MAPPING OF EPITOPES ON POA P-I AND LOL P-I ALLERGENS WITH MONOCLONAL-ANTIBODIES

Allergen Poap I isolated from the dialysed aqueous extract of Kentucky blue grass pollen by affinity chromatography with an anti-Lolp I murine monoclonal antibody (MAb) 290A-167 was previously shown to consist of a 35.8-kilodalton (kD) component with a pi of 6.4, designated as Poap la, and a 33-kD component with a pi of 9.1, designated as Poap Ib. The present study reports on the comparative antigenic analyses of these two components, using MAbs produced separately against Poap I and Lolp I. Thus, anti-Poap I MAbs 60 and 61 and anti-Lolp I MAb 290A-167 recognized Poap Ia and Poap Ib whereas anti-Poap I MAbs 62, 63 and 64 and anti-Lolp I MAb 348A-6 recognized only Poa p Ia. The specificities of the MAbs were further resolved by comparing their respective abilities to inhibit the binding of l25 I--Poapi or l25I-LolpI to the different MAbs prepared in the form of solid phase. These studies revealed that at least 4 distinct epitopes (designated as E, E2, E3and E4) were shared by both Poa p\ and Lolp I. All 4 epitopes were present on Poap Ia whereas only E1 and E3 were detected on Poa p Ib. E, was recognized by MAbs 60 and 61, E2 by MAbs 62, 63 and 64, E3 by MAb 290A-167 and E4 by MAb 348A-6. The observations that MAb 290A-I67 inhibited significantly the binding of human IgE antibodies to Poap I and Lolp I were interpreted to indicate that epitope E3 may also constitute an allergenic site on both Poa p I and Lolp I. These studies revealed that Poa p I and Lolp I share extensive antigenic and allergenic cross-reactivities with one another. © 1990 S. Karger AG, Basel.