710 A dipstick test or in vitro diagnosis of natural rubber latex (NRL) allergy as a useful screening test

S240

Abstracts

J ALLERGY CLIN IMMUNOL JANUARY 2000

TESTS sodium periodate treatment to destroy the carbohydrate epitopes, GI and GII lost most of their IgE-binding activity. Inhibition ELISA supported the significance of the carbohydrate epitopes. The Hev b 2 isoenzymes competitively inhibited the IgE binding to the homologous antigens adsorbed on a plate. Enzymatic degradation of their peptide backbones did not cause substantial diminution of the inhibition Our experimental results suggest the relevance of carbohydrate epitopes in Hev b 2 to the diagnosis of the latex allergy and latexfruit syndrome. It is generally considered that IgE binding to car-

DIAGNOSTIC

MAGIC

A Dipstick Test for In Vitro Diagnosis of Natural Rubber Latex (NRL) Allergy as a Useful Screening Test B Kiirrirrg*. R Wuhlt. B Rundolf*

*Department

of Dermatology.

Esmarch SW 56.48149 Mtinster, beck, Germany Since assays for quantitative

University

Germany

of Mttnster.

tAllergopharma.

measurement

of serum

Von Rhein-

specific

IgE

antibodies are generally accepted for the diagnosis of latex allergy we examined the value of a semiquantitative dipstick assay (Allergodip-Latex. Allergopharma) as a screening test for NRL allergy. The test includes ammoniated and non-ammoniated latex allergen pads together with positive with established quantitative System, DPC-AlaSTAT,and

and negative controls. Data obtained assays including Pharmacia Cap-FEIA Magic Light (Chiron diagnostics were

compared with the dipstick test in latex-sensitized (n=lS sensitized (n=232) persons, mainly health care workers. the in vitro findings were related to clinical symptoms

I) and nonIn addition after expo-

SENSITIVITY

STANDARD

I%)

SPECIFICITY

89.0 96.8 93.7 91.9 83.8

LIGHT

ALLERGODIP SKIN PRICK TEST In the detined

subgroup,

(%)

99.0 90.3 90.8 92.2 93.3

the Allergodip-Latex

dipstick

test iden-

tities correctly 91 of 99 (91.9%) latex sensitized persons and 107 out of I16 (92.9%) non-sensitized persons. These data are in line with the other in vitro assays. In contrast to other in vitro assays the dipstick test requires no further laboratory equipment. This test is very easy to perform and the hand-on time is only S-IO min. The results of a semiquantitative test depend on subjective assessment.

should be carefully evaluated. Carbohydrate epitopes may also confuse the serum tests when investigating the cross-reactivity of latexallergic patients. Many plant-derived proteins and some invertebrate

710

TEST

TO THE DIAGNOSTIC

CAP-FEIA ALASTAT

bohydrate epitopes does not necessary provoke allergic symptoms. They often cause false-positive results in irt vitro IgE tests. Therefore, the actual allergenicity of Hev b 2 for a latex-allergic patient

proteins contain a cross-reactive carbohydrate determinant (CCD). We must take into account the effect of CCD when the cross-reaction of a latex-allergic patient was examined by in vim IgE tests.

RELATIVE

In this case interpersonal variability is low and the test fultils requirements for semiquantitative screening of NRL allergy.

711

Unique Patients Bonani

the

and Shared IgE Epitopes of Hev b 1 and Hev b 3 for With Latex Hypersensitivity Kurcharitr Knrrirpong. Bonerjee.

V K~rrup.

Laura

Casrillo.

J Fink.

K Kelly

Medical

College of Wisconsin and VAMC, Milwaukee, WI, USA Two major water insoluble proteins located on the surface of rubber particles in Hewn brnsiliensis latex are the 14.6 kDa rubber elongation factor Hev b I and its homolog, 23 kDa Hev b 3. These 2 proteins with 47% amino acid sequence homology exhibited binding to IgE antibody in sera from patients with latex hypersensitivity especially in children with spina bitida (SB). The humoral and cell mediated immune responses of these allergens in latex allergic patients are well recognized. However, little is known about the structure involvement understanding

and function relationship of these allergens and their in the immune modulation of latex allergy. A clear of the IgE binding epitopes of Hev b I and Hev b 3

may contribute not only to the precise diagnosis of latex allergy, but also to the management of the disease. This study aimed at defining the IgE antibody binding regions in the allergens Hev b 1 and Hev

sure to NRL and skin prick test results with a panel of different latex allergen extracts. All subjects with a positive skin prick test (SPT) suffered from contact urticaria, allergic rhinitis or conjunctivitis

b 3. Linear overlapping thesized on derivatized the synthetic peptides

after exposure to NRL. On the basis of this coincidence we compared the results of the in vitro assays with skin prick test results.

with latex allergy revealed 8 IgE binding regions in Hev b I and I I in Hev b 3. Seven out of I I epitopes of Hev b 3 were at the N-terminal region with maximum sequence homology to Hev b I. The

VALIDATION IN VITRO

ASSAY

CAP-FEIA ALASTAT

MAGICLIGHT ALLERGODIP In order

OF IN VITRO NUMBER

ASSAYS

SENSITIVITY

380 302 273 375 to analyse

IN COMPARISON (%)

90.0 73.7 74.5 73.9 sensitivity

and specificity

TO SPT

SPECIFICITY

(%I

85.3 87.7 89.8 85.5 for all in vitro

decapeptides of the 2 allergens were syncellulose membranes. The IgE binding of studied with pooled sera from SB patients

identified IgE binding sequences from both Hev b I and Hev b 3 were synthesized and SB and HCW sera were evaluated for IgE antibody binding. These epitopes were also studied for their reactivity to monoclonal antibody against Hev b 3 and polyclonal mouse sera against Hev b I, The result indicates that N-region peptide of Hev b I KYLGFVQDAA (I 6-25) reacted only with IgE of latex allergic study reacted AEEVEEERLK

SB sera. None of the other sera used in the present to this epitope. Similarly 4 sequences from Hev b 3. (2-I 1). YYIPLEAVKF (60-69). APRIVLDVAS

assays we defined a subgroup including all subjects who had been tested with all four in vitro assays and skin prick test (n=215). We defined a diagnostic standard in terms of at least three correspond-

(104-I 13). and GVQEGAKALY (I 19-128) showed specific IgE antibody binding only to SB sera. The IgE of HCW patients with latex allergy reacted specifically with 3 epitopes of Hev b I and 2

ing test results out of all diagnostic methods (in vitro assays and skin prick test). The sensitivity and specificity of each diagnostic were determinated relative to this diagnostic standard.

C-terminal epitopes of Hev b 3. In conclusion, the results indicate that the presence of both unique and shared IgE epitopes in the structurally similar Hev b I and Hev b 3 allergens may be of value in the reliable diagnosis of latex hypersensitivity and in understanding the pathophysiology of latex induced allergy.