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Les chitinases
mardi 6 avril 2010, par
Les chitinases sont des enzymes glycolytiques détruisant la chitine.
La chitine est un composant de la paroi de nombreux organismes : insectes, fungi, arthropodes, nématodes, etc... Après la cellulose, la chitine est le polysaccharide le plus abondant dans la nature.
La chitine a un rôle protecteur. Mais les organismes colonisés ou attaqués se défendent en secrétant des enzymes capables de détruire la chitine, dont des chitinases. C’est le cas, notamment des plantes 
.
Les chitinases ont aussi un rôle physiologique. On en trouve, par exemple, dans le tractus digestif des acariens .
On sait à présent que des protéines chitinase-like sont également sécrétées dans l’asthme et qu’elles participent à la réponse inflammatoire .
Les chitinases sont rangées en différentes « classes » sur la base de similitudes au sein de leur séquence peptidique : on connaît ainsi 5 classes de chitinases .
Les chitinases de classe 1 sont connues en allergologie comme étant à l’origine du "syndrome latex-fruits" (cf. syndrome latex-aliments).
En fait l’allergie croisée entre le latex et certains produits d’origine végétale a essentiellement pour base une homologie avec un composant du latex qui n’est pas une chitinase mais une "win" protéine, la pro-hévéine Hev b 6.01 (WIN = wound-induced). La pro-hévéine est une protéine de défense végétale ("PR-protéine" = pathogenesis-related protein).
On comprend que des PR-protéines soient présentes dans le latex dont la sécrétion a justement pour but de combattre un danger pour la plante (cicatrisation d’une blessure, pouvoir anti-microbien, …) .
La pro-hévéine est composée de 2 portions juxtaposées : un domaine N-Terminal (l’hévéine Hev b 6.02) et un domaine C-terminal (Hev b 6.03). Dans le latex collecté sur les Hevea de l’hévéine libre est présente aussi.
La nature a parfois utilisé des "blocs" de construction pour composer ses protéines. Ainsi, le domaine hévéine se retrouve-t-il dans d’autres protéines, à commencer par certaines chitinases.
Toutes les chitinases n’ont pas de domaine hévéine (cf.schéma ci-dessous ).
Quand le domaine hévéine est présent, sa fonction est de se lier au polysaccharide à attaquer : l’hévéine est une des multiples sortes de lectines.
Le domaine C-terminal des chitinases porte, de son côté, l’activité enzymatique.
Même s’il est théoriquement possible qu’une sensibilisation au latex apparaisse secondairement à une allergie mettant en jeu des chitinases alimentaires (cf. Latex et aliments), le plus souvent le latex est l’initiateur de l’allergie croisée et, plus précisément, le domaine hévéine dans le latex .
On a donc une réactivité croisée hévéine du latex ↔ chitinases alimentaires.
Quelles chitinases sont susceptibles de croiser avec l’hévéine ?
Celles qui possèdent un domaine hévéine, c’est à dire celles de classe 1 ou 4 (cf. schéma ci-dessus).
Il se trouve que pour l’instant, seules des chitinases de classe 1 ont montré une réactivité croisée avec l’hévéine (ou le latex).
On a identifié peu de chitinases classe 4 IgE-réactives comparativement aux classe 1 : une dans le raisin et une dans le pollen de cèdre du Japon (Cryptomeria japonica).
Mais la raison principale de cette absence de réactivité croisée pourrait tenir plutôt dans un déficit d’homologie entre les domaines hévéines des chitinases de classe 4 avec l’hévéine du latex. Pour celle du raisin, le pourcentage d’identité n’est que de 53 % (cf. tableau ci-dessous).
Pourcentages d’identité des domaines hévéine de quelques chitinases en comparaison avec l’hévéine du latex (Hev b 6.02)
| chitinases de classe 1 | latex (Hev b 11) | 68 |
| avocat (Pers a 1) | 73 | |
| banane | 68 | |
| châtaigne (Cas s 5) | 70 | |
| haricot | 70 | |
| chitinase de classe 4 | raisin | 53 |
Les chitinases ayant un rôle important de défense pour les végétaux, on peut estimer que tous les végétaux, au moins dans certains organes importants comme les fruits ou les graines, contiennent des chitinases et pourraient être l’objet d’une allergie croisée avec le latex.
En dehors de limitations liées au degré d’identité avec l’hévéine (cf. tableau ci-dessus), un autre facteur important pour empêcher une réactivité croisée réside dans la relative fragilité des chitinases à la chaleur (cuisson des aliments) et à la digestion.
La chaleur provoque une déformation des protéines qui ne retrouvent pas toujours leur conformation initiale avec le refroidissement.
Dans le cas des chitinases, le domaine hévéine, riche en ponts disulfure, pourrait mieux résister mais la présentation des épitopes de l’hévéine être gênée par la dénaturation du domaine C-terminal.
Pour la digestibilité, il a été montré que les chitinases étaient très rapidement dégradées en milieu gastrique.
Associée à l’effet de la cuisson, cette digestibilité explique que les réactions cliniques soient souvent localisées à la sphère orale et plutôt restreintes à des aliments consommés crus : avocat, banane, kiwi, par opposition aux haricots, pois, riz et autres pommes de terre.
A noter, de plus, que ces aliments sont habituellement cuits dans l’eau ce qui entraîne une élution potentielle d’une partie des allergènes solubles. Par exemple, la châtaigne et le sarrasin, bien que consommés cuits, n’ont pas ce phénomène éventuel d’élution.
Cependant, la digestibilité n’est pas toujours complète et des peptides IgE-réactifs de 4-6 kDa ont été montrés résister à la digestion gastrique. Ces peptides ont pour origine des fragments du domaine hévéine. Leur IgE-réactivité a été prouvée tant in vitro qu’en tests cutanés .
On peut comprendre que, selon la réactivité du patient pour tel ou tel épitope sur l’hévéine, des réactions systémiques puissent être générées par les chitinases alimentaires chez certains sujets du fait de cette digestibilité incomplète.
L’hévéine du latex est-elle seule capable de générer une sensibilisation aux aliments ?
Différents points sont à aborder :
D’autres chitinases ont-elles une relevance clinique ?
- les chitinases de classe 3, telle l’hévamine du latex, ne semblent pas générer d’allergie autre que pour le latex lui-même.
- les chitinases de classe 2, comme les précédentes, n’ont pas de domaine hévéine. Cependant ces molécules ont une assez bonne homologie avec le domaine C-terminal des chitinases de classe 1.
- Des chitinases de classe 2 ont été identifiées dans l’avocat et la banane mais ne semblent pas avoir un rôle IgE-réactif important : elles n’inhibent que partiellement leur propre fruit et ne parviennent à positiver les tests cutanés que chez 2 patients/19 pour l’avocat (et aucun pour la banane)
- Cela pose d’ailleurs la question de l’IgE-réactivité de ces domaines C-terminaux : Posch trouve 3 sujets parmi 20 latex-avocat qui sont positifs pour Pers a 1 (la chitinase de l’avocat) sans être positifs pour l’hévéine. Et Diaz-Perales note que le domaine C-terminal de Cas s 5 (châtaigne) arrive à une relative inhibition de l’extrait châtaigne .
Le domaine C-terminal pourrait jouer un rôle dans la réactivité croisée entre chitinases, c’est-à-dire entre aliments, mais ce rôle reste pour le moment à confirmer.
- La réactivité d’un domaine C-terminal pourrait d’ailleurs provenir d’une sensibilisation à la chitinase classe 1 du latex, Hev b 11.
