Detection of IgE- and IgG-binding proteins after electrophoretic transfer from polyacrylamide gels

Molecular Allergen-Specific IgE Assays as a Complement to Allergen Extract-Based Sensitization Assessment

Molecular allergen-based component-resolved diagnostic IgE antibody tests have emerged in the form of singleplex assays and multiplex arrays. They use both native and recombinant allergen molecules, sometimes in combination with each other, to supplement allergen extract-based IgE antibody analyses. The total number of available allergenic molecules has reached a diagnostically useful level; however, more molecules are needed to cover all the clinically important allergen specificities. Thus, for the foreseeable future, molecular allergen-specific IgE analyses will remain a supplement for initial allergen extract-based IgE antibody analyses in the diagnostic workup of the allergic patient. As a spin-off, it will enable manufacturers to improve the quality of extracts for in vitro testing. The 2 most exciting diagnostic developments linked to component-resolved diagnostic tests are the possibility to increase diagnostic sensitivity by the inclusion of allergens that are underrepresented in the current extracts and in vitro assays and to increase the diagnostic specificity by taking the information on allergen cross-reactivity into account. Particularly the latter application is still under development. This requires additional studies on the clinical relevance of serological cross-reactivity.

Potential, pitfalls, and prospects of food allergy diagnostics with recombinant allergens or synthetic sequential epitopes

This article aims to critically review developments in food allergy diagnostics with regard to the verification of specific IgE antibodies and the identification of the responsible allergens. Results of IgE-binding tests with food extracts are hampered by cross-reactive proteins, low-quality test agents, or both. Specificity can be increased by defining adequate cutoff values, whereas sensitivity can be improved by using high-quality test agents. IgE-binding tests with purified allergens enabled reliable quantification of allergen-specific IgE titers, with higher levels found in individuals with food allergy compared with individuals without food allergy. However, the overlap in individual test reactivity between allergic and nonallergic subjects complicates interpretation. Recombinant allergens and synthetic sequential epitopes enabled detection of sensitization profiles, with IgE specific to several allergens and substructures now being suggested as markers of severity, persistence, or both. However, high-power quantitative studies with larger numbers of patients are required to confirm these markers. IgE-binding tests merely indicate sensitization, whereas the final proof of clinical relevance still relies on family/case history, physical examinations, and provocation tests. Novel technologies promise superior diagnostics. Microarray technology permits simultaneous measurement of multiple IgE reactivities regarding specificity, abundance, reactivity, or interaction. Improved functional tests might enable reliable estimation of the clinical relevance of IgE sensitizations at justifiable expenses.

IgE-mediated anaphylaxis to Thiomucase, a mucopolyssacharidase: allergens and cross-reactivity

BACKGROUND

Thiomucase is a mucopolysaccharidase obtained from ovine tissues mainly used to facilitate the diffusion of local anaesthetics and in the treatment of cellulitis. A patient with an anaphylaxis in relation to the intramuscular administration of Thiomucase is reported.

OBJECTIVE

To investigate Thiomucase allergens and their possible relationship with dander allergens and animal albumins.

MATERIAL AND METHODS

Skin prick tests (SPT) and serum-specific IgE were performed with Thiomucase and danders. Thiomucase SDS-PAGE immunoblotting was performed in order to study allergens. RAST/CAP inhibition and SDS-PAGE immunoblotting inhibition were carried out to study the cross-reactivity.

RESULTS

Skin prick tests (SPT) were positive to Thiomucase, animal dander (cat, dog, sheep, other), bovine serum albumin (BSA), and echinococcus. Specific IgE was also positive to Thiomucase, animal dander (cat, dog, sheep, other), BSA and echinococcus. In the RAST-CAP inhibition assays BSA was nearly completely inhibited by Thiomucase, Thiomucase was partially inhibited by BSA and cat and Echinococcus granulosus was partially inhibited by sheep and Thiomucase. In the Thiomucase SDS-PAGE immunoblotting several proteins fixed IgE, ranging from 20 kDa to > 94 kDa, the strongest with 43 kDa. The IgE fixation to BSA, cat and sheep in the SDS-PAGE immunoblotting was completely inhibited by the preincubation of the serum with Thiomucase.

CONCLUSIONS

An IgE-mediated anaphylaxis to Thiomucase is documented. Multiple allergens are recognized in Thiomucase by the patient serum, the main with 43 kDa. Partial cross-reactivity with BSA, cat dander and sheep dander is documented.

Allergy to iguana

BACKGROUND

Furry animals produce allergens that can cause allergic rhinitis and asthma. In contrast, scaly animals, such as lizards, are assumed not to be allergenic.

OBJECTIVE

We sought to evaluate a 32-year-old man who complained of allergic rhinitis and asthma symptoms that occurred exclusively in his own home. He had dogs and cats at home but denied any increase in symptoms specifically associated with these pets. Skin prick testing initially performed to 42 common aeroallergens, including cat, dog, and house dust mite, elicited negative results. He later reported that the symptoms were worse on exposure to his pet iguanas.

METHODS

Skin prick tests were subsequently performed to an extract made from scales from his pet iguana. Extracts were also prepared from several zoo reptiles. Immunoassays for IgE antibody, as well as IgE immunoblots, were performed by using these extracts and the patient's serum.

RESULTS

The skin prick test result with the pet iguana scale extract was positive. The patient's serum contained IgE antibody to his own pet iguana and to a zoo iguana.

CONCLUSION

Our patient's history, skin test results, and in vitro studies clearly demonstrate that he is allergic to iguana. Physicians should be aware that such allergy to scaly pets may occur and should not restrict history taking to questions about furry pets.

Allergy to lentils in Mediterranean pediatric patients

BACKGROUND

Peanuts and soybeans are the major legumes involved in human food allergy; however, scarce data exist on adverse reactions to other temperate legumes, such as lentils.

