cDNA cloning and immunological characterization of the rye grass allergen Lol p I

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.

Purification, characterization and molecular cloning of Cha o 1, a major allergen of Chamaecyparis obtusa (Japanese cypress) pollen

Pollen of Chamaecyparis obtusa (Japanese cypress) is one of the causes of allergic pollinosis in Japan. A major allergen of the pollen designated Cha o 1, was purified by two-step ion exchange chromatography. Cha o 1 was separated into four components with molecular masses of 48.5 kDa and 52.0 kDa, each with pIs of 6.77 and 6.82. The 23-residue N-terminal sequence of Cha o 1 was determined and shown to have high identity with that of Cry j 1, a major allergen of Cryptomeria japonica pollen. cDNA coding for Cha o 1 was cloned by hybridization screening using Cry j 1 cDNA as a probe. One of the cDNA clones, pCHA-1 was sequenced and found to code for a putative 21-residue signal peptide and a 354-residue native protein with a derived molecular mass of 38.1 kDa. The deduced amino acid sequence of Cha o 1 showed 79-80% identity with those of Cry j 1. These findings were consistent with observations of a close crossreaction between the two allergens. Homology analyses revealed that Cha o 1 had 46-49% identity with Amb a 1 families and Amb a 2, the major allergens of short ragweed. Cry j 1 has pectate lyase enzyme activity, suggesting that Cha o 1 may have the same enzyme activity as Cry j 1.

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.

A cDNA from pea petals with sequence similarity to pollen allergen, cytokinin-induced and genetic tumour-specific genes: identification of a new family of related sequences

A cDNA isolated from pea petals exhibits extensive similarity to pollen allergen genes, a cytokinin-regulated cDNA from soybean suspension cultures, a partial cDNA preferentially expressed in tobacco genetic tumours, four Arabidopsis expressed sequence tags (ESTs) and fifteen rice ESTs. This diverse family of pollen-allergen-likes genes may have a common ancestor or at least share common functional domains. Possession of a putative signal peptide and a presumed extracellular location is a common aspect of this family of sequences.

Recombinant expression and epitope mapping of grass pollen allergens

We have studied the expression of recombinant forms of Group 1 allergens from rye-grass and Bermuda grass pollens. Recombinant Lol p 1 expressed in bacteria bound serum IgE from allergic patients. Based on analysis of fragments of the Lol p 1 cDNA clone, the major IgE-reactive epitope has been mapped to the C-terminus. However, although SDS-denatured natural Cyn d 1 (from Bermuda grass) bound IgE, the full or partial recombinant proteins expressed in bacteria did not bind IgE. We have since expressed Cyn d 1 in the yeast Pichia pastoris and restored IgE binding. cDNA clones encoding two isoforms of Lol p 5, Lol p 5A and Lol p 5B, have been expressed in bacteria and resulting polypeptides show IgE-binding. Random fragments of these clones have been generated and when expressed as partial recombinant proteins in bacteria, allowed us to identify the major IgE-binding epitopes. The allergenic epitopes were localised towards the C-terminal half of the molecule. Although both isoforms shared similar IgE-reactive epitopes, Lol p 5B did not recognise the Lol p 5A-specific monoclonal antibody A7. At sequence level, there appear to be several amino acid differences between the antigenic epitopes of these two isoallergens. These results aid in the design of diagnostics and in grass pollen immunotherapy.

The effect of sucrose on the quality of ryegrass (Lolium perenne) pollen extracts

We studied the protein-stabilizing properties of sucrose, in the extraction medium, on the composition and stability of ryegrass (Lolium perenne) pollen extracts. The effect of 0.5 M and 1 M sucrose was assessed in the presence and absence of 0.5% phenol, which is commonly used as a disinfectant in industrially prepared allergenic extracts. In the absence of phenol, sucrose improves the stability of extracts during storage, but it has little influence on the extraction process. In the presence of 0.5% phenol, however, both the quality of fresh extracts and the stability are greatly improved by 0.5 M and by 1 M sucrose, as shown by electrophoresis, immunoblotting, and RAST-inhibition experiments. The protection afforded by sucrose against the degrading effect of phenol is particularly evident for the major allergen Lol p 1 and for a set of basic allergens. In this respect, sucrose has been found to be superior to glycerol, on an equimolar basis. One may envisage the use of 0.5 M sucrose in allergenic extracts for intradermal testing and immunotherapy.