- Cependant la relevance clinique de cet allergène est elle-même très hypothétique. Par exemple, les sujets positifs pour Hev b 11 sont tous positifs pour l’hévéine , alors que ce n’est pas le cas dans le sens inverse.
- Il semble bien que la réactivité pour Hev b 11 soit une réactivité croisée de son domaine hévéine avec l’hévéine elle-même (Hev b 6.02).
Enfin quelques chitinases de classe 4 ont été montrées IgE-réactives (raisin, cèdre du Japon ).
- Ces chitinases possèdent un domaine hévéine et l’on s’attendrait à des réactions croisées avec l’hévéine.
- Cela ne semble pas être le cas comme il a été noté plus haut.
- Par ailleurs, le raisin n’est pas un fruit statistiquement associé à une sensibilisation au latex (cf. [Raisin et dérivés).
Quels éléments possède-t-on pour démontrer le rôle essentiel d’Hev b6.02 et du latex ?
- l’avocat, la banane ou la châtaigne n’inhibent qu’inconstamment le latex et que partiellement l’hévéine .
- des recombinants des domaines hévéine d’avocat et de banane (et aussi d’Hev b 11) ont été testés chez des sujets positifs pour l’hévéine : ils sont négatifs une fois sur deux .
- De plus une mono-réactivité pour ces domaines (= sans réactivité pour Hev b 6.02) est très rare .
- Force est de constater que l’hévéine du latex est très majoritairement le moteur de la réactivité à d’autres allergènes contenant un domaine hévéine.
Existe-t-il une explication à cette primauté de l’hévéine dans le syndrome latex-aliments ?
- Chen a fait l’hypothèse que certains épitopes de l’hévéine étaient absents dans les domaines hévéine croisants : l’hévéine aurait tous les épitopes nécessaires pour inhiber complètement les domaines hévéine, tandis que ces derniers ne possèderaient que certains épitopes capables de croiser efficacement avec l’hévéine.
- Un important travail d’une équipe finlandaise apporte crédit à cette hypothèse :
- malgré des pourcentages d’identité relativement élevés des domaines hévéine avocat et banane avec Hev b 6.02 (env. 73 %), des différences sont vues dans une représentation en 3D entre ces peptides (cf. figure). Un épitope est relativement bien conservé (Arg 5-Gln38), tandis que l’autre est différent dans l’avocat et la banane comparativement à l’hévéine.
- parallèlement, et de façon surprenante a priori, pour 11 sujets montrant un test cutané positif avec les domaines hévéine avocat ou latex, un seul n’est positif pour la chitinase complète correspondante.
Il semble donc que l’on soit en présence d’un double mécanisme (cf. figure) : un épitope moins affin sur les domaines hévéine des aliments et un masquage d’épitope du domaine hévéine par le domaine C-terminal dans la chitinase complète.
On aurait la gradation de réactivité suivante : hévéine Hev b 6.02 > domaines hévéine isolés (ex. recombinants) > domaines hévéine dans les chitinases complètes.
[1] - Merzendorfer H, Zimoch L. Chitin metabolism in insects: structure, function and regulation of chitin synthases and chitinases. J Exp Biol 2003;206:4393-4412
Chitin is one of the most important biopolymers in nature. It is mainly produced by fungi, arthropods and nematodes. In insects, it functions as scaffold material, supporting the cuticles of the epidermis and trachea as well as the peritrophic matrices lining the gut epithelium. Insect growth and morphogenesis are strictly dependent on the capability to remodel chitin-containing structures. For this purpose, insects repeatedly produce chitin synthases and chitinolytic enzymes in different tissues. Coordination of chitin synthesis and its degradation requires strict control of the participating enzymes during development. In this review, we will summarize recent advances in understanding chitin synthesis and its degradation in insects.
↩[2] - O’Neil SE, Heinrich TK, Hales BJ, Hazell LA, Holt DC, Fischer K, et al. The chitinase allergens Der p 15 and Der p 18 from Dermatophagoides pteronyssinus. Clin Exp Allergy 2006;36:831-839
BACKGROUND: House dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae cause allergic disease in humans as well as in dogs. In geographical regions where the two mite species coexist, they both elicit specific immunoglobulin (Ig E) responses in humans whereas dogs preferentially react to D. farinae extracts. In dogs the main IgE binding is directed to the D. farinae chitinase allergens Der f 15 and Der f 18 and not to the groups 1 and 2 allergens as found for humans. Although the IgE response of humans to Der f 18 has been investigated there is no report on Der f 15-specific IgE in humans .
OBJECTIVE: This study aimed to characterize the chitinase allergens Der p 15 and Der p 18 of D. pteronyssinus and to find out whether they are important allergens for humans .
METHODS: cDNA was cloned by a polymerase chain reaction strategy from D. pteronyssinus libraries using primers based on conserved chitinase sequences. IgE binding to the recombinant polypeptides was measured by immunosorbent assay. Mice were immunized with the polypeptides and cross-reactivity examined .
RESULTS: Two variants of Der p 15 were isolated, encoding mature proteins of 58.8 and 61.4 kDa. The amino acid sequences had 90% identity to Der f 15. The cDNA for Der p 18 encoded a mature protein of 49.2 kDa with 88% sequence identity to Der f 18. Der p 15-specific IgE was detected in 70% and Der p 18-specific IgE in 63% of a panel of 27 human allergic sera .
CONCLUSIONS: The D. pteronyssinus chitinases Der p 15 and Der p 18 show a high frequency of binding to IgE in allergic human sera. They are therefore potentially important allergens for humans as well as dogs.
↩[3] - Sutherland TE, Maizels RM, Allen JE. Chitinases ans chitinase-like proteins: potential therapeutic targets for the treatment of T-helper type type 2 allergies. Clin Exp Allergy 2009;39:943-955
Mammalian chitinase and chitinase-like proteins (CLPs) are a family of mediators increasingly associated with infection, T cell-mediated inflammation, wound healing, allergy and asthma. Although our current knowledge of the function of mammalian chitinases and CLPs is very limited, important information can be deduced from research carried out in lower organisms, and in different immunopathological conditions. Enzymatically active mammalian chitinase proteins may have evolved to degrade the copious amounts of chitin mammals are exposed to on a daily basis, and to form an innate barrier to chitin-containing organisms. CLPs are homologous to chitinases but lack the ability to degrade chitin. It is most striking that both chitinases and CLPs are up-regulated in T-helper type 2 (Th2)-driven conditions, and the first evidence is now emerging that these proteins may accentuate Th2 reactivity, and possibly contribute to the repair process that follows inflammation. Following studies demonstrating that chitinase inhibition leads to an attenuated allergic response, several strategies are being used to develop enzyme inhibitors for therapeutic use in human diseases. In this review, we will summarize recent insights into the effects of chitinases and CLPs in the context of Th2-dominated pathology with particular focus on allergy and asthma, discussing whether chitinase enzyme inhibitors may be of therapeutic value.
