Direct Skin Tests Research Articles

Empowering Pediatricians With Direct Penicillin Challenges: A Promising Delabeling Strategy.

Current literature supports a multidisciplinary approach to penicillin allergy delabeling. Our study aims to review the success rate of penicillin challenges performed at Walter Reed National Military Medical Center Allergy Clinic and assess the reaction rate associated with a direct oral challenge in low-risk patients. We conducted a retrospective review of the outcomes of pediatric penicillin challenges at the Walter Reed National Military Medical Center Allergy and Immunology clinic from June 2019 to May 2023. A total of 74 challenges were included in this study. Patients were initially screened to assess the date of reaction, nature of reaction, if the reaction was life-threatening, and if the patient was hospitalized or sought emergency medical care for the reported reaction. After completion of the screening questionnaire, a direct graded challenge was performed (without skin testing) if a patient's history was deemed low risk. Patients with a recent reaction or a history of multiple drug allergies were more likely to be directed to skin prick testing and intra-dermal testing with Pre-pen and Penicillin-G prior to challenge. All patients passed all challenges. Thus, there was a 100% pass rate for both direct challenges and skin test with oral challenges. Given the low rate of adverse events in this study, expansion of penicillin delabeling in the primary care setting should be considered in patients deemed to be at low risk. It is important for allergists to empower and educate their peers and push forward a movement to create a multidisciplinary approach to penicillin delabeling.

Moisturizing effect of skin patches with hydrophobic and hydrophilic electrospun fibers for atopic dermatitis

Atopic dermatitis (eczema), one of the most common disease and also most difficult to treat, is seeking for novel development not only in medicine but also in bioengineering. Moisturization is the key in eczema treatment as dry skin triggers inflammation that damages the skin barrier. Thus, here we combine electrospun hydrophobic polystyrene (PS) and hydrophilic nylon 6 (PA6) with oils to create patches helping to moisturize atopic skin. The fibrous membranes manufactured using electrospinning: PS, PA6, composite PS – PA6 and sandwich system combining them were characterized by water vapor transmission rates (WVTR) and fluid uptake ability (FUA). To create the most effective moisturizing patches we use borage, black cumin seed and evening primrose oil and tested their spreading. We show a great potential of our designed patches, the oil release tests on a skin and their moisturizing effect were verified. Our results distinctly reveal that both fiber sizes and hydrophilicity/hydrophobicity of polymer influence oil spreading, release from membranes and WVTR measurements. Importantly, the direct skin test indicates the evident increase of hydration for both dry and normal skin after using the patches. The electrospun patches based on the hydrophobic and hydrophilic polymers have outstanding properties to be used as oil carriers for atopic dermatitis treatment.

Airway responsiveness in an allergic rabbit model

Background Animal models of allergy and bronchial hyperresponsiveness (BHR) are useful in researching pulmonary diseases and evaluating drug effects on the airways. Neonatally immunised rabbits exhibit several features of asthma as adults, including early and late airway responses following antigen challenge, oedema and inflammatory cell infiltration into the lung, BHR to inhaled histamine and methacholine (compared with naïve rabbits) and exacerbations of BHR following antigen challenge. Therefore this model can be used to investigate the underlying mechanisms of BHR and for the preclinical evaluation of new drugs for the treatment of asthma. Aim To describe the characteristics of airway responses in a rabbit model of allergic inflammation and to evaluate the relationship between skin test reactivity to antigen, airway inflammation and BHR. Methods New Zealand White rabbits were neonatally immunised against Alternaria tenius. At 3 months of age, airway responsiveness was measured to aerosolised histamine, methacholine or allergen. Bronchoalveolar lavage (BAL) was performed and cell counts recorded. Direct skin tests were performed to assess skin reactivity to allergen and passive cutaneous anaphylaxis (PCA) tests were performed to determine titres of circulating IgE. Results In a population of allergic rabbits, allergen challenge induced a significant bronchoconstriction, airway inflammation and BHR. Skin test responsiveness to allergen did not correlate with various indices of pulmonary mechanics e.g. baseline sensitivity to methacholine and histamine, or allergen-induced BHR. In contrast, skin test responsiveness did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung. Conclusion The allergic rabbit is a useful model to further our understanding of allergic diseases. Recording lung function using a minimally invasive procedure allows repeated measurements to be made in rabbits longitudinally, and each animal may thus be used as its own control. Our observations do not support the use of skin responsiveness to allergen as a predictor of airway sensitivity as we observed no correlation between skin sensitivity and airway responsiveness to inhaled histamine, methacholine or allergen. However, skin reactivity did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung. Our results also further highlight the likely dissociation between airway inflammation and BHR.