OBJECTIVE

The purpose of this study was to identify patients who are allergic to lentils, to assess clinical features and other associated food allergies, and to characterize allergens in lentil extract.

METHODS

Twenty-two children each with a history of adverse reactions to lentils were enrolled in the study. The diagnosis of lentil allergy was based on food challenges or a convincing history of anaphylaxis, with positive skin tests and/or specific serum IgE to lentils. Lentil components were characterized by SDS-PAGE immunoblotting.

RESULTS

Twenty of 22 subjects had symptomatic allergy to lentils at the diagnostic time. The most frequent symptoms were oropharyngeal symptoms (40%) and acute urticaria (30%); 3 patients also reported symptoms when they were exposed to steam from cooked lentils. In 18 patients, symptoms after lentil ingestion started under 4 years of age (median, 2.7 years). Nine patients had allergic reactions to other legumes: chick peas (6 patients), peas (2 patients), and green beans (1 patient). Immunoblotting patterns obtained with patients' sera showed IgE-binding bands ranging from 14 to 84 kd. Five sera recognized 9 or more IgE-binding bands, and more than 50% of patients who were tested have specific IgE antibodies to 7 components in lentil extract.

CONCLUSION

Allergic reactions to lentils started early in life, usually below 4 years of age; oropharyngeal symptoms and acute urticaria were the most common symptoms through ingestion, and symptomatic reactivity to chick peas is frequently associated.

Occupational asthma caused by exposure to asparagus: detection of allergens by immunoblotting

BACKGROUND

Vegetables of the Liliaceae family, such as garlic or onion, have been reported to cause occupational asthma. However, there are few data on adverse reactions to asparagus. We evaluated the role of asparagus as a cause of asthma in a patient with respiratory symptoms occurring at work (horticulture) and studied relevant allergens.

METHODS

A 28-year-old man complained of rhinoconjunctivitis and asthma when harvesting asparagus at work. Eating cooked asparagus did not provoke symptoms. A positive skin test reaction was observed with raw asparagus, Alternaria alternata, and grass-pollen extracts. The methacholine test demonstrated mild bronchial hyperresponsiveness. The patient had an immediate asthmatic response after challenge with raw asparagus extract. Bronchial provocation tests with boiled asparagus, A. alternata, and control extracts were negative. Two unexposed subjects with seasonal allergic asthma did not react to the raw asparagus extract.

RESULTS

The double-blind, placebo-controlled food challenge with raw asparagus was negative. Serum asparagus-specific IgE was 13.9 kU(A)/l. By SDS-PAGE immunoblot, at least six IgE-binding components, ranging from 22 to 73 kDa, were detected only in raw asparagus.

CONCLUSIONS

We report a case of occupational asthma caused by asparagus inhalation, confirmed by specific bronchoprovocation. Immunoblot analysis showed that asparagus allergens are very labile and quite sensitive to heat denaturation.

Cross-reactivity between IgE-binding proteins from Anisakis, German cockroach, and chironomids

Anisakis simplex larvae parasitize animals used as seafood and can produce a specific immune response in man. The ingestion of seafood contaminated with stage three of A. simplex larvae can induce a specific IgE response with clinical symptoms, usually urticaria, even if the fish is cooked before ingestion and the invasive infestation power destroyed by heating. Our preliminary studies showed a strong association of A. simplex sensitization with Ascaris lumbricoides, Daphnia, chironomid spp., Atlantic shrimp (Pandalus borealis), and German cockroach (Blattella germanica). We conducted the cross-reactivity study with cockroach, a ubiquitous insect, and Chironomidae (red mosquito larvae), a work-related allergen, without any possibility of Anisakis contamination. Serum samples were collected from 60 pediatric patients, with serum specific IgE to A. simplex. Both specific-IgE and immunoblot-inhibition studies, with a serum pool from 18 patients, were performed to determine whether the association of sensitizations to nematodes and arthropods was due to immunologic cross-reactivity. In addition, serum samples from 21 of 60 patients who showed also sensitization to German cockroach were used for individual immunoblot studies. In the serum pool, dose-dependent inhibition of B. germanica and Chironomus spp, was observed after preincubation with the A. simplex extract. Immunoblot of Anisakis, inhibited with Chironomus and German cockroach, yielded a partial blot inhibition but mainly on bands below 41 kDa. Blot inhibition of German cockroach and Chironomus with Anisakis was dose related. The band patterns in individual blots were heterogeneous, but most of them had bands of 30-43 kDa. None of these sera recognized allergens in the 14-kDa area. In our study, CAP-inhibition and immunoblot-inhibition analysis of Anisakis showed that several IgE-binding components could be shared by the three allergens.

Identification and characterization of wheat grain albumin/globulin allergens

Bakers' asthma, an immediate-type allergic response to the inhalation of cereal flours, is an important occupational disease among workers of the baking and milling industries, and the salt-soluble proteins of wheat and rye flour dust are considered the most relevant allergens. In order to identify and characterize the major IgE-binding proteins, the polypeptide composition of the albumin/globulin protein fraction obtained from different cultivars was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and high-resolution two-dimensional polyacrylamide gel electrophoresis with immobilized pH gradients in the first dimension (IPG-Dalt), followed by immunoblotting with sera from asthmatic bakers. Relevant allergens were isolated by micropreparative IPG-Dalt and blotting onto polyvinylidenedifluoride membranes and identified by amino acid composition analysis or N-terminal amino acid sequence analysis. SDS-PAGE, IPG-Dalt, and immunoblotting demonstrated that the sera of the bakers allergic to flour contained IgE antibodies which bound to numerous albumin/globulin polypeptides in the 70, 55, 35, 26-28, and 14-18 kDa areas. More detailed investigations using IPG-Dalt revealed cultivar-specific differences in IgE-binding. It was also demonstrated that the majority of the allergens were not single polypeptide spots, but consisted of up to ten isoforms of similar molecular mass but different isoelectric points. Amino acid composition analysis and N-terminal amino acid sequence analysis, which were performed for nine allergens located in the 14-18, 26-28, and 35 kDa areas, revealed homologies to amylase/protease inhibitors, acyl-CoA oxidase and fructose-bisphosphate-aldolase from wheat, barley, maize, and rice, respectively.

