Name: development and validation of an ultrasensitive single molecule array digital enzyme-linked immunosorbent assay for human interferon-α
Uploaded: 2018-06-14T14:00:00.000+00:00
Duration: 8 min 26 s
Description: Watch this Scientific Journal Video about Development and Validation of an Ultrasensitive Single Molecule Array Digital Enzyme-linked Immunosorbent Assay for Human Interferon-Î± at JoVE.com

DD 和 YJC 承认来自情报局的支持 (项目 IFNX, 不。CE17001002) 和 ImmunoQure AG 提供单克隆抗体。我们感谢穆尼耶, Nathalia 贝伦, 克里斯汀 Bodemer, 亚历克斯贝洛, 伊莎贝尔 Melki, 皮埃尔卡尔捷提供临床样本。YJC 承认欧洲研究理事会 (GA 309449: YJC 的研究), 以及国家研究机构 (法国) 在 "未来投资" 项目下管理的国家补贴, 其参考 ANR-10-IAHU-01。

1. 抗体的选择
<ol><li>在开始之前, 该协议审查所有关键步骤 (表 1) 和选择最佳抗体。 注意: 对于这个协议高亲和力抗干扰素α抗体-IC50 在表 2中所描述的选择。优先选择对传统 ELISA 有效的配对。</li>
</ol>2. 对顺磁珠捕获抗体的共轭和不同浓度的测试
注: 在抗体共轭过程中, 始终保持珠共轭缓冲 (BCB) 和珠洗涤缓冲 (BWB) 在冰上。
<ol><li>
捕获抗体缓冲交换
	<ol>
<li>以初始数量的抗干扰素α抗体 A 测试3不同的珠动词比 (0.038 毫克/毫升, 0.075 毫克/毫升, 0.3 毫克/毫升)。 注: 低抗体涂层浓度可以是有益的, 如果检测提出了高背景信号。在缓冲交换过程中, 初始抗体数量应占估计损失的30%。根据制造商的指示和为了减少最初的背景, 测试了0.05 毫克/毫升, 0.1 毫克/毫升和0.3 毫克/毫升的浓度, 虽然这些确切的值往往没有得到由于上述可变损失的缓冲交换过程。</li>
		<li>将所需的抗体量添加到过滤器列连同 BCB, 最多可达500µL。</li>
		<li>离心机在 > 1万 x g 的列5分钟, 并丢弃流经。</li>
		<li>通过在 > 1万 x g 处添加450µL 的总容积, 然后将其 BCB 为5分钟, 并将其丢弃, 然后将该列清洗两次。</li>
		<li>将含有抗体的过滤器列放置在一个干净的离心管中倒置--该柱面的开口部分朝向新管的内侧, 离心机在 800 x g 处为1分钟。 注意: 此步骤将允许收集已清除的抗体。此步骤不需要缓冲区添加。</li>
		<li>用50µL BCB 和离心机在 800 x g 处冲洗膜, 2.1.5 1 分钟。</li>
		<li>用低容积分光光度计测定抗体浓度。</li>
		<li>添加 BCB 以达到所需的抗体浓度并记下最终音量。 注: 200 µL 的体积将用于描述协议的其余部分, 这个卷被称为2卷 (2V)。所有以下试剂卷将相应地被适应。</li>
		<li>漩涡, 并保持冰。</li>
	</ol>
</li>
	<li>
顺磁珠制备
	<ol>
<li>将 2.8 x 108珠子 (100 µL = 1V) 转移到离心管中。 注: 珠子的体积取决于2.1.8 获得的最终体积。</li>
		<li>脉冲旋转, 放入磁选机1分钟, 丢弃稀释剂, 从磁铁中取出。</li>
		<li>加入2V 的 BWB 和涡旋5秒。</li>
		<li>重复2.2.2 和2.2.3 两次, BWB 和两次 BCB。</li>
		<li>对于1V 的珠子添加190µL BCB, 涡 5 s, 脉冲旋转, 并储存在冰上洗净珠。</li>
	</ol>
</li>
	<li>
珠活化
	<ol>
<li>将1毫升的冷 BCB 加入10毫克的 1-乙基 3-(3-dimethylaminopropyl) carbodiimide 盐酸盐 (EDC) 和涡流, 直到溶液是均匀的。</li>
		<li>对于1V 的珠子添加10µL 冷稀释的 EDC 到洗涤珠, 漩涡, 并保持在一个振动筛在 1000 rpm 30 分钟的室温。 注: 由于在水溶液中的不稳定性, 应尽快完成对小珠的制备和添加。同时, 由于该系统具有极强的反应性, 所以在添加前必须有一个均匀的珠悬浮, 以防止异质珠的活化。添加后, 珠子必须保持悬浮。</li>
	</ol>
</li>
	<li>
抗体的珠共轭
	<ol>
<li>涡旋和脉冲旋转活化珠。现在把珠子放在磁选机里1分钟, 扔掉 BCB 上清, 然后把管子从磁铁上取下。</li>
		<li>用2V 的 BCB 把珠子洗净。涡流, 脉冲旋转, 并把磁选机1分钟。然后丢弃 BCB 缓冲器, 从磁铁中取出珠子。</li>
		<li>快速添加冷, 缓冲交换200µL (2V) 抗体的活化珠。</li>
		<li>涡流, 并保持在室温下的振动筛2小时。</li>
	</ol>
</li>
	<li>
珠封和最终清理
	<ol>
<li>脉冲旋转的抗体涂层珠悬浮, 放在磁分离器1分钟, 转移到新的管, 并测量浓度与低容积分光光度计。 注意: 这一步将提供有关珠子是否饱和的信息--任何高于零的值都会显示珠饱和度--因为检测到无法绑定到珠子的可溶性抗体将是可测量的。</li>
		<li>从磁铁中取出共轭珠, 加入2V 的 BWB, 涡流为5秒, 脉冲旋转, 并放入磁选机中1分钟。</li>
		<li>用低容积分光光度计将上清液转移到新管中, 测量浓度。 注意: 此步骤将提供有关抗体是否稳定地固定在珠子上的信息。在这上清液中检测到的抗体浓度将表明从珠子中分离出的抗体, 这种现象经常发生。即使很少的捕获抗体仍然附着在珠子上, 这种化验也常常奏效。</li>
		<li>从磁铁中取出共轭珠, 加入2V 的 BWB, 涡流为5秒, 脉冲旋转, 并放入磁选机中1分钟。</li>
		<li>从磁铁中取下共轭珠, 在室温下加入2V 的珠挡缓冲器, 涡旋5秒, 在振动筛中孵化30分钟。</li>
		<li>用 2V, 一次与 BWS, 和2x 与珠稀释剂缓冲 (丢弃所有上清液) 清洗抗体涂层和被阻拦的珠子3x。</li>
		<li>将涂层和被堵塞的珠子贮存在4°c 中, 直到使用2V 的珠稀释剂缓冲。 注: 在使用前, 必须使用磁选机用 250 x 珠 volume/20, 用探测器/样品稀释剂清洗一次珠子。</li>
	</ol>
</li>
</ol>3. 检测抗体 Biotinylation
<ol><li>
检测抗体缓冲交换
	<ol>
<li>服用260µg 的两个抗干扰素抗体克隆。 注意: 这在缓冲交换过程中考虑到30% 的损失, 并允许测试两种不同的生物素/抗体比值。</li>
		<li>使用 Biotinylation 反应缓冲器 (BRB) 代替 BCB 进行2.1。</li>
		<li>测量体积和抗体浓度, 调整体积以获得最终浓度为1毫克/毫升。 注: 这是一个建议的开始浓度, 但它可以优化, 如果化验没有达到所需的灵敏度。</li>
	</ol>
</li>
	<li>
检测抗体 Biotinylation
	<ol>
<li>把 N-hydroxysuccinimide-polyethylene-glycol4-biotin (NHS-PEG4-Biotin) 到室温和并用重悬共400µL 蒸馏水, 达到3.4 毫米的浓度。</li>
		<li>确定生物素: 抗体比测试和混合检测抗体和稀释的生物素相应地 (60:1 比率等于100µL 检测抗体和4.5 µL 生物素)。 注: 开始, 测试30:1 和60:1 比率。</li>
		<li>在室温下, 将抗体-生物素混合, 脉冲旋转和孵育30分钟。 注: 不需要摇动。</li>
	</ol>
</li>
	<li>
生物素化检测抗体纯化
	<ol>
<li>将生物素化抗体转移到新的过滤器中, 并进行 2.1, 执行3洗涤步骤与 BRB (400, 450 和450µL) 和最终收集。</li>
		<li>测量纯化, 生物素化检测抗体的体积和浓度, 贮存在4摄氏度, 直到使用。</li>
	</ol>
</li>
</ol>4. 检测优化
注: 使用单分子阵列分析仪软件的自制配置30。 单分子阵列分析仪由软件控制, 允许运行化验标准化, 执行样品 quantifications, 修改外部参数 (珠, 探测器, SBG, RGP 浓度; 样品稀释...) 和内部参数 (步骤数, 孵化时间...), 以达到最佳的化验条件, 也可以用来计算结果 (背景, LOD, 数量)。对于单分子阵列分析仪的设置和计算每轮优化所需的试剂量, 请参阅制造商的说明。使用2步配置执行第一轮优化。
<ol><li>在两种构型中检测捕获抗体-共轭珠和生物素化检测抗体的组合。<ol>
<li>测试组合三不同的抗干扰素α A 捕获抗体浓度与两种不同的抗干扰素α B biotinylation 比作为检测和捕获抗体, 反之亦然 (图 1) 通过选择适当的条件在分析器软件。</li>
		<li>选择最敏感的组合, 即提供最低 LOD 的条件, 并使用它进行进一步的步骤 注:图 1显示了0.3 毫克/毫升抗干扰素α a 抗体珠浓度和生物素: 抗体比值30:1 与抗干扰素α B 抗体导致最高灵敏度, 这证明了 LOD 11.6 的成品/毫升。(见补充表 1)。此组合将用于所有未来步骤。注意, 在任何一轮优化之前, 这一特定的检测都达到了极大的灵敏度。</li>
