Mutational analysis of the IgE epitopes in the latex allergen Hev b 5.

BACKGROUND: Hev b 5 is a major latex allergen and potential candidate for an immunotherapy reagent. OBJECTIVE: The purpose of this study was to produce a hypoallergenic form of Hev b 5. METHODS: We used SPOTs analysis with alanine substitution to identify amino acids (AAs) critical for IgE binding and used site-directed mutagenesis to produce recombinant proteins with altered IgE-binding activity. RESULTS: Eleven epitopes were identified (5.1-5.11) in Hev b 5. Individual patients demonstrated variable epitope recognition, with the most intense reactivity to epitopes 5.4 and 5.7. IgE inhibition assays with synthetic peptides indicated that mutating a single epitope would not reduce IgE binding, but rather a combination of epitopes was required. After alanine substitutions to identify the important AAs, site-directed mutagenesis was used to replace the crucial AAs with alanine. Twenty clones with different combinations of altered epitopes were evaluated by means of IgE inhibition assays. Clones with mutations in single epitopes failed to reduce IgE binding, but changes to 8 epitopes (14 AAs) resulted in a 4500-fold reduction in IgE binding. Epitopes 5.7 and 5.9 were found to be cross-reactive, making Hev b 5 a multivalent allergen. CONCLUSIONS: We produced a recombinant Hev b 5 protein with significantly reduced IgE-binding activity. Changing a minimum of 3 immunodominant epitopes was required to cause a 100-fold reduction in IgE binding. Changes in 8 epitopes, particularly the cross-reactive epitopes 5.7 and 5.9, were needed to maximize the reduction in IgE binding. Mutants with reduced IgE-binding activity may prove to be valuable reagents for immunotherapy.

Latex protein: a hidden "food" allergen?

Avoidance of latex allergens is the primary method to prevent adverse reactions. Natural rubber latex is found in many different products in both the health care industry and in modern society, and consequently results in unexpected exposures of sensitized individuals. The use of latex gloves by food handlers provides one potential route for inadvertent exposure to latex allergens. In this study we have used two immunological methods to determine whether latex proteins are transferred to foods following contact with latex gloves. Direct transfer of latex protein to cheese was visualized using a modified immunoblot method. Sliced cheese was touched with a gloved finger. A nitrocellulose membrane was applied to lift the potential fingerprints and a rabbit anti-latex antiserum was used to visualize the transfer of any latex finger-prints. After handling lettuce with gloves, transferred protein was recovered by extracting the lettuce and quantified using an inhibition ELISA for latex proteins. Fingerprints of latex protein were readily detectable on cheese after contact with powdered latex gloves, but not with vinyl gloves. Furthermore, powdered latex glove use resulted in measurable amounts of latex protein on lettuce with an exposure-dependent increase in the latex protein levels. Lettuce alone or lettuce handled with vinyl gloves was negative for latex protein. The use of latex gloves by food handlers is the source of an indirect food additive in the form of latex proteins. It is recommended that food handlers avoid the use of latex gloves to eliminate inadvertent exposure of latex-sensitive individuals.

Detection of immunoglobulin antibodies in the sera of patients using purified latex allergens.

BACKGROUND: Latex allergy is largely an occupational allergy due to sensitization to natural rubber latex allergens present in a number of health care and household products. Although several purified allergens are currently available for study, information on the usefulness of these purified, native or recombinant allergens in the demonstration of specific immunoglobulin (Ig) E in the sera of patients is lacking. OBJECTIVE: To evaluate the purified latex allergens and to demonstrate specific IgE antibody in the sera of health care workers and spina bifida patients with clinical latex allergy. METHODS: Two radioallergosorbent and an enzyme-linked immunosorbent assay (ELISA) using latex proteins Hev b 1, 2, 3, 4, 6 and 7 along with two glove extracts and Malaysian nonammoniated latex (MNA) were evaluated to demonstrate IgE in the sera of health care workers and spina bifida with latex allergy and controls with no history of latex allergy. RESULTS: ELISA using the purified latex allergens demonstrated specific IgE in 32-65% health care workers and 54-100% of spina bifida patients with latex allergy. The corresponding figures for RAST were 13-48 and 23-85 for RAST-1 and 19-61 and 36-57 for RAST-2. These results were comparable with the results obtained with glove extracts and crude rubber latex proteins. CONCLUSIONS: When used simultaneously, latex proteins Hev b 2 and Hev b 7 reacted significantly with specific serum IgE in 80% of health care workers and 92% of spina bifida patients with latex allergy by ELISA technique, while this combination gave lower positivity when the RASTs were used. By the addition of Hev b 3, specific IgE was detected in all spina bifida patients with latex allergy. Both RASTs failed to show specific IgE in the control subjects, while the ELISA showed significant latex-specific IgE in 22% of controls.

