rPla a 1, London plane tree/ Maple leaf sycamore

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Code: t241
Latin name: Platanus acerifolia
Source material: rPla a 1 is a CCD-free recombinant protein.
Family: Platanaceae
Common names: Invertase inhibitor

Allergen: rPla a 1. (1, 2, 3)
                rPla a 1 is a CCD-free recombinant protein.

Biological function: Invertase inhibitor.

Mw: 18 kDa

Clinical Utility

Pla a 1, an invertase inhibitor, is a major allergen, recognised by up to 90% of plane-tree-allergic patients. (1)

Recombinant Pla a 1, like other recombinant allergens, can be used to assess patient reactivity, characterise IgE binding epitopes, and study the effect of mutations on IgE binding.

The sensitivity of a mix of Pla a 1 and Pla a 2 was demonstrated to be100% and 87.5% for monosensitised and polysensitised patients, respectively, with no false-positive reactions detected. Researchers have proposed that a combination of Pla a 1 and Pla a 2 can be reliably used to diagnose plane pollen allergy, instead of the whole pollen extract. (3)

Allergen Exposure

See Maple leaf sycamore/London plane t11.

Allergen description:

Pla a 1 is an invertase inhibitor. (1, 2, 3 4, 5, 6, 7)

Invertases convert the transport sugar sucrose into its building blocks, fructose and glucose. Invertase activity is vital for cellular processes such as carbohydrate transport, sugar signalling, and stress response. Protein inhibitors of invertase affect enzyme activity in a strictly pH-dependent manner. (8)

Invertase inhibitors are thermolabile proteins with molecular weights of 18 kDa to 23 kDa. (9)

Invertase inhibitors have been characterised in American Sycamore (Pla oc 1) Oriental plane tree (Pla or 1) and California Sycamore (Pla r 1). (10)

Invertase inhibitors of unknown allergenic potential have been isolated from a number of plants and vegetables, including red beets, sugar beets, and sweet potatoes. (9)

Potential Cross-Reactivity

Invertase inhibitors have been isolated and characterised in American Sycamore (Pla oc 1), Oriental plane tree (Pla or 1), and California Sycamore (Pla r 1). (10) However, the cross-reactivity of the invertase inhibitors found in these closely related species can be inferred, but has not been evaluated.

Pla a 1 share 43%, 40%, 28%, and 27% identical residues with invertase inhibitors from grape, Arabidopsis thaliana, tobacco, and tomato, respectively. (2) The allergenic potential of these invertase inhibitors has not been evaluated. Potential clinically relevant cross-reactivity between the Pla a 1 and other invertase inhibitors has not been determined.

A study conducted in Spain that analysed the differences between pollen-allergic patients with and without plant food allergy evaluated 806 patients utilising a panel of 28 purified allergens from pollens and/or plant foods. The authors remarked that Pla a 1 and Pla a 2 are major allergens of P. acerifolia, which some reports had cited as being involved in plant food allergy; but noted that although P. acerifolia pollens have frequently been associated with plant food allergy (peach, nuts and others), due to Pla a 3 – a lipid transfer protein (LTP) with partial cross-reactivity to Peach Pru p 3 – their data supported the notion that Pla a 1 and Pla a 2 were potentially involved in these cross-reactivity reactions. (11) To date this impression has not been further assessed.

Clinical Experience

Plane trees are an important source of airborne allergens in many cities of the United States and western Europe, (2) and exposure to London plane tree pollen can induce asthma, allergic rhinitis and allergic conjunctivitis; (12, 13, 14) systemic reactions have occurred during immunotherapy. (15)

Initially, the relevance of London plane tree pollen as a cause of seasonal allergy was thought to be negligible, and thought not to contribute much to the prevalence of atopic sensitisation, even though the pollen had been detected in the atmosphere, as some relevant position papers and review articles of the main pollen sources in Europe do not mention plane pollen at all; (16, 17) but recent studies have argued that pollen from this tree is an important cause of pollinosis.

Although early studies reported that Pla a 1 was recognised by up to 92% of monosensitised Platanus-allergic patients and 83% of polysensitised patients, (1, 2) a more recent study suggests that the prevalence may depend on a geographic region and/or population group: a Spanish study of 179 pollen-sensitised patients who underwent skin-prick test with pollen extract and allergen-specific IgE for a range of allergens reported that of 67 patients found to be sensitised to P. acerifolia by skin-prick test, only 16 (8.9%) were found to have specific IgE to Pla a 1. (18)

An Italian study demonstrated monosensitisation to plane pollen. The patient, a 40-year-old man experiencing rhino-conjunctivitis from mid-April to the end of May over a period of 7 years, was shown to be monosensitised to plane pollen. On ISAC 103 the patient showed IgE reactivity to both Pla a 1 and Pla a 2, but on immunoblot analysis the serum showed a single IgE reactivity at about 50 kDa allergen. The authors suggested that although such a condition is a very rare event in that geographic area, it may be worth testing patients routinely with plane pollen extract. (19)

See Maple leaf sycamore/London plane t11 for clinical information and further details on London plane allergy.

