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

[Hevea brasiliensis como fuente alergénica: revisión bibliográfica]

Abstract

La planta Hevea brasiliensis se utiliza ampliamente en la industria como fuente de extracción de caucho, un elemento empleado en diversas áreas comerciales y médicas. Los estudios inmunológicos de esta especie indican que es una fuente alergénica importante, que puede provocar sensibilización y alergia. Se han identificado diferentes componentes alergénicos de esta planta, con diversas propiedades inmunitarias y bioquímicas, y estudiado más de diez tipos diferentes de alérgenos, cada uno con distinta capacidad de inducir síntomas alérgicos. En esta revisión informamos los avances actuales en el estudio de Hevea brasiliensis.

Hevea latex-associated allergies: piecing together the puzzle of the latex IgE reactivity profile

Introduction: IgE-mediated Hevea latex allergy and associated food-allergies constitute a significant health issue with serious consequences of diagnostic error. Hence, there is a need for more reliable confirmatory diagnostics.Areas covered: Here, we summarize the major limitations of conventional tests using native extracts and describe how piecing together the IgE reactivity profile can benefit correct diagnosis in difficult cases in whom conventional tests yield equivocal or negative results. A diagnostic algorithm integrating traditional sIgE and component-resolved diagnosis (CRD) is presented.Expert opinion: Moreover, it is clear that the discoveries in the field of the Hevea latex proteome will contribute to our understandings and accurate approach of sometimes complex cross-reactivity phenomena that extend beyond the 'latex-fruit syndrome.'

Identification and practical management of latex allergy in occupational settings

Allergy to natural rubber latex (NRL) from Hevea brasiliensis is a relevant occupational health hazard. The use of gloves and products manufactured with latex and environmental allergen exposure in the work environment are risks factors for the development of occupational allergy among different job categories. Healthcare workers have been the most commonly affected, but other professions with exposure to latex products such as hairdressers, cleaners, food handlers and those making natural rubber latex (NRL) products are also at risk of developing occupational allergy. Clinical manifestations of IgE-mediated latex allergy can range from troublesome skin disorders to life-threatening systemic reactions. It is very important to identify the occupational allergic diseases in their early stages in order to implement avoidance strategies. For this purpose, the interventions for prevention should emphasize the importance of latex allergy awareness and surveillance among exposed workforces.

Molecular allergy diagnosis: status anno 2015

IgE antibodies play a key role in type I allergic reactions. Today, different in vitro immunoassays for allergen-specific IgE antibodies are available. However, some major issues should be taken into account for correct interpretation of specific IgE (sIgE) antibody results, as these assays do not demonstrate absolute positive and negative predictive values. Therefore, additional diagnostic tests are needed to make the correct diagnosis. During the last two decades significant progress in biochemistry and molecular biology enabled the detection and quantification of sIgE antibodies to allergen protein components and epitope-emulating peptides, also called molecular allergy diagnosis or component resolved diagnosis (CRD). In contrast to conventional sIgE antibody assays, molecular allergy diagnosis makes it possible to discriminate between genuine allergy and merely sensitisation, to establish personalized sensitization patterns and to assess the individual risk of severity of an allergic reaction and finally it helps us to predict the natural course. In this review the use of CRD in inhalant, food, latex and hymenoptera venom allergy will be discussed. The primary focus will be on the most relevant clinical applications of CRD rather than to describe all the currently available allergen components and epitopes. Appropriate experience of our own research group is provided.

Current overview of allergens of plant pathogenesis related protein families

Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environmental conditions like UV irradiation and insect or fungal attacks express these proteins constitutively. These proteins are mostly resistant to proteases and most of them show considerable stability at low pH. Many of these plant pathogenesis related proteins are found to act as food allergens, latex allergens, and pollen allergens. Proteins having similar amino acid sequences among the members of PR proteins may be responsible for cross-reactivity among allergens from diverse plants. This review analyzes the different pathogenesis related protein families that have been reported as allergens. Proteins of these families have been characterized in regard to their biological functions, amino acid sequence, and cross-reactivity. The three-dimensional structures of some of these allergens have also been evaluated to elucidate the antigenic determinants of these molecules and to explain the cross-reactivity among the various allergens.

Circulating human basophils lack the features of professional antigen presenting cells

Recent reports in mice demonstrate that basophils function as antigen presenting cells (APC). They express MHC class II and co-stimulatory molecules CD80 and CD86, capture and present soluble antigens or IgE-antigen complexes and polarize Th2 responses. Therefore, we explored whether human circulating basophils possess the features of professional APC. We found that unlike dendritic cells (DC) and monocytes, steady-state circulating human basophils did not express HLA-DR and co-stimulatory molecules CD80 and CD86. Basophils remained negative for these molecules following stimulation with soluble Asp f 1, one of the allergens of Aspergillus fumigatus; Bet v 1, the major birch allergen; TLR2-ligand or even upon IgE cross-linking. Unlike DC, Asp f 1-pulsed basophils did not promote Th2 responses as analyzed by the secretion of IL-4 in the basophil-CD4⁺ T cell co-culture. Together, these results demonstrate the inability of circulating human basophils to function as professional APC.

