Interference in ragweed pollen and honeybee venom radioallergosorbent tests

Detection of Allergen-Specific IgE Antibody Responses

Allergen-specific IgE production is the central event in the pathogenesis of atopic disorders and increases in specific IgE serum antibodies are an indicator of immediate hypersensitivity responses in humans and in animal models of allergy. Consequently, accurate and user-friendly methods are needed to measure serum levels of allergen-specific IgE. This review examines historical and recent developments in in vivo and in vitro methods for the detection of allergen-specific IgE in humans and in animal models. Routinely, in vitro methods such as enzyme-linked immunosorbant assays or radioallergosorbant tests and in vivo methods such as the skin prick test (SPT) for humans and the passive cutaneous anaphylaxis assay (PCA) used in animals are utilized to detect allergen-specific IgE. While in vivo assays are usually more accurate than in vitro assays since they provide a functional readout of IgE activity, they are relatively costly and require considerable expertise. On the other hand in vitro assays are limited by the fact that the amount of allergen-specific serum IgG exceeds IgE antibody by several orders of magnitude, resulting in competition for allergen binding. Consequently, methods that use allergen as a direct capture step are limited by the availability of free allergen binding sites for IgE. In order to circumvent this problem, in vitro methods usually require prior depletion of IgG or use high amounts of allergen in order to facilitate availability of free binding sites for IgE detection. Clearly, these approaches are limited for small sample volumes and allergens that are in short supply. New methods such as protein microarray could potentially overcome this problem by providing high allergen concentrations in a relatively small reaction volume. Currently, in vitro methods are rarely used in isolation for prognosis but are used primarily to complement the information obtained from in vivo assays. With the emergence of new technologies it is conceivable that in vitro assays may in the future replace in vivo assays, however until then in vivo assays remain the gold standard of allergen-specific IgE detection.

Detection of mosquito saliva-specific IgE antibodies by capture ELISA

We developed an IgE-capture ELISA and measured mosquito saliva-specific IgE antibodies in 27 children sensitive to mosquito bites. Children with large 15-min bite wheals had significantly higher (P < 0.0005) mosquito saliva-specific IgE levels than children with small wheals. In the latter group, the saliva-specific IgE level was significantly higher (P = 0.031) than the levels of six infants never exposed to mosquitoes. A positive correlation (r = 0.65; P = 0.0002) was found between the size of the 15-min wheal and the mosquito saliva-specific IgE antibody levels. These results further support the role of mosquito saliva-specific IgE antibodies in the pathogenesis of mosquito-bite whealing. Compared to immunoblotting, IgE-capture ELISA provides a quantitative method to measure mosquito saliva-specific IgE antibodies.

Dot immunobinding assay as a new diagnostic test for human hydatid disease

Bovine and human hydatid antigens collected from hepatic cysts and characterized by SDS-PAGE immunoblotting show similar patterns. The bovine hydatid antigen has been used to develop a simple and fast in vitro diagnostic assay for human hydatidosis. This method, named HA-DIA (hydatid antigen dot immunobinding assay), consists of incubation of a serum sample with a textile colloidal dye (pink) and a nitrocellulose stick to which the hydatid antigen has been bound. The presence of parasite-specific antibodies leads to dyeing of the stick reactive area, and a coloured spot appears. HA-DIA sensitivity and specificity have been studied in comparison with RAST-IgE and ELISA-IgG by testing 17 sera of patients with hydatid disease and 36 control sera from patients affected with other parasitic and non-parasitic diseases. HA-DIA showed positive results in all the patients' sera and in none of the control sera. Correlation with ELISA--IgG and RAST-IgE was significant. HA-DIA has been demonstrated to be of good predictive value, allowing a speedy diagnosis of hydatid disease. In view of its simplicity, not requiring any laboratory instruments, it is particularly suitable for large-scale field screening.