	</ol>
</li>
</ol><img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57421/57421fig1.jpg"> 图 1: 选择抗体定位, 捕获抗体浓度的珠子和 biotinylation 比.用抗干扰素α A 作为捕获抗体和抗干扰素α B 作为检测抗体 (a), 对两种可能的不同构型进行了测试, 反之亦然 (B)。IFNα-2c 被用作抗原。不同的捕获抗体浓度和生物素: 抗体 (B: A) 比率也测试两种配置。虚线显示 LOD 的最佳状态;抗干扰素α A 0.3 毫克/毫升作为捕获和抗干扰素α B 生物素: 探测器抗体比为 30 (LOD = 11.6 毫克/毫升对应的 AEB 值 0.017265)。使用了2步配置。生物素: 抗体 (B: A).<a href="/files/ftp_upload/57421/57421fig1large.jpg" target="_blank">请点击这里查看这个数字的大版本.</a>
<ol start="2"><li>比较2与3步配置。 注: 在3步的配置中, 有三种不同的孵化步骤, 一个与捕获抗体, 一个与检测抗体和最后第三个 SBG 酶标记。然而, 在2步的配置中, 捕获和检测抗体同时与感兴趣的分析物一起孵化。<ol>
<li>运行单分子阵列分析仪与捕获和检测抗体浓度和比率从4.1.2 选择2和3步配置预先配置在分析仪, 按照制造商的指令30。</li>
		<li>选择允许最高灵敏度的配置, 并将其保留为将来的步骤 注: 如图 2和辅助表 2所示, 2 步配置给每个浓度测试提供了稍微高的灵敏度和信号/背景比。因此, 为将来的步骤保留了2步的配置。</li>
	</ol>
</li>
</ol><img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57421/57421fig2.jpg"> 图 2: 2 vs 3 步配置比较.使用0.3 毫克/毫升抗干扰素α抗体作为捕获和抗干扰素α B 作为检测抗体的30生物素: 抗体比, 对2和3步构型进行了评估。IFNα-2c 被用作抗原。在3步条件设置中, 有三种不同的孵化步骤, 一个与捕获抗体, 一个与检测抗体和最后第三个 SBG 酶标签。然而, 在2步的配置中, 捕获和检测抗体同时与感兴趣的分析物一起孵化。<a href="/files/ftp_upload/57421/57421fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<ol start="3"><li>检测抗体与 SBG 浓度优化<ol>
<li>测试三不同浓度的检测抗体 (0.1, 0.3, 0.6 µg/毫升) 连同三不同浓度的 SBG (50, 150, 和 250 pM) 如上文所述30。</li>
		<li>选择具有最高灵敏度的浓度, 并保持它们的未来步骤。 注:图 3显示探测器0.3 µg/mL 和 SBG 150 pM 是显示最佳 LOD 的条件。这些条件也给出了低背景水平和中等振幅, 这种行为产生良好的标准偏差 (SD) 值 (辅助表 3)。典型的浓度范围在 0.1-1 µg/毫升之间的检测抗体和 50-200 pm 为 SBG, 虽然更高浓度 (如多达 300 pM) 的后者可能需要。重要的是要避免的条件, 将使背景高于 0.02 AEB。增加检测单克隆抗体 (SBG) 的浓度将提高信号响应和背景。然而, 如果信号的增量超越背景的变化, LOD 将会改善。可能出现的情况是, 背景的减少使低校准仪之间的差别更高。</li>
	</ol>
</li>
</ol><img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57421/57421fig3v2.jpg"> 图 3: 探测器和 SBG 浓度优化.评估了三种不同浓度的生物素化检测抗体 (0.1、0.3 和0.6 µg/毫升) 和三种不同浓度的 SBG (50、150和 250 pM)。虚线显示 LOD 的最佳状态;检测抗体在0.3 毫克/毫升和 SBG 150pM (LOD = 0.09 毫克/毫升对应的 AEB 值 0.017184)。<a href="/files/ftp_upload/57421/57421fig3v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<ol start="4"><li>其他优化步骤<ol>
<li>如果未达到所需的灵敏度, 请使用分析器软件中的预配置选项测试不同步骤的不同潜伏期。</li>
		<li>如果检测不够灵敏, 请使用分析器软件中预配置的选项优化每种检测的珠子数量。 注: 一旦生物样品的测试开始, 样品体积是一个附加参数易受优化。确保样品根据健康和安全程序进行处理。</li>
	</ol>
</li>
</ol>5. 化验特异性和重现性
<ol><li>测试干扰素-α测定特异性, 通过测试与不同的干扰素α亚型和其他相关的蛋白质 (图 4a和4b)。</li>
</ol><img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57421/57421fig4.jpg"> 图 4: 优化 IFNα单分子阵列法的特异性和灵敏度.(a) 对干扰素β、IFN-λ1、IFN-λ2、干扰素和干扰素-γ重组蛋白进行了测试, 以及 (B) 16 亚型干扰素α, 包括三种 IFN-α2类型 (IFN-α2a、IFN-α2b 和 IFN-α2c)。改编自 Rodero等。2017.<a href="/files/ftp_upload/57421/57421fig4large.jpg" target="_blank">请点击这里查看这个数字的更大版本.</a>
<ol start="2"><li>通过执行三项独立的复制实验和评估相互间的变异 (图 5), 评估优化试验的重现性。</li>
	<li>计算检测的 LOD 注: LOD 是用三空白 + 3 标准差 (SD) 的平均值计算的, 从而获得0.23 的 fg/mL 值。由于标准样品稀释系数为 1:3, 稀释因子的加入给出了0.69 个成品/mL 的 LOD。</li>
</ol><img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57421/57421fig5.jpg"> 图 5: 优化的 pan-干扰素-α单分子阵列测定的重现性.三独立运行使用两种不同的珠子进行。对第二批进行了两次独立实验。每项测量都以重复的方法获得。虚线代表的 LOD, 由平均空白平均酶每珠 + SD 的所有运行。IFN-α17被用作参考, 考虑到衍生标准曲线是所有其他干扰素α亚型的代表, 如图 4b所示。图中显示平均值和 SD (误差线)。虚线显示不同运行的 LOD;运行 1: 0.073 个成品/毫升 AEB = 0.006238, 运行 2: 0.113 fg/毫升 AEB = 0.007119, 运行 3: 0.043 成品/毫升 AEB = 0.05518)。改编自 Rodero等。2017.<a href="/files/ftp_upload/57421/57421fig5large.jpg" target="_blank">请点击这里查看这个数字的更大版本.</a>
6. 蛋白质竞争化验
<ol><li>进行蛋白质竞争分析 (如图6所示), 进一步证明化验的特异性。 注: 使用 SLE 患者血浆样本 (n = 5)。<ol>
<li>当怀疑在生物样品中存在病毒时, 通过将非 ioinic 表面活性剂 (0.5% nonidet P40 替代物) 的200µL 添加到40毫升探测器/样品稀释剂中, 并大力进行涡流制备钝化缓冲器。</li>
		<li>离心生物样品含有1万克的感兴趣的分析物, 15 分钟4摄氏度, 以去除细胞碎片。</li>
		<li>混合185µL 检测器/样品稀释剂或灭活缓冲器与100µL 生物样品 (最终稀释因子 3) 和15µL 抗干扰素α抗体 A (初始浓度1毫克/毫升, 最终浓度50微克/毫升) 或缓冲。室温下孵育30分钟。</li>
		<li>如上文所述, 在单分子阵列分析仪上运行无抗干扰素α抗体的样品。 注: 在信号饱和情况下, 样品应进一步稀释。另外, 300 µL 是重复分析所需的卷。</li>
	</ol>
</li>
</ol><img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/57421/57421fig6.jpg"> 图 6: 蛋白质竞争化验.采用五种不同 SLE 患者的样本进行了竞争实验。生物样品在4摄氏度离心10.000 克, 15 分钟。他们被稀释1/3 与检测器/样品稀释剂含有 NP40 病毒灭活。15µl 抗干扰素α抗体 A (初始浓度1毫克/毫升, 最终浓度50µg/毫升) 或缓冲增加到总体积300µL. 在室温下进行孵化30分钟. 对照组以灰色和抗干扰素α A 治疗样品为例。抗体以黑色显示。图显示平均值和 SD (误差条)。虚线代表 LOD (AEB = 0.024774, 0.8037 fg/毫升)。从 Rodero等2017 适应<a href="/files/ftp_upload/57421/57421fig6large.jpg" target="_blank">, 请点击这里查看这个数字的大版本.</a>

