Pru p 3, a marker allergen for lipid transfer protein sensitization also in Central Europe

In the Mediterranean area, lipid transfer proteins (LTPs) are important causes of plant‐food allergies often associated with severe allergic reactions. There, peach LTP (Pru p 3) seems to be the primary sensitizer, whereas in Central Europe, little is known about the importance of LTP sensitization. In this region, allergen extract‐based diagnosis is often complicated by co‐sensitization to Bet v 1, the major birch pollen allergen, its cross‐reactive food allergens, and profilins. We investigated the role of LTP sensitization in Central European patients displaying strong allergic reactions to plant‐derived food. Analysis of IgE reactivity revealed that ten of thirteen patients were sensitized to Pru p 3, nine to Bet v 1, and two to profilin. Our results showed that LTP sensitization represents a risk factor for severe allergic symptoms in Central Europe. Furthermore, the strong IgE reactivity detected in immunoblots of plant‐food extracts indicated that Pru p 3 can be used as a marker allergen for LTP sensitization also in Central European patients.

Infant milk formulas differ regarding their allergenic activity and induction of T-cell and cytokine responses

Background

Several hydrolyzed cow's milk (CM) formulas are available for avoidance of allergic reactions in CM‐allergic children and for prevention of allergy development in high‐risk infants. Our aim was to compare CM formulas regarding the presence of immunoreactive CM components, IgE reactivity, allergenic activity, ability to induce T‐cell proliferation, and cytokine secretion.

Methods

A blinded analysis of eight CM formulas, one nonhydrolyzed, two partially hydrolyzed (PH), four extensively hydrolyzed (EH), and one amino acid formula, using biochemical techniques and specific antibody probes was conducted. IgE reactivity and allergenic activity of the formulas were tested with sera from CM‐allergic patients (n = 26) in RAST‐based assays and with rat basophils transfected with the human FcεRI, respectively. The induction of T‐cell proliferation and the secretion of cytokines in Peripheral blood mononuclear cell (PBMC) culture from CM allergic patients and nonallergic individuals were assessed.

Results

Immune‐reactive α‐lactalbumin and β‐lactoglobulin were found in the two PH formulas and casein components in one of the EH formulas. One PH formula and the EH formula containing casein components showed remaining IgE reactivity, whereas the other hydrolyzed formulas lacked IgE reactivity. Only two EH formulas and the amino acid formula did not induce T‐cell proliferation and proinflammatory cytokine release. The remaining formulas varied regarding the induction of Th2, Th1, and proinflammatory cytokines.

Conclusion

Our results show that certain CM formulas without allergenic and low proinflammatory properties can be identified and they may also explain different outcomes obtained in clinical studies using CM formulas.

Hypoallergenic derivatives of Fel d 1 obtained by rational reassembly for allergy vaccination and tolerance induction

BACKGROUND AND OBJECTIVE

The major cat allergen Fel d 1 represents one of the most important respiratory allergens. Aim of this study was to engineer recombinant Fel d 1 derivatives with reduced IgE reactivity and preserved T cell epitopes for vaccination and tolerance induction.

METHODS

Seven recombinant mosaic proteins were generated by reassembly of non-IgE-reactive peptides of Fel d 1 which contained the sequence elements for induction of allergen-specific blocking IgG antibodies and T cell epitopes. Mosaic proteins were expressed in Escherichia coli using codon-optimized synthetic genes and compared with Fel d 1 regarding structural fold by circular dichroism, IgE-binding capacity, activation of allergic patients' basophils and ability to induce allergen-specific blocking IgG antibodies upon immunization.

RESULTS

Although each of the mosaic proteins had lost the alpha-helical fold typical for Fel d 1, a strong reduction in IgE reactivity as well as allergenic activity in basophil activation assays was only obtained for three constructs, two reassembled fragments (Fel d 1 MB, Fel d 1 MC) and a fusion of the latter two (Fel d 1 MF) in which the cysteines of Fel d 1 MC were replaced by serines. Immunization of rabbits with Fel d 1 MB, MC and MF induced high levels of IgG antibodies that inhibited IgE reactivity of cat-allergic patients to Fel d 1 in a comparable manner as IgG induced with the wild-type allergen.

CONCLUSIONS

We report the development of hypoallergenic reassembled Fel d 1 proteins suitable for vaccination and tolerance induction in cat-allergic patients.

Carrier-bound Alt a 1 peptides without allergenic activity for vaccination against Alternaria alternata allergy

BACKGROUND

The mould Alternaria alternata is a major elicitor of allergic asthma. Diagnosis and specific immunotherapy (SIT) of Alternaria allergy are often limited by the insufficient quality of natural mould extracts.

OBJECTIVE

To investigate whether recombinant Alt a 1 can be used for reliable diagnosis of Alternaria alternata allergy and to develop a safe, non-allergenic vaccine for SIT of Alternaria allergy.

METHODS

The qualitative sensitization profile of 80 Alternaria-allergic patients from Austria and Italy was investigated using an allergen micro-array and the amount of Alternaria-specific IgE directed to rAlt a 1 was quantified by ImmunoCAP measurements. Peptides spanning regions of predicted high surface accessibility of Alt a 1 were synthesized and tested for IgE reactivity and allergenic activity, using sera and basophils from allergic patients. Carrier-bound peptides were studied for their ability to induce IgG antibodies in rabbits which recognize Alt a 1 and inhibit allergic patients' IgE reactivity to Alt a 1.

RESULTS

rAlt a 1 allowed diagnosis of Alternaria allergy in all tested patients, bound the vast majority (i.e. >95%) of Alternaria-specific IgE and elicited basophil activation already at a concentration of 0.1 ng/mL. Four non-allergenic peptides were synthesized which, after coupling to the carrier protein keyhole limpet hemocyanin, induced Alt a 1-specific IgG and inhibited allergic patients' IgE binding to Alt a 1.