IgE antibodies against midge and moth found in Japanese asthmatic subjects and comparison of allergenicity between these insects

The specific IgE antibodies to moth (Bombyx mori) and midge (Chironomus yoshimatsui) were measured by the Pharmacia CAP system in 51 house-dust-mite-sensitive asthma patients. None of these patients had definite histories of exposure to these insects or apparent evidence of insect-induced asthma symptoms. The RAST-inhibition assay was performed to investigate cross-allergenicity between these two insects. Furthermore, IgE immunoblotting was done to study the IgE-binding components in moth and midge extracts. Thirty (59%) of these patients showed positive IgE antibodies to moth, while 25 (49%) showed positive IgE antibodies to midge. Those frequencies of positivity were similar to that for Japanese cedar pollen, which is well known to cause allergy. A significant correlation (r = 0.863) was observed between IgE antibody titers of these two insects. The results from the RAST-inhibition assay indicated cross-allergenicity between these insects and also the existence of species-specific allergens. Fifteen IgE-binding components in moth extract were observed. The most frequent IgE-binding protein was the 79-kDa (84.2%), followed by the 72-kDa (78.9%), the 82-kDa (57.9%), and the 76-kDa (57.9%) proteins. Those were considered to be major allergens in moth. Twenty-four IgE-binding components in midge extract were observed. However, no IgE-binding protein to which over 50% of patient sera reacted was observed. These results suggest that these two insects may be considered to bear important allergens and that there is cross-allergenicity between these insects as well as species-specific allergens.

Monospecific allergy to swordfish

BACKGROUND

Fish allergy is a relatively common and potentially fatal condition. Most fish allergic subjects are allergic to multiple fish species. We encountered a patient clinically allergic only to swordfish.

OBJECTIVE

To characterize the in vivo and in vitro IgE antibody responsiveness of this patient solely allergic to swordfish.

METHODS

Prick skin tests, as well as immunoassay and protein immunoblotting for IgE antibody were performed using commercial fish extracts and fresh swordfish. A more typical multiple fish-allergic subject and a subject not allergic to food were also studied for comparison.

RESULTS

The multiple fish-allergic subject demonstrated IgE antibody to a 13-kD protein in all fish tested (probably Gad c 1 and its analogues in other fish). The swordfish-allergic subject did not recognize this 13-kD band but did demonstrate IgE directed against a 25-kD band only in swordfish. The negative control showed no IgE binding to either the 13 or 25 kD bands.

CONCLUSIONS

It is possible to be allergic to a single fish species, such as swordfish, and such monospecific allergy may be due to the presence of species-specific allergens, in this case a 25-kD allergen in swordfish.

Cross-reactivity of IgE-binding components between boiled Atlantic shrimp and German cockroach

IgE-antibody reactivity to boiled Atlantic shrimp (Pandalus borealis) and German cockroach (Blattella germanica) of sera from 89 patients, sensitive to one or the other, was investigated with an enzymatic immunoassay for specific IgE detection (CAP-FEIA System, Pharmacia, Sweden). IgE serum levels to both antishrimp and anticockroach allergens were found to be positive in 76 of the 89 (85.4%) tested sera. A positive anticockroach IgE was very rare in the absence of detectable antishrimp IgE (five of 89 sera). Linear regression analysis on antishrimp and anti-German cockroach IgE levels-log plot revealed a correlation coefficient (r) of 0.73. Inhibition experiments showed that boiled Atlantic shrimp extract inhibited CAP with German cockroach, and vice versa. Immunoblotting showed the strongest IgE binding for both allergenic extracts between 30 and 43 kDa. By blot inhibition, the binding capacity of German cockroach was totally abolished by Atlantic shrimp extract, while German cockroach extract only partially IgE binding to Atlantic shrimp. Cross-reactivity exists between shrimp, an important food allergen, and German cockroach, which has an increasing role in allergic asthma. It could be important to determine the clinical significance of cross-allergy to both allergens, in which exposures occur in different ways.

Epitope specificity of the major peanut allergen, Ara h II

The antigenic and allergenic structure of Ara h II, a major allergen of peanuts, was investigated with the use of four monoclonal antibodies obtained from BALB/c mice immunized with purified Ara h II. Our previous studies with monoclonal antibodies generated to peanut allergens showed this method to be useful for epitope mapping. When used as a solid phase in an ELISA, these monoclonal antibodies captured peanut antigen, which bound human IgE from patients with positive peanut challenge responses. The Ara h II monoclonal antibodies were found to be specific for peanut antigens when binding for other legumes was examined. In ELISA inhibition studies with the monoclonal antibodies, we identified two different antigenic sites on Ara h II. In similar studies with pooled human IgE serum from patients with positive challenge responses to peanuts, we identified two closely related IgE-binding epitopes. These characterized monoclonal antibodies to Ara h II will be useful for future studies to immunoaffinity purify the Ara h II allergen and to use in conjunction with recombinant technology for determining structure-function relationships.