↩[4] - Shuhui L, Mok YK, Wong WS. Role of mammalian chitinases in asthma. Int Arch Allergy Immunol 2009;149:369-377
Asthma is a chronic inflammatory disease characterized by airway inflammation, mucus hypersecretion and airway hyperresponsiveness. Mechanisms underlying the pathogenesis of asthma are not fully understood. In recent years, there are mounting evidences demonstrating that mammalian chitinases may play a key role in mediating the T-helper 2 cell-driven inflammatory response that is commonly associated with asthma. Chitinases (e.g., chitotriosidase and acidic mammalian chitinase) are enzymes that degrade chitin, the second most abundant biopolymer that can be found in the cell walls of fungi, microfilarial sheaths of helminths, and exoskeletons of insects and crustaceans. There are also chitinase-like proteins (e.g., YKL-40, Ym1 and Ym2) that lack chitinolytic activity but retain chitin-binding ability. Therefore, chitinases were originally believed to function in host defense against parasitic infections, but the first discovery of their role in inflammatory airway diseases came as a surprise. There is ample evidence to support an association of acidic mammalian chitinase and YKL-40 with allergic bronchial asthma in patients. Our recent studies in a mouse asthma model revealed that anti-inflammatory drugs like corticosteroid and cysteinyl leukotriene receptor antagonist were able to suppress elevated pulmonary levels of mammalian chitinases. Taken together, mammalian chitinases may be useful as biomarkers for asthma. Notwithstanding, large-scale multi-center association studies are required to confirm this hypothesis. Besides, substantially more works using knockout mice, recombinant chitinases and siRNA technology are required to investigate a potential role of chitinases in the pathogenesis of asthma.
↩[5] - Henrissat B. Classification of chitinases modules. EXS 1999;87:137-156
Chitinases frequently display a modular structure featuring a catalytic domain attached to one or several ancillary noncatalytic domains whose function is often chitin binding. Gene cloning and DNA sequencing have allowed the determination of a massive number of amino acid sequences of chitinases during the last 10 years. This chapter presents a unifying classification system of the various chitinase modules that combines specific features of their sequences, three-dimensional structures and reaction mechanisms. [References: 41]
↩[6] - Sanchez-Monge R, Blanco C, Perales AD, Collada C, Carrillo T, Aragoncillo C, et al. Class I chitinases, the panallergens responsible for the latex-fruit syndrome, are induced by ethylene treatment and inactivated by heating. J Allergy Clin Immunol 2000;106:190-195
Class I chitinases have been identified as the major panallergens in fruits associated with the latex-fruit syndrome, such as avocado, banana, and chestnut. However, other plant foods containing these enzymes have not been related to this syndrome. OBJECTIVE: We sought out class I chitinases in the green bean, a legume that is known to express chitinases but is not associated with latex allergy, and examined whether the content or allergenic activity of chitinases can be modified by physical or chemical treatments.
METHODS: IgE-binding proteins in untreated bean samples, as well as in ethylene- and heat-treated samples, were detected by using a pool of sera from patients with latex-fruit allergy. Putative allergens were purified by cation-exchange chromatography and characterized by N-terminal sequencing, enzymatic activity assays, immunodetection with sera and antichitinase antibodies, and immunoblot inhibition tests. Skin prick tests with untreated and heated purified allergens were also carried out.
RESULTS: An IgE-binding protein of 32 kd that was also recognized by antichitinase antibodies was detected in green bean extracts. This reactive component was strongly induced by ethylene treatment. The protein, designated PvChI, was identified as a class I chitinase closely related to the major avocado allergen Prs a 1. Immunoblot inhibition assays demonstrated cross-reactivity between both allergens. Purified PvChI induced positive skin prick test responses in 7 of 8 patients with latex-fruit allergy.
Heat treatment of both Prs a 1 and PvChI produced a full loss of their allergenic capacities both in vitro and in vivo. No IgE-binding component was detected in the white mature bean in which the main isolated 32-kd protein corresponded to a nonreactive phytohemagglutinin.
CONCLUSIONS: Ethylene treatment induces the expression of plant class I chitinases. The allergenic activity of plant class I chitinases seems to be lost by heating. This fact could explain why plant foods containing these putative allergens that are consumed after cooking are not usually associated with the latex-fruit syndrome.
↩[7] - Malandain H, Lavaud F. Allergénicité des protéines de défense végétale. Rev Fr Allergol Immunol Clin 2004;44:469-475
La synthèse de protéines de défense fait partie des réponses biochimiques que les plantes ont développées pour lutter contre leurs ennemis naturels et contre les stress environnementaux. De nombreuses protéines de défense végétale sont allergisantes : chitinases, protéines de transfert lipidique LTP, protéines Bet v 1-like. Cet article rappelle les principales familles de protéines de défense végétale, leur impact allergique et l'effet de certains procédés agricoles ou technoalimentaires sur l'allergénicité des aliments végétaux.
↩[8] - Sanchez-Monge R, Diaz-Perales A, Blanco C, Salcedo G. Class I chitinases and the latex fruit syndrome. Internet Symp Food Allergens 2000;2(3):137-144 ↩
[9] - Diaz-Perales A, Collada C, Blanco C, Sanchez-Monge R, Carrillo T, Aragoncillo C, et al. Class I chitinases with hevein-like domain, but not class II enzymes, are relevant chestnut and avocado allergens. J Allergy Clin Immunol 1998;102:127-133
BACKGROUND: Several foods associated with the latex-fruit syndrome present relevant allergens of around 30 kd. Neither these components nor any other responsible for the reported cross-reactions have been identified and purified. OBJECTIVE: We sought to isolate and characterize the 30 kd allergens from avocado fruit and chestnut seed, two of the main allergenic foods linked with latex allergy.
METHODS: Sera from patients allergic to chestnut and avocado were selected according to clinical symptoms, specific IgE levels, and positive skin prick test responses. Class I and II chitinases were purified by affinity and cation-exchange chromatography and characterized by specific IgE and anti-chitinase immunodetection, immunoblot inhibition assays, enzymatic activity tests, and N-terminal sequencing.
RESULTS: Relevant 32 kd allergens were detected by specific IgE immunodetection in both avocado and chestnut crude extracts. The same bands, together with others of 25 kd, were revealed by a monospecific antiserum against class II chitinases. Purification and characterization of the 32 kd allergens from both plant sources allowed their identification as class I chitinases with an N-terminal hevein-domain. The purified allergens fully inhibited IgE binding by the corresponding crude extract when tested in immunoblot inhibition assays. Highly related 25 kd class II chitinases that lack the hevein-like domain were also isolated from the same protein preparations. No IgE-binding capacity was shown by these class II enzymes. CONCLUSION: Class I chitinases are relevant allergens of avocado and chestnut and could be the panallergens responsible for the latex-fruit syndrome. The hevein-like domain seems to be involved in their allergenic reactivity.
↩[10] - Chen Z, Posch A, Cremer R, Raulf-Heimsoth M, Baur X. Identification of hevein (Hev b 6,02) in Hevea latex as a major cross-reacting allergen with avocado fruit in patients with latex allergy. J Allergy Clin Immunol 1998;102:476-481
BACKGROUND: Recent studies demonstrated that allergy to natural rubber latex is frequently associated with hypersensitivity to avocado fruit. The responsible cross-sensitizing allergen has not been identified.
OBJECTIVE: The purpose of this study was to investigate the cross-reactivity of a latex major allergen, hevein, with avocado proteins.
METHODS: Serum samples from 118 health care workers (HCWs) allergic to latex (HCW group) and 78 patients with spina bifida (SB) allergic to latex (SB group) were included in this study. Anti-hevein and anti-avocado IgE antibodies were measured by enzyme-linked allergosorbent assay. Cross-reactivity of hevein to avocado proteins was assessed by inhibition of the IgE binding in individual patients' sera containing IgE antibodies to both hevein and avocado.
