Latex allergy diagnosis: in vivo and in vitro standardization of a natural rubber latex extract

For the diagnosis of IgE-mediated (immediate) hypersensitivity to natural rubber latex (NRL), skin prick testing with extracts of latex gloves has been widely used, but such extracts are difficult to standardize. The present study aimed to produce on an industrial scale an NRL extract from freshly collected NRL and to evaluate, calibrate, and standardize the extract by both in vivo and in vitro testing. The source material, latex of the rubber tree, Hevea brasiliensis (clone RRIM 600), was frozen immediately after collection in Malaysia and shipped in dry ice to Stallergènes SA, France. Protein and allergen profiles were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, isoelectric focusing (IEF), crossed immunoelectrophoresis (CIE), and crossed radioimmunoelectrophoresis (CRIE). Allergen quantification was effected by RAST inhibition. The capacity of the preparation to elicit immediate hypersensitivity reactions in vivo was measured by skin prick testing in 46 latex-allergic patients and 76 nonallergic control subjects. SDS-PAGE and immunoblot profiles of the extract and an NRL standard (E8) provided by the US Food and Drug Administration were almost identical, disclosing several distinct IgE-binding proteins with apparent molecular weights of 14, 20, 27, 30, and 45 kDa, conforming to reported molecular weights of several significant NRL allergens. An arbitrary index of reactivity (IR) of 100 was assigned to the extract at 1:200 dilution (w/v), having a protein content of 22 micrograms/ml. Skin prick testing of latex-allergic patients and controls using the extract at 100 IR revealed 93% sensitivity, 100% specificity, 100% negative predictive value, and 96% positive predictive value. In conclusion, a skin prick test reagent for diagnosis of type I NRL allergy was successfully standardized. The reagent was demonstrated to contain most, if not all, of the currently known clinically significant NRL allergens, and it showed high sensitivity and specificity.

Significance of rubber elongation factor as a latex allergen

IgE-mediated hypersensitivity to proteins eluting from surgical gloves and other natural rubber products is a well-recognized allergic condition with special impact to health care workers and sensitized patients. Since rubber elongation factor (REF) has been suggested to be the major latex allergen (Hev b 1) we purified REF from rubber particles using electrophoresis and electroelution and reevaluated the occurrence of IgE antibodies to purified REF. The purified protein was subjected to tryptic digestion, peptide separation and amino acid sequencing. Amino acid sequences of 9 tryptic peptides from the purified 14-kD protein gave 100% homology to REF. In immunoblotting, sera from 4 of 6 latex-allergic children with spina bifida or other congenital anomalies exhibited IgE antibodies against REF whereas only 1 serum from the 30 other latex-allergic patients had similar antibodies. In IgE ELISA 8/45 (18%) latex-allergic patients had IgE antibodies to purified REF, whereas 30 (67%) of the same patients had IgE antibodies to purified prohevein, another rubber protein, recently shown to be a major natural rubber latex allergen. The observed overall low frequency of IgE antibodies to purified REF, as measured by two specific IgE assays, indicates that REF is one but not the most significant allergen among the natural rubber latex proteins.

Crossreactivity between allergens in natural rubber latex and banana studied by immunoblot inhibition

BACKGROUND

An association between allergic reactions to natural rubber latex and to banana has been reported but the immunochemical properties of the putative cross-reacting allergens remain unknown.

OBJECTIVE

To study extracts of banana and natural rubber latex and sera from latex-allergic patients for possible crossreacting allergens and IgE antibodies.

METHODS

Sera from 22 latex-allergic patients and 22 control subjects with no evidence of allergy to latex or to banana were studied. All patients had positive and controls negative reactions in skin-prick testing using an eluate of latex gloves. IgE antibodies to natural rubber latex and to banana were evaluated by immunoblotting and by radioallergosorbent test (RAST) and crossreactivity between allergens in banana and natural rubber latex by immunoblot inhibition. Skin-prick testing was used to examine in vivo reactivity to banana.

RESULTS

Ten of the 22 (45%) latex-allergic patients sera recognized altogether 14 allergens in banana by immunoblotting. The most frequently identified banana allergens were 23, 32, 36, 39 and 47 kDa proteins. The banana skin-prick test was positive in 14 of 18 (78%) latex-allergic patients studied and banana RAST in 12 of 14 patient sera tested. Fourteen of 21 interviewed patients reported symptoms from eating or handling bananas. In immunoblot inhibition studies a dose-dependent inhibition of IgE binding to banana extract with natural rubber latex proteins was observed in all five patient sera tested and, likewise, the binding of IgE to natural rubber latex extract was inhibited with banana proteins in four of the five patient sera.

