Crossreactivity and T-cell epitope specificity of Bet v 1-specific T cells suggest the involvement of multiple isoallergens in sensitization to birch pollen

T cells specific to multiple Bet v 1 peptides are highly cross-reactive toward the corresponding peptides from the homologous group of tree pollens

Background

Allergens from Fagales trees frequently cause spring allergy in Europe, North America, and some parts of Asia. The definition of the birch homologous group, which includes birch (Bet v), oak (Que a), alder (Aln g), hazel (Cor a), hornbeam (Car b), beech (Fag s), and chestnut (Cas s), is based on high allergen sequence identity and extensive IgE cross-reactivity. Clinical effect was seen during the alder/hazel, birch, and oak pollen seasons after treatment with tree SLIT-tablets containing only birch allergen extract. Here, we characterize T-cell reactivity with respect to epitope specificities and cross-reactivity toward various Bet v 1 family members, (PR-10/group 1 major allergens). This cross-reactivity may be part of the immunological basis of clinical effect or cross-protection when exposed to birch homologous tree species.

Method

T-cell lines were generated from 29 birch-allergic individuals through stimulation of peripheral blood mononuclear cells (PBMCs) with birch/Bet v or oak/Que a allergen extracts. T-cell responses to allergen extracts, purified group 1 allergens, and overlapping 20-mer peptides (Bet v 1, Aln g 1, Cor a 1, and Que a 1) were investigated by T-cell proliferation and cytokine production. Cross-reactivity was evaluated based on Pearson's correlations of response strength and further investigated by flow cytometry using tetramer staining for homologous peptide pairs.

Results

T-cell reactivity toward extracts and group 1 allergens from across the birch homologous group was observed for birch/Bet v as well as oak/Que a T-cell lines. T-cell lines responded to multiple Bet v 1 homologous peptides from Aln g 1 and Cor a 1 and a subset of Que a 1 peptides. Significant Pearson's correlations between frequently recognized peptides derived from Bet v 1 and the corresponding peptides derived from alder, hazel, and oak strongly supported the T-cell cross-reactivity toward these allergens. Cross-reactivity between birch and birch homologous peptides was confirmed by pMHCII tetramer staining.

Conclusion

T cells from birch tree pollen allergic individuals respond to multiple trees within the birch homologous group in accordance with the level of sequence homology between Bet v 1 family members, (PR-10 allergens) from these allergen sources, confirming the basis for clinical cross-protection.

Bet v 1-independent sensitization to major allergens in Fagales pollen: Evidence at the T-cell level

BACKGROUND

In birch-dominated areas, allergies to pollen from trees of the order Fagales are considered to be initiated by the major birch pollen allergen Bet v 1. However, the sensitizing activity of Bet v 1-homologs in Fagales pollen might be underestimated. Allergen-specific T-cells are crucial in the sensitization process. The T-cell response to major allergens from alder, hazel, oak, hornbeam, chestnut, beech, and chestnut pollen has not yet been analyzed. Here, we characterized the cellular cross-reactivity of major allergens in Fagales pollen with Bet v 1.

METHODS

T-cell-lines (TCL) were established from allergic individuals with Aln g 1, Car b 1, Ost c 1, Cor a 1, Fag s 1, Cas s 1, and Que a 1, and tested for reactivity with Bet v 1 and synthetic overlapping 12-mer peptides representing its primary sequence. Aln g 1-specific TCL was additionally tested with Aln g 1-derived peptides and all allergens. IgE-competition experiments with Aln g 1 and Bet v 1 were performed.

RESULTS

T-cell-lines initiated with Fagales pollen allergens varied strongly in their reactivity with Bet v 1 and by the majority responded stronger to the original stimulus. Cross-reactivity was mostly restricted to the epitope Bet v 1142-153 . No distinct cross-reactivity of Aln g 1-specific T-cells with Bet v 1 was detected. Among 22 T-cell epitopes, Aln g 1 contained two immunodominant epitopes. Bet v 1 inhibited IgE-binding to Aln g 1 less potently than Aln g 1 itself.

