Dennis R. Ownby

Watermelon and ragweed share allergens.

A biotin-avidin amplified ELISA was used to measure antigen-specific IgE for ragweed, representative members of the gourd family (watermelon, cantaloupe, honeydew melon, zucchini, and cucumber), and banana in the sera of 192 allergic patients, each with an IgE greater than or equal to 180 microns/ml. Sixty-three percent (120/192) of the sera contained antiragweed IgE, and of these patients, 28% to 50% contained IgE specific for any single gourd family member. In contrast, no greater than 11% of the sera positive for a given gourd or banana were negative for ragweed. Correlations between ragweed and gourd-specific IgE levels were significant (p less than 0.001), and correlation coefficients between any two gourds exceeded 0.79. In an ELISA system, the extracts of watermelon and ragweed inhibited each other in a dose-dependent manner; the resulting nonparallel inhibition curves indicate that some, but not all, of the allergens in the two extracts are cross-reactive. Isoelectric focusing of watermelon and ragweed extracts in narrow range gel (pH 4 to 6) followed by immunoblotting demonstrated six watermelon allergen bands with isoelectric points identical to those of ragweed allergens. Several remaining bands in the two extracts had differing isoelectric points, however. Six of 26 patients interviewed with watermelon-specific IgE reported developing oropharyngeal symptoms (itching and/or swelling of the lips, tongue, or throat) after ingesting at least one of the study foods, whereas only one of 25 patients interviewed without detectable watermelon-specific IgE reported similar symptoms (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis after ingestion of beignets contaminated with Dermatophagoides farinae

A 48-year-old man was evaluated for anaphylaxis associated with ingestion of beignets prepared from a commercial mix. Microscopic examination of the patients beignet mix revealed live Dermatophagoides farinae. Another unopened box from the same source was not infested. Skin test results to aeroallergens and foods, including all beignet mix ingredients, were positive only to D. farinae and D. pteronyssinus extracts. Skin prick test results to an infested mix extract (1:5 wt/vol) were also positive, but no reaction was observed with noninfested mix extract. ELISA inhibition studies demonstrated significant inhibition of the patients serum binding to D. farinae strips by infected mix extract. Parallel inhibition curves were produced by the infested mix extract and a commercial D. farinae extract. Noninfested mix extract showed no inhibition. RAST analysis with beignet mix discs showed significant binding of the patients serum IgE to infested mix discs but not to noninfested mix discs. RAST inhibition studies revealed more than 86% inhibition of binding of the patients IgE to infested mix discs by infested mix extract and D. farinae extract. No inhibition was observed with noninfested mix or 5% fetal calf serum-phosphate-buffered saline. We conclude that the allergen to which the patient reacted was most likely D. farinae and that ingestion of D. farinae may cause anaphylaxis in sensitive persons.

Use of urinary cotinine and questionnaires in the evaluation of infant exposure to tobacco smoke in epidemiologic studies

Exposure to environmental tobacco smoke is an important variable in many pediatric epidemiologic studies. We measured urinary cotinine, a specific metabolite of nicotine, in a population-based cohort of children every other month from birth through two years of age. Extensive data regarding exposure to smokers (people in the home, in home and away from home day care, home visitors, visits to smokers) were collected monthly by way of home interviews. We evaluated, with multiple cotinine measurements as the gold standard, other measures of exposure that are more feasible to obtain in large-scale studies. Comparing one cotinine to the average of multiple measurements, we found that 33.7% were in error in excess of 100 ng/mg, but 84% of the infants could be correctly classified into categories of low versus high. Parental smoking patterns had the highest predictive accuracy (fathers 67.0% and mothers 64.1%). Combining selected smoker categories (either parent, other home residents outside day care workers) resulted in improved accuracy of 79.3%.