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.

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.

Latex allergy: low prevalence of immunoglobulin E to highly purified proteins Hev b 2 and Hev b 13

BACKGROUND

Hevea brasiliensis (Hev b) 2 and Hev b 13 have recently been identified as major latex allergens by detecting specific IgE antibodies in >50% of sera from Hev b latex-allergic individuals.

OBJECTIVE

We assessed the prevalence rates for sensitization to extensively purified latex allergens in patients from three diverse geographical areas.

METHODS

Native Hev b 2, Hev b 5, Hev b 6.01 and Hev b 13 were purified by non-denaturating chromatography and were used in ELISAs to assess sera from 215 latex-allergic patients and 172 atopic non-sensitized controls from Finland, Spain and the United States to detect allergen-specific IgE antibodies.

RESULTS

Unexpectedly, even highly purified Hev b 13 contained epitope(s) to which Hev b 6-specific human IgE antibodies bound effectively. Further purification, however, reduced the prevalence of IgE antibody reactivity to low levels: 15%, 5% and 11% for Hev b 2, and 18%, 30% and 27% for Hev b 13 among latex-allergic Finnish, Spanish and American patients, respectively. Interestingly, Finnish patients had a lower prevalence of Hev b 5-specific IgE antibody (28%) as compared with Spanish (49%) and American (71%) patients. The prevalence of Hev b 6.01-specific IgE reactivity was uniformly >50% in all three populations.

CONCLUSION

Neither Hev b 2 nor Hev b 13 appear to be major latex allergens when evaluated in serological assays using highly purified allergens. The reason(s) for the observed differences in published sensitization rates in various geographic regions requires further study. The purity of the allergen preparations has a marked impact on the accuracy of latex-specific IgE antibody detection in epidemiological studies and in the serological diagnosis of latex allergy.

Percutaneous reactivity to natural rubber latex proteins persists in health-care workers following avoidance of natural rubber latex

BACKGROUND

Long-term avoidance of natural rubber latex [Hevea brasiliensis (Hev b)] is currently recommended for health-care workers (HCWs) with established natural rubber latex (NRL) allergy. Percutaneous sensitivity to eight Hev b NRL allergens was evaluated in HCWs in 2000. To date, no studies have evaluated the longitudinal effects of NRL avoidance on percutaneous sensitivity to NRL allergens.

OBJECTIVE

The aims of this study were to evaluate changes in percutaneous reactivity to non-ammoniated latex (NAL) and NRL allergens in HCWs 5 years after a recommendation to avoid NRL and to evaluate factors that predict the persistence of in vivo sensitivity to NAL and NRL allergens.

METHODS

Skin prick testing was performed with NAL, seven NRL allergens (Hev b 1, 2, 3, 4, 6.01, 7.01, and 13), and recombinant Hev b 5 (rHev b 5) in 34 HCWs who were initially evaluated in 2000 for occupationally related NRL allergy. Serial 10-fold dilutions of NAL and NRL allergens were employed in skin testing. Sera from the HCWs were assayed for latex and enhanced latex (rHev b 5-enriched allergosorbent)-specific IgE antibodies using the ImmunoCAP assay.

RESULTS

The prevalence of work-related symptoms significantly decreased between 2000 and 2005 with avoidance of NRL (P<0.05). A >/=100-fold reduction in percutaneous sensitivity to Hev b 2 and Hev b 7 was less likely in those with prior history of systemic reactions to NRL (P=0.0053), reported history of reaction to cross-reactive foods (P=0.014), continued local reactions to NRL gloves (P<0.0001), or high NRL glove exposure since the initial study (P=0.0075). The diagnostic sensitivity and specificity of the latex-specific IgE serology was 54% and 87.5%, respectively, in comparison with NAL skin tests. The addition of rHev b 5 to the ImmunoCAP (enhanced latex) allergosorbent altered the diagnostic sensitivity and specificity of the ImmunoCAP to 77% and 75%, respectively.

CONCLUSION

While symptoms may resolve quickly with NRL avoidance therapy, detectable IgE indicating continued sensitization remains beyond 5 years, and thus continued avoidance of NRL should be recommended.