Unique and shared IgE epitopes of Hev b 1 and Hev b 3 in latex allergy.

Of the several latex proteins cloned and expressed, the rubber elongation factor, Hev b 1, and the closely related Hev b 3, represent two major allergens associated with latex allergy. Although both allergens demonstrated IgE binding with sera from latex allergic patients, it was not known whether these two molecules shared any epitopes. Hence, in the present study using health care workers (HCW) and spina bifida (SB) patients with latex allergy, we investigated the IgE binding epitopes in Hev b 1 and Hev b 3. Recombinant Hev b 1 and Hev b 3 were expressed in a prokaryotic expression system, while overlapping decapeptides of Hev b 1 and Hev b 3 were synthesized on derivatized cellulose membrane. Eight IgE binding epitopes for Hev b 1 and eleven for Hev b 3 were identified using sera from latex allergic patients with SB. On further analysis of synthetic peptides encompassing these epitopes, similar IgE antibody reactivity was demonstrated with three Hev b 1 epitopes b1E3, b1E5, b1E6 and two Hev b 3 epitopes; b3E10 and b3E 11. For Hev b 1, a unique IgE binding epitope was identified in the region of amino acid residues 16-25. In competitive ELISA, peptides bIE2 and bIE4 together inhibited 58% of IgE binding of Hev b 1, while b3E5 showed 22% inhibition in the IgE binding of Hev b 3. The results of the present study suggest that the understanding of linear and conformational IgE epitopes in the major latex allergens may provide better insight into the structure-function relationship of the allergens, and may lead to the development of better patient care and management strategies in latex allergy.

Molecular and immunologic characterization of new isoforms of the Hevea brasiliensis latex allergen hev b 7: evidence of no cross-reactivity between hev b 7 isoforms and potato patatin and proteins from avocado and banana.

BACKGROUND: Hev b 7 is a Hevea brasiliensis latex allergen with sequence identities of 39% to 42% to patatins recently identified as potato allergens. The complementary DNAs encoding 2 different Hev b 7 isoforms were previously reported. OBJECTIVE: The aim of this study was to determine the sequence variation of Hev b 7 and to compare the IgE reactivity of individual isoforms in vitro and in vivo. A further objective was to evaluate possible cross-reactivities between Hev b 7 and patatins and proteins from banana and avocado. METHODS: An H brasiliensis lambda ZAP complementary DNA (cDNA) library was screened with use of a Hev b 7 cDNA probe. Four Hev b 7 isoforms were produced in recombinant form and their IgE-binding capacities were compared. IgE immunoblot inhibitions and ELISA inhibition assays were used to investigate the possible cross-reactivity between Hev b 7 and recombinant potato patatin and proteins from avocado and banana. RESULTS: Two new isoforms, S2 and D2, were identified by sequencing 32 cDNA clones with full-length coding regions. All 4 recombinant isoforms displayed esterase activity and identical IgE-binding capacities. The new isoforms S2 and D2 were evaluated in skin prick tests and provoked responses equivalent to natural Hev b 7. No cross-reactivity was observed between Hev b 7 isoforms and potato patatin and proteins from avocado and banana. CONCLUSIONS: All 4 recombinant Hev b 7 isoforms have equivalent IgE-binding capacity and therefore represent suitable reagents for the development of in vitro and in vivo diagnostic tests. Hev b 7, patatins, and their homologs appear not to contribute to cross-reactivity in the latex-fruit syndrome.

IgE antibody response to vertebrate meat proteins including tropomyosin.