Prophylaxis of experimentally induced ovomucoid allergy in neonatal pigs using Lactococcus lactis

Probiotic Lactococcus lactis (LL) is immunomodulatory and may prevent allergy by biasing from type-2 to a type-1 immune response. We hypothesized that newborn pigs pre-treated orally with LL are protected against allergy to ovomucoid (Ovm). Pigs were assigned to two treatment groups. Piglets were pretreated orally on days of age 1–7, 10, 12, 14, 21, 28 and 35 with LL ( n = 30) or medium (control, n = 32) and sensitized to Ovm by intraperitoneal injection together with cholera toxin on days 14, 21 and 35. Pigs were orally challenged with egg white (day 46) and assigned scores for allergic signs. Outcomes were measured as direct skin tests, serum antibody to Ovm [IgG (H + L); IgE; IgG 1 and IgG 2] and cytokine production by mitogen-stimulated blood mononuclear cells (BMC). Clinical signs and skin test positivity were less frequent in the LL group ( p ≤ 0.0001). Serum antibody associated with IgG (H and L), IgE, IgG 1 or IgG 2 was significantly increased on day 46 (post-sensitization) compared to day 14 (pre-sensitization) ( p ≤ 0.0001). The LL -treated pigs had more IgE and IgG 2-related antibody activity and lower IgG 1/IgG 2 and IgE/IgG 2 ratios indicating a type-1 bias in immune response ( p ≤ 0.05). Concentration of type-2 cytokines interleukin IL-4 and IL-10 were significantly lower in supernatants of stimulated BMC of LL -treated pigs ( p ≤ 0.0001). Interferon -γ, TGF-β and IL-13 were not detected in control or treated animals. Thus, oral treatment of neonatal pigs with LL significantly reduced subsequent frequency of allergy to Ovm associated with reduced type-2 immune response correlates hence supporting the “hygiene hypothesis” and potential use of LL as a neonatal immunoregulator.

Antigenic and allergenic differences between 16 different cultivars of Olea europaea.

In southern Spain, during the months of May and June, most of the air-borne pollen is from olive trees. However, in inland regions, such as Madrid, there exist many atopic patients who exhibit positive reactions to pollen of gramineae and reactivity to Olea europaea pollen. It is remarkable that only a few of them are exclusively reactive to Olea europaea (monosensitized), in contrast to southern zones, in which we found an increase in monosensitization (1). In 1984, Gonzalez Quevedo in our department began to study Olea europaea pollen from different cultivars. Using both in vitro and in vivo techniques, we found statistically significant differences in allergenic activity and potency between the different varieties. Direct RAST and skin tests revealed greater allergenic activity in extracts of the varieties cornezuelo, cornicabra, gordal, ojiblanco, manzanilla, and verdial when compared with the other varieties studied. In addition, we confirmed that the major allergen of Olea europaea pollen has an isoelectric point with value close to 6. This major antigen is present in all the analysed extracts from the distinct 16 cultivars, and we found that the allergenic reactivity increased in parallel with the increase in content of this antigen (2). Cross-reactivity, caused by the presence of allergenic fractions common to extracts of different origin, has been widely studied using inhibition RAST and, less frequently, by CRIE (radioimmunoelectrophoresis) and reverse enzymoimmunoassay. Bousquet et al. studied the cross-reactivity between four types of Oleaceae (Olea europaea, Fraxinus excelsior, Ligustrum vulgare, and Phillyria angustifolia) using inhibition RAST, isoelectrofocusing, and tandem crossed immunoelectrophoresis (CIE). They detected a high degree of cross-reactivity but not a total identity between these four pollen species (3). In 1992, Baldo et al. studied the cross-reactivity between olive and privet pollens, with olive pollen having major antigens between 18 and 19 kDa, 20 kDa, and 40 kDa, while pollens in privet were in the range of 19, 20, and 40 kDa. Baldo et al. concluded that the presence of IgE antibodies that react with the pollen may not necessarily be a consequence of the sensitization to the pollen of these species (4). In 1984, our group studied 16 cultivars of Olea europaea from the botanical and agronomic point of view (5–14). This comprised a biological evaluation in vivo and in vitro, and a study of the protein content of the pollen extracts, aimed at establishing whether there are distinctive characteristics among the different cultivars.