Crystallization and identification of the glycosylated moieties of two isoforms of the main allergen Hev b 2 and preliminary X-ray analysis of two polymorphs of isoform II

Latex from Hevea brasiliensis contains several allergenic proteins that are involved in type I allergy. One of them is Hev b 2, which is a beta-1,3-glucanase enzyme that exists in different isoforms with variable glycosylation content. Two glucanase isoforms were isolated from trees of the GV-42 clone by gel filtration, affinity and ion-exchange chromatography. Isoform I had a carbohydrate content of about 20%, with N-linked N-acetyl-glucosamine, N-acetyl-galactosamine, fucose and galactose residues as the main sugars, while isoform II showed 6% carbohydrate content consisting of N-acetyl-glucosamine, fucose, mannose and xylose. Both isoforms were crystallized by the hanging-drop vapour-diffusion method. Isoform I crystals were grown using 0.2 M trisodium citrate dihydrate, 0.1 M Na HEPES pH 7.5 and 20%(v/v) 2-propanol, but these crystals were not appropriate for data collection. Isoform II crystals were obtained under two conditions and X-ray diffraction data were collected from both. In the first condition (0.2 M trisodium citrate, 0.1 M sodium cacodylate pH 6.5, 30% 2-propanol), crystals belonging to the tetragonal space group P4(1) with unit-cell parameters a = b = 150.17, c = 77.41 A were obtained. In the second condition [0.2 M ammonium acetate, 0.1 M trisodium citrate dihydrate pH 5.6, 30%(w/v) polyethylene glycol 4000] the isoform II crystals belonged to the monoclinic space group P2(1), with unit-cell parameters a = 85.08, b = 89.67, c = 101.80 A, beta = 113.6 degrees. Preliminary analysis suggests that there are four molecules of isoform II in both asymmetric units.

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.

Generation of Allergen-Enriched Protein Fractions of Hevea brasiliensis Latex for in vitro and in vivo Diagnosis

BACKGROUND

The latex of Hevea brasiliensis trees contains a complex proteome that includes a range of allergenic proteins. Current latex extracts that are used for the diagnosis of latex allergy still lack important allergens. We aimed to devise a production process for an improved reagent that would ideally contain the complete latex allergome.

METHODS

Latex C-serum was fractionated by ammonium sulfate precipitation, and B- and C-serum proteins were then separated by anion exchange chromatography. Proteins eluting within defined salt concentration ranges were pooled into six final fractions. Fractions were evaluated by two-dimensional electrophoresis and subsequent IgE immunoblot for their spectrum of allergens. The presence of the most important latex allergens in the fractions was checked by Western blot analyses. Each fraction was further evaluated by skin prick test (SPT).

RESULTS

Reproducibility of the preparation method was demonstrated with two batches of latex. Comparison of latex B- and C-serum to the six fractions showed a remarkable increase in the number of detectable allergens in the fractions. The presence of the latex allergens Hev b 1-8 and Hev b 13 in the fractions was demonstrated. In SPTs, the fractions produced wheal-and-flare reactions comparable to commercial latex extracts.

CONCLUSIONS

This method provides reproducible latex protein fractions of high allergen content for the diagnosis of latex allergy.

The immuno cross-reactivity of gutta percha points

OBJECTIVE

The purpose of this study is to test the postulated immuno cross-reactivity between proteins derived from raw gutta percha (RGP), gutta percha point (GPP) and natural rubber latex (NRL).

METHODS

Antigenicity and cross-reactivity of proteins were determined by the FITkit (FITBiotech, Finland) and ELISA inhibition assays.

RESULTS

Antigenicity of proteins derived from RGP or GPP was not demonstrated. Except for NRL glove extracts, neither extracts from RGP or GPP were reactive in ELISA inhibition assay.

SIGNIFICANCE

There is no immunologic cross-reactivity in vitro between proteins derived from RGP or GPP, and from NRL gloves. Thus, therapeutic use of GPP is unlikely to initiate adverse immuno-reactivity in individuals previously sensitized to NRL proteins.

Latex allergen IgE assays in the assessment of Veterans Affairs health care workers

BACKGROUND

A previous multicenter study of Veterans Affairs health care workers evaluated hospital participants for latex hypersensitivity. Well-defined groups from that study allowed us to explore the diagnostic utility of newer antilatex allergen IgE immunoassays in the present study.

OBJECTIVES

To determine whether an enhanced CAP (ENHCAP) assay or an enzyme-linked immunosorbent assay (ELISA) identifies latex glove symptomatic individuals with antilatex allergen IgE that had not been detected by the CAP assay used in the original study and to determine the specificity of the ENHCAP assay.

METHODS

The ELISA measured IgE antibody to Malaysian nonammoniated natural rubber latex extract (MNA), Hev b1, Hev b5, and Hev b6. Four patient groups were tested: confirmed latex glove allergic, latex glove symptomatic, latex glove sensitized/asymptomatic, and latex glove nonallergic.

