An immunogenetic analysis of T-cell reactive regions on the major allergen from the house dust mite, Der p I, with recombinant truncated fragments

A hypoallergenic peptide mix containing T cell epitopes of the clinically relevant house dust mite allergens

Background

In the house dust mite (HDM) Dermatophagoides pteronyssinus, Der p 1, 2, 5, 7, 21, and 23 have been identified as the most important allergens. The aim of this study was to define hypoallergenic peptides derived from the sequences of the six allergens and to use the peptides and the complete allergens to study antibody, T cell, and cytokine responses in sensitized and nonsensitized subjects.

Methods

IgE reactivity of HDM‐allergic and non‐HDM‐sensitized individuals to 15 HDM allergens was established using ImmunoCAP ISAC technology. Thirty‐three peptides covering the sequences of the six HDM allergens were synthesized. Allergens and peptides were tested for IgE and IgG reactivity by ELISA and ImmunoCAP, respectively. Allergenic activity was determined by basophil activation. CD4+ T cell and cytokine responses were determined in PBMC cultures by CFSE dilution and Luminex technology, respectively.

Results

House dust mite allergics showed IgE reactivity only to complete allergens, whereas 31 of the 33 peptides lacked relevant IgE reactivity and allergenic activity. IgG antibodies of HDM‐allergic and nonsensitized subjects were directed against peptide epitopes and higher allergen‐specific IgG levels were found in HDM allergics. PBMC from HDM‐allergics produced higher levels of IL‐5 whereas non‐HDM‐sensitized individuals mounted higher levels of IFN‐gamma, IL‐17, pro‐inflammatory cytokines, and IL‐10.

Conclusion

IgG antibodies in HDM‐allergic patients recognize peptide epitopes which are different from the epitopes recognized by IgE. This may explain why naturally occurring allergen‐specific IgG antibodies do not protect against IgE‐mediated allergic inflammation. A mix of hypoallergenic peptides containing T cell epitopes of the most important HDM allergens was identified.

Immunoproteomic analysis of house dust mite antigens reveals distinct classes of dominant T cell antigens according to function and serological reactivity

BACKGROUND

House dust mite (HDM) allergens are a common cause of allergy and allergic asthma. A comprehensive analysis of proteins targeted by T cells, which are implicated in the development and regulation of allergic disease independent of their antibody reactivity, is still lacking.

OBJECTIVE

To comprehensively analyse the HDM-derived protein targets of T cell responses in HDM-allergic individuals, and investigate their correlation with IgE/IgG responses and protein function.

METHODS

Proteomic analysis (liquid chromatography-tandem mass spectrometry) of HDM extracts identified 90 distinct protein clusters, corresponding to 29 known allergens and 61 novel proteins. Peripheral blood mononuclear cells (PBMC) from 20 HDM-allergic individuals were stimulated with HDM extracts and assayed with a set of ~2500 peptides derived from these 90 protein clusters and predicted to bind the most common HLA class II types. 2D immunoblots were made in parallel to elucidate IgE and IgG reactivity, and putative function analyses were performed in silico according to Gene Ontology annotations.

RESULTS

Analysis of T cell reactivity revealed a large number of T cell epitopes. Overall response magnitude and frequency was comparable for known and novel proteins, with 15 antigens (nine of which were novel) dominating the total T cell response. Most of the known allergens that were dominant at the T cell level were also IgE reactive, as expected, while few novel dominant T cell antigens were IgE reactive. Among known allergens, hydrolase activity and detectable IgE/IgG reactivity are strongly correlated, while no protein function correlates with immunogenicity of novel proteins. A total of 106 epitopes accounted for half of the total T cell response, underlining the heterogeneity of T cell responses to HDM allergens.

CONCLUSIONS AND CLINICAL RELEVANCE

Herein, we define the T cell targets for both known allergens and novel proteins, which may inform future diagnostics and immunotherapeutics for allergy to HDM.

Definition of a pool of epitopes that recapitulates the T cell reactivity against major house dust mite allergens

BACKGROUND

Allergens from house dust mites (HDM) are a common cause of asthma. Der p and Der f from Dermatophagoides sp. are strong immunogens in humans. Allergen extracts are used to study T helper (Th2) cell responses to HDM, which are implicated in the development and regulation of allergic disease.

OBJECTIVE

To define an epitope mixture that recapitulates, and might substitute for, HDM extract in terms of detecting and characterizing Th2 cell responses.