Commercial laboratory preparation of immunotherapy vials

The efficacy of allergen-specific immunotherapy injections for allergic patients continues to be documented. Recent reports on sublingual immunotherapy have acknowledged this route as a viable and safe alternative to subcutaneous immunotherapy for reducing respiratory symptoms. Allergens can be determined by direct skin testing (in vivo) or by serum analysis (in vitro). In vivo testing includes scratch, prick/puncture, intradermal, and skin endpoint titration. In vitro testing uses a form of a radioallergosorbent test to measure allergen-specific IgE. The use of a US Food and Drug Administration–licensed commercial laboratory for the preparation of immunotherapy offers numerous advantages for the physician: any method of testing can be accommodated according to the physician’s prescription; immunotherapy injections are prepared in a certified cleanroom following stringent guidelines to ensure quality and sterility; and a physician’s overhead costs for staff, space, and supplies, as well as staff time constraints, can be reduced.

Roasted fullfat soybean as an ingredient of milk replacers for goat kids

The present work was aimed at studying simple methods for processing fullfat soybean, and at designing soy-based milk replacers suitable for goat kids. Soybean was roasted at 100°C for 10 (HSF10) or 30 (HSF30) min. The residual antitryptic activity and immunoreactive glycinin and β-conglycinin, respectively, were 40, 17 and 5% for HSF10, and 20, 6 and 3% for HSF30, of those in raw soybean. Milk replacers containing 24% CP and 22% fat were prepared. In the control diet, skim milk powder and sweet whey provided 95 and 5% of total protein, respectively. In the soy-based diets, 45% of total protein was from either the HSF10 or the HSF30 flour, the remainder being provided by skim milk powder and sweet whey (45 and 10% of total protein, respectively). These diets were given as liquid milk replacers to 20 goat kids ( n=6, 8 and 6 for control, HSF10 and HSF30 treatments, respectively) between 14 and 50 days of age. Nutrient digestibility and N balance were measured twice over 5 days starting at 26 and 40 days of age. Growth and DM intake were not significantly different between treatments. The digestibility of N was lower for the soy-based diets as compared with the control diet. It did not change significantly over time for the control and HSF10 diets (average values of 0.915 and 0.67, respectively) but it increased significantly from 0.70 to 0.80 for HSF30 between the two measurement periods. Direct skin tests carried out with soybean protein extracts after the second measurement period revealed only delayed reactions to HSF10 extracts in the HSF10 group. Roasting fullfat soybean at 100°C for 30 min appeared to provide a milk replacer ingredient nutritionally more acceptable for rearing kids than roasting for 10 min.

Volumetric Assessment of Airborne Pollen and Spore Levels in Rochester, Minnesota, 1992 Through 1995

To reassess airborne pollen counts and to study spore counts by volumetric collection in Rochester, Minnesota. Samples of pollen and spores were collected from the top of a six-story building in downtown Rochester by use of a rotational rod sampler, which was activated for 30 seconds every 10 minutes for 24 hours a day, 5 days a week, from mid-April to mid-October 1992 through 1995. Particles were stained with Calberla's fluid and viewed microscopically by transmitted light. Identifications were substantiated by comparison with field-collected "known" materials and standard reference guides. Data were expressed as "particles retained/cubic meter of air sampled." Because the methods of collection varied, only qualitative comparisons could be made with a study done in Rochester more than 3 1/2 decades earlier. For tree pollens, a similar progression of appearance and seasonal duration were noted for most species. Alder (Alnus), willow (Salix), and hickory-pecan (Carya), however, were found to have distinctly longer seasons, and walnut (Julgans) was detected 2 weeks earlier in the season. The most frequently detected tree pollen had changed from oak (Quercus) to apple and crab apple (Malus), which was not reported at all previously. Ragweed (Ambrosia) was still found to peak at the end of August and had a similar duration. Study of grass and nettle pollen as well as the Amaranthaceae-Chenopodiaceae complex yielded findings similar to those in the prior investigation. Fungal spores were detected from April through October and represented a substantial percentage of the airborne allergens; Cladosporium, ascospores, and basidiospores were the most common. Volumetric assessment of airborne pollen and spore levels in Rochester, Minnesota, yielded useful information for clinicians in southern Minnesota that could help direct skin test selection.