Causative allergens of allergic rhinitis in Japan with special reference to silkworm moth allergen

To determine the importance of silkworm moth allergens, we tested 267 patients with allergic rhinitis with CAP-RAST, a new assay system for detecting specific IgE in sera. We used the following allergen sources: house-dust mite, Candida, Alternaria, cat dander, orchard grass, ragweed, mugwort, Japanese hops, Japanese cedar, Japanese cypress, cotton, silk, larval chironomid midge, adult chironomid midge, and silkworm moth. As expected, the highest positive rate of reaction, as determined by CAP-RAST, was 73.8% for Japanese cedar, followed by 53.2% for mite and 50.6% for Japanese cypress. Although the positive rate for silkworm moth was not as high as for cedar pollen, one-third of patients had specific IgE against silkworm moth. The positive rate of reaction to silkworm moth was much higher than that to chironomid. It was interesting to note that the patients reported had not been documented as having frequent contact with silkworm moth allergen. Correlations between silkworm moth and silk, and silkworm moth and chironomid midge were found to be significant (P < 0.001). Silkworm moth allergen showed the third highest reaction rate in patients with severe symptoms. These results suggest that silkworm moth allergen should be considered to be important in patients with allergic rhinitis in Japan.

Evaluation of allergenic potency by REAST inhibition. A new tool for the standardization of allergenic extracts

The potency of allergenic extracts can be determined in vitro by RAST inhibition, and this has become the preferred method for the standardization of allergens. A disadvantage of this technique is the impossibility of obtaining data about allergens bound to the solid phase, i.e., the counterpart of the inhibiting extract. The REAST (reverse enzyme allergosorbent test) is based on the capture of IgE by a specific antibody bound to microtiter wells, the reaction of captured IgE with biotinylated allergen and the development of a colour reaction by subsequent addition of streptavidin-peroxidase and chromogenic substrate. The addition of an allergen extract in a dose-response fashion competes with the biotinylated allergen and inhibits the test. In the present study REAST inhibition has been evaluated with Dermatophagoides pteronyssinus, Parietaria judaica and mixed grass pollen extracts. The correlation of REAST inhibition with RAST inhibition and both intra-assay and inter-assay reproducibility have been evaluated. REAST inhibition is a potentially valuable new tool for the standardization of allergenic extracts.

Comparison of immunologic tests in the diagnosis of occupational asthma and rhinitis

In this study, three immunologic tests, skin prick test, RAST, and basophil histamine-release test (BHRT), were compared by provocation in the diagnosis of occupational asthma and rhinitis. Twenty-three positive bronchial or nasal challenges were performed on 16 patients (six farmers, six bakery workers, and four food industry workers) and asthma or rhinitis was diagnosed as caused by cereal flour or grain, cow epithelium, storage mites, garlic, or soy dust. A control group consisted of 12 patients, of whom four (two bakery workers, one food industry worker, and one farmer) were challenge-negative, and the rest suffered from pollen allergy and seasonal rhinitis and were not challenged. The sensitivity and specificity of the prick test, RAST, BHRT, and a panel of them were as follows: 74 and 89%, 57 and 86%, 78 and 93%, and 91 and 71%, respectively. The overall concordance among these three type I allergy tests or between immunologic tests and challenge was relatively good.

Strong serum inhibition of specific IgE correlated to competing IgG4, revealed by a new methodology in subjects from a S. mansoni endemic area