METHODS

Peripheral blood mononuclear cells (PBMC) from 52 HDM allergic and 10 non-allergic individuals were stimulated with HDM extracts and assayed with a set of 178 peptides spanning mite allergens group Der p 1, 2, 23 and Der f group 1 and 2 allergens. A pool of the most dominant T cell epitopes identified in the present study and from published literature was assembled and tested for ex vivo T cell responses. Correlation with HDM-specific IgE titres was examined.

RESULTS

Patterns of T cell reactivity to Der p and Der f - derived peptides revealed a large number of epitopes. Clear patterns of immunodominance were apparent, with HDM allergen group 1 and 2 dominant over group 23. Furthermore, within a given antigen, 6-11 epitopes accounted for the vast majority of responses. Based on these results and published data, a comprehensive dust mite pool (DMP) of epitopes was designed and found to allow detection of ex vivo T cell responses. DMP ex vivo reactivity correlated with HDM-specific IgE titres and was similar to that detected with commonly used HDM extracts. Ex vivo DMP stimulation was associated with a predominant Th2 response in allergic donors, and minor reactivity of T cells producing IFNγ, IL17 and IL10.

CONCLUSIONS & CLINICAL RELEVANCE

A detailed map of Der p and Der f antigens defined a pool of epitopes that can be used to detect ex vivo HDM responses.

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.

Proteomic analysis in the identification of allergenic molecules

Conventional and innovative strategies can be exploited to identify and characterize new allergenic proteins. With the aim of obtaining suggestions for future improvements, this article describes our attempt to understand and describe some of the advantages and pitfalls of the methodologies and procedures often used in this field. The analysis includes the protein extract preparation, starting from the allergenic source, the separation of the proteins contained in a mixture and the detection, identification and characterization of IgE-binding molecules. Classic and emerging proteomic technologies, including mass spectrometry-based methodologies, Edman degradation procedure, microarray-based techniques and bioinformatics search strategies, have been explored. A comparative analysis of biochemistry-based proteomics and molecular biology strategies has also been given.

Epitope-specific T-cell responses and allergic phenotypes: implications for T-cell peptide therapy

In the 1990s, elucidation of the primary amino acid sequence of several major allergens using molecular cloning techniques opened the door to T-cell epitope mapping studies. Such analyses underscored the complexity of the allergen-specific T-cell repertoire and the challenges to using allergen-derived peptides to identify epitope-specific differences associated with allergic and nonallergic responses. This review highlights important factors that may influence the nature of epitope-specific T-cell responses observed in vitro. These include the properties of the allergen, genetics of the host and selection of patients with defined allergic phenotypes based on serum antibody profiles and skin test reactivity. By taking these factors into account, T-cell epitope-specific differences associated with distinct allergic phenotypes can be identified. Observations at the T-cell epitope level undermine the Th1/Th2 paradigm as a model for the development of allergic versus nonallergic responses. Instead, they support the mounting data that point to a network of interactions between T helper cells and regulatory T cells, which controls the allergic response. The ability of peptides that localize to polypeptide chain 2 of the major cat allergen, Fel d 1, to preferentially induce interleukin-10 and interferon-gamma is discussed. Mechanisms whereby specific allergen-derived peptides may modify the T-cell repertoire and influence the immune outcome are also outlined. Further investigation of allergen-derived T-cell epitopes is warranted in order to optimize the design of peptide vaccines for the treatment of allergic disease.

T-cell epitopes of aeroallergens

OBJECTIVE

To describe the current knowledge of the T-cell epitopes of common aeroallergens, how they were discovered, and implications for future therapy.

DATA SOURCES

PubMed search of English-language articles without date limits pertaining to T-cell epitopes of aeroallergens included on a standard skin test panel.

STUDY SELECTION

A total of 127 articles were screened based on the results of the PubMed search and cross-indexed as needed. The highest quality and most clinically relevant articles were included for discussion.

RESULTS

Of the 47 allergen extracts included on the standard skin test panel at our instittition, T-cell epitopes have been described for 13. Immunodominant epitopes have been used for peptide immunotherapy trials.

CONCLUSIONS

T-cell epitopes have been characterized for a minority of common aeroallergens. However, knowledge is rapidly expanding and can lay the groundwork for therapies that specifically target T cells.

Anti-lymphocyte function associated antigen-1 inhibits T-helper 2 function of human allergen-specific CD4+ T cells

BACKGROUND

Blockade of lymphocyte function associated antigen-1 (LFA-1) is proving successful in the management of psoriasis and other inflammatory skin conditions including atopic dermatitis (AD), but the dependence of allergen-specific CD4+ T-cell function on LFA-1 has not been studied extensively.