BACKGROUND: Although meat is a main source of proteins in western diets, little information is available regarding allergy to vertebrate meats or the allergens implicated in these reactions. OBJECTIVE: To evaluate the in vitro IgE antibody response to different vertebrate meats in suspected meat-allergic subjects, as well as the possible role of tropomyosin in meat allergy and to analyze the cross-reactivity between vertebrate meats and the effect of heating on the IgE-binding to meat proteins. METHODS: Fifty-seven sera from suspected meat-allergic subjects were tested by grid blot to extracts of beef, lamb, pork, venison, chicken, and turkey and to four mammalian tropomyosins of different origins. RESULTS: Meat-allergic subjects have IgE antibodies to proteins in different mammalian meats (43/57 subjects); cross-reactivity with avian meat was limited: less than 50% (19/43) of meat positive sera reacted to chicken. In contrast, most of the poultry-positive sera also reacted to different mammalian meats. In general, there was stronger IgE reactivity to raw meats in comparison to cooked meats; an exception was six cases in which IgE reactivity to cooked poultry was stronger. Weak IgE reactivity to tropomyosin was detected in only 2/57 sera tested. CONCLUSIONS: Suspected meat-allergic subjects have serum IgE directed to meat proteins. In vitro cross-reactivity among mammalian meats appears to be important, while cross-reactivity to poultry is limited indicating mammalian-specific proteins. Although cooking in general denatures meat proteins rendering them less allergenic, in some cases the process of cooking may result in the formation of new allergenic moieties. The muscle protein tropomyosin is not an important vertebrate meat allergen.

The efficacy and safety of fexofenadine HCl and pseudoephedrine, alone and in combination, in seasonal allergic rhinitis.

BACKGROUND: Antihistamines effectively treat seasonal allergic rhinitis (SAR), although the ability of this drug class to reduce nasal congestion is limited. Nasal decongestants effectively treat nasal congestion but not the histamine-related components of SAR. Therefore antihistamine/nasal decongestant combinations are commonly used to maximize the treatment of SAR. Fexofenadine HCl is a nonsedating, long-acting H1 receptor antagonist that provides fast and effective relief from SAR. It is well tolerated, with no sedative or cardiotoxic effects. OBJECTIVE: We sought to compare the efficacy and safety of a fexofenadine HCl/pseudoephedrine HCl combination with that of each individual component in the treatment of ragweed allergy. METHODS: In this Canadian multicenter, double-blind, parallel-group study, 651 patients allergic to ragweed were randomized to receive 60 mg of fexofenadine HCl twice daily, 120 mg of sustained-release pseudoephedrine HCl twice daily, or a combination of the 2 drugs (60 mg of fexofenadine HCl/120 mg of sustained-release pseudoephedrine HCl) twice daily for 2 weeks. Efficacy analyses were based on symptom severity. In addition, a health economic assessment was performed. RESULTS: Combination therapy was significantly more effective than pseudoephedrine alone in improving primarily histamine-mediated symptoms (sneezing; rhinorrhea; itchy nose, palate, and/or throat; and itchy, watery, red eyes) and significantly more effective than fexofenadine alone in reducing nasal congestion. Combination therapy also produced greater improvements in daily activities and work productivity compared with the individual components. No serious adverse events were reported in any of the treatment groups. In addition, no clinically significant changes in 12-lead electrocardiogram parameters, vital signs, or clinical laboratory values were observed. CONCLUSION: Combination therapy is more effective than fexofenadine alone or pseudoephedrine alone in relieving the full spectrum of SAR symptoms (ie, both the primarily histamine-related symptoms and nasal congestion).

Human IgE-binding epitopes of the latex allergen Hev b 5.

