应用核酸适配子检测细胞因子的新方法-ELONA法

以人肿瘤坏死因子 (Humantumornecrosisfactor,hTNF α)特异性的核酸适配子为检测分子建立了酶联寡聚核苷酸吸附试验 (Enzyme linkedOligonucleotideassay ,ELONA)方法 ,用于hTNF α的检测。通过SELEX(SystematicEvolutionofLigandsbyExponentialEnrichment)方法从随机RNA库中筛选到与hTNF-α特异结合的RNA适配子。根据其序列 ,用体外转录方法合成生物素标记的RNA适配子 ,并对其进行了氨基修饰以增加其稳定性。以hTNF-α的单克隆抗体为捕获分子 ,生物素标记的hTNF-α特异性RNA适配子为检测分子建立了ELONA方法 ,并对这种检测方法的灵敏度、精密度和准确度等进行了分析。同时用ELONA和ELISA方法检测了正常人血清中的hTNF-α水平 ,并对检测结果进行比较。结果显示 ,ELONA方法的灵敏度为 100pg/mL ,具有较好的精密度和准确度。ELONA法的检测结果与ELISA法检测结果基本一致。该方法适用于血清、细胞培养上清等多种生物标本中各种细胞因子及其它蛋白的检测。     

定量检测猕猴血清中重组人源化抗狂犬病毒单克隆抗体间接ELISA法的建立

目的：建立定量检测血清中重组人源化抗狂犬病毒单克隆抗体（HuMabs）NM57的间接ELISA法,为药代动力学研究提供一种简单快速的方法。方法：采用狂犬病毒糖蛋白包被酶标板、HRP标记的IgG-Fc段为标记抗体,建立定量检测HuMabsNM57的间接ELISA法,并对其特异性、灵敏度、精密度及准确度进行检测。结果：间接ELISA法检测HuMabsNM57的灵敏度为5ng／mL,组内及组间精密度分别为2．6％-6．0％、8．5％-11．3％。结论：建立了灵敏度高、特异性强的检测HuMabs NM57的间接ELISA法,精密度及准确度均符合药代动力学要求,可用于猕猴及人血清中HuMabsNM57的检测。     

定量检测重组抗白介素6受体人源化单克隆抗体HS628的ELISA方法的建立及确证

目的:建立一种灵敏、特异、快速、经济的ELISA方法,用于检测食蟹猴血清中重组抗白介素6受体人源化单克隆抗体HS628的含量。方法:对ELISA与生物素-亲和素ELISA(BA-ELISA)方法进行比较,最终采用BA-ELISA法对HS628进行定量。包被抗体为羊抗人Ig G单抗,以生物素标记的重组白介素6受体作为检测抗原,以HRP标记的链霉亲和素作为放大剂,最终用单组分显色液(TMB)显色。结果:建立了特异性检测HS628的ELISA方法并完成方法学确证,该方法的线性范围为1.64~400 ng/m L,灵敏度为1.64 ng/m L,精密度、准确度、回收率及稳定性符合要求,与对照品校正标准曲线吻合。结论:用建立的ELISA方法测定猴血清中HS628的含量能满足新生物制药临床前药代动力学研究指导原则要求,可用于HS628的检测。     

Nodal检测双单抗夹心ELISA法建立及应用

现已证实,Nodal参与了肿瘤恶性生物学过程,但对其高敏感检测法尚未建立。采用基因工程表达人源Nodal作为抗原免疫BALB/c小鼠,通过经典PEG诱导的细胞融合技术筛选出针对Nodal的特异性单克隆抗体7株。夹心ELISA确证7株抗体组成了15种可配对的抗体对。经筛选后选取抗体对AF12-DG5建立标准化夹心ELISA法,结合生物素-亲和素检测系统,DG5抗体标记生物素,采用链亲和素与辣根过氧化物酶标记的生物素(HRP-Biotin)按质量比4∶1预先混合孵育的ABC混合物进行检测,以提高ELISA法的灵敏度。棋盘滴定确定抗体工作最佳浓度为:捕获抗体(AF12)2μg/ml,检测抗体(生物素化DG5)2μg/ml。此条件下的夹心ELISA法线性范围为0~3 000pg/ml,检测限为68pg/ml,平均回收率为99.6%,精密度准确度良好。以正常人血清作为阴性对照,使用该夹心ELISA法测定结直肠癌、鼻咽癌和胆囊癌患者血清,发现三种肿瘤患者血清与正常人血清中的Nodal浓度均存在明显的统计学差异,可作为临床使用参考。     