<ol>
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作者没有什么可透露的。

在这里, 我们描述了一个高度可重现的, 超灵敏单分子阵列数字 ELISA 的发展和验证, 以直接量化的干扰素α蛋白在人体样本 (步骤总结在表 1)。检测的最关键步骤之一是抗体对16的选择, 在动力学和表位结合方面的特点是成功测定的关键。重要的是要避免使用配对单克隆抗体的目标相同的表位或导致立体障碍。多克隆抗体可作为检测抗体来克服这种局限性。如果在任何给定的步骤没有达到期望的灵敏度, 应考虑进一步的优化可能性。这可能包括使用替代抗体对, 参数的变化, 如蛋白质类型 (如 BSA < 酪蛋白), pH 值 (6.0-8.5), 离子强度, 缓冲能力 (如氯化钠和磷酸盐浓度), 载体珠, 和/或存在的表面活性剂。在研制单分子阵列试验时, 需要对多种参数进行优化。但是, 总体而言, 提供高信号的条件: 背景比率和最小检测限是首选的 (请参见图 1、图 2和图 3)。
关于特异性, 干扰素α的检测显示任何其他 IFNs 测试 (β, γ, λ1, λ2, ω) 没有交叉反应 (图 4a), 并能够检测所有13干扰素α亚型 (图 4b)。然而, 该检测显示 IFN-α2亚型的亲和力较低 (图 4b和补充表 4)。有趣的是, 对不同类别的 IFN-α2 (a, b, c) 也有不同的敏感性, 这可能是由于不同的制造程序或不同的氨基酸序列, 因为 IFN-α2亚型是从各种商业供应商。有了这个唯一的例外, 所有的干扰素α物种作出了非常相似的反应。通过对样品的预处理与抗干扰素α A 克隆的结合, 进一步证明了该方法的特异性, 废除了该信号 (图 6和补充表 6)。
这种技术的一个主要优点是, 任何感兴趣的分析物都有可能成为目标16。此外, 可以测试不同的生物标本, 如血清, 血浆, 脑脊液, 细胞裂解物, 培养上清液31 , 甚至呼吸32。通常, 1:3 的等离子稀释是为了避免单分子阵列分析仪的潜在堵塞。然而, 感兴趣的分析物可能存在于相关生物样品的极低浓度, 并且可能需要更高浓度的样品 (取决于测定灵敏度)33。尽管有可能进行多路复用, 同时保持良好的灵敏度为34, 但它是一个更具挑战性的过程, 在相同的实验中测量大于6蛋白质的测试还有待开发35。
在这种低浓度下检测和量化细胞因子和其他生物相关蛋白的能力开辟了一个全新的应用范围33,36。众所周知, 许多蛋白质甚至在极低浓度下发挥作用, 直到现在都低于最佳 ELISAs37的检测极限。虽然其他免疫分析技术提供优于常规 ELISA19, 我们在这里证明, 单分子阵列数字 ELISA 是一个重现性和稳健的平台超灵敏检测低浓度细胞因子在人类样本。因此, 这项技术为生物标志物发现和改善病人对多种疾病的管理提供了巨大的潜力。

