Natural rubber latex allergens: new developments

Improving Deproteinization in Colombian Latex from Hevea brasiliensis: A Bibliometric Approximation

Natural Rubber Field Latex (NRFL) allergens restrict its use in some markets due to health-threatening allergic reactions. These molecules are proteins that are related to asymptomatic sensitization and hypersensitivity mediated by immunoglobulin E (IgE). Although NRFL allergens have been investigated since the 1980s, there are still gaps in knowledge regarding the development of deproteinized natural rubber (DPNR). Therefore, in this study, the deproteinization of NRFL from the lower basin of the Cauca River, Antioquia-Colombia was evaluated using eight systems. The highest removal value was 84.4% and was obtained from the treatment containing SDS (Sodium dodecyl sulfate), Urea, and Ethanol. It was also possible to determine that at high concentrations of SDS, removal percentages higher than 70% are reached. On the other hand, all deproteinizing systems decreased NRFL Zeta potentials without self-coagulation, suggesting enhanced colloidal stability in DPNR latex. On the other hand, the bibliometric analysis presented technological advances in DPRN through different parameters and bibliometric networks. The analysis presented makes an important contribution from the bibliometric approach that could be positive for the development of research on DPNR.

Diagnostic value of the ISAC(®) allergy chip in detecting latex sensitizations

PURPOSE

Latex allergy can be diagnosed by different test methods such as IgE quantification, Western blot, cellular antigen stimulation test (CAST), and in vivo methods [e.g. skin prick test (SPT)]. Phadia provides two modern methods using recombinant latex allergens: ImmunoCAP(®) and the Immuno Solid-phase Allergen Chip (ISAC(®)), which enables simultaneous determination of specific IgE against five latex allergens. We compared the diagnostic sensitivity of the ISAC(®) test kit and the conventional Hev b 5-spiked ImmunoCAP(®) latex extract.

METHODS

Forty sera were sampled from subjects with suspected natural rubber latex (NRL) allergy. These patients had positive SPT to NRL extract, positive NRL Western blots, and positive results in the CAST. All sera were analysed using the ISAC(®) and recombinant NRL ImmunoCAP(®) allergens and compared to the results of 20 negative control sera.

RESULTS

Only 22 of the 40 subjects (55 %) showed positivity to at least one latex allergen on the ISAC(®) (sensitivity ISAC(®) 55 %). The sensitivity of the ImmunoCAP(®) latex extract was 70 %. The most frequently detected sensitization was against Hev b 6.01 (n = 12). When the serum samples were tested with all recombinant ImmunoCAP(®) allergens, three additional sensitizations against latex could be detected compared to the ISAC(®).

CONCLUSIONS

Microarrays do offer many potential benefits such as elegant simultaneous determination of sensitizations against different NRL allergens with minimal amounts of serum. However, a negative NRL test result should be regarded with caution and at least be confirmed by other in vitro methods.

Primary prevention of latex allergy in healthcare-spectrum of strategies including the European glove standardization

IgE-mediated allergy to natural rubber latex was first noted from rubber gloves in 1979. The initial reports in dermatological journals described contact urticarial reactions; later, severe generalized allergic reactions and asthma were documented. A considerable proportion of the people involved in medical and dental care were found to be sensitized to latex. This article describes and surveys a broad range of primary prevention measures at the local and national levels. Examples are given from paediatrics, dental education, and medical care. National strategies and position papers on latex allergy are presented in which medical professionals, manufacturers and public authorities have cooperated. Special reference is paid to the European work to standardize medical gloves, which led to document EN 455:3.

Microarray based IgE detection in poly-sensitized allergic patients with suspected food allergy - an approach in four clinical cases

BACKGROUND

Component-resolved diagnosis and microarray technology have been recently introduced into clinical allergy practice, and may be particularly useful in poly-sensitized allergic patients.

METHODS

We compare the clinical usefulness of a microarray-based IgE detection assay (ISAC(®)) with skin tests and specific IgE with standard allergens (sIgE) or their monocomponents in four case reports of patients poly-sensitized to aeroallergens and food.

