Antigen-specific Immunotherapy Regulates B Cell Activities in the Intestine

Mature B cells (BCs) express CD23 and B cell receptors. Whether activation of CD23 and B cell receptors has different effects on BC activities is unclear. This study aims to investigate the mechanism by which the specific antigen immunotherapy regulates the activation of BCs in the skewed Th2 responses. Mice were sensitized to ovalbumin. The specific antigen vaccination (SAV) at graded doses was employed to modulate the activities of BCs in which the expression of IL-10, IgE, matrix metalloproteinase-9 (MMP9), CD23, and serum soluble CD23 by BCs was evaluated. The immune regulatory effect of BCs primed by lower or higher SAV doses was observed with an adoptive transfer mouse experiment. SAV activated CD23 to produce IL-10 in BCs at lower doses. The higher doses of SAV increased the expression of MMP9 in BCs that reduced the amounts of CD23 in BCs and increased the serum levels of soluble CD23, which was abrogated by the pretreatment with MMP9 inhibitor. Adoptively transfer with BCs primed by lower doses of SAV inhibited the ongoing antigen-specific Th2 responses whereas the BCs primed by higher doses of SAV exacerbated the ongoing Th2 responses. Exposure to specific antigens at optimal doses can activate BCs to produce IL-10 to suppress the skewed antigen-specific Th2 responses. The antigen doses of SAV higher than the optimal doses may promote the production of soluble CD23 to exacerbate the ongoing immune responses.     

婴儿双歧杆菌对花生过敏小鼠模型肠道Th2反应的调节

目的研究婴儿型双歧杆菌对花生过敏小鼠肠道Th2型反应的调节作用。方法通过应用花生蛋白诱导肠道的Th2型反应,建立食物过敏小鼠模型。过敏小鼠灌胃给予婴儿型双歧杆菌（ATCC菌或CGMCC0313-2）或不做处理。然后分离小鼠小肠黏膜CD4＋T细胞或DC,另取肠黏膜组织进行石蜡包埋甲苯胺蓝染色肥大细胞计数,HE染色进行嗜酸细胞和单个核细胞计数,流式细胞检测CD4＋T中Th2（CD4＋IL4＋T）细胞和Treg（CD4＋CD25＋Foxp3＋T）比例,另取CD4＋T进行CFSE标记,与DC共培养4d后流式细胞检测CD4＋T增殖反应,收集细胞培养液ELISA检测IL-4、IL-5和IL—13分泌水平。结果过敏组小鼠Th2型细胞数,CD4＋T细胞增殖反应,IL4、IL-5和IL-13水平,肠黏膜中肥大细胞、嗜酸性细胞和单个核细胞数均明显高于对照组（P〈0．01）,而Treg数目低于对照组（P〈0．01）,婴儿双歧杆菌干预后,婴儿双歧杆菌组Th2型细胞数,IL4、IL-5和IL-13水平,肠黏膜中肥大细胞、嗜酸性细胞和单个核细胞数均明显低于过敏组（P〈0．01）,而Treg数目高于过敏组（P〈0．01）。结论口服婴儿型双歧杆菌可以抑制花生过敏导致的肠道Th2型反应。     

Longterm persistence of proteolytic activities in frass of Blattella germanica increases its allergenic potential

Chromogenic microplate assays in 96 wells were used to determine the stability of enzyme activity in frass of Blattella germanica (Blattodea: Blattellidae). Frass samples were exposed to controlled conditions [temperature 15-35 °C and/or 53-100% relative humidity (RH)] and to household conditions (apartment). Exposure times were 0 (control), 90, 183 and 276 days. Starch digestion and cellulolytic activities decreased during exposure. Non-specific proteolytic activities were affected by changes in selective proteolytic activities. Activities towards AAPpNA and SA(3) pNA strongly increased at 100% RH, indicating the possible influence of microorganisms growing on frass. Activities towards BApNA and ArgpNA decreased with increasing decomposition time, whereas activity towards ZRRpNA was not influenced by exposure time. The largest decrease in activities towards ArgpNA and BApNA occurred at temperatures of 15 °C, 30 °C and 35 °C and at 100% RH. Activities towards BApNA and ZRRpNA were very stable under different temperature and RH conditions; this was confirmed by findings showing that these activities were stable in the experimental apartment. In comparison with the control, activities towards ZRRpNA and BApNA after 276 days decreased by 1% and 19%, respectively. The longterm persistence of proteolytic activities in cockroach frass increases their allergenic hazard potential.     