I 型 IFNs 是一种细胞因子的家族, 在协调抗病毒免疫应答中起着核心作用。他们首先发现了由萨克斯和 Lindenmann 60 年前1,2和它现在知道这个异构的多肽家庭包括14个不同的子类 (13 干扰素α亚型和1干扰素β)。I 型 IFNs 是清除病毒感染的必要条件, 但也牵涉到各种人类疾病的病理状态, 包括自身免疫性疾病系统性红斑狼疮 (SLE), 青少年皮肌炎 (JDM), 和类型i interferonopathies 的 i. 型干扰素诱导的信号, 导致病理3,4,5,6,7。
研究 I 型干扰素蛋白在生物样品中的水平一直是挑战, 因为它最初的鉴定为 "干扰物质"1,2。目前, 夹心酶联免疫吸附法 (ELISA) 是检测干扰素α蛋白最常用的方法。尽管是特定的, 简单, 快速, I 型干扰素 ELISAs 目前的重要限制, 如有限的敏感性。此外, 所有干扰素α亚型的测量都需要使用多种检测方法, 每个测试都有自己的探测能力和灵敏度。虽然有商业 ELISAs 检测不同亚型干扰素α, 他们的灵敏度是有限的 (1.95 pg/毫升, 12.5 pg/毫升, 12.5 pg/毫升, 分别) 往往不足以检测干扰素α蛋白的生物样品。为了克服这一局限性, 通过测量诱导基因表达或功能活动8、9、10、11,开发了几种生物代理检测法来量化 I 型干扰素。12,13,14. 尽管如此, 这些化验结果并不能直接测量干扰素α蛋白。
本研究采用单分子阵列数字 ELISA 技术, 研制出一种检测单干扰素-α蛋白分子的方法。数字 elisa 采用与常规 elisa 相同的基础化学, 然而, 反应发生在阵列包括5万个单独 46 femtoliter 大小井15,16。单蛋白分子由抗体涂层顺磁性珠捕获, 并标记为生物素化检测抗体, 其次是结合酶共轭, 链亲和素β-乳糖酶 (SBG)。随后, 珠被悬浮与荧光酵素基体, 试卤灵β D-galactopyranoside (RGP), 入单分子阵列。通过减少20亿乘以17的体积反应, 达到了高局部荧光信号浓度, 单分子计数变得可行, 因为每个分子产生的信号, 现在可以可靠地测量18。在本质上, 单分子阵列能够计数单个免疫复合物, 并确定每个珠的平均酶数 (AEB)。计数信号被检测到的 microwells 允许量化/数字化的蛋白质分子, 因为有直接相关的蛋白质浓度和比例之间的 immunocomplexed 珠和总数量的珠子呈现在femtoliter 大小的房间。
杨等。使用九种不同的技术和四个细胞因子免疫进行了广泛的跨平台评估研究, 目的是比较不同平台19之间的检测精度、灵敏度和数据相关性。研究的一个重要结果是, 单分子阵列和单分子计数免疫检测在亚 pg/mL 浓度范围内对人血清中细胞因子的测定具有最高灵敏度。采用单分子阵列数字 ELISA 细胞因子检测方法, 研究了 TNF α和 IL-6 在克罗恩病20、interferonopathy 和自体免疫患者中的作用, 以及不同 translationally 后修饰形式的 c--c主题趋化因子 10 (CXCL10) 在慢性肝炎和健康捐赠者接受西格列汀21,22。其他应用包括测量糖尿病视网膜病变患者的紫红23;通过血清/血浆测量丝光24和淀粉样β1-42 肽25, 在多发性硬化和阿尔茨海默病的背景下, 对脑部病理学进行研究。单分子阵列测定也可用于改进病原体的检测, 如 HIV 病毒储层26的表征, 以及检测 DNA27和微 rna28。单分子阵列技术的一个主要优点是这种高通用性, 因为如果有特定的抗体对, 就可以对任何感兴趣的分析物进行检测。此外, 自制的化验试剂盒在商业上是可以利用的, 允许开发新的化验, 其中的议定书是以修改后的形式详细说明的。
本文详细介绍了单分子阵列检测的发展和验证步骤, 从而提高了对干扰素α蛋白检测的灵敏度。单分子阵列检测的抗体应高度特异, 避免与相关蛋白的交叉反应 (如果相关的物种特异性考虑)。理想情况下, 应选择具有 KD小于 10-9米的抗体;高亲和性确保强约束, 具有较高的信号产生。抗体-抗原结合的动力学也很重要, 快速 k 和慢 k将有利于抗原抗体复合体的组装。从具有良好性能的经典 ELISA 的抗体对, 具有 1-100 pg/毫升的检测限制, 增加了获得高度敏感的单分子阵列检测的机会。张和同事对生物分子相互作用的每一个步骤进行了详细的动力学研究, 提出了一套预测分析灵敏度18的方程式。他们表明, 单分子阵列数字 ELISA 似乎是有效的范围内广泛的抗体亲和力 (KD~10−11 -10−9 M), 以及信号产生更依赖于这种抗体的速率。
为了利用高亲和抗体, 我们利用了自体免疫 polyendocrinopathy 综合征1型/自身免疫性 polyendocrinopathy-念珠菌病外胚层营养不良 (APS1/APECED)29的抗体。由于尚不清楚的原因, 绝大多数 AIRE 缺乏的人开发了一套核心的高亲和力抗体抗所有干扰素α亚型29, 我们选择了两个抗干扰素α抗体克隆的互补结合亲和性对于不同的干扰素α亚型, 估计由 IC50值。这些独特的高亲和抗体与单分子阵列技术的结合, 使干扰素α在 attomolar (fg/毫升) 浓度的直接量化。这种超灵敏干扰素α蛋白检测将有助于更好地了解干扰素诱发反应在不同疾病环境中的性质、调控和生物学影响。