CONCLUSION

The cellular cross-reactivity of major Fagales pollen allergens with Bet v 1 was unincisive, particularly for Aln g 1, most akin to Bet v 1. Our results indicate that humoral and cellular responses to these allergens are not predominantly based on cross-reactivity with the major birch pollen allergen but suggest a Bet v 1-independent sensitization in individuals from birch tree-dominated areas.

Allergy to oak pollen in North America

Background: Oak pollen is an important allergen in North America. The genus Quercus (oak) belongs to the family Fagaceae under the order Fagales. Objective: The objective of this article was to narratively review the oak pollen season, clinical and epidemiologic aspects of allergy to oak pollen, oak taxonomy, and oak allergen cross-reactivity, with a focus on the North American perspective. Methods: A PubMed literature review (no limits) was conducted. Publications related to oak pollen, oak-related allergic rhinitis with or without conjunctivitis, and oak-related allergic asthma were selected for review. Results: Oak species are common throughout the United States and contribute up to 50% to overall atmospheric pollen loads. Mean peak oak pollen counts can reach >2000 grains/m³. The start of the oak pollen season generally corresponds to the seasonal shift from winter to spring based on latitude and elevation, and may begin as early as mid February. The duration of the season can last > 100 days and, in general, is longer at lower latitudes. In the United States, ∼30% of individuals with allergy are sensitized to oak. The oak pollen season correlates with increased allergic rhinitis symptom-relieving medication use and asthma-related emergency department visits or hospitalizations. Oak falls within the birch homologous group. Extensive immunologic cross-reactivity has been demonstrated between oak pollen and birch pollen allergens, and, more specifically, their major allergens Que a 1 and Bet v 1. The cross-reactivity between oak and birch has implications for allergy immunotherapy (AIT) because guidelines suggest selecting one representative allergen within a homologous group for AIT, a principle that would apply to oak. Conclusion: Allergy to oak pollen is common in North America and has a substantial clinical impact. Oak pollen allergens are cross-reactive with birch pollen allergens, which may have implications for AIT.

Simplified AIT for allergy to several tree pollens-Arguments from the immune outcome analyses following treatment with SQ tree SLIT-tablet

BACKGROUND

The SQ tree SLIT-tablet (containing birch extract) proved clinically significant effects during the pollen season for birch as well as alder/hazel. Immune outcomes of this treatment for allergens from multiple birch homologous trees need further investigation. We hypothesize that birch pollen extract AIT modulates a highly cross-reactive immune response and that this may be the basis for the observed clinical cross-protection.

METHODS

Blood samples were collected from 397 birch allergic patients during SQ tree SLIT-tablet or placebo treatment (1:1) for up to 40 weeks. Serum IgE and IgG₄ specific to birch, and birch homologous tree pollens from alder, hazel, hornbeam, beech and chestnut were measured by ImmunoCAP. IgE-Blocking Factor (IgE-BF) for alder, birch and hazel during treatment was measured by Advia Centaur and blocking effects for birch and all these birch homologous tree pollens were further investigated by basophil activation (BAT). Antibody readouts were investigated in patient subsets. T-cell responses (proliferation) to allergen extracts and peptide pools (group 1 allergens) were investigated in T-cell lines from 29 untreated birch pollen-allergic individuals.

RESULTS

Significant Pearson correlations between serum IgE towards birch, alder, hazel, hornbeam and beech were observed (r-values > .86). T-cell reactivity was observed throughout the birch homologous group. Almost identical kinetics for changes in IgE towards birch, alder and hazel were observed during treatment and similar species-specific changes were seen for serum-IgG₄ . IgG₄ reactivity towards birch and alder, hazel, hornbeam and beech correlated significantly at end-of-treatment (r-values > .72). Treatment resulted in similar IgE-BF kinetics for alder, birch, and hazel and blocking of BAT for multiple trees in most actively treated patients investigated.