重组人鼠嵌合抗CD20单克隆抗体免疫原性检测方法的建立

目的:建立一种灵敏、特异、操作简单的ELISA方法,用于检测食蟹猴血清中抗CD20单克隆抗体的免疫原性。方法:首先采用桥连ELISA法对抗药物抗体(ADA)进行定性筛选,以抗CD20单克隆抗体作为包被抗体,以生物素标记的抗CD20单克隆抗体作为检测抗体,二者共同结合血清中存在的ADA,以D450/560nm值超过临界值作为阳性判断标准;初筛为阳性的样本采用免疫清除法进一步确证,并同时进行免疫交叉试验考察ADA对供试品和原研对照品的免疫反应有无差异。结果:建立了检测ADA的筛选方法和确证方法,确定了检测的临界值和归一化因子,血清中抗药物抗体的检测灵敏度达3.5 ng/m L,批内/批间精密度介于3.1%~7.4%,准确度介于-1.2%~9.5%;食蟹猴连续给药后,部分个体产生特异性抗体,且抗体滴度随时间延长而增高。结论:建立的ADA筛选方法和确证方法可用于毒性试验的免疫原性检测;动物给药剂量对抗体的产生有较大影响,低剂量连续给药更易诱发特异性抗体产生。     

重组人血清白蛋白抗体检测方法的建立及确证

目的：建立一种高灵敏度、高特异性、操作简单快捷、通量高的重组人血清白蛋白（rHSA）抗体检测方法。方法：采用桥连ELISA法,即将rHSA包被于96孔板,加入待测血样及阳性对照,用辣根过氧化物酶标记的rHSA检测,显色读取D_450nm/D_570nm值：用此方法确定临界值、方法灵敏度、精密度、血药浓度对检测方法的影响,再以免疫清除法进行确证。结果：通过桥连ELISA法确定临界值为0．0492,方法灵敏度为352ng／mL,方法板间、板内精密度均小于20％,且血药中的rHSA浓度为20μg／mL时不影响抗体的检测;经免疫清除法可将假阳性样本排除,从而提高了方法的特异性．结论：建立的方法可以准确、快速地检测出rHSA的特异性抗体。     

用生物素-亲和素ELISA法检测人胚肺二倍体细胞培养的甲型肝炎病毒抗原

利用生物素-亲和素生物放大系统的原理,建立了新的检测细胞培养的甲型肝炎病毒抗原的方法。用生物素标记的抗甲肝IgG,与免疫偶联于固相的甲肝抗原作用,然后用亲和素-生物素辣根酶复合物(ABPC)与生物素化的IgG偶合,邻苯二胺(OPD)显色。该法在检测甲肝抗原中获得满意结果,灵敏度比普通ELISA法提高约10倍,非特异性显著降低。该法可进一步发展成为一种高特异性的,灵敏的甲肝临床诊断和流行病学调查的技术。     

两种甲型肝炎病毒抗原快速检测方法的建立

目的建立两种甲型肝炎病毒抗原(HAV-Ag)检测试剂盒,并对其检测效果进行评价。方法生物素标记甲型肝炎病毒抗体(HAV-Ab)与辣根过氧化物酶标记亲和素联合应用建立甲型肝炎病毒抗原BA-ELISA检测法;同时使用辣根过氧化物酶标记HAV-Ab作放大系统建立双抗体夹心甲型肝炎病毒抗原ELISA检测试剂,对比两种检测方法的特异性、灵敏度及实际应用效果。结果用生物素标记甲型肝炎病毒抗体-辣根过氧化物酶标记亲和素作放大系统建立的甲型肝炎病毒抗原BA-ELISA检测法,较双抗体夹心ELISA检测方法灵敏度高1～2个稀释度;两种检测法均对10余种病毒无交叉,P/N值BA-ELISA检测法较高。结论甲型肝炎病毒抗原BA-ELISA检测法是一种灵敏度高,特异性好,方便快捷的检测方法,可广泛应用于甲型肝炎病毒研究及临床检测中。而甲型肝炎病毒抗原双抗体夹心ELISA检测法,检测灵敏度适中,操作简单,更适用于甲肝疫苗生产检定。     

