猫主要过敏原Fel d 1的T细胞抗原表位分析及三维结构模拟

目的:预测猫主要过敏原Fel d 1与MHC Ⅰ、MHCⅡ类分子的结合力获得T细胞优势抗原表位,并模拟Fel d 1的三维结构,为猫主要过敏原的改造及其临床研究等提供依据.方法:从Uniprot数据库中得到猫主要过敏原Fel d 1的氨基酸序列,通过在线软件NetMHCⅡ2.2对Fel d 1氨基酸序列进行MHCⅡ抗原表位分析,使用软件SYFPEITHI分析MHC Ⅰ的抗原表位,再通过在线软件Swiss-Model预测Feld1的三维结构,以Ramachandran图评估三维结构的稳定性.结果:运用生物学软件分析得到Fel d 1上两个高值MHCⅡ抗原表位区域分别为22～43、80～95,MHC Ⅰ抗原表位优势区为17～30、56～84、91 ～103.Ramachandran图显示Feld 1的空间构象稳定.结论:本研究有助于确定Fel d 1的T细胞优势抗原表位及其三维结构模型,为Fel d 1抗原性改造提供理论依据,及将来的临床研究奠定基础.     

欧洲女贞花粉主要过敏原Lig v 1 理化性质与结构的生物信息学分析

目的:运用生物信息学相关软件,预测欧洲女贞花粉主要过敏原Lig v 1 的理化性质和结构,为Lig v 1 重组表达系统的选择和过敏原性改造提供参考。方法:查询文献获得Lig v 1 的氨基酸序列,运用生物信息学软件分析其理化性质(ProtParam)、信号肽(SignalP 4.1 Server)、跨膜区(TMHMM Server v.2.0)、二级结构(GOR4)、MHC域类抗原表位(NetMHC域2.2 Server)、B 细胞抗原表位(ProteanTM 5.01)以及系统发生树(MEGA 6)。结果:Lig v 1 在大肠杆菌中稳定性较好,不存在信号肽与跨膜区;二级结构中无规则卷曲占大多数;Lig v 1 潜在MHC域类抗原表位为30 ~44 区域;B 细胞抗原表位既具有连续的氨基酸序列,也具有不连续的氨基酸序列;Lig v 1 与欧洲白蜡以及木犀榄的同源蛋白进化距离最近。结论:大肠杆菌是适合重组Lig v 1 的表达系统,Lig v 1 抗原表位分析为低过敏原性改造提供参考。     

应用免疫信息学技术预测严重急性呼吸综合征冠状病毒2(SARS-CoV-2)的抗原表位

目的运用免疫信息学技术预测严重急性呼吸综合征冠状病毒2(SARS-CoV-2)的B细胞、细胞毒性T淋巴细胞(CTL)和辅助T(Th)细胞的抗原表位。方法从NCBI数据库检索SARS-CoV-2蛋白序列,根据抗原性≥0.5和氨基酸数≥100进行筛选,最终的蛋白序列用于后续的抗原肽的预测。用蛋白质结构预测软件Phyre2进行三维结构的预测、蛋白质模型结构的细化软件GalaxyRefine优化蛋白的三维结构,最后用蛋白质结构同源建模SWISS-MODEL系统对优化后的结构进行准确性评估。蛋白序列用于CTL、Th细胞和线性B细胞抗原肽预测,三维结构用于结构性B细胞抗原预测。免疫表位数据库和分析资源(IEDB)预测SARS-CoV-2的CTL和Th细胞抗原表位,B细胞线性抗原肽预测软件Bepipred Linear Epitope Prediction 2.0和B细胞结构抗原肽预测软件ElliPro-Epitope prediction based upon structural protrusion分别预测B细胞线性和结构抗原肽。结果从NCBI数据库获得了27个SARS-CoV-2的蛋白序列,去掉抗原性0.5和氨基酸数100的蛋白质后,最终选定9个蛋白进行后续抗原肽预测。最终获得了24个CTL、20个Th细胞、12个B细胞线性表位和16个B细胞结构表位。结论获得的抗原表位可用于后续多表位疫苗的设计,相较于只针对单种蛋白靶点的抗原表位而言,多靶点抗原表位具有更强的免疫原性,这些抗原表位对SARS-CoV-2疫苗而言,具有一定的参考价值。     