Electrophoretic characterization of wheat grain allergens from different cultivars involved in bakers' asthma

In order to identify and characterize the wheat grain allergens involved in bakers' asthma, proteins were sequentially extracted from whole-meal flour. The polypeptide composition of the individual solubility fractions (albumin/globulin, gliadin and glutenin) was analyzed by sodium dodecyl sulfate-gel electrophoresis (SDS-PAGE), and high-resolution two-dimensional gel electrophoresis with immobilized pH gradient 4-9 in the first dimension (IPG-Dalt). The resolved polypeptides were transferred onto an immobilizing polyvinylidene difluoride membrane and incubated with a pooled serum from four asthmatic bakers. Bound IgE was demonstrated by autoradiography using 125I-labeled anti-human IgE. Our study demonstrated that the serum of the bakers allergic to flour contained IgE antibodies which bound to numerous polypeptides of all three solubility fractions. The highest percentage of IgE binding was observed with certain albumin and/or globulin polypeptides, whereas the gliadins and glutenins exhibited considerably less allergenicity. SDS-PAGE revealed that the protein which bound the highest percentage of IgE from the sera of the allergic bakers is a 27 kDa albumin. More detailed investigations using IPG-Dalt demonstrated that this allergen is not a single polypeptide but consists of several polypeptide spots that differ in their isoelectric points. Quantitative studies using computer-assisted laser densitometry revealed that the amount of patients' IgE bound by these particular polypeptides differed considerably between the seven wheat cultivars examined, ranging from 13% to 53% of the total radioactive uptake.

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.

Anaphylaxis to measles, mumps, and rubella vaccine mediated by IgE to gelatin

BACKGROUND

Allergic reactions to measles, mumps, and rubella (MMR) vaccine are rare; some have been attributed to allergy to trace quantities of egg proteins. We report a 17-year-old female who had an anaphylactic reaction to MMR vaccine. A primary vaccination with MMR at age 15 months had been uneventful. She is not allergic to eggs; however, ear and throat pruritus and tongue swelling develop after she eats gelatin. MMR vaccine contains gelatin as a stabilizer.

METHODS AND RESULTS

Prick skin tests were positive to 1:10 wt/vol dilutions of MMR vaccine and gelatin but negative to egg. By immunoassay, her serum IgE antibodies were elevated to both MMR vaccine and gelatin, but not to isolated MMR antigens. IgE binding to the gelatin carrier could be inhibited in a dose-dependent fashion by addition of not only MMR vaccine but also gelatin from a variety of animal sources. Immunoblotting confirmed the presence of IgE antibodies to multiple gelatin components as well as to MMR vaccine components.

CONCLUSIONS

We conclude that the patient has an anaphylactic sensitivity to gelatin, and that her anaphylaxis to MMR vaccine was caused by the gelatin component. This sensitivity may explain other cases of MMR anaphylaxis.

Identification of host-protective antigens of Taenia ovis oncospheres

Sheep were fully protected against challenge infection following immunization with a homogenate of T. ovis oncospheres. Ultracentrifugation of sonicated oncospheres either alone or in the presence of a range of detergents did not reduce the immunogenicity of the extracts. Solubilization of oncosphere extracts in non-ionic detergents or sodium dodecyl sulphate (SDS) enabled analysis of host-protective antigens by isoelectric focusing (IEF) and electrophoresis in polyacrylamide gels (SDS-PAGE), respectively. Immunoblotting analysis of oncosphere antigens with immune sheep sera identified predominantly two groups of antigens with relative mobilities of 31-34 kDa and 47-52 kDa with a common isoelectric point of 5.8. The immunogenicity of these antigens was confirmed in vaccination trials using appropriate fractions cut from SDS-PAGE gels and agarose IEF gels. Affinity-purified antibodies prepared against the candidate antigens were used to select the corresponding recombinant DNA-derived polypeptides, one of which was subsequently found to be host-protective.

Identification and characterization of a second major peanut allergen, Ara h II, with use of the sera of patients with atopic dermatitis and positive peanut challenge

Peanuts are frequently a cause of food hypersensitivity reactions in children. Serum from nine patients with atopic dermatitis and a positive double-blind, placebo-controlled, food challenge to peanut were used in the process of identification and purification of the peanut allergens. Identification of a second major peanut allergen was accomplished with use of various biochemical and molecular techniques. Anion exchange chromatography of the crude peanut extract produced several fractions that bound IgE from the serum of the patient pool with positive challenges. By measuring antipeanut specific IgE and by IgE-specific immunoblotting we have identified an allergic component that has two closely migrating bands with a mean molecular weight of 17 kd. Two-dimensional gel electrophoresis of this fraction revealed it to have a mean isoelectric point of 5.2. According to allergen nomenclature of the IUIS Subcommittee for Allergen Nomenclature this allergen is designated, Ara h II (Arachis hypogaea).

The antigenicity and allergenicity of microparticulated proteins: Simplesse

New technologies are allowing the food industry to develop products from standard foods which may not be recognized in its modified form by food allergic patients. One such product, Simplesse, has been formulated by microparticulation of egg white and/or cows' milk proteins and is used as a fat substitute in many fat-laden foods. The purpose of this study was to determine whether the process of microparticulation altered the allergenicity/antigenicity of egg white and cows' milk proteins compared to the starting materials. Soluble protein fractions of Simplesse and its respective starting materials were compared to egg white, cows' milk protein, an ultra-filtered egg white/condensed milk mixture, and/or a whey concentrate by SDS-polyacrylamide gel electrophoresis. In addition, sera from 16 patients with documented egg and/or cows' milk hypersensitivity and two controls who were not allergic to egg or milk were used to assess potential allergenicity/antigenicity of these products by immunoblot (Western blot) analysis. There were heterogeneous IgE and IgG binding patterns to the food fractions among these food allergic patients suggesting differing sensitivity patterns among the individuals tested. However, utilizing both SDS-PAGE and immunoblot analyses, the major allergens in the microparticulated products were the same as those found in the starting materials, egg and cows' milk. In addition, there was no evidence of 'novel' protein fractions in the Simplesse test materials compared to the starting materials.