BACKGROUND: Hev b 5 is an acidic protein (isoelectric point, 3.5) rich in glutamic acid with 9 repeated amino acid (AA) sequences of XEEX or XEEEX. Although its function in Hevea brasiliensis is unknown, Hev b 5 has been identified as a major latex allergen. Immunoblot inhibition studies suggest Hev b 5 exists as multiple isoforms or contains a common epitope found in several other proteins. OBJECTIVE: The purpose of this study was to further characterize Hev b 5 and to identify linear IgE-binding epitopes. METHODS: Octapeptides spanning the entire Hev b 5 protein were synthesized on a derivatized cellulose membrane. The membrane was reacted with sera pooled from health care workers allergic to latex or rabbits immunized with latex proteins. B-cell epitopes were identified by subsequent incubations with the appropriate secondary antibodies and detected by using chemifluorescence. RESULTS: Sera from patients allergic to latex recognized 6 IgE-binding regions located throughout the molecule. Two epitopes (2 and 4) had the common AA sequence of KTEEP. Epitopes 3 and 5 had a similar AA sequence of EEXXA, where X was P, T, or K. Epitopes 1 and 6 appeared to be unrelated to the other epitopes. Database analysis could not identify other proteins with similar sequences. Neither of the XEEEX sequences bound IgE. Control sera failed to react to any peptides. CONCLUSIONS: Hev b 5 exists as multiple isoforms, but only small amounts are present in the nonammoniated latex preparations, such as those used for diagnostic tests, and this may help to explain the relatively poor sensitivity of some in vitro tests.

The role of infection in atopic dermatitis.

explain this tendency to develop infections. A decrease in the number and function of CD8+ suppressor/cytotoxic T cells from peripheral blood of AD patients has been reported.2 This could explain the increased incidence of cutaneous viral and fungal infections observed in these patients. Monocytes from AD patients secrete increased levels of interleukin (IL)-10 that can inhibit T cell mediated responses.3 Leukocytes from patients with AD have been found to produce decreased amounts of interferon gamma (IFN-g),4 which is required for the

Latex sensitization: occupational versus general population prevalence rates.

BACKGROUND: Natural rubber latex (NRL) has become an important occupational health concern in recent years, particularly among health care workers. It has been suggested in some reports that the prevalence of latex sensitization among occupationally exposed groups is not different from that in the general population. METHODS: The findings of prevalence studies conducted among occupationally-exposed and general population groups were reviewed to determine whether there is evidence to support this suggestion. RESULTS: Numerous surveys of HCWs have demonstrated that the prevalence of sensitization to latex ranged in most studies from 5 to 12%; sensitization of HCWs may produce clinical effects including urticaria, rhinoconjunctivitis, occupational asthma, and potentially life-threatening anaphylactic shock. More than a decade ago, data from Finland indicated that the prevalence of latex allergy in the general population was less than 1%. Recent reports from Finland have confirmed this, with observations that 0.7-1.1% of large series of patients were NRL-allergic, while among 804 unselected patients, the prevalence of latex skin prick test (SPT) positivity was 0.12%. In contrast, other studies have suggested that from 4 to 6.4% of individuals tested were positive for serum latex-specific IgE antibodies. However, the specificity of these assays has been reported to be low. In three recent studies based on SPTs, published in 1997, the prevalence of positive reactions to latex was about 1% or less. The prevalence was 0.7% (95% CI 0.3-1.4) among 758 apprentices in Quebec, Canada; and 1.1% among more than 3,000 children tested in Finland (1.0% confirmed on latex use test). There were no first- and second-year dental students with positive latex SPTs in Ontario, Canada. CONCLUSIONS: These recent investigations provide further evidence consistent with earlier studies based on skin testing that the prevalence of latex sensitization in occupationally-unexposed groups is quite low (< 1%). The marked differences in the findings based on serological assays may relate to the nonspecificity of these assays and deserve further investigation.

Purified and recombinant latex proteins stimulate peripheral blood lymphocytes of latex allergic patients.

BACKGROUND: Natural rubber latex proteins have been implicated in severe allergy in individuals exposed to latex products, particularly health care workers. Until recently, only crude antigens were available to study the immune response in these patients. In recent years a number of relevant allergens have been purified, but few have been used in lymphocyte studies. Hence, to better understand the immunological mechanisms involved in latex allergy, we investigated the response of peripheral blood mononuclear cells (PBMCs) to various purified natural rubber latex allergens. METHODS: Using conventional protein purification methods and gene cloning, we have obtained 6 natural rubber latex proteins. We studied allergen-specific IgE levels and PBMC responses to these allergens along with 3 crude latex antigen preparations. RESULTS: Of the 28 latex-allergic health care workers studied, 16 reacted to one or more of the allergens studied, but PBMCs from controls failed to respond to these antigens. Serum IgE to the antigens was detected in 11-90% of the patients. CONCLUSION: Fifty-seven percent of the latex-allergic patients demonstrated PBMC responses to at least one of the latex allergens tested, but there was no direct correlation between serum IgE levels and PBMC responses. However, since none of the control subjects showed any PBMC stimulation, this may prove useful in determining sensitization to latex. Among the allergens studied, the predominant mononuclear cell responses were directed against Hev b 2, while serum IgE against rHev b 6 was demonstrable in the greatest number of patients. The crude latex allergens were toxic to PBMCs and hence, the purified allergens may be of greater value in demonstrating sensitization of patients to latex allergens.

