Pho d 2, a major allergen from date palm pollen, is a profilin: cloning, sequencing, and immunoglobulin E cross-reactivity with other profilins.
BACKGROUND
Up to now, some date palm pollen (DPP) allergens have been described but very few data are available about their molecular nature. The aim of this study was to identify and characterize Pho d 2, a major allergen from this pollen.


METHODS
Sera from 25 patients allergic to DPP were analysed by immunoblotting. Purification of DPP profilin was performed by poly-l-proline affinity chromatography. Profilin-encoding cDNA from DPP was cloned by using a RT-PCR strategy and recombinant allergen was expressed as a non-fusion protein in Escherichia coli. Natural and recombinant Pho d 2 were investigated by means of enzyme allergosorbent test to compare the immunologic properties of both allergens and to analyse cross-reactivity with other profilins.


RESULTS
A 14.4 kDa protein was identified as a major allergen in DPP extract. Purification, cloning, heterologous expression, and inhibition experiments identified it as profilin (Pho d 2). Pho d 2 comprises 131 amino acids and has high sequence identity with other allergenic food and pollen profilins. The prevalence of specific IgE antibody reactivity to natural Pho d 2 by ELISA was 56% and 64% by skin prick test (SPT). Pho d 2 is an important allergen as it is responsible for more than 70% of the IgE reactivity to the pollen extract. IgE directed against Pho d 2 showed a strong cross-reactivity with other profilins such as those from olive tree and grass pollens.


CONCLUSIONS
Pho d 2, a 14.4 kDa protein identified as profilin, is a major and relevant allergen in DPP, as confirmed by SPT and thereby may elicit clinical symptoms in sensitized patients.
Asturias
J A
JA
Department of Research and Development, Bial-Arístegui, E-48008 Bilbao, Spain. juan.asturias@bial.com
Ibarrola
I
I
Fernández
J
J
Arilla
M C
MC
González-Rioja
R
R
Martínez
A
A
D000328:Adult; D000368:Aged; D000485:Allergens / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000097:blood; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011058:Pollen / Q000276:immunology*; D011994:Recombinant Proteins / Q000302:isolation & purification; D012882:Skin Tests
D000485:Allergens; C503226:Pho d 2 protein, date palm; D011994:Recombinant Proteins; D007073:Immunoglobulin E