Detection of allergens in a cat pelt extract

Allergenic components of cat pelt extract fractionated by SDS-polyacrylamide gel electrophoresis (PAGE) and transferred to nitrocellulose membranes were identified using sera from 15 allergic patients who showed positive skin test and RAST to cat extract. Two components showed the highest IgE-binding frequency; 14 kD (being recognized by 86% of the sera examined) and 29 kD (73% of the sera tested). Both components were purified by electroelution and subjected to RAST inhibition assays. The 29 kD fraction was able to bind specific IgE to D. pteronyssinus and inhibited a RAST assay of 29 kD component (Der p I) purified from a D. pteronyssinus extract. These results could explain the finding of positive skin test with some commercial cat allergen solutions in patients with D. pteronyssinus allergy.

Identification and characterization of important allergens from mugwort pollen by IEF, SDS-PAGE and immunoblotting

Mugwort (Artemisia vulgaris L.) pollen allergens, separated by SDS-PAGE or IEF, were identified after transfer to NCM by incubation with a panel of sera from 16 patients with clinical mugwort pollen allergy, followed by [125I]anti-IgE and autoradiography. Of the at least 23 components separated by SDS-PAGE in a 15% polyacrylamide gel, at least 15 components with mol. wts 12,000-100,000 bound IgE from the panel of patient sera. A component of mol. wt 22,000 bound IgE from at least 94% of the patient sera tested and for all but three sera this component also bound the greatest quantity of IgE. Five other components with mol. wts 12,000, 17,000, 29,000, 39,000 and 42,000 bound IgE from 75-94% of the patient sera. After separation by IEF, at least 28 protein bands were detected in the pI region 3.5-7.2 and at least seven bands were found in the region 8.6-9.3. At least 11 bands in the pI range 4.2-7.3 and at least five bands in the pI region 8.5-9.2 bound IgE from the panel of patient sera. The most intense radiostaining was observed with a component having a pI of 4.35, which bound IgE from 31% of the patient sera. Immunoblotting of the SDS-PAGE and IEF gels using specific rabbit antisera and human sera against three important mugwort pollen allergens, denoted Ag 9, Ag 12 and Ag 13, was performed to determine the mol. wt and pI of these allergens which had earlier only been identified in CIE/CRIE. The results revealed that Ag 13 had a mol. wt of 61,000 and a pI of 4.35, Ag 12 had a mol. wt of 22,000 and AG 9 had pIs in the region 4.55-5.55 (six isoforms). Ag 9 did not bind IgE after SDS-PAGE and was thus not identified in the SDS-PAGE pattern, and Ag 12 failed to be detected in the NCM after transfer from IEF gels. By crossed immunoelectrofocusing, Ag 12 was found to consist of several isoforms predominantly located in the pI region 3.5-5.1. The immunoblotting analysis also revealed that the glycoprotein allergen Art v II was not detected after transfer from either SDS-PAGE or IEF gels. In conclusion, immunoblotting analysis of SDS-PAGE and IEF gels are useful methods for characterization of mugwort pollen extract, but it should be noted that some important allergens which are easily identified in CIE/CRIE may fail to be detected by these methods.

Identification of jack-jumper ant (Myrmecia pilosula) venom allergens

Jack-jumper ant venom proteins were electrophoretically separated on SDS-polyacrylamide gels, transferred to nitrocellulose and probed with sera from subjects who had experienced an allergic reaction after being bitten by a jack-jumper ant. Ant venom components that bound IgE antibodies were detected by addition of 125I-anti-human IgE followed by autoradiography. Of the 17 polypeptides resolved by electrophoresis only three, of molecular weights approximately 14 kD, 12 kD and 10 kD, bound IgE antibodies from the panel of 50 sera examined. There was a marked similarity in the binding patterns by individual sera with almost all of the sera recognizing the 14kD and 12 kD components. IgE-binding profiles of separated ant venoms from ants collected in different regions of Australia appeared to be very similar if not identical. Identification of the ant allergens is a necessary prelude to the preparation of standardized venom sac extracts suitable for safe and effective diagnostic and therapeutic use.

Methodological considerations when using nitrocellulose immunoblotting from polyacrylamide gels to study the mould allergens Aspergillus fumigatus and Alternaria alternata

The effects of sample treatments, separation conditions, and the possible presence of antibody interference phenomena in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) followed by nitrocellulose immunoblotting (IB) were studied using allergens from Alternaria alternata (Alt.a.) and Aspergillus fumigatus (Asp.f.) as model systems. In order to obtain good resolution in the IB method the mould allergens were separated in gradient gels under dissociating conditions (SDSgPAGE) including sample treatment with boiling, SDS and 2-mercaptoethanol (ME). These treatments all reduced the IgE binding capacities of the Asp.f. and Alt.a. extracts studied. Nevertheless, a great variety of IgE-binding components were detected after IB, and this could probably be explained by refolding of allergens during the blotting procedure where SDS was partly removed. A comparison of IgG-enriched and IgG-reduced serum fractions in IB revealed small differences in the IgE-binding patterns suggesting that IgG interference is of minor importance in the system studied. The IB method must be individually optimized for each new allergen studied using well characterized sera, preferably monospecific for the major components. Taking these facts into consideration, the IB technique is a valuable complement to other methods in the study of mould allergens.