CONCLUSIONS

Systematic analyses of T-cell and antibody cross-reactivities before and during birch pollen extract AIT provide the immunological basis for the observed clinical effect of SQ tree SLIT-tablet treatment of tree pollen allergy induced by multiple trees in the birch homologous group.

Allergen hybrids - next generation vaccines for Fagales pollen immunotherapy

Background

Trees belonging to the order of Fagales show a distinct geographical distribution. While alder and birch are endemic in the temperate zones of the Northern Hemisphere, hazel, hornbeam and oak prefer a warmer climate. However, specific immunotherapy of Fagales pollen-allergic patients is mainly performed using birch pollen extracts, thus limiting the success of this intervention in birch-free areas.

Objectives

T cells are considered key players in the modification of an allergic immune response during specific immunotherapy (SIT), therefore we thought to combine linear T cell epitope-containing stretches of the five most important Fagales allergens from birch, hazel, alder, oak and hornbeam resulting in a Fagales pollen hybrid (FPH) molecule applicable for SIT.

Methods

A Fagales pollen hybrid was generated by PCR-based recombination of low IgE-binding allergen epitopes. Moreover, a structural-variant FPH4 was calculated by in silico mutagenesis, rendering the protein unable to adopt the Bet v 1-like fold. Both molecules were produced in Escherichia coli, characterized physico-chemically as well as immunologically, and tested in mouse models of allergic sensitization as well as allergy prophylaxis.

Results

Using spectroscopic analyses, both proteins were monomeric, and the secondary structure elements of FPH resemble the ones typical for Bet v 1-like proteins, whereas FPH4 showed increased amounts of unordered structure. Both molecules displayed reduced binding capacities of Bet v 1-specific IgE antibodies. However, in a mouse model, the proteins were able to induce high IgG titres cross-reactive with all parental allergens. Moreover, prophylactic treatment with the hybrid proteins prevented pollen extract-induced allergic lung inflammation in vivo.

Conclusion

The hybrid molecules showed a more efficient uptake and processing by dendritic cells resulting in a modified T cell response. The proteins had a lower IgE-binding capacity compared with the parental allergens, thus the high safety profile and increased efficacy emphasize clinical application for the treatment of Fagales multi-sensitization.

Superparamagnetic iron oxide nanoparticles conjugated to a grass pollen allergen and an optical probe

In this study we report the development of a bioconjugate between superparamagnetic iron oxide nanoparticles and Phl p5a (one of the major allergens from grass pollen). The bioconjugate also contains an optical probe (Alexa647) conjugated to the nanoparticle via biotin-streptavidin association. We show that this conjugate has a range of features that makes it a very promising candidate to image the localization of this allergen in vivo: (a) upon conjugation to the iron oxide nanoparticles, the allergen retains its ability to interact with IgE antibodies; (b) the magnetic properties of the iron oxide core of this bioconjugate are suitable for MR imaging; and (c) Alexa647 fluorophore retains its emission properties once attached to the iron oxide nanoparticles, yielding a dual modality MRI-optical probe.

Birch pollen immunotherapy results in long-term loss of Bet v 1-specific TH2 responses, transient TR1 activation, and synthesis of IgE-blocking antibodies

BACKGROUND

Early events of specific immunotherapy (SIT) are induction of allergen-specific IL-10-producing T(R)1 cells and production of IgG antibodies, but there is little knowledge about the long-term immune mechanisms responsible for sustained allergen tolerance.

OBJECTIVE

Bet v 1-specific immune responses of 16 patients with birch pollen allergy were characterized up to 54 months at defined time points before, during, and after a 3-year period of SIT.

METHODS

We sought to analyze allergen-specific T- and B-cell responses. Bet v 1-specific IL-5-, IFN-γ-, and IL-10-secreting T cells were quantified in peripheral blood, and birch pollen-specific IgE and IgG antibody levels were determined in serum. Furthermore, the inhibitory capacity of SIT-induced IgG was evaluated by blocking allergen binding to IgE and inhibition of facilitated allergen presentation.