Identification of soyabean allergens and immune mechanisms of dietary sensitivities in preruminant calves

The allergenicity of soya proteins was assessed by direct skin testing and by in vitro lymphoproliferation tests in calves fed milk substitutes containing skim milk powder (sMP) or an antigenic heated soya flour (HSF). During the last three weeks of treatment, the calves were injected intradermally with raw soya flour (RSF), HSF, hydrolysed soya protein isolate (HSPI), sMP or purified soya proteins, after being premedicated with anti-histamine or not. Peripheral blood leucocytes (PBL) were grown over five days with various mitogens or dietary antigens, and the incorporation of tritiated thymidine was measured. Strong skin oedema reactions to RSF, HSF and all the purified proteins were observed in the calves fed HSF at various times up to 24 hours after injection. The skin oedema was largely prevented by premedication with anti-histamine. A strong delayed skin thickening was observed in the calves fed HSF for up to five days with β-conglycinin. PBL from the calves fed HSF proliferated in vitro with HSF, HSPI and β-conglycinin, but not with glycinin. Thus, most proteins from soyabean were implicated in the immediate and semi-delayed immune reactions, whereas β-conglycinin was strongly involved in a delayed type hypersensitivity in calves.

Influence of soya antigen levels in milk replacers on the disruption of intestinal motility patterns in calves sensitive to soya.

An experiment was designed to determine the soya antigen levels in milk replacers above which gastrointestinal disorders appeared in preruminant calves previously sensitized to antigenic soya by feeding a soya-based milk replacer for 3 months. These calves were then equipped with wire electrodes on the duodenum and the mid-jejunum. The sensitization was visualized using direct skin testing, plasma anti-soya antibody determination and intestinal myoelectric activity recording. After sensitization, the calves were occasionally fed liquid test meals containing various proportions of antigenic soya and whey. The soya-fed calves displayed larger 24 h skin reactions to beta-conglycinin and higher plasma anti-soya antibody titres than the controls maintained on a skim-milk based milk replacer. Disturbances of the myoelectric activity patterns were recorded on the duodenum and mid-jejunum after feeding antigenic soya, but not non-antigenic soya or milk protein, in the soya-sensitized calves. When the level of antigens was varied, disorders in the jejunal motility patterns appeared when antigenic soya provided one-third or more of the dietary protein in the test meals, although some abnormalities were evident at lower incorporation rates. The major change was a reduction in the mean duration of the jejunal migrating motor complexes which was essentially accounted for by a decrease in the mean duration of the phase I (quiescence). This level of antigens corresponded approximately to 14 and 12 mg of immunoreactive glycinin and beta-conglycinin respectively, per gram of protein intake, i.e. 80 and 70 mg/kg0.75 per test meal.

Isolation and partial characterization of Bermuda grass pollen allergen, BG‐60a

In an earlier study we showed that Bermuda grass (Cynodon dactylon) pollen contains at least 12 IgE-binding proteins that can be analysed by immunoblot technique. One of the active components (BG-60) proved to be a basic protein of glycoprotein nature. It contained about 28% carbohydrate as determined from the dry weight and consisted of four molecules. One of the components was purified from the pollen extract by a combination of ammonium sulphate precipitation, ion-exchange chromatography on carboxymethyl-TSK, gel filtration on Ultrogel AcA 44 and chromatofocusing. Its molecular weight was approximately 60 kD by SDS-PAGE and 34 kD by gel filtration chromatography. The isoelectric point of the antigen was about 9.7. The homogeneity of the antigen BG-60a was assessed by one single arc of immunoprecipitation both in immunodiffusion and crossed immunoelectrophoresis and by one single band after SDS-PAGE. Its allergenicity was demonstrated by direct intradermal skin test on allergic patients and by examining IgE-binding reactivity with allergic patients' serum.

Studies for revealing a possible sensitization to hirudin after repeated intravenous injections in baboons

The immunogenic potential of natural and recombinant hirudin was investigated using baboons. Animals received 4 intravenous hirudin injections of 1,000 antithrombin units/kg at certain times (day 1, 3, 8 and 42) and were checked for an immune response. None of the tests performed (in vitro histamine-release, ELISA for detection of humoral hirudin-specific IgG and IgM antibodies by indirect ELISA, direct skin test) revealed any kind of sensitization to hirudin. Urinary excretion of hirudin was not diminished by successive injections, if diuresis was within normal ranges. In summary, these results confirm previous observations indicating the weak antigenic potential of hirudin. Therefore, immune reactions to hirudin in man during therapeutic measures requiring several exposures to the inhibitor should not to be expected under normal circumstances.