RESULTS: The prevalence of seropositive IgE antibodies to avocado was found to be strongly associated with the presence of hevein-specific IgE antibodies in subjects of both groups (P < .001). Sixty-seven of 91 (73%) subjects from the HCW group and all 19 subjects in the SB group with positive IgE antibodies to hevein also had elevated IgE values to avocado. Competitive RAST inhibition with 42 sera showed that IgE binding to avocado could be completely inhibited in 27 (64%) sera by preincubation with hevein. By contrast, the degrees of inhibition of IgE to hevein by avocado extract ranged from 0% to 36% (n = 16). These results indicate that sensitization to avocado in most patients allergic to latex is caused exclusively by IgE-binding epitopes present in hevein. Results of immunoblots and immunoblot inhibition with 11 serum samples confirmed that a 30-kd protein in avocado was the major IgE-binding component; the IgE-binding reactivity to this protein could be inhibited by hevein in all sera tested.
CONCLUSION: Hevein is the major cross-reacting allergen with avocado in subjects with latex allergy.
↩[11] - Posch A, Wheeler CH, Chen Z, Flagge A, Dunn MJ, Papenfuss F, et al. Class I endochitinase containing a hevein domain is the causative allergen in latex-associated avocado allergy. Clin Exp Allergy 1999;29:667-672
BACKGROUND: In the medical literature immunoglobulin (Ig)E-mediated sensitization to avocado is rarely reported. On the other hand, more than 50% of subjects having IgE-mediated natural rubber latex allergy are sensitized to avocado fruit as demonstrated by skin-prick testing and/or specific IgE measurements and about 10-20% report hypersensitivity reactions after ingesting avocado. OBJECTIVE: The underlying pathomechanism of latex-associated avocado allergy is still unknown. The conserved hevein domain of the major latex allergen prohevein (Hev b 6.01) is a ubiquitous chitin-binding protein structure that can be found in several plant proteins and may be responsible for the observed cross-reactivity between latex and avocado fruit.
METHODS: Chitin-binding avocado proteins (CBAPs) were isolated by affinity-chromatography and their IgE-binding characteristics were studied by immunoblotting using the sera from 15 avocado-sensitized latex patients. Inhibition experiments using isolated hevein and CBAPs as inhibitor solutions were performed to study the immunological cross-reactivity between both protein species and to assess the role of the CBAPs as mediators in latex-associated avocado allergy.
RESULTS: In 80% of avocado-sensitized subjects (n = 15), IgE antibodies directed against a 31-kDa allergen were detected by immunoblotting. This IgE-binding protein was identified by protein sequencing to be a class I endochitinase containing a hevein domain at the N-terminus. Purified native and digested (using simulated gastric fluid) endochitinase were able to completely block all avocado-specific IgE antibodies in six out of seven avocado patients.
CONCLUSIONS: Sensitization to endochitinase class I containing a hevein domain is the main underlying pathomechanism in latex-mediated avocado allergy.
↩[12] - Posch A, Wheeler CH, Chen Z, Flagge A, Dunn MJ, Papenfuss F, et al. Class I endochitinase containing a hevein domain is the causative allergen in latex-associated avocado allergy. Clin Exp Allergy 1999;29:667-672
BACKGROUND: In the medical literature immunoglobulin (Ig)E-mediated sensitization to avocado is rarely reported. On the other hand, more than 50% of subjects having IgE-mediated natural rubber latex allergy are sensitized to avocado fruit as demonstrated by skin-prick testing and/or specific IgE measurements and about 10-20% report hypersensitivity reactions after ingesting avocado. OBJECTIVE: The underlying pathomechanism of latex-associated avocado allergy is still unknown. The conserved hevein domain of the major latex allergen prohevein (Hev b 6.01) is a ubiquitous chitin-binding protein structure that can be found in several plant proteins and may be responsible for the observed cross-reactivity between latex and avocado fruit.
METHODS: Chitin-binding avocado proteins (CBAPs) were isolated by affinity-chromatography and their IgE-binding characteristics were studied by immunoblotting using the sera from 15 avocado-sensitized latex patients. Inhibition experiments using isolated hevein and CBAPs as inhibitor solutions were performed to study the immunological cross-reactivity between both protein species and to assess the role of the CBAPs as mediators in latex-associated avocado allergy.
RESULTS: In 80% of avocado-sensitized subjects (n = 15), IgE antibodies directed against a 31-kDa allergen were detected by immunoblotting. This IgE-binding protein was identified by protein sequencing to be a class I endochitinase containing a hevein domain at the N-terminus. Purified native and digested (using simulated gastric fluid) endochitinase were able to completely block all avocado-specific IgE antibodies in six out of seven avocado patients.
CONCLUSIONS: Sensitization to endochitinase class I containing a hevein domain is the main underlying pathomechanism in latex-mediated avocado allergy.
↩[13] - Yagami T, Haishima Y, Nakamura A, Osuna H, Ikezawa Z. Digestibility of allergens extracted from natural rubber latex and vegetable foods. J Allergy Clin Immunol 2000;106:752-762
BACKGROUND: Several cross-reactive allergens are now known to be involved in the defense responses of higher plants. Such proteins are drawing the attention of plant breeders because of their antimicrobial or stress-alleviating activities. Plants genetically modified to express defense-related proteins are being developed. The current concern is focused on the allergenicity of these intentionally expressed proteins.
OBJECTIVE: It is believed that food allergens are proteins resistant to digestion. Digestibility tests have been accepted as an appropriate method for evaluating the allergenicity of newly introduced proteins. In this study we investigated the usefulness of this method for detecting allergens from natural rubber latex and vegetable foods.
METHODS: Proteins were extracted from rubber latex, potato, and 5 kinds of fruits. Simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were used for the digestibility test. An aliquot of each digest was periodically withdrawn and analyzed. Allergens were detected with pooled sera from individuals with latex allergy or patients given a diagnosis of oral allergy syndrome.
RESULTS: Most latex and vegetable food proteins were digested by the SGF within 4 minutes. Numerous allergens were also decomposed by the SGF within 8 minutes. Although vegetable food allergens were relatively stable in the SIF, kiwi allergens were substantially degraded by the SIF within 16 hours. CONCLUSION: The pronounced lability of the plant-derived allergens was thought to reflect the discrete sensitization and elicitation processes of patients with latex-fruit syndrome or oral allergy syndrome. These results indicate that the allergenicity of a newly expressed protein should be carefully evaluated according to not only its digestibility but also other important properties.
↩[14] - Diaz-Perales A, Blanco C, Sanchez-Monge R, Varela J, Carrillo T, Salcedo G. Analysis of avocado allergen (Prs a 1) IgE-binding peptides generated by simulated gastric fluid digestion. J Allergy Clin Immunol 2003;112:1002-1007
BACKGROUND: Resistance to pepsin digestion has been claimed to be a characteristic of food allergens that can induce severe adverse reactions. Moreover, pepsin treatment is included in protocols to evaluate the potential allergenicity of transgenic foods. Allergenic plant class I chitinases, such as avocado Prs a 1, are the panallergens involved in the latex-fruit syndrome. Previous reports indicated their susceptibility to simulated gastric fluid (SGF) digestion. OBJECTIVE: We sought to evaluate the IgE-binding capacity and the in vivo reactivity of the SGF products of the avocado allergen Prs a 1.