RESULTS

Case 1: a woman with rhinitis, oral allergy syndrome to several fruits and anaphylaxis to cherry. Diagnostic tests supported non-specific lipid transfer proteins (nsLTPs) primary sensitization. Case 2: a woman with exercise-induced asthma, rhino-conjunctivitis and oral allergy syndrome to fresh fruits of different families. A diagnosis of primary grass and weed pollen allergy with profilin and pathogenesis-related protein family 10 (PR-10) cross-reactive food allergy was proposed. Case 3: a man with atopic eczema, asthma, rhinitis, and multiple anaphylactic episodes with cashew nuts and oral allergy syndrome to fruits. The diagnostic workup supported a primary birch pollen allergy with PR-10 and nsLTPs cross-reactive food allergy. Case 4: a woman with rhino-conjunctivitis, per-operative anaphylaxis due to latex and recent pharyngeal angio-oedema episodes. The diagnosis was a primary grass and weed pollen allergy with equivocal profilin sensitization and no obvious cross-reactivity mediated by nsLTPs sensitization.

CONCLUSIONS

The possibility to carry out multiple sIgE measurements with single protein allergens, in particular with the microarray technique, is a useful, simple and non-invasive diagnostic tool in complex poly-sensitized allergic patients.

Diagnostic value of specific IgE analysis in latex allergy

BACKGROUND

The precision of the methods used to diagnose latex allergy is of great importance due to false-positive results. Neither the skin prick test (SPT) nor the latex-specific IgE assay has 100% diagnostic accuracy. We analysed the diagnostic value of latex-specific IgE by the first-ever concomitant use of the SPT and nasal provocation test (NPT).

METHODS

Twenty-seven latex-sensitive patients (group 1), 46 aeroallergen-sensitive patients (group 2a) and 33 healthy subjects (group 2b) participated in the study. All groups underwent an SPT with latex and aeroallergens and an NPT with latex. Latex-specific IgE and total IgE levels were measured by the ImmunoCAP assay.

RESULTS

Latex-specific IgE was positive in 92.6, 30.4 and 9.1% of groups 1, 2a and 2b, respectively. The 11 aeroallergen-sensitive patients in group 1 and all of the patients in group 2a were predominantly sensitised to pollens (grass, weed and tree) and reacted to a lesser degree to house dust mite, moulds and animal dander. Combined pollinosis was remarkably more prevalent in patients with positive latex-specific IgE in group 2a than in those with negative latex-specific IgE (p = 0.001). The NPT was positive in 84.6% of group 1 and negative in all control subjects. The sensitivity, specificity, negative predictive value and positive predictive value of the latex-specific IgE assay were 90.9, 72.2, 96.3 and 50%, respectively.

CONCLUSION

The high rate of false-positive results for latex-specific IgE by ImmunoCAP should be taken into account when making a diagnosis of latex allergy in patients with pollinosis, especially in those sensitised to more than one pollen species.

Latex allergy

Allergy to natural rubber latex is an important clinical condition that occurred after the institution of universal precautions to protect healthcare workers. A rapid increase and production of both examination and surgical gloves resulted in an epidemic of allergy to latex protein. Healthcare workers in both the medical and dental environments, as well as specific groups of individuals including those with spina bifida, myelodysplasia, and food allergies (banana, kiwi, avocado, and others), were at increased risk of sensitization. Clinical symptoms in the latex allergic individual ranged from type I hypersensitivity reaction including rhinoconjunctivitis, asthma, and systemic reaction to type IV hypersensitivity reaction, which occur from the chemicals added during the manufacturing process. Diagnosis of latex allergy is based on a clinical history that correlates the development of symptoms in relationship to exposure. In the United States there are no skin tests approved by the Food and Drug Administration. Therefore a combination of clinical judgment and serologic testing such as ImmunoCAP and Immulite is helpful. The primary treatment of latex allergy is avoidance of exposure to the latex protein.