RESULTS

The ENHCAP assay and the MNA ELISA were highly concordant with the original CAP assay. In the subgroup with latex glove symptoms that were previously negative by the CAP assay, the ENHCAP assay value was elevated in 7 (11%) of 64 samples, only 3 of which were class 2 or higher. The MNA ELISA result was positive in only 4 (6%) of these 64 samples, and 3 of these were fractionally above the cutoff value for this assay.

CONCLUSIONS

The ENHCAP assay and the MNA ELISA identified a few additional positive individuals in the group that was latex glove symptomatic and originally CAP assay negative. The ENHCAP assay and the MNA ELISA produced only a modest improvement in diagnostic sensitivity over that of the original CAP assay.

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.

Specific IgE response to purified and recombinant allergens in latex allergy

Background

In recent years, allergy to natural rubber latex has emerged as a major allergy among certain occupational groups and patients with underlying diseases. The sensitization and development of latex allergy has been attributed to exposure to products containing residual latex proteins. Although improved manufacturing procedures resulted in a considerable reduction of new cases, the potential risk for some patient groups is still great. In addition the prevalent cross-reactivity of latex proteins with other food allergens poses a major concern. A number of purified allergens and a few commercial kits are currently available, but no concerted effort was undertaken to evaluate them.

Methods

We studied 11 purified latex allergens, Hev b 1 to Hev b 10, and Hev b 13 along with several crude allergen extracts and two commercial ImmunoCAP assays to evaluate specific IgE antibody in the sera from latex allergic patients and controls. Health care workers and spina bifida patients with clinical symptoms of latex allergy, spina bifida patients without latex allergy, and non-atopic health care workers have been studied.

Results

The results suggest that Hev b 2, 5, 6, and 13 together identified over 80 percent health care workers with latex allergy, while Hev b 6 along with Hev b 1 or 3 detected specific IgE antibody in all sera studied from patients with spina bifida and latex allergy. The ImmunoCAP results using both Hev b 5 amplified and non-amplified closely agreed with the clinical diagnosis of latex allergy in health care workers and in spina bifida.

Conclusion

Although the purified allergens and crude extracts reacted diversely with IgE from different patient groups, the results indicated that use of certain combinations of purified recombinant antigens will be useful in commercial kits or in in-house assays for detecting specific IgE antibody in the sera. The results suggest that a combination of Hev b 2, 3, 5, 6, and 13 together detected specific IgE in 80% of the sera from latex allergic patients. Both ImmunoCAPs correctly identified over 95% of latex allergic patients, however, showed reactivity with a few normal control subjects

Hevea brasiliensis latex allergens: current panel and clinical relevance

Latex allergy has been studied in detail in Europe and the US over the past two decades, resulting in specific guidelines that succeeded in reducing its incidence in high-risk populations within the medical field. How these developments have affected high-risk populations outside the health care scenario is an important unanswered question. In addition, a second wave of latex allergy may occur in nations that are striving to attain higher economic and technologic standards, including population-dense countries such as China. Therefore, the application of Hevea allergens in novel diagnostic assays and the development of specific latex immunotherapy will provide new opportunities for latex allergy research. In this review, we summarize current knowledge on the immunological properties of the 13 officially accepted Hevea brasiliensis latex allergens.

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.

Natural rubber latex allergens: new developments

PURPOSE OF REVIEW

New allergenic latex proteins have been identified, whereas further information on known latex allergens has emerged in recent years. Although prevalence figures for sensitization to the various latex allergens have been published in several studies in the past, the data have not been collated to facilitate cross-comparison.

RECENT FINDINGS

Salient characteristics of the three most recently identified latex allergens, Hev b 11, 12 and 13 are described, whereas new findings on some of the previously recognized allergens are examined. Hev b 2 is viewed from the standpoint of allergenicity and protein glycosylation, Hev b 4 in relation to its biochemical identity and molecular cloning, Hev b 5 with respect to its recombinant form, and Hev b 6 in connection with conformational IgE epitopes. Reports on sensitization or allergic reaction to purified latex allergens from recent and past work are summarized. The use of latex allergens in latex allergy diagnostics is reviewed and discussed.

SUMMARY

Thirteen latex allergens have been recognized by the International Union of Immunological Societies. Based on the results of published studies, native Hev b 2, recombinant Hev b 5, native or recombinant Hev b 6, native Hev b 13, and possibly native Hev b 4 are the major allergens relevant to latex-sensitized adults. Although there is an increasing tendency to identify and characterize latex allergens largely on the basis of their recombinant forms, not all such recombinant proteins have been fully validated against their native counterparts with respect to clinical significance.