METHODS: Patients with a clinical history of latex-fruit allergy syndrome, a positive skin prick test (SPT) response to Prs a 1, and specific IgE to avocado were selected. Untreated and SGF-digested Prs a 1 samples were analyzed by means of IgE and IgG immunoblotting, IgE immunoblotting and ELISA-inhibition assays, and SPTs. Peptides from SGF-digested samples were fractionated by means of HPLC, characterized by N-terminal amino acid sequencing and matrix-assisted laser desorption/ionization analysis, and tested for in vivo reactivity with SPTs.
RESULTS: Neither protein staining nor IgE immunoblotting with a pool of sera from allergic patients resulted in the detection of any band after SDS-PAGE separation of an SGF-digested sample of Prs a 1. However, this sample showed a similar inhibitory potency to that of untreated Prs a 1 in both immunoblot- and ELISA-inhibition assays (up to 70% inhibition of the IgE binding to crude avocado extract) and induced positive SPT responses in 5 of 8 allergic patients. Peptides from SGF-digested Prs a 1 were separated by means of HPLC, and 4 of them reached more than 50% inhibition values when using avocado extract as the solid phase in ELISA-inhibition assays. Reactive peptides were located both in the N-terminal hevein-like domain and in the catalytic domain of Prs a 1. Those corresponding to the hevein-like domain (approximately 5100 d) produced positive SPT responses in 5 of 8 allergic patients, whereas 2 peptides located in the catalytic domain (approximately 1400 and 2500 d) were reactive in 2 or 3 of the 8 patients. CONCLUSION: Prs a 1 was extensively degradated when subjected to SGF digestion. However, the resulting peptides, particularly those corresponding to the hevein-like domain, were clearly reactive both in vitro and in vivo.
↩[15] - Diaz-Perales A, Collada C, Blanco C, Sanchez-Monge R, Carrillo T, Aragoncillo C, et al. Class I chitinases with hevein-like domain, but not class II enzymes, are relevant chestnut and avocado allergens. J Allergy Clin Immunol 1998;102:127-133
BACKGROUND: Several foods associated with the latex-fruit syndrome present relevant allergens of around 30 kd. Neither these components nor any other responsible for the reported cross-reactions have been identified and purified. OBJECTIVE: We sought to isolate and characterize the 30 kd allergens from avocado fruit and chestnut seed, two of the main allergenic foods linked with latex allergy.
METHODS: Sera from patients allergic to chestnut and avocado were selected according to clinical symptoms, specific IgE levels, and positive skin prick test responses. Class I and II chitinases were purified by affinity and cation-exchange chromatography and characterized by specific IgE and anti-chitinase immunodetection, immunoblot inhibition assays, enzymatic activity tests, and N-terminal sequencing.
RESULTS: Relevant 32 kd allergens were detected by specific IgE immunodetection in both avocado and chestnut crude extracts. The same bands, together with others of 25 kd, were revealed by a monospecific antiserum against class II chitinases. Purification and characterization of the 32 kd allergens from both plant sources allowed their identification as class I chitinases with an N-terminal hevein-domain. The purified allergens fully inhibited IgE binding by the corresponding crude extract when tested in immunoblot inhibition assays. Highly related 25 kd class II chitinases that lack the hevein-like domain were also isolated from the same protein preparations. No IgE-binding capacity was shown by these class II enzymes. CONCLUSION: Class I chitinases are relevant allergens of avocado and chestnut and could be the panallergens responsible for the latex-fruit syndrome. The hevein-like domain seems to be involved in their allergenic reactivity.
↩[16] - Blanco C, Diaz-Perales A, Collada C, Sanchez-Monge R, Aragoncillo C, Castillo R, et al. Class I chitinases as potential panallergens involved in the latex-fruit syndrome. J Allergy Clin Immunol 1999;103:507-513
BACKGROUND: Latex-fruit cross-sensitization has been fully demonstrated.
However, the antigens responsible for this "latex-fruit syndrome" have not been identified. We have recently shown that class I chitinases are relevant chestnut and avocado allergens. OBJECTIVE: We sought to evaluate the in vivo and in vitro reactions of purified chestnut and avocado chitinases in relation to the latex-fruit syndrome.
METHODS: From a latex-allergic population, eighteen patients allergic to chestnut, avocado, or both were selected. Skin prick tests (SPTs) were performed with crude chestnut and avocado extracts, chitinase-enriched preparations, and purified class I and II chitinases from both fruits. CAP-inhibition assays with the crude extracts and purified proteins were carried out.
Immunodetection with sera from patients with latex-fruit allergy and immunoblot inhibition tests with a latex extract were also performed.
Eighteen subjects paired with our patients and 15 patients allergic to latex but not food were used as control groups.
RESULTS: The chestnut class I chitinase elicited positive SPT responses in 13 of 18 patients with latex-fruit allergy (72%), and the avocado class I chitinase elicited positive responses in 12 of 18 (67%) similarly allergic patients. By contrast, class II enzymes without a hevein-like domain did not show SPT responses in the same patient group. Each isolated class I chitinase reached inhibition values higher than 85% in CAP inhibition assays against the corresponding food extract in solid phase. Immunodetection of the crude extracts and the purified class I chitinases revealed a single 32-kd band for both chestnut and avocado. Preincubation with a natural latex extract fully inhibited the IgE binding to the crude extracts, as well as to the purified chestnut and avocado class I chitinases. CONCLUSION: Chestnut and avocado class I chitinases with an N-terminal hevein-like domain are major allergens that cross-react with latex. Therefore they are probably the panallergens responsible for the latex-fruit syndrome.
↩[17] - Blanco C, Diaz-Perales A, Collada C, Sanchez-Monge R, Aragoncillo C, Castillo R, et al. Class I chitinases as potential panallergens involved in the latex-fruit syndrome. J Allergy Clin Immunol 1999;103:507-513
BACKGROUND: Latex-fruit cross-sensitization has been fully demonstrated.
However, the antigens responsible for this "latex-fruit syndrome" have not been identified. We have recently shown that class I chitinases are relevant chestnut and avocado allergens. OBJECTIVE: We sought to evaluate the in vivo and in vitro reactions of purified chestnut and avocado chitinases in relation to the latex-fruit syndrome.
METHODS: From a latex-allergic population, eighteen patients allergic to chestnut, avocado, or both were selected. Skin prick tests (SPTs) were performed with crude chestnut and avocado extracts, chitinase-enriched preparations, and purified class I and II chitinases from both fruits. CAP-inhibition assays with the crude extracts and purified proteins were carried out.
Immunodetection with sera from patients with latex-fruit allergy and immunoblot inhibition tests with a latex extract were also performed.
Eighteen subjects paired with our patients and 15 patients allergic to latex but not food were used as control groups.
RESULTS: The chestnut class I chitinase elicited positive SPT responses in 13 of 18 patients with latex-fruit allergy (72%), and the avocado class I chitinase elicited positive responses in 12 of 18 (67%) similarly allergic patients. By contrast, class II enzymes without a hevein-like domain did not show SPT responses in the same patient group. Each isolated class I chitinase reached inhibition values higher than 85% in CAP inhibition assays against the corresponding food extract in solid phase. Immunodetection of the crude extracts and the purified class I chitinases revealed a single 32-kd band for both chestnut and avocado. Preincubation with a natural latex extract fully inhibited the IgE binding to the crude extracts, as well as to the purified chestnut and avocado class I chitinases. CONCLUSION: Chestnut and avocado class I chitinases with an N-terminal hevein-like domain are major allergens that cross-react with latex. Therefore they are probably the panallergens responsible for the latex-fruit syndrome.