Recombinant allergens for diagnosis and therapy of allergic diseases

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cloning, expression and immunological characterization of Ory s 1, the major allergen of rice pollen

We have isolated and characterized a cDNA clone, Ory s 1, encoding a group-1 allergen of rice pollen. The Ory s 1 protein shows significant sequence identity to the major allergen of rye-grass pollen, Lol p 1. RNA gel blot analysis shows that the Ory s 1 gene is expressed in mature anthers, but not in vegetative or other floral tissues tested. Southern blot analysis indicates that this clone represents a member of a small gene family in rice. Western blot analyses of total rice pollen proteins with the group-1 allergen-specific monoclonal 3A2 and IgE antibodies from grass pollen-allergic patients, revealed the presence of cross-reactive antigenic and allergenic epitopes in Ory s 1.

Cloning, sequencing and expression in Escherichia coli of Pha a 1 and four isoforms of Pha a 5, the major allergens of canary grass pollen

BACKGROUND

The pollen of canary grass, which was introduced as a pasture grass from Europe, is a major allergen source in the external environment of southern Australia. This study was performed to characterize the major recombinant allergens of canary grass pollen. It is anticipated that recombinant allergens may be useful in diagnosis and immunotherapy of grass pollen induced allergies.

OBJECTIVE

To clone major canary grass pollen allergens and assess their nucleotide and amino acid sequence homologies with other grass pollen allergens. This sequence information may then be useful in T and B cell epitope mapping studies.

METHODS

A canary grass pollen lambda gt11 cDNA expression library was constructed and screened with sera of grass-pollen-sensitive patients. IgE-reactive clones were isolated, sub-cloned into Escherichia coli, sequenced and, along with the deduced amino acid sequences, compared with other sequences in nucleotide and amino acid databases.

RESULTS

One of the clones encoded the group 1 allergen of canary grass pollen, Pha a 1, with a deduced amino acid sequence identity of 88.8% with Lol p 1, from rye-grass pollen, 88.1% with Hol l 1, from velvet grass pollen and 86.6% with Phl p 1, from timothy grass pollen. The other clones (e.g. clones, 5, 14, 28, 29) encoded polymorphic forms of Pha a 5. These polymorphic forms showed between 60.6-95.5% nucleotide and 40.1-81.7% deduced amino acid sequence identities with each other. Moreover, they shared significant sequence identity with other group 5 allergens from rye-grass, timothy and Kentucky bluegrass pollens.

CONCLUSIONS

Group 1 and four isoforms of group 5 allergens of canary grass pollen have been cloned and upon sequencing demonstrated strong nucleotide and amino acid sequence identities with other group 1 and 5 grass pollen allergens.

Characterization of the isoforms of the group I allergen of Cynodon dactylon

BACKGROUND

The group I allergen of Cynodon dactylon, Cyn d I, was found to consist of four to 10 isoforms.

METHODS

We studied the isoforms with the use of two-dimensional gel electrophoresis. The antigenic difference of the isoforms was evaluated by radioimmunoprecipitation with monoclonal antibodies (MAbs). The acidic isoforms and the basic and neutral isoforms were further isolated by MAb-affinity chromatography for RAST and competitive RAST. In addition, the N-terminal sequence was evaluated by microsequencing.

RESULTS

A total of 11 isoforms were found in Cyn d I in extracts prepared from different sources of Bermuda grass pollen (BGP). They were either acidic (Cyn d I-A, I-B, I-C, I-D, I-E, I-F, I-G, I-H, and I-I), neutral (Cyn d I-X), or basic (Cyn d I-J). Cyn d I-G, with an isoelectric point of approximately 6.4, was constantly present in all the pollen preparations, whereas the content of the basic Cyn d I-J varied from less than 5% to greater than 20%. The molecular weight of the basic and neutral isoforms were slightly lower than those of the acidic isoforms. All isoforms shared a common antigenic determinant(s) recognizable by MAb 4-37, and the basic and neutral isoforms possessed a unique antigenic determinant(s) recognizable by MAb 1-61. RAST showed that both the acidic Cyn d I and the basic and neutral Cyn d I were recognized by human IgE in the pooled sera of persons allergic to BGP. Competitive RAST showed a high crossreactivity between the acidic and the basic and neutral isoforms. A 95% sequence identity also existed between the N-terminal 20 amino acid residues of basic Cyn d I-J and the dominant acidic isoform Cyn d I-G.