Isolation and characterization of the early nodule-specific protein homologue (Hev b 13), an allergenic lipolytic esterase from Hevea brasiliensis latex

Recurring reports of a highly allergenic 42-46-kDa protein in Hevea brasiliensis latex appeared to have been resolved with the discovery of a 43-kDa allergenic latex protein that was a homologue to patatin. However, the low to moderate prevalence of sensitization to the protein, designated Hev b 7, among latex-allergic patients could not adequately explain the frequent observations of the 42-46-kDa allergen. This led to the hypothesis that another, more allergenic protein of a similar molecular mass existed in Hevea latex. We report the isolation and purification of a 42.98-kDa latex glycoprotein showing homology to the early nodule-specific protein (ENSP) of the legumes Medicago sativa, Medicago truncatula, and Glycine max. The protein is allergenic, being recognized by immunoglobulin E (IgE) in sera from latex-allergic patients. The IgE epitope resides on the carbohydrate moiety of the protein, and the presence of a similar carbohydrate component on potato tuber patatin enables the latter to inhibit IgE binding to the ENSP homologue. The cDNA encoding the ENSP homologue was isolated by reverse transcription-PCR and cloned. The protein predicted from the cDNA sequence has 391 amino acids, the first 26 of which constitute a putative signal peptide. The deduced molecular mass of the mature protein is 40.40 kDa, while its isoelectric point is estimated at 5.0. The discrepancy between the predicted and observed molecular mass might be due to glycosylation, for which three N-sites on the protein are predicted. The purified protein showed lipase and esterase activities and may be involved in plant defense.

Latex allergy

The prevalence of IgE mediated natural latex rubber allergy is estimated to be < 1% in the general population, < 17% in medical personnel and approximately 0% in children with spina bifida. We review the definition, diagnosis, prevention, and treatment of NLR allergy.

In vivo sensitization to purified Hevea brasiliensis proteins in health care workers sensitized to natural rubber latex

BACKGROUND

Thirteen proteins of natural rubber latex (Hevea brasiliensis) known to bind human IgE have been isolated and characterized as Hev b allergens. However, the in vivo importance of native Hev b allergens has not been defined in health care workers (HCWs) with natural rubber latex (NRL) allergy.

OBJECTIVES

The principal aim of this study was to identify the major in vivo Hev b allergens in HCWs with NRL allergy confirmed by percutaneous sensitivity to nonammoniated latex (NAL).

METHODS

Skin prick testing was performed with 7 (native) proteins purified from NAL (Hev b 1, 2, 3, 4, 6.01, 7.01, and a newly described Hev b 13) and recombinant Hev b 5 in 62 HCWs with histories of NRL allergy (group 1) confirmed by percutaneous reactivity to NAL and in 49 atopic HCWs without NRL allergy (group 2). Serial 10-fold concentrations of Hev b proteins (5 x 10(-5) microg/mL to 50 microg/mL) were tested; serum samples of subjects were assayed for serum specific IgE by immunoassays.

RESULTS

Hev b 2, Hev b 5, Hev b 6.01, and Hev b 13 produced skin reactions in more than 60% of group 1 subjects, with Hev b 1, 3, 4, and 7.01 eliciting reactions in less than 50%. Only 1 of 49 group 2 workers reacted to a single Hev b antigen (Hev b 13). Specificity of 7 Hev b allergens was 100% and 98% for Hev b 13 in identifying workers with confirmed NRL allergy. Specific IgE by AlaSTAT and CAP immunoassays was elevated in 40 of 60 (67%) and 33 of 62 (53%) of NAL-reactive workers and produced false-positive test results in 4 of 49 (8%) and 3 of 48 (6%) group 2 subjects, respectively.

CONCLUSION

Hev b 2, 5, and 6.01 are major in vivo allergens and Hev b 13 is a new major in vivo allergen among HCWs with allergy to NRL.

Latex allergies in the health care worker

A dramatic increase in the incidence of latex allergies in health care workers followed the surge in latex glove use accompanying the rise of human immunodeficiency virus (HIV) in the early 1980s. This increase in latex glove use was driven by the release of Universal Precautions issued by the Centers for Disease Control (CDC) in response to the rise of HIV and other blood-borne pathogens. Efforts to stem allergic responses in the workplace have relied on the substitution of other materials for latex. Unfortunately, there is so much latex in everyday life that avoiding this allergen is exceedingly difficult once one is sensitized. Additionally, there are numerous cross reactants that are present in the environment. The situation is further confounded by the introduction of genetically manipulated foods and agricultural products that contain defense proteins genetically inserted to protect plants from pests and pathogens. Many of these defense proteins are antigens that will cross react with latex. Sensitivity reactions, once developed, may progress to the point at which the health care worker is excluded from working. This report provides an overview of rubber products and cross reactants, allergic reactions, and latex sensitivity for the health care worker.