Pitfalls in the diagnosis of latex allergy

BACKGROUND

Screening patients for latex allergy prior to surgery is an important but intensive procedure. The appropriate testing strategy for diagnosing latex (Hevea brasiliensis) allergy involves in-vitro specific IgE or skin prick testing. The sensitivity and specificity of both tests are influenced by patient-specific factors or manufacturing processes that alter the clinically relevant allergens in skin testing solutions.

METHODS

Total IgE and latex-specific IgE testing was introduced as a screening test. Skin prick testing was done on patients with a high probability of latex allergy and negative specific IgE with total IgE <100 kU/L. SDS-PAGE was done on the non-ammoniated latex (NAL) and newly introduced ammoniated latex (AL) reagents for the clinically relevant allergens.

RESULTS

51 patients had a total IgE <100 (range, 2.8-99.0 kU/L), and 10% had a positive skin test. 60% of positive skin tests would have been missed with lower total IgE cut-offs of 50 kU/L (6% of referrals). SDS-PAGE of the NAL solution showed 3 prominent bands with molecular weights of approximately 20, 24 and 42 kDa that correlated with Hev b 6, Hev b 3 and Hev b 7/13, respectively. In contrast, the AL solution showed 3 very faint higher molecular weights bands that did not correlate with clinically relevant antigens.

CONCLUSIONS

Increasing the cut-off value of total IgE for allergen-specific IgE testing increased the sensitivity of the specific IgE test. The NAL reagent had a greater number of clinically significant allergens at higher concentrations than AL, which may have implications for the clinical sensitivity of the newer AL reagent.

Molecular allergology approach to allergic diseases in the paediatric age

Identification, characterization, and purification of allergens are essential for the structural and immunologic studies needed to understand how these molecules induce specific IgE antibody production by the human immune system. Advances in molecular biology techniques have led to the production of recombinant allergens having constant properties, allowing detection of specific IgE directed against different molecular components of an allergenic source. Presence of homologous allergens in different sources is the reason for cross-reaction. Molecule-based diagnostic tools can lead to better interpretation of poly-sensitizations, observed by ST and in vitro tests using allergenic extracts as they were made before. Some examples IgE sensitization to major genuine allergens and panallergens will be presented.

Mapping of IgE-binding epitopes on the major latex allergen Hev b 2 and the cross-reacting 1,3beta-glucanase fruit allergens as a molecular basis for the latex-fruit syndrome

Nine distinct IgE-binding epitopes were identified along the entire amino acid sequence of the major latex allergen Hev b 2 (1,3beta-glucanase) using a set of synthetic 15-mer peptides frameshifted by 3 residues immobilized on cellulose membrane (Spot technique). Most of the amino acid residues building these IgE-binding epitopic regions are nicely exposed on the surface and the epitopes usually correspond to charged regions on the molecular surface of the protein. A smaller number of 5 IgE-binding epitopic areas was identified on the banana 1,3beta-glucanase, which exhibits a very similar overall conformation and charge distribution. The latter epitopes might be responsible for the IgE-binding cross-reactivity currently observed in the latex-fruit syndrome. Using rabbit polyclonal IgG anti-BanGluc as a probe instead of IgE from allergic patients the same epitopic regions were identified in both Hev b 2 and BanGluc. Additionally, surface-exposed regions with a very close conformation were predicted to occur on Ole e 9, the 1,3beta-glucanase allergen identified in olive pollen.

Interference of cross-reactive carbohydrates in the determination of specific IgE in alcohol drinkers and strategies to minimize it: the example of latex

BACKGROUND

Cross-reactive carbohydrate determinants (CCDs) are N-glycans in plant and invertebrate proteins that interfere with specific IgE determinations. The prevalence of IgE to Man2XylFucGlcNAc2 (MUXF), the CCD from bromelain, may be increased in heavy drinkers.

OBJECTIVE

To further investigate the relationship of alcohol consumption to CCD specific IgE. Latex was used as an example for investigating CCD interference with in vitro allergy testing and how to minimize the interference by using nonglycosylated recombinant allergens and inhibition assays.