RESULTS

Seasonal increases in Bet v 1-specific T(H)2 cell numbers ceased to appear after the first year of SIT without deviation to a T(H)1-dominated immune response. Furthermore, the frequency of IL-10-producing T(R)1 cells, which had increased during the first year of SIT, returned to pretreatment levels in the second year. In contrast, allergen-specific IgG antibody concentrations continuously increased during SIT but started to decrease after cessation of treatment. Functional analysis confirmed the ability of the IgG antibodies to inhibit IgE-allergen interactions, which peaked at the end of SIT but then slowly started to decrease.

CONCLUSION

Long-term allergen tolerance achieved by SIT is associated with the development of peripheral T-cell tolerance characterized by decreased reactivity of Bet v 1-specific T(H)2 cells and enriched allergen-specific IgG competing with IgE antibodies for allergen binding.

Interaction of allergens, major histocompatibility complex molecules, and T cell receptors: a 'ménage à trois' that opens new avenues for therapeutic intervention in type I allergy

T cells are major players in the initiation and perpetuation of the allergic immune response. In this review, we summarize the current knowledge on allergen recognition by T lymphocytes and address the components of the trimeric recognition complex: T cell receptors, major histocompatibility complex molecules, and allergen-derived peptides. Furthermore, possible implications of this scientific background for future therapeutic developments are discussed.

Clinical allergy to hazelnut and peanut: identification of T cell cross-reactive allergens

BACKGROUND

Peanut and tree nut allergies are life-threatening conditions for many affected individuals worldwide. Currently there is no cure. While co-allergy to peanut and tree nuts is a common clinical observation, and IgE cross-reactivity between peanut and tree nuts is reported, T cell cross-reactivity is poorly defined.

METHODS

Hazelnut-specific T cell lines were established using peripheral blood mononuclear cells from 5 subjects with co-allergy to hazelnut and peanut. These lines were stimulated with hazelnut and peanut extracts and purified major peanut allergens, Ara h 1 and Ara h 2. Proliferation was determined by (3)H-thymidine incorporation and secretion of key Th1 (IFN-γ) and Th2 (IL-5) cytokines analysed by ELISA.

RESULTS

Hazelnut-specific T cell lines from all 5 subjects proliferated upon stimulation with both hazelnut and peanut extracts and for 4 subjects, to Ara h 1 and/or Ara h 2. Proliferating cells were mainly CD4+ T cells and produced both IL-5 and IFN-γ in response to hazelnut and peanut stimulation. Mitogenicity of extracts and allergens was excluded by their lack of stimulation of house dust mite-specific T cells.

CONCLUSION

Our finding that hazelnut and peanut co-allergy is associated with cross-reactive T cell responses, driven partly by cross-reactivity to the major peanut allergens Ara h 1 and Ara h 2, points to future development of allergen immunotherapy by targeting cross-reactive T cells.

A CD26-controlled cell surface cascade for regulation of T cell motility and chemokine signals

Chemokines are key regulators of cell trafficking, and dipeptidyl peptidase IV/CD26 (CD26) inactivates chemokines. Here we show that the CD26-processed chemokines SDF1alpha/CXCL12 and RANTES/CCL5, in contrast to a control chemokine not processed by CD26, are potent inducers of cell surface expression of thrombospondin-1 (TSP-1) in T lymphocytes through a CD26-controlled mechanism and that TSP-1 stimulates expression of lipoprotein receptor related protein/CD91. Accordingly, intact TSP-1 and a peptide mimetic of a sequence in TSP-1 were sufficient to stimulate CD91 expression. The chemokine-induced expression of TSP-1 and CD91 was mimicked by inhibitors of CD26 and CXCL12 and CCL5 as well as inhibitors of CD26 stimulated polarized cytoplasmic spreading and migration through TSP-1. Silencing of CD26 using small interfering RNA or Ab-induced modulation of CD26 also increased TSP-1 expression and enhanced cytoplasmic spreading and T cell migration markedly. These results indicate that CD26 is an endogenous inhibitor of T cell motility through inhibition of TSP-1 expression and that chemokines stimulate cell polarity and migration through abrogation of the CD26-dependent inhibition. This suggests that T cell motility is regulated by a cascade of interacting cell surface molecules.

