Latex allergy--Part II

Diagnosis of latex allergy consists of four methods: anamnesis, skin tests, laboratory examinations and specific allergen challenge. Anamnesis is the source of information on the symptoms and reactions of IgE-dependent allergy, different accompanying factors and atopy diseases. The recognition of latex allergy is possible with positive SPT and/or sIgE (latex). Specific allergen challenge is performed in situation with positive anamnesis, negative SPT and negative sIgE (latex). Latex allergy treatment is not different than other allergic diseases. Specific immunotherapy is new methods in these cases. Because of absence of standardized latex allergens, this method is still on experimental issue. The inconsistent results do not allow the recommendation of immunotherapy in everyday practice. The most important prophylactic activity in case of latex allergy is to reduce the exposure to latex among the medical staff and the patients.     

Latex allergy

Latex allergy continues to be an important medical problem. In this review we re-examine the definition of latex allergy, the offending allergens, the factors that enhance sensitization, the threshold levels that sensitize and elicit reactions in sensitized individuals, current diagnostic techniques, avoidance measures, the barrier properties of nonlatex alternatives, and the roles of premedication and immunotherapy. Twenty years after its resurgence, latex allergy is a well-defined condition with established diagnostic criteria and rational treatment and prevention strategies. However, in spite of advances associated with molecular studies of latex allergens and improved understanding of immunotherapy, avoidance remains the only effective treatment. (J Allergy Clin Immunol 2000;105:1054-62.)     

Latex antigens.

Previous studies have demonstrated that some children with spina bifida have IgE to proteins in natural rubber. In this study we compare different sources of latex antigen and identify possible antigenic peptides by radioimmunoblotting technique. Sera were collected from 26 children with spina bifida, tested by RAST with ammoniated latex extract (AL), and frozen until use. Extracts were prepared from ammoniated and nonammoniated latex, and the proteins were separated by electrophoresis on a 15% sodium dodecyl suflate-polyacrylamide gel and transferred to polyvinylene difluoride (PVDF). Strips of PVDF were then incubated with individual sera and 125I-labeled rabbit antihuman IgE before development by autoradiography; 18/26 sera were AL RAST positive; 0/8 AL RAST-negative patients had any binding to the latex proteins on PVDF. Sera from all patients were tested in a RAST with a nonammoniated latex extract (NAL), and the results were comparable to the AL RAST. Liquid-phase AL and NAL were comparable in their ability to inhibit the binding of patient's IgE to solid-phase AL and NAL. Sera from 14 RAST-positive patients were tested by immunoblotting with separated, reduced, and nonreduced AL and NAL. All 14 sera demonstrated IgE binding to a 14 kd peptide, which was more pronounced in reduced NAL. These results suggest that the 14 kd peptide in NAL is a major antigen in rubber allergy but that AL is an acceptable antigen source for in vitro diagnostic studies.     

Latex allergy and skin

PURPOSE OF REVIEW: In this review we address the prevalence and outcome of latex allergy in health care workers (HCWs). Recent findings in natural rubber latex (NRL) allergens and trials of specific immunotherapy (SIT) are also of interest. RECENT FINDINGS: A study involving skin prick test (SPT) screening in HCWs in Russia and adjacent countries found a prevalence of latex allergy of 1.9%. Questionnaire studies performed in Wales and in the USA identified prevalence rates of about 0.6%. An intervention undertaken at the Mayo Clinic, in which only gloves with low or undetectable allergen levels were allowed, reduced markedly the incidence of NRL allergy. Two studies, one from Finland and another from Ohio, showed that outcomes in latex-allergic HCWs are generally good. A study involving SPT screening showed that 6% of construction workers had latex allergy. A questionnaire study among allergists practicing in the USA showed that 62% performed latex SPT and 6% reported anaphylaxis, which mostly occurred while using a homemade SPT solution. Hev b 2, Hev b 5, Hev b 6.01 and Hev b 13 produced positive SPT reactions in over 60% of latex-allergic individuals. Topical application of NRL in a murine model of protein contact dermatitis caused a striking increase in prohevein-specific (Hev b 6.01) immunoglobulin E levels, together with a T-helper-2 type dermatitis. A placebo-controlled SIT trial with NRL extract alleviated cutaneous symptoms but caused some systemic reactions in latex-allergic patients. SUMMARY: Low prevalence rates suggest that the peak of the latex allergy epidemic has already passed in HCWs. Hospital-wide interventions requiring use of low-allergen gloves reduce sensitization and changing gloves to nonlatex ones, or even using low-allergen latex gloves, in the affected individuals appears to confer adequate secondary prevention. In the USA there is an urgent need for standardized latex SPT reagent. Hev b 5 and Hev b 6.01 are major in vivo NRL allergens. Findings in mice suggest that NRL proteins eluting from latex gloves may also cause hand eczema in humans. SIT with NRL extract must still be considered an experimental treatment.     