METHODS

We determined the levels of IgE to CCD markers (MUXF and ascorbate oxidase) and natural rubber latex in 270 adults without a history of latex allergy (73 abstainers or occasional drinkers, 76 light drinkers, 47 moderate drinkers, and 74 heavy drinkers). In cases with latex reactivity, we performed inhibition assays with MUXF and screened for IgE to a panel of recombinant latex allergens. Fourteen-day serologic follow-up was available for a subset of individuals.

RESULTS

Moderate to heavy drinkers displayed an increased prevalence of IgE to CCD markers. The presence of CCD specific IgE was closely associated with latex IgE reactivity. Inhibition studies and the absence of reactivity to nonglycosylated recombinant latex allergens indicated CCD interference in latex IgE determinations. Serum levels of specific IgE decreased with alcohol abstention.

CONCLUSIONS

In this population, alcohol consumption is associated with an increased prevalence of IgE reactivity to natural rubber latex due to CCD interference. The use of nonglycosylated recombinant allergens and inhibition assays may help to minimize CCD interference in populations in which IgE to CCDs is common.

Latex allergy: a model for therapy

Allergy to natural rubber latex products emerged as an important clinical condition following an increase in the use of latex gloves for barrier protection in the early 1980s. In addition to latex glove users, other high-risk groups with different latex exposure include spina bifida patients and others with multiple surgical procedures. Subjects with fruit and vegetable allergy are also at risk due to cross-reactive allergens. Following the significant advances in the identification and characterization of common aeroallergens, latex allergy was well placed to become an excellent model of therapy. Awareness of latex allergy and modes of sensitization enabled epidemiological studies to inform allergen avoidance initiatives, substantially reducing inadvertent exposure in major hospitals in Western countries. Spina bifida is often identified in utero or soon after birth, allowing vigorous latex allergen avoidance with enhanced efficacy of primary prevention. However, changing demographics of latex allergy and technological revolution in countries such as China and India are predicted to unleash a second wave of latex allergy reemphasizing the incentive for improved manufacturing procedures for latex products. The desirable high tensile strength and elasticity of natural rubber latex have made the commercial identification of good alternatives very difficult but this would also be attractive for primary prevention. In addition, an effective specific immunotherapy regimen would be valuable for selected high-risk atopic individuals. Current subcutaneous and sublingual immunotherapy schedules have been tested for treatment of latex allergy with evidence of efficacy but the risks of adverse events are high. For such potent allergens as latex, hypoallergenic but T cell-reactive preparations are required for clinical use. Identification of allergenic components of latex products, with generation of monoclonal antibodies and recombinant allergens, allowed sequence determination and mapping of T cell and B cell epitopes. Together, these reagents and data facilitated improved diagnostics and investigation of novel-specific therapeutics. Potential hypoallergenic latex preparations identified include modified non-IgE-reactive allergen molecules and short T cell epitope peptides. The co-administration of adjunct therapies such as anti-IgE or corticosteroids and of appropriate adjuvants for induction of regulatory T cell response offers promise for clinically effective, safe latex-specific vaccines.

Quantitative analysis of immunoglobulin E reactivity profiles in patients allergic or sensitized to natural rubber latex (Hevea brasiliensis)

BACKGROUND

Characterized native and recombinant Hevea brasiliensis (rHev b) natural rubber latex (NRL) allergens are available to assess patient allergen sensitization profiles.

OBJECTIVE

Quantification of individual IgE responses to the spectrum of documented NRL allergens and evaluation of cross-reactive carbohydrate determinants (CCDs) for more definitive diagnosis.

METHODS

Sera of 104 healthcare workers (HCW; 51 German, 21 Portuguese, 32 American), 31 spina bifida patients (SB; 11 German, 20 Portuguese) and 10 Portuguese with multiple surgeries (MS) were analysed for allergen-specific IgE antibody (sIgE) to NRL, single Hev b allergens and CCDs with ImmunoCAP technology.