Cellular localization of water soluble, allergenic proteins in rye-grass (Lolium perenne) pollen using monoclonal and specific IgE antibodies with immunogold probes

A postembedding method has been developed for localizing water soluble allergens in rye-grass pollen. This uses dry fixation in glutaraldehyde vapour, followed by 2,2-dimethoxypropane, prior to a 100% ethanol series leading into embedment in LR Gold. This has allowed the attachment of specific monoclonal antibodies to the allergen, which are themselves probed with specific immunogold labels to the antibodies. Wall and cytoplasmic sites have been identified, representing an improvement of fixation and localization of allergens over previous studies employing polyclonal, broad spectrum antibodies. Rye-grass allergens are labelled in mature pollen grains in the exine (tectum, nexine and central chamber), and in the electron opaque areas of the cytoplasm, especially mitochondria. The allergens are absent from the intine, polysaccharide (P) particles, amyloplasts, Golgi bodies and endoplasmic reticulum. IgE antibodies derived from humans allergic to rye-grass pollen, bind to similar sites in the cytoplasm but only to the outer surface of the pollen grain wall. This method now provides a valuable tool for further developmental studies on the pollen grains, in order to establish the site/s of synthesis of the allergens.

Members of the alpha-amylase inhibitors family from wheat endosperm are major allergens associated with baker's asthma

We have identified the major antigens or IgE binding components from wheat flour. Thirty-five sera from patients with baker's asthma were used to analyze the reaction with wheat salt-soluble proteins. We found a 15 kDa SDS-PAGE band which reacted with all sera tested. Purified members of the alpha-amylase inhibitor family, which are the main components of the 15 kDa band, were recognized by specific IgE when tested with a pool of reactive sera. Immunodetection after two-dimensional electrophoretic fractionation of crude inhibitor preparations from wheat endosperms also detected several inhibitor subunits as major low-molecular-weight allergens.

Analysis of the individual allergens of Russian thistle pollen by an enzyme-linked immunoblotting technique

Russian thistle pollen extract was analyzed by immunoblots of isoelectric focused and SDS-PAGE gels. Twenty distinct protein bands were recognized by human IgE- and IgG-specific antibodies in the immunoblot from the SDS-PAGE gel. Molecular weights of these allergens ranged from 12.2 kD to 85 kD. Seventeen bands were detected on isoelectric focusing immunoblots with pI from 3.95 to 7.70. Allergic subjects had differing individual patterns of protein band recognition. Immunoblot techniques provide detailed evaluations of the response of allergy subjects to components of crude natural allergens.

Allergens of the imported fire ant

A whole body extact (WBE) was prepared by saline extraction of ground imported fire ants (IFA). A serum pool from rabbits immunized with the WBE elicited 31 precipitates on crossed immunoelectrophoresis. Crossed radioimmunoelectrophoresis was performed with sera from 26 RAST IFA-positive subjects, 24 of whom were known for clinical hypersensitivity to IFA and two subjects, known to be hypersensitive to yellow jacket. Radiostaining was obtained to 14 precipitates, some of which were judged to be partially identical. Thus, six apparently different allergen groups could be identified. Two of these fulfilled arbitrary criteria of major allergens. Three of the IFA WBE allergens were easily identified in crossed immunoelectrophoresis of a commercially obtained IFA-venom preparation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the IFA WBE demonstrated protein bands with molecular weight ranging from 10,000 to 200,000 daltons. An immunoblotting technique with nitrocellulose paper strips revealed binding of human IgE from hypersensitive subjects to four different bands (either single bands or clusters of proteins of similar molecular weight) with molecular weights ranging from 13,000 to 42,000 daltons. It is a notable finding that these insect allergens thus were of a similar size as important aeroallergens.

Immunoblotting from immobilized pH gradients. The case of alpha 2-macroglobulin

Guidelines for effective blotting of proteins from immobilized pH gradients with a soft polyacrylamide matrix (e.g. T% = 3) include: thick (1 mm) IPG slabs, electrotransfer in a buffer tank in the presence of 0.1% SDS, nitrocellulose of the sturdiest type, thorough removal of all IPG fragments before further processing of the membrane. For alpha 2-M, IPG on a 4-6.5 gradient followed by enzyme-linked immunodetection allows the recognition of a complex pattern with several bands centered around pI 5.1. The procedure may also reveal the desialylated forms of alpha 2-M (microheterogeneity reduced to 2-3 bands), the native subunits (after reduction with thiols) and the denatured half molecules (in the presence of 8 M urea).

Immunoperoxidase localization of apolipoprotein D in human enterocytes and hepatocytes

In this study we prepared a pure apolipoprotein D and obtained a specific antiserum to it. The purified apolipoprotein D migrated as a single band of Mr = 29,000 but appeared as five isoforms on isoelectrofocusing. The antiserum did not cross-react with other apolipoproteins. Immunoenzymatic staining revealed the presence of apolipoprotein D in the perinuclear area of the cytoplasm of isolated normal hepatocytes and HepG2 cells. Apolipoprotein D was also localized in intestinal epithelium and in liver cells. The intracellular distribution of apolipoprotein D was similar to that of apolipoprotein B. Our results indicated that apolipoprotein D, like many other circulating apolipoproteins, is synthesized in enterocytes and hepatocytes.

Olive (Olea europea) pollen allergens--I. Immunochemical characterization by immunoblotting, CRIE and immunodetection by a monoclonal antibody

The pattern of reactivity of the Olea europea crude extract antigens was analysed after electroblotting to nitrocellulose from SDS-PAGE. The antigens contained in the 17, 19 and 42 K bands were most reactive with specific IgE from individual sera. Following immunization with a crude extract, one monoclonal antibody (OL-1) was raised against components which exhibited IgE binding capacity in electroblotting and crossed radioimmunoelectrophoresis (CRIE). Monoclonal antibody OL-1 reacted with the 17 and 19 K antigens and with three arcs of crossed immunoelectrophoresis (CIE), one of which is considered to contain a major allergen by CRIE.