CONCLUSIONS

The present results confirm the existence of crossreacting allergens in natural rubber latex and banana and provide new information on the immunochemical nature and heterogeneity of these allergens.

The main IgE-binding epitope of a major latex allergen, prohevein, is present in its N-terminal 43-amino acid fragment, hevein

Polypeptides of natural rubber latex (NRL) that elute from surgeon's gloves and other manufactured rubber products can sensitize exposed individuals and elicit severe hypersensitivity reactions. Previously, we showed that prohevein is a major allergen in NRL, the source material for rubber manufacturing. To analyze which region of the molecule carries the main IgE-binding epitope(s), we purified prohevein and its C-domain from NRL by gel filtration, reverse phase chromatography, and electroelution. In immunoblotting, prohevein bound IgE from 15 of 20 (75%), and the prohevein C-domain from 3 of 20 (15%) latex-allergic patient sera. In ELISA, 36 of 52 (69%) patient sera showed IgE binding to prohevein, whereas 11 of 52 (21%) sera had IgE to prohevein C-domain. We then purified from a brand of highly allergenic surgeon's gloves six hydrophilic peptides that revealed in amino-terminal sequencing 100% identity to the N-terminus of prohevein. In mass spectrometry, all purified peptides gave a molecular mass of 4719 +/- 1.9 daltons, which corresponds to the molecular mass of hevein (4719.1 daltons), a 43-amino acid N-terminal fragment of prohevein. Purified hevein inhibited 72% of IgE binding from pooled sera of NRL-allergic patients to solid phase glove extract and 45% of IgE binding to solid phase NRL. Of the 43 NRL-allergic patient sera tested, 56% showed IgE Abs to purified hevein in ELISA. In skin prick testing, purified hevein elicited positive reactions in three-quarters of the latex-allergic patients tested. These results indicate that the majority of prohevein's IgE-binding ability resides in its N-terminal fragment, known as hevein. In one highly allergenic latex glove examined, the majority of IgE-binding ability was attributable to hevein molecules, suggesting that these peptides can be significant sensitizers in NRL allergy.

The main IgE-binding epitope of a major latex allergen, prohevein, is present in its N-terminal 43-amino acid fragment, hevein

Polypeptides of natural rubber latex (NRL) that elute from surgeon's gloves and other manufactured rubber products can sensitize exposed individuals and elicit severe hypersensitivity reactions. Previously, we showed that prohevein is a major allergen in NRL, the source material for rubber manufacturing. To analyze which region of the molecule carries the main IgE-binding epitope(s), we purified prohevein and its C-domain from NRL by gel filtration, reverse phase chromatography, and electroelution. In immunoblotting, prohevein bound IgE from 15 of 20 (75%), and the prohevein C-domain from 3 of 20 (15%) latex-allergic patient sera. In ELISA, 36 of 52 (69%) patient sera showed IgE binding to prohevein, whereas 11 of 52 (21%) sera had IgE to prohevein C-domain. We then purified from a brand of highly allergenic surgeon's gloves six hydrophilic peptides that revealed in amino-terminal sequencing 100% identity to the N-terminus of prohevein. In mass spectrometry, all purified peptides gave a molecular mass of 4719 +/- 1.9 daltons, which corresponds to the molecular mass of hevein (4719.1 daltons), a 43-amino acid N-terminal fragment of prohevein. Purified hevein inhibited 72% of IgE binding from pooled sera of NRL-allergic patients to solid phase glove extract and 45% of IgE binding to solid phase NRL. Of the 43 NRL-allergic patient sera tested, 56% showed IgE Abs to purified hevein in ELISA. In skin prick testing, purified hevein elicited positive reactions in three-quarters of the latex-allergic patients tested. These results indicate that the majority of prohevein's IgE-binding ability resides in its N-terminal fragment, known as hevein. In one highly allergenic latex glove examined, the majority of IgE-binding ability was attributable to hevein molecules, suggesting that these peptides can be significant sensitizers in NRL allergy.

