Api m 6: a new bee venom allergen

BACKGROUND: Characterization of the primary structure of allergens is a prerequisite for the design of new diagnostic and therapeutic tools for allergic diseases. OBJECTIVE: The purpose of this study was the identification and characterization of a low-molecular-weight, IgE-binding, bee venom (BV) allergen. METHODS: BV proteins were separated by using size exclusion chromatography and HPLC. IgE antibody binding to purified proteins was analyzed by means of immunoblotting, and T-cell response was analyzed by means of proliferation assay. Amino acid sequence was determined with 2 approaches, namely Edman degradation and carboxy terminal analysis with mass spectrometry. RESULTS: Api m 6, which migrated as an 8-kd band in SDS-PAGE, was frequently (42%) recognized by IgE from BV-hypersensitive patients. In addition, PBMCs from BV-hypersensitive patients, as well as from a normal control subject, proliferated in response to this allergen. Api m 6 exists as 4 isoforms of 7190, 7400, 7598, and 7808 d, respectively. Amino acid sequences obtained from HPLC-purified preparations revealed that the isoforms were constituted of a common central core of 67 residues, only differing in the amino- and carboxy-terminal ends. Api m 6 showed no significant sequence homology with known proteins. CONCLUSIONS: We have identified and sequenced a new BV allergen that elicits a strong IgE and T-cell response in a large number of BV-hypersensitive patients. Api m 6 should be considered in the diagnostic and therapeutic approach of BV immunotherapy on the basis of peptides or recombinant proteins.     

Molecular cloning and expression in insect cells of honeybee venom allergen acid phosphatase (Api m 3)

BACKGROUND: Acid phosphatase (Api m 3) is a major allergen in honeybee (Apis mellifera) venom, and its availability as a recombinant protein may facilitate the development of improved diagnostic tests and immunotherapies. OBJECTIVE: One objective is the determination of the complete primary structure of Api m 3 and to obtain recombinant Api m 3 on the basis of expression in insect cells. Another objective is the quantitative analysis of patient serum IgE antibody reactive to recombinant Api m 3. METHODS: The cloning of Api m 3 from venom gland cDNA and its expression as a full-length protein in eukaryotic insect cells is described. The immunoreactivity of serum IgE antibodies of honeybee venom-sensitized patients to recombinant Api m 3 was determined in an enzyme immunoassay. RESULTS: PCR amplification generated a 1122-bp DNA fragment whose identity as the coding sequence of Api m 3 was verified by several means. Recombinant Api m 3, expressed in Trichoplusia ni cells, showed an expected molecular weight and enzymatic activity at pH 4.5. Analysis of tryptic fragments of purified recombinant Api m 3 by mass spectrometry confirmed its identity. In immunoassays, recombinant Api m 3 is specifically recognized by IgE antibodies of pooled serum in Western blots and by 37% of the individual sera of honeybee venom-sensitized patients in ELISA analysis. CONCLUSION: The availability of recombinant Api m 3 provides a tool for both the development of improved diagnostic tests and the design of safer and more effective immunotherapeutic approaches for honeybee venom allergy. CLINICAL IMPLICATIONS: The recombinant venom allergen Api m 3 is a key element in the search for an optimized component-resolved approach to honeybee venom allergy with regard to both the development of superior diagnostic tests and the improvement of allergen immunotherapy.     