Comparative studies on tree pollen allergens. XII. Evaluation of direct and indirect autoradiography systems for 125I in crossed radioimmunoelectrophoresis and other immunoautoradiographic techniques

Visualization by autoradiography of specific IgE binding in crossed radioimmunoelectrophoresis (CRIE) and other 125I-immunoautoradiography (IAR) techniques is done in two different ways; either by traditional direct autoradiography (D-ARG), where the film is exposed to the 125I-anti-IgE incubated sample at room temperature, or by indirect autoradiography (ID-ARG), applying intensifying screen, low-temperature exposure and, eventually, pre-exposure. This study confirmed that D-ARG provided the benefits of simplicity and better image resolution with the disadvantage of prolonged exposure periods. ID-ARG reduced the exposures needed to produce film image densities of 0.01 and 0.1 A540 nm (i.e. autoradiographic sensitivity (AR sigma) and autoradiographic speed (ARs] to 1/18 and 1/55 respectively of the corresponding exposures in D-ARG. The lowest detection limits for 125I in 24 h were 1.2 cpm mm-2 with the indirect and 6.8 cpm mm-2 with the direct systems investigated. The major drawbacks of ID-ARG were inferior image resolution and higher background levels, especially when pre-exposure was included.

Protein blotting on nitrocellulose: some important aspects of the resolution and detection of antigens in complex extracts

The resolution and detection of individual components in complex extracts by protein blotting have been investigated. By probing nitrocellulose transfers with monospecific and multispecific antisera, it was demonstrated that dissociating conditions were required for the maximum resolution of antigens by polyacrylamide gel electrophoresis, a conclusion reinforced by results from 2-D electrophoresis. The dissociating and reducing treatments employed, however, were both shown to be responsible for some loss of total antigenicity and included the complete loss of at least one important antigen. Assays with nitrocelluloses of different pore sizes demonstrated that both higher protein-binding capacities and higher backgrounds were associated with the use of the smallest pore size, while the sensitivity of the assay was greatest when a non-ionic detergent, and not proteins, were used for blocking. Nitrocellulose-bound proteins may be stained with amido black, India ink, toluidine blue, Ponceau S or a gold sol, but these agents do not always give identical staining patterns. While detection of components with immuno-enzyme staining methods had some advantages, problems with non-specific binding were encountered. These did not occur with affinity purified radiolabelled second antibodies, which in combination with scanning of autoradiographs allowed a quantitative approach to be adopted.

Quantitative immunoblotting assay of blood coagulation factor XII

The immunoblotting technique was applied to the study of Factor XII (F.XII) in plasma. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of whole plasma followed by electroblotting of the electropherograms to nitrocellulose (NC) membranes and immunologic detection by a double antibody technique was used. 125I-F.XII was transferred to the NC membrane in amounts proportional to the amount applied to the gel provided that a constant amount of carrier protein was present. Based on this, a quantitative assay was developed using either normal plasma or F.XII dilutions in F.XII-deficient plasma as standards. The measurement of F.XII antigen by immunoblotting was reproducible and gave values similar to those obtained by radial immunodiffusion. Two normal plasma pools contained 26 and 29 micrograms/ml of F.XII according to the immunoblotting assay. Compared to other immunoassays, immunoblotting has the advantage of directly estimating the apparent molecular weight (MW) of the protein of interest. Thus, we could confirm the normal apparent MW (80,000) of a F.XII-like molecule previously isolated from a cross reacting material (CRM)-positive F.XII-deficient plasma. None of eight CRM-negative F.XII-deficient plasmas showed an 80,000 MW immunoreactive molecule. However, five of these eight plasmas had a faint autoradiographic band at 115,000 MW that was similarly seen in only three out of 43 individual normal plasmas. The nature of this 115,000 MW band remains to be defined.

An analysis of class I antigens of man and other species by one-dimensional IEF and immunoblotting

A procedure for the molecular identification of MHC class I products based on 1-D IEF and subsequent immunoblotting is described. Optimal conditions for 1-D IEF, the electrophoretic transfer of proteins out of denaturing, nonionic detergent-containing gels to nitrocellulose, and the requisite antibodies, both polyclonal and monoclonal, for the visualization of class I heavy chains have been established. Cross-reactivity of antibodies has enabled the biochemical analysis of class I heavy chains in the dog. The procedure reported here requires modest amounts of cells and allows a rapid molecular characterization of class I heavy chain polymorphisms in man and other species without the need for radiochemical methods.

Physicochemical and immunochemical characterization of allergenic proteins from rye-grass (Lolium perenne) pollen prepared by a rapid and efficient purification method

Three fractions of rye-grass (Lolium perenne) pollen extract have been isolated by preparative isoelectric focusing (i.e.f.) and characterized in terms of physicochemical and immunochemical properties. The purified components were designated 'R7' and 'R14' on the basis of their positions in relation to other rye-grass pollen extract components on SDS/polyacrylamide-gel electrophoresis and their apparent molecular masses were assessed as 31 and 11 kDa respectively. On i.e.f., R14 split into two components, one acidic (pI 5.0) and one basic (pI 9.0), termed 'R14a' and 'R14b' respectively, and R7 focused at pI 5.8. R7 and R14a were shown to be allergenic by skin-prick test and all three components were recognized by rye-grass-pollen-specific human IgE. On SDS/polyacrylamide-gel electrophoresis and i.e.f., R7 behaved in a manner identical with that shown by an authentic sample of Rye I and gave an amino acid analysis similar to published data [Johnson & Marsh (1966) Immunochemistry 3, 91-100] for Rye group-I isoallergens; the amino acid sequence of the first 27 N-terminal amino acids was also determined. Physicochemical analysis revealed that R14a was equivalent to Rye II and 14b to Rye III. Preparative i.e.f. followed by gel-permeation chromatography proved to be a rapid and efficient method for purifying the allergenic components of Rye I (R7), Rye II (R14a) and Rye III (R14b) from rye-grass pollen extract.