CONCLUSIONS AND CLINICAL RELEVANCE

rAlt a 1 is a highly allergenic molecule allowing sensitive diagnosis of Alternaria allergy. Carrier-bound non-allergenic Alt a 1 peptides are candidates for safe SIT of Alternaria allergy.

Patients suffering from non-IgE-mediated cow's milk protein intolerance cannot be diagnosed based on IgG subclass or IgA responses to milk allergens

BACKGROUND

Cow's milk is one of the most common causes of food allergy. In two-thirds of patients, adverse symptoms following milk ingestion are caused by IgE-mediated allergic reactions, whereas for one-third, the mechanisms are unknown. Aim of this study was to investigate whether patients suffering from non-IgE-mediated cow's milk protein intolerance can be distinguished from persons without cow's milk protein intolerance based on serological measurement of IgG and IgA specific for purified cow's milk antigens.

METHODS

We determined IgG(1-4) subclass and IgA antibody levels to purified recombinant αS1-casein, αS2-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin in four patient groups by ELISA: Patients with IgE-mediated cow's milk allergy (CMA, n=25), patients with non-IgE-mediated cow's milk protein intolerance (CMPI, n=19), patients with gastrointestinal symptoms not associated with cow's milk ingestion (GI, n=15) and control persons without gastrointestinal problems (C, n=26). Cow's milk-specific IgE levels were determined by ImmunoCAP.

RESULTS

Only CMA patients had IgE antibodies to cow's milk. Cow's milk allergic patients mounted the highest IgG(1) and IgG(4) antibody levels to αS1-casein, αS2-casein, β-casein, κ-casein, and α-lactalbumin. No elevated levels of IgG(4) , IgA, and complement-binding IgG subclasses (IgG(1) , IgG(2) , IgG(3) ) to purified cow's milk allergens were found within the CMPI patients compared to persons without cow's milk protein intolerance (GI and C groups).

CONCLUSION

Cow's milk protein intolerant patients cannot be distinguished from persons without cow's milk protein intolerance on the basis of IgG subclass or IgA reactivity to cow's milk allergens.

Recombinant allergen-based monitoring of antibody responses during injection grass pollen immunotherapy and after 5 years of discontinuation

BACKGROUND

Subcutaneous injection immunotherapy (SCIT) is considered as antigen-specific and disease-modifying treatment with long-lasting effect.

METHODS

We used a panel of recombinant grass pollen allergens for analyzing allergen-specific IgE, IgG(1) -IgG(4) , IgM, IgA, and light-chain (kappa, lambda) responses in grass pollen-allergic patients who had received one course of injection immunotherapy (SCIT) with an aluminum hydroxide-adsorbed grass pollen extract or only anti-inflammatory treatment. Serum samples were analyzed before and after 5 months of treatment as well as after 5 years.

RESULTS

After 5 months of SCIT but not of anti-inflammatory treatment, IgG(1) > IgG(4) > IgG(2) > IgA antibody responses using both kappa and lambda light chains specific for major grass pollen allergens (Phl p 1, Phl p 5, Phl p 6, Phl p 2) increased significantly, whereas specific IgM or IgG(3) levels were unaltered. Allergen-dependent basophil degranulation was only inhibited with SCIT sera containing therapy-induced allergen-specific IgG antibodies. Likewise, decreases in Phl p 1- and Phl p 5-specific IgE levels and significant (P<0.001) reduction in symptom and medication scores were found only in the SCIT group but not in the group of patients receiving anti-inflammatory treatment. After 5 years, allergen-specific IgG antibody levels in the SCIT group had returned to baseline levels and there was no significant difference regarding symptoms between the SCIT and non-SCIT groups.

CONCLUSION

The results from our observational study demonstrate that only SCIT but not anti-inflammatory treatment induces allergen-specific IgG and reduces boosts of allergen-specific IgE production but that one SCIT course was not sufficient to achieve long-term immunological and clinical effects.

Molecular characterization of Der p 10: a diagnostic marker for broad sensitization in house dust mite allergy

BACKGROUND

Tropomyosins represent clinically relevant seafood allergens but the role of mite tropomyosin, Der p 10, in house dust mite (HDM) allergy has not been studied in detail.

OBJECTIVE

To express and purify a recombinant Der p 10 with equivalent IgE reactivity as natural Der p 10 and to evaluate its IgE reactivity and allergenic activity in HDM-allergic patients.

METHODS

rDer p 10 was expressed in Escherichia coli, purified and characterized by mass spectrometry and circular dichroism. It was tested for IgE reactivity in 1322 HDM-allergic patients. Detailed IgE-reactivity profiles to six HDM allergens (Der p 1, 2, 5, 7, 10, 21) were established for subgroups of Der p 10-positive and -negative patients. The allergenic activity of rDer p 10 was evaluated in basophil degranulation experiments.

RESULTS

rDer p 10 is an α-helical protein sharing IgE epitopes with nDer p 10. It is recognized by 15.2% of HDM-allergic patients. Der p 10-negative patients were primarily sensitized to Der p 1 and/or Der p 2, whereas Der p 10-positive patients reacted to several other HDM allergens besides the major allergens (Der p 1, Der p 2) or showed a rather selective Der p 10 reactivity. The allergenic activity of Der p 10 was generally low but patients could be identified who suffered from clinically relevant HDM allergy due to Der p 10 sensitization.

CONCLUSION AND CLINICAL RELEVANCE

Der p 10 may be a diagnostic marker for HDM-allergic patients with additional sensitization to allergens other than Der p 1 and Der p 2. Such patients may require attention when allergen-specific immunotherapy is considered.