结核分枝杆菌抗体双抗原夹心ELISA检测方法的建立及初步应用

目的:建立2种结核分枝杆菌(Mtb)抗体的双抗原夹心ELISA检测方法,并初步评价其在Mtb血清学临床辅助诊断中的应用价值。方法:采用Mtb融合抗原38k D+ESAT6+CFP10作为包被抗原,分别以辣根过氧化物酶(HRP)和生物素(Bio)标记的38k D+ESAT6+CFP10作为标记抗原,建立2种Mtb双抗原夹心ELISA法,即HRP-ELISA法和Bio-ELISA法;采用所建立的2种方法对结核患者和健康对照血清进行检测。结果:经过一系列的反应条件优化,确定HRP-ELISA法和Bio-ELISA法的最佳抗原包被浓度分别为2、0.25μg/m L,最适加样量均为100μL血清原液,最佳标记抗原稀释率分别为1∶500、1∶2000,检测的灵敏度分别为43.66%、52.11%,特异性均为100%。结论:建立了2种Mtb双抗原夹心ELISA法,它们均适用于Mtb血清学的临床辅助诊断。     

双抗体夹心ELISA检测HIV-1 gp41抗原方法的建立

目的:建立检测HIV-1gp41抗原的双抗体夹心ELISA,并探讨其临床应用的可行性。方法:用饱和硫酸铵(SAS)纯化抗HIV-1gp41-5单克隆抗体(mAb),用HRP标记后建立双抗体夹心ELISA法,对其灵敏度及特异性进行检测,并用该方法对40份HIV-1阳性血清进行了检测。结果:用mAbE12(5μg/mL)为包被抗体,2H6为酶标记抗体(1∶900)建立了双抗体夹心ELISA法,检测gp41-5多肽的灵敏度是100pg/mL。对HIV-1阳性血清中gp41抗原的检出率为67.5%(27/40)。结论:建立了特异性强、灵敏度良好的检测HIV-1gp41抗原的双抗体夹心ELISA法。     

Aptamers as functional nucleic acids:<Emphasis Type="Italic">In vitro</Emphasis> selection and biotechnological applications

Aptamers are functional nucleic acids that can specially bind to proteins, peptides, amino acids, nucleotides, drugs, vitamins and other organic and inorganic compounds. The aptamers are identified from random DNA or RNA libraries by a SELEX (systematic evolution of ligands by exponential amplification) process. As aptamers have the advantage, and potential ability to be released from the limitations of antibodies, they are attractive to a wide range of therapeutic and diagnostic applications. Aptamers, with a high-affinity and specificity, could fulfil molecular the recognition needs of various fields in biotechnology. In this work, we reviewed some aptamer selection techniques, properties, medical applications of their molecules and their biotechnological applications, such as ELONA (enzyme linked oligonucleotide assay), flow cytometry, biosensors, electrophoresis, chromatography and microarrays.     

Selection and Identification of Aptamers Against B Cell Activating Factor

Systemic lupus erythematosus (SLE) is the most common autoimmune disease in China. B cell activating factor (BAFF) is an important target for the treatment and detection of SLE. It is of great significance to develop novel molecular recognition elements with high affinity for BAFF. In this study, artificial nucleic acid aptamers against BAFF were screened from a 78 nt single-stranded DNA random library by systematic evolution of ligands exponential enrichment (SELEX) in vitro based on several selection and amplification steps. Through ten rounds of selection, the aptamers with high specificity and affinity for BAFF were identified. After high-throughput sequencing, several aptamers were selected and further examined for binding affinity and specificity. The investigation by dot blotting, Eastern blotting analyses and enzyme-linked oligonucleotide assay (ELONA) showed that the aptamers Apt 7 and Apt 12 with dissociation constants of 241.00±19.75 nmol/L and 413.51±46.94 nmol/L were able to recognize BAFF specifically. After molecular docking analysis, Apt 7 was truncated to Apt 7～1, and the dissociation constant was 192.10±28.61 nmol/L. A sandwich ELONA using Apt 7～1 and BAFF antibodies was established to detect BAFF. The detection limit was estimated to be 0.227 nmol/L. This study provides new molecular recognition elements for the detection of BAFF and the study of antagonists.     

