Fescue (genus Festuca), is a large genus of grasses belonging to the family Poaceae. Festuca pratensis (F. pratensis, Meadow fescue) native to Eurasia, is a perennial grass and commonly found in temperate and cold regions of Alaska to Nova Scotia, Europe, and the United States. Meadow fescue grass is used as forage, turf, and soil stabilization. The primary allergen of Meadow fescue is a pollen grain, which is monoporate, spheroidal to ovoid, with a diameter of 31-40 mm. It is reported to induce allergic rhinitis, allergic conjunctivitis, and asthma in sensitized individuals when exposed through oral or nasal route, which was evident from various studies. Meadow fescue grass consists of the following allergen molecules Fes p 1, Fes p 4, Fes p 5, and Fes p 13, which belong to the allergen groups 1, 2/3, 4, and 5. In-vitro diagnostic tests and skin prick test is recommended for Meadow fescue allergen by the World Allergy Organization (WAO) and European standards. Meadow fescue allergen immunotherapy is administered subcutaneously at an effective maintenance dose of 1000-4000 bioequivalent allergen units (BAU). Meadow grass has extensive cross-reactivity among the family Poaceae, particularly within the subfamily Pooidea.

Risk factors

Meadow fescue pollen commonly induces allergic rhinitis (AR), allergic conjunctivitis (AC) and asthma in sensitized individuals (2). 

Worldwide distribution

Meadow fescue is native to Eurasia, introduced as a valuable forage grass in the USA and southern Canada, however, currently less planted. Meadow fescue is found from Alaska to Nova Scotia, Europe, and the United States (except Arizona and much of Florida). It is found in meadows, roadsides, and waste places (1). 

Main

Meadow fescue pollen grains are airborne and can enter the airway through the nasal or oral passage and triggers allergic reactions(2).

Allergic rhinitis

Various studies (therapeutic and/or diagnostic) have mentioned about Meadow Fescue grass sensitized or allergic patients.  A Polish study examined specific IgE in 5 grass and 3 weed pollens in 22 seasonal AR patients aged between 13 and 53 years. The study found out that Meadow fescue was the most common sensitization followed by Meadow grass, and Cocksfoot (2). Similarly, a study in Norway found that Meadow fescue is a very important causative factor for allergic symptoms in 770 seasonal and perennial nasal symptoms patients. (3). In Yugoslavia, Meadow fescue pollen grains were reported as a frequent cause of allergic reactions (4).

Other diseases

The endophyte Neotyphodium coenophialum, in Fescue grass and grains, produces several classes of plant/fungal alkaloids. These pyrrolizidine alkaloids can be found in cow’s milk, which may possess a risk to children ingesting milk. (5, 6). The fungal alkaloid may lead to toxicosis which can manifest as vascular and thermoregulatory disturbances leading to local (fescue foot)  or general hyperthermia (summer fescue toxicosis). Also, it has been reported to induce reproductive problems, agalactia (failure of milk secretion), change in lipid metabolism with fat necrosis (lipomatosis), and increased oxidative stress (6).

Allergen immunotherapy

Allergen immunotherapy (AIT) improves AR symptoms and medication use in patients with or without conjunctivitis and allergic asthma. AIT is administered as subcutaneous immunotherapy (SCIT) or sublingual immunotherapy through drops or tablets. The potential effective doses for SCIT maintenance of Meadow fescue grass is found to be 1000-4000 bioequivalent allergen units (BAU)(7). In grass-sensitive individuals, recombinant Dac g II was recognized by species- and group-cross-reactive human IgE antibodies in 33% (4/12) of sera randomly selected from grass-sensitive individuals and in 67% (14/21) of sera from patients receiving grass pollen immunotherapy (8).

Prevention strategies

Following actions, can be taken to reduce allergic reactions to pollen:

• Limit outdoor activities (if possible) during pollen season: This will reduce the amount of inhaled pollen allergen and will help in reducing allergic symptoms.
• Keep windows closed during the pollen season.
• Take allergy medicine before pollen season: this helps in preventing the release of histamine and other chemicals that can cause allergic reactions.
• Wear sunglasses and a hat to keep pollen out of the eyes and hair.
• Wash and dry clothes are worn during outdoor activities (9).

Allergenic molecules

Grass spp. among Pooideae family have a significant affinity for groups of major allergen 1, 2/3, 4, and 5 (1). Overall, 24 allergens are identified from Meadow fescue, among which 12 have an affinity for binding with IgE antibodies in sera from patients with well-established AR.

• Fes p 1.
• Fes p 4 (60 kDa protein), Group 4 grass allergen, a berberine bridge enzyme.
• Fes p 5, Group 5 grass allergen, a ribonuclease.
• Fes p 13, Group 13 grass allergen, a polygalacturonase (10)

Meadow fescue grass contains Group 1 and 4 allergens:

Group 1 allergens 

• Highly cross-reactive glycoproteins
• Highly homologous, but not all of the antigenic epitopes are crossreactive
• >95% of allergic patients possess IgE antibodies for Group 1 allergen (11).

Group 4 allergens 

•  Glycoproteins
• Molecular weight of 50 to 60 kDa

Around 75% of allergic patients possess IgE reactivity to Group 4 allergen(12)

Cross-reactivity

An extensive cross-reactivity exists among the family Poaceae, particularly within the subfamily Pooideae. Pooideae grasses lack group 2 and 5 allergens in members of the PACC clade, cross-reactivity is much less with southern grasses such as Bermuda and Bahia (1). Fescue meadow pollen cross-sensitizes with kiwi fruit. Kiwi glycoprotein (24 kilodaltons) is reported to have common epitopes and cross-reactivity with Meadow Fescue allergen (Fes p 4 and a 36 kDa) (4).

Other topics

DNA content of F. pratensis

 A study by Ebrahimzadegan R et al. (2019) concluded that repetitive sequences and transposable elements were observed in 61% of the genome, and 4% is satellite repeats which were partly harnessed as cytological markers. In the future, B-specific tandem repeats can trace the dynamics of supernumerary chromosomes which can provide direct insight into the cellular basis of the B chromosome drive mechanism in F. pratensis. (13).

Author: Turacoz Healthcare Solutions

Reviewer: Dr. Fabio Iachetti

Last reviewed: October  2020