Compiled by Dr Harris Steinman, harris@allergyadvisor.com


  1. Asturias JA, Ibarrola I, Bartolomé B, Ojeda I, Malet A, Martínez A. Purification and characterization of Pla a 1, a major allergen from Platanus acerifolia pollen. Allergy 2002;57(3):221-7.
  2. Asturias JA, Ibarrola I, Eraso E, Arilla MC, Martínez A. The major Platanus acerifolia pollen allergen Pla a 1 has sequence homology to invertase inhibitors. Clin Exp Allergy 2003;33(7):978-85.
  3. Asturias JA, Ibarrola I, Amat P, Tella R, Malet A, Cisteró-Bahíma A, Enrique E, Malek T, Martínez A. Purified allergens vs. complete extract in the diagnosis of plane tree pollen allergy. Clin Exp Allergy 2006;36(12):1505-12.
  4. International Union of Immunological Societies Allergen Nomenclature: IUIS official list http://www.allergen.org/ Accessed December 2013.
  5. Fernández-González D, González-Parrado Z, Vega-Maray AM, Valencia-Barrera RM, Camazón-Izquierdo B, De Nuntiis P, Mandrioli P. Platanus pollen allergen, Pla a 1: quantification in the atmosphere and influence on a sensitizing population. Clin Exp Allergy 2010;40(11):1701-8.
  6. Fernández-González M, Guedes A, Abreu I, Rodríguez-Rajo FJ. Pla a_1 aeroallergen immunodetection related to the airborne Platanus pollen content. Sci Total Environ 2013;463-4:855-60.
  7. Enrique E, Alonso R, Bartolomé B, San Miguel-Moncín M, Bartra J, Fernández-Parra B, Tella R, Asturias JA, Ibarrola I, Martínez A, Cisteró-Bahíma A. IgE reactivity to profilin in Platanus acerifolia pollen-sensitized subjects with plant-derived food allergy. J Investig Allergol Clin Immunol 2004;14(4):335-42.
  8. Hothorn M, Wolf S, Aloy P, Greiner S, Scheffzek K. Structural insights into the target specificity of plant invertase and pectin methylesterase inhibitory proteins. Plant Cell 2004;16(12):3437-47.
  9. Pressey R. Invertase inhibitors from red beet, sugar beet, and sweet potato roots. Plant Physiol 1968;43(9):1430-4.
  10. Arilla MC, Ibarrola I, Mir A, Monteseirín J, Conde J, Martínez A, Asturias JA. Development of a sandwich-type ELISA for measuring Pla a 1, the major allergen of Platanus acerifolia pollen. Int Arch Allergy Immunol 2005;138(2):127-33.
  11. Cuesta-Herranz J, Barber D, Blanco C, Cistero-Bahíma A, Crespo JF, Fernández-Rivas M, Fernández-Sánchez J, Florido JF, Ibáñez MD, Rodríguez R, Salcedo G, Garcia BE, Lombardero M, Quiralte J, Rodriguez J, Sánchez-Monge R, Vereda A, Villalba M, et al. Differences among pollen-allergic patients with and without plant food allergy. Int Arch Allergy Immunol 2010;153(2):182-92.
  12. Bousquet J, Hejjaoui A, Becker WM, Cour P, Chanal I, Lebel B, Dhivert H, Michel FB. Clinical and immunologic reactivity of patients allergic to grass pollens and to multiple pollen species. I. Clinical and immunologic characteristics. J Allergy Clin Immunol 1991;87(3):737-46.
  13. Carretero Aníbarro P, Juste Picón S, García González F, Alloza Gómez P, Pérez Giménez R, Blanco Carmona J, Reinares Ten C, Vicente Serrano J, Bascones O. Allergenic pollens and pollinosis in the city of Burgos. [Spanish] Alergol Inmunol Clin 2005;20(3):90-4.
  14. Belver MT, Caballero MT, Contreras J, Cabañas R, Sierra E, Madero R, López Serrano MC. Associations among pollen sensitizations from different botanical species in patients living in the northern area of Madrid. J Investig Allergol Clin Immunol 2007;17(3):157-9.
  15. Hejjaoui A, Ferrando R, Dhivert H, Michel FB, Bousquet J. Systemic reactions occurring during immunotherapy with standardized pollen extracts. J Allergy Clin Immunol 1992;89(5):925-33.
  16. D'Amato G, Spieksma FT, Liccardi G, Jäger S, Russo M, Kontou-Fili K, Nikkels H, Wüthrich B, Bonini S. Pollen-related allergy in Europe. Allergy 1998:53:567-78.
  17. D'Amato G, Cecchi L, Bonini S, Nunes C, Annesi-Maesano I, Behrendt H, Liccardi G, Popov T, van Cauwenberge P. Allergenic pollen and pollen allergy in Europe. Allergy 2007;62(9):976-90.
  18. Orovitg A, Guardia P, Barber D, de la Torre F, Rodríguez R, Villalba M, Salcedo G, Monteseirìn J, Conde J. Enhanced diagnosis of pollen allergy using specific immunoglobulin E determination to detect major allergens and panallergens. J Investig Allergol Clin Immunol 2011;21(4):253-9.
  19. Asero R, Mistrello G, Amato S, Villalta D. Monosensitization to a novel plane pollen allergen. Eur Ann Allergy Clin Immunol 2012;44(4):167-9.


As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.