Aptamers: versatile probes for flow cytometry

Aptamers are nucleic acid oligomers with distinct conformational shapes that allow them to bind targets with high affinity and specificity. Aptamers are selected from a random oligonucleotide library by their capability to bind a certain molecular target. A variety of targets ranging from small molecules like amino acids to complex targets and whole cells have been used to select aptamers. These characteristics and the ability to create specific aptamers against virtually any cell type in a process termed “systematic evolution by exponential enrichment” make them interesting tools for flow cytometry. In this contribution, we review the application of aptamers as probes for flow cytometry, especially cell-phenotyping and detection of various cancer cell lines and virus-infected cells and pathogens. We also discuss the potential of aptamers combined with nanoparticles such as quantum dots for the generation of new multivalent detector molecules with enhanced affinity and sensitivity. With regard to recent advancements in aptamer selection and the decreasing costs for oligonucleotide synthesis, aptamers may rise as potent competitors for antibodies as molecular probes in flow cytometry.     

Selection of DNA aptamers that bind to influenza A viruses with high affinity and broad subtype specificity

Many cases of influenza are reported worldwide every year. The influenza virus often acquires new antigenicity, which is known as antigenic shift; this results in the emergence of new virus strains, for which preexisting immunity is not found in the population resulting in influenza pandemics. In the event a new strain emerges, diagnostic tools must be developed rapidly to detect the novel influenza strain. The generation of high affinity antibodies is costly and takes time; therefore, an alternative detection system, aptamer detection, provides a viable alternative to antibodies as a diagnostic tool. In this study, we developed DNA aptamers that bind to HA1 proteins of multiple influenza A virus subtypes by the SELEX procedure. To evaluate the binding properties of these aptamers using colorimetric methods, we developed a novel aptamer-based sandwich detection method employing our newly identified aptamers. This novel sandwich enzyme-linked aptamer assay successfully detected the H5N1, H1N1, and H3N2 subtypes of influenza A virus with almost equal sensitivities. These findings suggest that our aptamers are attractive candidates for use as simple and sensitive diagnostic tools that need sandwich system for detecting the influenza A virus with broad subtype specificities.     

RNA Aptamer That Specifically Binds to Mycolactone and Serves as a Diagnostic Tool for Diagnosis of Buruli Ulcer

BackgroundBuruli ulcer (BU) is a subcutaneous skin disease listed among the neglected tropical diseases by the World Health Organization (WHO). Early case detection and management is very important to reduce morbidity and the accompanied characteristic disfiguring nature of BU. Since diagnosis based on clinical evidence can lead to misdiagnosis, microbiological confirmation is essential to reduce abuse of drugs; since the anti-mycobacterial drugs are also used for TB treatment. The current WHO gold standard PCR method is expensive, requires infrastructure and expertise are usually not available at the peripheral centers where BU cases are managed. Thus one of the main research agendas is to develop methods that can be applied at the point of care. In this study we selected aptamers, which are emerging novel class of detection molecules, for detecting mycolactone, the first to be conducted in a BUD endemic country.MethodsAptamers that bind to mycolactone were isolated by the SELEX process. To measure their affinity and specificity to mycolactone, the selected aptamers were screened by means of isothermal titration calorimetry (ITC) and an enzyme-linked oligonucleotide assay (ELONA). Selected aptamers were assessed by ELONA using swab samples from forty-one suspected BU patients with IS2404 PCR and culture as standard methods. ROC analysis was used to evaluate their accuracy and cutoff-points.ResultsFive out of the nine selected aptamers bound significantly (p< 0.05) to mycolactone, of these, three were able to distinguish between mycolactone producing mycobacteria, M. marinum ({"type":"entrez-nucleotide","attrs":{"text":"CC240299","term_id":"30566962","term_text":"CC240299"}}CC240299, Israel) and other bacteria whilst two others also bounded significantly to Mycobacterium smegmatis. Their dissociation constants were in the micro-molar range. At 95% confidence interval, the ROC curve analysis among the aptamers at OD450 ranged from 0.5–0.7. Using this cut-off for the ELONA assay, the aptamers had 100% specificity and sensitivity between 0.0% and 50.0%. The most promising aptamer, Apt-3683 showed a discernible cleavage difference relative to the non-specific autocatalysis over a 3-minute time course.ConclusionThis preliminary proof-of-concept indicates that diagnosis of BUD with RNA aptamers is feasible and can be used as point of care upon incorporation into a diagnostic platform.     