Cloning and characterization of a latex allergen (Hev b 7): homology to patatin, a plant PLA2.

We previously identified a 46-kD protein allergen in latex as having amino acid sequence homology to the patatin gene family. The objective of this study was to characterize this protein by molecular techniques. RNA was isolated from the latex or leaf material from Hevea brasiliensis and from potato tubers. Specific polymerase chain reaction (PCR) primers were designed from the amino acid sequence and reverse transcriptase (RT)-PCR amplified a specific product from latex RNA that was subsequently cloned and sequenced. This product was 1493 bp in length with an 1167 bp open reading frame. The deduced amino acid sequence encodes for a 389 aa protein, pI 4.82 with 43% homology to tobacco patatin. Northern analysis of potato, Hevea leaf, and latex RNA demonstrated the message to be most abundant in latex, weakly present in Hevea leaf, but no hybridization occurred with potato RNA. Patatin has lipid acyl-transferase and PLA2-like activity, suggesting it plays a role as a defence-related protein. Other defence-related proteins in latex such as hevein, glucanase, and hevamine are also allergens. Increased production of defence-related proteins as a result of increased tapping of the rubber trees to meet the demand for latex may explain the increased allergenicity of latex.

Latex allergy in operating room nurses.

OBJECTIVE: To determine the prevalence of allergy to natural rubber latex and potential crossreacting foods in operating room nurses. METHOD: Two hundred forty-seven operating room nurses completed a latex allergy questionnaire. They were questioned about symptoms of latex reactivity and about other allergies particularly to foods that may crossreact with latex. Informed consent was obtained and skin prick testing was performed with natural rubber latex and five latex extracts representing low (0.08 to 0.25 microgram/mL) and high (18 to 106 micrograms/mL) natural rubber latex protein gloves. Skin prick tests were done with four potentially crossreacting foods (banana, avocado, kiwi, and potato), saline, and histamine controls. RESULTS: One hundred thirty-five (54.7%) nurses described allergic symptoms they attributed to latex exposure. Of these 12 (4.9%) tested positive to latex extracts alone, 12 (4.9%) tested positive to food extracts alone, and 5 (2.0%) tested positive to both latex and crossreactive foods. Three of the 17 (17.6%) nurses testing positive to latex gave no history of reactivity to latex. Indirect latex ELISA was done on the serum of skin test-positive patients with a 70.6% sensitivity. CONCLUSION: Of the nurses tested, 6.9% had positive skin prick tests to latex extracts; 17.6% of these were asymptomatic and 29.4% had associated food positive skin prick tests.

Incidence of latex sensitization among latex glove users.

BACKGROUND: Although there are several reports of the prevalence of latex sensitization among health care workers, the incidence of sensitization is unknown. OBJECTIVE: The objective of this study was to estimate the incidence of sensitization among latex glove users at a hospital in Hamilton, Ontario, Canada. METHODS: Workers with negative results to the skin test at baseline were followed prospectively over 1 year, some wearing powdered gloves and others using powder-free gloves. They were reevaluated in 1995 with a questionnaire and skin prick test (SPT) sensitivity to latex reagents, three common inhalants, and six foods. A conversion was defined as a (new) latex SPT with wheal diameter at least 4 mm greater than saline control. Glove extracts were assayed for antigenic protein, and air samples were obtained to estimate exposure to airborne latex protein. RESULTS: During powdered glove use, personal exposures ranged from 5 to 616 ng/m3, whereas during powder-free glove use, all but two results for air samples were below the limit of detection (about 0.1 ng/m3). During the study period, the protein concentration in the powdered gloves, initially mean 557 microg/gm of sample, declined at a rate of 295 microg/gm per year (p < 0.0001). Of the 1075 SPT-negative participants at baseline, 479 were working in eligible wards, and of these, 435 (91%) participated in follow-up, 227 using powder-free gloves and 208 using powdered gloves. We identified four conversions, two (1.0%) in the powdered glove group and two (0.9%) in the powder-free group. The two participants using powdered gloves were the only converters who were symptomatic. The significance of skin test conversions identified in the powder-free group, both asymptomatic patients, is unclear. The limitations of the study are discussed, including the limited power, the declines in latex protein concentrations, and the possibility of information (observer) bias. CONCLUSION: To our knowledge, this represents the first reported estimate (about 1%) of incidence of sensitization in hospital personnel using latex gloves.