CONCLUSIONS

The present study disclosed that basic Cyn d I-J is an important allergen and that the content of this isoform varies in different lots of BGP.

In pursuit of the "holy grail": recombinant allergens and peptides as catalysts for the allergen-specific immunotherapy

This presentation reviews recent progress in knowledge of (i) molecular biology and immunology of allergens and (ii) the methods for the modulation of allergen-specific immune response, with special emphasis on our grass pollen allergens, particularly Pao p IX AL, used as a model. The last few years have seen tremendous progress in molecular characterization of allergens, leading to synthesis of a number of recombinant allergens. Furthermore, studies of the structure-activity relationship of allergens have led to the delineation of the epitopes of these allergens and of widespread cross-reactivities among diverse allergens. In view of the requirement for extensive pre-clinical studies, the application of the recombinant allergens and epitopes in the clinical realm has just begun. Studies in murine systems suggest that these allergens and/or their epitopic peptides downregulate allergen-specific immune responses de novo. The potential and drawbacks of the recombinant allergens and peptides for improving the existing immunotherapeutic approaches and for developing new approaches to specific immunotherapy are discussed.

Recombinant allergen Lol p II: expression, purification and characterization

Pollen from perennial rye grass (Lolium perenne) is a major cause of type I allergies worldwide. It contains complex mixtures of proteins, among which Lol p II is a major allergen. Previously, we have reported the cloning and sequencing of Lol p II and its expression in fusion with the heavy chain of human ferritin as carrier polypeptide (Sidoli et al., 1993, J. biol. Chem. 268, 21819-21825). Here, we describe the expression, purification and characterization of a recombinant Lol p II overproduced as a non-fusion protein in the periplasm of E. coli. The recombinant allergen was expressed in high yields and was easily purified in milligram amounts. It competed with the natural Lol p II for binding to specific IgE, and it induced allergic responses in skin prick tests, indicating to be immunologically analogous to the natural protein. Biochemical analyses indicate that recombinant Lol p II is a highly stable and soluble monomeric molecule which behaves like a small globular protein.

T cell response to grass pollen allergens: correlation with skin test reactivity and serum IgE levels

T cell proliferative responses to rye and Bermuda grass pollen allergens have been studied in a series of 51 atopic and 18 non-atopic subjects. Mean T cell responses were higher in the atopic group than in the non-atopic group (P < 0.001), and there was a strong correlation between the magnitude of reaction in the T cell assay and in the skin test (rye P < 0.01, Bermuda P < 0.05). A similar association was shown between T cell reactivity and serum levels of allergen-specific IgE (rye P < 0.05, Bermuda P < 0.05), but no relationship was found between serum allergen-specific IgG levels and any other parameter studied. T cell reactivity was not found in three cord blood samples tested. Discordance between positivity for T cell responses and skin test reactions in some cases might reflect reactivity by T cell subsets that promote IgG antibody or cell-mediated responses without IgE antibody production. A precise knowledge of T cell recognition of grass pollen allergens will provide exciting new prospects for more effective and safer immunotherapy strategies for allergic diseases including asthma.

Complementary DNA cloning of the major allergen Phl p I from timothy grass (Phleum pratense); recombinant Phl p I inhibits IgE binding to group I allergens from eight different grass species

BACKGROUND

Grass pollens, such as pollen from timothy grass (Phleum pratense), represent a major cause of type I allergy.

OBJECTIVE

In this report we attempted to determine how cross-reactive allergenic components of grass pollens from different species can be represented by a minimum number of recombinant allergens.

METHODS

We isolated and sequenced a timothy grass pollen cDNA coding for the major allergen Phl p I. A recombinant Phl p I-beta-galactosidase fusion protein, which bound to IgE in 87% of patients with grass pollen allergy, was produced in Escherichia coli. Using recombinant Phl p V and Phl p I, we defined representative patients' sera that bound to group I but not to group V allergens, as well as sera with reactivity against group I and group V allergens. IgE immunoblot inhibition studies were done with nitrocellulose-blotted pollen extracts from eight grass species with different geographic distribution.