RESULTS

In all patient groups rHev b 5-sIgE concentrations were the most pronounced. Hev b 2, 5, 6.01 and 13 were identified as the major allergens in HCW and combined with Hev b 1 and Hev b 3 in SB. In MS Hev b 1 displayed an intermediate relevance. Different sIgE antibody levels to native Hevea brasiliensis (nHev b) 2 and rHev b 6.01 allowed discrimination of SB with clinical relevant latex allergy vs. those with latex sensitization. Sensitization profiles of German, Portuguese and American patients were equivalent. rHev b 5, 6.01 and nHev b 13 combined detected 100% of the latex-allergic HCW and 80.1% of the SB. Only 8.3% of the sera showed sIgE response to CCDs.

CONCLUSIONS

Hev b 1, 2, 5, 6.01 and 13 were identified as the major Hev b allergens and they should be present in standardized latex extracts and in vitro allergosorbents. CCDs are only of minor relevance in patients with clinical relevant latex allergy. Component-resolved diagnostic analyses for latex allergy set the stage for an allergen-directed immunotherapy strategy.

Allergen concentration in natural rubber latex

BACKGROUND

Hevea brasiliensis latex serum is commonly used as the in vivo and in vitro reference antigen for latex allergy diagnosis as it contains the full complement of latex allergens.

OBJECTIVE

This study quantifies the concentrations of the significant allergens in latex serum and examines its suitability as an antigen source in latex allergy diagnosis and immunotherapy.

METHODS

The serum phase was extracted from centrifuged latex that was repeatedly freeze-thawed or glycerinated. Quantitation of latex allergens was performed by two-site immunoenzymetric assays. The abundance of RNA transcripts of the latex allergens was estimated from the number of their clones in an Expressed Sequence Tags library.

RESULTS

The latex allergens, Hev b 1, 2, 3, 4, 5, 6, 7 and 13, were detected in freeze-thawed and glycerinated latex serum at levels ranging from 75 (Hev b 6) to 0.06 nmol/mg total proteins (Hev b 4). Hev b 6 content in the latex was up to a thousand times higher than the other seven latex allergens, depending on source and/or preparation procedure. Allergen concentration was reflected in the abundance of mRNA transcripts. When used as the antigen, latex serum may bias the outcome of latex allergy diagnostic tests towards sensitization to Hev b 6. Tests that make use of latex serum may fail to detect latex-specific IgE reactivity in subjects who are sensitized only to allergens that are present at low concentrations.

CONCLUSION

Latex allergy diagnostics and immunotherapy that use whole latex serum as the antigen source may not be optimal because of the marked imbalance of its constituent allergens.

Latex allergy within a cohort of not-at-risk subjects with respiratory symptoms: prevalence of latex sensitization and assessment of diagnostic tools

BACKGROUND

Immunoglobluin E (IgE)-mediated hypersensitivity to natural rubber latex (NRL) is a major problem in allergy practice. Currently, the use of skin prick tests (SPTs) with latex extracts and specific IgE detection for the diagnosis of NRL allergy in suspected patients is directed to identification of risk factors. Many cases of NRL allergy remain undiagnosed due to misreporting of symptoms by the patients or lack of proper questions asked by the physician.

MATERIALS AND METHODS

A total of 6,126 subjects referred for respiratory symptoms underwent SPTs with NRL. Positive subjects were resurveyed for exposure to NRL, and specific IgE for NRL extracts and recombinant molecules was determined. Immunoblots of NRL extracts were performed to identify IgE patterns.

RESULTS

Forty-six of 3,930 sensitized subjects had a positive SPT with NRL, displaying a prevalence of NRL sensitization of 0.75% for the general and 1.2% for the sensitized population. Eleven out of 46 (23.9%) subjects could be defined as NRL asymptomatic, whereas 35 (76.1%) developed symptoms upon exposure to NRL. Specific IgE to NRL was detected for 22 (75.86%) of 29 tested sera. Seventeen out of 22 (77%) sera displayed specific IgE to recombinant allergens with most reactions to Hev b 5, Hev b 6.01 and Hev b 6.02. Immunoblots of NRL extract fractions with patients' sera showed heterogeneous patterns.