Isolation of the major IgE-binding protein from Parietaria judaica pollen using monoclonal antibodies

Allergen molecules from Parietaria judaica pollen, a widely distributed allergy inducer in Southern and Western Europe, have been studied using specific monoclonal antibodies (MAbs). MAbs against IgE-binding components were selected in a 4-step radioimmunoassay. Three different MAbs (AC/1.1, AC/7.1 and AC/15.1) were obtained which recognized epitope(s) located on a polypeptide of 10 Kd (Pj10). This polypeptide displayed the highest IgE-binding ability under either native or SDS-denatured conditions, as determined by immunoadsorption and immunodetection after SDS-PAGE, respectively. The Pj10-containing allergen, purified on an AC/1.1 MAb-Sepharose column, was able to inhibit most of the binding of specific IgE to the pollen extract coupled to paper discs in an inhibition radioallergosorbent test (RAST). The affinity-purified allergen exhibited the same immunoelectrophoretic behaviour as the native allergen.

The immune response to herpes simplex virus: comparison of the specificity and relative titers of serum antibodies directed against viral polypeptides following primary herpes simplex virus type 1 infections

Employing an immunoblotting technique, the polypeptide specificity and relative titers of anti-HSV IgG reactive with denaturation-resistant epitopes on HSV proteins were determined in patients experiencing primary HSV-1 infections at various anatomical sites. Early sera from previously seronegative patients with primary HSV-1 infections were found to have comparatively low levels of antibody directed against the major viral glycoprotein antigens (gB, gC, and gD) relative to titers present in sera of individuals with long-standing, latent orofacial HSV-1 infections. Patients with primary infections did however have high titers of antibody directed against a series of low molecular weight HSV polypeptide antigens. These antigens were found to be antigenically related to a structural component of virion nucleocapsids. At later times postinfection, titers of antibodies directed against other viral polypeptides including the major glycoproteins increased to levels more closely approximating those observed in latently infected individuals. These results indicate that the anti-HSV IgG detected by immunoblot analysis which appears earliest following primary infection is not directed against the known major infected cell or virion glycoprotein surface antigens but rather against an internal capsid protein of HSV.

Purification and characterization of a specific antigen from Echinococcus multilocularis

A polypeptide (Em2a) purified by affinity chromatography from the Echinococcus multilocularis metacestode showed a high degree of purity as assayed by SDS-PAGE and analytical isoelectrical focusing. A minor contamination with host albumin was revealed. Estimation of relative mol. mass gave a value of 54,000. The isoelectric point was found to be 4.8. Antigenic activity of the polypeptide was demonstrated by immunoprecipitation and western blotting. In these assays the protein was recognized only by homologous sera from patients infected with larval E. multilocularis. This antigen (Em2a) did not react in the ELISA with sera from patients infected with heterologous helminths; these sera were highly cross-reacting with antigen from E. granulosus hydatid fluid. Seventy-three (94%) from 78 investigated patients (alveolar echinococcosis) showed a seropositive reaction with the polypeptide Em2a.

Isotachophoresis of allergenic extracts

One aspect of the isotachophoretic determination of protein patterns in biological samples of interest is the characterization of allergens. This group of (glyco) proteins, causing allergic reactions, is used both for diagnosis and in the treatment of allergy. The aim of this investigation was to obtain a maximum amount of information, within one run, on the (glyco)protein composition of a number of allergenic extracts (e.g., from pollen or house dust mites). Commercially available extracts were dialysed prior to analysis to remove disturbing buffer constituents. A high-pH system was chosen in order to obtain a maximum amount of information from the samples (1-2 microliter). The leading electrolyte was 0.01 M C1-, buffered with Tris (pH 8.2), containing 0.2% w/v hydroxyethylcellulose, and the terminating electrolyte was beta-alanine, buffered to pH 10 with Ba(OH)2. The total analysis time was 15-20 min using a PTFE capillary (0.2 mm I.D.). The pre-separation current was 30 microA and the current during detection was 15 microA. UV absorption was measured at 280 nm. For optimal discrimination of the compounds of interest, an ampholyte mixture was used for spacing. The analytical procedure yielded highly reproducible UV patterns. Significant differences between various allergenic extracts were observed. It was concluded that isotachophoresis is a powerful method for the physico-chemical characterization of individual allergenic extracts, e.g., with respect to manufacturing and quality control.

Auto- and iso-antigens of human spermatozoa detected by immunoblotting with human sera after SDS-PAGE

A sodium dodecylsulphate-polyacrylamide gel electrophoretic system for analysis of the proteins of human spermatozoa was established. Subsequent immunoblotting of the gels with human sera gave a reproducible immunolabelling of distinctive polypeptide bands. To identify auto- and isoantigens, 28 well-characterized sera from the WHO Reference Bank for Reproductive Immunology (1977, Acta Pathol. Microbiol. Scand. Sect. C, Suppl. 252) containing agglutinating and complement fixating antibodies (9 female (F) and 19 male (M) and 30 normal sera (14 F and 16 M) were analysed with reference to binding of IgG. Three spermatozoal antigens with Mr values in reduced state of 120,000 (6), 41,000 (6) and 32,000 (15) were found to be specifically correlated to the agglutinating activity of the reactive sea. (The number of these are given in parentheses). Furthermore, IgG from 2 and 3 of the normal sera and 14 and 17 of the agglutinating sera reacted with 78 and 64 kDA polypeptide, respectively. Identical binding patterns of IgG to spermatozoal polypeptides were obtained with IgG from male and female sera. The IgG-binding could not be correlated to the modes of spermatozoal agglutination. In a similar analysis of the IgM binding antigens of 21 agglutinating and 12 normal sera no differences in binding between the sera were found, except for a specific reaction to a 78 kDa antigen for 5 of the agglutinating sera.