OBJECTIVES

We sought to investigate the potential ability of LFA-1 inhibition to influence keratinocyte presentation of allergen to specific T-helper (Th) 2 cell clones.

METHODS

Using human leucocyte antigen class II tetrameric complexes, we generated Der p 1-specific DRB1*1501-restricted CD4+ T-cell lines (n=5) and clones (n=4) from the peripheral blood of five adults with AD.

RESULTS

Using doses of anti-LFA-1 present in vivo, we observed significant inhibition (P<0.05) of allergen-specific CD4+ T-cell production of interleukin-4 with such inhibition occurring during presentation of allergen by keratinocytes.

CONCLUSIONS

These data show that at doses present in vivo, LFA-1 blockade inhibits keratinocyte presentation to allergen-specific Th2 cells, suggesting one mechanism through which anti-LFA-1 may be beneficial therapeutically.

DNA vaccines and allergic diseases

1. Allergic diseases are characterized by inappropriate immune responses to common environmental antigens. The prevalence of these diseases has been increasing worldwide for reasons that are not exactly clear. 2. Current treatment is largely symptomatic. Because the initial observation that simple plasmid DNA injections resulted in in vivo protein expression and induction of adaptive immune responses to the encoded antigen, the potential of modifying the allergic immune responses by DNA vaccination so as to treat and prevent these diseases has been explored extensively. 3. In the present paper we review preclinical studies using animal models of allergic diseases, with an emphasis on DNA vaccine design, for house dust mite allergens-related allergic asthma.

T-cell responses to allergens

The allergic response in human beings is engineered by CD4(+) T lymphocytes, which secrete T(H)2 cytokines in response to activation by allergen-derived peptides. Although T(H)2 cells have been well characterized, defining the properties of allergen-specific T cells has proved challenging in human beings because of their low frequency within the T-cell repertoire. However, recent studies have provided insight into the molecular signature of long-lived human memory T(H)2 cells, which are allergen-specific. T-cell responses directed against allergens develop in early life and are heavily influenced by the type and dose of allergen, and possibly coexposure to microbial products. These responses are susceptible to suppression by regulatory T cells. This article highlights recent advances in the characterization of allergen-specific memory T(H)2 cells and discusses the heterogeneous nature of regulatory T cells and possible mechanisms of action. The relevance of T-cell epitope mapping studies to understanding the unique nature of T-cell responses to different allergens, as well as to peptide vaccine development, is reviewed. Experimental techniques and approaches for analyzing allergen-specific T cells and identifying novel T-cell epitopes are described that may lead to new T-cell-based therapies.

[Proliferative response of peripheral blood mononuclear cells to the recombinant allergen BtM of the Blomia tropicalis housedust mite]

Allergic diseases are triggered when individuals genetically predisposed to developing an allergy (atopy) are exposed to sensitizing allergens. These allergens are captured and processed by antigen-presenting cells (APC) which presents them to T lymphocytes. Some of these allergens have a significant influence on the development of this type of disease and cause most of the symptoms in allergic individuals around the world. They are found in the feces of house dust mites, which have diverse and varied origin in several species, for example the Blomia tropicalis (Bt) mite. In Cartagena (Colombia), this highly prevalent mite has been a central object of study by the Institute of Immunological Research of the University of Cartagena, where several of its allergens have been cloned, sequenced and expressed as recombinant allergens. Moreover, their capacity to bind to IgE and the frequency of this process has been studied. The aim of the present study was to analyze the lymphoproliferative response of peripheral blood mononuclear cells (PBMC) in healthy and allergic individuals to one of the recombinant allergens of B. tropicalis, BtM. This response was studied in PBMC from six patients with allergy to Bt (positive cutaneous test to Bt extract), using a cellular proliferation technique, with incorporation of 3H thymidine at days 3 and 6 days of culture, and at three different concentrations of BtM. Notable among the results was the high proliferation produced by cells from patient JF018 at 3 days of stimulus (41.7 IE), with the lowest concentration of protein (100 microg/mL). Moreover, in all the experiments this concentration was the cause of most of the cell proliferation. In addition, some response to control LAC012 against glutathione-S-transferase (GST) was induced. In conclusion, the results of the present study demonstrate that the recombinant allergen BtM is able to induce a cellular response in the PBMC of patients allergic to Bt. Moreover, it is able to induce a response similar to that produced by natural allergens, because its pattern of response is similar to that shown by cells stimulated with Bt extract. These results also show that a process of anergy can be produced in cells when excess antigen is present. In some individuals (both allergic and nonallergic), GST is able to cause a proliferative response, indicating its sensitizing potential in these individuals.