Recombinant allergens for allergen-specific immunotherapy: 10 years anniversary of immunotherapy with recombinant allergens

The broad applicability of allergen-specific immunotherapy for the treatment and eventually prevention of IgE-mediated allergy is limited by the poor quality and allergenic activity of natural allergen extracts that are used for the production of current allergy vaccines. Today, the genetic code of the most important allergens has been deciphered; recombinant allergens equalling their natural counterparts have been produced for diagnosis and immunotherapy, and a large panel of genetically modified allergens with reduced allergenic activity has been characterized to improve safety of immunotherapy and explore allergen-specific prevention strategies. Successful immunotherapy studies have been performed with recombinant allergens and hypoallergenic allergen derivatives and will lead to the registration of the first recombinant allergen-based vaccines in the near future. There is no doubt that recombinant allergen-based vaccination strategies will be generally applicable to most allergen sources, including respiratory, food and venom allergens and allow to produce safe allergy vaccines for the treatment of the most common forms of IgE-mediated allergies.

Microarray and allergenic activity assessment of milk allergens

BACKGROUND

Cow's milk is one of the most common causes of food allergy affecting approximately 2.5% of infants in the first years of their life. However, only limited information regarding the allergenic activity of individual cow's milk allergens is available.

OBJECTIVE

To analyse the frequency of IgE reactivity and to determine the allergenic activity of individual cow's milk allergens.

METHODS

A nitrocellulose-based microarray, based on purified natural and recombinant cow's milk allergens was used to determine IgE reactivity profiles using sera from 78 cow's milk-sensitized individuals of varying ages. The allergenic activity of the individual allergens was tested using patients' sera for loading rat basophil leukaemia cells (RBL) expressing the α-chain of the human receptor FcεRI.

RESULTS

Using the microarray and the RBL assay, cow's milk allergens were assessed for frequency of IgE recognition and allergenic activity. Moreover, the RBL assay allowed distinguishing individuals without or with mild clinical reactions from those with severe systemic or gastrointestinal symptoms as well as persons who grew out cow's milk allergy from those who did not.

CONCLUSIONS

Component-resolved testing using milk allergen microarrays and RBL assays seems to provide useful additional diagnostic information and may represent a basis for future forms of prophylactic and therapeutic strategies for cow's milk allergy.

Association of allergic patients' phenotypes with IgE reactivity to recombinant pollen marker allergens

BACKGROUND

During the last decade allergen molecules from several allergen sources have been produced by recombinant DNA technology. The aim of this study was to investigate whether IgE reactivity to recombinant pollen allergens with broad and narrow cross-reactivity is associated with clinical phenotypes of allergic sensitization.

METHODS

Serum IgE reactivity to a panel of six recombinant birch and grass pollen allergens was measured by ELISA in pollen sensitized patients from Central Europe to define groups of patients with exclusive IgE reactivity to rBet v 1, with exclusive reactivity to major grass pollen allergens (rPhl p 1, rPhl p 2, rPhl p 5) and with IgE reactivity to cross-reactive pollen allergens (rBet v 2, rPhl p 7). Patients' clinical phenotypes were recorded. IgE responses to tree, grass and weed pollen as well as plant food extracts were evaluated in vitro by CAP-FEIA and clinical sensitivities were confirmed in vivo by skin prick testing.

RESULTS

IgE reactivity to the recombinant major birch pollen allergen, rBet v 1, was associated with sensitization to pollen from birch, taxonomically related trees and to certain plant-derived food. Reactivity to the recombinant timothy grass pollen allergens, rPhl p 1, rPhl p 2, rPhl p 5, indicated sensitization to pollen from grasses. Patients reacting with the highly cross-reactive allergen rPhl p 7 were polysensitized to pollen from unrelated trees, grasses and weeds and rBet v 2-positive patients were polysensitized to pollen and plant-derived food from unrelated plants.

CONCLUSIONS

IgE reactivity to recombinant marker allergens is associated with clinical phenotypes of allergic sensitization and may be useful for the selection of treatment strategies.

Anti-calreticulin immunoglobulin A (IgA) antibodies in refractory coeliac disease

Refractory coeliac disease (RCD) is a very rare and dangerous form of CD, in which gluten-free diet loses its therapeutic effect and the damage of intestinal mucosa persists. Because of the adherence to the diet, serological markers of CD [immunoglobulin A (IgA) antibodies against gliadin, tissue transglutaminase (tTG) and endomysium] are often missing in RCD patients. We found substantially elevated levels of IgA anti-calreticulin (CRT) antibodies in the sera of almost all RCD patients tested. These sera were negative for IgA antibodies to gliadin and tTG and only some of them showed IgA antibodies to enterocytes. Analysis of patients' IgA reactivity to CRT fragments (quarters and halves) by Western blotting revealed differences in the specificity of IgA antibodies between RCD and CD patients. We therefore used the Pepscan technique with synthetic overlapping decapeptides of CRT to characterize antigenic epitopes recognized by serum IgA antibodies of RCD patients. Employing this method we demonstrated several dominant antigenic epitopes recognized by IgA antibodies of RCD patients on the CRT molecule. Epitope GVTKAAEKQMKD was recognized predominantly by serum IgA of RCD patients. Our results suggest that testing for serum IgA antibodies against CRT and its selected peptide could be a very useful tool in RCD differential diagnosis.

Different allergenic activity of grass pollen allergens revealed by skin testing

BACKGROUND

Grass pollen is one of the most important allergen sources. The aim of this study was to compare the in vivo allergenic activity of two recently characterized major grass pollen allergens, Phl p 4 and Phl p 13, with three established major grass pollen allergens, Phl p 1, Phl p 2 and Phl p 5 as a basis for the formulation of a grass pollen allergy vaccine based on purified allergens.

MATERIAL AND METHODS

Eighty-two grass pollen allergic patients were skin prick tested with serial dilutions of approximately equimolar concentrations of the purified allergens in a double-blind study.