↩[18] - Posch A, Wheeler CH, Chen Z, Flagge A, Dunn MJ, Papenfuss F, et al. Class I endochitinase containing a hevein domain is the causative allergen in latex-associated avocado allergy. Clin Exp Allergy 1999;29:667-672
BACKGROUND: In the medical literature immunoglobulin (Ig)E-mediated sensitization to avocado is rarely reported. On the other hand, more than 50% of subjects having IgE-mediated natural rubber latex allergy are sensitized to avocado fruit as demonstrated by skin-prick testing and/or specific IgE measurements and about 10-20% report hypersensitivity reactions after ingesting avocado. OBJECTIVE: The underlying pathomechanism of latex-associated avocado allergy is still unknown. The conserved hevein domain of the major latex allergen prohevein (Hev b 6.01) is a ubiquitous chitin-binding protein structure that can be found in several plant proteins and may be responsible for the observed cross-reactivity between latex and avocado fruit.
METHODS: Chitin-binding avocado proteins (CBAPs) were isolated by affinity-chromatography and their IgE-binding characteristics were studied by immunoblotting using the sera from 15 avocado-sensitized latex patients. Inhibition experiments using isolated hevein and CBAPs as inhibitor solutions were performed to study the immunological cross-reactivity between both protein species and to assess the role of the CBAPs as mediators in latex-associated avocado allergy.
RESULTS: In 80% of avocado-sensitized subjects (n = 15), IgE antibodies directed against a 31-kDa allergen were detected by immunoblotting. This IgE-binding protein was identified by protein sequencing to be a class I endochitinase containing a hevein domain at the N-terminus. Purified native and digested (using simulated gastric fluid) endochitinase were able to completely block all avocado-specific IgE antibodies in six out of seven avocado patients.
CONCLUSIONS: Sensitization to endochitinase class I containing a hevein domain is the main underlying pathomechanism in latex-mediated avocado allergy.
↩[19] - Dìaz-Perales A, Sánchez-Monge R, Blanco C, Lombardero M, Carillo T, Salcedo G. What is the role of the hevein-like domain of fruit class I chitinases in their allergenic capacity ? Clin Exp Allergy 2002;32:448-454
Class I chitinases are the major panallergens in fruits associated with the latex-fruit syndrome. These enzymes contain an N-terminal hevein-like domain homologous to latex hevein, and a larger catalytic domain. The role of these domains in their allergenic capacity is still controversial.
Objective : We sought to evaluate the role of both domains of class I chitinases in their IgE-binding properties, using Cas s 5, the major allergen from chestnut, as a model.
Method s : Recombinant Cas s 5 and its deleted form, lacking the hevein-like domain, designated rCat, were expressed in Pichia pastoris using the pPIC 9 vector. Both recombinant products were purified from the supernatants of transformed yeast cultures by gel-filtration and cation-exchange chromatography. The isolated proteins were characterized by N-terminal sequencing, enzymatic activity and N-glycosylation tests, anti-chitinase and specific IgE immunodetection. Immunoblot, RAST and CAP inhibition assays were also performed.
Result s : Both purified rCas s 5 and rCat showed the expected N-terminal amino acid sequences and an enzymatic activity similar to that of their natural counterparts isolated from chestnut seeds, and were strongly recognized by anti-chitinase antibodies. In contrast, only rCas s 5, but not rCat, bound specific IgE from sera of patients suffering from the latex-fruit syndrome, and fully inhibited IgE-binding to natural Cas s 5 in immunoblot inhibition assays. Latex hevein also exerted a strong immunoblot inhibition of IgE-binding to chestnut Cas s 5. RAST and CAP inhibition using whole chestnut extract on the solid phase, rendered inhibition levels around 70-90% for rCas s 5 and 60% for rCat, in contrast to the immunoblotting results.
Conclusions : Recombinant Cas s 5 behaves like natural Cas s 5 in IgE-binding assays in vitro. The hevein-like domain of allergenic class I chitinases seems to include all their main IgE-binding epitopes when tested by immunodetection and immunoblot inhibition experiments. RAST and CAP inhibition assays, on the contrary, suggest that relevant epitopes are also harboured in the catalytic domain of these allergens.
↩[20] - O'Riordain G, Radauer C, Hoffmann-Sommergruber K, Adhami F, Peterbauer CK, Blanco C, et al. Cloning and molecular characterization of the Hevea brasiliensis allergen Hev b 11, a class I chitinase. Clin Exp Allergy 2002;32:455-462
In the last 10 years type-I allergy against proteins from Hevea brasiliensis latex has become an acknowledged medical issue. Fruit-allergic patients represent one risk group for developing latex allergy. Class I chitinases have been identified from chestnut, avocado and banana as relevant allergens. The chitin binding (hevein) domain from these class I chitinases has been postulated to bear the important IgE binding epitopes.
Objective : To clone the cDNA of an allergenic latex class I chitinase, to express the recombinant protein and to determine its IgE cross-reactivity with hevein (Hev b 6.02).
Method s : A full-length cDNA coding for a class I chitinase has been isolated from Hevea latex RNA by reverse transcription followed by PCR. The chitinase encoding sequence has been subcloned into the pMAL expression vector and expressed in E. coli as a fusion protein to maltose binding protein. The highly enriched recombinant protein fraction has been tested for its IgE binding capacity in immunoblots and ELISA. Furthermore, the pathogenesis-related function of the recombinant protein was tested in a fungal growth inhibition assay.
Result s : The Hevea brasiliensis latex chitinase, designated Hev b 11, displays 70% identity to the endochitinase from avocado and its hevein-domain 58% to hevein (Hev b 6.02). The recombinant Hev b 11-maltose binding protein is recognized by latex- and fruit-allergic patients with IgE binding in both, ELISA and immunoblots. Pre-incubation of sera with rHev b 11-maltose binding protein showed an overall 16% inhibition of subsequent binding to rHev b 6.02-maltose binding protein on solid phase. The growth of F. oxysporum was inhibited in a dose dependent manner by addition of rHev b 11-maltose binding protein to the culture.
Conclusions : Hev b 11, a class I chitinase, is another allergen from Hevea latex with a chitin binding domain and displays a different IgE binding capacity compared with hevein.
↩[21] - Fujimura T, Shigeta S, Suwa T, Kawamoto S, Aki T, Masubuchi M, et al. Molecular cloning of a class IV chitinase allergen from Japanese cedar (Cryptomeria japonica) pollen and competitive inhibition of its immunoglobulin E-binding capacity by latex C-serum. Clin Exp Allergy 2005;35:234-243
Summary Background Japanese cedar (Cryptomeria japonica) pollinosis is one of the most prevalent allergic diseases in Japan. Only three C. japonica allergens, Cry j 1, Cry j 2, and CJP-6, have been characterized. The full IgE-binding spectrum of C. japonica pollen allergens demonstrates that many allergens remain to be identified. Objective The aim of this study was to characterize a novel allergen with a high frequency of IgE binding. Methods The cDNA coding for a high-frequency IgE-binding protein, designated CJP-4, was cloned from the total mRNA of C. japonica pollen. The corresponding native allergen was purified by affinity precipitation with colloidal chitin and gel chromatography. The IgE-binding ability of purified native CJP-4 was characterized by ELISA and ELISA inhibition. Results The CJP-4 cDNA encoded 281 amino acids with significant sequence homology to class IV chitinases. Purified native CJP-4, migrated as a homogeneous 34-kDa protein on SDS-PAGE, revealed endochitinase activity on native PAGE. The purified protein displayed the ability to bind IgE from all patients tested (31/31) in ELISA, whereas Cry j 1 bound to IgE at a 71% frequency (22/31). Pre-incubation with latex C-serum completely inhibited the reaction of pooled sera IgE from patients with C. japonica pollinosis and/or latex allergy to purified CJP-4. Conclusion We identified CJP-4 as a novel and fourth C. japonica chitinase allergen with high IgE-binding frequency. The competitive IgE-binding profile between C. japonica chitinase and latex C-serum indicated that C. japonica chitinase should be an important pan-allergen in C. japonica pollen.