A two-dimensional electrophoretic analysis of latex peptides reacting with IgE and IgG antibodies from patients with latex allergy

Latex proteins from nonammoniated natural rubber latex were investigated for their reactivity with antibodies in the sera of patients with spina bifida and health care workers with allergy to latex. Immunoblots of two-dimensional electrophoresis were used to compare the reactivity of various polypeptides against IgE, IgG, and subclasses of IgG. A total of 79 polypeptides showed reactivity with IgG and IgE antibodies from different patients. IgG showed reactivity with all the 79 polypeptides, while IgE reacted with 56 allergens. IgG2 reacted with the least number of proteins, while IgG4 reacted with the largest number of polypeptides. Several antigens were identified as significant due to their reactivity with antibodies in latex-allergic patients. Four proteins reacted with IgE, IgG1, IgG3 and IgG4 of only spina bifida patients with latex allergy, while one other protein reacted only with health care workers. Thus, these relevant latex peptides may be isolated, purified, and used in various assays for more reliable diagnosis of latex allergy.

Cross-reacting allergens in natural rubber latex and avocado

BACKGROUND

An association between allergy to latex and avocado has been reported but the responsible cross-reacting allergens have not been identified or characterized.

METHODS

Immunoblotting, immunoblot inhibition, and RAST inhibition methods were used to study cross-reactive proteins between natural rubber latex (NRL) and avocado. Sera from 18 patients with previously verified latex allergy were used as the source of IgE antibodies, and 11 of the patients underwent skin prick testing with fresh avocado.

RESULTS

Fourteen of the 18 sera (78%) had IgE antibodies that bound to a total of 17 avocado proteins with apparent molecular weights ranging from 16 to 91 kd. Ten most strongly reacting sera were used for immunoblot inhibition studies. When NRL proteins were used as soluble inhibitors, binding of IgE antibodies to solid-phase avocado proteins was inhibited in a dose-dependent manner: 100 micrograms of NRL proteins inhibited IgE binding to 15 of the 17 avocado proteins, and 10 micrograms caused inhibition to 13 protein bands. Comparably, soluble avocado proteins were able to inhibit IgE binding to solid-phase NRL. Corresponding RAST inhibitions were performed with two patient sera; in both, avocado inhibited IgE binding to NRL and in one NRL proteins inhibited IgE binding to avocado. Skin prick test responses to fresh avocado were positive in seven of the 11 patients with latex allergy who were tested.

CONCLUSIONS

The large number of inhibitable proteins in immunoblot experiments and clinical observations from skin prick tests suggest considerable immunologic cross-reactivity between NRL and avocado. The observed cross-reacting protein components may be responsible for the recently reported type I hypersensitivity reactions to NRL and avocado in patients with a preexisting allergy to either allergen.

Prohevein from the rubber tree (Hevea brasiliensis) is a major latex allergen

BACKGROUND

There is general agreement that proteins eluting from different natural rubber latex products can cause immediate type hypersensitivity reactions in latex-allergic patients. However, there is as yet no consensus as to what are the most important allergens in natural rubber latex.

OBJECTIVE

We wanted to purify and characterize at the primary structure level three natural latex proteins, suggested to represent significant allergens.

METHODS

Proteins were purified from ultracentrifuged bottom fraction of natural rubber latex using high performance liquid chromatography gel filtration and reversed phase chromatography. Purified proteins were subjected to tryptic cleavage, peptide separation and amino acid sequencing. Immunoblotting was used to demonstrate IgE antibodies to the purified proteins in sera from latex-allergic patients.

RESULTS

A 20 kDa protein was identified by amino acid sequencing as prohevein, a major protein in the rubber tree Hevea brasiliensis, and a 30 kDa natural rubber latex protein as hevamine, another essential rubber tree protein. A third, previously undescribed natural rubber latex protein, showed high homology to several plant endo-1,3-beta-glucosidases. In immunoblotting, the purified prohevein bound IgE antibodies from 24/29 (83%) sera of latex-allergic patients including positive results in 4/6 latex-allergic children with spina bifida or other congenital anomalies. The purified prohevein elicited positive skin-prick test reactions in all six latex-allergic patients showing IgE to prohevein. The purified 36 kDa protein bound IgE from 6/29 (21%) latex-allergic sera, and the purified hevamine from only 1/29 patient sera.

CONCLUSION

The observed high frequency of IgE antibodies to prohevein suggests that this protein is a major natural rubber latex allergen.

