Pla a 1
Summary
Pla a 1, a non-glycosylated protein, is a major allergen of London plane (Platanus acerifolia) tree pollen. Pla a 1 belongs to the pectine methyl esterase/invertase inhibitor family. Relevant cross-reactivity to Pla a 1 is limited to pollen homologues from other Platanaceae trees. Therefore, Pla a 1 sensitization is a marker of genuine sensitization to pollens of the Platanaceae family.
Epidemiology
Worldwide distribution
The London plane tree (Platanus acerifolia), a cosmopolitan, wind-pollinated, mainly urban and ornamental species, is a major cause of pollen sensitization in exposed populations [1, 2].
Pla a 1 was identified as a major plane tree pollen allergen, binding to IgE from up to 92% of monosensitized Platanus-allergic patients [3]. However, most patients sensitized to P. acerifolia are also sensitized to other pollens, and the molecular profile of sensitization to P. acerifolia differs according to climate conditions [1, 4]. The prevalence of Pla a 1 IgE is lower in subjects with positive skin prick tests to P. acerifolia pollen allergenic extracts but lacking a clear history of Platanus pollen allergy and/or presenting with multiple pollen elicitors, often as a result of polysensitization and panallergen involvement [4-6]. In patients with P. acerifolia pollinosis confirmed by nasal challenge with the culprit extract, Pla a 1 IgE was positive in 58.8% (10/17) [7].
Overall, studies in general population and unselected, either suspected or confirmed, allergic patients have found prevalence figures for Pla a 1 sensitization at less than 5% in different parts of Europe and Asia [8-10]. As an example, the prevalence of Pla a 1 sensitization was 1.77% and ranked 46th among 75 common allergenic molecules in a large scale study of Italian subjects with a suspicion of airborne or food allergy [11].
Monosensitization to Pla a 1 is infrequent, seen in 2-10% of Pla a 1 sensitized subjects [4, 11].
Clinical Relevance
Detailed information regarding P. acerifolia pollen is available in the whole allergen section. P. acerifolia pollinosis manifests as allergic rhinitis and asthma, which are often associated [3, 7]. Food allergy associated to plane tree pollinosis is not related to Pla a 1 sensitization, but rather to panallergens such as profilins and lipid transfer proteins [5-7].
Disease severity and prediction
Pla a 1 sensitization is associated with intermittent allergic rhinitis, rhinoconjunctivitis, and asthma with a seasonal pattern [7].
Cross-reactive molecules
London tree pollen has been implicated in cross-reactivity with various plant allergenic sources, including pollen from other trees, from grass, and weeds, and more importantly plant foods, e.g. peach [1, 7]. To date, Pla a 1-induced cross-reactivity is not considered relevant for species outside the Platanaceae family [1].
Diagnostics
Marker allergen for genuine sensitization to Platanaceae pollens
Pla a 1 is recommended as a marker of genuine sensitization to Platanaceae pollen [1]. Among 28 patients with evocative symptoms and positive skin prick tests to plane extract receiving a nasal challenge test to plane tree pollen, Pla a 1 IgE detection exhibited a sensitivity of 58.8% (10/17) and a specificity of 90.9% (10/11) [7]. Testing for Pla a 1 and Pla a 2 IgE has been suggested as a means of detecting genuine plane tree sensitization, instead of the plane pollen extract [16].
Cross-Reactivity
Pla a 1 cross-reactivity is limited to similar allergens from Platanaceae pollen [1].
AIT Prescription
Detectable Pla a 1 IgE confirms genuine sensitization to P. acerifolia, hence assisting with AIT selection [1].
Exposure
The main route of exposure is through inhalation of P. acerifolia and other Platanaceae pollen.
Prevention And Therapy
Experimental trials
Not relevant.
References
- Matricardi, P.M., et al., EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol, 2016. 27 Suppl 23: p. 1-250.
- Vrinceanu, D., et al., Urban allergy review: Allergic rhinitis and asthma with plane tree sensitization (Review). Exp Ther Med, 2021. 21(3): p. 275.
- Asturias, J.A., et al., Purification and characterization of Pla a 1, a major allergen from Platanus acerifolia pollen. Allergy, 2002. 57(3): p. 221-7.
- Nunez-Borque, E., et al., Allergen Profile of London Plane Tree Pollen: Clinical and Molecular Pattern in Central Spain. J Investig Allergol Clin Immunol, 2021: p. 0.
- Orovitg, A., et al., Enhanced diagnosis of pollen allergy using specific immunoglobulin E determination to detect major allergens and panallergens. J Investig Allergol Clin Immunol, 2011. 21(4): p. 253-9.
- Skypala, I.J., et al., Lipid Transfer Protein allergy in the United Kingdom: Characterization and comparison with a matched Italian cohort. Allergy, 2019. 74(7): p. 1340-1351.
- Wangorsch, A., et al., Molecular cloning of plane pollen allergen Pla a 3 and its utility as diagnostic marker for peach associated plane pollen allergy. Clin Exp Allergy, 2016. 46(5): p. 764-74.
- Panzner, P., et al., A comprehensive analysis of middle-European molecular sensitization profiles to pollen allergens. Int Arch Allergy Immunol, 2014. 164(1): p. 74-82.
- Garib, V., et al., Possible effect of landscape design on IgE recognition profiles of two generations revealed with micro-arrayed allergens. Allergy, 2017. 72(10): p. 1579-1582.
- Siroux, V., et al., Trajectories of IgE sensitization to allergen molecules from childhood to adulthood and respiratory health in the EGEA cohort. Allergy, 2021.
- Scala, E., et al., Cross-sectional survey on immunoglobulin E reactivity in 23,077 subjects using an allergenic molecule-based microarray detection system. Clin Exp Allergy, 2010. 40(6): p. 911-21.
- Suarez-Cervera M, A.J., Vega-Maray A, Castells T, Lopez-Iglesias C, Ibarrola I et al, The role of allergenic proteins Pla a 1 and Pla a 2 in the germination of Platanus acerifolia pollen grains. Sexual Plant Reproduction, 2005. 18: p. 101-112.
- Asturias, J.A., et al., The major Platanus acerifolia pollen allergen Pla a 1 has sequence homology to invertase inhibitors. Clin Exp Allergy, 2003. 33(7): p. 978-85.
- IUIS/WHO. IUIS/WHO Pla a 1. 2021 December 23 2022]; Available from: http://allergen.org/viewallergen.php?aid=520.
- BLAST, U. BLAST for UniProt UniProtKB - Q8GT41 (PLA1_PLAAC) for Pla a 1. December 23 2021]; Available from: https://www.uniprot.org/blast/uniprot/B202112236320BA52A5CE8FCD097CB85A53697A3502635FI.
- Asturias, J.A., et al., Purified allergens vs. complete extract in the diagnosis of plane tree pollen allergy. Clin Exp Allergy, 2006. 36(12): p. 1505-12