Bioinformatics approaches to classifying allergens and predicting cross-reactivity

Allergenic proteins from very different environmental sources have similar sequences and structures. This fact may account for multiple allergen syndromes, whereby a myriad of diverse plants and foods may induce a similar IgE-based reaction in certain patients. Identifying the common triggering protein in these sources, in silico, can aid designing individualized therapy for allergen sufferers. This article provides an overview of databases on allergenic proteins, and ways to identify common proteins that may be the cause of multiple allergy syndromes. The major emphasis is on the relational Structural Database of Allergenic Proteins (SDAP []), which includes cross-referenced data on the sequence, structure, and IgE epitopes of over 800 allergenic proteins, coupled with specially developed bioinformatics tools to group all allergens and identify discrete areas that may account for cross-reactivity. SDAP is freely available on the Web to clinicians and patients.

Functional Analysis of Birch Pollen Allergen Bet v 1-Specific Regulatory T Cells

Allergen-specific immunotherapy using peptides is an efficient treatment for allergic diseases. Recent studies suggest that the induction of CD4+ regulatory T (Treg) cells might be associated with the suppression of allergic responses in patients after allergen-specific immunotherapy. Our aim was to identify MHC class II promiscuous T cell epitopes for the birch pollen allergen Bet v 1 capable of stimulating Treg cells with the purpose of inhibiting allergic responses. Ag-reactive CD4+ T cell clones were generated from patients with birch pollen allergy and healthy volunteers by in vitro vaccination of PBMC using Bet v 1 synthetic peptides. Several CD4+ T cell clones were induced by using 2 synthetic peptides (Bet v 1(141-156) and Bet v 1(51-68)). Peptide-reactive CD4+ T cells recognized recombinant Bet v 1 protein, indicating that these peptides are produced by the MHC class II Ag processing pathway. Peptide Bet v 1(141-156) appears to be a highly MHC promiscuous epitope since T cell responses restricted by numerous MHC class II molecules (DR4, DR9, DR11, DR15, and DR53) were observed. Two of these clones functioned as typical Treg cells (expressed CD25, GITR, and Foxp3 and suppressed the proliferation and IL-2 secretion of other CD4+ T cells). Notably, the suppressive activity of these Treg cells required cell-cell contact and was not mediated through soluble IL-10 or TGF-beta. The identified promiscuous MHC class II epitope capable of inducing suppressive Treg responses may have important implication for the development of peptide-based Ag-specific immunotherapy to birch pollen allergy.

Endogenous thrombospondin-1 is a cell-surface ligand for regulation of integrin-dependent T-lymphocyte adhesion

Lymphocyte adhesion to cells and extracellular matrix (ECM) via integrins plays a pivotal role for the function of the immune system. We show here that endogenous thrombospondin-1 (TSP-1) is a cell-surface ligand for cis interaction of surface receptors in T lymphocytes controlled by integrins and the T-cell antigen receptor (TCR/CD3). Stimulation of CD3 triggers rapid surface expression of TSP-1 in quiescent T cells, whereas activated cells express TSP-1 constitutively. Endogenous TSP-1 is attached to lipoprotein receptor-related protein 1 (LRP1/CD91) and calreticulin (CRT) on the cell surface through its NH2-terminal domain. Adhesion via integrins to ICAM-1 or ECM components up-regulates TSP turnover dramatically from a low level in nonadherent cells, whereas CD3 stimulation inhibits TSP turnover through interference with CD91/CRT-mediated internalization. Integrin-associated protein (IAP/CD47) is essential for TSP turnover and adhesion through interaction with the C-terminal domain of TSP-1 in response to triggering signals delivered at the NH2-terminal. These results indicate that endogenous TSP-1 connects separate cell-surface receptors functionally and regulates T-cell adhesion.