MHC-Ⅱ类抗原表位预测软件的对比评价

比较不同MHC-Ⅱ类抗原表位预测软件的优缺点,为后续应用提供依据.在众多HLA-Ⅱ类抗原表位中,选取HLA-DR的6个表位(DRB1*0101, 0301, 0401, 0701, 1101和1501)为代表,选取MHCBN数据库中的309条已知抗原表位的肽链为待测肽链.使用近年来常用的7个表位预测软件,根据不同软件的临界值确定入选结果数据,比较各软件所得结果与已有的实验结果之间的差距以确定其优劣.综合7个软件预测结果进行评价,得出NetMHCⅡ和NetMHCⅡpan所得结果准确率最高.可以用NetMHCⅡpan及NetMHCⅡ进行MHC-Ⅱ类分子抗原表位预测.不同软件HLA的各个亚型的预测所得指标不一致,提示综合运用不同软件对多肽表位进行预测十分必要.     

严重急性呼吸综合征冠状病毒2(SARS-CoV-2)刺突蛋白的B细胞及T细胞抗原表位的生物信息学分析

目的 使用生物信息学方法预测严重急性呼吸综合征冠状病毒2(SARS-CoV-2)刺突蛋白(S蛋白)的结构特点，并预测可能的B细胞和T细胞表位。方法 从NCBI数据库中获取SARS-CoV-2的S蛋白氨基酸序列，通过蛋白质基本性质分析工具ProtParam分析S蛋白的理化性质；利用综合性序列工具软件Lasergene和蛋白质二级结构分析软件SOMPA分析S蛋白二级结构；蛋白质同源物/类似物Y识别引擎Phyre2和分子图像观察软件Rasmol构建并分析S蛋白三级结构；B细胞表位预测工具ABCpred、 BepiPred和BcePred预测S蛋白的B细胞抗原表位；利用免疫表位数据库IEDB预测S蛋白的T细胞抗原表位。结果S蛋白由1273个氨基酸组成，理论等电点为6.24,原子组成为C₆₃₃₆H₉₇₇₀N₁₆₅₆O₁₈₉₄S₅₄,属于稳定亲水性蛋白。Lasergene软件的Gramier-Robson方法预测显示：α螺旋占23.5%、 β折叠占53.7%、转角区域占14.9%、无规则卷...     

旋毛虫抗原分子克隆及其T细胞和B细胞表位预测

目的 克隆旋毛虫肌幼虫Mr21 000抗原蛋白基因(Ts21),预测其T细胞和B细胞表位.方法 旋毛虫(河南地理株)感染小鼠后收集肌幼虫,提取肌幼虫总RNA,应用RT-PCR技术获取目的基因Ts21,构建重组质粒pUC18-Ts21并测序,应用生物信息分析软件预测其T细胞和B细胞表位.结果 成功构建克隆载体pUC18-Ts21.旋毛虫Mr21 000抗原的T细胞表位位于第9～23、135～150位氨基酸位点;B细胞表位位于第31～35、53～56、98～104、124～130、133～157、160～172位氨基酸位点.结论 成功克隆了旋毛虫河南地理株肌幼虫Mr21 000抗原的编码基因,T细胞和B细胞表位预测结果表明该抗原蛋白具有较好的抗原性,可作为旋毛虫病免疫诊断和预防的候选抗原.     

细粒棘球绦虫多价EgA31-EgG1Y162抗原序列优化分析

目的:将优化的EgA31-EgG1Y162抗原基因构建于pET30a上,诱导蛋白表达,SDS-PAGE鉴定蛋白表达效果,用生物信息学软件分析优化的EgA31-EgG1Y162抗原序列,为构建高效的疫苗奠定理论基础。方法:运用ProtParam,DNAstar,E.coli Codon Usage Analyzer等多种生物信息学软件分析优化后EgA31-EgG1Y162蛋白的理化性质,比较其优化前后序列的异同点及抗原表位分布情况等。结果:EgA31-EgG1Y162蛋白属于不稳定性蛋白且亲水性蛋白,通过网上在线软件分析,优化序列的密码子中不含利用率低的密码子。表位预测分析确定6个T细胞表位的氨基酸区域1～15、86～97、177～193、359～388、305～319、344～358和7个B细胞表位为102～112、172～204、318～334、343～353、394～409、415～431、443～458。结论:多价EgA31-EgG1y162融合抗原蛋白的优化序列中不含利用率低的密码子,且T和B细胞表位未受影响,为重组蛋白体外的有效表达奠定实验基础,对包虫病的多价表位疫苗研究具有...     