Hymenoptera venom allergy: analysis of double positivity to honey bee and Vespula venom by estimation of IgE antibodies to species-specific major allergens Api m1 and Ves v5

Background:  In patients with hymenoptera venom allergy diagnostic tests are often positive with honey bee and Vespula venom causing problems in selection of venoms for immunotherapy.
Methods:  100 patients each with allergic reactions to Vespula or honey bee stings and positive i.e. skin tests to the respective venom, were analysed for serum IgE to bee venom, Vespula venom and crossreacting carbohydrate determinants (CCDs) by UNICAP (CAP) and ADVIA Centaur (ADVIA). IgE-antibodies to species specific recombinant major allergens (SSMA) Api m1 for bee venom and Ves v5 for Vespula venom, were determined by ADVIA. 30 history and skin test negative patients served as controls.
Results:  By CAP sensitivity was 1.0 for bee and 0.91 for Vespula venom, by ADVIA 0.99 for bee and 0.91 for Vespula venom. None of the controls were positive with either test. Double positivity was observed in 59% of allergic patients by CAP, in 32% by ADVIA. slgE to Api m1 was detected in 97% of bee and 17% of Vespula venom allergic patients, slgE to Ves v5 in 87% of Vespula and 17% of bee venom allergic patients. slgE to CCDs were present in 37% of all allergic patients and in 56% of those with double positivity and were more frequent in bee than in Vespula venom allergic patients.
Conclusions:  Double positivity of IgE to bee and Vespula venom is often caused by crossreactions, especially to CCDs. IgE to both Api m1 and Ves v5 indicates true double sensitization and immunotherapy with both venoms.     

Mutational epitope analysis and cross-reactivity of two isoforms of Api g 1, the major celery allergen

For better understanding the cross-reactivity between the major birch pollen and celery allergens, Bet v 1 and Api g 1, respectively, putative epitope areas and structurally important positions for IgE-binding of the isoforms Api g 1.01 and Api g 1.02 were point mutated. The IgE binding capacities were measured in ELISA, the IgE cross-reactivity between the isoforms, mutants and Bet v 1 investigated by ELISA-inhibition experiments with serum pools from patients with confirmed celery allergy (DBPCFC). Api g 1.01 displayed a clearly higher frequency and capacity of IgE binding than Api g 1.02. In Api g 1.01, substitution of lysine against glutamic acid at amino acid position 44, a key residue of the Bet v 1 "P-loop", increased the IgE-binding properties. Structural instability due to proline insertion at position 111/112 resulted in loss of IgE binding of Api g 1.01, but not of Api g 1.02. Between Api g 1.01 and Api g 1.02 only partial cross-reactivity was seen. The data suggest that the IgE epitopes of the two isoforms are distinct and that in contrast to Api g 1.01, the "P-loop" region plays an important role for IgE binding of celery allergic subjects to Api g 1.02. Understanding and investigation of the molecular mechanisms in celery allergy is an important step to generate hypoallergenic proteins for safe and efficacious immunotherapy of food allergy.     

Mimotopes for Api g 5, a Relevant Cross-reactive Allergen,in the Celery-Mugwort-Birch-Spice Syndrome

Purpose

In the celery-mugwort-birch-spice syndrome, a significant proportion of IgE is directed against high molecular weight (HMW) glycoproteins, including the celery allergen Api g 5. BIP3, a monoclonal antibody originally raised against birch pollen, recognizes HMW allergens in birch and mugwort pollens, celery, and Apiaceae spices. Our aim was to generate mimotopes using BIP3 for immunization against the HMW allergens relevant in the celery-mugwort-birch-spice cross reactivity syndrome.

Methods

Mimotopes were selected from a random-peptide display library by BIP3 and applied in IgE inhibition assays. The 3 phage clones with the highest inhibitory capacity were chosen for immunization of BALB/c mice. Mouse immune sera were tested for IgG binding to blotted birch pollen extract and used for inhibiting patients'' IgE binding. Furthermore, sera were tested for binding to Api g 5, to horseradish peroxidase (HRP) as a second glycoprotein, or to non-glycosylated control allergen Phl p 5 in ELISA, and the specific Api g 5-specific IgG titers were determined.

Results

Three rounds of biopanning resulted in phage clones exhibiting 7 different sequences including 1 dominant, 1-6-cyclo-CHKLRCDKAIA. Three phage clones had the capacity to inhibit human IgE binding and induced IgG to the HMW antigen when used for immunizing BALB/c mice. The induced BIP3-mimotope IgG reached titers of 1:500 specifically to Api g 5, but hardly reacted to glycoprotein HRP, revealing a minor role of carbohydrates in their epitope.