Passive exposure to cigarette smoke does not increase allergic sensitization in children

The purpose of this study was to learn whether children passively exposed to parental cigarette smoke would be more frequently sensitized to common allergens or would have higher concentrations of allergen-specific IgE. To evaluate this question, we studied two groups of children aged 2 to 17 years. The first group consisted of 100 children selected from a general pediatric group practice. These children were being observed for well-child care, and the only selection criteria were the need for a venous blood sample for a reason unrelated to the study. The second group of 91 patients were consecutively referred, from the same pediatric group, for allergy evaluation because of respiratory tract symptoms. Parental smoking histories were obtained, and total serum IgE, IgD, and IgE specific for cat, dog, mite, ragweed, grass, and cockroach were measured by ELISA. Children of smoking mothers had significantly greater IgD concentrations (p = 0.03) and were more likely to be referred for allergy evaluation (p = 0.0001), but these children did not have increased concentrations of total or allergen-specific IgE. Exposed children were not more likely to be serologically sensitive to any of the allergens tested. We conclude that children passively exposed to cigarette smoke do not produce more IgE to common allergens nor are they more likely to produce IgE to any particular allergen.

Stability of immunoglobulin E (IgE) in stored obstetric sera

OBJECTIVEnTo determine the stability of immunoglobulin E levels in obstetric sera.nnnMETHODSnAlaSTAT(R) and AlaTOP(R) (Diagnostic Products) were used to assay total and specific IgE levels in obstetric sera collected in Memphis, TN and Portland, OR. The samples were collected from the Collaborative Perinatal Project (CPP) between 1959 and 1965 and stored at -20 degrees C. The assay results were compared with IgE levels found in sera collected at the same locations for the Calcium for Pre-eclampsia Prevention Study (CPEP) and stored since 1992 at -70 degrees C. The samples were also assayed for cockroach (CR) and mouse urine specific IgE using the AlaSTAT(R) assay (Diagnostic Products).nnnRESULTSnTotal IgE and specific IgE to CR and mouse urine were detectable in older and recent samples. The median total IgE for the recent and older Portland samples was 26 IU/ml and 65 IU/ml, respectively. The median total IgE was identical (40 IU/ml) in the recent and older Memphis samples.nnnCONCLUSIONnLong-term storage does not diminish the ability to measure serum IgE. Levels of IgE in sera stored 32-37 years were equal to or greater than levels in sera stored for 5 years. reserved.

Computerized measurement of allergen-induced skin reactions

The areas of 50 randomly chosen skin-test reactions were measured with a graphics tablet interfaced to a microcomputer. The computer-determined areas were compared with the sums and products of orthogonal diameters, the maximum diameter, and the actual areas of the reactions. The areas measured by the computer were highly correlated with the actual areas (r = 0.999). Both the sums and products of orthogonal diameters were also highly correlated with the actual areas (r = 0.953 and r = 0.988, respectively) and added little to the correlation of the maximum diameter (r = 0.923). The average coefficient of variation for repeated computer area measurements was 5.3%. Area and maximum diameter measurements were then compared in a study designed to evaluate the variation of prick tests applied by different persons. Area measurements revealed significant differences between the testers, which were not found when maximum diameter measurements were compared. Computerized area determination is a rapid, accurate means for quantitating skin-test reactions. The precision offered by this method is of potential importance for studies involving quantitative skin testing.

Evaluation of the cause of nasal and ocular symptoms associated with lawn mowing

A number of individuals with perennial or seasonal rhinoconjunctivitis state that their symptoms may suddenly worsen on exposure to lawn mowing. Many allergists have believed that this was related to the agitation of molds deposited on the grass. We studied 50 consecutive new patients with rhinitis using history, skin testing, total and specific IgE assays, and nasal smears. Twenty-five patients gave histories of minimal or no change in their nasal symptoms with exposure to lawn mowing, whereas 11 patients had definite, but mild, symptoms, and 14 patients had severe symptoms. Positive skin tests to grasses, trees, and weed pollens were more frequent in those patients with symptoms exacerbated by lawn mowing (p less than 0.03). Symptomatic patients also had higher serum concentrations of total IgE (p less than 0.008) and grass-pollen specific IgE (p = 0.0004). The frequencies of positive skin tests to ragweed pollens, house dust, molds, and grass leaves, as well as the percentage of nasal eosinophils, were not different in the symptomatic and asymptomatic groups. No significant association was found between symptoms and IgE antibodies to molds or grass-leaf extract. We believe that the increased nasal and ocular symptoms coincident with lawn mowing are allergic phenomena significantly associated with skin test sensitivity and specific IgE antibodies to grass pollens but not with sensitivity or specific IgE to molds or grass-leaf extract.