A method allowing the immunopurification of human IgE from small volumes of sera with a yield close to 100% (mean = 97.8%; SEM = 0.7) has been developed. The immunopurification eluates were cleared of other class antibodies that could compete with IgE in specific assays. Immunopurification of IgE followed by specific IgE enzyme-linked immunosorbent assay (ELISA) (IMMEL) was then applied to sera of 160 individuals from an area endemic for Schistosoma mansoni. In comparison with radioimmunosorbent test (RAST) and ELISA performed on unfractionated sera, IMMEL provided the highest specific IgE signals. Furthermore, the best correlations between the specific IgE levels and either the specific basophil histamine release levels (r = 0.84; p less than 10(-4) or the anti-S. mansoni skin test values (r = 0.45; p = 10(-4)) were obtained with IMMEL. Measurement of anti-S. mansoni IgE levels in immunopurified fractions and in unfractionated sera of these 160 individuals revealed a strong serum inhibition (geometric means of 98.6% and 96.8% for the adult worms and the larvae, respectively) of the specific IgE reactivity in ELISA. This inhibition was correlated with the anti-adult worm and anti-larval IgG4 levels (r = 0.65; p less than 10(-4) and r = 0.58; p less than 10(-4), respectively). In contrast, this inhibition did not correlate with the specific IgG1, IgG2, IgG3 and IgM levels. Furthermore, the level of specific IgG4 was clearly lower than that of specific IgG1, suggesting that the major contribution of IgG4 in the competition effect is not due to higher levels but rather to a specificity spectrum close to that of the specific IgE. These results support the idea that a specific function of IgG4 in serum might be to control antigen recognition by IgE and consequently, to regulate anaphylactic reactions and IgE-mediated immunity.

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.

Comparison between RAST and Pharmacia CAP system: a new automated specific IgE assay

RAST represents the standard technique to titrate serum-specific IgE and was found to have a higher efficiency in the diagnosis of IgE-mediated allergy than other in vitro tests. Pharmacia CAP system (CAP) is a new solid-phase immunoassay, fully automated, used for the titration of specific IgE antibodies. Results are listed in kilounits per liter, equilibrated against the World Health Organization standard for IgE. RAST and CAP were compared in 106 unselected patients (6 to 59 years) characterized by a detailed clinical history and skin prick tests with standardized allergen extracts. IgE to cat, Dermatophagoides pteronyssinus, Alternaria, orchard grass, olive, and Parietaria pollen were tested; 470 tests were run. The specificity, sensitivity, and efficiency of both in vitro tests ranged from 85.5% to 100% except for olive pollen, in which the sensitivity of both in vitro tests was low (68.2% for the new test and 63.6% for RAST). Except for orchard-grass pollen, the sensitivity and specificity of CAP were better than that of RAST. There was a highly significant correlation between both tests (r range, between 0.864 to 0.987). CAP competes favorably with RAST and has the advantage of being automated and eliciting results in kilounits per liter.

Human immune response to allergens of house dust mite, Dermatophagoides pteronyssinus. IV. Occurrence of natural autologous anti-idiotypic antibodies

IgG isolated from the plasma of seven individuals hypersensitive to the common house dust mite Dermatophagoides pteronyssinus (DPT) was exhaustively adsorbed onto insolubilized DPT. The unbound fraction was found by radioimmunoassay to contain antibodies recognizing the variable region of both anti-DPT IgG and IgE antibodies. This recognition was idiotype (Id)-specific as it persisted after passage over insolubilized polyclonal IgG of unrelated specificity. Most of these anti-Id IgG carried the internal image of the initial antigen in that they competitively inhibited the binding of anti-DPT antibodies to DPT. Immunoadsorption of anti-Id IgG onto insolubilized anti-DPT IgG antibodies from the same individual completely eliminated their reaction with anti-DPT IgG but not with anti-DPT IgE, suggesting that idiotopes included in the antigen-binding site of specific IgG and IgE antibodies were not identical. Anti-Id IgG recognizing idiotopes located outside the antigen-binding site (bystander idiotopes) were also completely removed by passage over insolubilized anti-DPT IgG; in this case the reaction of the anti-Id IgG with both anti-DPT IgG and anti-DPT IgE was inhibited, indicating that, for a given individual, bystander idiotopes were shared between anti-DPT antibodies pertaining to these two isotypes.

