Specific immune response to Phleum pratense plant profilin in atopic patients and control subjects

Strong and frequent T-cell responses to the minor allergen Phl p 12 in Spanish patients IgE-sensitized to Profilins

BACKGROUND

Profilins are dominant pan-allergens known to cause cross-sensitization, leading to clinical symptoms such as pollen-food syndrome. This study aimed to determine the T-cell response to Phl p 12 in profilin-sensitized patients, by measuring the prevalence, strength and cross-reactivity to clinically relevant profilins.

METHODS

The release of Phl p allergens from pollen was determined by mass spectrometry and immunochemistry. T-cell responses, epitope mapping and cross-reactivity to profilins (Phl p 12, Ole e 2, Bet v 2 and Mal d 4) were measured in vitro using PBMCs from 26 Spanish grass-allergic donors IgE-sensitized to profilin. Cross-reactivity was addressed in vivo using 2 different mouse strains (BALB/c and C3H).

RESULTS

Phl p 12 and Phl p 1 are released from pollen simultaneously and in similar amounts. Both T-cell response frequency (17/26 donors) and strength were comparable between Phl p 12 and Phl p 1. T-cell cross-reactivity to other profilins correlated with overall sequence homology, and 2 immunodominant epitope regions of Phl p 12 were identified. Data from mice immunized with Phl p 12 showed that cross-reactivity to Bet v 2 was mediated by conserved epitopes and further influenced by additional genetic factors, likely to be MHC II.

CONCLUSION

The strength, prevalence and cross-reactivity of T-cell responses towards Phl p 12 are comparable to the major allergen Phl p 1, which supports the hypothesis that T cells to Phl p 12 can play an important role in development of allergic symptoms, such as those associated with pollen-food syndrome.

Detection of pan-allergens in commercial pollen extracts for allergen immunotherapy

BACKGROUND

Up to 50% of patients with pollen allergy are sensitized to at least 1 of the 2 pollen pan-allergens profilin and polcalcin. These allergens could have clinical relevance but the content of profilin and polcalcin in commercial extracts for allergen immunotherapy (AIT) is unknown.

OBJECTIVE

To detect these pan-allergens in commercial pollen extracts for AIT from various sources.

METHODS

Immunoglobulin E (IgE) reactivity to Phl p 7 and Bet v 2 of sera from 18 adults hypersensitive to profilin and/or polcalcin was investigated by enzyme-linked immunosorbent assay before and after absorption with grass, birch, ragweed, pellitory, and olive pollen extracts for AIT from different producers. Immunoblot inhibition experiments also were carried out using the same allergens.

RESULTS

Birch, grass, ragweed, and olive pollen extracts for AIT contained large amounts of profilin, inducing 80% to 90% inhibition in most cases; Parietaria AIT extract appeared to contain little profilin. On immunoblot, grass and birch pollen extracts for sublingual AIT completely absorbed IgE specific for rBet v 2. Interestingly, only grass pollen extracts induced a significant inhibition of IgE binding to rPhl p 7 on enzyme-linked immunosorbent assay and immunoblot. A grass pollen allergoid lost most of its inhibitory potency, suggesting a much weakened affinity for specific IgE.

CONCLUSION

With the exception of Parietaria, commercial extracts for AIT of most pollens are rich in profilin and, hence, potentially able to desensitize to this allergen; in contrast, only grass pollen extracts seem rich in polcalcin. These are the pollens to use in case of severe symptoms induced by pollen pan-allergens.

Sensitization to timothy grass pollen allergenic molecules in children

BACKGROUND

Grass pollens are significant elicitors of IgE-mediated allergic disease in the world and timothy (Phleum pratense) is one of the most important pollens of the family. Molecular and biochemical characterization of Phleum pratense has revealed several allergen components: rPhl p 1 and rPhl p 5 have been shown to be "Species Specific Allergens", while the profilin rPhl p 12 and the calcium-binding protein rPhl p 7 are the principal Cross-Reactive components.

METHODS

In this study the pattern of sensitization to rPhl p 1, rPhl p 5, rPhl p 7 and rPhl p 12 was analyzed in children with asthma and/or rhinoconjunctivitis and grass pollen allergy, in order to evaluate the frequency of sensitization to allergenic molecules of Phleum pratense among pediatric subjects allergic to grass pollen in a Mediterranean population. The correlation of sensitization to these Phleum allergenic molecules with IgE against grass pollen extract and its variation according to age and level of IgE against grass pollen extract were evaluated.

RESULTS

IgE against to rPhl p 1 were found in 99% (205/207) of patients, to rPhl p 5 in 67% (139/207), to rPhl p 12 in 32% (66/207) and to rPhl p 7 only in 5% (10/207).Sensitization only to "Species Specific" (rPhl p1, rPhl p5) allergenic molecules of Phleum pratense was detected in 65% (135/207) of children. Our data show the predominant role of rPhl p 1 in pediatric populations as the most relevant sensitizing allergen detectable at all ages and at all levels of timothy grass pollen-specific IgE antibodies, while the importance of rPhl p 5 rises with the increase of patients' age and with grass pollen IgE levels.

CONCLUSIONS

The assessment of sensitization to grass pollen allergenic molecules could help develop a better characterization of allergic sensitization in grass pollen allergy in children, which may be different in every patient. It could also enable clinicians to give more specific and effective immunotherapy, based on allergenic molecule sensitization.