Latex allergy: epidemiological study of 1351 hospital workers.

OBJECTIVE: To determine the prevalence of latex sensitisation among a large group of healthcare workers, study the occupational and non-occupational factors associated with latex allergy, and characterise latex exposure in air and by gloves. METHODS: All 2062 employees of a general hospital in Hamilton, Ontario, Canada who regularly used latex gloves were invited to participate in a cross sectional survey, representing the baseline phase of a prospective cohort morbidity study. Attempts were made to recruit employees who were diagnosed with latex allergy before the survey. Glove extracts were assayed for antigenic protein, and area and personal air samples were obtained on two occasions (summer and winter) to estimate exposure to airborne latex protein. A questionnaire on medical and occupational information was administered by an interviewer. Skin prick tests were performed with latex reagents, three common inhalants, and six foods. RESULTS: The mean (SD) latex protein concentrations were 324 (227) micrograms/g in powdered surgical gloves and 198 (104) micrograms/g in powdered examination gloves. Personal latex aeroallergen concentrations ranged from 5 to 616 ng/m3. There was a total of 1351 (66%) participants. The prevalence of positive latex skin tests was 12.1% (95% confidence interval (95% CI) 10.3% to 13.9%). This prevalence did not vary by sex, age, hospital, or smoking status but subjects who were latex positive were significantly more likely to be atopic (P < 0.01). Participants who were latex positive were also significantly more likely to have positive skin tests to one or more foods (Mantel-Haenszel odds ratio (OR) adjusted for atopy 12.1, 95% CI 7.6 to 19.6, P < 10(-9)). Work related symptoms were more often reported among latex positive people, and included hives (OR 6.3, 95% CI 3.2 to 12.5), eye symptoms (OR 1.9, 95% CI 1.2 to 2.8), and wheezy or whistling chest (OR 4.7, 95% CI 2.8 to 7.9). The prevalence of latex sensitivity was highest among laboratory workers (16.9%), and nurses and physicians (13.3%). When the glove consumption per healthcare worker for each department was grouped into tertiles, the prevalence of latex skin test positivity was greater in the higher tertiles of glove use for sterile (surgical) gloves (P < 0.005) but not for examination gloves. CONCLUSIONS: In this large, cross sectional study of healthcare workers, the prevalence of latex sensitisation was 12.1% (9.5% among all those eligible), and there were significant associations with atopy, positive skin tests to certain foods, work related symptoms, and departmental use of gloves per healthcare worker. This cohort is being followed up prospectively and will be retested to determine the incidence of development of latex sensitivity.

IgE epitope analysis of the hevein preprotein; a major latex allergen.

We have previously identified the hevein preprotein as a common allergen for latex allergic healthcare workers. The B cell epitopes in the hevein protein that are recognized by IgE of latex-allergic individuals have not been identified. In this study, we examined the hevein preprotein using epitope mapping. Overlapping synthetic peptides of 10 amino acids (two aa overlap) were synthesized on a derivatized cellulose membrane using Fmoc chemistry. The peptide spots were probed with pooled sera from 10 latex-allergic patients, and the IgE-reactive peptides identified with anti-IgE MoAbs. We identified six B cell epitopes within the full length hevein preprotein which bound IgE from latex-allergic patients. Two were located in the N-terminal 5-kD hevein domain and four were observed in the 14-kD C-domain. A broad epitope was located between the N-terminal amino acids 13-24. This epitope had nearly complete homology to wheat germ agglutinin (WGA). Immunological cross-reactivity to WGA was confirmed by Western blot analysis with purified WGA, and this reactivity could be inhibited by latex proteins or WGA. Of the five remaining epitopes, four had homologies to other proteins in the pathogenesis-related family of plant proteins (PR-4). The data demonstrate that hevein has multiple IgE epitopes. The significant homology of these epitopes to a broad family of plant defence proteins further explains the increased prevalence of food allergies in latex-allergic individuals.