Immunotherapy with Hymenoptera venoms. Position paper of the Working Group on Immunotherapy of the European Academy of Allergy and Clinical Immunology

Immunotherapy with Hymenoptera venoms is widely used throughout the world and is accepted as an effective treatment for most patients with Hymenoptera venom allergy. There are, however, still some unresolved problems with this form of treatment. At present there is no definite test which makes it possible to identify patients at risk - and thus candidates for immunotherapy - unequivocally. On the basis of prospective studies on the natural history of Hymenoptera allergy, venom immunotherapy is indicated in adults with severe systemic anaphylaxis. It is usually not necessary in patients with large local reactions only. Children with mild systemic reactions, e.g. urticaria, will need immunotherapy only in case of repeated reactions and/or a high risk of re-exposure. The selection of venoms for immunotherapy may lead to some confusion owing to common antigenic determinants shared by venoms of various Hymenoptera species. Many different regimens for immunotherapy have been proposed. At present, the three main are: rush, stepwise or clustered and classical. The maintenance dose of 100 micrograms usually protects from life-threatening reactions. However, in some patients 200 micrograms are necessary for complete protection. The usual interval between maintenance injections is 4 to 6 weeks. In many patients a strong increase of venom specific serum IgG-antibodies usually parallels clinical protection induced by venom immunotherapy, although many exceptions have been reported. Allergic side effects of venom immunotherapy are not rare, especially with honey bee venom and during the initial phase of dose increase. The question of the duration of venom immunotherapy is handled differently: although some authors recommend treatment for life, most suggest treating patients until skin tests and RAST become negative.

Diagnosis of allergy: in vitro testing

Relatively few laboratory tests are of proven value in the differential diagnosis and management of allergic diseases. Immunoassays for IgE and for IgE antibodies are the mainstays. Measurement of IgE in serum is advocated as a first-order laboratory test in the differential diagnosis of allergic disease in children and adults. The usefulness of laboratory tests for IgE antibodies in serum, once a subject of debate in the clinical allergy literature, is now firmly established. Confusion, in respect to the use of these tests, is most evident in clinical situations which have been the subject of limited clinical investigation, e.g., the use of tests for IgE antibodies to screen for allergic disease, the indications for their use in patients treated with allergen immunotherapy, and the diagnostic specificity of IgE antibodies to foods as an indicator of food-induced allergic symptoms. Confusion is also apparent in the interpretation of borderline test results, i.e., results which may indicate the presence of low titers of IgE antibodies, and in defining the optimum format for reporting results to maximize the analytical sensitivity of the test method. This review addresses the ambiguities noted above in the interpretation of results. The paragraphs that follow also consider the possible uses of laboratory tests for inflammatory mediators of immediate hypersensitivity, for IgG antibodies to allergens, and of tests designed to evaluate the in vitro functions of lymphocytes in patients with allergic disease.

Standardization of house dust mite extracts. Liberation of allergenic and antigenic components in relation to extraction conditions

The spontaneous release of house dust mite components from cultures of Dermatophagoides pteronyssinus into slightly buffered water was studied against time, using both continuous and discontinuous extraction procedures. It was shown that proteins, carbohydrates, IgE binding components and precipitating antigenic components were rapidly released from the house dust mite cultures, reaching a maximal liberation within 1 h of extraction. Repeated extractions of house dust mite cultures (discontinuous extraction) showed an additional release of IgE components but the IgE binding potency declined after successive extractions, while showing increasing release of immunological inactive components. IgE binding to antigens immobilized to polystyrene surfaces (IgE-ELISA) appeared to be less sensitive compared with cyanogen-bromide activated discs (IgE-RAST). It was concluded that extraction procedures of house dust mite cultures with short incubation time of 1 h or less are to be preferred.