Purification and partial amino acid sequencing of a 27-kD natural rubber allergen recognized by latex-allergic children with spina bifida

We purified from natural rubber latex (NRL) by means of high-performance liquid chromatography a 27-kD protein, recognized characteristically by IgE in sera from latex-allergic children with spina bifida or other congenital anomalies and histories of multiple surgeries. N-terminal sequence analysis of the purified 27-kD protein was unsuccessful suggesting that its N-terminus is blocked. To obtain internal sequence information from the protein it was digested with trypsin and the purified tryptic peptides were subjected to sequence analysis. Thirteen of the 14 sequenced peptides revealed no significant homology to any of the published protein sequences indicating that the 27-kD protein is previously undescribed at the primary structure level. However, one of the 14 sequenced peptides showed significant homology to the rubber elongation factor, a 14.6-kD NRL protein. For the time being, the 27-kD NRL protein is the first molecularly characterized NRL allergen associated with defined clinical manifestations of latex allergy.

Allergen and protein content of latex gloves

BACKGROUND

Proteins eluting from surgical gloves and other medical rubber products elicit immediate local and systemic hypersensitivity reactions in latex-allergic subjects but detailed knowledge about the amount and allergenic potential of these proteins is scanty.

OBJECTIVE

To protect latex-allergic people and to diminish the risk of sensitization, adequate methods are needed to measure and monitor the allergen content of surgical latex gloves.

METHODS

Extracts of six surgical and one household latex glove brand were studied. Bradford and Lowry methods were used for total protein measurements. Sera from 17 latex-allergic patients were used as a source of latex IgE antibodies. Allergen content of extracts was studied in vitro by immunoblot, crossed radioimmunoelectrophoresis and immunospot methods, and in vivo by skin prick testing in 35 latex-allergic patients.

RESULTS

The total protein concentration of the glove extracts varied from 3 to 337 micrograms/g glove. The Bradford method gave lower values than the Lowry method. Immunoblotting showed allergenic rubber proteins in four of the seven glove brands. Ten proteins in two surgical and six proteins in one household glove brand bound latex IgE antibodies in a heterogeneous manner. The results from crossed radioimmunoelectrophoresis and immunospot assays were mostly in line with immunoblotting findings. Extracts from five of the seven glove brands elicited positive prick tests; in all five also the presence of allergens could be shown by in vitro tests. Prick test reactivity and total protein concentration were not directly correlated.

CONCLUSIONS

In vitro assays showed considerable variation in the total protein and allergen contents of different latex glove brands. The amount of protein eluting from the gloves did not always correlate with their allergenicity in skin prick tests indicating that total protein measurement is not a sufficient method to monitor the allergenic properties of latex gloves.

Latex allergy: frequent occurrence of IgE antibodies to a cluster of 11 latex proteins in patients with spina bifida and histories of anaphylaxis

Proteins and allergens in natural rubber latex were characterized by a two-dimensional immunoblot method with serum samples from 17 patients with latex allergy of whom 10 had spina bifida and 7 were health care workers. We demonstrated in rubber tree sap approximately 240 polypeptides of which 57 bound immunoglobulin E (IgE) in patient serum samples. Forty-six of the 57 allergens were identified by patients with spina bifida, 19 of 57 allergens by health care workers, and 8 of 57 allergens by both patient groups. IgE antibodies from all 5 patients with spina bifida with histories of anaphylaxis bound three allergens with molecular weights of 27 kd and isoelectric points ranging from pH 4.6 to pH 4.8. Four of these 5 patients also identified a complex of eight other allergens with molecular weights ranging from 13 kd to 27 kd and isoelectric points from pH 4.4 to pH 5.6. This cluster of 11 allergens was identified by none of the 7 health care workers and by only 1 of 5 patients with spina bifida without demonstrable anaphylaxis. These preliminary findings indicate that patients with spina bifida in whom latex hypersensitivity has developed exhibit a strong anti-latex IgE immune response, which seems to differ markedly from the immune response of health care workers with latex allergy. The characteristic anti-latex IgE profile in patients with spina bifida and with a history of an anaphylactic reaction may be valuable in the evaluation of pathogenetic processes in latex allergy.