In vitro Selection of High Affinity DNA and RNA Aptamers that Detect Hepatitis C Virus Core Protein of Genotypes 1 to 4 and Inhibit Virus Production in Cell Culture

Hepatitis C virus (HCV) core is a highly conserved and multifunctional protein that forms the viral capsid, making it an attractive target for HCV detection and inhibition. Aptamers are in vitro selected, single-stranded nucleic acids (RNA or ssDNA) with growing applicability in viral diagnostics and therapy. We have carried out DNA and RNA in vitro selection against six different variants of HCV core protein: two versions of the full-length protein of genotype 1, and the hydrophilic domain of genotypes 1 to 4. The aptamer populations obtained were analyzed by means of Ultra-Deep Sequencing (UDS), the most abundant sequences were identified and a number of highly represented sequence motifs were unveiled. Affinity (measured as the dissociation constant, Kd) of the most abundant DNA and RNA aptamers were quantified using Enzyme-Linked OligoNucleotide Assay (ELONA)-based methods. Some aptamers with nanomolar or subnanomolar Kd values (as low as 0.4 nM) were the common outcome of DNA and RNA selections against different HCV core variants. They were tested in sandwich and competitive biosensor assays, reaching a limit of detection for HCV core of 2 pM. Additionally, the two most prevalent and high affinity aptamers were assayed in Huh-7.5 reporter cell lines infected with HCV, where they decreased both the viral progeny titer and the extracellular viral RNA level, while increasing the amount of intracellular viral RNA. Our results suggest that these aptamers inhibit HCV capsid assembly and virion formation, thus making them good candidate molecules for the design of novel therapeutic approaches for hepatitis C.     

适配体的筛选及在生命分析化学中的应用

指数级富集的配体系统进化技术（SELEX）是近年来发展的获得能够与靶分子高特异性和高亲力结合的寡核苷酸序列（适配体）的筛选技术。目前多种靶分子的适配体如蛋白或小分子,都已经通过SELEX技术筛选获得,使适配体在蛋白质组研究、临床医学、药物研发及基因调控等领域已经成为重要的研究工具。本文就近几年适配体的筛选技术及在生命分析化学中的应用发展方面进行了综述。     

Selection and Application of ssDNA Aptamers to Detect Active TB from Sputum Samples

Background

Despite the enormous global burden of tuberculosis (TB), conventional approaches to diagnosis continue to rely on tests that have major drawbacks. The improvement of TB diagnostics relies, not only on good biomarkers, but also upon accurate detection methodologies. The 10-kDa culture filtrate protein (CFP-10) and the 6-kDa early secreted antigen target (ESAT-6) are potent T-cell antigens that are recognised by over 70% of TB patients. Aptamers, a novel sensitive and specific class of detection molecules, has hitherto, not been raised to these relatively TB-specific antigens.

Methods

DNA aptamers that bind to the CFP-10.ESAT-6 heterodimer were isolated. To assess their affinity and specificity to the heterodimer, aptamers were screened using an enzyme-linked oligonucleotide assay (ELONA). One suitable aptamer was evaluated by ELONA using sputum samples obtained from 20 TB patients and 48 control patients (those with latent TB infection, symptomatic non TB patients, and healthy laboratory volunteers). Culture positivity for Mycobacterium tuberculosis (Mtb) served as the reference standard. Accuracy and cut-points were evaluated using ROC curve analysis.