Dose response of IgE and IgG antibodies during ragweed immunotherapy

We studied the detailed dose-response relationship for ragweed (RW) antibody responses in 51 patients who received maximal-dose immunotherapy with crude RW extract. Serum RW-IgG and RW-IgE levels were determined by solid-phase radioimmunoassay at frequent intervals during initiation and maintenance of immunotherapy. Pretreatment RW-IgE ranged from 0.94 to 974 ng/ml (median 105); 45/51 patients had insignificant levels (less than 250 ng/ml) of RW-IgG. The maximal doses given ranged from 0.19 to 93.5 micrograms of RW antigen E per injection. All patients produced a significant IgG response (median peak 3462 ng/ml, range 689 to 24,395), and 46/51 had significant increases in IgE antibody (median peak 231 ng/ml, range 12 to 1528). A threshold dose was defined for each patient's IgG and IgE response as that dose level which initiated a persistent increment in immunoglobulin to greater than or equal to 25% of pretreatment levels. The median threshold dose for IgE was 0.13 micrograms of antigen E, which was achieved in a median time of 42 days. The threshold dose for IgG was significantly higher (median 0.56 micrograms of antigen E; p = 0.001) and occurred significantly later (median 79 days; p = 0.003). Despite variability over 3 orders of magnitude, the thresholds for IgE and IgG responses were significantly correlated for individual patients (r = 0.487; p = 0.002). The maximum RW-IgE response occurred in a median of 107 days, after which IgE antibodies declined in 46 of 49 patients. The maximal IgG response occurred significantly later (median 245 days; p less than 0.001) and then plateaued or declined modestly. The doses required to achieve maximal IgE and IgG responses were significantly correlated (r = 0.638; p less than 0.001). The maximum IgG response was positively correlated with the maximal dose of RW antigen E received (r = 0592; p less than 0.001). In 28 of the 51 patients, the incremental rise in total serum IgE was more than twice that observed for RW-IgE at the time of the maximum response, suggesting a nonspecific effect of RW immunotherapy on total serum IgE levels. This discrepancy could not be accounted for by environmental stimulation from other known allergens, as assessed by skin testing, or by pretreatment levels of RW-IgE or total IgE. These observations indicate that the human IgE antibody response during high-dose RW immunotherapy is more sensitive to both stimulation and suppression by continuous allergen administration than is the IgG response.(ABSTRACT TRUNCATED AT 400 WORDS)

Serological methods in the diagnosis and management of human allergic disease

The diagnosis and management of human allergic disease is aided by serological measurements involving the quantitation of total human serum IgE, allergen-specific IgE and allergen-specific IgG. Initially, a brief overview of immediate hypersensitivity reactions will be presented with a focus on the role of "reaginic" allergen-specific IgE antibody. The principles and design of immunoassay methods employed in the measurement of total serum IgE and allergen-specific human IgE will then be examined with a discussion of the pros and cons of different radioallergosorbent test (RAST) reporting schemes. Next, Hymenoptera venom will be used as a model allergen system for exploring the clinical utility, principles and design of immunoassays used to quantitate allergen-specific IgG antibody in human serum. Examples of the utility of specific IgG measurements will be provided with recent clinical data. Finally, an overview will be presented on more research-based techniques used in the study of human allergic responses such as cross-immunoelectrophoresis and immunoassays for leukotrienes, prostaglandins, platelet Factor 4 and cyclic AMP.

The development of negative skin tests in children treated with venom immunotherapy

Twenty-eight of 62 children (45%) with a history of sting-induced anaphylaxis and initially positive skin tests to venom(s) developed negative venom skin tests to one or more of the venoms used in their treatment after 3 yr or more of immunotherapy. Children who developed negative venom skin tests were less sensitive prior to treatment, as judged by venom skin tests and venom-specific IgE antibody determinations, than children who maintained positive venom skin tests. Levels of venom-specific IgE antibodies declined with time in most children, but to lower levels in those with negative skin tests. Venom-specific IgG antibody levels were similar in both patients with negative skin tests and those with persistently positive skin tests. The development of negative skin tests may reflect a loss of allergic sensitivity, which is sufficient to allow the physician to consider the discontinuation of venom injections.

A solid-phase bead radioimmunoassay for specific IgE to ragweed antigen E

A solid-phase bead radioimmunoassay has been developed for measuring IgE against antigen E (IgE-a-AgE) in serum. The patient's IgE is bound by monoclonal mouse anti-human IgE which is on the surface of a solid bead. Other immunoglobulin classes are not bound and can be washed away. Radiolabeled AgE is then added and is specifically bound by IgE-a-AgE. This assay is reproducible, and in contrast to specific IgE assays utilizing RAST methodology, it cannot be inhibited by specific antibody of other classes. Moreover, the solid-phase bead method does not utilize myeloma IgE. Finally, its results correlate well with those of a previously developed polystyrene tube method.