RESULTS

Phl p 4 and Phl p 13 were identified as major grass pollen allergens according to IgE binding frequency (Phl p 4: 85%; Phl p 13: 56%), but exhibited a five to nine-fold lower allergenic skin reactivity compared to Phl p 1, Phl p 2 or Phl p 5.

CONCLUSION

Our results indicate that Phl p 4 and Phl p 13 are not essential components for a therapeutic grass pollen vaccine and underpin the importance of evaluating the in vivo allergenic activity of individual allergens for the formulation of therapeutic vaccines based on purified allergens.

Sensitization to human milk

BACKGROUND

Allergy to milk is one of the earliest manifestations of IgE-mediated allergies and affects about 2.5% of newborn children. Several reports indicate that milk-allergic patients may be sensitized also to human milk proteins.

OBJECTIVE

To analyse the specificity and possible biological relevance of IgE reactivity to human milk antigens in milk-allergic patients.

METHODS

The specificity of IgE reactivity to cow's milk and human milk antigens was analysed with sera from milk-allergic children and adults by IgE immunoblotting. IgE cross-reactivity between milk antigens was studied by immunoblot inhibition experiments. That IgE reactivity to human milk antigens is not due to alloreactivity or due to the transmission of foreign antigens into mother's milk was demonstrated through the analysis of milk samples from genetically unrelated mothers before and after intake of dietary milk products. The biological relevance of IgE reactivity to human milk was confirmed by skin testing. Results IgE antibodies to human milk were found in more than 80% of the tested milk-allergic patients. Cross-reactive IgE-reactive human antigens such as alpha-lactalbumin and non-cross-reactive human milk antigens were identified. Immediate-type skin reactions could be elicited with human milk samples in patients with IgE reactivity to human milk.

CONCLUSION

IgE reactivity to human milk in milk-allergic patients can be due to cross- sensitization and genuine sensitization to human milk and may cause allergic symptoms. IgE-mediated sensitization to human milk is common in milk-allergic patients and may require diagnostic testing and monitoring.

Detection of an allergen in dog dander that cross-reacts with the major cat allergen, Fel d 1

BACKGROUND

A considerable proportion of animal-allergic patients are sensitized to both cat and dog allergens but knowledge about cross-reactive allergens in cat and dog dander is limited.

OBJECTIVE

To investigate whether dog dander contains an allergen that cross-reacts with the major cat allergen, Fel d 1.

METHODS

Recombinant Fel d 1 with the same immunological properties as natural Fel d 1 was used for quantitative (CAP) IgE competition experiments performed with sera obtained from cat-allergic patients (n=36). A Fel d 1 cross-reactive dog allergen was characterized by one- and two-dimensional immunoblotting using rFel d 1 for IgE inhibition experiments and with monospecific, polyclonal rabbit anti-recombinant Fel d 1 antibodies.

RESULTS

In 25% of Fel d 1-reactive cat-allergic patients, more than 50% inhibition of IgE reactivity to dog allergens was achieved with recombinant Fel d 1. An Fel d 1 cross-reactive 20 kDa allergen with a pI of approximately 3.4 was detected in dander extracts of several different dog breeds.

CONCLUSION

This is the first report demonstrating the presence of an Fel d 1-like allergen in dog dander extracts, which may be responsible for double positivity to cat and dog in serology. However, the clinical relevance of this cross-sensitization needs to be confirmed. These results are important for the diagnostic and therapeutic use of dog dander allergen extracts.

Component-resolved diagnosis to optimize allergen-specific immunotherapy in the Mediterranean area

Allergen-specific immunotherapy (SIT) is the only allergen-specific treatment for allergy. It can prevent progression of the disease and has a long-lasting therapeutic effect. Since SIT is allergen-specific, the identification of the disease-eliciting allergen is an essential prerequisite for the accurate prescription of treatment. Diagnostic tests based on allergen extracts consist of mixtures of various allergens of which some are specific for the allergen source and others occur as cross-reactive allergens in various unrelated allergen sources. It may therefore be difficult and sometimes impossible to identify the disease-causing allergen with such tests, particularly in patients who are sensitized to more than one allergen source. Sensitization to pollens from olive, grasses, and Parietaria in the Mediterranean area is frequently treated with SIT. Here, we describe allergen molecules from these sources that can be used for component-resolved diagnosis of allergy to facilitate the selection of patients for SIT and monitor the immunological effects of treatment.

A pollen-specific polygalacturonase from lily is related to major grass pollen allergens

A pollen-specific gene from lily (Lilium longiflorum Thunb. cv. Snow Queen), designated LLP-PG, was characterized. Southern blots of lily genomic DNA indicated that LLP-PG is a member of a small gene family. A thorough sequence analysis revealed that the LLP-PG gene is interrupted by two introns and encodes a protein of 413 amino acids, with a calculated molecular mass of 44 kDa, and a pI of 8.1. Evaluation of the hydropathy profile showed that the protein has a hydrophobic segment at the N-terminus, indicating the presence of a putative signal peptide. A sequence similarity search showed a significant homology of the encoded protein to pollen polygalacturonases (PGs) from various plant species and to an important group (group 13) of grass pollen allergens. The LLP-PG transcript is pollen-specific and it accumulates only at the latest stage during pollen development, in the mature pollen. In contrast to other "late genes" LLP-PG transcript can neither be induced by abscisic acid (ABA) nor by dehydration. Immunoblot analyses of pollen protein extracts from lily, timothy grass and tobacco with IgG antibodies directed against LLP-PG and against the timothy grass pollen allergen, Phl p 13, indicated that lily LLP-PG shares surface-exposed epitopes with pollen PGs from monocotyledonous and dicotyledonous plants. Enzyme-linked immunosorbent assay (ELISA) analyses and inhibition ELISA assays with patients' IgE demonstrated a very low IgE reactivity of lily rLLP-PG and a lack of cross-reactivity between rLLP-PG and the timothy grass pollen allergen, rPhl p 13. These data demonstrated that despite the significant sequence homology and the conserved surface-exposed epitopes LLP-PG represents a low-allergenic member of pollen PGs.