Results

Twenty-four out of the 66 aptamers that were isolated bound significantly (p<0.05) to the CFP-10.ESAT-6 heterodimer and six were further evaluated. Their dissociation constant (K_D) values were in the nanomolar range. One aptamer, designated CSIR 2.11, was evaluated using sputum samples. CSIR 2.11 had sensitivity and specificity of 100% and 68.75% using Youden’s index and 35% and 95%, respectively, using a rule-in cut-point.

Conclusion

This preliminary proof-of-concept study suggests that a diagnosis of active TB using anti-CFP-10.ESAT-6 aptamers applied to human sputum samples is feasible.     

DNA Aptamers Selectively Target Leishmania infantum H2A Protein

Parasites of the genus Leishmania produce leishmaniasis which affects millions people around the world. Understanding the molecular characteristics of the parasite can increase the knowledge about the mechanisms underlying disease development and progression. Thus, the study of the molecular features of histones has been considered of particular interest because Leishmania does not condense the chromatin during mitosis and, consequently, a different role for these proteins in the biology of the parasite can be expected. Furthermore, the sequence divergences in the amino and in the carboxy-terminal domains of the kinetoplastid core histones convert them in potential diagnostic and/or therapeutics targets. Aptamers are oligonucleotide ligands that are selected in vitro by their affinity and specificity for the target as a consequence of the particular tertiary structure that they are able to acquire depending on their sequence. Development of high-affinity molecules with the ability to recognize specifically Leishmania histones is essential for the progress of this kind of study. Two aptamers which specifically recognize Leishmania infantum H2A histone were cloned from a previously obtained ssDNA enriched population. These aptamers were sequenced and subjected to an in silico analysis. ELONA, slot blot and Western blot were performed to establish aptamer affinity and specificity for LiH2A histone and ELONA assays using peptides corresponding to overlapped sequences of LiH2A were made mapping the aptamers:LiH2A interaction. As “proofs of concept”, aptamers were used to determine the number of parasites in an ELONA platform and to purify LiH2A from complex mixtures. The aptamers showed different secondary structures among them; however, both of them were able to recognize the same peptides located in a side of the protein. In addition, we demonstrate that these aptamers are useful for LiH2A identification and also may be of potential application as diagnostic system and as a laboratory tool with purification purpose.     

Isolation of a new ssDNA aptamer against staphylococcal enterotoxin B based on CNBr‐activated sepharose‐4B affinity chromatography

Staphylococcus aureus are potent human pathogens possessing arsenal of virulence factors. Staphylococcal food poisoning (SFP) and respiratory infections mediated by staphylococcal enterotoxin B (SEB) are common clinical manifestations. Many diagnostic techniques are based on serological detection and quantification of SEB in different food and clinical samples. Aptamers are known as new therapeutic and detection tools which are available in different ssDNA, dsDNA and protein structures. In this study, we used a new set of ssDNA aptamers against SEB. The methods used included preparation of a dsDNA library using standard SEB protein as the target analyte, affinity chromatography matrix in microfuge tubes, SELEX procedures to isolate specific ssDNA‐aptamer as an affinity ligand, aptamer purification using ethanol precipitation method, affinity binding assay using ELISA, aptamer cloning and specificity test. Among 12 readable sequences, three of them were selected as the most appropriate aptamer because of their affinity and specificity to SEB. This study presents a new set of ssDNA aptamer with favorable selectivity to SEB through 12 rounds of SELEX. Selected aptamers were used to detect SEB in infected serum samples. Results showed that SEB c1 aptamer (2 µg SEB/100 nM aptamer) had favorable specificity to SEB (k_d = 2.3 × 10^?11). In conclusion, aptamers can be considered as useful tools for detecting and evaluating SEB. The results showed that affinity chromatography was an affordable assay with acceptable accuracy to isolate sensitive and selective novel aptamers. Copyright © 2016 John Wiley & Sons, Ltd.