CONCLUSIONS

SPTs with NRL extract should be routinely performed in patients with respiratory symptoms. Hev b 5, Hev b 6.01 and Hev b 6.02 are the most important allergens, but further characterization of NRL extracts is needed to identify novel allergens and to clarify the role of crossreactive carbohydrate determinants.

Latex specific IgE: performance characteristics of the IMMULITE 2000 3gAllergy assay compared with skin testing

BACKGROUND

In the absence of a US Food and Drug Administration (FDA)-cleared latex skin testing reagent, in vitro tests remain important for the diagnosis of latex allergy.

OBJECTIVE

To evaluate the performance characteristics of IMMULITE 2000 3gAllergy (Immulite), a third-generation, FDA-cleared, continuous random-access immunoanalyzer, for the quantification of latex specific IgE.

METHODS

Stored serum samples (N = 201) from patients classified as having positive or negative latex puncture skin test results were measured for latex specific IgE levels using Immulite, and these data were compared with historical results from 3 second-generation, FDA-cleared IgE antilatex assays (AlaSTAT [Ala], AutoCAP [CAP], and HY*TEC enzyme immunoassay [HT]).

RESULTS

The diagnostic performances of the CAP, Ala, and Immulite assays (> or = 0.35 kU/L cutoff value) were equivalent in sensitivity and specificity (P > .05). The HT assay (> or = 0.05 kU/L cutoff value) was more sensitive and less specific (P < .05). Immulite (> or = 0.10 kU/L cutoff value) had greater sensitivity than Ala and CAP and greater specificity than HT (P < .05 for both). Diagnostic efficiency was greater for Immulite than for CAP, Ala, and HT (P < .05).

CONCLUSIONS

The Immulite system is superior in diagnostic performance, especially at the 0.10 kU/L or greater cutoff level, for the diagnosis of latex allergy compared with older, second-generation assays. Immulite still misclassifies 15.5% of puncture skin test-positive individuals as negative for latex specific IgE. Compared with second-generation assays, Immulite represents a technological advance, with enhanced speed and less operator intervention.

Structural analysis of the glycoprotein allergen Hev b 4 from natural rubber latex by mass spectrometry

The lecithinase homolog (Hev b 4) from Hevea brasiliensis (Q6T4P0_HEVBR) is an important natural rubber latex allergen. Hev b 4 is a highly glycosylated protein and its carbohydrate moiety has been implicated in the binding of IgE from natural rubber latex allergic patients. The cDNA for Hev b 4 has recently been cloned and sequenced. Here, we have analyzed the post-translational modifications of natural Hev b 4 by liquid chromatography/electrospray ionization-mass spectrometry of tryptic peptides. Seven of the eight potential glycosylation sites were found to be occupied. One site, however, was only partially glycosylated. Asn224 was substituted by complex type N-glycans with fucose and xylose, whereas all other sites carried either oligomannose glycans or a mixture of oligomannose and complex N-glycans. Glycosylation site Asn308, the most C-terminal one of the eight sites, was only found in the non-glycosylated form. The complex type N-glycans apparently form the molecular basis for the immune reaction with patients' sera. A large fraction of Hev b 4 molecules contains two or more complex N-glycans and thus a physiological reaction against these polyvalent allergens on the basis of the carbohydrate is in theory possible. Aside from allowing glycosylation analysis, the mass spectrometric data defined the N-terminal cleavage site of Hev b 4. This study once more demonstrates the outstanding analytical potential of electrospray ionization-mass spectrometry coupled with liquid chromatographic separation.

Advances in development of hypoallergenic latex immunotherapy

PURPOSE OF REVIEW

The characterization of clinically relevant latex allergens and the production of recombinant allergens is now well advanced, but this knowledge needs to be translated into new strategies for the safe and effective specific treatment of latex allergic diseases including asthma and anaphylaxis.