<table><tbody><tr><td>Anti-IFN-&amp;alpha; antibody A (8H1 clone)</td><td>ImmunoQure AG</td><td>NA</td><td>Not commercially available</td></tr><tr><td>Anti-IFN-&amp;alpha; antibody B (12H5 clone)</td><td>ImmunoQure AG</td><td>NA</td><td>Not commercially available</td></tr><tr><td>Anti-IFN-&amp;alpha; antibody EBI-1 clone</td><td>eBioscience</td><td>BMS216C</td><td></td></tr><tr><td>Anti-IFN-&amp;alpha; antibody BMS216BK clone</td><td>eBioscience</td><td>BMS216BK</td><td>Not an ELISA kit but bulk abs</td></tr><tr><td>IFN &amp;alpha;2c</td><td>eBioscience</td><td>BMS305</td><td>OK</td></tr><tr><td>IFN &amp;alpha;I (17)</td><td>PBL</td><td>11150-1</td><td></td></tr><tr><td>IFN &amp;alpha;2a</td><td>PBL</td><td>11100-1</td><td></td></tr><tr><td>IFN &amp;alpha;2a</td><td>PeproTech</td><td>No longer available</td><td></td></tr><tr><td>IFN &amp;alpha;2b</td><td>PBL</td><td>11105-1</td><td></td></tr><tr><td>IFN &amp;alpha;1</td><td>PBL</td><td>11175-1</td><td></td></tr><tr><td>IFN &amp;alpha;4a (M1)</td><td>PBL</td><td>11177-1</td><td></td></tr><tr><td>IFN &amp;alpha;4b (a4)</td><td>PBL</td><td>11180-1</td><td></td></tr><tr><td>IFN &amp;alpha;B2 (a8)</td><td>PBL</td><td>11115-1</td><td></td></tr><tr><td>IFN &amp;alpha;C (a10)</td><td>PBL</td><td>11120-1</td><td></td></tr><tr><td>IFN &amp;alpha;D (a1)</td><td>PBL</td><td>11125-1</td><td></td></tr><tr><td>IFN &amp;alpha;G (a5)</td><td>PBL</td><td>11135-1</td><td></td></tr><tr><td>IFN &amp;alpha;F (a21)</td><td>PBL</td><td>11130-1</td><td></td></tr><tr><td>IFN &amp;alpha;H2 (a14)</td><td>PBL</td><td>11145-1</td><td></td></tr><tr><td>IFN &amp;alpha;J1 (a7)</td><td>PBL</td><td>11160-1</td><td></td></tr><tr><td>IFN &amp;alpha;K (a6)</td><td>PBL</td><td>11165-1</td><td></td></tr><tr><td>IFN &amp;alpha;WA (a16)</td><td>PBL</td><td>11190-1</td><td></td></tr><tr><td>IFN &amp;lambda;1</td><td>PeproTech</td><td>300-02L</td><td></td></tr><tr><td>IFN &amp;lambda;2</td><td>PeproTech</td><td>300-02K</td><td></td></tr><tr><td>IFN &amp;omega;</td><td>PeproTech</td><td>300-02J</td><td></td></tr><tr><td>IFN &amp;beta;</td><td>PeproTech</td><td>300-02BC</td><td></td></tr><tr><td>IFN &amp;gamma;</td><td>PeproTech</td><td>300-02</td><td></td></tr><tr><td>Anti-IFN-&amp;alpha; ELISA</td><td>PBL</td><td>41115.1</td><td></td></tr><tr><td>96-well plates</td><td>Corning</td><td>3904</td><td></td></tr><tr><td>ISRE-Reporter</td><td>Qiagen</td><td>CCS-008L</td><td></td></tr><tr><td>Fu-GENE HD Transfection Reagent</td><td>Promega</td><td>E2311</td><td></td></tr><tr><td>Opti-MEM Reduced Serum Mediuem</td><td>ThermoFischer Scientific</td><td>31985062</td><td></td></tr><tr><td>Dual-Luciferase Reporter assay</td><td>Promega</td><td>E1910</td><td></td></tr><tr><td>Nonidet P40 Substitute</td><td>Sigma-Aldrich</td><td>74385</td><td></td></tr><tr><td>Spectrophotometer NanoDrop 1000</td><td>Thermo Scientific</td><td>No longer available</td><td></td></tr><tr><td>Amicon micocentrifuge tubes - 0.5mL filtres</td><td>Merck Millipore</td><td>UFC505096</td><td></td></tr><tr><td>Bead Conjugation Buffer</td><td>Quanterix</td><td>102040</td><td>Can not be ordered separately</td></tr><tr><td>Non-Encoded Paramagnetic Beads</td><td>Quanterix</td><td>101360</td><td></td></tr><tr><td>Bead Wash Buffer</td><td>Quanterix</td><td>102040</td><td>Can not be ordered separately</td></tr><tr><td>EDC</td><td>Fisher Scientific</td><td>11844071</td><td></td></tr><tr><td>Bead Blocking Buffer</td><td>Quanterix</td><td>102040</td><td>Can not be ordered separately</td></tr><tr><td>Bead Diluent Buffer</td><td>Quanterix</td><td>101362</td><td></td></tr><tr><td>Detector and Sample Diluent</td><td>Quanterix</td><td>101359</td><td></td></tr><tr><td>Biotinylation Reaction Buffer</td><td>Quanterix</td><td>102040</td><td>Can not be ordered separately</td></tr><tr><td>NHS-PEG4-Biotin</td><td>Fisher Scientific</td><td>11891195</td><td></td></tr><tr><td>diH&lt;sub&gt;2&lt;/sub&gt;O</td><td></td><td></td><td></td></tr><tr><td>Centrifuge for 1.7mL microcentrifuge tubes (Heraens Fresco 21 Centrifuge)</td><td>Thermo Scientific</td><td>75002478</td><td></td></tr><tr><td>Standard laboratory vortex mixer (MS2 Minishaker)</td><td>IKA</td><td>MS2</td><td></td></tr><tr><td>Pipettes (10, 20, 200 and 1000 &amp;mu;l)</td><td>Thermo Scientific</td><td></td><td></td></tr><tr><td>Tips (10, 20, 200 and 1000 &amp;mu;l)</td><td>Thermo Scientific</td><td></td><td></td></tr><tr><td>1.7mL microcentrifuge tubes</td><td>Eppendorf</td><td></td><td></td></tr><tr><td>Magnetic separator that accomodates 1.7mL microcentrifuge tubes (Life Technologies DynaMag-2)</td><td>ThermoFisher Scientific</td><td>12321D</td><td></td></tr><tr><td>Mini benchtop centrifuge (Galaxy MinisStar)</td><td>VWR</td><td>521-2844</td><td></td></tr><tr><td>Mixer/Shaker (Eppendorf Thermomixer Comfort)</td><td>Eppendorf</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Single molecule array (Simoa) reagents&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>SBG, Bead and Detector Barcode Labels</td><td>Quanterix</td><td>101652</td><td></td></tr><tr><td>15 mL Reagent Bottles</td><td>Quanterix</td><td>102411</td><td></td></tr><tr><td>Simoa specimen 96-well plates</td><td>Quanterix</td><td>101457</td><td></td></tr><tr><td>Simoa Discs</td><td>Quanterix</td><td>100001</td><td></td></tr><tr><td>Simoa 2.0 conductive Tips</td><td>Quanterix</td><td>101726</td><td></td></tr><tr><td>Simoa Cuvettes</td><td>Quanterix</td><td>100803</td><td></td></tr><tr><td>Simoa SBG Reagent</td><td>Quanterix</td><td>102295</td><td></td></tr><tr><td>Simoa RGP Reagent</td><td>Quanterix</td><td>101736</td><td></td></tr><tr><td>Simoa System Buffer 1</td><td>Quanterix</td><td>100486</td><td></td></tr><tr><td>Simoa System Buffer 2</td><td>Quanterix</td><td>100487</td><td></td></tr><tr><td>Sealing Oil</td><td>Quanterix</td><td>100206</td><td></td></tr><tr><td>ddH&lt;sub&gt;2&lt;/sub&gt;O</td><td></td><td></td><td></td></tr><tr><td>Simoa HD-1 Analyzer</td><td>Quanterix</td><td>100032</td><td></td></tr><tr><td>&lt;u&gt;Technologies&lt;/u&gt;</td><td></td><td></td><td></td></tr><tr><td>Single molecule array (Simoa)</td><td>Quanterix</td><td></td><td></td></tr><tr><td>Single molecule counting Erenna Immunoassay Systems</td><td>Singluex</td><td></td><td></td></tr></tbody></table>

development and validation of an ultrasensitive single molecule array digital enzyme-linked immunosorbent assay for human interferon-&#945;

本协议的主要目的是描述干扰素 (干扰素) α单分子阵列数字酶联免疫吸附试验 (ELISA) 检测的发展和有效性。该系统使人类干扰素α蛋白的定量化具有前所未有的灵敏度, 对其他干扰素的种类无交叉反应性。
该协议的第一个关键步骤是抗体对的选择, 其次是捕获抗体与顺磁性珠的共轭, 以及检测抗体的 biotinylation。在此步骤之后, 可以修改不同的参数, 如检测配置、检测抗体浓度和缓冲成分, 直到达到最佳灵敏度为止。最后, 评估了该方法的特异性和重现度, 以确保结果的可信度。在这里, 我们开发了一种干扰素-α单分子阵列检测, 用高亲和性自身抗体从 biallelic 突变的患者中分离出的0.69 毫升/mL, 其自身免疫调节蛋白 (AIRE) 导致自身免疫性 polyendocrinopathy综合征1型/自身免疫性 polyendocrinopathy-念珠菌性外胚层营养不良 (APS1/APECED)。重要的是, 这些抗体能够检测到所有13种干扰素α亚型。
这种新方法允许首次在 attomolar 浓度下检测和定量测定人类生物样品中的干扰素α蛋白。这种工具对于监测人类健康和疾病状态中这种细胞因子的水平非常有用, 尤其是感染、自身免疫和 autoinflammation。