Assessment of profilin as an allergen for latex-sensitized patients

BACKGROUND

The presence of the actin-binding protein, profilin, has been demonstrated in natural latex extracts; but the clinical significance of this molecule as an allergen for latex-allergic patients is not clear. We studied the allergenic relevance of isolated latex natural and recombinant profilin, by in vivo and in vitro techniques, in two populations of spina bifida children (SB) and adults allergic to latex (AL).

METHODS

Profilin is present in small amounts in latex extracts obtained from low ammoniated (LA) natural latex. Its purification by affinity chromatography resulted difficult due to Heb v 1 unspecific binding. Therefore a method was developed to obtain natural profilin from natural latex, combining affinity chromatography (PLP, poly-L-proline Sepharose column) and previous ammonium sulfate fractionation. Alternatively, latex c-serum containing a low amount of Hev b 1 and a relatively higher profilin content could be used. Recombinant latex profilin isoform (rHev b 8) was cloned by PCR amplification. The entire coding region of Hev b 8 was subcloned into the expression vector pKN172 and a non-fusion form of Hev b 8 was expressed in Escherichia coli BL21 (DE3). Purified recombinant protein was obtained after a single passage through PLP-Sepharose column.

RESULTS

Natural and recombinant purified Hev b 8 were tested cutaneously by intradermoreaction (ID) in 17 SB and 14 AL patients. They were positive in 15 SB and 14 AL patients. No wheals were produced when tested in nonatopic control patients. Only 42% of sera from latex-allergic patients revealed specific IgE titers of class 1 or higher by enzyme immunoassay and only 39% of them exhibited IgE binding by SDS-PAGE immunoblotting with any natural or recombinant Hev b 8 forms.

CONCLUSION

It seems that profilin is a relevant allergen for both groups of patients from a frequency point of view, but with scarce presence in natural latex extracts and raw sources, with a subsequent low IgE induction capacity.

Protein and allergen assays for natural rubber latex products

The major issues in the efforts to alleviate allergy to natural rubber latex (NRL) proteins are prevention of allergic reactions and decreasing future sensitization. An accurate estimate of the potential allergenicity of NRL products is essential as guidance to manufacturers and users. Development of a reliable in vitro method for the quantitation of NRL allergens has been impeded by (1) limited knowledge of the individual allergens among NRL proteins, (2) variations in the protein profiles among NRL products, and (3) heterogeneity of responses to NRL allergens among sensitized individuals. The current methods include measurement of either the total or the antigenic NRL proteins. Although these methods provide valuable information, all except one have not been validated or standardized. The lack of sensitivity and specificity of this standardized method and poor correlation with the allergenic protein levels have mandated the need for a better assay. In the past year, an immunologic method for the quantitation of all antigenic proteins has been developed as a national standard. The method provides a significant improvement in sensitivity and specificity of NRL protein measurement, but the question of relevance to allergen content remains open. In the last several years, the intensive research aimed at purifying and characterizing individual allergens among NRL proteins resulted in the identification of more than 10 major allergens. On the basis of this knowledge, present efforts are focused on the development of a method for quantitation of relevant allergenic NRL proteins.

Allergens and natural rubber proteins

BACKGROUND

Allergy to natural rubber latex (NRL) results from exposure to proteins derived from Hevea brasiliensis. Type I latex hypersensitivity is observed in certain occupational and other high-risk groups with frequent exposure to NRL products. This includes health care workers (HCWs), workers in the latex industry, children with spina bifida, and atopic individuals.

OBJECTIVES

Early reliable diagnosis and avoidance are required for better patient care. Standardized reagents are not presently available for in vitro and in vivo testing and treatment of patients with latex allergy. However, a number of allergens have been isolated and characterized from Hevea latex and NRL products. Currently, a total of 11 major and minor allergens are designated by the International Allergen Nomenclature Committee. This article reviews the structural and functional characteristics of these latex allergenic proteins.

RESULTS

NRL-allergenic proteins include those involved in the biosynthesis of polyisoprene and coagulation of latex rubber elongation factor, small rubber particle protein, prohevein, and patatin. Pathogenesis-related proteins include beta-1,3-glucanases, chitinases, and hevamine; and the structural proteins include microhelix protein complex, proline-rich protein, profilins, enolases, and manganese superoxide dismutase. Recombinant allergens demonstrated skin test reactivity in patients with latex allergy. The minimal level of skin test reactivity was about 70 pg/mL for NRL and 1 ng/mL for recombinant allergens. The use of selected recombinant latex allergens (Hev b 5, Hev b 6, and Hev b 7) in skin prick tests identified 93% of allergic individuals, mainly health care workers.