Characterization of recombinant cat albumin

BACKGROUND

Indoor allergens derived from animals and mites often contribute to exacerbation of skin manifestations in atopic dermatitis (AD) patients.

OBJECTIVE

To produce and characterize recombinant cat albumin, a cross-reactive animal allergen.

METHODS

A complete cDNA coding for cat albumin was obtained by RT-PCR amplification from cat liver RNA. Recombinant cat albumin was expressed in Escherichia coli as hexahistidine-tagged protein, purified by nickel affinity chromatography and studied for IgE reactivity with sera from cat-allergic patients by ELISA and immunoblotting. Furthermore, CD203c expression of basophils from cat-allergic patients upon exposure to recombinant cat albumin was analysed.

RESULTS

Recombinant cat albumin, a cross-reactive animal allergen sharing most IgE epitopes with its natural counterpart, was produced in E. coli. It was recognized preferentially by IgE from AD patients and elicited IgE-dependent basophil activation in sensitized patients.

CONCLUSIONS

Recombinant cat albumin may be used as a paradigmatic tool to analyse mechanisms of allergen-triggered exacerbation of AD, for diagnostic and, perhaps for therapeutic purposes.

Identification of pronp1, a tobacco profilin gene activated in tip-growing cells

In plant cells, several cellular processes depend on rapid reorganization of a dynamic network of actin cytoskeletal elements in response to internal and environmental stimuli. Profilins, ubiqitous eukaryotic actin monomer-binding proteins with highly conserved three-dimensional structures, regulate the actin cytoskeleton and are considered to link the microfilament system with signal transduction pathways. Plant profilins have been grouped into two distinct classes, gametophytic (pollen-specific) and sporophytic. Here we report the isolation of a profilin gene that seems to be activated during tip growth of specialized cells of gametophytic as well as sporophytic origin. Identification of a genomic DNA clone containing a tobacco profilin gene, pronp1, and analysis of the pronp1 promoter-uidA fusion gene in transgenic Nicotiana tabacum plants revealed a prominent expression of pronp1 in mature pollen and elongating pollen tubes and significant activity in root hairs of developing seedlings. This expression pattern was distinct from that of any other profilin gene isolated so far. Pronp1 thus represents a unique profilin gene that is activated at the transcriptional level in two kinds of tip-growing cells, pollen tubes and root hairs, both of which require rapid organization of the actin cytoskeleton. The isolation of such a gene has fundamental importance for our understanding of modulation of the actin cytoskeleton at the molecular level.

Reduction in allergenicity of grass pollen by genetic engineering

BACKGROUND

Hay fever and allergic asthma triggered by grass pollen allergens affect approximately 20% of the population in cool temperate climates. Ryegrass is the dominant source of allergens due to its prodigious airborne pollen production. Lol p 5 or group 5 is among the most important and widespread grass pollen allergen because it reacts with IgE antibodies of more than 90% of grass pollen-allergic patients, contains most of the grass pollen-specific IgE epitopes and elicits strong biological responses. Significant efforts have been made in developing diagnostic and therapeutic reagents for designing new and more effective immunotherapeutic strategies for treatment of allergic diseases. An alternative approach to this problem could be to reduce the amount of allergen content in the source plant.

METHODS

High velocity microprojectile bombardment was used to genetically engineer ryegrass. Antisense construct targeted to one of major allergen, Lol p 5, was introduced. The expression of antisense RNA was regulated by a pollen-specific promoter. Pollen was analysed for IgE reactivity.

RESULTS

Analysis of proteins with allergen-specific monoclonal and polyclonal antibodies did not detect Lol p 5 in the transgenic pollen. The transgenic pollen showed remarkably reduced allergenicity as reflected by low IgE binding capacity of pollen extract as compared to control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development.

CONCLUSIONS

Our studies showed that it is possible to selectively 'switch off' allergen production in pollen of ryegrass demonstrating feasibility of genetic engineering of plants for reduced allergenicity.

Escherichia coli expression and purification of recombinant dog albumin, a cross-reactive animal allergen

BACKGROUND

Animal hair-dander represents an important source of indoor allergens. Diagnosis and therapy of animal allergy would benefit from the availability of defined recombinant allergens. They may be preferred to animal-derived proteins, particularly for in vivo application in patients.

OBJECTIVE

The purpose of this study was to express and purify recombinant dog albumin, an important cross-reactive animal allergen.

METHODS

Complementary (c)DNA sequences coding for dog albumin were obtained by reverse transcription and subsequent PCR amplification from dog liver RNA. Dog albumin-encoding cDNA sequences were inserted into phage lambdagt11, and IgE-reactive phage clones were isolated by immunoscreening with serum IgE from a patient with dog allergy. Dog albumin was expressed as IgE-reactive recombinant protein in Escherichia coli and purified by inclusion body preparation, resolubilization, and diethylaminoethyl cellulose chromatography. Cross-reactivity of dog albumin with cat and human albumin was examined by immunoblot, as well as ELISA inhibition experiments.

RESULTS

A cDNA sequence coding for complete dog albumin was obtained by reverse transcription and subsequent PCR amplification from dog liver. The cDNA and deduced amino acid sequence of dog albumin was highly homologous to the sequences of albumins from animals to human subjects, thus explaining the extensive cross-reactivities among albumins. Recombinant dog albumin was expressed in E coli and purified. It reacted with serum IgE from patients allergic to dog albumin and a monoclonal anti-human albumin antibody. Immunologic competition experiments performed with serum IgE from patients allergic to dog albumin and a mouse monoclonal antihuman albumin antibody indicated the presence of similar epitopes on dog, cat, and human albumin.

CONCLUSION

Recombinant dog albumin may be used for diagnostic purposes to identify patients who are cross-sensitized to many animal species and perhaps for specific immunotherapy of sensitized individuals.

