Food reactions in pollen and latex allergic patients

[Latex allergy]

Latex allergy has become an increasing cause of morbility in the last few years and is now recognized as an international health problem. The prevalence of latex sensitization among the general population is less than 1 %. The groups at highest risk include healthcare workers, rubber industry workers, patients with a history of multiple surgical procedures, particularly children with spina bifida and urogenital abnormalities, atopic individuals, and patients with certain fruit allergies (especially kiwi, avocado, chestnut and banana). The molecular and immunological characteristics of several natural latex allergens have been identified. Symptoms range from contact urticaria to anaphylaxis. Diagnosis is based on clinical history and is confirmed by skin prick tests. Measurement of serum specific IgE to latex can also be useful. The best treatment is latex avoidance and substitution by other materials. However, because latex products are ubiquitous in medical and nonmedical devices of daily use, a latex-free environment is not easy to achieve. In some patients, immunotherapy could be an alternative.

Latex allergy: prevalence, risk factors, and cross-reactivity

There are few little exact epidemiological data on the prevalence and incidence of latex allergy, partly because the diagnostic tools are unsatisfactory and partly because the epidemiological study planning often does not fulfill criteria of good praxis. On the basis of present data, latex allergy in normal population is low, under 1%. Known risk groups such as health care workers, atopic subjects, people with hand dermatitis, and especially spina bifida patients show higher prevalence numbers. The common serological cross-reactivity between latex and a great number of different fruits and vegetables is bound to common plant pathogenesis-related proteins and storage proteins. Despite positive serological tests, only about half of NRL-allergic subjects have clinical symptoms after eating cross-reacting foods.

Cloning of cDNA encoding a soybean allergen, Gly m Bd 28K

A cDNA clone encoding a soybean allergen, Gly m Bd 28K, has been isolated. The clone has a 1567-bp cDNA insert with a 1419-bp open reading frame and a 148-bp 3'-untranslated region, followed by a polyadenylation tail. The open reading frame was shown to encode a polypeptide composed of 473 amino acids. The chemically determined amino acid sequences of the peptides obtained from the allergen, including its N-terminal peptide, were shown to be contained in the N-terminal region of the amino acid sequence deduced from the cDNA, showing that the first half of the cDNA encodes the allergen with a preceding segment of 21 amino acids. The peptide fragment including the allergen was expressed as a fusion protein with glutathione S-transferase in Escherichia coli and immunoblotted with the sera of soybean-sensitive patients and the monoclonal antibody against the allergen. Furthermore, homology analyses demonstrate that the polypeptide for the cDNA exhibits high homology with the MP27/MP32 proteins in pumpkin seeds and the carrot globulin-like protein. This finding suggests that the polypeptide may consist of a 21-amino acid segment as a part of the signal peptide and the proprotein, which may be converted to two mature proteins, Gly m Bd 28K and a 23-kDa protein, during the development of soybean cotyledons.

Allergic sensitization and clinical reactions to latex, food and pollen in adult patients

BACKGROUND

Many latex-allergic patients are sensitized to one or more foods. Patients allergic to tree and/or grass pollens are also often sensitized to plant-derived foods. Atopy, defined in most studies as sensitivity to an aeroallergen, is a risk factor for latex allergy. The relative importance of pollen sensitivity, a sign of atopy, as a risk factor for food allergy in latex-allergic patients has not, however, been examined.

OBJECTIVE

To investigate the relationship between pollen sensitivity and sensitivity to food in latex-allergic patients.

METHODS

Forty-four latex-allergic patients (Groups 1 and 2), 24 of whom were also allergic to tree and/or grass pollen (Group 1) and 25 pollinosis patients who were not allergic to latex (Group 3) were studied. We obtained a history of reactions to food and skin tested them with 12 fresh-frozen fruits.

RESULTS

All 12 foods induced a skin test reaction in at least one patient in each of the three Groups. There were, however, twice as many positive skin test reactions to food in patients with pollinosis, whether or not they were allergic to latex, as there were in patients allergic to latex but not to pollen. Latex-allergic patients were most likely to have a positive skin test and a history of a reaction to avocado or banana whereas patients with pollinosis only were most likely to have a positive skin test and a history of a reaction to apple, peach or celery.

CONCLUSIONS

These results suggest that concomitant allergy to pollen is an important risk factor in determining which plant-derived foods sensitize latex-allergic patients.

Analysis of the three-dimensional antigenic structure of giant ragweed allergen, Amb t 5

The ragweed allergens Amb t 5 and Amb a 5 are among the smallest inhaled protein allergens known, containing a single, immunodominant T-cell epitope. In this study we analyzed the B-cell epitope structure of Amb t 5. The three-dimensional structures of Amb t 5 and Amb a 5 have been determined by NMR spectroscopy, providing a rare opportunity to analyze three-dimensional antigenic sites. Amb t 5 residues likely to be important for antigenicity were identified by examining the surface area of Amb t 5 accessible to a probe of the size of an antibody molecule. After changing these residues to the corresponding Amb a 5 residues, recombinant proteins were purified and tested for loss of antigenic activity. Inhibition radio-immunoassays, using sera from 8 individuals who had received immunotherapy with giant ragweed extract, allowed the mutations to be divided into three groups: (1) mutations that had little or no effect on antibody binding, (2) mutations that caused a loss of antigenic activity to a different degree in different sera and (3) mutations that drastically reduced antigenic activity in all sera tested. This last set of mutations clustered in the third loop of Amb t 5, suggesting that antibody recognition of Amb t 5, like T-cell recognition, is primarily directed towards a single, immunodominant site.

"Latex-fruit syndrome": frequency of cross-reacting IgE antibodies

An association between allergies to latex proteins and to various foods has been reported and confirmed by RAST and immunoblotting inhibition. However, no significant data had been collected on the frequency of specific IgE antibodies to fruits in these patients and the frequency of a history of fruit intolerance. Serum samples of 136 patients with well-documented, clinically relevant, immediate-type hypersensitivity against latex proteins were analyzed for IgE antibodies against a panel of different fruits. Patient history of food intolerance was documented by a standardized questionnaire. Fruit-specific IgE antibodies were detected in 69.1% of serum samples. Cross-reacting IgE antibodies recognizing latex and fruit allergens (papaya, avocado, banana, chestnut, passion fruit, fig, melon, mango, kiwi, pineapple, peach, and tomato) were demonstrated by RAST-inhibition tests. Of our patients, 42.5% reported allergic symptoms after ingestion of these fruits and a total of 112 intolerance reactions were recorded. However, fruit-specific IgE antibodies were detected only in serum samples from 32.1% of the patients who perceived symptoms due to these fruits. Thus, serologic tests seem to be of low significance for prediction o food allergy in latex-allergic patients.