CONCLUSIONS

Recombinant latex allergens are clinically reactive and can be produced in a standardized manner, which could potentially provide safe and sensitive reagents for the diagnosis and treatment of type I latex allergy.

Allergic and latex-specific sensitization: route, frequency, and amount of exposure that are required to initiate IgE production

Quantitative data that documents human exposure-response relationships for IgE sensitization to allergens are limited. Although seemingly straightforward, documentation of exposure-response relationships can be difficult. Issues that are related to study design, allergen standardization, exposure assessment, and evaluation for sensitization can impact greatly on study results. Despite these issues, exposure-response relationships for sensitization to protein allergens have been documented in several occupational groups, which include enzyme-detergent workers, bakers, and laboratory animal workers. In general, atopy acts as an effect modifier in these settings, steepening the exposure-response relationship. Several studies suggest that the greatest risk for sensitization is within the first several years of exposure. For 1 allergen, the protease subtilisin, a short-term exposure limit of 60 ng/m(3) has been recommended by the American Council of Governmental Industrial Hygienists. With regard to natural rubber latex, exposure-related factors such as number of operations have been shown to be risk factors for sensitization of children with spina bifida. By contrast, fewer studies show exposure-response relationships for IgE sensitization of health care workers to natural rubber latex, and the area remains controversial. However, a recent cohort study that evaluated incident sensitization in dental hygiene students suggests strongly that, with sufficient exposure, employment in health care can lead to an increased risk of IgE sensitization to natural rubber latex.

Diagnosis of natural rubber latex allergy

The accurate diagnosis of a latex-allergic individual begins with a comprehensive clinical history. Atopy, food allergies, hand dermatitis, and temporal relationships between allergic symptoms and natural rubber product exposure are risk factors that increase the suspicion of latex allergy. If symptoms are temporally delayed (hours-days) and confined to skin-latex product contact areas, Type IV hypersensitivity should be suspected and patch testing may be performed to identify activated T cells that are specific for selected rubber chemical additives. If ocular, upper and lower airway, and/or systemic allergic symptoms are observed with rapid onset (minutes) following a definable latex exposure, Type I hypersensitivity should be suspected. One or several confirmatory tests for latex-specific IgE antibody in the skin or blood may next be performed to verify a sensitized (IgE antibody positive) state. If the clinical history remains discordant with a skin test or blood test result, in vivo provocation tests may be cautiously considered for adjudication. Diagnostic methods for latex-specific IgE antibody detection in skin and blood are overviewed, with a focus on their performance, advantages, and limitations.

Allergenic proteins of natural rubber latex

As the living cytoplasm of laticiferous cells, Hevea brasiliensis latex is a rich blend of organic substances that include a mélange of proteins. A small number of these proteins have given rise to the problem of latex allergy. The salient characteristics of H. brasiliensis latex allergens that are recognized by the International Union of Immunological Societies (IUIS) are reviewed. These are the proteins associated with the rubber particles, the cytosolic C-serum proteins and the B-serum proteins that originate mainly from the lutoids. Procedures for the isolation and purification of latex allergens are discussed, from latex collection in the field to various preparative approaches adopted in the laboratory. As interest in recombinant latex allergens increases, there is a need to validate recombinant proteins to ascertain equivalence with their native counterparts when used in immunological studies, diagnostics, and immunotherapy.

Inhaled latex allergen (Hev b 1)

BACKGROUND

IgE-mediated responses to natural rubber latex allergens have become a major health problem among recognized risk groups.

OBJECTIVE

The purpose of this investigation was to measure the amounts of Hevea brasiliensis latex allergen (Hev b 1) inhaled and deposited on surfaces when latex or vinyl gloves were worn and compare the results with the conventional measures (breathing zone samplers) of occupational exposure.

METHODS

Hev b 1 exposure was measured by nasal sampling and breathing zone sampling. Latex allergen exposure was generated by having each subject don a pair of powdered latex examination gloves and continuing his or her normal daily activity for 30 minutes. By means of adhesive tape, surface dust samples were collected from the surfaces of gloves, the subject's hands, and work areas. Sampling was performed with subjects wearing no gloves, subjects wearing powdered vinyl gloves, subjects wearing powdered latex gloves, and nearby colleagues wearing latex gloves. All samples were assayed through use of the HALOgen assay (Inhalix, Sydney, Australia) with a Hev b 1-specific mAb. Particles transporting latex allergen were identified by a surrounding immunostain halo, and these were quantified and reported as total numbers of particles inhaled, airborne, or found on surface areas evaluated.

RESULTS

Study subjects inhaled 26 times more allergen when powdered latex gloves were worn than under the "no glove" and powdered vinyl glove conditions. During the same period, Hev b 1 particle levels measured in the ambient air through use of the breathing zone sampler increased by 24-fold. The median numbers of particles carrying Hev b 1 allergen per square centimeter on the surface of the hands after the wearing of latex and vinyl gloves were 1964 and 5, respectively. Latex allergen was physically associated both with cornstarch granules and with larger dust particles having a darker, more irregular appearance.