总之, 一个 pan-干扰素-α单分子阵列检测的限制0.69 的成品/毫升, 使用2步配置与捕获珠涂覆0.3 毫克/毫升抗干扰素α抗体和抗干扰素α B 检测抗体生物素化在生物素: 抗体比30被开发了。生物素化检测抗体和 SBG 浓度分别为0.3 µg/毫升和 150 pM。这种高度特异的检测能够检测出所有13种干扰素α亚型, 不与其他类型的 IFNs 发生交叉反应。因此, 虽然无法识别和量化每种干扰素α, 但它们都可以被检测和测量, 同时给出含有13种不同子类的干扰素α的总浓度值。
为探讨新研制的检测方法对健康个体血浆和血清中干扰素α蛋白的诊断价值, 并与 SLE 和 JDM 患者的样本进行比较。如图 7所示, 与健康对照组相比, 两种疾病群中均检测出高水平的干扰素α蛋白。虚线表明了传统的商用 ELISA 的 LOD, 说明这种方法不会检测到这些患者组的干扰素α蛋白, 尽管已知的这种细胞因子与这些表型的关联。此外, 干扰素α可以被量化超过5对数的数量, 说明了广泛的动态范围的检测, 与检测水平之间的 1-10 的 fg/毫升确认高度敏感的性质的化验。
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/57421/57421fig7.jpg"> 图 7: 从患者群中测定血浆和血清中干扰素α蛋白的数量.这个数字已经从 Rodero. 2017. 用泛 IFNα单分子阵列法对健康对照组 (n = 20) 和患有 SLE (n = 72) 和 JDM (n = 43) 的患者进行了血浆检测。采用单向方差分析试验 (克鲁斯卡尔) 和邓恩的多组比较试验进行了研究。中值被描述。虚线表示参考人类抗干扰素α ELISA 的 LOD (1.95 pg/毫升 = 1950 fg/毫升)。<a href="/files/ftp_upload/57421/57421fig7large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td>步</td>
			<td>考虑</td>
			<td>参考</td>
		</tr>
<tr>
<td rowspan="3">1. 抗体对选择</td>
			<td>目标不同的表位</td>
			<td rowspan="3">表2</td>
		</tr>
<tr>
<td>高亲和力</td>
		</tr>
<tr>
<td>快速 k开/慢 k
</td>
		</tr>
<tr>
<td>2. 抗体对取向</td>
			<td rowspan="3">选择最低检测限制条件</td>
			<td rowspan="3">图1</td>
		</tr>
<tr>
<td>3. 捕获抗体浓度</td>
		</tr>
<tr>
<td>4. 生物素: 探测器抗体比</td>
		</tr>
<tr>
<td>5. 2 vs 3 步配置</td>
			<td>选择具有最高信号的条件: 背景比</td>
			<td>图2</td>
		</tr>
<tr>
<td>6. 检测抗体浓度</td>
			<td rowspan="2">选择最低检测限制条件</td>
			<td rowspan="2">图3</td>
		</tr>
<tr>
<td>7. SBG 浓度</td>
		</tr>
<tr>
<td>8. 特异性</td>
			<td>评估交叉反应性</td>
			<td rowspan="2">图4</td>
		</tr>
<tr>
<td>9. 灵敏度</td>
			<td>评估子类型的识别 (如果适用)</td>
		</tr>
<tr>
<td>10. 重现性</td>
			<td>评估化验变异性</td>
			<td>图5</td>
		</tr>
</tbody></table>表 1: 单分子阵列测定的发展和优化步骤摘要.本表总结了单分子阵列检测的发展和优化所需的不同步骤, 从抗体对的初始选择直到重现性的评估。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td>抗原</td>
			<td>8H1 (A)</td>
			<td>12H5 (B)</td>
			<td>Sifalimumab</td>
			<td>Rontalizumab</td>
		</tr>
<tr>
<td>IFNα1</td>
			<td>28。3</td>
			<td>51。3</td>
			<td>460</td>
			<td>22.63</td>
		</tr>
<tr>
<td>IFNα2</td>
			<td>2563</td>
			<td>10。7</td>
			<td>9.02</td>
			<td>2.15</td>
		</tr>
<tr>
<td>IFNα4</td>
			<td>5.11</td>
			<td>2.99</td>
			<td>35.35</td>
			<td>325。3</td>
		</tr>
<tr>
<td>IFNα5</td>
			<td>2.01</td>
			<td>19。6</td>
			<td>93.29</td>
			<td>2.49</td>
		</tr>
<tr>
<td>IFNα6</td>
			<td>64。7</td>
			<td>3.03</td>
			<td>4.97</td>
			<td>-</td>
		</tr>
<tr>
<td>IFNα7</td>
			<td>0。9</td>
			<td>0.63</td>
			<td>233。1</td>
			<td>-</td>
		</tr>
<tr>
<td>IFNα8</td>
			<td>302</td>
			<td>0.83</td>
			<td>691</td>
			<td>10.86</td>
		</tr>
<tr>
<td>IFNα10</td>
			<td>2.54</td>
			<td>0.71</td>
			<td>43。2</td>
			<td>-</td>
		</tr>
<tr>
<td>IFNα14</td>
			<td>3224</td>
			<td>2。1</td>
			<td>14.52</td>
			<td>0。9</td>
		</tr>
<tr>
<td>IFNα16</td>
			<td>1.83</td>
			<td>32.99</td>
			<td>59.18</td>
			<td>28.65</td>
		</tr>
<tr>
<td>IFNα17</td>
			<td>2.21</td>
			<td>0.77</td>
			<td>890。9</td>
			<td>23.86</td>
		</tr>
<tr>
<td>IFNα21</td>
			<td>2.78</td>
			<td>12.87</td>
			<td>1769</td>
			<td>5。8</td>
		</tr>
</tbody></table>表 2: Pan α抗体的选择.IC50 (ng/毫升) 用干扰素刺激的反应元素 (ISRE)-荧光素酶中和法测定。表显示了用于所有干扰素α亚型的单分子阵列检测中抗体的 IC50 值。1万 HEK 293 星享细胞被播种在白色半区域96井板和反向转染与 50 ng 预混 ISRE-萤火虫荧光素酶的记者和 Renilla 荧光素酶的结构, 根据制造商的指示使用染用试剂。荧光素酶表达结构作为内部规范化控制。细胞在一夜间孵化在减少的血清培养基补充0.1 毫米不必要的氨基酸, 1 毫米丙酮酸钠, 0.5% 胎牛血清在37°c, 5% CO2在一个湿润的气氛。在夜间孵化后, 细胞被刺激24小时, 其中含有重组人干扰素α的混合物, 有或没有抗干扰素α抗体或对照 IgG, 在37摄氏度 preincubated 1 小时。经过24小时的刺激, 双荧光素酶的报告化验是根据制造商的指示进行。«-»没有确定。Sifalimumab 是一个完全人类, 免疫球蛋白 G1 κ单克隆抗体, 结合和中和大多数干扰素α亚型;Rontalizumab 是一种抗干扰素α的人性化单克隆抗体。改编自迈耶等2016 和 Rodero等。2017。
补充表 1: 选择抗体定位, 捕获抗体浓度的珠子和 biotinylation 比.用抗干扰素α A 作为捕获抗体和抗干扰素α B 作为检测抗体 (a), 对两种可能的不同构型进行了测试, 反之亦然 (B)。IFNα-2c 被用作抗原。不同的捕获抗体浓度和生物素: 抗体 (B: A) 比率也测试两种配置。饱和度 (Sat)。橙色: 用于 LOD 计算的 AEB 值;这些浓度被认为是空白的, 因为 AEB 值保持稳定。LOD 计算为平均空白 + 3SD.<a href="/files/ftp_upload/57421/Supplementary_Table_1.xlsx">请单击此处下载此文件.</a>
补充表 2: 测试 2 vs 3 步配置.用 IFNα-2c 作为抗原对2和3步构型进行了评估。AEB 值以及信号/背景口粮 (S/B) 都显示在这两个条件。<a href="/files/ftp_upload/57421/Supplementary_Table_2.xlsx">请单击此处下载此文件.</a>
辅助表 3: 检测器和 SBG 浓度优化.评估了三种不同浓度的生物素化检测抗体 (0.1、0.3 和0.6 µg/毫升) 和三种不同浓度的 SBG (50、150和 250 pM)。AEB 值显示在九测试条件下。橙色: 用于 LOD 计算的 AEB 值;这些浓度被认为是空白的, 因为 AEB 值保持稳定。LOD 计算为平均空白 + 3SD.<a href="/files/ftp_upload/57421/Supplementary_Table_3.xlsx">请单击此处下载此文件.</a>
补充表 4: 优化 IFNα单分子阵列法的特异性和灵敏度.当干扰素β、IFN-λ1、IFN-λ2、干扰素和干扰素-γ重组蛋白 (A) 和干扰素-α (B) 的16亚型进行测试时, 每个珠子的平均酶值均显示出来。«-»没有确定。<a href="/files/ftp_upload/57421/Supplementary_Table_4.xlsx">请单击此处下载此文件.</a>
补充表 5: 优化 IFNα单分子阵列测定的重现性.所有三独立奔跑的平均 AEB 值显示由10.000 个 fg/毫升的集中。«-»没有确定。饱和度 (Sat)。<a href="/files/ftp_upload/57421/Supplementary_Table_5.xlsx">请单击此处下载此文件.</a>
补充表 6: 蛋白质竞争化验.所有测试的条件都显示每个珠子的平均酶值。测量是重复进行的。<a href="/files/ftp_upload/57421/Supplementary_Table_6.xlsx">请单击此处下载此文件.</a>