Esporotricosis diagnosticada por el laboratorio

Forty cases of sporotrichosis have been diagnosed from 1976 to 1989 at the Mycology Laboratory of the Instituto Nacional de Salud. The disease was present in patients 4 to 52 years old, and 35 of 40 (87.5%) were males. Fixed cutaneous and lymphocutaneous forms were predominant, 45% and 42.5% respectively. The diagnosis was established by isolation of Sporothrix schenckii in 92% of the cases. Two patients were diagnosed using direct fluorescence, skin test and tube agglutination.

Antigenic and Allergenic Determinants of Ovalbumin

The decapeptide 1-10 of hen's egg ovalbumin (OA), deduced from the known amino acid sequence (Gly-Ser-Ile-Gly-Ala-Ala-Ser-Met-Glu-Phe), was synthesized by Merrifield solid phase peptide synthesis with a yield of greater than 70%. The completeness of the insertion of amino acids during synthesis was monitored by the amino acid compositions of the peptide-resin, prior to coupling of the preceding residue. The linearity of the synthesis was supported by dansyl Edman degradation and detection of three NH2 terminal residues 5-dimethylamino-naphtheline-1-sulphonyl (DNS)-Gly, -Ser, -Ile, respectively. The peptide was purified by gel filtration chromatography and analytical reversed-phase high-performance liquid chromatography (HPLC). The homogeneity of the preparation was calculated both from the amino acid analysis and by integrating the peaks of HPLC to be greater than 83%. The antigenicity of the purified (P2) peptide could be detected by precipitation inhibition with the nephelometric technique. The decapeptide could also specifically react with functional structures on reaginic IgE molecule from the sera of individuals allergic to eggs, inhibiting its further binding to ovalbumin. An in-vivo experiment using direct skin test on two patients allergic to eggs showed no activity, rendering further testing unnecessary. The results suggest that the decapeptide of the NH2 terminal segment of OA encompasses an Ig-binding haptenic epitope.

Antigenic/allergenic characterization of American and German cockroach extracts

Cockroach allergens have been implicated as clinically significant sensitizing agents in the induction/exacerbation of “urban asthma.” In the present study, approximately 50% of atopic, predominantly inner-city residents had immediate wheal-and-flare cutaneous reactivity to a commercial American cockroach whole body extract. Crude whole body extracts were prepared in our laboratory from both American ( Periplaneta americana) and German ( Blatella germanica) cockroach species. Crossed immunoelectrophoresis of American cockroach whole body extract (AWBE) and German cockroach whole body extract (GWBE) detected a total of 50 and 56 precipitin peaks, respectively, when extracts were reacted with hyperimmunized rabbit antisera. Crossed radioimmunoelectrophoresis identified at least five electrophoretically distinct allergens each in AWBE and GWBE. Cockroach whole body extracts produced two major protein peaks when extracts were fractionated on Sephadex G-75. RAST-inhibition studies demonstrated allergens in both peak 1 and the immediate trailing fractions of the column. Direct RAST and end point prick skin testing confirmed the presence of signficant/important allergens in column “fraction 2” of AWBE. Skin testing and RAST analysis suggested the occurrence of shared and species-specific allergens between AWBE and GWBE. Collectively, these studies confirm the important sensitizing potential of cockroach allergens, characterize their number and size distribution by crossed radioimmunoelectrophoresis and column chromatography, support the occurrence of significant allergens in column “fraction 2,” and suggest the occurrence of both species-specific and shared interspecies allergens.

The diversity of reaginic immune responses to platinum and palladium metallic salts

As part of a National Institute for Occupational Safety and Health health hazards evaluation, workers employed in a precious metal refinery exposed to platinum (Pt), palladium (Pd), and other group VIII metallic salts were evaluated for direct skin test sensitivity to Pt. Current (107) and former (30) workers who quit or were discharged because of Pt-related health problems were prick tested with ammonium hexachloroplatinate ([NH 4] 2 PtCl 6). Of the 107 currently exposed workers, 15 (14%) exhibited positive skin tests, as indexed by immediate reactivity at a dose of 10 3 gm/ml or less. Eight (27%) of the 30 former workers no longer exposed to Pt also demonstrated positive Pt skin tests. Sera obtained from the workers were assessed for transferable antibodies to Pt and Pd salts by monkey passive cutaneous anaphylaxis. In addition, Pt-specific antibodies were evaluated by RAST. Results of these studies suggested that short- and long-term passive cutaneous anaphylaxis immune responses occur after exposure to both Pt and Pd compounds. Results of RAST analysis for Pt-specific antibodies indicated that significantly higher (p < 0.001) levels were present in the sera of skin test-positive workers as compared to control sera from Pt-exposed, skin test-negative workers or nonexposed control subjects. Evidence was also obtained that Pt or Pt-protein adducts present in the sera of exposed workers may compete for IgE-binding sites in the RAST assay. The specificity of the Pt-specific RAST system was proved by inhibition experiments.