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.

Chitosan nanoparticles containing plasmid DNA encoding house dust mite allergen, Der p 1 for oral vaccination in mice

Our previous studies indicated that intramuscular (i.m.) immunisation with full length Der p 1 cDNA induced significant humoral response to the left domain (approximately corresponding to amino acids 1-116) but not to the right domain (approximately corresponding to amino acids 117-222) of Der p 1 allergen. This study explored the use of chitosan-DNA nanoparticles for oral immunisation to induce immune responses specific to both the left and right domains of Der p 1. DNA constructs pDer p 1 (1-222) and pDer p 1 (114-222) were complexed with chitosan and delivered orally followed by an i.m. injection of pDer p 1 (1-222) 13 weeks later. Such approach has successfully primed Th1-skewed immune responses against both domains of Der p 1. This strategy could be further optimised for more efficacious gene vaccination for full length Der p 1.

Expression and immunogenicity of the major house dust mite allergen Der p 1 following DNA immunization

The mite protein Der p 1 is a major trigger of allergy and atopic asthma world-wide, and thus, a good vaccine candidate for allergy prevention. Since it is a cysteine protease, the catalytic effects of Der p 1 vaccination may be unpredictable. One approach to reduce this risk is to vaccinate with DNA encoding enzymatically inactive forms of Der p 1. Here we show that Der p 1 DNA without its native pre-pro sequences potently induced Der p 1-specific antibodies, as long as its pre-sequence was substituted by another leader sequence. Without any pre-pro sequence, the same DNA fragment was well expressed but failed to induce significant level of anti-Der p 1 antibodies, without further boosting by protein.

Allergen-specific CD8(+) T cells and atopic disease

Considerable evidence suggests that IL-10 may have a role in the manifestation of atopic disease. We sought to test the hypothesis that at the single cell level, allergen-specific T cells have diminished IL-10 production capacity in severely affected atopics compared with asymptomatic atopics. We defined three A*0201-restricted Der p 1 CD8(+) T cell epitopes. Using human leukocyte antigen-A*0201-peptide (HLA-A*0201-peptide) tetrameric complexes and enzyme-linked immunospot assays to analyze peripheral blood mononuclear cells from A*0201-positive severely symptomatic atopics, asymptomatic atopics, and nonatopic controls, we observed a significant association between the frequency of the Der p 1-specific CD8(+) T cells and disease activity. The specific T cells expressed an antigen-experienced cell surface phenotype, and 45.7% were positive for cutaneous lymphocyte-associated antigen. The specific T cells were able to produce IFN-gamma efficiently, but their IL-10 production was significantly reduced in severely affected atopics. In contrast, viral-specific CD8(+) T cells were able to produce equivalent amounts of IL-10 in the severely affected atopics compared with asymptomatic atopics and nonatopics. Through defining the first human atopic allergen HLA class I epitopes, we have provided a possible cellular mechanism to link the previous association of low IL-10 levels and severe atopic disease. These data are consistent with a role for CD8(+) T cells in atopic disease pathogenesis and may provide a basis for future T cell immunotherapy strategies.

What establishes a protein as an allergen?

There is little known about the factors that determine the allergenicity of food proteins. Apparently, the ability of a food protein to induce an allergic response requires its presence in substantial amounts in the food supply, its durability during food processing, and its resistance to digestion in the gastrointestinal tract. In addition to the mode and degree of exposure, structural characteristics appear to play an important role for the capacity of a protein to modulate the immune response towards allergic reactions. Until now, however, there has been no indication for common structural characteristics of linear T cell or linear IgE (B cell) epitopes and the knowledge of structural characteristics of conformational IgE binding sites is very limited. Experimental data point only to certain surface areas of allergenic proteins which are important for IgE binding. Therefore, it is not possible to suggest any structural motif or conformational sequence pattern common to all allergenic proteins. Furthermore, glycosylation appears not to be a common critical determinant of allergenicity since food allergens comprise both glycoproteins and nonglycosylated proteins. Based on the few published three-dimensional structures of allergenic proteins including food proteins, one unifying feature of allergens appears to be their spherical shape. The three-dimensional structures of many more allergens have to be determined, however, to allow for a better understanding of the molecular basis of allergenicity. Most recently, new ideas have been introduced as to why certain biochemical or biologic functions such as enzymatic activities may predispose a protein to become an allergen. Proteolytically active allergens have been demonstrated to irritate the human mucosal surface, to enhance their own transmucosal uptake, and to augment IgE production. Therefore, the functional activity of some allergens may play a role among other factors in the process of sensitization and allergic responses.