RESULTS

Preadsorption of patients' sera with recombinant nonfusion Phl p I strongly reduced IgE binding to group I allergens from the eight grasses, showing extensive cross-reactivity between species.

CONCLUSION

A single recombinant group I allergen contains many of the IgE epitopes of group I isoallergens from a number of different grass species.

Mapping of T cell epitopes of the major fraction of rye grass using peripheral blood mononuclear cells from atopics and non-atopics. II. Isoallergen clone 5A of Lolium perenne group I (Lol p I)

Rye grass is the major cause of hay fever which currently affects 20% of the population. Lolium perenne group I (Lol p I) is a glycoprotein of 240 amino acid residues, representing the main allergen of rye grass. We have used peripheral blood mononuclear cells (PBMC) from controls and subjects allergic to rye grass and cultured them with L. perenne extract (LPE) and Lol p I and measured lymphocyte activation using thymidine incorporation. Patients were further studied against the 115 overlapping peptides of the iso-allergen clone 5A of Lol p I to see whether the 4 amino acid residue differences between clone 1A and clone 5A affect the T cell epitope and thus, lymphocyte activation. There are 24 peptide differences between isoallergen clone 1A and clone 5A occurring in pools 4, 13, 16 and 19 each one of which could be an immunodominant epitope. The PBMC from all allergic patients studied showed a strong proliferative response to LPE and Lol p I. Five immunogenic peptide pools, pool 6, 15, 16, 17 and 19 of the isoallergen clone 5A were also identified. Most of these pools are in the C-terminal region of Lol p I. Out of 20 pools tested in vitro 1 pool (pool-17) induced PBMC proliferation in five out of six patients who were not restricted to an HLA class II DR gene product. However, three out of the six subjects responded to various other peptide pools in addition to the immunodominant pool. In spite of the amino acid differences between the two clones, pool 17 still remains the immunodominant T cell epitope. Control subjects showed only weak responses to LPE and no detectable response to either Lol p I or peptide pools. From within the most active pool we have defined two peptides of the isoallergen clone 5A (identical in sequence with clone 1A) which stimulate lymphocytes from rye grass-sensitive patients in vitro. Previous studies with the two continuous sequences (193WGAVWRIDTPDK204 and 195AVWRIDTPDKLT206) tested in vivo by intradermal skin testing have shown typical delayed-type hypersensitivity reactions after 24-48 h in one patient. Comparison of amino acid sequences of Lol p I, Lol p II and Lol p III proteins revealed a significant level of structural similarity among them. Interestingly, 50% of the residues of the second peptide sequence are also present in Lol p II and Lol p III.(ABSTRACT TRUNCATED AT 400 WORDS)

Four recombinant isoforms of Cor a 1, the major allergen of hazel pollen, show different reactivities with allergen-specific T-lymphocyte clones

Purified preparations of allergenic proteins from plants, and in particular from pollens, consist of multiple closely related isoforms. These isoforms are highly similar in their amino acid sequences, yet they display different properties with respect to antibody binding. In this study we report of differential potencies of cross-reacting tree pollen allergens and cloned isoforms of these allergens to activate allergen-specific T-lymphocyte clones (T-cell clones; TCC). Six TCC with specificity for Bet v 1, a representative tree pollen major allergen, were established from peripheral blood of five birch-pollen-allergic donors. All TCC displayed the helper-cell phenotype. Five TCC reacted with distinct epitopes present on natural (n) and on recombinant (r) Bet v 1. One TCC could not be stimulated with r Bet v 1, in spite of strong reactivity with purified natural Bet v 1. The TCC were tested in proliferation assays using purified n Bet v 1, n Cor a 1 (the homologous major allergen of hazel pollen), r Bet v 1, four recombinant isoforms of Cor a 1 and peptides representing corresponding T-cell stimulating regions (isoepitopes) on these proteins. The clones showed different patterns of reactivity in response to stimulation with the five recombinant molecules and the corresponding peptides. Certain exchanges of amino acids within stimulating peptides correlated with a lack of proliferation of the TCC tested. These findings are important with respect to the use of broadly cross-reactive recombinant allergens or allergen-derived peptides for immunotherapy of type I allergy.