A single amino acid substitution on the surface of a natural hevein isoform (Hev b 6.0202), confers different IgE recognition

Decreased immune reactivity of isoforms of major allergens has been reported. However, such claims have always been based on experiments with recombinant proteins. This work describes the molecular and physicochemical characterization of a hevein (Hev b 6.0201) natural isoform (Hev b 6.0202), which is present in rubber latex from Hevea brasiliensis. The isoallergen has a single substitution Asn14Asp, which gives rise to local differences in the surface potential, as observed from the crystal structure presented here. Besides, ELISA inhibition using serum pools of adult and pediatric patients showed reduced IgE-binding capacity ( approximately 27%) with the isoallergen. Overall, these results are relevant to delineate crucial residues involved in this dominant discontinuous epitope.

Immunobiology of grass pollen allergens

Among pollen allergens, grass pollen allergens are some of the most frequent contributors to allergic symptoms. Substantial progress has been made since the 1960s in the identification and characterization of the grass allergens. Members of this group belong to the Poaceae family, and have been classified into 13 distinct groups based on their structure, and their biological and immunologic properties. The major contributors to allergy and, hence, most studied among the grass allergens, are those belonging to groups 1 and 5. This review is focused on the structure and immunobiology of the grass allergens and highlights how recent advances in the field have contributed to superior diagnosis and immunotherapy for allergy to grass pollens.

Recombinant allergens for analysing T-cell responses

T-cell responses constitute a central element of allergic disease and a model for studying Th1 and Th2 cytokine pathways. Most studies to date have used extracts of allergens which contain variable quantities of different allergens and non-allergenic antigens. Recombinant allergens provide the tools for studying the responses to allergens in a reproducible and dose-dependent manner and the different T-cell responses of allergic and non-allergic subjects provide a method for verifying the responses and their relationship to allergic sensitisation. Most allergies show dominant responses to one or a few major allergens. These allergens have been described for the common allergies and have been produced as recombinant allergens. A particular problem for allergens is that many are mixtures of proteins from multi-gene families or are highly polymorphic. Information now exists so the sequence variation can be represented. Purified recombinant allergens produced by standard expression systems stimulate the expected T-cell responses from the peripheral blood of allergic and non-allergics to allergen extracts. Although stimulation with recombinant allergens which are not produced with a natural IgE binding activity can provide a measure of allergenicity, the altered tertiary structure can reduce Th2 responses. The sequence information now available provides the means to use PCR to produce cDNA for the production of recombinant allergens from readily available sources. The production of the highly reactive recombinant Der p 2 allergen of house dust mite from natural sources is described.

Api m 6: a new bee venom allergen

BACKGROUND

Characterization of the primary structure of allergens is a prerequisite for the design of new diagnostic and therapeutic tools for allergic diseases.

OBJECTIVE

The purpose of this study was the identification and characterization of a low-molecular-weight, IgE-binding, bee venom (BV) allergen.

METHODS

BV proteins were separated by using size exclusion chromatography and HPLC. IgE antibody binding to purified proteins was analyzed by means of immunoblotting, and T-cell response was analyzed by means of proliferation assay. Amino acid sequence was determined with 2 approaches, namely Edman degradation and carboxy terminal analysis with mass spectrometry.

RESULTS

Api m 6, which migrated as an 8-kd band in SDS-PAGE, was frequently (42%) recognized by IgE from BV-hypersensitive patients. In addition, PBMCs from BV-hypersensitive patients, as well as from a normal control subject, proliferated in response to this allergen. Api m 6 exists as 4 isoforms of 7190, 7400, 7598, and 7808 d, respectively. Amino acid sequences obtained from HPLC-purified preparations revealed that the isoforms were constituted of a common central core of 67 residues, only differing in the amino- and carboxy-terminal ends. Api m 6 showed no significant sequence homology with known proteins.

