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

Identification of an allergen related to Phl p 4, a major timothy grass pollen allergen, in pollens, vegetables, and fruits by immunogold electron microscopy

Group 4 grass pollen allergens represent 60 kDa glycoproteins recognized by 70% of patients sensitive to these pollens. An antiserum against purified Phl p 4 from timothy grass pollen was used to investigate various pollens, fruits, and vegetables for Phl p 4-related allergens by immunogold electron microscopy. In timothy grass, mugwort, and birch pollens, allergens were located in the wall, and in timothy grass and birch pollens additionally in the cytoplasm. In peanut, apple, celery root, and carrot root, only cytoplasmic areas were labeled. Group 4-related allergens thus occur in pollens of unrelated plants and in plant food and may therefore contribute to crossreactivities in patients allergic to various pollens and plant food.

Isolation and partial characterization of a 46-kd allergen of Bermuda grass pollen

Cyn d Bd46K, a 46-kD component of Bermuda grass (Cynodon dactylon) pollen, had been identified as an allergenic constituent. In the present study two-dimensional (2D) gel electrophoresis illustrated the presence of five acidic isoforms in Cyn d Bd46K, and this molecule was purified by monoclonal antibody (MAb) affinity chromatography for further characterization. Using a digoxigenin-labeled lectin-binding assay, the elucidating protein was disclosed to be a glycoprotein with terminal mannose. The involvement of a carbohydrate moiety in the allergenicity and antigenicity of the elucidated molecule was demonstrated with sodium-periodate-treated Cyn d Bd46K, which reduced binding to its specific MAb and human IgE. We were unable to identify the N-terminal amino acid sequences of Cyn d Bd46K, but some internal amino acid sequences were disclosed by microsequencing some fragments cleaved by Achromobacter protease I and fractionated by reversed-phase column chromatography. The amino acid sequences of 4 identified Cyn d Bd46K internal peptide fragments were found to be 25-71% identical with that of cytochrome c oxidase III from corn grass pollen. The present study provided important information for future experiments on the molecular cloning of the elucidated allergen.

The high molecular mass allergen fraction of timothy grass pollen (Phleum pratense) between 50-60 kDa is comprised of two major allergens: Phl p 4 and Phl p 13

BACKGROUND

More than 70% of the patients allergic to grass pollen exhibit IgE-reactivity against the high molecular mass fraction between 50 and 60 kDa of timothy grass pollen extracts. One allergen from this fraction is Phl p 4 that has been described as a basic glycoprotein. A new 55/60 kDa allergen, Phl p 13, has recently been purified and characterized at the cDNA level.

OBJECTIVE

The relative importance of the two high molecular mass allergens has been characterized with respect to their IgE-binding frequency and capacity.

METHODS

Both high molecular mass allergens were biochemically purified and subjected to nitrocellulose strips. About 306 sera obtained from subjects allergic to grass pollens were used to determine specific IgE-binding frequency to Phl p 4 and Phl p 13. IgE-binding of allergens was quantified by ELISA measurements. Pre-adsorption of sera with purified allergens and subsequent incubation of nitrocellulose-blotted timothy grass pollen extract was performed to determine whether or not Phl p 4 and Phl p 13 represent the whole high molecular mass allergen fraction. Proteolytic stability of both allergens was investigated by addition of protease Glu-C.

RESULTS

More than 50% of 300 patients displayed IgE-binding with both allergens. Clear differences concerning the immunological properties of Phl p 4 and Phl p 13 were confirmed by individual IgE reactivities. Quantification of specific IgE for both allergens revealed comparable values. For complete inhibiton of IgE-binding in the high molecular mass range preincubation of sera with both allergens was necessary. Interestingly, inhibition of strong reacting sera with Phl p 13 eliminated not only reactivity of the 55/60 kDa double band, but in addition a 'background smear'. Whilst undenatured Phl p 4 was resistent to proteolytic digestion with Glu-C, native Phl p 13 was degraded rapidly.

CONCLUSION

Phl p 4 and Phl p 13 are immunologically different and must both be considered as major allergens. They are judged to be important candidates for potential recombinant therapeutics that may provide a basis for improved immunotherapy.

Detection and quantification of group 4 allergens in grass pollen extracts using monoclonal antibodies

BACKGROUND

Grass pollen extracts are complex mixtures consisting of different major allergenic and non-allergenic components. Phl p 4 is an important allergen, because more than 75% of grass pollen allergic patients produce specific IgE antibodies against group 4 allergens.

OBJECTIVE

This study was designed to investigate the specificity of monoclonal antibodies (MoAbs) produced against Phl p 4 and to verify the presence of group 4-like proteins in different grass pollen. Furthermore the usefulness of MoAbs for quantification of group 4 allergens was studied.

METHODS

Group 4 analogues were investigated by immunoblotting and ELISA inhibition using three MoAbs. The specificity of antibodies was studied using isolated group 1 and group 5 allergens. Quantification of group 4 allergen was achieved by a two-site solid-phase ELISA. Phl p 4 was purified from whole pollen extract by chromatographic or electrophoretic techniques and used as standard.

RESULTS

The MoAbs studied bound strongly to proteins from timothy grass pollen extract at a mw of 55 kDa and a pI of 9.0-9.3. Phl p 4 homologes with similar mw were detected in Dactylis glomerata, Festuca pratensis, Holcus lanatus, Poa pratensis, Lolium perenne. Epitope mapping showed that all three MoAb recognized unrelated regions on Phl p 4. A two-site binding ELISA using MoAbs was developed for determination of Phl p 4 in Phleum pratense extracts. The method was able to evaluate group 4 in mass units with a working range between 150 and 2000 ng/mL. The absolute amounts of group 4 in extracts of several grasses varied considerably but was always-less than 1% of the total protein.

CONCLUSION

Group 4 homologes are present in the various grass extracts but to different extents. The group 4 ELISA could be very useful as a additional tool for providing information concerning the composition of grass pollen extracts.

A murine monoclonal anti-idiotypic antibody detects a common idiotope on human, mouse and rabbit antibodies to allergen Lol p IV

A syngeneic mouse monoclonal anti-idiotypic antibody (anti-Id), designated as B1/1, was generated against a monoclonal antibody (MoAb 91) specific for Ryegrass pollen allergen Lol p IV. This anti-Id recognized an idiotope (Id) that was also present on other monoclonal antibodies with the same specificity as MoAb 91. Observations that (i) the anti-Id inhibited the binding of MoAb 91 to Lol p IV and (ii) the Id-anti-Id interaction could be inhibited by Lol p IV indicated that the Id was located within or near the antigen combining site. These properties served to characterize B1/1 as an internal image anti-Id. Evidence that an immune response in different species to Lol p IV elicits the formation of antibodies which express a common Id was provided by the observations that (i) the Id-anti-Id interactions could be inhibited by mouse, human and rabbit antisera to Lol p IV and (ii) the binding of these antisera to Lol p IV could be inhibited by the anti-Id. Interestingly, the internal image anti-Id B1/1 also recognized an Id on a monoclonal antibody which was directed to an epitope of Lol p IV, different from that recognized by MoAb 91.