Major allergen Phl p Va (timothy grass) bears at least two different IgE-reactive epitopes

It is established that most grass pollen allergens consist of several isoforms of which the function is mainly still unknown. A number of these allergens belonging to group V have been cloned, sequenced, and expressed. Antigenic sites and IgE-reactive epitopes of the major allergen Phl p Va, are unknown. We have identified the complete cDNA sequence of a Phl p Va isoallergen by immunoscreening of a timothy grass pollen cDNA library and mixed oligonucleotide primed amplification of N-terminal cDNA. Additionally, we found an incomplete isoallergenic cDNA clone of the same protein. Immunoreactivity of the fusion proteins with patients' sera and monoclonal antibodies showed that the clones represent group Va allergens. Comparison of deduced amino acid sequences with published sequences of Lol p V and Poa p IX revealed a homology of 81.1% and 86.9%, respectively. With affinity-purified IgE antibodies recognizing the recombinant fusion protein, we can demonstrate the existence of a common group V IgE-reactive epitope. By construction of both an N-terminal and a C-terminal peptide of the complete Phl p Va and cross-inhibition, we identified at least two different IgE epitopes. Eleven patients showed variable IgE immunoreactivities to both IgE-reactive epitopes.

Cytokinin regulation of a soybean pollen allergen gene

Cytokinin treatment of suspension-cultured soybean cells stimulated the accumulation of an mRNA, called cim 1, by a factor of ca. 20 within 4 h. Induction of cim 1 mRNA accumulation occurred at benzyladenine concentrations as low as 10(-8) M. Furthermore, cim 1 mRNA accumulation was stimulated in the absence of cytokinin by staurosporine (an inhibitor of protein kinases) and inhibited in the presence of cytokinin by okadaic acid (an inhibitor of protein phosphatases 1 and 2a), suggesting that cim 1 accumulation in response to cytokinin is dependent on cytokinin-induced dephosphorylation of one or more cellular proteins. The deduced amino acid sequence of the cim 1 protein product, derived from the complete nucleotide sequence of a cim 1 cDNA, was 40% identical to that of a perennial rye grass pollen allergen cDNA (Lol Pl). This sequence also indicated that the cim 1 protein product contains a putative signal peptide followed by predominantly hydrophilic residues, consistent with the hypothesis that it is exported to the apoplast.

IgE and IgG cross-reactivity among Lol p I and Lol p II/III. Identification of the C-termini of Lol p I, II, and III as cross-reactive structures

In this study, the homologous C-termini of Lol p I, Lol p II, and Lol p III were shown to contain cross-reactive B-cell epitopes. This was demonstrated by inhibition studies with purified Lol p I, II, and III and synthetic peptides of their C-termini. It was ruled out that the observed cross-reactivity was caused by cross-contamination of the purified allergens. Both human IgE and IgG bound to the C-terminus of Lol p I. These antibodies were cross-reactive with Lol p II and, more specifically, with its C-terminus. Within a small panel of allergic patients, no cross-reactivity with Lol p III was found. A hyperimmune polyclonal rabbit antiserum against Lol p I also recognized the Lol p I C-terminus. As for human antibodies, cross-reactivity with Lol p II and its C-terminus was demonstrated. Cross-reactivity with Lol p III was demonstrated with C-terminal peptides, but not with native Lol p III. A polyclonal rabbit antiserum against Lol p II bound to the C-terminal peptides of both Lol p II and III. This binding was inhibited with Lol p I, confirming that cross-reactive structures exist not only on the C-termini of Lol p II and Lol p I, but also of Lol p III and Lol p I. The existence of cross-reactivity between Lol p I and Lol p II and III possibly contributes to the frequently observed cosensitization for these allergens in grass-pollen-allergic patients.

Immunological relationships among group I and group V allergens from grass pollen

Specific IgE antibodies have been affinity-purified from recombinant grass pollen allergens, and used to identify isoforms of the two major allergens of rye-grass pollen, Lol p I and Lol p V and cross-reactive allergens in other grasses. Lol p I-specific IgE (affinity-purified from the recombinant protein expressed by clone 13R which encodes amino acids 96-240 of Lol p I) identified four isoforms of the allergen. The same probe recognized cross-reactive epitopes in pollen proteins from 14 out of 16 grasses. The allergens identified by Lol p V-specific IgE (affinity-purified from the recombinant protein expressed by clones 12R or 19R which encode the full Lol p V protein) varied more in their physicochemical characteristics than the Group I isoforms. At least eight isoforms of Lol p V were identified by the Lol p V-specific IgE. The same probe recognized cross-reactive epitopes in pollen protein from 13 out of 16 grasses. Group I proteins were identified in grasses from two sub-families of the Poaceae, while the Group V allergens were only identified in pollen of grasses from one sub-family, the Pooideae.