↩[22] - Möller M, Kayma M, Vieluf D, Paschke A, Steinhart H. Determination and characterization of cross-reacting allergens in latex, avocado, banana, and kiwi fruit. Allergy 1998;53:289-296
Sera of 11 patients were used to characterize allergens in kiwi fruit, latex, avocado, and banana by SDS-PAGE/immunoblotting and to determine cross-reactions between these allergen extracts in EAST inhibition and immunoblot inhibition. By SDS-PAGE/immunoblotting, allergens with apparent molecular weights of 21, 38, 40, and 42 kDa were visualized in latex extract. In avocado extract, IgE-binding components of 27, 43, 52, 58, 65, 75, and 88 kDa were to be seen, whereas, in banana extract, a 40-kDa protein showed strong IgE binding. Furthermore, allergens of 52, 58, 88, and 94 kDa were detected in the extract of banana. Cross-reactions between these allergen extracts were determined by EAST inhibition. Immunoblot inhibition demonstrated that almost all IgE-reactive bands in nitrocellulose-blotted latex, avocado, and banana extracts and two components of 43 and 67 kDa in kiwi fruit shared common IgE epitopes.
↩[23] - Makinen-Kiljunen S. Banana allergy in patients with immediate-type hypersensitivity to natural rubber latex. J Allergy Clin Immunol 1994;93:990-996
BACKGROUND: An association between allergy to latex and banana has been reported. Even though cross-reacting IgE antibodies have been demonstrated, in no study has the existence of structurally similar allergens been confirmed. In the present study banana allergy was studied in a large series of patients with latex allergy. Specific IgE antibodies were characterized for cross-reactivity and compared with pollen RAST results. Latex and banana extracts were investigated for common antigens and allergens .
METHODS: Latex-, banana-, and pollen-specific (birch, timothy, mugwort) IgE were measured in 47 sera from patients with latex allergy. Thirty-one patients were skin prick tested with banana and questioned for possible reactions after eating bananas. Several RAST inhibition and immunospot inhibition studies were used to characterize cross-reacting IgE antibodies. Structurally similar antigens and allergens were evaluated with crossed-line immunoelectrophoresis and crossed-line radioimmunoelectrophoresis, respectively .
RESULTS: Latex RAST results were positive in 31 (66%) and banana RAST results were positive in 26 (55%) of the 47 sera. Of the 31 latex RAST-positive sera, 25 (81%) were also banana RAST-positive. Results from latex RAST correlated significantly with results from banana RAST (p < 0.001), but not with those from pollen RAST (p > 0.05). Banana skin prick test results were positive in 11 (35%) of the 31 patients tested. Symptoms after eating bananas were reported by 16 (52%) of the 31 patients. In inhibition studies the binding of IgE antibodies to solid-phase banana and to several latex preparations was inhibited by latex and banana, respectively. In crossed-line immunoelectrophoresis at least one antigen from banana fused with an antigen from latex, which also bound IgE antibodies in autoradiography (crossed-line radioimmunoelectrophoresis) .
CONCLUSIONS: Patients with latex allergy have symptoms caused by banana and show positive skin test and specific IgE test results. Cross-reacting IgE antibodies were confirmed by several inhibition techniques. For the first time, a structurally similar antigen/allergen was demonstrated.
↩[24] - Rodriguez M, Vega F, Garcia MT, Panizo C, Laffond E, Montalvo A, et al. Hypersensitivity to latex, chestnut, and banana. Ann Allergy 1993;70:31-34
The incidence of latex-allergic patients is probably higher than suspected. A spectrum of IgE-dependent allergic reactions to latex products including urticaria, rhinitis, asthma, angioedema, and life-threatening anaphylaxis has been increasingly reported in recent years. We describe three patients with rubber hypersensitivity and allergy to fruit (banana and chestnut). Immediate positive responses were obtained in prick tests with latex, banana, and chestnut extracts. Histamine release was positive and specific IgE antibodies to all three extracts were detected by fluorescence radioimmunoassay. In the RAST-inhibition studies, the extract of latex inhibited the binding of chestnut and banana, but chestnut and banana extracts did not inhibit the binding of latex. These results suggest a sensitivity to crossreacting antigens in latex allergy associated with allergy to certain fruits.
↩[25] - Brehler R, Theissen U, Mohr C, Luger T. 'Latex-fruit syndrome': frequency of cross-reacting IgE antibodies. Allergy 1997;52:404-410
An association between allergies to latex proteins and to various foods has been reported and confirmed by RAST and immunoblotting inhibition. However, no significant data had been collected on the frequency of specific IgE antibodies to fruits in these patients and the frequency of a history of fruit intolerance. Serum samples of 136 patients with well-documented, clinically relevant, immediate-type hypersensitivity against latex proteins were analyzed for IgE antibodies against a panel of different fruits. Patient history of food intolerance was documented by a standardized questionnaire. Fruit-specific IgE antibodies were detected in 69.1% of serum samples. Cross-reacting IgE antibodies recognizing latex and fruit allergens (papaya. avocado, banana, chestnut, passion fruit, fig. melon, mango, kiwi, pineapple, peach, and tomato) were demonstrated by RAST-inhibition tests. Of our patients 42.6% reported allergic symptoms after ingestion of these fruits and a total of 112 intolerance reactions were recorded. However, fruit-specific IgE antibodies were detected only in serum samples from 32.1% of the patients who perceived symptoms due to these fruits. Thus, serologic tests seem to be of low significance for prediction of food allergy in latex-allergic patients.
↩[26] - Salcedo G, Diaz-Perales A, Sanchez-Monge R. The role of plant panallergens in sensitization to natural rubber latex. Curr Opin Allergy Clin Immunol 2001;1:177-183
Latex allergy represents an increasing occupational problem, mainly among healthcare workers. An association between latex allergy and hypersensitivity to some plant foods, particularly fruits (the latex-fruit syndrome), has been established. Class I chitinases with an N-terminal hevein-like domain from avocado, chestnut, banana and other foods, and latex hevein seem to be the allergens responsible for the cross-reactions involved in the latex-fruit syndrome. The potential role of other latex allergens, such as profilin, Hev b 5, Hev b 7 and beta-1,3-glucanases, in the co-sensitization to latex and plant foods is also discussed.