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.

Induction of allergic reactions in guinea pigs with purified house dust mite allergens

To establish a guinea pig model for house dust mite allergy with purified mite allergens, we studied the immune response to two major mite allergens, native Der f 1 (nDer f 1) and recombinant Der f 2 (rDer f 2) and crude mite extract in Hartley guinea pigs. Animals were immunized with either mite extract, nDer f 1 or rDer f 2, four times at 2- to 3-week intervals. Then the guinea pigs were examined as to the status of sensitization to the sensitizing antigen. Intradermal injection of mite antigens to mite extract-, nDer f 1-, and rDer f 2-sensitized animals induced both immediate and late-phase cutaneous reactions. Allergic airway disease was also provoked by the intranasal instillation of rDer f 2 or mite extract. Anti-nDer f 1 and -rDer f 2 IgE as well as anti-mite extract IgE were produced in the sensitized guinea pigs and IgE titer for three mite antigens were comparable. We concluded that immunization of Hartley guinea pigs with nDer f 1 and rDer f 2 achieved sensitization to mite allergens, which was comparable to that obtained by the immunization with mite extract. A mite-allergic model suitable for immunological and pharmacological studies was established from rDer f 2-sensitized guinea pigs.

Hyposensitization to allergic reaction in rDer f 2-sensitized mice by the intranasal administration of a mutant of rDer f 2, C8/119S

C8/119S is a mutant of recombinant Der f 2 (rDer f 2), and lacks a disulphide bond possessed by wild-type rDer f 2. In humans and mice, C8/119S has a very weak IgE-binding capacity compared with the wild-type, but possesses a T cell reactivity comparable to that of the wild-type. C8/119S may thus be a safe immunotherapeutic agent for house dust mite allergy. The aim of the present study was to evaluate whether the intranasal administration of C8/119S could suppress an immediate allergic reaction in mice sensitized with wild-type rDer f 2, possessing an allergic activity comparable to native counterparts purified from mite extract. Seven-week-old male A/J mice were immunized with wild-type rDer f 2 four times, and then intranasally administered 0.2-2 microg of wild-type, 0.2-20 microg of C8/119S, or PBS alone, three times a week for 4 weeks. Seven days after the last administration, the mice were examined for an immediate allergic reaction. The animals administered 2 microg of C8/119S (C2.0 group) showed significantly reduced immediate bronchoconstriction provoked by the i.v. injection of 1 and 10 microg of wild-type rDer f 2, compared with the PBS-treated mice. Similar results were obtained when we examined mice 10 weeks after the last administration. The reactions in the other groups given wild-type or C8/119S also tended to decrease in severity in comparison with the animals of the PBS group. The allergic phenotypes of the T cells, B cells, and basophils in the C2.0 group were shifted to that of naive mice without immunization. We conclude that C8/119S has hyposensitizing activities in mice sensitized with wild-type rDer f 2. C8/119S may be useful for immunotherapy of house dust mite allergy.

T Cell Epitopes in Japanese Cedar (Cryptomeria japonica) Pollen Allergens: Choice of Major T Cell Epitopes in Cry j 1 and Cry j 2 Toward Design of the Peptide-Based Immunotherapeutics for the Management of Japanese Cedar Pollinosis

Japanese cedar pollinosis is caused by exposure to Japanese cedar (Cryptomeria japonica) pollen, of which two components, Cry j 1 and Cry j 2, are believed to be the major allergens. T cell lines specific to either Cry j 1 or rCry j 2 were reactive to various portions of each panel of overlapping peptides derived from Cry j 1 or Cry j 2. Two peptides, p211–225 and p108–120, from among six major T cell epitopes identified in Cry j 1 sequence, and three peptides, p182–200, p344–355, and p66–80, from among five in Cry j 2, were chosen to design an artificial polypeptide (named Cry-consensus) based on a difference among the types of the restriction molecules capable of presenting these peptides. After construction of a DNA encoding these peptides in order, Cry-consensus was expressed in Escherichia coli. Five of six T cell epitopes, except for Cry j 2 p344–355, in Cry-consensus were recognized by the T cell clones specific to each peptide. PBMC from allergic patients induced higher proliferation under stimulation from Cry-consensus than individual peptides. Eighty-eight percent of the PBMC (15 of 17) showed proliferation under the Cry-consensus stimulation. Thus, several major T cell epitopes from Cry j 1 and Cry j 2 can be chosen in the design of peptide-based immunotherapeutics for the management of Japanese cedar pollinosis in subjects having various types of HLA class II molecules.

