rOle e 1 Olive

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Olive t9

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Code: t224
Latin name: Olea europaea
Source material: rOle e 1 is a CCD-free recombinant protein
Family: Oleaceae
Common names: Group 1 Oleaceae

Olive allergen components

Available ImmunoCAP®:  

Olea europaea, the Olive tree, is one of the most important causes of seasonal respiratory allergy in the Mediterranean area (1) and also in other parts of the world where this tree is now grown. Olive tree is a member of the Oleaceae family, which has 4 important genera: Olive (Olea), Ash (Fraxinus), Lilac (Syringa), and Privet (Ligustrum).

Olive tree probably originated in Asia Minor, spread to the Mediterranean region, and was then introduced into North America (especially California and Arizona), South America (Chile), Australia and South Africa. Although in North America Olive trees are found only in the Southwest, Ash and Privet are widespread, a circumstance of relevance to cross-reactivity (2). Countries and regions have distinct varieties of Olive. In Italy, individual varieties of Olea europaea, which differ between the northern and southern parts of the country, may induce different IgE-mediated reactions (3).

The Olive tree is an evergreen growing to 10 m, with a broad, round crown and a thick and knotty trunk. The flowers are hermaphrodite (have both male and female organs). The plant is self-fertilising. Pollination is by insects but also by wind when pollen is in abundance. The pollination period varies: it typically occurs in the spring, but in Europe may start as early as January, depending on the region (1). In southern Italy it lasts from early April to late June, and as one moves north, lasts until July (3).

Olive pollens can induce asthma, allergic rhinitis and allergic conjunctivitis in sensitised individuals (4-11).

The frequency of sensitisation to Olive tree pollen varies in the Mediterranean region from ~10% of atopic individuals in Sicily to ~40% in Greece (1,12). In Greece, one study found that more than 37% of atopic individuals were sensitised to Oleaceae (13). Fifteen percent of atopic patients in southern France were found to be skin-prick positive to Oleaceae (14). In Italy, atopic sensitisation varied from 12% in Sicily to 30% in Apulia (15-19). In Naples, of 4,142 patients examined consecutively over a two-year period, 13.5% of adults and 8.5% of children of all skin prick test-positive patients were positive to Olea pollen allergens on skin-prick testing (20). Less than 1.4% of children and 2.3% of adults were found to be monosensitised to Olive pollen (20). In another study on 507 asthmatic atopic children in the Chieti-Pescara area of Italy, skin-prick tests found that 21% were sensitised to Olive tree pollen (21).

Sensitisation to Olive pollen has also been reported in Israel (22-23). Positive skin reactions to Olive pollen, among atopic patients of the Jewish population, was shown to be high where Olive trees are abundant (66%), and lower (29%) where the trees are scarce (24-25). In Spain, a study demonstrated that the frequency of sensitisation could vary greatly within the same country (26-27). The daily pollen concentration in the atmosphere showed pollen from the Olive tree to be one of the most common pollen grains (28).

Olive tree pollen has also been shown to result in sensitisation in Japan as well as in Israel; in the Japan 16% of pollinosis patients were positive to this allergen (25,29). Skin-prick tests for sensitisation to Olive tree pollen in the southern part of Switzerland (Canton Ticino) showed a high sensitisation rate of 54% (30).

The majority of studies demonstrate a higher prevalence of rhinoconjunctivitis than of asthma (1). Patients are more likely to be polysensitised than monosensitised to Olive tree pollen. Polysensitised individuals, children and adults, may have symptoms throughout the year without an apparent increase during the Olive pollination season (11,31).

The following allergens have been characterised. 

  • Ole e 1 (32-36). 
  • Ole e 2, a profilin (37). 
  • Ole e 3, a calcium-binding protein (38). 
  • Ole e 4 (39-40). 
  • Ole e 5, a superoxide dismutase (39-40). 
  • Ole e 6 (41). 
  • Ole e 7, a lipid-transfer protein (42). 
  • Ole e 8, a calcium-binding protein (41). 
  • Ole e 9, a 1,3-beta-glucanase protein (43). 
  • Ole e 10 (44).
Allergens from Olea europaea listed by IUIS*
Ole e 1 Ole e 2

  *International Union of Immunological Societies ( Jan. 2008

t224 rOle e 1

Recombinant non-glycosylated protein produced in an E. coli strain strain carrying a cloned cDNA encoding Olea europaea allergen Ole e 1

Common name: Common olive group 5, Group 1 Oleaceae
Biological function: Trypsin inhibitor
Mw: 19 and 20 kDa

Allergen description

Ole e 1 (45) exhibits a high degree of polymorphism (46) and is present in Olive tree pollen in 2 main forms, glycosylated and nonglycosylated, with apparent molecular masses of 20 and 18.5 kDa, respectively (47). rOle e 1 is actually a mixture of polypeptides with different glycosylation patterns (46).

Of the many allergens isolated and characterised from Olive pollen, Ole e 1 is the most frequent sensitising agent, affecting more than 70% of patients with sensitisation to Olive pollen, although other allergens, such as Ole e 4 and Ole e 7, have also been shown to be major allergens. The prevalence of many Olive pollen allergens is dependent on geographical location (41).

Not all allergens are found in every Olive tree cultivar. In a study examining the various IgE-binding proteins of the pollen extracts of the various Olive tree cultivars, 6 predominant IgE-binding bands, some of which appear in all the cultivars, were found. Ole e 1 appeared in only 8 of the cultivars, but not in the 9 others (48).

Current standard diagnostic methods utilise crude pollen extracts that contain a complex mixture of allergenic and non-allergenic proteins. Furthermore, Ole e 1 concentration has been shown to have a 25-fold variation in pollen extracts (49). Therefore, using a well-defined allergen such as rOle e 1 allows for improved diagnosis and therapy.

A high degree of cross-reactivity has been demonstrated among Olive tree (Olea europaea), Ash (Fraxinus exselsior), Privet (Ligustrum vulgare) and Phillyrea angustifolia (a bush usually confined to certain areas of the Mediterranean) (2). All are members of the Oleaceae family, although there is no total identity among these 4 pollen species (50). The major pollen allergens from Ash (Fra e1) Privet (Lig v 1) and Lilac or Syringa vulgaris (Syr v 1), another member of the Oleaceae family, are proteins homologous to Ole e 1 (4,36,51-54). Ole e 1 has been reported to be a marker allergen for the diagnosis of Olive and European ash pollen allergy (55).

Therefore, rOle e 1 may be of diagnostic benefit in particular in areas where no Olive trees exist but other Ole e 1-cross-reactive pollens are found. For example, in northern and central Europe, where there are no Olive trees, 2 commonly occurring genera of the Oleaceae family, Fraxinus and Ligustrum, are present; but these have a low frequency of allergic sensitisation compared to Olea. The importance of cross-reactivity is demonstrated by a study in Michigan, USA, where in 103 atopic subjects, cross-reactivity among Olive tree, Fraxinus, Privet and Russian olive tree pollens was demonstrated, even though the Olive tree does not grow in that area. Nineteen subjects were skin prick-positive to this allergen, confirming the effect of cross-reactivity (2).

Cross-reactivity between extracts of Oleaceae and some species of the Poaceae family has also been shown (56-57). The major allergen of Plantago lanceolata (English plantain) pollen, Pla l 1, has been shown to have significant sequence homology with the major Olive pollen allergen Ole e 1 (58).

Compiled by Dr Harris Steinman,


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As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.