tumor-associated oligosaccharides and their chemically modified analogues for elicitation of cell-mediated immune responses to certain tumors in humans. In another application, oligosaccharides derived from capsules of Streptococcus pneumoniae type 8 have been linked to S-layer proteins and have been found to elicit protective antibody responses in animals. Most recently, allergen S-layer conjugates have been prepared with the intention to suppress the TH2-directed, IgE-mediated allergic responses to Bet nu 1, the major allergen of birch pollen. In the former two applications, the S-layer vaccine technology appears to offer the versatility needed to direct vaccination responses toward predominant control by TH1 or TH2 lymphocytes to meet the different therapeutic or prophylactic requirements in each case. In the third application, work has progressed to a preliminary stage only.

Biological and immunological importance of Bet v 1 isoforms

In 2D-PAGE analysis of Bet v 1, the major birch pollen allergen, up to 12 isoforms can be demonstrated that differ in their isoelectric points from about pH 4.9 to pH 5.9. The molecular weights of these isoforms seem to be rather similar, but minor variations can also be seen. Preliminary experiments with birch leaves seem to indicate that in aging leaves some isoforms can be found that do not occur in pollen. In birch cells cultured in vitro, Bet v 1 isoforms can be induced by bacterial infection that do not occur in pollen (Swoboda et al. (1995), Pant, Cell and Environment 18, 865-874). In a recent paper (Swoboda et al (1995)., J. Biol. Chem. 270, 2607-2613) we show that in natural Bet v 1 from pollen the isoforms are due to different protein sequences. The derived protein sequences of 10 different isoforms (corresponding to 13 different cDNAs) were determined and confirmed by plasma desorption mass spectrometry of purified natural Bet v 1 after trypsin and endoproteinase Glu-C digestion. These experiments also showed that pollen Bet v 1 isoforms were reactive to patients' sera to different degrees and that common post-synthetic modifications (besides N-terminal methionine cleavage) did not occur on Bet v 1. Recombinant isoforms were produced in E. coli, purified and tested with selected patients allergic to birch pollen (Ferreira et al., J. Exp. Med., in the press). The pattern of IgE binding to Bet v 1 isoforms widely differs. Also, T-cell clones from individual patients in some cases are specific to peptides occurring only in certain isoforms. It was of particular interest that three of the naturally occurring pollen Bet v 1 isoforms do not or hardly bind IgE of untreated patients allergic to Bet v 1. However, a comparison of IgE reactivity in patients before and after conventional immunotherapy with natural pollen extract clearly showed that this form of immunotherapy induced IgE to the isoforms that had been unreactive in untreated patients. One of these, Bet v 1d, showed a particularly strong potency towards T-cell stimulation. The isoform(s) that do not bind IgE in untreated patients but still show T-cell reactivity could be potentially utilized for a new form of immunotherapy that avoids the risk of anaphylaxis.

Induction of IgE antibodies with predefined specificity in rhesus monkeys with recombinant birch pollen allergens, Bet v 1 and Bet v 2

BACKGROUND

Recombinant birch pollen allergens Bet v 1 and Bet v 2 (birch profilin) have been characterized in vitro previously.

OBJECTIVE

To establish a close-to-man model of type I allergy, recombinant birch pollen allergens were injected into rhesus monkeys.

METHODS

The allergens were expressed in Escherichia coli, purified to homogeneity and injected into rhesus monkeys with aluminium hydroxide as adjuvans. The development of type I allergy was monitored by measurement of specific IgE, in vitro histamine release tests, cellular proliferation assays, skin testing, and bronchial provocation tests.

RESULTS

Immunized rhesus monkeys displayed symptoms of type I allergy comparable to those of allergic patients, and cross-reactivity of IgE antibodies with Bet v 1 and Bet v 2 homologous allergens was observed. Systemic application of corticosteroids during secondary immunizations suppressed specific antibody responses.

CONCLUSION

Recombinant birch pollen allergens (Bet v 1 and Bet v 2) were effective to establish a close-to-man model of natural type I allergy in rhesus monkeys, allowing study of specific IgE regulation in vivo.