CONCLUSION

In a laboratory where gloves are worn for protection, the use of latex gloves resulted in a 26-fold increase in inhaled latex allergen over background levels measured while vinyl gloves were worn as controls. Low levels of latex exposure also occurred when vinyl gloves or no gloves were worn; the reasons for this are under investigation.

IGE-mediated natural rubber latex allergy: an update

In the past 2 decades, IgE-mediated NRL allergy has become a well-defined condition with recognised risk groups, established diagnostic tools, and adequate prevention strategies (1-3). Furthermore, molecular biology and biochemical techniques have significantly improved our knowledge of the proteins responsible to cause the disease. Clinical manifestations will not be addressed in this review, nor will broad preventive strategies be proposed; these have been discussed elsewhere (4, 5). After a brief introduction this review will focus on specific issues: (1) How do we estimate the prevalence of NRL allergy and who is at risk for clinical sensitisation? (2) What specific allergens cause NRL allergy? How does sensitisation for these allergens occur? Are all patients sensitised for the same allergens? Threshold allergen exposure levels. (4) What is the latex-fruit syndrome? What is the clinical relevance of a positive plant food specific IgE quantification in patients with NRL allergy? (5) How do we diagnose NRL allergy? What are the strengths and weaknesses of currently available diagnostic tools? (7) How do we manage NRL allergy? What is the role of medication and immunotherapy in the treatment of NRL allergy? How do we select an appropriate non-NRL alternative for NRL gloves? Which regulatory provisions have been implemented?

Latex allergy: past and present

Although latex products have been in use for over a century, allergic responses to latex proteins have only been recognized as a serious health problem for the past 15 years. Latex allergy particularly affects two groups, health care workers (HCW) and children with spina bifida (SB). This manuscript provides a brief history of latex allergy, and a review of the following: the manufacturing process for dipped latex products, the 11 latex allergens that have been characterized and received allergen designations by the International Union of Immunological Societies, the methods used in exposure assessment, the epidemiology and clinical management of latex allergy, and the use of animal models in investigating mechanisms underlying latex allergy.

Natural rubber pharmaceutical vial closures release latex allergens that produce skin reactions

BACKGROUND

The release of allergenic proteins from natural rubber vial closures (stoppers) into aqueous pharmaceuticals may induce allergic reactions in individuals with latex allergy (LA) receiving medications from such vials.

OBJECTIVE

The goal of this study was to determine whether solutions stored in vials containing natural rubber closures release allergenic proteins detectable by skin testing of subjects with LA.

METHODS

Five pharmaceutical vial closures (2 natural rubber and 3 synthetic) were coded, inserted onto vials containing phenol-saline-human serum albumin, and stored in an inverted position before use. Twelve volunteers with and 11 volunteers without LA underwent skin testing with solutions from each of the 5 vials, either those not punctured (0P) or those punctured 40 times with a 21-gauge needle 12 to 24 hours before testing (40P).

RESULTS

All intradermal skin test responses in the group without LA were negative. Two and 5 of the 12 subjects with LA had positive intradermal skin reactions to 0P and 40P solutions, respectively, from vials containing rubber closures. Two subjects with LA had inexplicable, positive, nonreproducible intradermal skin test reactions to solutions from vials containing bromobutyl but not vials with isoprene synthetic closures. In vitro inhibition analysis detected 6 to 7 AU/g latex allergen in extracts of cut natural rubber containing closures but not in extracts of synthetic closures.

CONCLUSION

Natural rubber vial closures released allergenic latex proteins into the tested solutions in direct contact during storage in sufficient quantities to elicit positive intradermal skin reactions in some individuals with LA. These data support a recommendation to eliminate natural rubber from closures of pharmaceutical vials.

Latex allergy: review of recent advances

Latex allergy is an IgE-dependent immediate hypersensitivity reaction to latex proteins. Risk factors for latex allergy are contact with latex products and atopy. Children who undergo multiple surgical procedures and healthcare workers are the major groups at risk. Powdered latex gloves are an important source of sensitization. Preventive measures are leading to reduction in latex sensitization and allergic reactions. The prevalence of latex allergy in the general population may be as low as 0.1%, whereas the frequency of latex sensitization is reported to be 7%; this may be due to cross-reacting antipollen IgE. The most important latex allergens have been purified, and some have been cloned and sequenced. Many latex-allergic patients are also allergic to common plant-derived aeroallergens and foods. The structural and biologic relationships among plant-derived food allergens, including latex, explain these clinically important cross-reactions.