Previously undescribed grass pollen antigens are the major inducers of T helper 2 cytokine-producing T cells in allergic individuals

T cells play an important role in the pathogenesis of allergic diseases. However, the proteins considered as potential immunogens of allergenic T-cell responses have traditionally been limited to those that induce IgE responses. Timothy grass (TG) pollen is a well-studied inhaled allergen for which major IgE-reactive allergens have also been shown to trigger T helper 2 (Th2) responses. Here we examined whether other TG pollen proteins are recognized by Th2 responses independently of IgE reactivity. A TG pollen extract was analyzed by 2D gel electrophoresis and IgE/IgG immunoblots using pooled sera from allergic donors. Mass spectrometry of selected protein spots in combination with de novo sequencing of the whole TG pollen transcriptome identified 93 previously undescribed proteins for further study, 64 of which were not targeted by IgE. Predicted MHC binding peptides from the previoulsy undescribed TG proteins were screened for T-cell reactivity in peripheral blood mononuclear cells from allergic donors. Strong IL-5 production was detected in response to peptides from several of the previously undescribed proteins, most of which were not targeted by IgE. Responses against the dominant undescribed epitopes were associated with the memory T-cell subset and could even be detected directly ex vivo after Th2 cell enrichment. These findings demonstrate that a combined unbiased transcriptomic, proteomic, and immunomic approach identifies a greatly broadened repertoire of protein antigens targeted by T cells involved in allergy pathogenesis. The discovery of proteins that induce Th2 cells but are not IgE reactive may allow the development of safer immunotherapeutic strategies.

Antibody profiles and self-reported symptoms to pollen-related food allergens in grass pollen-allergic patients from northern Europe

BACKGROUND

Most studies on pollen-related food allergy have so far focused on the association of birch/weed pollen allergens and plant food allergy. The aim of this study was to elucidate the allergen spectrum among a group of grass pollen-allergic patients from northern Europe and to relate the results to clinical histories of pollen-related food allergy.

METHODS

Fifty-eight grass pollen-allergic patients answered a questionnaire regarding allergy to foods. Blood samples were taken to test IgE-reactivity to a large panel of pollen allergens and pollen- and nonpollen-related food allergens using crude allergen extracts and recombinant and native allergens.

RESULTS

Three different groups of grass pollen-allergic patients were identified according to their IgE antibody profile: a grass pollen group only (19%), a grass and tree pollen group (29%) and a grass, tree and compositae (pan-) pollen group (48%). No sensitization to Bet v 1 as well as almost no IgE to plant food was observed in the grass pollen group. In contrast, nearly all patients in the two tree-related groups had IgE to Bet v 1, which reflected the high frequency of adverse reactions to typical birch-related food in these groups. Only four patients belonging to the pan-pollen group displayed IgE to profilin Phl p 12/Bet v 2. Patients in the pan-pollen group reported significantly more symptoms to food allergens compared with patients in the two other groups. The most frequently reported symptom was the oral allergy syndrome.

CONCLUSIONS

Sensitization to grass pollen alone is rare among grass pollen-allergic patients from northern Europe. The majority of patients are in addition sensitized to birch (Bet v 1), which seems to be closely related to their pollen-derived food allergy. The study highlights the advantage of using well-defined allergen molecules for the diagnosis of cross-reactivity between pollen and food allergens.

Specific immune response to Parietaria judaica plant profilin: a low T cell proliferative response supports high IgE and skin prick test

BACKGROUND

allergic disease caused by Parietaria judaica (Pj) has been widely documented in Mediterranean area. Profilins have been identified as widely distributed allergenic proteins. The role of Pj profilin in specific immune response in Pj-sensitized patients is unknown.

METHODS

skin prick test and determination of specific and total IgE levels in serum were performed in all patients (n = 28) and non-allergic controls (n = 18). Peripheral blood mononuclear cells (PBMC) were isolated from both groups and stimulated with crude extract or highly purified Pj profilin. The production of type I and type II cytokines was determined by specific and polyclonal stimuli in patients and controls. T-cell lines specific to Pj profilin were established and cross-reactivity with another highly purified profilin from Phleum pratense (Phl p) was evaluated.

RESULTS

Pj profilin-sensitized patients showed a small but significantly increased in T-cell proliferative response to this profilin compared with non-atopic controls. The production of interleukin (IL)-4 and interferon (IFN)-γ in response to the specific stimulus was undetectable. However, the production of IL-4 in response to a polyclonal stimulus [phytohemagglutinin (PHA)] was significantly higher in atopic patients than in controls. The T-cell response did not correlate with the magnitude of response to skin prick tests with Pj profilin or with Pj-specific serum IgE levels. In addition, the production of IL-4 in response to a polyclonal stimulus (PHA) did not correlate with the individual skin prick tests to Pj profilin or with Pj-specific IgE levels in serum. The T-cell lines tested showed no cross-reactivity with Phl p profilin.

CONCLUSIONS

our results suggest that Pj profilin is partly responsible for the T-cell-mediated response in patients allergic to Pj. The high skin reactivity to Pj profilin is these patients was accompanied by a small increase in the T-cell response to this profilin. The response was highly specific since Pj profilin specific T-cell lines showed no cross-reactivity with a highly homologous profilin from Phl p. The lack of correlation between the proliferative T-cell response and polyclonal IL-4 production with allergen-specific serum IgE and skin reactivity probably indicates that some of the responding T-cells may be involved in immune reactions other than those supporting IgE production.