↩[27] - Adhami F, Leitzenberger I, Wagner S, Scheiner O, Breiteneder H. Recombinant hevein and hevein-like domains from Hevea latex, avocado and banana bind cross-reactive IgE from latex-allergic patients. EAACI 21th Congress, Naples, 1-5 June, 2002, Poster n°226
The potential role of class I chitinases as major panallergens involved in the latex fruit syndrome has been well demonstrated. The high sequence identity among the major latex allergen hevein and the hevein-like domains at the N-termini of class I chitinases suggested an essential role of hevein and hevein-like domains as the main allergens involved in the latex fruit syndrome. The purpose of this study was the production of recombinant hevein (Hev b 6.02), and the hevein-like domains of latex (Hev b 11- Hev), avocado (Avo-Hev) and banana (Ba-Hev) class I chitinases to examine the cross-reactivity between these allergens. These proteins fused to the maltose-binding protein and were expressed in E. coli XL1 blue cells using the expression vector pMAL-p2 and purified by amylose affi- nity chromatography. Sera from 104 patients sensitized to latex B extract proteins were included in this study. The ELISA assays indicated that 52 (50%) of 104 tested sera possessed IgE directed to rHev b 6.02/MBP. Twenty-eight of rHev b 6.02 positive patients (56%) displayed specific IgE to rHev b 11-Hev/MBP, 26 patients (50%) revealed positive IgE-binding signals to rBa-Hev/MBP and 24 patients (44%) had specific IgE to rAvo-Hev/MBP. A high inhibition level of IgE binding to hevein-like proteins was achieved using hevein as inhibitor, whereas only a weak inhibition could be detected in the opposite way. The obtained results confirm the relevance of latex, avocado and banana class I chitinases for the latex fruit syndrome and indicate the key role of hevein-like domains for the allergenic cross-reactivities of these proteins.
↩[28] - Radauer C, Wagner S, Allwardt D, Adhami F, Leitzenberger I, Hafner C, et al. Determination of the cross-reactivity between the major latex allergen hevein and hevein-like domains of class I chitinases in a group of latex allergic patients. Allergy Clin Immunol Int 2005;17(Suppl. 1):45
Background: About one half of latex-allergic patients suffer from adverse reactions towards several plant foods including avocado, banana, chestnut, and kiwi fruit. This so-called latex-fruit syndrome is commonly attributed to IgE cross-reactivity between the major latex allergen hevein (Hev b 6.02) and fruit class I chitinases that contain an N-terminal chitin-binding domain homologous to hevein. Several IgE-binding class I chitinases have been characterised as natural or recombinant products. However, serological data on their cross-reactivities with hevein using a larger sample of latex allergic patients' sera are still missing.
Methods: We used a panel of 60 sera of patients with latex allergy confirmed by positive case histories and positive skin prick tests or glove provocation tests. All sera were tested in an IgE ELISA with recombinant hevein and the recombinant hevein-like domains derived from the class I chitinases from latex (Hev b 11-Hev), banana (Mus xp-Hev), and avocado (Pers a 1-Hev). The recombinant allergens were expressed in Escherichia coli as fusion proteins with the maltose binding protein using the pMal system.
Results: Forty-five of the 60 sera (75%) contained IgE specific for hevein. The frequencies of sensitisation to Hev b 11-Hev, Mus xp-Hev and Pers a 1-Hev were 31 (52%), 27 (45%), and 31 (52%), respectively. Only two patients contained low amounts of IgE specific for the hevein-like domains from banana or avocado chitinases without concomitant hevein sensitisation. In contrast, 13 patients' sera (22%) reacted exclusively to hevein. The amounts of IgE binding to different chitinase-derived hevein-like domains were highly correlated. The frequencies of reported adverse reactions to banana and avocado were 23% and 17%. Nevertheless, no significant connection between sensitisation to hevein-like domains and food allergy symptoms could be observed.
Conclusion: Our data suggest that the production of cross-reactive IgE directed to hevein and hevein-like chitin-binding domains is in most cases caused by primary sensitisation to hevein. The missing association between sensitisation to hevein and symptoms of food allergy puts the clinical relevance of heveinlike domains as allergens into question.
↩[29] - Chen Z, Posch A, Cremer R, Raulf-Heimsoth M, Baur X. Identification of hevein (Hev b 6,02) in Hevea latex as a major cross-reacting allergen with avocado fruit in patients with latex allergy. J Allergy Clin Immunol 1998;102:476-481
BACKGROUND: Recent studies demonstrated that allergy to natural rubber latex is frequently associated with hypersensitivity to avocado fruit. The responsible cross-sensitizing allergen has not been identified.
OBJECTIVE: The purpose of this study was to investigate the cross-reactivity of a latex major allergen, hevein, with avocado proteins.
METHODS: Serum samples from 118 health care workers (HCWs) allergic to latex (HCW group) and 78 patients with spina bifida (SB) allergic to latex (SB group) were included in this study. Anti-hevein and anti-avocado IgE antibodies were measured by enzyme-linked allergosorbent assay. Cross-reactivity of hevein to avocado proteins was assessed by inhibition of the IgE binding in individual patients' sera containing IgE antibodies to both hevein and avocado.
RESULTS: The prevalence of seropositive IgE antibodies to avocado was found to be strongly associated with the presence of hevein-specific IgE antibodies in subjects of both groups (P < .001). Sixty-seven of 91 (73%) subjects from the HCW group and all 19 subjects in the SB group with positive IgE antibodies to hevein also had elevated IgE values to avocado. Competitive RAST inhibition with 42 sera showed that IgE binding to avocado could be completely inhibited in 27 (64%) sera by preincubation with hevein. By contrast, the degrees of inhibition of IgE to hevein by avocado extract ranged from 0% to 36% (n = 16). These results indicate that sensitization to avocado in most patients allergic to latex is caused exclusively by IgE-binding epitopes present in hevein. Results of immunoblots and immunoblot inhibition with 11 serum samples confirmed that a 30-kd protein in avocado was the major IgE-binding component; the IgE-binding reactivity to this protein could be inhibited by hevein in all sera tested.
CONCLUSION: Hevein is the major cross-reacting allergen with avocado in subjects with latex allergy.
↩[30] - Karisola P, Kotovuori A, Poikonen S, Niskanen E, Kalkkinen N, Turjanmaa K, et al. Isolated hevein-like domains, but not 31-kd endochitinases, are responsible for IgE-mediated in vitro and in vivo reactions in latex-fruit syndrome. J Allergy Clin Immunol 2005;115:598-605
Imprimer la bibliographieBACKGROUND: Individuals with natural rubber latex allergy often have immediate reactions to plant-derived foods and fresh fruits, such as avocado and banana. IgE of these patients has been shown to bind endochitinases containing an N-terminal hevein-like domain (HLD). However, evidence on 31-kd endochitinase-induced reactions in vivo is lacking .
OBJECTIVE: We sought to assess the clinical significance of 31-kd endochitinases and isolated HLDs in latex-fruit syndrome .
METHODS: The 31-kd endochitinases and corresponding HLDs were purified or produced from avocado, banana, latex, and wheat germ. Skin prick test reactivities against purified proteins were examined in 15 patients with natural rubber latex allergy. The binding efficiency of IgE to purified proteins was studied by using an inhibition ELISA. Experimentally resolved or modeled structures of the proteins were compared to clarify the molecular basis of clinical reactions .
RESULTS: Eleven (73%) patients had skin prick test reactions to isolated HLDs of avocado and banana, but only 1 (7%) patient reacted to their corresponding 31-kd endochitinases. HLDs from avocado and banana inhibited binding of IgE to prohevein (Hev b 6.01) in 59% and 38% of patients, respectively, whereas corresponding percentages for 31-kd endochitinases were 17% and 20%, respectively. Isolated HLDs of wheat germ agglutinin and 18-kd wheat germ agglutinin did not significantly inhibit IgE binding to hevein .
CONCLUSION: The isolated HLD molecules alone, but not when linked to endochitinases, seem to be responsible for IgE-mediated clinical reactions in latex-fruit syndrome. Careful selection of relevant allergens in their proper molecular form is therefore crucial in forming a reliable diagnosis of latex-fruit syndrome.
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