g14 Cultivated oat

Anecdotal evidence suggests that cultivated oat pollen may induce asthma, allergic rhinitis and allergic conjunctivitis in sensitized individuals, however few studies have been reported to date. Nine allergens have been characterized from Avena sativa, representing a number of allergen Groups, and extensive cross-reactivity may be expected to a certain degree among other members of the family Poaceae, especially in the subfamily Pooideae.

Worldwide distribution 

Oat is a nutritionally important crop throughout the world and is ranked sixth in world cereal crop production, with secondary uses in cosmetics and other industries (3). Oats are cultivated in cool temperate zones with reasonably high rainfall, long day length and moderate temperatures, such as the USA, southern Canada, the Russian Federation, mid to North Europe, and Australia and South America (4, 5). A. sativa is an annual grass that can grow to 1.5 m tall and commonly yields approximately 30,000 seeds per kilogram of harvested plant (6). The majority of production comes from spring sown cultivars (for early autumn harvest), however autumn sowing may be practiced in regions where summers are hot and dry.(7). 

Anecdotal evidence suggests that cultivated oat pollen may induce asthma, allergic rhinitis and allergic conjunctivitis in sensitized individuals, however few studies have been reported to date (2, 8, 9).

In a clinical file review of 335 female and 130 male asthmatic patients attending a hospital clinic in Cova de Beira (Portugal), 70% of the patients had allergic asthma and 30% had non-allergic asthma (2). Skin-prick testing (SPT) identified the major sensitizers for allergic asthmatic individuals to be grass pollen (65.5%), mites (62.9%), cereal pollens including A. sativa (62.6%), tree pollen (49.3%), weed pollen (49.3%), dog dander (30%), molds and fungi (21.9%) and cat dander (15.3%) (2). The study noted no correlation between the wheal size of the prick tests or the pattern of allergen sensitization and the severity of allergic disease (2). In contrast to these results in adults, an earlier study in the same region of Portugal submitted 371 pediatric patients (aged ≤15 years) to SPTs to aeroallergens and noted a prevalence of only 0.1% sensitization to A. sativa extract (8).

Specific IgE determination demonstrated that oat pollen may be an occupational allergen among dairy farmers (9).

The serum immunoreactivity profiles to common indigenous allergens in Iran were recently compared between 39 patients with Meniere’s disease and 41 control individuals (10). This study reported a significant relationship between Meniere and serum reactivity to inhalation and food allergens (both, p=0.001), and also a significant difference between the Meniere and control groups with respect to individual inhalation allergens including sweet vernal grass, cultivated rye, cultivated oat, Russian thistle, goosefoot and rough pigweed (p=0.01–0.038) (10). 

Allergenic molecules

The following allergens have been characterized from A. sativa: (11)

·       Ave s 1, a Group 1 grass allergen, an expansin

·       Ave s 2, a Group 2 grass allergen with unknown biological function

·       Ave s 36, a glutenin

·       Ave s 4, a Group 4 grass allergen, a berberine bridge enzyme

·       Ave s 5, a Group 5 grass allergen, a ribonuclease

·       Ave s 7, a calcium-binding protein, polcalcin

·       Ave s 11S, a legumin-like protein (11S Globulin)

·       Ave s 12, a profilin

·       Ave s 13, a Group 13 grass allergen, a polygalacturonase

Biomarkers of severity

Group 13 allergens specifically occur in pollen of the major grass subfamilies, and Group 13-specific IgE antibodies can be considered immunological markers for genuine grass pollen sensitization (12).

Cross-reactivity

More than 95% of patients allergic to grass pollens have IgE antibodies to Group 1 allergens, while 60% have IgE antibodies to Group 2/3 allergens, 70% to Group 4 allergens, 70-80% to Group 5 allergens, and 20% to profilins (13).

Extensive cross-reactivity among the different individual species of the genus Avena may be expected, and to a certain degree among members of the family Poaceae, especially in the subfamily Pooideae, as a result of the variable degree of cross-reactivity between allergens in Groups 1, 2, 4, and 5 (13-16).

A survey of 193 grass pollen-allergic patients from different countries noted that inhibition of IgE binding to pollen extracts prepared from species more closely related to timothy grass was higher (e.g. Anthoxanthum odoratum [sweet vernal grass]: 65%, A. sativa: 66%, Lolium perenne [rye grass]: 64%, Poa pratensis [meadow grass/Kentucky Bluegrass]: 66%, Secale cereale [cultivated rye]: 63%, and Triticum sativum [cultivated wheat]: 63%) than to extracts from more distantly-related species (Cynodon dactylon [Bermuda grass]: 47%, Phragmites australis [Australian reed]: 55%, and Zea mays [maize/corn]: 45%) (13). In this study, immunologically detectable Group 5 and Group 2 allergens were found in all species except for C. dactylon and Z. mays (13).

In a survey of proteins cross-reactive with Group 1, Group 4 and Group 9 allergens, numerous allergen cognate proteins were identified in pollen from ten agricultural species including barley (Hordeum vulgare), maize/corn (Z. mays), rye (S. cereale), triticale (xTriticosecale cereale), oat (A. sativa), canola (Brassica napus) and sunflower (Helianthus annus) (17). 

Author: RubyDuke Communications

Reviewer: Dr. Christian  Fischer

Last reviewed: December  2021