Watch this Scientific Journal Video about Development and Validation of an Ultrasensitive Single Molecule Array Digital Enzyme-linked Immunosorbent Assay for Human Interferon-Î± at JoVE.com

Development and Validation of an Ultrasensitive Single Molecule Array Digital Enzyme-linked Immunosorbent Assay for Human Interferon-&#945;

在这里, 我们提出一个协议来描述一个单一的分子阵列数字 ELISA 检测的发展和验证, 这使得对所有干扰素α亚型的超敏检测在人体标本。

人干扰素α超灵敏单分子阵列数字酶联免疫吸附试验的研制与验证

The main aim of this protocol is to describe the development and validation of an interferon (IFN)-&#945; single molecule array digital Enzyme-Linked ...

development-validation-an-ultrasensitive-single-molecule-array

Research

JoVE Journal

Immunology and Infection

11.9K 次观看.  Institut Pasteur. 在这里, 我们提出一个协议来描述一个单一的分子阵列数字 ELISA 检测的发展和验证, 这使得对所有干扰素α亚型的超敏检测在人体标本。

视频: Development and Validation of an Ultrasensitive Single Molecule Array Digital Enzyme-linked Immunosorbent Assay for Human Interferon-α

An ELISA Based Binding and Competition Method to Rapidly Determine Ligand-receptor Interactions

A comprehensive understanding of signaling pathways requires detailed knowledge regarding ligand-receptor interaction. This article describes two fast and reliable point-by-point protocols of enzyme-linked immunosorbent assays (ELISAs) for the investigation of ligand-receptor interactions: the direct ligand-receptor interaction assay (LRA) and the competition LRA. As a case study, the ELISA based analysis of the interaction between different lambda interferons (IFNLs) and the alpha subunit of their receptor (IL28RA) is presented: the direct LRA is used for the determination of dissociation constants (KD values) between receptor and IFN ligands, and the competition LRA for the determination of the inhibitory capacity of an oligopeptide, which was designed to compete with the IFNLs at their receptor binding site. Analytical steps to estimate KD and half maximal inhibitory concentration (IC50) values are described. Finally, the discussion highlights advantages and disadvantages of the presented method and how the results enable a better molecular understanding of ligand-receptor interactions.

The presented protocols describe two enzyme-linked immunosorbent assay (ELISA) based techniques for the rapid investigation of ligand-receptor interactions: The first assay allows the determination of dissociation constant between ligand and receptor. The second assay enables a rapid screening of blocking peptides for ligand-receptor interactions.

的ELISA基结合和竞争法快速测定配体 - 受体相互作用

A comprehensive understanding of signaling pathways requires detailed knowledge regarding ligand-receptor interaction. This article describes two fast and ...

科研

化学

High-throughput Detection Method for Influenza Virus

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, precise diagnosis of the infecting strain and rapid high-throughput screening of vast numbers of clinical samples is paramount to control the spread of pandemic infections. Current clinical diagnoses of influenza infections are based on serologic testing, polymerase chain reaction, direct specimen immunofluorescence and cell culture 1,2.
Here, we report the development of a novel diagnostic technique used to detect live influenza viruses. We used the mouse-adapted human A/PR/8/34 (PR8, H1N1) virus 3 to test the efficacy of this technique using MDCK cells 4. MDCK cells (104 or 5 x 103 per well) were cultured in 96- or 384-well plates, infected with PR8 and viral proteins were detected using anti-M2 followed by an IR dye-conjugated secondary antibody. M2 5 and hemagglutinin 1 are two major marker proteins used in many different diagnostic assays. Employing IR-dye-conjugated secondary antibodies minimized the autofluorescence associated with other fluorescent dyes. The use of anti-M2 antibody allowed us to use the antigen-specific fluorescence intensity as a direct metric of viral quantity. To enumerate the fluorescence intensity, we used the LI-COR Odyssey-based IR scanner. This system uses two channel laser-based IR detections to identify fluorophores and differentiate them from background noise. The first channel excites at 680 nm and emits at 700 nm to help quantify the background. The second channel detects fluorophores that excite at 780 nm and emit at 800 nm. Scanning of PR8-infected MDCK cells in the IR scanner indicated a viral titer-dependent bright fluorescence. A positive correlation of fluorescence intensity to virus titer starting from 102-105 PFU could be consistently observed. Minimal but detectable positivity consistently seen with 102-103 PFU PR8 viral titers demonstrated the high sensitivity of the near-IR dyes. The signal-to-noise ratio was determined by comparing the mock-infected or isotype antibody-treated MDCK cells.
Using the fluorescence intensities from 96- or 384-well plate formats, we constructed standard titration curves. In these calculations, the first variable is the viral titer while the second variable is the fluorescence intensity. Therefore, we used the exponential distribution to generate a curve-fit to determine the polynomial relationship between the viral titers and fluorescence intensities. Collectively, we conclude that IR dye-based protein detection system can help diagnose infecting viral strains and precisely enumerate the titer of the infecting pathogens.

This method describes the use of Infrared dye based imaging system for detection of H1N1 in bronchioalveolar lavage (BAL) fluid of infected mice at a high sensitivity. This methodology can be performed in a 96- or 384-well plate, requires &lt;10 &mu;l volume of test material and has the potential for concurrent screening of multiple pathogens.

流感病毒的高通量检测方法

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, ...

免疫与感染

High-throughput Quantitative Real-time RT-PCR Assay for Determining Expression Profiles of Types I and III Interferon Subtypes

Described in this report is a qRT-PCR assay for the analysis of seventeen human IFN subtypes in a 384-well plate format that incorporates highly specific locked nucleic acid (LNA) and molecular beacon (MB) probes, transcript standards, automated multichannel pipetting, and plate drying. Determining expression among the type I interferons (IFN), especially the twelve IFN-&#945; subtypes, is limited by their shared sequence identity; likewise, the sequences of the type III IFN, especially IFN-&#955;2 and -&#955;3, are highly similar. This assay provides a reliable, reproducible, and relatively inexpensive means to analyze the expression of the seventeen interferon subtype transcripts.