人源α-烯醇化酶B细胞表位鉴定及其与牙龈卟啉单胞菌烯醇化酶的交叉反应预测

目的:预测鉴定人源α-烯醇化酶蛋白的B细胞抗原表位,探讨人源α-烯醇化酶与牙龈卟啉单胞菌烯醇化酶之间的交叉反应性。方法:以人源α-烯醇化酶蛋白序列为基础,综合应用多个软件预测B细胞线性表位;再以人源α-烯醇化酶的蛋白晶体结构为基础,采用4个生物信息学软件综合预测B细胞构象表位;利用原核表达系统对人源α-烯醇化酶蛋白进行表达、亲和层析法进行,纯化抗原免疫BALB/c小鼠,化学合成预测的线性表位片段检测抗体反应,确定人源α-烯醇化酶蛋白B细胞表位。利用Clustal X进行蛋白质序列比对和Swiss-Model进行同源模建,研究人源α-烯醇化酶和牙龈卟啉单胞菌烯醇化酶的交叉反应性。结果:人源α-烯醇化酶线性B细胞表位优势区域为9-25aa,28-43aa,70-85aa,163-178aa,229-244aa,280-295aa;构象性B细胞表位优势区域为:1-4/24-30/77-86/124aa,9-16/51-59aa,250-254/262-268/271-274aa;合成的线性表位片段中9-25aa免疫应答反应最强烈,其次是70-85aa,再次为28-43aa,163-178aa,229-244aa,280-295aa;牙龈卟啉单胞菌烯醇化酶和人源α-烯醇化酶氨基酸序列同源性高达50.11%,两者在线性B细胞表位优势区域的9-24aa和32-42aa序列高度相似;空间构象比对结果显示牙龈卟啉单胞菌烯醇化酶和人源α-烯醇化酶之间的RMSD值为1.055,且两者在3个构象性B细胞表位优势区域的空间构象高度相似,推测二者可能在上述区域发生交叉反应。结论:预测并鉴定了人源α-烯醇化酶蛋白的B细胞抗原表位,比较其与牙龈卟啉单胞菌的烯醇化酶可能发生交叉反应的位点,为研究人源α-烯醇化酶蛋白的自身抗原性和类风湿性关节炎发病机制提供了理论基础。     

人易感H6N1禽流感病毒血凝素蛋白的B细胞抗原表位预测及进化分析

目的预测人易感H6N1禽流感病毒血凝素蛋白的B细胞抗原表位,并分析其进化特征。方法从GISAID和Gen Bank两大数据库获得人易感H6N1病毒的血凝素蛋白及近缘序列,采用多款预测软件分别预测了其B细胞线性和构象型抗原表位,并分析了这些表位的保守性、适应性和进化特征。结果综合各种因素共预测出4个线性表位(表位A、B、C和D)和2个构象型表位(表位E和F)。表位C和位点41、157、186、187在进化过程中易发生突变,其余表位较为保守,其中表位D最保守;位点157受到强烈的正选择作用,它可能是H6N1病毒逃避宿主免疫系统攻击的一个关键位点。结论人易感H6N1禽流感病毒血凝素蛋白拥有5个保守的B细胞抗原表位(3个线性、2个构象型)和1个正选择作用位点,将为其疫苗的研制、致病机制的理解和病毒防治提供理论基础。     

人易感H6N1禽流感病毒血凝素蛋白的B细胞抗原表位预测及进化分析北大核心CSCD

目的预测人易感H6N1禽流感病毒血凝素蛋白的B细胞抗原表位,并分析其进化特征。方法从GISAID和Gen Bank两大数据库获得人易感H6N1病毒的血凝素蛋白及近缘序列,采用多款预测软件分别预测了其B细胞线性和构象型抗原表位,并分析了这些表位的保守性、适应性和进化特征。结果综合各种因素共预测出4个线性表位(表位A、B、C和D)和2个构象型表位(表位E和F)。表位C和位点41、157、186、187在进化过程中易发生突变,其余表位较为保守,其中表位D最保守;位点157受到强烈的正选择作用,它可能是H6N1病毒逃避宿主免疫系统攻击的一个关键位点。结论人易感H6N1禽流感病毒血凝素蛋白拥有5个保守的B细胞抗原表位(3个线性、2个构象型)和1个正选择作用位点,将为其疫苗的研制、致病机制的理解和病毒防治提供理论基础。     