CONCLUSIONS

We have identified and sequenced a new BV allergen that elicits a strong IgE and T-cell response in a large number of BV-hypersensitive patients. Api m 6 should be considered in the diagnostic and therapeutic approach of BV immunotherapy on the basis of peptides or recombinant proteins.

The CC-chemokine receptor 5 (CCR5) is a marker of, but not essential for the development of human Th1 cells

The CC-chemokine receptor 5 (CCR5) has recently been described as a surface marker of human T cells producing type 1 (Th1) cytokines. Here we confirm that CCR5 is expressed on human Th1 but not on Th2 T-cell clones. Using intracellular cytokine staining, we show that alloantigen specific CD4+ T-cell lines derived from a CCR5-deficient individual (delta32 allele homozygote) contain high numbers of both interferon gamma (IFN-gamma) and interleukin (IL)-2 producing cells, low numbers of IL-10 producing cells and no IL4 or IL-5 producing cells when stimulated with phorbol ester and ionomycin in vitro. These results were similar to those obtained from alloantigen specific CD4+ T-cell lines derived from CCR5 expressing individuals. An enzyme-linked immunoabsorbent assay (ELISA) confirmed that the Th1 cytokine-positive cells from the CCR5-deficient individual were able to produce equal amounts of cytokines when compared to T-cell lines from CCR5-expressing individuals, These results demonstrate that CCR5-negative T cells display the same capacity of Th1 T-cell differentiation as T cells derived from CCR5-expressing individuals. Thus, CCR5 expression is not essential for differentiation of human Th1 T cells.

Blocking Antibodies Induced by Specific Allergy Vaccination Prevent the Activation of CD4+ T Cells by Inhibiting Serum-IgE-Facilitated Allergen Presentation

Allergen-specific CD4+ T lymphocytes are activated at extremely low allergen concentrations in vivo as a result of serum-facilitated allergen presentation (S-FAP). It is not clear at present if specific allergy vaccination (SAV) has an effect on this mechanism. Here we show that birch allergen-specific serum-IgE facilitates the presentation of Bet v 1, the major birch pollen allergen, to Bet v 1-specific CD4+ T lymphocytes by a factor of >100. This process is CD23 mediated, could be detected in sera from the majority of birch-allergic patients, and was clearly dose dependent. S-FAP of Bet v 1 was inhibited in patients undergoing long-term birch SAV, but not by sera from patients undergoing grass SAV, indicating that birch-specific Abs are involved. This resulted in decreased proliferation and IL-4, IL-5, IL-10, and IFN-γ production of Bet v 1-specific T cells. The inhibition was already noted after 3–9 mo of SAV and could not be solely explained by increased serum levels of birch-specific IgG4. When IgG- and IgA/IgM-containing fractions of long-term SAV sera were used to inhibit S-FAP, only IgG-containing fractions were shown to inhibit S-FAP. These results indicate that blocking IgG Abs induced by SAV inhibits the occurrence of S-FAP at very low allergen concentrations, resulting in significantly higher allergen threshold levels to obtain T cell proliferation and cytokine production and thus allergen-induced late-phase responses.