RECENT FINDINGS

The current status of latex allergy is discussed indicating a changing demographic paradigm. A new wave of latex allergy is emerging outside the healthcare setting with the widespread use of latex products. An increased prevalence in developing countries is also reported. Limited studies on current specific immunotherapy for latex allergy are reviewed, confirming the feasibility but demonstrating an unacceptable risk of adverse events. The characterization of latex allergens and the identification of B and T-cell epitopes point to rational strategies for the generation of hypoallergenic preparations for specific immunotherapy. Results to date for latex allergens are reviewed, including recombinant, chemical modification and synthetic peptide approaches. Candidate hypoallergenic preparations for targeting sensitization to the major allergens Hev b 1, Hev b 3, Hev b 5 and Hev b 6.01 have been identified. Further investigations of optimal regimens for the delivery of specific immunotherapy to induce regulatory T-cell function are warranted.

SUMMARY

The findings point to the selection of suitable hypoallergenic preparations for clinical trials of effective and safe latex allergy immunotherapy.

Identification of Hevamine and Hev b 1 as Major Latex Allergens in Taiwan

BACKGROUND

Proteins from latex gloves have been documented to trigger occupational latex allergy among health care workers. Allergen characterization of latex glove extract has never been studied in Taiwan. This study aimed to identify allergenic proteins from latex gloves.

METHODS

Crude extracts of latex gloves were prepared with phosphate-buffered saline and 20 medical workers with a history of latex allergy were enrolled in this study. The specific IgE antibody was determined by the Pharmacia CAP system and in-house enzyme-linked immunoassay and immunoblotting. The target proteins were excised from two-dimensional PAGE and analyzed by electrospray ionization tandem mass spectrometry.

RESULTS

Immunoblotting of glove extracts revealed three IgE-binding proteins at a molecular mass of 45, 30 and 14 kDa. Peptide mass fingerprinting revealed that the protein at 45 kDa, which was recognized by 10% (2/20) of atopic sera tested, was an allergenic lipolytic esterase from Hevea brasiliensis (Hev b 13). The 30- and 14-kDa proteins, which were recognized by 55% (11/20) and 85% (17/20) of patients' sera, were found to be hevamine and rubber elongation factor (Hev b 1), respectively.

CONCLUSIONS

Our results indicated that hevamine and Hev b 1 are the major allergens from latex gloves in Taiwan, which differs from the reports in Western countries.

Molecular cloning and immunoglobulin E reactivity of a natural rubber latex lecithinase homologue, the major allergenic component of Hev b 4

BACKGROUND

Hev b 4 is an allergenic natural rubber latex (NRL) protein complex that is reactive in skin prick tests and in vitro immunoassays. On SDS-polyacrylamide gel electrophoresis (SDS-PAGE), Hev b 4 is discerned predominantly at 53-55 kDa together with a 57 kDa minor component previously identified as a cyanogenic glucosidase. Of the 13 NRL allergens recognized by the International Union of Immunological Societies, the 53-55 kDa Hev b 4 major protein is the only candidate that lacks complete cDNA and protein sequence information.

OBJECTIVE

We sought to clone the transcript encoding the Hev b 4 major protein, and characterize the native protein and its recombinant form in relation to IgE binding.

METHODS

The 5'/3' rapid amplification of cDNA ends method was employed to obtain the complete cDNA of the Hev b 4 major protein. A recombinant form of the protein was over-expressed in Escherichia coli. The native Hev b 4 major protein was deglycosylated by trifluoromethane sulphonic acid. Western immunoblots of the native, deglycosylated and recombinant proteins were performed using both polyclonal antibodies and sera from latex-allergic patients.