Conclusions

The mimotopes characterized in this study mimic the epitope of BIP3 relevant for Api g 5, one of the cross-reactive HMW allergens relevant in the celery-mugwort-birch-spice syndrome. BIP3 mimotopes may be used in the future for hyposensitization in this clinical syndrome by virtue of good and specific immunogenicity.     

Characterization of api g 1.0201, a new member of the Api g 1 family of celery allergens

BACKGROUND: The association of pollinosis with allergy to plant foods occurs in up to 70% of tree pollen-allergic patients. In recent years, some of the relevant cross-reacting proteins have been characterized at the molecular and immunological level. Api g 1 has been identified as the celery homologue of the major birch pollen allergen, Bet v 1. Although a number of Bet v 1 isoforms have been characterized from birch pollen, little is known about isoforms of food allergens and their allergenic features. METHODS: Api g 1.0201, an isoform of Api g 1, was isolated from a cDNA library, cloned and sequenced. The cDNA was expressed in Escherichia coli and the purified recombinant protein was tested in immunoblots. RESULTS: Api g 1.0201 displays 72% sequence similarity to the previously identified Api g 1.0101 and consists of 159 amino acid residues. The sequence of Api g 1.0201 has five additional amino acid residues at the carboxy-terminus as compared to Api g 1.0101. Purified recombinant Api g 1.0201 is recognized by IgE from the sera of celery-allergic patients, as well as by the murine monoclonal anti-Bet v 1 antibody. In general, this isoform displays a weaker IgE-binding capacity than Api g 1.0101, as concluded from immunoblotting experiments. Results from inhibition assays revealed that IgE-binding to Api g 1.0201 is only slightly reduced by preincubation with either purified recombinant Api g 1.0101 or purified recombinant Bet v 1a. Total inhibition was only achieved when using purified natural Bet v 1. CONCLUSIONS: At present, little is known about the IgE-binding capacity of isoforms of Bet v 1 homologues of food allergens. Identification and characterization of such isoforms may help to contribute to a better understanding of food allergy and the observed cross-reactivity to pollen allergy.     

Muscle fiber type analysis in the mouse m. digastricus, m. stylohyoideus, m. zygomaticus and m. buccinator

It is generally accepted in vertebrates that large motor nerve fibers innervate the white (fast) muscle fibers and small motor nerve fibers innervate the red (slow) muscle fibers. In the previous study (SHIMOZAWA, NAKAMURA 1985), we showed that nerve branches to the venter caudalis m. digastrici and m. stylohyoideus of the mouse consist of considerably larger myelinated nerve fibers compared with the truncus facialis distal to the foramen stylomastoideum innervating the other skeletal muscles in the face. To examine the relationship between the size of nerve fibers and the type of muscle fibers, we performed, in this investigation, quantitative analysis of muscle fiber types (white, intermediate and red) in the venter rostralis (RD) et venter caudalis (CD) m. digastrici, m. stylohyoideus (St), m. zygomaticus (Zy) and m. buccinator (Bu) of the mouse with the Sudan Black B stain preparations. Ratios of the number of muscle fibers of 3 types were RD (28.1%), CD (24.6%), St (27.5%), Bu (28.5%) less than Zy (40.8%) for the white muscle fibers, the RD (58.5%), CD (62.9%), St (53.9%), Bu (60.3%) greater than Zy (47.3%) for the red muscle fibers, while differences between the ratios for these muscles were not significant for the intermediate muscle fibers. Mean major and minor diameters and average transverse areas of the muscle fibers of 3 types were white greater than intermediate greater than red muscle fiber in all muscles examined in this study. When compared between these muscles, they were RD, CD, St greater than Zy, Bu for any type of muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)