Type:
Component
Component
Component
Phl p 7
Unknown
g210
Recombinant, CCD-free protein
Timothy grass pollen polcalcin
Phl p 7 is a minor allergen from timothy grass (Phleum pratense) pollen belonging to the polcalcin family of pollen panallergens. It is a non-glycosylated, calcium-binding EF-hand protein.
Grass pollens are the principal causes of respiratory allergic disease globally. Timothy grass has a widespread distribution in the temperate climate and is often the predominant grass pollen in such European and Asian regions, less so in Australia (1, 2). Timothy grass pollen induces allergic rhinitis (AR), allergic rhinoconjunctivitis (ARC), and exacerbates asthma in sensitized individuals (2)
Phl p 7 is a minor allergen of timothy grass pollen, binding IgE from 7-10% of grass-allergic patients, often less in pediatric patients (1, 3-5). In an unselected population of 23,077 consecutive Italian subjects with a suspicion of airborne or food allergy, the prevalence of IgE sensitization to Phl p 7 was 2.47% (6).
The Swedish birth cohort BAMSE provided data in pediatric general population. Sensitization to Phl p 7 was detected in none of 763 pediatric subjects at the age of 4 years, in 0.3% at age 8, and in 1.2% at age 16 (7).
Apparent monosensitization to Phl p 7 is infrequent (7) .
Detailed information regarding timothy grass pollen is available in the whole allergen section. Timothy grass pollen induces allergic rhinitis (AR), allergic rhinoconjunctivitis, and exacerbates asthma in sensitized individuals (2). There is a high degree of cross-reactivity between timothy grass and other grass pollens (3).
Sensitization to Phl p 7 is usually detected in grass allergic patients years after the onset of symptoms (1, 9). Sensitization to Phl p 7 is almost constantly associated with sensitization to major grass pollen allergens, and a distinct source of primary sensitization should be considered if sensitization to Phl p 1 and Phl p 5 is lacking (1).
Grass-allergic patients sensitized to Phl p 7 display a more severe phenotype in terms of symptom severity, asthma prevalence and allergic comorbidities (1). Sensitization to Phl p 7 was also identified as a biomarker of asthma and more severe AR in a pediatric cohort of grass allergic patients (10).
In the birth cohort BAMSE, Phl p 7 sensitization at age 8 in subjects without grass allergy symptoms was associated with the development of grass pollen AR by the age of 16 (7). However, due to the very rare occurrence of Phl p 7 sensitization at age 8, this result did not reach statistical significance.
Clinically significant cross-reactivity of Phl p 7 is observed with other polcalcins from unrelated plant species (1, 8)
Phl p 7 induces skin reactivity, in vitro histamine degranulation, and was identified as a potent allergen (1, 3, 4)
Phl p 7 is an acidic EF-hand, calcium-binding homodimeric protein with a molecular weight of 6 kDa.
As of August 15th, 2021, one isoallergen of Phl p 7 i.e., Phl p 7.0101, has been officially published by the World Health Organization (WHO) and International Union of Immunological Societies (IUIS) Allergen Nomenclature (11)
Phl p 7 displays extensive sequence identity and conformational similarity to other polcalcins (3, 4, 8)
Upon exposure of predisposed individuals to grass pollen, sensitization to Phl p 7 is a late event, although infrequent (1, 7-9).
Sensitization to Phl p 7 is a marker of more severe AR, higher risk of asthma and higher risk of other allergic comorbidities (1, 10).
Phl p 7 cross-reacts with similar proteins from other pollens, making it a suitable biomarker of sensitization to the panallergen family of polcalcins
Phl p 7 is not a candidate molecule for AIT (5, 11)
The main route of exposure is through inhalation of timothy grass pollen (1, 3).
Author: Joana Vitte
Reviewer: Dr. Christian Fischer
Last reviewed: November 2021