Monoclonal Antibodies Raised against the Major Apple Allergen, Mal d 1, are Useful Tools for Epitope Studies

Mal d 1, the major apple allergen shows strong cross-reactivity with IgE specific for the major birch pollen allergen, Bet v 1, and is responsible for birch pollen related food allergy to apple. In contrast to other food and pollen allergens, only a few data on the B-cell epitopes of Mal d 1 are available. To obtain data on the antibody binding epitopes of Mal d 1 and to gain insights to the structures responsible for its B-cell cross-reactivity to Bet v 1, the binding characteristics were studied with 3 monoclonal antibodies (MAbs) raised against Mal d 1 and with patients' IgE directed against Mal d 1 and Bet v 1 by immunoblotting and ELISA. The different binding characteristics of these three MAbs indicated that the MAbs 1D6, 2B2 and 3F8 recognized different epitopes on the major apple allergen. MAb 2B2 cross-reacted with Bet v 1 on immunoblots, whereas 1D6 and 3F8 did not. Since 1D6 and 2B2 (but not 3F8) always competed with IgE from the same apple-allergic patients, 1D6 may be a useful tool for Mal d 1 epitope studies and 2B2 for an epitope that cross-reacts with IgE specific for Bet v 1.     

Cross-reactivity and epitope analysis of Pru a 1, the major cherry allergen.

A high percentage of birch pollen allergic patients experiences food hypersensivity after ingestion of fresh fruits and vegetables. The cross-reactivity of the major allergens of sweet cherry (Pru a 1), apple (Mal d 1), pear (Pyr c 1), celery tuber (Api g 1) and carrot (Dau c 1) is due to structural similarities which are reflected by high amino acid sequence identities with Bet v 1a, the major birch pollen allergen. Apart from a strong cross-reactivity to Bet v 1a, IgE inhibition experiments with Mal d 1, Pru a 1 and Api g 1 demonstrated the presence of common and different epitopes among the tested food allergens. Secondary structure prediction of all investigated allergens indicated the presence of almost identical structural elements. In particular, the 'P-loop' region is a common domain of the pollen related food allergens and of pathogenesis related proteins. To identify the IgE binding epitopes, five overlapping recombinant Pru a 1 fragments representing the entire amino acid sequence with lengths of approximately 60-120 residues were investigated. Weak IgE binding capacity was measured exclusively with Pru a IF4 (1-120) by immunoblotting, whereas none of the fragments showed allergenicity in the rat basophil leukaemia cell mediator release assay. Site-directed mutagenesis experiments with Pru a 1 revealed that amino acid S112 is critical for IgE binding of almost all patients sera tested. This reduced IgE binding was also observed with a single point mutant of Bet v 1a (S112P) and thus indicated serine 112 as an essential residue for preserving the structure of a cross-reactive IgE epitope. Moreover, two Pru a 1 mutants with an altered 'P-loop' region, showed a lowered IgE binding capacity for IgE from a subgroup of allergic patients. The investigation of essential features for preserving cross-reactive IgE-epitopes provides the structural basis for understanding the clinically observed cross-allergenicity between pollen and fruits. Moreover, non-anaphylactic allergen fragments or variants derived from the IgE-inducing pollen allergens may serve as useful tools for a new strategy of specific immunotherapy.     

Bet v 1142-156 is the dominant T-cell epitope of the major birch pollen allergen and important for cross-reactivity with Bet v 1-related food allergens

