g16 Meadow foxtail

Alopecurus pratensis is a tall perennial grass species with a broad native range, and one of the most important sources of airborne pollen in temperate regions. Meadow foxtail contributes to seasonal and perennial rhinitis symptoms of grass pollen allergic individuals, however there is some evidence that continuous exposure to cowshed dust containing A. pratensis pollen may elicit some degree of immuno-modulation which protects children against allergy.

Worldwide distribution 

A. pratensis is a tall perennial grass species with a broad native range across temperate Europe and Asia (3) (1). Widely grown for hay and pasture in North America, South America and Australia, meadow foxtail is considered to be an invasive species in parts of Australia, Alaska, Denmark, Faroe Islands, Iceland, Norway and Sweden (1) (4). 

Main 

A. pratensis is one of the first grasses to begin growth in the spring (3, 5) and one of the most important sources of airborne grass pollen in temperate regions (6).

Anecdotal evidence suggests that pollen produced by A. pratensis may induce hay fever, asthma and conjunctivitis in sensitized individuals(2){Holopainen, 1979 #7;Kmenta, 2017 #9}; however, very few studies specifically assessing the role of A. pratensis have been reported to date.

A high degree of skin reactivity has been observed in patients with hay fever exposed to unfractionated extracts of grass pollens, including meadow foxtail (2). In 1979, an assessment of 770 patients in Nordic countries with seasonal and perennial nasal symptoms determined that Alopecurus was an important contributor to positive reactions to pollen (7).

More recently, A. pratensis was identified as a potentially relevant allergen in a population study of pollen allergy in the Sarajevo region (Bosnia and Herzegovina) during 2002 (8). In 2015, A. pratensis was also shown to be a significant contributor to aerial pollen concentration and rhinitis symptoms of grass pollen allergy sufferers in Berlin (Germany) during the grass pollen season (9).

However, mice treated with intranasal applications of cowshed dust containing plant material from hay and grass fodder (primarily A. pratensis) had significantly lower IgE antibodies than mice treated with sham intranasal formulations (10). These authors were the first to demonstrate that arabinogalactan from A. pratensis induced IL-10 production and protected the mice from developing atopic sensitization, allergic airway inflammation and airway hyperreactivity (10). Arabinogalactan is a major component of grass pollen (10), and the concentration of grass pollen in the air of cowsheds has been correlated with allergy protection in children who live on farms (11).

Allergenic molecules

Meadow foxtail grass contains at least 24 antigens, of which 12 have been shown to bind to sera from patients with well-established allergic rhinitis (12).

The following allergens have been characterized from A. pratensis:

·       Alo p 1, a 27-32 kDa protein, a Group 1 grass allergen (13)

·       Alo p 5, a 27-33 kDa protein, a Group 5 grass allergen (13)

The Group 1 and Group 5 allergens are considered to be major allergens as 90% and 65% of individuals allergic to grass pollen posses IgE reactivity to these allergens, respectively (14).

Cross-reactivity

Variable degrees of cross-reactivity may occur between grass pollen species sharing Group 1 and/or Group 5 grass allergens (13). An in vitro analysis of 13 grasses demonstrated a high degree of structural homology and extensive epitope sharing between meadow foxtail, Timothy grass (g6), wild rye (g70), cultivated rye (g5), fescue meadow grass (g4), meadow grass (g8), orchard grass (g3), velvet grass (g13), redtop grass (g9), crested dogstail grass, brome grass, false oat grass and sweet vernal grass (14).

Carbohydrate-reactive IgE antibodies attributed to grass pollen sensitization have been found to cross-react with glycan structures from other allergen sources, particularly vegetable foods (15). Extensive cross-reactivity is also possible between profilins, a family of Group 12 allergen proteins which are highly conserved throughout the plant kingdom and present in all tissues (15).

Author: RubyDuke Communications

Reviewer: Dr. Christian  Fischer

Last reviewed: December  2021