Allergenic impact of inhaled arthropod material.

We have reviewed a number of aeroallergens, derived from arthropods, that can induce allergic respiratory illnesses. The insects and acarids responsible often are easily overlooked or, if evident, have allergenic impacts that are not well recognized. Use of techniques such as RAST, RAST inhibition, and assays of mediators from both passively sensitized lung and basophil-rich leukocyte suspensions has facilitated identification of these new allergens and their sources. Direct skin and inhalation challenge testing have provided clinical correlations in vivo, emphasizing the potential importance of these agents. The high prevalence and intensity of type 1 responses to environmental arthropods (eg, cockroaches, house dust mites, moths, and butterflies) suggests that their significance as causes of persistent airway diseases may, at times, exceed that of pollens. Further investigation clearly is warranted, and it is our opinion that arthropod allergies must be considered and investigated seriously in all patients with respiratory allergy that is not otherwise readily explained, particularly bronchial asthma. Such an enlightened approach offers both a fuller understanding of disease causation and, we believe, a means to achieve improved patient care.

Standardization of Dermatophagoides pteronyssinus: assessment of potency and allergen content in ten coded extracts.

As part of the studies to establish an international reference preparation of Dermatophagoides pteronyssinus allergens, ten coded extracts of this mite were assessed in four laboratories. The extracts were compared for total potency using direct RAST, RAST inhibition and quantitative skin tests, and also for composition and major allergen content using crossed immunoelectrophoresis, crossed radioimmunoelectrophoresis, rocket immunoelectrophoresis and radioimmunoassay. In addition, the source materials were examined by light microscopy, and the extracts were examined for the presence of proteins/allergens derived from the culture media. To help with standardization, a new reference pool of sera from patients allergic to D. pteronyssinus was also established (National Institute of Biological Standards and Control, NIBSC, 82/528). The results showed that techniques are available for measurements of potency and allergen content. In several of the extracts, culture medium derived allergens and antigens were demonstrated. It also became clear that extracts varied not only in their total potency but also in the distribution of the identifiable allergens. In particular, extracts derived from isolated mites contained more AgX and/or Ag 23 relative to their content of antigen P1 (= Ag42). These studies lead to the choice of an extract for an international reference preparation (NIBSC 82/518) and helped to establish the methods used subsequently in the international collaborative study.

Direct skin test in highly sensitized guinea pigs for rapid and sensitive determination of staphylococcal enterotoxin B.

The direct skin test in highly sensitized guinea pigs was developed as a rapid and extremely sensitive assay for detection of staphylococcal enterotoxin B (SEB) in foods. This report details the experimental conditions required to elicit optimal sensitization of guinea pigs to SEB. An intense and persistent immunoglobulin E (IgE) anti-SEB response was established in strain 13 guinea pigs pretreated with cyclophosphamide followed by four sensitizing doses of 10 micrograms of SEB 1 month apart. The conditions, however, optimal for eliciting IgE responses led to a sustained failure to produce antibody of the IgG1 subclass. With the use of highly sensitized guinea pigs, one can achieve a sensitivity ranging from 0.1 to 1.0 pg of purified SEB by the direct skin test for at least 7 months after the last challenge. For analysis of SEB in food extracts, the entire assay can be accomplished within 20 min with a sensitivity of 10 to 100 pg SEB per ml of prepared food samples, and the recovery of enterotoxin from spiked food products ranged between 75 and 89% of the amount added.

IgE Responses in Human Schistosomiasis

We have developed a non-competitive solid-phase radioimmunoassay (SPRIA) to quantitate human IgE antibodies to Schistosoma mansoni antigens that was capable of accurately measuring IgE antibodies in both high and low titer sera. Ninety sera from "early" or "chronic" schistosomiasis patients were studied. Both levels of parasite-specific IgE antibodies and the proportion of the total IgE response that was parasite-specific were significantly lower in "early infection" sera than in sera of patients with chronic infections. The SPRIA to adult worm antigen was compared with basophil histamine release and direct intradermal skin testing also performed with the adult antigen. Both tests showed significant correlations with the SPRIA in detecting specific anti-parasite antibody.