IgE immune response to rubber proteins in adult patients with latex allergy

In the present immunoblot study we examined IgE immune responses to natural rubber latex proteins in sera from 27 adult patients with latex allergy. We demonstrated at least 30 proteins in the rubber tree sap, of which 19 bound IgE antibodies in a heterogeneous manner in patient sera. Twenty-two of the 27 patient sera (81%) showed positive immunoblot test results. IgE antibodies in the patient sera bound most frequently to a 20 kd allergen, which was recognized by 17 of the 22 (77%) patient sera with positive immunoblot test results. These results suggest that a 20 kd rubber protein could be a major allergen in adult patients with latex allergy. Immunoblotting with a representative set of allergens as antigen would offer a sensitive, confirmatory in vitro test to demonstrate hypersensitivity to latex.

Immunoglobulin E reactivity to latex antigens in the sera of patients from Finland and the United States

BACKGROUND

Patients with latex sensitivity and latex antigens from the United States and Finland, two countries where allergic reactions to latex have been widely reported, were evaluated to determine the spectrum of immune responses.

METHODS

Sera from 27 patients from Finland and 18 from the United States with latex allergy and control sera from nonsensitive individuals were studied for latex-specific IgE antibodies. Four antigen preparations were used: two extracted from gloves and one each extracted from rubber tree sap from Malaysia and India. All 45 patients had skin prick test results that were positive to latex antigens, and all sera were evaluated by enzyme-linked immunosorbent assay (ELISA) with the various antigens.

RESULTS

There were considerable differences in the reactivity of patient sera with the different antigens. Only 50% of the sera from patients with latex allergy from Finland demonstrated significant levels of IgE to latex as determined by enzyme-linked immunosorbent assay. These patients showed more reactivity with rubber tree sap antigens than with glove antigens. However, 72% of the patients from the United States demonstrated antibodies to latex, and no marked differences were noted between the antigen extracts.

CONCLUSIONS

The results indicate that reagents such as rubber tree sap, which contain multiple clinically significant antigenic components, should be included in evaluation of latex allergy and that differences in patient populations may result in serologic variances.

IgE reactivity to 14-kD and 27-kD natural rubber proteins in latex-allergic children with spina bifida and other congenital anomalies

We examined by immunoblotting sera from 39 latex-allergic patients, 19 from USA and 20 from Finland, including 15 children with spina bifida and 5 children with other congenital anomalies, for IgE antibodies to natural rubber latex (latex) antigens. IgE antibodies in 10 of the 12 (83%) US spina bifida patients and in 2 of the 3 Finnish spina bifida patients recognized a previously undescribed 27-kD antigen which, together with a 14- and a 20-kD peptide, appeared to be a major latex allergen. Two patients with other congenital anomalies, one from the US and one from Finland, also demonstrated anti-27-kD bands. IgE antibodies to the 27-kD antigen were not detected in other latex-allergic patients from the US or Finland although most of them showed IgE binding to 14- and/or 20-kD latex antigens. All 21 controls, including 3 spina bifida patients with no evidence of latex allergy, gave negative immunoblot results. This observation suggests that patients with spina bifida or other congenital anomalies who have been subject to multiple operations and other invasive therapeutic procedures may have been exposed to different antigenic source materials than other latex-allergic patients.

Detection of IgG4 and IgE antibodies to rubber proteins by immunoblotting in latex allergy

Sera from four latex-allergic hospital employees (two physicians and two nurses) were examined for the occurrence of IgG4 and IgE antibodies to rubber proteins by immunoblotting. We used natural rubber sap as antigen source and detected IgG4 antibodies in all four patient sera. The IgG4 antibodies bound to 12 rubber protein antigens with molecular weights ranging from 14 kD to 53 kD. IgE antibodies bound nine of the antigens and the major antigen for both IgG4 and IgE seemed to be a 21 kD rubber protein. The parallel occurrence of IgG4 and IgE antibodies against the same rubber protein antigens suggests that IgG4 antibodies also may play a role in the pathogenesis of latex allergy.

Surgical latex glove allergy: characterization of rubber protein allergens by immunoblotting

Immunoblot analysis employing IgE antibodies derived from sera of 3 physicians and 2 nurses allergic to surgical latex gloves, disclosed 10 allergens in natural rubber sap. Nine of the 10 allergens were detected in ammoniated natural rubber latex, but only 4 allergens in a latex glove extract. The allergenic proteins had apparent molecular weights ranging from 14 to 70 kD. Allergens with molecular weights of 14 and 21 kD showed the most intense immunoblot reactions suggesting that these proteins could be the major allergens in the natural rubber. An 11-kD protein and a 26-kD protein were only seen in the glove extract, indicating that they could be modified rubber proteins formed during glove manufacture.