An improved prick skin-test procedure for young children

The prick method of skin testing is advantageous for young children because of the decreased risk of anaphylaxis and less patient discomfort. Some would argue, however, that the necessity of keeping extract drops at the skin-test sites makes prick testing impractical compared with intradermal testing for squirming youngsters. Since the literature is not clear concerning the length of time extract must be present at the prick site, we performed duplicate sets of prick tests with five concentrations of ragweed extract on 16 ragweed-sensitive adults. For one set of tests, the drops were removed immediately after the skin had been pricked; for the other set, extracts remained at the site for 15 min. After 15 min we recorded the size of the wheal and flare response for each test. On the basis of analysis of these paired observations, we concluded that there is no significant difference between these two methods of administering prick skin tests.

Antibody responses in watermelon sensitivity

Watermelon-specific IgE (WM-IgE) appears to mediate the oropharyngeal symptoms after watermelon ingestion. However, less than one fourth of watermelon-sensitive individuals (i.e., those with detectable WM-IgE) develop such symptoms after watermelon ingestion. In an attempt to separate symptomatic from asymptomatic persons, we measured watermelon-specific-IgE and IgG4 concentrations in the sera of 29 watermelon-sensitive patients, 6 of whom were symptomatic. Although the mean WM-IgE level of the symptomatic group exceeded that of the asymptomatic group (p = 0.04), individual WM-IgE values failed to distinguish symptomatic from asymptomatic persons. No differences in WM-IgG4 levels between the two groups could be found. Watermelon extract proteins were separated by isoelectric focusing and blotted to nitrocellulose membranes. The membranes were reacted with the individual sera of 14 watermelon-sensitive patients and then stained for IgE, IgG1, and IgG4 binding. Great variations in IgE, IgG1, and IgG4 binding patterns were found, but no subtype restrictions were discovered. Although the pattern of IgE-stained bands in the absence of corresponding IgG1-stained bands was seen more frequently in symptomatic individuals, immunoblot patterns failed to separate symptomatic from asymptomatic persons. We conclude that the pattern of IgE, IgG1, and IgG4 responses to separated watermelon allergens was not predictive of clinical symptoms in a group of watermelon-sensitive patients.

Maternal group B Streptococcus and the infant gut microbiota.

Early patterns of gut colonization may predispose children to adult disease. Exposures in utero and during delivery are associated with the infant gut microbiome. Although ~35% of women carry group B strep (GBS; Streptococcus agalactiae) during pregnancy, it is unknown if GBS presence influences the infant gut microbiome. As part of a population-based, general risk birth cohort, stool specimens were collected from infants diapers at research visits conducted at ~1 and 6 months of age. Using the Illumina MiSeq (San Diego, CA) platform, the V4 region of the bacterial 16S rRNA gene was sequenced. Infant gut bacterial community compositional differences by maternal GBS status were evaluated using permutational multivariate analysis of variance. Individual operational taxonomic units (OTUs) were tested using a zero-inflated negative binomial model. Data on maternal GBS and infant gut microbiota from either 1 (n=112) or 6-month-old stool (n=150) specimens was available on 262 maternal-child pairs. Eighty women (30.5%) were GBS+, of who 58 (72.5%) were given intrapartum antibiotics. After adjusting for maternal race, prenatal antifungal use and intrapartum antibiotics, maternal GBS status was statistically significantly associated with gut bacterial composition in the 6 month visit specimen (Canberra R 2=0.008, P=0.008; Unweighted UniFrac R 2=0.010, P=0.011). Individual OTU tests revealed that infants of GBS+ mothers were significantly enriched for specific members of the Clostridiaceae, Ruminococcoceae, and Enterococcaceae in the 6 month specimens compared with infants of GBS- mothers. Whether these taxonomic differences in infant gut microbiota at 6 months lead to differential predisposition for adult disease requires additional study.