Antisense-mediated silencing of a gene encoding a major ryegrass pollen allergen

Type 1 allergic reactions, such as hay fever and allergic asthma, triggered by grass pollen allergens are a global health problem that affects approximately 20% of the population in cool, temperate climates. Ryegrass is the dominant source of allergens because of its prodigious production of airborne pollen. Lol p 5 is the major allergenic protein of ryegrass pollen, judging from the fact that almost all of the individuals allergic to grass pollen show presence of serum IgE antibodies against this protein. Moreover, nearly two-thirds of the IgE reactivity of ryegrass pollen has been attributed to this protein. Therefore, it can be expected that down-regulation of Lol p 5 production can significantly reduce the allergic potential of ryegrass pollen. Here, we report down-regulation of Lol p 5 with an antisense construct targeted to the Lol p 5 gene in ryegrass. The expression of antisense RNA was regulated by a pollen-specific promoter. Immunoblot analysis of proteins with allergen-specific antibodies did not detect Lol p 5 in the transgenic pollen. The transgenic pollen showed remarkably reduced allergenicity as reflected by low IgE-binding capacity of pollen extract as compared with that of control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development, indicating that genetic engineering of hypoallergenic grass plants is possible.

Male gametic cell-specific gene expression in flowering plants

The role of the male gamete-the sperm cell-in the process of fertilization is to recognize, adhere to, and fuse with the female gamete. These highly specialized functions are expected to be controlled by activation of a unique set of genes. However, male gametic cells traditionally have been regarded as transcriptionally quiescent because of highly condensed chromatin and a very reduced amount of cytoplasm. Here, we provide evidence for male gamete-specific gene expression in flowering plants. We identified and characterized a gene, LGC1, which was shown to be expressed exclusively in the male gametic cells. The gene product of LGC1 was localized at the surface of male gametic cells, suggesting a possible role in sperm-egg interactions. These findings represent an important step toward defining the molecular mechanisms of male gamete development and the cellular processes involved in fertilization of flowering plants.

Male gametic cell-specific expression of H2A and H3 histone genes

Formation of the generative cell in flowering plants initiates the male spermatogenesis pathway which eventually culminates in the process of double fertilization. Little is known about the molecular mechanisms operative in the generative cell. Here, we report the isolation and characterization of cDNA clones encoding generative cell-specific histones, gcH2A and gcH3. In situ hybridization analysis revealed that both genes are activated after formation of the generative cell and accumulation of transcripts increases progressively during generative cell maturation. These results suggest that gcH2A and gcH3 mRNAs are products of transcriptional activation of the generative cell nucleus and thus provide the first evidence for male germ line cell-specific gene expression in flowering plants.

Engineering of hypoallergenic mutants of the Brassica pollen allergen, Bra r 1, for immunotherapy

The Brassica pollen allergen Bra r 1 belongs to a new family of Ca2+-binding proteins, characterized by the presence of two potential EF-hand calcium-binding domains. Disruption of these EF-hand motifs by amino acid substitutions demonstrated that both domains of Bra r 1 constitute functional Ca2+-binding sites. Calcium-binding deficient mutants displayed significantly reduced IgE-binding activity. Injection of these mutated Bra r 1 variants into a murine model system showed that mouse IgG raised against the mutants recognized native Bra r 1 in Brassica pollen extracts suggesting the potential use of the engineered allergens for effective immunotherapy.

Plant homologue of human excision repair gene ERCC1 points to conservation of DNA repair mechanisms

Nucleotide excision repair (NER), a highly versatile DNA repair mechanism, is capable of removing various types of DNA damage including those induced by UV radiation and chemical mutagens. NER has been well characterized in yeast and mammalian systems but its presence in plants has not been reported. Here it is reported that a plant gene isolated from male germline cells of lily (Lilium longiflorum) shows a striking amino acid sequence similarity to the DNA excision repair proteins human ERCC1 and yeast RAD10. Homologous genes are also shown to be present in a number of taxonomically diverse plant genera tested, suggesting that this gene may have a conserved function in plants. The protein encoded by this gene is able to correct significantly the sensitivity to the cross-linking agent mitomycin C in ERCC1-deficient Chinese hamster ovary (CHO) cells. These findings suggest that the NER mechanism is conserved in yeast, animals and higher plants.

Identification of a Ca2+ binding protein as a new Bermuda grass pollen allergen Cyn d 7: IgE cross-reactivity with oilseed rape pollen allergen Bra r 1

cDNA clones encoding two isoforms of an allergen from pollen of Bermuda grass (Cynodon dactylon) have been isolated using IgE from allergic patients. Homologous transcripts are present in pollen of 15 other grasses tested. This allergen, tentatively designated as Cyn d 7, contains two calcium binding domains and shows significant sequence similarity with other Ca2+ binding pollen allergens, namely Bet v 4 from birch and Bra r 1 from oilseed rape. Approximately 10% of allergic sera tested showed IgE reactivity to this allergen. IgE cross-reactivity was observed between this allergen and Bra r 1 of oilseed rape. IgE reactivity of this allergen requires protein-bound Ca2+. Using IgE affinity-purified from the recombinant allergen to probe Western blots of pollen extracts Cyn d 7 has been identified as a 12 kDA protein.