BACKGROUND: Individuals with birch pollen allergy frequently experience hypersensitivity reactions to certain foods, primarily because of IgE antibodies specific for the major birch pollen allergen Bet v 1 that cross-react with homologous food allergens. OBJECTIVE: We sought to characterize the major T-cell epitopes of Bet v 1 and to investigate their involvement in the cellular cross-reactivity with homologous food allergens. METHODS: T-cell epitope mapping of Bet v 1 was performed by testing Bet v 1-specific T-cell lines derived from 57 individuals with birch pollen allergy, with overlapping peptides representing the entire allergen. T-cell lines and T-cell clones were stimulated with Bet v 1-related major allergens from apple (Mal d 1), cherry (Pru av 1), hazelnut (Cor a 1), celery (Api g 1), carrot (Dau c 1), and soybean (Gly m 4) and with peptides deduced from the C-terminal amino acid sequences of these molecules. Results Bet v 1 142-156 , positioned in the highly conserved C-terminal region of Bet v 1, was identified as the major T-cell epitope recognized by 61% of individuals. Most T lymphocytes specific for Bet v 1 142-156 were activated by one or more homologous food proteins or the respective peptides, as indicated by proliferation and cytokine production. CONCLUSION: The major T-cell epitope of Bet v 1, Bet v 1 142-156 , plays an important role in the cellular cross-reactivity between this respiratory allergen and related food allergens. Thus T lymphocytes specific for Bet v 1 142-156 might be activated by various Bet v 1-related food allergens in vivo, even out of the pollen season.     

Two different profiles of peach allergy in the north of Spain

BACKGROUND: Peach allergy has two different patterns: central Europe with oral allergy syndrome (OAS) related to a primary sensitization to birch pollen Bet v 1 and profilins and southern Europe with mostly systemic symptoms, in many cases due to sensitization to lipid-transfer proteins. METHODS: Thirty peach-allergic patients with positive skin and food challenge tests and 29 control subjects were included. Skin prick tests (SPT) with inhalant allergens, commercial peach and apple extracts and native Pru p 3 were performed. In vitro specific immunoglobulin (Ig) E to grass pollen, birch pollen, peach, apple, rBet v 1, rBet v 2 and rPhl p 12 was determined by CAP, and rBet v 1, rMal d 1, rMal d 4, rMal d 3 and rPru p 3 using the ADVIA-Centaur platform. Basophil activation test (BAT) with commercial peach extract, commercial apple extract, nPru p 3, rMal d 3, rMal d 1 and rMal d 4 was also performed. RESULTS: Pru p 3 was the major allergen in the patient group from northern Spain. Sensitization to this allergen was found in 100% of the patients with systemic symptoms or contact urticaria. Only 60% of OAS patients were sensitized to Pru p 3, being all of them sensitized to profilins and 60% of them to allergens of the Bet v 1 family. Specific IgE determination and BAT using recombinant allergens (rPru p 3) show specificity and sensitivity values close to 100%. CONCLUSIONS: Most peach-allergic patients coming from the north of Spain present systemic symptoms after ingestion of peach, Pru p 3 being the main allergen. Patients with OAS present profilin-Bet v 1-related sensitization. Thus, in the north of Spain our patients show a mixed central-south Europe pattern with LTP-profilin-Bet v 1 sensitization depending on the symptoms presented. The use of natural and recombinant plant allergens, allows establishing the sensitization patterns to the different allergens studied.     

Molecular basis of allergic cross-reactivity between group 1 major allergens from birch and apple.

Patients allergic to birch pollen often also react with fruits and vegetables, such as apple. The major cause of cross-reactivity between birch and apple is biochemical and immunological similarity between the major allergens, Bet v 1 and Mal d 1, as demonstrated by serological and cellular immunoassays. In addition, birch pollen-specific therapeutic allergy vaccination has been shown to improve allergic symptoms caused by oral ingestion of apple. Detailed analysis of molecular surface areas based on the crystal structure of Bet v 1, and primary sequence alignment, identify potential epitopes for cross-reactive antibodies. Two or more conserved patches are identified when comparing Bet v 1 and Mal d 1, thus providing a molecular model for serological cross-reactivity involving more than one IgE-binding epitope. A minimum of two epitopes would be necessary for cross-linking of receptor bound IgE in functional histamine release assays and skin test. Individual amino acid substitutions, as occurring in isoallergenic variation, may, however, have a dramatic effect on epitope integrity if critical residues are affected. Thus, one area large enough to accommodate antibody-binding epitopes shared by all known Mal d 1 isoallergens and variants is identified, as well as areas shared by Bet v 1 and individual Mal d 1 isoallergens or variants. The occurrence of limited epitope coincidence between Bet v 1 and Mal d 1 is in agreement with the observation that some, but not all, birch pollen allergic patients react with apple, and that the epitope repertoire recognised by the IgE of the individual patients determines the degree of cross-reactivity.     

