Latex-allergic patients sensitized to the major allergen hevein and hevein-like domains of class I chitinases show no increased frequency of latex-associated plant food allergy

Abstract

Allergies to certain fruits such as banana, avocado, chestnut and kiwi are described in 30-70% of latex-allergic patients. This association is attributed to the cross-reactivity between the major latex allergen hevein and hevein-like domains (HLDs) from fruit class I chitinases. We aimed to assess the extent of cross-reactivity between hevein and HLDs using sera from latex-allergic patients with and without plant food allergy. Hevein and HLDs of latex, banana, and avocado chitinases were expressed in Escherichia coli as fusion proteins with the maltose-binding protein and purified by affinity chromatography. IgE binding to these proteins was studied in sera from 59 latex-allergic patients and 20 banana-allergic patients without latex allergy by ELISA and ELISA inhibition. Additionally, 16,408 allergic patients' sera were tested for IgE binding to hevein, latex chitinase, and wheat germ agglutinin using an allergen microarray. Hevein-specific IgE was detected in 34/59 (58%) latex-allergic patients' sera. HLDs of latex, banana, and avocado chitinases were recognized by 21 (36%), 20 (34%), and 9 (15%) sera, respectively. In contrast, only one of 20 banana-allergic patients without latex allergy was sensitized to chitinase HLDs. In most tested latex-allergic patients' sera, IgE binding to hevein was only partially reduced by preincubation with HLDs. Among hevein-sensitized, latex-allergic patients, the percentage of plant food allergy (15/34 = 44%) was equal to latex-allergic patients without hevein sensitization (11/25 = 44%). In the general allergic population, 230 of 16,408 sera (1.4%) reacted to hevein and/or a hevein-like allergen. Of these, 128 sera showed an isolated sensitization to hevein, whereas only 17 bound to latex chitinase or wheat germ agglutinin without hevein sensitization. In conclusion, the IgE response to HLDs is elicited by hevein as sensitizing allergen in most cases. Despite considerable cross-reactivity between these allergens, no correlation between latex-associated plant food allergy and sensitization to hevein or HLDs was found.

Fig. 1

Sequence and structure comparison of hevein and HLDs. (A) Multiple sequence alignment; grey: residues identical to corresponding ones in hevein, bold: conserved cysteine residues, dashes: gaps introduced during the alignment. (B) Mapping of conserved residues onto the molecular surface of hevein (PDB ID: 1hev). Black: residues conserved between hevein and HLDs of class I chitinases (left) or Tri a 18 (right), respectively. Molecular graphics images were produced using the UCSF Chimera package from the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco (supported by NIH P41 RR-01081) (Pettersen et al., 2004).

Fig. 2

IgE binding patterns towards hevein and HLDs. (A) Sera of 59 latex-allergic patients tested in an IgE ELISA. Patients are grouped according to the existence of food allergy to avocado (Avo) and banana (Ban). (B) Sera of 230 allergic patients sensitized to at least one of the tested allergens on the ISAC.

Fig. 3

Distribution of the amounts of IgE specific for hevein and hevein-like domains. (A) IgE specific for hevein and class I chitinase HLDs among 59 latex-allergic patients. The plot shows the ELISA OD values resulting from the conversion of p-nitrophenyl phosphate catalyzed by the alkaline phosphatase conjugated to the secondary antibody. (B) IgE specific for hevein, Hev b 11-HLD and Tri a 18 among 230 patients from a general allergic population sensitized to any of the tested allergens. Allergen-specific IgE was measured by ISAC. Medians with interquartile ranges are indicated.

Fig. 4

Correlation of paired IgE values specific for hevein and HLDs. Specific IgE was measured by ISAC in 230 sera from a general allergic population sensitized to any hevein-like allergen.

Fig. 5

IgE inhibition ELISA. Sera of selected latex-allergic patients were tested for IgE binding to hevein and HLDs in a direct ELISA (left column) and in an inhibition assay (right column). Sera were preincubated with Hev b 6.02 (black bars), Hev b 11-HLD (dark grey), Mus a 2-HLD (light grey), and Pers a 1-HLD (white) before proceeding with the immunoassay.

Fig. 6

Comparison of hevein sensitization and plant food allergy among 59 latex-allergic patients. Hevein sensitization was determined by IgE ELISA, plant food allergy was assessed based on the symptoms reported by the patients.