Clinical and immunological surveys in bee keepers

Two hundred and fifty bee keepers in the South of France, working seasonally, were clinically investigated by means of a questionnaire. Forty-three per cent had presented anaphylactic symptoms and 7.0% toxic reactions when stung by bees. The personal atopic history was found to be significantly (P less than 0.01) elevated in bee keepers who experienced anaphylaxis. Total serum IgE and been venom-specific IgE were titrated in 100 subjects. Total serum IgE was significantly elevated in allergic bee keepers (P = 0.02). Although bee venom-specific IgE were significantly (P less than 0.01) higher in allergic bee keepers this parameter cannot discriminate between allergic and non-allergic bee keepers owing to a considerable overlap. Bee venom-specific IgG was assayed in seventy subjects. Their level was significantly (P less than 0.001) higher in allergic and non-allergic bee keepers as compared with non-allergic blood donors and non-bee-keeping allergic patients. In both bee keeper groups there was no difference in bee venom-specific IgG titres.

Increase of lymphocytes with Fc receptors for IgE in patients with allergic rhinitis during the grass pollen season

Peripheral blood lymphocytes from 10 nonallergic donors and 7 patients suffering from seasonal allergic rhinitis and receiving desensitization therapy were analyzed by rosette assays for Fc receptors for IgE (Fc epsilon R) and IgG (Fc gamma R) before, during and after the grass pollen season. Six of seven patients had moderately elevated IgE levels (330 +/- 268 IU/ml), all had high titers of skin sensitizing antibodies to grass pollens and serum IgE antibodies as measured by radio-allergosorbent tests (RAST). Seven of the nonallergic donors had 2-30 IU/ml IgE and negative RAST, whereas three had 91-267 IU/ml IgE and two were RAST positive to the grass pollens. In March, when the patients were asymptomatic, the mean +/-SD of the Fc epsilon R+ lymphocytes did not significantly differ from the nonallergic control group: nonallergic Fc epsilon R+ 1.2 +/- 0.9% (29 +/- 20/,mm3), allergic Fc epsilon R+ 2.0 +/- 3.1% (48 +/- 52/mm3). In contrast, during the grass pollen season in May and June, when the patients developed symptoms of allergic rhinitis, they had significantly (P less than 0.01) more Fc epsilon R+ lymphocytes than the controls: nonallergic Fc epsilon R+ 1.7 +/- 1.9% (40 +/- 46/mm3), allergic Fc epsilon R+ 4.7 +/- 1.2% (134 +/- 69/mm3). In the postpollen period, August-October, most of the patients again had low numbers of Fc epsilon R+ lymphocytes: nonallergic Fc epsilon R+ 1.4 +/- 0.9% (26 +/- 13/mm3), allergic Fc epsilon R+ 2.1 +/- 1.9% (62 +/- 82/mm3). The nonallergic control donors with elevated IgE levels and positive RAST always had low numbers of Fc epsilon R+ lymphocytes. In contrast, two other nonallergic donors, who had a 2-7 IU/ml IgE and negative RAST, showed significant increases of Fc epsilon R+ lymphocytes over several weeks during the grass pollen season. No statistically significant changes in Fc gamma R+ lymphocytes occurred in both nonallergic and allergic donors. The total and specific IgE serum levels did not vary much in the nonallergic donors and patients during the period of study and any changes that did occur did not correlate with the changes in Fc epsilon R+ lymphocytes. The data demonstrate that Fc epsilon R+ peripheral blood lymphocytes increase in allergic patients during natural antigen exposure and active disease in the absence of measurable increases of total and specific serum IgE. Because two nonallergic control donors also had temporary increases of Fc epsilon R+ lymphocytes, an increase of peripheral blood Fc epsilon R+ lymphocytes may be a sensitive indicator of an ongoing IgE immune response.