Latex allergy in children

Natural rubber is a component of the latex of the tropical Hevea brasiliensis tree which is widely used in the manufacturing of medical devices and a large variety of articles for everyday use. Over a dozen allergens have been identified in the latex of H. brasiliensis. The allergens Hev b 1, Hev b 3, Hev b 6, and Hev b 7 are proteins that are involved in the biosynthesis of rubber or the coagulation of latex. Allergens that are part of the plant's defense system are represented by Hev b 2 and class I endochitinases. The allergens Hev b 4, Hev b 5, and Hev b 8-10 were classified as either structural or housekeeping proteins. Immediate-type hypersensitivity reactions to proteins present in Hevea latex were first described in 1927. Since then, natural rubber latex (NRL) allergy has become an important medical problem for an increasing number of individuals. Sensitization mainly occurs by wound or mucosal contact with NRL devices during surgery or by inhalation of airborne allergens released from powdered latex gloves. The number of surgical interventions and an atopic disposition are the most important risk factors for developing latex allergy, especially in children with spina bifida. Exposure to NRL products should be carefully avoided for individuals who belong to high-risk groups. Initial studies on establishing a latex-free environment for surgery in all spina bifida patients have reported on a decrease in sensitization and allergy to NRL.     

Latex allergens in glove-powdering slurries

Exposure to airborne glove powder contaminated with latex allergens is known to provoke respiratory symptoms in latex-sensitized individuals. In the commonly used wet-powdering process in glove manufacturing, powder is applied by dipping gloves in a cornstarch suspension, a slurry. The slurry is a potential source of allergen contamination of the powder. The protein and latex allergen contents in five different slurries and in extracts from the corresponding latex gloves were measured using the BCA assay and the IgE antibody inhibition assay (EAI assay). Latex allergens were found in all slurries and gloves. No correlation between the values of protein contents and allergen contents was found. Wet powdering of gloves induces a risk of latex protein contamination of the cornstarch.     

Latex allergy in fruit-allergic patients

The purpose of this study was to investigate the prevalence of latex allergy in fruit-allergic patients, and to assess its clinical significance. Fifty-seven fruit-allergic patients and 50 non-fruit-allergic atopic patient controls were studied. All patients were questioned about conventional immediate symptoms after contact with latex products. Patients also underwent skin prick testing and determination of specific serum IgE to latex, as well as a screening test for environmental allergens. Immunologic latex sensitization occurred in 49/57 (85.9%) fruit-allergic patients, who showed a positive STP and/or CAP to latex, but in only two controls ( P <0.001). Six out of 57 (10.5%) fruit-allergic patients suffered from clinically relevant latex allergy. Symptoms included contact urticaria, angioedema, conjunctivitis, generalized urticaria, and moderate anaphylactic reactions. No control reported symptoms with latex products ( P =0.052). In all patients, clinical symptoms to fruits preceded a history of latex allergy. The fruits most associated were melon, peach, and banana. From our data, we conclude that there is a potential for allergic reactions to latex in patients with allergy to fruit. All patients with fruit allergy should be screened for individual risk of latex allergy.     

Latex immunoassay of transferrin in urine

A fully automated assay based on latex particle agglutination has been developed for the determination of transferrin in urine. The assay consists of incubating urine samples for 30 min at 50 degrees C with latex particles on which an anti-transferrin antibody has been adsorbed and then quantifying the residual unagglutinated particles with an optical particle counter. The measurable concentration range is 0.5-10 micrograms/l. Intra- and interassay coefficients of variation varied from 2.1 to 11.8% and the recovery averaged 102.5% (SD 13.8). Correlation coefficients between transferrinuria and albuminuria were 0.79 in 100 healthy subjects and 0.97 in 90 subjects with established or suspected glomerular involvement. Transferrin and albumin were stable in urine over the pH range 5-9 for 24 h at 37 degrees C, or for 2 weeks at 4 degrees C or room temperature. Transferrin was, however, less stable than albumin during prolonged storage of urine at 4 degrees C. The present latex immunoassay of transferrin may also be adapted to give a turbidimetric reading in which agglutination is quantified by measuring the decrease of absorbance at 360 nm.     

Latex reaction with toxoplasma antigen]

The author describes the latex fixation test (LFT) with Toxoplasma antigen. The main parts of this technique are as follows: the sensibilization of latex particles and incubation of the sensitized particles with sera examined in an icebox (overnight) followed by spinning at 5000 G 10 minutes.--The sera giving negative results with LRT reacted also in 78,3% with complement-fixing test (CFT) in 79.3% and with indirect fluorescent test (IFAT) in 61.8% and with microprecipitating test (MPT) in 100% negatively.--The sera reacting strongly positively with LFT reacted also with CFT in high titers (titer 160 and higher) in 60.9% and in 55% with IFAT (titers 128 and higher).