Analysis of T-cell reactive regions and HLA-DR4 binding motifs on the latex allergen Hev b 1 (rubber elongation factor)

BACKGROUND

The rubber elongation factor in Hevea rubber (Hev b 1) is one of the important latex-allergenic proteins inducing the production of specific IgE antibodies in latex-exposed subjects. In addition, Hev b 1 induces lymphocyte proliferation responses. A study about detailed T-cell epitope analysis of major latex allergens has not been published yet.

OBJECTIVE

The aim of this study was to define the T-cell reactive regions on the latex allergen Hev b 1.

METHODS

Nine overlapping peptides with 19 or 17 amino acid lengths representing the complete sequence of Hev b 1 were used for T-cell epitope mapping. Peripheral blood mononuclear cells (PBMCs) of latex-sensitized patients and healthy subjects were isolated and stimulated with the synthetic peptides to determine the specific proliferation response. The examined patients were sensitized to latex by occupational exposure (n=14) and suffered from rhinitis, conjunctivitis, contact urticaria and/or asthma. Two control groups of non-sensitized subjects were studied, one occupationally exposed to latex (n=4), the other one not exposed to latex (n=4).

RESULTS

Positive proliferation response induced by one or more peptides was detected in 10 of the latex-sensitized patients and in two of the latex-exposed non-sensitized subjects. Each patient exhibited an individual epitope reactivity pattern. The whole protein was found to be immunogenic, but the intensity of lymphocyte responses induced by the peptides was different. The majority of the patients' PBMCs (more than 66%) responded to the peptides 31-49 and 91-109. Using the peptide selection of Stille's algorithms, three epitopes were predicted covering region 38-74 and two others covering region 82-104; the two peptides 31-49 and 91-109 are part of these regions. A strong HLA-DR4Dw4 (DRB1*0401)-binding motif according to published DR4w4 binding motifs was predicted in the region of 102-110 including peptide 91-109 to which the majority of tested HLA-DR4-positive patients responded.

CONCLUSIONS

Our data indicate that the whole 14 kDa protein Hev b 1 is immunogenic having regions that demonstrate individual and varying PBMC stimulation. Experimental data of T-cell reactive regions based on PBMC-stimulation complement the information on T-cell epitope prediction. In addition, the Hev b 1 molecule contains a HLA-DR4Dw4 (DRB1*0401)-binding motif.

Identification of T-cell epitope sequences on an important mite antigen

BACKGROUND

T-cell epitopes on Der 1 and Der 2 groups, the major mite allergens, have been intensively analysed, while those on the other important allergens remain to be elucidated. We have cloned four cDNAs coding for important mite allergens on the basis of frequency and capacity of IgE binding. Stimulatory action of glutathione S-transferase-fused Mag1 on lymphocytes from mite-allergic patients was relatively high among them.

OBJECTIVE

To identify T-cell epitopes on Mag1, we studied the stimulating activity of truncated Mag1 proteins and synthetic peptides on proliferative response of lymphocytes from mite antigen-immunized mice and mite-sensitive patients.

METHODS

Truncated Mag1 proteins were expressed as a fusion protein with beta-galactosidase in Escherichia coli pop2136 carrying a variety of deleted Mag1 inserts. Murine T-cell epitope regions were estimated by the truncated antigen-induced lymphocyte proliferation assay. Overlapping peptides covering the whole sequence of the presumed T-cell epitope regions were synthesized to identify the epitope core sequences using murine and human Mag1-specific T-cell lines.

RESULTS

Amino acid range 56-70 on Mag1 molecule showed remarkable stimulatory action on murine T cells, while amino acid ranges 51-65 and 86-100 had potent stimulatory activity on human T cells.

CONCLUSIONS

These results suggest that Mag1 is a valuable antigen suitable for studies on T-cell responses and T-cell epitopes in mice and humans.

T cell receptor genetics, autoimmunity and asthma

Images