Multiple IgE recognition on the major allergen of the Parietaria pollen Par j 2

The Effector Function of Allergens

Allergens are antigens that generate an IgE response (sensitization) in susceptible individuals. The allergenicity of an allergen can be thought of in terms of its ability to sensitize as well as its ability to cross-link IgE/IgE receptor complexes on mast cells and basophils leading to release of preformed and newly formed mediators (effector activity). The identity of the allergens responsible for sensitization may be different from those that elicit an allergic response. Effector activity is determined by (1) the amount of specific IgE (sIgE) and in some circumstances the ratio of sIgE to total IgE, (2) the number of high affinity receptors for IgE (FcεR1) on the cell surface, (3) the affinity of binding of sIgE for its epitope and, in a polyclonal response, the collective avidity, (4) the number and spatial relationships of IgE binding epitopes on the allergen and (5) the presence of IgG that can bind to allergen and either block binding of sIgE and/or activate low affinity IgG receptors that activate intracellular inhibitory pathways. This review will discuss these important immunologic and physical properties that contribute to the effector activity of allergens.

Location of destroyed antigenic sites of Gly m Bd 60 K after three processing technologies

Gly m Bd 60 K, which is the α subunit of β-conglycinin, is a major soybean (Glycine max) allergen. We used high hydrostatic pressure (HHP), thermal techniques, and glycation to treat β-conglycinin, which can effectively reduce the antigenicity of β-conglycinin. β-conglycinin was used to immunize New Zealand rabbits, and the antiserum had a titer > 1: 1 × 105 and an IC50 of 2.254 μg/mL. β-conglycinin was subjected to HHP, thermal techniques, and glycation and mixed with rabbit antiserum against β-conglycinin to obtain the site-specific antiserum. The overlapping gene fragments of Gly m Bd 60 K were amplified by polymerase chain reaction (PCR), then cloned into a T7 phage vector and packaged in vitro, the recombinant T7 phages were constructed. Indirect ELISA (iELISA) was used to locate the destroyed antigenic sites and, after three rounds of segment expression and identification, the C2-1 and C2-2 fragments were identified as destroyed antigenic sites of Gly m Bd 60 K. Allergenicity analysis showed that the C2-1 and C2-2 fragments reacted with allergic patients' serum, which indicated that the destroyed sites were allergic sites.

Cross-reactivity between Parietaria judaica and Parietaria officinalis in immunotherapy extracts for the treatment of allergy to Parietaria

Parietaria judaica and P. officinalis are the two most common subspecies of the Parietaria genus. P. judaica and P. officinalis have exhibited cross-reactivity in previous studies. P. judaica pollen is the main cause of allergy in the Mediterranean area. It has been shown that a high percentage of patients sensitized to P. judaica with allergic rhinitis (AR) have an increased risk of developing asthma. The present study aimed to confirm the cross-reactivity between P. judaica and P. officinalis and to evaluate the use of a single P. officinalis extract in patients allergic to both subspecies as a preferable option for the diagnosis and treatment of allergy in a highly pollinated area of the Spanish Mediterranean coast. The present study was a single centre, observational cross-sectional study of adult patients diagnosed with AR and/or bronchial asthma who were sensitized to Parietaria pollen. A total of 24 patients were enrolled in the study and included in the analysis. Allergovit^® immunotherapy extracts were selected for the study based on the protein content (P. officinalis pollen extract). The results of an in vitro ELISA revealed that 79.1% (n=19) of the patient sera were reactive to immunotherapy extracts. ELISA inhibition assay of the IgE binding to P. officinalis demonstrated inhibition values >70% in the sera of highly reactive patients, confirming the cross-reactivity between the two Parietaria subspecies. In addition, all patients enrolled in the study exhibited double skin positivity against P. judaica and P. officinalis extracts, as assessed by the skin prick test, further supporting the in vivo reactivity between the two subspecies. The present study demonstrated that P. judaica and P. officinalis pollen extracts were highly cross-reactive, and that a unique P. officinalis pollen extract may be used for the diagnosis and immunotherapy of patients allergic to Parietaria.

Identification of antigenic sites destructed by high hydrostatic pressure (HHP) of the β subunit of β-conglycinin

β-conglycinin is one of the most allergenic proteins, and its constituent subunits α', α, and β are all potential allergens to humans. In the present study, we concentrated on the destructed antigenic sites of β subunit of β-conglycinin after high hydrostatic pressure (HHP) treatment. In this paper, the overlapping gene fragments of the β subunit of β-conglycinin were amplified by polymerase chain reaction (PCR) and cloned into T7 phage vectors. After being packaged in vitro, the recombinant T7 phage was constructed, and the overlapping fragments of the β subunit were displayed on the phage surface. The recombinant phages that expressed the overlapping fragments of the β subunit were used to react with specific antiserum by indirect ELISA to identify the HHP destructed antigenic sites. After three rounds of expression and identification, we used synthetic peptide technology to identify that the obtained fragment was a conformational epitope. We further confirmed that HHP treatment changed the conformational structure of β-conglycinin, which reduced the antigenicity of the protein.

Combination of two epitope identification techniques enables the rational design of soy allergen Gly m 4 mutants

Detailed IgE-binding epitope analysis is a key requirement for the understanding and development of diagnostic and therapeutic agents to address food allergies. An IgE-specific linear peptide microarray with random phage peptide display for the high-resolution mapping of IgE-binding epitopes of the major soybean allergen Gly m 4, which is a homologue to the birch pollen allergen Bet v 1 is combined. Three epitopes are identified and mapped to a resolution of four key amino acids, allowing the rational design and the production of three Gly m 4 mutants with the aim to abolish or reduce the binding of epitope-specific IgE. In ELISA, the binding of the mutant allergens to polyclonal rabbit-anti Gly m 4 serum as well as IgE purified from Gly m 4-reactive soybean allergy patient sera is reduced by up to 63% compared to the wild-type allergen. Basophil stimulation experiments using RBL-SX38 cells loaded with patient IgE are showed a decreased stimulation from 25% for the wild-type Gly m 4 to 13% for one mutant. The presented approach demonstrates the feasibility of precise mapping of allergy-related IgE-binding epitopes, allowing the rational design of less allergenic mutants as potential therapeutic agents.

Challenges for allergy diagnosis in regions with complex pollen exposures

Over the past few decades, significant scientific progress has influenced clinical allergy practice. The biological standardization of extracts was followed by the massive identification and characterization of new allergens and their progressive use as diagnostic tools including allergen micro arrays that facilitate the simultaneous testing of more than 100 allergen components. Specific diagnosis is the basis of allergy practice and is always aiming to select the best therapeutic or avoidance intervention. As a consequence, redundant or irrelevant information might be adding unnecessary cost and complexity to daily clinical practice. A rational use of the different diagnostic alternatives would allow a significant improvement in the diagnosis and treatment of allergic patients, especially for those residing in complex pollen exposure areas.