实时荧光PCR检测食品中致敏原芥末成分

对植物原料产品和植物源性食品中芥末成分的快速鉴定是避免过敏性疾病发生的重要措施。依据芥末Sin A1管家基因的核酸序列设计特异性引物和探针,对3种芥末样品和21种非芥末植物样品进行实时荧光PCR检测,结果显示,过敏原芥末管家基因的样品FAM通道有荧光信号检出,非芥末样品FAM通道均无荧光信号检出。灵敏度实验表明,植物原料产品中对芥末的检测低限可达到1 mg/kg。此外对市售的芥菜籽等样品和深加工的芥末致敏原参考物质(葡萄糖)进行实际样品的检测,均能很好检出致敏原芥末成分。     

Structural and immunologic characterization of Ara h 1, a major peanut allergen

Allergic reactions to peanuts and tree nuts are major causes of anaphylaxis in the United States. We compare different properties of natural and recombinant versions of Ara h 1, a major peanut allergen, through structural, immunologic, and bioinformatics analyses. Small angle x-ray scattering studies show that natural Ara h 1 forms higher molecular weight aggregates in solution. In contrast, the full-length recombinant protein is partially unfolded and exists as a monomer. The crystal structure of the Ara h 1 core (residues 170-586) shows that the central part of the allergen has a bicupin fold, which is in agreement with our bioinformatics analysis. In its crystalline state, the core region of Ara h 1 forms trimeric assemblies, while in solution the protein exists as higher molecular weight assemblies. This finding reveals that the residues forming the core region of the protein are sufficient for formation of Ara h 1 trimers and higher order oligomers. Natural and recombinant variants of proteins tested in in vitro gastric and duodenal digestion assays show that the natural protein is the most stable form, followed by the recombinant Ara h 1 core fragment and the full-length recombinant protein. Additionally, IgE binding studies reveal that the natural and recombinant allergens have different patterns of interaction with IgE antibodies. The molecular basis of cross-reactivity between vicilin allergens is also elucidated.     

Bet v 1 from Birch Pollen Is a Lipocalin-like Protein Acting as Allergen Only When Devoid of Iron by Promoting Th2 Lymphocytes

It is hypothesized that allergens are at the borderline of self and non-self and, through as yet elusive circumstances, mount a Th2 response for allergic sensitization. The major birch pollen allergen Bet v 1 is considered the prototype for the PR-10 protein family causing respiratory allergy. Here, we give structural evidence that Bet v 1 is a lipocalin-like protein with a striking structural resemblance to human lipocalin 2. Lipocalin 2 is highly expressed in the lung where it exerts immunoregulatory functions dependent on being loaded with siderophore-bound iron (holo-form) or not (apo-form). We demonstrate that similar to lipocalin 2, Bet v 1 is capable of binding iron via catechol-based siderophores. Thereby, calculated K_d values of 66 nm surpassed affinities to known ligands nearly by a power of 10. Moreover, we give functional evidence of the immunomodulatory capacity of Bet v 1 being dependent on its iron-loaded state. When incubated to human immune cells, only the apo-form of Bet v 1, but not the holo-form, was able to promote Th2 cells secreting IL13. These results provide for the first time a functional understanding on the allergenicity of Bet v 1 and a basis for future allergen immunotherapies counteracting Th2 immune responses on a molecular basis.     

Resolution of the structure of the allergenic and antifungal banana fruit thaumatin-like protein at 1.7-A

The structure of a thaumatin-like protein from banana (Musa acuminata) fruit, an allergen with antifungal properties, was solved at 1.7-A-resolution, by X-ray crystallography. Though the banana protein exhibits a very similar overall fold as thaumatin it markedly differs from the sweet-tasting protein by the presence of a surface exposed electronegative cleft. Due to the presence of this electronegative cleft, the banana thaumatin-like protein (Ban-TLP) acquires a strong (local) electronegative character that eventually explains the observed antifungal activity. Our structural analysis also revealed the presence of conserved residues of exposed epitopic determinants that are presumably responsible for the allergenic properties of banana fruit towards susceptible individuals, and provided evidence that the Ban-TLP shares some structurally highly conserved IgE-binding epitopes with thaumatin-like proteins from fruits or pollen from other plants. In addition, some overlap was detected between the predicted IgE-binding epitopes of the Ban-TLP and IgE-binding epitopes previously identified in the mountain cedar Jun a 3 TLP aeroallergen. The presence of these common epitopes offers a molecular basis for the cross-reactivity between aeroallergens and fruit allergens.     

Detection of low-molecular weight allergens resolved on two-dimensional electrophoresis with acid-urea polyacrylamide gel

Two-dimensional electrophoresis with immobilized pH gradient (IPG) followed by acetic acid/urea-polyacrylamide gel electrophoresis (AU-PAGE) was developed for the detection of low-molecular weight food allergens. Wheat proteins were used to test the applicability of AU-PAGE for the analysis of food allergens. Isoelectric focusing (IEF) for first dimension was performed with IPG pH 3-10. AU-PAGE was performed as a second-dimensional electrophoresis and high resolution was obtained, especially for proteins below 15 kDa. For immunodetection, the proteins resolved on AU gel were transferred to a polyvinylidene difluoride membrane. The assembly of semidry electroblotting for AU gel was set reversed as for sodium dodecyl sulfate (SDS)-PAGE gel. The electroblotted membrane was immunolabeled with serum from a radio-allergosorbent test-positive individual for wheat to identify allergenic proteins. Protein spots strongly recognized by the patient's serum were chosen for further analysis. Mass spectrometry analysis revealed that these proteins were alpha-amylase/trypsin inhibitors and lipid transfer protein. The system developed in this study was shown to be useful as a standard protocol for the separation of low-molecular weight proteins. Moreover, the IPG strips on which IEF was performed could be used either for SDS-PAGE or AU-PAGE by only changing equilibrating conditions, allowing for a wide range of allergen analysis.