RESULTS

The cDNA encoding the Hev b 4 major protein was cloned. Its open reading frame matched lecithinases in the conserved domain database and contained 10 predicted glycosylation sites. Detection of glycans on the Hev b 4 lecithinase homologue confirmed it to be a glycoprotein. The deglycosylated lecithinase homologue was discerned at 40 kDa on SDS-PAGE, this being comparable to the 38.53 kDa mass predicted by its cDNA. Deglycosylation of the lecithinase homologue resulted in the loss of IgE recognition, although reactivity to polyclonal rabbit anti-Hev b 4 was retained. IgE from latex-allergic patients also failed to recognize the non-glycosylated E. coli recombinant lecithinase homologue.

CONCLUSION

The IgE epitopes of the Hev b 4 lecithinase homologue reside mainly in its carbohydrate moiety, which also account for the discrepancy between the observed molecular weight of the protein and the value calculated from its cDNA.

Occupational allergens in dentistry

PURPOSE OF REVIEW

Dental professionals and their physicians frequently do not recognize, accurately diagnose or appropriately manage occupational allergies. Dental allergen identification, diagnostics and practical avoidance strategies are summarized in this review.

RECENT FINDINGS

Methacrylates, natural rubber latex proteins, rubber glove allergens, and glutaraldehyde are the predominant allergens in dentistry. Reactions range from cell-mediated contact allergy to urticaria and occupational asthma.

SUMMARY

Despite recent advances in allergen characterization and increased awareness of selected allergens, treatment of occupational allergies can be improved. Better information and improved cooperation between dental workers and their clinicians is needed.

Toxicological and immunological aspects of occupational latex allergy

Latex allergy continues to be an important occupational health problem as latex products are used increasingly worldwide, particularly in healthcare. Although there are few epidemiological studies on the incidence of latex allergy, there has been an increase in the number of case reports over the last 10 years and, based on skin-prick tests, estimates of prevalence of latex allergy in healthcare workers range from 2% to 17%. The allergic health effects arise either from the latex proteins, generally causing a type I immediate hypersensitivity reaction, or from the chemicals added to latex during processing, causing a type IV delayed hypersensitivity reaction. Clinical manifestations of latex allergy depend on the route of exposure and occur by direct contact either with skin or mucosa, or by inhalation. The diagnosis of latex allergy is based on the history, skin tests, serological tests and challenge tests. Thirteen latex allergens have been identified and isolated so far from natural rubber latex. They differ in their potential to elicit immunological responses in individuals allergic to latex and thus have been designated as major or minor allergens. In latex gloves, cornstarch powder used as a donning agent carries latex proteins, thereby increasing inhalational and mucosal exposure to latex proteins. There also appears to be a positive correlation between protein content and allergenicity of gloves. The use of powder-free, low-protein gloves is effective in reducing symptoms and markers of sensitisation. Alternatives to latex gloves, such as nitrile or vinyl gloves are available but may be inferior in respect to manual dexterity and biological impermeability.

Hypoallergenic variants of the major latex allergen Hev b 6.01 retaining human T lymphocyte reactivity

Hev b 6.01 is a major allergen of natural rubber latex with sensitization of 70-86% of latex glove-allergic subjects. Recently, we mapped the immunodominant T cell sites of Hev b 6.01 to the highly IgE-reactive hevein (Hev b 6.02) domain. Hev b 6.01 contains 14 cysteine residues with multiple disulphide bridges stabilizing tertiary conformation. With the goal of a standardized specific immunotherapy we developed hypoallergenic Hev b 6.01 mutants by site-directed mutagenesis of selected cysteine residues (3, 12, 17, and 41) within the Hev b 6.02 domain. Peptides corresponding to the Hev b 6.02 domain of two of the mutants were also synthesized. These mutants and peptide variants showed markedly decreased or ablated latex-allergic patient serum IgE binding by immunoblotting and ELISA. Basophil activation testing confirmed markedly decreased activation with successive cysteine substitutions of the mutants and complete abrogation with the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide. Retention of T cell reactivity is crucial for effective specific immunotherapy and all mutants and peptide variants maintained their latex-specific T cell reactivity. The ablated allergenicity but retained T cell reactivity of the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide suggests this peptide is a suitable candidate for inclusion in a latex immunotherapy preparation.

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.