RAPD analysis of genetic variation in the Australian fan flower, Scaevola

The use of randomly amplified polymorphic DNA (RAPD) to study genetic variability in Scaevola (family Goodeniaceae), a native Australian species used in ornamental horticulture, is demonstrated. Plants of the genus Scaevola are commonly known as "fan flowers," due to the fan-like shape of the flowers. Nineteen accessions of Scaevola (12 cultivated and 7 wild) were studied using 20 random decamer arbitrary primers. Eight primers gave a distinct reproducible amplification profile of 90 scorable polymorphic fragments, enabling the differentiation of the Scaevola accessions. RAPD amplification of genomic DNA revealed a high genetic variability among the different species of Scaevola studied. Molecular markers were used to calculate the similarity coefficients, which were then used for determining genetic distances between each of the accessions. Based on genetic distances, a dendrogram was constructed. Though the dendrogram is in general agreement with the taxonomy, it also highlights discrepancies in the classification. The RAPD data showed that Scaevola aemula (series Pogogynae) is closer to Scaevola glandulifera of series Globuliferae than to the rest of members of series Pogogynae. In addition, the RAPD banding pattern of white flower S. aemula, one of the commercial cultivars, was identical to that of Scaevola albida, indicating their genetic similarity. Our study showed that there is a large genetic distance between commercial cultivars of Scaevola (Purple Fanfare, Pink Perfection, and Mauve Cluster), indicating considerable genetic variation among them. The use of RAPDs in intra- and inter-specific breeding of Scaevola is also explored.

Developmental and cell cycle regulation of alfalfa nucMs1, a plant homolog of the yeast Nsr1 and mammalian nucleolin

We report here the isolation and characterization of the nucMs1 alfalfa cDNA, whose predicted amino acid sequence structurally resembles the yeast Nsr1 protein and animal nucleolins. These proteins consist of an N-terminal acidic domain, centrally located RNA recognition motifs (RRMs), and a C-terminal glycine- and arginine-rich domain. In comparison with animal nucleolins that contain four RRMs, NucMs1 more closely resembles the yeast Nsr1 protein, which contains only two RRMs. A NucMs1 C-terminal peptide antibody specifically recognized a 95-kD nucleolar protein in alfalfa cells that changed its localization in a cell cycle-dependent manner. The nucMs1 transcript and p95nucMs1 protein levels correlated with cell proliferation, and nucMs1 gene expression was found to be induced in the G1 phase upon mitogenic stimulation of G0-arrested leaf cells. In situ hybridization analysis of different alfalfa organs during various developmental stages showed that nucMs1 gene expression is highest in root meristematic cells, but it is also found in other meristematic cells of the plant body. nucMs1 expression is tightly linked to cell proliferation but does not depend on a particular cell cycle phase. No nucMs1 expression was observed in cells that had exited the cell cycle and were undergoing differentiation or polar growth, indicating that nucMs1 may not be necessary for processes other than cell proliferation.

Biological and immunological importance of Bet v 1 isoforms

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

The D-type alfalfa cyclin gene cycMs4 complements G1 cyclin-deficient yeast and is induced in the G1 phase of the cell cycle

Cyclins are key regulators of the cell cycle in all eukaryotes. In alfalfa, we have previously isolated three B-type cyclins. The closely related cycMs1 and cycMs2 genes are expressed primarily during the G2 and M phases and are most likely mitotic cyclins; expression of the cycMs3 gene is induced in the G0-to-G1 transition, when cells reenter the cell cycle. By complementation of G1 cyclin-deficient yeast cells, a novel alfalfa cyclin, designated cycMs4, was isolated. The predicted amino acid sequence of the cycMs4 gene is most similar to that of the Arabidopsis cyclin delta 3 gene. CycMs4 and cyclin delta 3 belong to the class of D-type cyclins and contain PEST-rich regions and a retinoblastoma binding motif. When comparing expression levels in different organs, cycMs4 transcripts were present predominantly in roots. Whereas expression of the cycMs4 gene was cell cycle-regulated in suspension-cultured cells, transcription in roots was observed to depend also on the positional context of the cell. When differentiated G0-arrested leaf cells were induced to resume cell division by treatment with plant hormones, cycMs4 transcription was induced before the onset of DNA synthesis. Whereas this induction was preceded by that of the cycMs3 gene, cycMs2 expression occurred later and at the same time as mitotic activity. These data suggest that cycMs4 plays a role in the G1-to-S transition and provide a model to investigate the plant cell cycle at the molecular level.

cycMs3, a novel B-type alfalfa cyclin gene, is induced in the G0-to-G1 transition of the cell cycle

Cyclins are key regulators of the cell cycle in all eukaryotes. We have previously isolated two B-type cyclin genes, cycMs1 and cycMs2, from alfalfa that are primarily expressed during the G2-to-M phase transition and are most likely mitotic cyclin genes. Here, we report the isolation of a novel alfalfa cyclin gene, termed cycMs3 (for cyclin Medicago sativa), by selecting for mating type alpha-pheromone-induced cell cycle arrest suppression in yeast. The central region of the predicted amino acid sequence of the cycMs3 gene is most similar to the cyclin box of yeast B-type and mammalian A- and B-type cyclins. In situ hybridization showed that cycMs3 mRNA can be detected only in proliferating cells and not in differentiated alfalfa cells. When differentiated G0-arrested cells were induced to reenter the cell cycle in the G1 phase and resume cell division by treatment with plant hormones, cycMs3 transcript levels increased long before the onset of DNA synthesis. In contrast, histone H3-1 mRNA and cycMs2 transcripts were not observed before DNA replication and mitosis, respectively. In addition, cycMs3 mRNA was found in all stages of the cell cycle in synchronously dividing cells, whereas the cycMs2 and histone H3-1 genes showed a G2-to-M phase- or S phase-specific transcription pattern, respectively. These data suggest that the role of cyclin CycMs3 differs from that of CycMs1 and CycMs2. We propose that CycMs3 helps control reentry of quiescent G0-arrested cells into the G1 phase of the cell cycle.