New Bet v 1 isoforms including a naturally occurring truncated form of the protein derived from Austrian birch pollen

Bet v 1, the major pollen allergen from white birch, displays a considerable degree of heterogeneity. Until now, all molecular and immunological characterization studies of Bet v 1 isoforms have been performed with commercially available pollen of Swedish origin. In regard to clinical studies with Austrian birch pollen allergic individuals, knowledge about the isoform repertoire in Austrian birch pollen was necessary. cDNAs coding for Bet v 1 isoforms from Austrian birch pollen were cloned by PCR amplification and sequenced. Besides the Austrian variants of the Swedish isoforms Bet v 1a (62% of the clones), ALK167 (4%), and Bet v 1d/h, Bet v 1g, and Bet v 11 (24%), three sequences with a significantly lower homology to known isoforms and two Bet v 1a-homologous sequences with a 7 bp insertion coding for a truncated protein were detected. No Austrian variants of the majority of the Swedish isoforms were found. The isoforms coding for truncated proteins were expressed in Escherichia coli and tested by immunoblotting. They bound a polyclonal anti-Bet v 1 antibody but did not recognize birch pollen allergic patients' serum IgE and two Bet v 1-specific monoclonal antibodies. The similarity of the Bet v 1 isoform patterns of Swedish and Austrian birch pollen justifies the use of Bet v 1 derived from Swedish pollen for clinical studies with birch pollen allergic individuals from outside Northern Europe.

The role of allergen-specific T cells in the allergic immune response: relevance to allergy vaccination

Recent research has elucidated many of the immunologic mechanisms that underlie atopic allergies. In particular, it has become clear that the role of CD4+ allergen-specific T cells is crucial for the induction of IgE and eosinophilia, factors that mediate the immediate hypersensitivity reaction and late-phase responses, respectively. Therefore, the reactivity patterns and activation requirements of allergen-specific T cells are important parameters for understanding and manipulating the allergic immune response. This review addresses these issues and discusses their relevance to the further development of allergy vaccines.

CD8+ T cells in atopic disease

In recent years there has been a tremendous expansion in our understanding about CD8(+) T cells. We now know that, as for CD4(+) T cells, they can be divided into subsets (Tc1 and Tc2) according to the cytokines they secrete. These subsets may differ in their capacity to kill and may even, in some cases, provide help for B cell antibody production or be involved in the induction of inflammatory responses. In addition, there is a host of cross-regulatory networks between different CD4(+) and CD8(+) subsets that control the magnitude and duration of immune responses. The observation that some antigens that are normally presented by MHC class II and seen by CD4(+) T cells can be presented by MHC class I and stimulate CD8(+) T cells increases the possibility for such interactions. During the next few years we can expect that our understanding of the biology of CD8(+) T cells and their role in immunity will increase.

Preserved epitope-specific T cell activation by recombinant Bet v 1-MBP fusion proteins

BACKGROUND

Allergen-specific T cells play an important role in the allergic immune response, and are thought to be the principal target in specific immunotherapy.

OBJECTIVE

The aim of the present study was to evaluate if fusion proteins of allergens with bacterial proteins can be used to activate and bias allergen-specific T cells, and to characterize T cell epitopes.

METHODS

The complete gene of Bet v 1, the major birch pollen allergen, was amplified by PCR from birch pollen mRNA, and cloned in pKK223-3. The complete gene or truncated sequences were transferred to pMAL-c and expressed in E. coli as fusion proteins with maltose binding protein (MBP). The complete fusion protein, and the truncated fusion proteins were used for studies with Bet v 1-specific T cells.

RESULTS

Bet v 1-specific T cells reacted similarly with purified and crude Bet v 1-MBP proteins. Therefore, crude preparations were used to study the epitope-specificity of 11 Bet v 1-specific T cell clones. Six distinct T cell epitopes were determined in this way. Interestingly, the T cell epitope of three T cell clones, that did not react with synthetic peptides in a previous study, was identified. In addition, the presence of MBP as a fusion partner to Bet v 1 was shown to influence TH2/TH1 cytokine production in T cell lines, but not in established T cell clones.

CONCLUSION

Using crude preparations of recombinant fusion proteins of Bet v 1 with MBP, multiple T cell epitopes were identified in Bet v 1. As T cell activation is preserved in this system, the generation of recombinant allergens with TH1-inducing proteins as fusion partners might be considered as a T-cell targeted approach for specific immunotherapy.