Identification and characterization of the allergenic proteins of Bahia grass (Paspalum notatum) pollen

BACKGROUND: Pollen of Bahia grass (Paspalum notatum) represents a major cause of type I allergy in diverse geographical areas, particularly in the southeastern coastal plain area of the United States. The aqueous protein extract of Bahia grass pollen contains the allergenically active components that produce skin-test-positive reactions in sensitive patients. OBJECTIVE: The emphasis of this study included the identification and characterization of the allergenic proteins present in the crude protein aqueous extract of Bahia grass pollen. METHODS: The crude extract of Bahia grass pollen, partially purified by isoelectric focusing and fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was electroblotted onto nitrocellulose membranes, probed with sera from patients skin test positive to Bahia grass and detected using anti-human IgE conjugated peroxidase. RESULTS: Four allergenic proteins of Bahia grass pollen with estimated molecular weights of 45, 33, 31 and 28 kD were identified and characterized. Following treatments with deglycosylation enzymes, the 4 allergens retained their antigenic reactivity with Bahia-grass-allergic patient sera containing polyclonal IgE antibodies. CONCLUSION: The crude extract of Bahia grass pollen contains many proteins but only 4 have allergenic reactivity. Following deglycosylation treatment, Bahia grass allergenic proteins have retained their antigenic reactivity with Bahia-grass-allergic patient sera containing polyclonal IgE antibodies. Four proteins reactive with IgE were detected, but the 33-kD protein (pI of 6.59) was the most reactive.