Isoforms of Bet v 1, the major birch pollen allergen, analyzed by liquid chromatography, mass spectrometry, and cDNA cloning

Bet v 1, the major allergen of birch pollen, displays a considerable degree of heterogeneity. Several charge variants have been detected by two-dimensional IgE immunoblots and isoelectric focusing techniques. This heterogeneity has been attributed to glycosylation (or other post-translational modifications) or to isogenes coding for Bet v 1 isoforms and/or allelic variants. However, until now, only limited structural data for Bet v 1 have been published. Recently, we described the expression, purification, and immunological properties of recombinant Bet v 1 (rBet v 1) produced in Escherichia coli as a non-fusion protein (Ferreira, F. D., Hoffmann-Sommergruber, K., Breiteneder, H., Pettenburger, K., Ebner, C., Sommergruber, W., Steiner, R., Bohle, B., Sperr, W. R., Valent, P., Kungl, A. J., Breitenbach, M., Kraft, D., and Scheiner, O. (1993) J. Biol. Chem. 268, 19574-19580). Here, we present a more detailed structural characterization of Bet v 1 by both cDNA cloning and mass spectrometry. Thirteen different cDNA clones coding for Bet v 1 isoforms were obtained by polymerase chain reaction amplification of birch pollen cDNA with a sequence-specific 5'-terminal primer and a nonspecific 3'-terminal primer or by immunological screening of a birch pollen cDNA library. These isoforms are referred to as Bet v 1b to Bet v 1n, whereas the previously isolated Bet v 1 cDNA (Breiteneder, H., Pettenburger, K., Bito, A., Valenta, R., Kraft, D., Rumpold, H., Scheiner, O., and Breitenbach, M. (1989) EMBO J. 8, 1935-1938) is now referred to as Bet v 1a. High performance liquid chromatography and plasma desorption mass spectrometry of proteolytic fragments of purified natural Bet v 1 (nBet v 1) and rBet v 1a were used to (i) confirm the primary structure of all Bet v 1 isoforms and (ii) to investigate any possible postsynthetic modifications on rBet v 1a or on the natural mixture of isoallergens obtained from birch pollen. Except for the cleavage of initiating methionine, no postsynthetic modifications were found in either nBet v 1 or rBet v 1a.

Molecular cloning and characterization of profilin from tobacco (Nicotiana tabacum): increased profilin expression during pollen maturation

Profilin has recently been identified as an actin-binding protein in higher plants. A cDNA coding for tobacco profilin, which shared an average sequence identity of 75% with other plant profilins, was isolated from a tobacco pollen cDNA library by antibody screening. Tobacco profilin was expressed in Escherichia coli and purified by affinity to poly-(L-proline) Sepharose. A rabbit antiserum was raised against recombinant tobacco profilin and used to estimate the amount of profilin expressed in different tobacco tissues. Profilin can be detected in different somatic tissues, but the expression is 50-100 fold higher in mature pollen. Immunofluorescence and confocal laser scanning microscopy showed a homogeneous distribution of profilin in the cytoplasm of in vitro cultured pollen grains and pollen tubes of tobacco whereas some growing pollen tubes were stained more intensively a their tip. A possible role of pollen profilin as a developmentally upregulated microfilament precursor in mature pollen is discussed.

A birch gene family encoding pollen allergens and pathogenesis-related proteins

Bet v I, the major pollen allergen of birch (Betula verrucosa), shows high sequence homology to a family of pathogenesis-related (PR) proteins that have recently been identified in several other plant species. We have used a pollen Bet v I cDNA clone and anti-Bet v I antibodies as probes to study the expression of Bet v I genes in birch cell suspension cultures under different experimental conditions. Induction of Bet v I-related proteins was detected in immunoblots of cell extracts upon co-cultivation with microbial pathogens. Northern analysis revealed the rapid induction of Bet v I transcripts in the presence of bacteria and fungi, but not by stress treatments (heat shock, metal ions) or by chemical elicitors. RNase protection experiments showed that the pathogen-inducible RNAs did not correspond to the pollen cDNA clone but most likely to the products of transcription of other members of the Bet v I gene family, sharing high sequence homology with the pollen-specific gene within the 5'-half of the coding region. We conclude that the Bet v I gene family of pollen allergens includes a subset of defense-related genes that are transcriptionally activated in the presence of microbial pathogens.

Identification of profilin as an actin-binding protein in higher plants

Profilin is a low molecular weight protein involved in the organization of the mammalian and protozoan cytoskeleton as well as in signal transduction. In this study, profilin is identified as an actin-binding protein in higher plants which is present in monocot and dicot angiosperms. Birch pollen profilin and actin can be copurified as a complex, and purified recombinant birch profilin can be used as an affinity matrix to obtain birch pollen actin. The binding of 125I-labeled recombinant birch pollen profilin to plant and animal actins can be blocked by profilin-specific antibodies that react with different epitopes of birch profilin. One of the blocking antibodies was raised against the 25 COOH-terminal amino acids indicating the importance of this region in the profilactin complex formation.

Distribution of allergens and allergen-coding mRNAs in various tissues of white birch

The distribution of allergenic proteins was investigated in various tissues of white birch, Betula verrucosa (pollen, leaves and male inflorescences containing immature pollen). In addition, callus and suspension culture cells were investigated for expression of IgE-binding proteins. Furthermore, RNA was extracted from all these tissues and subjected to in vitro translation in a cell-free wheat germ system. Bet v I, the major birch pollen allergen, could be extracted easily from pollen, and in low amounts from callus and leaves. No Bet v I could be extracted from immature male inflorescences. Minor allergens were expressed in high concentrations in pollen and in low concentrations in immature male inflorescences. No minor allergens could be detected in callus and leaves. In contrast to these observations, RNA from all the tissues as well as from callus could be translated in vitro into Bet v I as well as into minor allergens, in particular birch profilin (Bet v II), an important minor allergen. These data suggest that IgE-binding proteins of B. verrucosa, especially Bet v I, under certain circumstances can readily be synthesized in tissues other than pollen. This concept is corroborated by the recent observation that Bet v I reveals high homology with disease resistance response gene products from other plants, suggesting a similar function of Bet v I for the birch.