Epitope analysis of isoforms of the major allergen Phl p V by fingerprinting and microsequencing

The major allergen of timothy grass pollen (Phleum pratense), designated as Phl p V, consists of isoallergenic components of 38 and 32 kDa with pl values of 5.2-7.5 and 4.8-5.9, respectively. The different-sized proteins reveal similarities in IgE reactivity, N-terminal sequence and protein staining. For epitope analysis of these allergens a combination of enzymatic cleavage of electrophoretically separated proteins and immunoblotting techniques with subsequent N-terminal sequencing was performed. After isolation of the components from two-dimensional PAGE gels, proteins were enzymatically cleaved and separated by SDS-PAGE. By endoproteinase Glu-C cleavage six IgE-reactive fragments of each 32 kDa protein and three of each 38 kDa allergen were obtained. Microsequencing of the fragments revealed internal sequences that did not show any similarities between the different-sized allergens. Therefore, we assume only slight structural variations among allergens of similar sizes, whereas the 32 and 38 kDa proteins reveal great differences.

Molecular characterization of Phl p II, a major timothy grass (Phleum pratense) pollen allergen

Grass pollen allergens belong to the most important and widespread elicitors of pollen allergy. Using serum IgE from a grass pollen allergic patient, a complete cDNA encoding a group II allergen was isolated from a timothy grass (Phleum pratense) pollen expression library. The deduced amino acid sequence of the Phl p II allergen shows an average sequence identity of 61% with the protein sequences determined for group II/III allergens from rye grass (Lolium perenne) and a sequence identity of 43% with the C-terminal portion of group I grass pollen allergens from different species. A hydrophobic leader peptide similar to leader peptides found in other major grass pollen allergens heads the deduced amino acid sequence, indicating that group II/III grass pollen allergens belong to a family of secreted proteins. Serum IgE specific for Phl p II, detected the protein exclusively in pollen and not in other plant tissues. The recombinant Phl p II was expressed in Escherichia coli and showed similar IgE-binding capacity as the natural allergen.

Cloning of a cDNA encoding a group-V (group-IX) allergen isoform from rye-grass pollen that demonstrates specific antigenic immunoreactivity

We have isolated and characterized the cDNA clone, 19R, that encodes an isoform of a major rye-grass pollen allergen, Lol p V [previously referred to as Lol p 1b; Singh et al., Proc. Natl. Acad. Sci. USA 88 (1991) 1384-1388; and Lol p IX; Suphioglu et al., Lancet 339 (1992) 569-572]. Clone 19R was isolated from a rye-grass pollen cDNA expression library using grass pollen-specific immunoglobulin E (IgE) antibodies (Ab) from an allergic serum pool. The nucleotide (nt) sequence of clone 19R potentially encodes a 33.8-kDa protein of 339 amino acids (aa). It possesses a leader peptide essentially identical to the previously characterized isoform of Lol p V (Lol p VA). This indicates a mature processed 31.3-kDa protein of 314 aa, correlating well with the size of the polypeptides revealed by Western analysis of pollen proteins using IgE Ab affinity purified from recombinant fusion protein (reFP) encoded by clone 19R as solid matrix. There is no N-glycosylation motif. The protein encoded by clone 19R, designated Lol p VB, has 66.4% identity and 80.4% similarity with Lol p VA. However, a Lol p VA-specific monoclonal Ab, FMC A7, does not recognize reFP encoded by clone 19R, indicating that Lol p VB does not share this epitope. Cross-reactivity studies using affinity purified IgE Ab showed that both isoforms share similar allergenic epitopes. Immunoblot analysis using sera from a population of 30 patients showed that 80% possess IgE Ab that recognize both Lol p V isoforms. Variation occurred in the signal intensities of IgE binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleotide sequence of cDNA encoding the group II allergen of cocksfoot/orchard grass (Dactylis glomerata), Dac g II

