Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen- and plant food-allergic patients. Most of the melon-allergic patients (more than 70 percent) presented specific IgEantibodies to 14.4 Kda protein in melon extract that could be attributed to profilin.

To characterize allergenic component of the melon at the molecular level, this study was aimed at the cloning of melon major allergen cDNA. The IgE-binding component was isolated from melon by cation exchange FPLC and a purification step on poly-L-proline 4BSepharose. Cloning of melon profilin was performed by reverse transcription-PCR using degenerated primers. 5' and 3' RACE methods were carried out for the identification of the unknown 5'-end and 3'-end of the cDNA.

Four isoforms of profilin identified that significant differences were noted in the non-coding regions, whereas coding sequence in one of them only showed a variation in position 54. Coding sequences of all isoforms (AY292385, AY292386, AY292385) had a length of 394 bp corresponding to 131 amino acid residues and a predicted isoelectric point of 4.46. The deduced amino acid sequence of the corresponding protein showed high identity with other plant profilins (71-84%) recently described as allergens.

Profilin is an important allergenic compound in melon and shows high homology to pollens profilin. Pollenosis and associated allergies to melon can therefore partly be explained by the cross-reactivity between homologous profilins.