Successful sublingual immunotherapy with birch pollen has limited effects on concomitant food allergy to apple and the immune response to the Bet v 1 homolog Mal d 1

BACKGROUND: Cross-reactivity between the major birch pollen allergen, Bet v 1, and the apple protein, Mal d 1, frequently causes food allergy. OBJECTIVE: To investigate the effects of successful sublingual immunotherapy (SLIT) with birch pollen extract on apple allergy and the immune response to Bet v 1 and Mal d 1. METHODS: Before and after 1 year of SLIT, Bet v 1-sensitized patients with oral allergy syndrome to apple underwent nasal challenges with birch pollen and double-blind placebo-controlled food challenges with apple. Bet v 1-specific and Mal d 1-specific serum antibody levels and proliferation in PBMCs and allergen-specific T-cell lines (TCLs) were determined. Bet v 1-specific TCLs were mapped for T-cell epitopes. RESULTS: In 9 patients with improved nasal provocation scores to birch pollen, apple-induced oral allergy syndrome was not significantly reduced. Bet v 1-specific IgE and IgG(4) levels significantly increased. Bet v 1-specific T-cell responses to all epitopes and those cross-reactive with Mal d 1 significantly decreased. However, neither Mal d 1-specific IgE and IgG(4) levels nor Mal d 1-induced T-cell proliferation changed significantly. In contrast, Mal d 1-specific TCLs showed increased responses to Mal d 1 after 1 year of SLIT. CONCLUSION: This longitudinal study indicates that pollen SLIT does not efficiently alter the immune response to pollen-related food allergens, which may explain why pollen-associated food allergy is frequently not ameliorated by pollen immunotherapy even if respiratory symptoms significantly improve. CLINICAL IMPLICATIONS: SLIT with birch pollen may have no clinical effect on associated apple allergy.     

Cross-reactive and species-specific immunoglobulin E epitopes of plant profilins: an experimental and structure-based analysis

BACKGROUND: Profilins are cross-reactive plant allergens responsible for multiple pollen sensitization and pollen-associated food allergy. While it is assumed that profilins from different species are immunologically equivalent, some studies suggest partial or even lacking IgE cross-reactivity between certain profilins. OBJECTIVE: We aimed to obtain a semi-quantitative assessment of the contributions of conserved and species-specific epitopes to IgE binding of plant profilins. METHODS: We compared model structures of profilins from timothy, mugwort, celery and bell pepper with crystal structures of birch and latex profilins. We predicted potential conformational epitopes that consisted of contiguous patches of at least 20% surface-exposed residues. Celery and timothy profilins were purified from their natural sources, and profilins from birch, mugwort, bell pepper and latex were expressed in Escherichia coli. The structural integrity of all purified proteins was confirmed by circular dichroism spectroscopy. IgE ELISAs and ELISA inhibitions using sera from 22 profilin-sensitized allergic patients were carried out. RESULTS: Peptide backbone conformations of all six profilins were highly similar. Nine variable epitopes and two containing high proportions of conserved residues were predicted. IgE from all sera bound to all tested profilins and the amounts were highly correlated. However, IgE inhibition experiments revealed that up to 60% of total IgE binding was mediated by species-specific epitopes. The extent of cross-reactivity among profilins from timothy, birch, latex and celery was greater than cross-reactivity to mugwort and bell pepper profilins. This pattern was mirrored by sequence similarities among one of the predicted variable epitopes. Patients with IgE to cross-reactive epitopes displayed allergic reactions to a greater number of plant foods than patients having IgE directed to species-specific epitopes. CONCLUSION: The large extent of cross-reactivity among plant profilins justifies using a single profilin for diagnosis. However, the fine specificity of IgE directed to variable epitopes may influence the clinical manifestation of profilin sensitization.     

Mutational analysis of amino acid positions crucial for IgE-binding epitopes of the major apple (Malus domestica) allergen, Mal d 1

