Purification of the glycoprotein allergen Ag7 from mugwort pollen by concanavalin A affinity chromatography

Two affinity columns comprising immobilized concanavalin A (Con A), Con A-Sepharose and Con A-XP3507, were evaluated for their purifying ability for the glycoprotein allergen Ag7 from a partially purified extract of mugwort pollen. The most pronounced difference between the two columns was the nature of their nonspecific interactions; hydrophobic interactions were dominant with Con A-XP3507, whereas ionic interactions were dominant with Con A-Sepharose. Both Con A-columns were effective for purifying Ag7 with a recovery of 50% after specific elution with displacing sugars. The inclusion of 1.0 M NaCl and 20% ethylene glycol in the elution medium was useful for desorbing nonspecifically bound material, prior to specific elution of adsorbed Ag7 in the presence of the displacing sugars, α-methyl glucoside and α-methyl mannoside. The most efficient purification of Ag7 was achieved with Con A-Sepharose at room temperature rather than at 4°C. Affinity chromatography with Con A-XP3507 resulted in a slightly more contaminated product (purity 54%) than with Con A-Sepharose (purity 64%).