Latex sensitivity in dental students and staff: a cross-sectional study.

BACKGROUND: Dental practitioners, like other health care providers who regularly use latex gloves, are at increased risk for latex sensitivity. They are also at risk for irritant or allergic contact dermatitis. OBJECTIVE: This study was carried out to determine the prevalence of latex sensitivity and possible risk factors in staff and students of a Faculty of Dentistry. METHODS: A cross-sectional study was performed by using a questionnaire and allergy skin prick testing. RESULTS: Two hundred three students and staff members completed the questionnaire. Five percent reported asthma symptoms on exposure to rubber products, 13% reported symptoms of rhinitis or conjunctivitis, and 17% reported pruritus or urticaria within minutes of exposure to rubber. Overall, 10% of 131 subjects who underwent skin prick tests had a positive response to natural rubber latex. Among the students tested, there were increasing percentages of positive skin test responses to latex with increasing years of study (0% of Year 1 and 2 students tested; 6% of Year 3; and 10% of Year 4). Positive responses were seen as early as Year 3 in students (in their second year of clinical activity and glove use). Positive skin prick test responses to latex were related to a personal history of atopy (p = 0.005), positive prick test responses to common allergens (p < 0.005), latex-attributed immediate pruritus or urticaria (p < 0.05), rhinoconjunctivitis (p < 0.001), and asthma symptoms (p < 0.001). CONCLUSION: Dental school students and faculty are at high risk for latex sensitization. This occurs as early as the second year of glove use. Overall prevalence of skin sensitization was 10% of those tested. Preventive strategies in this group merit further investigation.

New developments in latex allergy.

There are several new developments in studies of latex allergy. It appears that many of the allergens to latex are defense proteins that the plant uses to respond to pathogens. Rubber elongation factor, hevein preprotein, hevamine, patatin, and glucanase have been identified as allergic proteins. In addition, processing and leaching of natural rubber latex devices results in a very low allergen content. Powdered rubber gloves appear to be a major contributor to airborne latex allergens. The replacement of low allergen-containing latex gloves for high allergen-containing gloves markedly reduces the levels of latex allergens in the clinical setting. By decreasing the inhalation and contact with latex allergens, we would expect a reduction in latex sensitization in the hospital.

IgE from latex-allergic patients binds to cloned and expressed B cell epitopes of prohevein.

Prohevein is one of the major allergens associated with latex allergy. In the present study, we identified IgE binding regions of prohevein, and expressed multiple IgE binding epitopes by selective cloning. These truncated polypeptides were then used to demonstrate IgE in the sera of patients. Decapeptides of prohevein were synthesized on derivatized cellulose membrane with an offset of one amino acid. The IgE reactivity of these linear peptides was evaluated separately using pooled sera from latex-allergic health care workers (HCW) and spina bifida (SB) patients. A total of 10 IgE binding epitopes representing unique as well as shared epitopes from both the N- and C-domains of the prohevein were identified. Recombinant polypeptides were constructed based on the identified epitopes, and clones carrying DNA fragments were overexpressed. These recombinant peptides were evaluated for IgE binding with sera from HCW, SB, and normal individuals. Recombinant prohevein, hevein, and the C-domain exhibited IgE binding in 84, 88, and 40% of HCW sera, respectively, as against reactivity of 84% with crude latex allergens. However, only 48% of the sera from SB patients showed IgE binding with recombinant prohevein, while 56 and 28% had reactivity with recombinant N- and C-domains, respectively. Among the three remaining recombinant peptides of the C-domain, only CA44-103 showed IgE binding with SB patients. The results of the present study suggest that linear IgE epitope analysis and construction of recombinant peptides increase the sensitivity and specificity of the immunodiagnosis of latex allergy and provide more information on the immunopathogenesis of hypersensitivity reaction mediated by type I allergy.