BACKGROUND: Individual amino acid residues of the major birch pollen allergen, Bet v 1, have been identified to be crucial for IgE recognition. The objective of the present study was to evaluate whether this concept was applicable for the Bet v 1-homologous apple allergen, Mal d 1. METHODS: A Mal d 1 five-point mutant was produced by PCR techniques, cloned into pMW 172 and expressed in Escherichia coli BL21(DE3) cells. To evaluate the allergenic properties of the engineered protein compared to Mal d 1 wild-type IgE immunoblotting, ELISA, peripheral blood monocytes proliferation assays, and skin prick tests were performed. RESULTS: The Mal d 1 mutant showed reduced capacity to bind specific IgE as compared to wild-ype Mal d 1 in in vitro assays in the majority of the sera tested. In ELISA, 10 out of 14 serum samples displayed an 88-30% decrease in IgE binding to Mal d 1 mutant compared to wild-type Mal d 1. Skin prick tests in apple-allergic patients (n = 2) confirmed the markedly decreased ability of the Mal d 1 mutant to induce allergic reactions in vivo. However, the relevant T cell epitopes were present in the mutated molecule according to peripheral blood mononuclear cell proliferation assays. CONCLUSIONS: Our findings suggest that it is possible to modulate the IgE-binding properties of allergens by single amino acid substitutions at crucial positions which might be useful for future immunotherapy of birch-pollen-associated food allergies which are not ameliorated by birch pollen immunotherapy.     

Lipid transfer proteins from fruit: cloning, expression and quantification

BACKGROUND: Lipid transfer proteins (LTP) are stable, potentially life-threatening allergens in fruits and many other vegetable foods. The aim of this study was to clone and express recombinant apple LTP (Mal d 3), as has previously been done for peach LTP (Pru p 3) and set up quantitative tests for measuring fruit LTPs. METHODS: cDNA for Mal d 3 and Pru p 3 was cloned, expressed in the yeast Pichia pastoris and the resulting proteins were purified via cation exchange chromatography. The immune reactivity of rMal d 3 was compared to nMal d 3 by RAST (inhibition), immunoblotting and basophil histamine release testing. To obtain monoclonal and monospecific polyclonal antibodies, mice and rabbits were immunized with purified nMal d 3. RESULTS: The deduced amino acid sequence of Mal d 3 was identical to the published sequence, Pru p 3 differed at two positions (S9A and S76H). The rMal d 3 had an IgE-binding potency and biological activity close to its natural counterpart. One sandwich ELISA selectively detecting apple LTP and another cross-reactive with cherry, nectarine and hazelnut LTP were developed. In addition, a competitive RIA was developed with polyclonal rabbit antiserum and labeled nMal d 3. CONCLUSION: rMal d 3 (as shown before for rPru p 3) may be a useful tool for application in component-resolved diagnosis of food allergy. Assays for the measurement of LTP will increase the traceability of this potentially dangerous allergen.     

Cross-reactivity within the profilin panallergen family investigated by comparison of recombinant profilins from pear (Pyr c 4), cherry (Pru av 4) and celery (Api g 4) with birch pollen profilin Bet v 2.

Profilin is a panallergen which is recognised by IgE from about 20% of birch pollen- and plant food-allergic patients. Little is known about epitope diversity among these homologous proteins, and about the correlation between IgE-cross-reactivity and allergenic reactivity. Plant food profilins from pear (Pyr c 4) and cherry (Pru av 4) were cloned by polymerase chain reaction and produced in Escherichia coli BL21. The profilins were purified as non-fusion proteins by affinity chromatography on poly-(L-proline)-Sepharose and characterized by immunoblotting, IgE-inhibition experiments and histamine release assays. The coding regions of the cDNA of pear and cherry profilin were identified as a 393 bp open reading frame. The deduced amino acid sequences showed high identities with birch pollen profilin Bet v 2 (76-83%) and other allergenic plant profilins. Pyr c 4 and Pru av 4 were investigated for their immunological properties in comparison with profilins from celery (Api g 4) and birch pollen (Bet v 2). Fourty-three of 49 patients (88%), preselected for an IgE-reactivity with Bet v 2 showed specific IgE-antibodies to the recombinant pear protein, 92% of the sera were positive with the recombinant cherry allergen and 80% of the sera were reactive with the celery protein. Inhibition experiments showed a strong cross-reactivity of IgE with profilins from plant food and birch pollen. However, IgE binding profiles also indicated the presence of epitope differences among related profilins. All investigated profilins, Pyr c 4, Pru av 4, Api g 4 and Bet v 2, presented almost identical allergenic properties in cellular mediator release tests. Therefore, cross-reactivities between related profilins may explain pollen-related allergy to food in a minority of patients. The nucleotide sequences reported have been submitted to the Genbank database under accession numbers AF129424 (Pyr c 4) and AF129425 (Pru av 4).