Cocksfoot/orchard grass (Dactylis glomerata) anther cDNA clones encoding the group II allergen Dac g II were previously isolated on the basis of immunoreactivity of human, rabbit, and murine antibodies with a 24-kDa protein expressed as a fusion protein with beta-galactosidase. Nucleotide sequencing reveals an open reading frame predicting expression of a 98-amino-acid (11-kDa) polypeptide exhibiting > 90% homology with the group II allergen of Lolium perenne, Lol p II. In vitro translation of different sized clone fragments generated by polymerase chain amplification confirms eukaryotic expression of a 10-12-kDa polypeptide by SDS-PAGE and the position of a translational stop apparently unrecognized during expression of lambda gt11 in E. coli. The unusual characteristics of the prokaryote-expressed fusion proteins may be exerting conformational alterations in Dac g II, as reflected by previous demonstrations of differences in human IgE immunoreactivity. Northern blot analysis using PCR-generated partial and full-length probes suggests that group II allergens may be encoded by a different family or families of temporally expressed genes from those encoding group I major allergens, although a group I gene may have been the progenitor.

T cell epitopes of the major fraction of rye grass Lolium perenne (Lol p I) defined using overlapping peptides in vitro and in vivo. I. Isoallergen clone1A

One hundred and fifteen overlapping synthetic peptides spanning the entire sequence of the iso-allergen clone1A of Lol p I from rye grass Lolium perenne were synthesized by the multi-pin technique. The peptides were overlapping 12mers, offset by two residues and overlapping by 10 residues. Sets of six adjacent overlapping peptides (except pool-1, 15, 20) were pooled and were used in vitro and in vivo to map the T cell epitopes on Lol p I. Six atopics who were skin test and RAST positive to rye grass showed T cell responses to L. perenne extract (LPE) and its major fraction (Lol p I). Five out of six showed T cell responses in vitro to peptide pool-17, while five non-atopics did not respond to any of the peptide pools. By testing the individual peptides of pool-17, we have located the T cell epitope on Lol p I. Interestingly, when we tested pool-17 and its single peptides in vivo by intradermal skin testing we found in one patient a typical DTH after 24-48 h to pool-17 and its peptides (peptides 3 and 4) which exactly matched the in vitro responses. By defining the T cell epitopes in this way a greater understanding of the allergic response to pollen will be obtained, and a more effective and less dangerous vaccine may be possible for treating patients with hay fever.

Zea mI, the maize homolog of the allergen-encoding Lol pI gene of rye grass

Sequence analysis of a pollen-specific cDNA from maize has identified a homolog (Zea mI) of the gene (Lol pI) encoding the major allergen of rye-grass pollen. The protein encoded by the partial cDNA sequence is 59.3% identical and 72.7% similar to the comparable region of the reported amino acid sequence of Lol pIA. Southern analysis indicates that this cDNA represents a member of a small multigene family in maize. Northern analysis shows expression only in pollen, not in vegetative or female floral tissues. The timing of expression is developmentally regulated, occurring at a low level prior to the first pollen mitosis and at a high level after this postmeiotic division. Western analysis detects a protein in maize pollen lysates using polyclonal antiserum and monoclonal antibodies directed against purified Lolium perenne allergen.

Comparison of four grass pollen species concerning their allergens of grass group V by 2D immunoblotting and microsequencing

The identification and characterization of allergenic components is a vital step towards improving diagnosis and therapy. Members of the grass family (Poaceae) reveal a high cross-reactivity among each other caused by the close phylogenetical relationship. In order to investigate the variability between allergenic components, we studied the allergen grass group V, one of the major allergens. Pollen extracts of 4 different tribes (timothy grass (Phleum pratense)--Agrostidae, perennial rye grass (Lolium perenne)--Festuceae, meadow velvet (Holcus lanatus)--Aveneae, and rye (Secale cereale)--Triticeae) of the Festucoideae subfamily were separated by 2D PAGE and investigated by immunoblotting using patients' poolserum and monoclonal antibodies (raised against group V allergens of timothy grass pollen). The antibodies identify different allergens in the four grass species. The components vary from 30-50 kDa and pI 4.8-7.0. The eight NH2-terminal amino acids were determined and indicated high similarities between the different components. These results cast doubt on the suitability of classifying allergens into groups based only on their molecular mass, isoelectric point and N-terminal sequence analysis. It suggests to classify allergens according to their IgE-reactive epitopes.

