Ole e 7
Summary
Ole e 7 is an allergen of olive (Olea europaea) tree pollen, of intermediate prevalence, predominating in areas of high exposure. Ole e 7 belongs to the nonspecific lipid transfer protein (nsLTP) family and displays clinically relevant cross-reactivity with homologues from other allergenic sources, including Pru p 3 from peach. Ole e 7 sensitization is associated with increased prevalence of severe respiratory symptoms in olive pollinosis patients and with nsLTP panallergen sensitization and food-induced reactions with or without olive pollinosis.
Epidemiology
Worldwide distribution
Olea europaea olive trees belong to the cosmopolitan Oleaceae family and are a major cause of pollen sensitization and allergy in the Mediterranean area [1].
Ole e 7 was described as an O. europaea pollen allergen of intermediate prevalence, binding IgE from 47% of patients allergic to O. europaea [2]. Its prevalence varies according to the study population of olive tree pollinosis, with subsequent studies reporting it from 14.4% [3] to 21.5% [4], peaking at 35% [3] to 47.9%, 51.2% [5, 6] and even 60% [2] of patients with very high exposure to olive tree pollen.
At the low end, in Central Europe, the prevalence of Ole e 7 IgE is low, e.g. 0.9% in a population of pollen-sensitized patients with doctor-diagnosed allergy in the Czech Republic [7].
A significant age effect was reported for Ole e 7 sensitization, with adults affected more frequent than children (24.1% vs. 12.6% respectively) [4].
Monosensitization to Ole e 7 in patients with olive tree pollinosis is infrequent [3].
Clinical Relevance
Detailed information regarding O. europaea pollinosis, which manifests itself mainly as allergic rhinoconjunctivitis and asthma [6], is available in the whole allergen section.
Disease severity and prediction
In patients with olive tree pollinosis and respiratory symptoms, detection of Ole e 7 sensitization is associated with an increased prevalence of asthma [3] and of concomitant pollinosis to Chenopodiaceae and Poaceae [5]. However, in terms of prevalence, an inverse correlation was reported between Ole e 7 sensitization and exclusively respiratory phenotypes [4].
In patients with olive pollinosis and confirmed plant food allergy, a statistical association between Ole e 7 sensitization and an increased prevalence of fruit-induced reactions, more often severe fruit-induced reactions as opposed to mild symptoms of oral allergy syndrome (OAS), emerged soon after the identification of the Ole e 7 allergen [6]. These findings were confirmed in later cohorts, with odds ratios of 2.4 for severe reactions and 2 for OAS in Ole e 7 sensitized patients [4]. In fact, frequent concomitant sensitization to other nsLTPs (prevalence 80%) was also reported in Ole e 7 sensitized patients [4].
Conversely, in subjects outside areas of O. europaea exposure, Ole e 7 sensitization was infrequent and not associated to markers of genuine sensitization (i.e., Ole e 1), but concomitant sensitization to one or more other nsLTPs was confirmed [7].
Cross-reactive molecules
Ole e 7 shares clinically relevant cross-reactivity with other pollen and food nsLTPs such as Pru p 3 [8], and is now considered as an allergen associated to nsLTP syndrome. ELISA inhibition experiments showed that multiple food extracts induced partial inhibition of Ole e 7 IgE binding, with a maximum at 67% with peach and 52% with pear extracts [8].
Diagnostics
Marker allergen for complex sensitization profiles to O. europaea pollen
Patients with olive pollinosis living in areas with high exposure to O. europaea pollen exhibit distinct sensitization profiles, which are more complex and include frequent Ole e 7 sensitization [3].
Marker allergen for nsLTP panallergen sensitization
A statistical association between detectable sensitization to Ole e 7 and to other nsLTPs such as Pru p 3 was reported in some [7] studies but not in others [3, 11]. Studies focusing on the nsLTP syndrome and the place of Ole e 7 showed that Ole e 7 sensitization is present in nsLTP allergic patients with or without olive pollen exposure, e.g. Italy or the United Kingdom (prevalence 30% vs 17%) [12].
Cross-Reactivity
Ole e 7 displays clinically relevant cross-reactivity with other pollen and food nsLTPs [8, 10].
AIT Prescription
Sensitization to Ole e 7 has been associated to an increased prevalence of adverse reactions to AIT for olive tree pollinosis [1, 3]. Conversely, in areas of high exposure to O. europaea pollen, a sensitization profile with Ole e 7 IgE but without Ole e 1 IgE can be found, making up around 2-7% of olive pollinosis patients [5, 6] and indicating different AIT requirements [3].
Exposure
The main route of exposure is through inhalation of O. europaea pollen, usually at high levels of exposure [1]
Prevention And Therapy
Experimental trials
Not relevant.
References
- Matricardi, P.M., et al., EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol, 2016. 27 Suppl 23: p. 1-250.
- Tejera, M.L., et al., Identification, isolation, and characterization of Ole e 7, a new allergen of olive tree pollen. J Allergy Clin Immunol, 1999. 104(4 Pt 1): p. 797-802.
- Barber, D., et al., Understanding patient sensitization profiles in complex pollen areas: a molecular epidemiological study. Allergy, 2008. 63(11): p. 1550-8.
- Scala, E., et al., Ole e 1, Ole e 7, and Ole e 9: Identifying distinct clinical subsets of olive tree-allergic patients. J Allergy Clin Immunol, 2016. 137(2): p. 629-631 e3.
- Quiralte, J., et al., Olive allergen-specific IgE responses in patients with Olea europaea pollinosis. Allergy, 2002. 57 Suppl 71: p. 47-52.
- Quiralte, J., et al., Modelling diseases: the allergens of Olea europaea pollen. J Investig Allergol Clin Immunol, 2007. 17 Suppl 1: p. 24-30.
- Panzner, P., et al., A comprehensive analysis of middle-European molecular sensitization profiles to pollen allergens. Int Arch Allergy Immunol, 2014. 164(1): p. 74-82.
- Oeo-Santos, C., et al., New insights into the sensitization to nonspecific lipid transfer proteins from pollen and food: New role of allergen Ole e 7. Allergy, 2020. 75(4): p. 798-807.
- IUIS/WHO. IUIS/WHO Olea europaea allergens. 2021 2021 December 30]; Available from: http://allergen.org/search.php?allergenname=&allergensource=Olea+europaea&TaxSource=&TaxOrder=&foodallerg=all&bioname=.
- Gonzalez-Klein, Z., et al., The key to the allergenicity of lipid transfer protein (LTP) ligands: A structural characterization. Biochim Biophys Acta Mol Cell Biol Lipids, 2021. 1866(7): p. 158928.
- Scala, E., et al., Lipid transfer protein sensitization: reactivity profiles and clinical risk assessment in an Italian cohort. Allergy, 2015. 70(8): p. 933-43.
- Skypala, I.J., et al., Lipid Transfer Protein allergy in the United Kingdom: Characterization and comparison with a matched Italian cohort. Allergy, 2019. 74(7): p. 1340-1351.