Mapping of epitopes on Poa p I and Lol p I allergens with monoclonal antibodies

Allergen Poa p I isolated from the dialysed aqueous extract of Kentucky blue grass pollen by affinity chromatography with an anti-Lol p 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 Poa p Ia, and a 33-kD component with a pI of 9.1, designated as Poa p Ib. The present study reports on the comparative antigenic analyses of these two components, using MAbs produced separately against Poa p I and Lol p I. Thus, anti-Poa p I MAbs 60 and 61 and anti-Lol p I MAb 290A-167 recognized Poa p Ia and Poa p Ib whereas anti-Poa p I MAbs 62, 63 and 64 and anti-Lol p 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 125I-Poa p I or 125I-Lol p I to the different MAbs prepared in the form of solid phase. These studies revealed that at least 4 distinct epitopes (designated as E1, E2, E3 and E4) were shared by both Poa p I and Lol p I. All 4 epitopes were present on Poa p Ia whereas only E1 and E3 were detected on Poa p Ib. E1 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunochemical characterization of cocos nucifera pollen

The Cocos nucifera pollen, as one of the sources of allergen responsible for immediate hypersensitivity reaction, was confirmed by skin prick test, bronchial provocation test, and RAST. The whole pollen extract (WPE) of C. nucifera was fractionated by combination of gel filtration and ion-exchange columns with fast protein liquid chromatography (Pharmacia, Uppsala, Sweden). Three protein peaks designated Cocos II, Cocos VI, and Cocos VII exhibited allergenic properties, as tested by skin prick test, direct IgE ELISA, bronchial provocation test, and immunoblot analysis. In RAST inhibition, Cocos IIa (a high-molecular-weight protein) obtained by fractionation of Cocos II on Mono Q column (fast protein liquid chromatography) (Pharmacia) was found to be the most potent allergen in Cocos WPE, followed by Cocos VI and Cocos VII, which are low-molecular-weight proteins. The reference patterns of Cocos WPE on crossed immunoelectrophoresis and thin-layer isoelectric focusing were established for future standardization of Cocos WPE to be used in the diagnosis and immunotherapy of allergic patients.

Identification of two distinct allergenic sites on ryegrass-pollen allergen, Lol p IV

Lol p IV is an important allergen of ryegrass pollen. For the immunochemical identification of antigenic and/or allergenic site(s), murine monoclonal antibodies (MAbs) were prepared against Lol p IV. The hybridoma cell-culture supernatants were screened for anti-Lol p IV antibodies by a combination of ELISA and Western immunoblot analyses. The MAbs were finally purified from ascites on a Mono Q ion-exchange column. In a competitive radioimmunoassay with Lol p IV as the solid phase and 125I-labeled MAbs, it was established that MAbs 90, 91, 92, 93, and 94, although they differed in their relative affinities, recognized in common with one another an epitope designated as antigenic site A, whereas MAb 12 recognized a different epitope referred to as site B. Sites A and B were also demonstrated to constitute allergenic determinants of Lol p IV. Differences in the repertoire of specificities of the human IgE antibodies directed to Lol p IV were also demonstrated. Interestingly, it was found that sera from both allergic as well as from nonatopic individuals had IgG antibodies to sites A and/or B.

Allergenic fragments of ryegrass (Lolium perenne) pollen allergen Lol p IV

To facilitate studies on establishing the nature of structure/function relationships of allergens, ryegrass pollen allergen, Lol p IV, was cleaved into smaller fragments by cyanogen bromide (CNBr) and the resulting peptides were further digested with trypsin. The resulting peptides were then fractionated by high performance liquid chromatography (HPLC) on a C-18 reverse phase column. The allergenic activity of the HPLC fractions was evaluated in terms of their ability to inhibit the binding of 125I-Lol p IV to serum IgE antibodies of a grass-allergic patient. Many of these fractions inhibited the binding between the native allergen and IgE antibodies in a dose-dependent manner. The inhibitions were specific, i.e., the fractions did not inhibit the binding between 125I-Lol p I (a group-I ryegrass pollen allergen) and the IgE antibodies present in the allergic human serum. The possibility that the allergenic peptide fractions were contaminated by the native undegraded allergen, which might have accounted for the observed inhibition, was ruled out by the fact that the native allergen could not be detected by SDS-PAGE and the elution profiles of allergenically active peptides did not coincide with that of native allergen. One of the allergenic sites recognized by monoclonal antibody (Mab) 90, i.e., site A, was located in HPLC fractions 90-100 while another allergenic site B (recognized by Mab 12) appeared to be lost following the sequential digestion of Lol p IV with CNBr and trypsin.

Monitoring of active groups of cyanogen-bromide-activated paper discs used as allergosorbent

The amount of active groups of cyanate esters and imidocarbamates present on cyanogen-bromide-activated paper discs were estimated. The protein-binding capacity of activated discs was found to be dependent on the amount of these active groups. The results suggested that monitoring of active groups on activated discs can help in preparing consistent allergosorbent for immunoassays.

Purification and characterization of allergens from Xanthium strumarium pollen

The allergenic components present in whole pollen extract of Xanthium strumarium were isolated by sequential ammonium sulphate precipitation, DEAE Sephadex A50 chromatography and gel filtration. The techniques of RAST inhibition and skin test were utilized to check the allergenicity of fractionated proteins revealing the presence of Xan Ib and Xan VIa as the important allergenic components. Xan Ib was found to be devoid of carbohydrate and had a molecular weight of 103,000 daltons. Xan VIa was a glycoprotein of molecular weight 17,000 daltons. The carbohydrate moiety of Xan VIa was found to be associated with allergenicity. The characteristic pattern of whole pollen extract on CIE and TLIEF showed 36 and 21 protein bands, respectively. The use of FPLC in isolation of partially purified allergens from Xanthium is discussed.

Isolation and identification of pollen allergens of Artemisia scoparia

The allergenic proteins of Artemisia scoparia pollen were separated and identified with ammonium sulfate precipitation, ion-exchange chromatography, gel filtration, and RAST-inhibition techniques. The important allergenic component Artemisia VI b that constitutes 29% of total protein in the extract was purified to homogeneity. It was found to be an acidic protein with isoelectric point 3.8 and molecular weight of 14,300. It was rich in carbohydrate, but the carbohydrate portion did not appear to be important for allergenicity. In the crossed immunoelectrophoresis reference pattern of the whole pollen extract, 37 precipitin lines could be identified on the anodic side, whereas Artemisia VI b could be observed as a single precipitin line. Immunologically, the whole pollen extract of A. scoparia demonstrated shared antigenic and allergenic determinants with Ageratum conyzoides-pollen extract. The use of fast protein liquid chromatography in partial purification of allergenic components is also discussed.