Purification and immunochemical characterization of recombinant and native ragweed allergen Amb a II

The complete sequence of a cDNA encoding Amb a II and its relationship to the Amb a I family of allergens has recently been described [Rogers et al. (1991) J. Immun. 147, 2547-2552; Griffith et al. (1991a), Int. Archs Allergy appl. Immun. 96, 296-304]. In this study, we present results generated with rabbit antipeptide antisera that recognize Amb a II or Amb a I, but not both. The specificity of two anti-Amb a II antipeptide sera, anti-RAE-50.K and anti-RAE-51.K, was verified on Western blots of recombinant Amb a II and Amb aI.1. These two sera, directed against separate regions of the Amb a II molecule, detected three individual 38-kDa Amb a II isoforms on 2D Western blots of aqueous ragweed pollen extract. These Amb a II isoforms have pI in the 5.5-5.85 range and can be easily distinguished from Amb a I isoforms with pI in the 4.5-5.2 range detected by an anti-Amb a I specific peptide antiserum. The Amb a II isoforms have also been individually purified from pollen, positively identified as Amb a II by amino acid sequencing, and visualized as separate bands on IEF gels. An analysis of Amb a II cDNA sequences generated by PCR led to the prediction of three Amb a II isoforms with pI of 5.74, 5.86 and 5.97 that are very similar to the pI deduced from 2D Western blot analysis. Recombinant Amb aI.1 and Amb a II have been expressed in E. coli, purified in their denatured form, and examined by ELISA for their capacity to bind pooled allergic human IgE. Purified native Amb a and Amb a II from pollen were shown to have very similar IgE-binding properties. In contrast, Amb a II had a markedly reduced IgE-binding capacity as compared to Amb a I.1. These data suggest that recombinant Amb a I.1 and Amb a II, isolated in a denatured form, differ significantly in their IgE-binding properties whereas the native molecules isolated from pollen do not.

Multiple T cell specificities for Bet v I, the major birch pollen allergen, within single individuals. Studies using specific T cell clones and overlapping peptides

Twenty-five T cell clones specific for Bet v I were established from the peripheral blood of two birch pollen-allergic patients. The T cell epitopes of these clones were mapped using dodecapeptides overlapping for 2 amino acids (neighbors share 10 residues) spanning the whole amino acid sequence of the protein (159 amino acids). In total, 7 epitopes could be detected. One donor displayed 6 distinct T cell specificities for the Bet v I molecule in 14 T cell clones; for the other donor, 4 stimulating peptides for 11 clones could be identified. Two T cell epitopes were recognized by both subjects. One of these might represent an immunodominant epitope located at amino acid position 77-92 of the Bet v I molecule, as in 13/25 T cell clones activation could be induced by this amino acid sequence. One T cell clone reacted with purified pollen-derived Bet v I, but neither with any peptide synthesized according to a Bet v I-encoding cDNA nor with the respective recombinant protein. Upon stimulation with allergen, the majority of the clones (21/24) revealed the TH0 or TH2 type of cytokine production (interleukin-4 production), indicating their importance in the pathogenesis of the allergic disease.

Identification of canary grass (Phalaris aquatica) pollen allergens by immunoblotting: IgE and IgG antibody-binding studies

The pollen of canary grass, which was introduced as a pasture grass from Europe, is a major allergen in the external environment of southern Australia. Seventeen allergenic fractions of canary grass pollen, ranging in mol. mass from 14 to 100 kDa, have been identified by immunoblotting, using IgE antibodies from sera of 24/30 grass-pollen-allergic subjects. The highest frequency of IgE binding (77%) was to a major 34-kDa fraction (tentatively designated Pha a I). This protein has been partially purified and identified as a group I allergen by immunodepletion experiments, with partially purified Lol p I (from rye-grass pollen), atopic serum, and Lol p I-specific MAb. In addition, microsequencing of the N-terminus of Pha a I showed an amino acid sequence identical to Lol p I. In a separate study, IgE binding to Western blots of Pha a I, Lol p I, and Cyn d I was investigated in 24 sera and found to occur in 19/24, 18/24, and 9/24, respectively. IgE binding to all three major allergens, and to both Pha a I and Lol p I, occurred in 8/24 sera. Our findings suggest that while the N-terminal sequence of Pha a I is identical to Lol p I, there may be specific allergenic epitopes exclusive to this allergen that are important for allergenicity in southern Australia.