This protocol describes a high-throughput qRT-PCR assay for the analysis of type I and III IFN expression signatures. The assay discriminates single base pair differences between the highly similar transcripts of these genes. Through batch assembly and robotic pipetting, the assays are consistent and reproducible.

高通量实时定量RT-PCR检测方法的确定I型和III型干扰素亚型的表达谱

Described in this report is a qRT-PCR assay for the analysis of seventeen human IFN subtypes in a 384-well plate format that incorporates highly specific ...

Development of a Lateral Flow Immunochromatographic Strip for Rapid and Quantitative Detection of Small Molecule Compounds

Membrane-based lateral flow immunochromatographic strips (ICSs) are useful tools for low-cost self-diagnosis and have been efficiently applied to toxin, physiological index and clinical biomarker detection. In this protocol, we provide a detailed description of the steps to develop a rapid, sensitive and quantitative lateral-flow immunoassay (using AuNPs as a marker and mAbs as a probe). The procedure describes the preparation and characterization of colloidal gold, synthesis of the AuNP-mAb conjugate, assembly of the immunochromatographic strip, and methodological investigation of the assay. The results showed that the final strips can be further utilized for the rapid and convenient self-diagnosis of a small molecule, which may provide an alternative tool in the rapid and precise analysis of physiological and biological indices.

开发用于快速定量检测小分子化合物的横向流动免疫色谱带

Membrane-based lateral flow immunochromatographic strips (ICSs) are useful tools for low-cost self-diagnosis and have been efficiently applied to toxin, ...

生物化学

Multiplexed Fluorometric ImmunoAssay Testing Methodology and Troubleshooting

To ensure the quality of animal models used in biomedical research we have developed a number of diagnostic testing strategies and methods to determine if animals have been exposed to adventitious infectious agents (viruses, mycoplasma, and other fastidious microorganisms). Infections of immunocompetent animals are generally transient, yet serum antibody responses to infection often can be detected within days to weeks and persist throughout the life of the host. Serology is the primary diagnostic methodology by which laboratory animals are monitored. Historically the indirect enzyme-linked immunosorbent assay (ELISA) has been the main screening method for serosurveillance. The ELISA is performed as a singleplex, in which one microbial antigen-antibody reaction is measured per well. In comparison the MFIA is performed as a multiplexed assay. Since the microspheres come in 100 distinct color sets, as many as 100 different assays can be performed simultaneously in a single microplate well. This innovation decreases the amount of serum, reagents and disposables required for routine testing while increasing the amount of information obtained from a single test well. In addition, we are able to incorporate multiple internal control beads to verify sample and system suitability and thereby assure the accuracy of results. These include tissue control and IgG anti-test serum species immunoglobulin (&alpha;Ig) coated bead sets to evaluate sample suitability. As in the ELISA and IFA, the tissue control detects non-specific binding of serum immunoglobulin. The &alpha;Ig control (Serum control) confirms that serum has been added and contains a sufficient immunoglobulin concentration while the IgG control bead (System Suitability control), coated with serum species immunoglobulin, demonstrates that the labeled reagents and Luminex reader are functioning properly.

Using Luminex Corporation&#x2019;s xMAP microsphere technology, we have developed the Multiplexed Fluorometric ImmunoAssay (MFIA) for serosurveillance of various laboratory animal species. The MFIA is a suspension microarray where antigen, tissue control or immunoglobulins are covalently linked to color-coded polystyrene microspheres. The MFIA testing method as well as various troubleshooting topics is addressed.

复用荧光免疫检测方法和故障排除

To ensure the quality of animal models used in biomedical research we have developed a number of diagnostic testing strategies and methods to determine if ...

生物学

An Optimized Hemagglutination Inhibition (HI) Assay to Quantify Influenza-specific Antibody Titers

Antibody titers are commonly used as surrogate markers for serological protection against influenza and other pathogens. Detailed knowledge of antibody production pre- and post-vaccination is required to understand vaccine-induced immunity. This article describes a reliable point-by-point protocol to determine influenza-specific antibody titers. The first protocol describes a method to specify the antigen amounts required for hemagglutination, which standardizes the concentrations for subsequent usage in the second protocol (hemagglutination assay, HA assay). The second protocol describes the quantification of influenza-specific antibody titers against different viral strains by using a serial dilution of human serum or cell culture supernatants (hemagglutination inhibition assay, HI assay).
As an applied example, we show the antibody response of a healthy cohort, which received a trivalent inactivated influenza vaccine. Additionally, the cross-reactivity between the different influenza viruses is shown and methods to minimize cross-reactivity by using different types of animal red blood cells (RBCs) are explained. The discussion highlights advantages and disadvantages of the presented assays and how the determination of influenza-specific antibody titers can improve the understanding of vaccine-related immunity.

An Optimized Hemagglutination Inhibition HI Assay to Quantify Influenza-specific Antibody Titers

The presented protocols describe how to perform a hemagglutination inhibition assay to quantify influenza-specific antibody titers from serum samples of influenza vaccine recipients. The first assay determines optimal viral antigen concentrations by hemagglutination. The second assay quantifies influenza-specific antibody titers by hemagglutination inhibition.

一种优化的血凝抑制 (HI) 测定流感特异抗体滴

Antibody titers are commonly used as surrogate markers for serological protection against influenza and other pathogens. Detailed knowledge of antibody ...

医学

High-Efficiency Generation of Antigen-Specific Primary Mouse Cytotoxic T Cells for Functional Testing in an Autoimmune Diabetes Model

Type 1 Diabetes (T1D) is characterized by islet-specific autoimmunity leading to beta cell destruction and absolute loss of insulin production. In the spontaneous non-obese diabetes (NOD) mouse model, insulin is the primary target, and genetic manipulation of these animals to remove a single key insulin epitope prevents disease. Thus, selective elimination of professional antigen presenting cells (APCs) bearing this pathogenic epitope is an approach to inhibit the unwanted insulin-specific autoimmune responses, and likely has greater translational potential.
Chimeric antigen receptors (CARs) can redirect T cells to selectively target disease-causing antigens. This technique is fundamental to recent attempts to use cellular engineering for adoptive cell therapy to treat multiple cancers. In this protocol, we describe an optimized T-cell retrovirus (RV) transduction and in vitro expansion protocol that generates high numbers of functional antigen-specific CD8 CAR-T cells starting from a low number of naive cells. Previously multiple CAR-T cell protocols have been described, but typically with relatively low transduction efficiency and cell viability following transduction. In contrast, our protocol provides up to 90% transduction efficiency, and the cells generated can survive more than two weeks in vivo and significantly delay disease onset following a single infusion. We provide a detailed description of the cell maintenance and transduction protocol, so that the critical steps can be easily followed. The whole procedure from primary cell isolation to CAR expression can be performed within 14 days. The general method may be applied to any mouse disease model in which the target is known. Similarly, the specific application (targeting a pathogenic peptide/MHC class II complex) is applicable to any other autoimmune disease model for which a key complex has been identified.

This article describes a protocol for the generation of antigen-specific CD8 T cells, and their expansion in vitro, with the aim of yielding high numbers of functional T cells for use in vitro and in vivo.

在自身免疫糖尿病模型中高效生成抗原特异性原小鼠细胞毒性T细胞细胞细胞，用于功能测试

Type 1 Diabetes (T1D) is characterized by islet-specific autoimmunity leading to beta cell destruction and absolute loss of insulin production. In the ...

Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19

Multiplex technologies for interrogating multiple biomarkers in concert have existed for several decades; however, methods to evaluate multiple epitopes on the same analyte remain limited. This report describes the development and optimization of a multiplexed immunobead assay for serological testing of common immunoglobulin isotypes (e.g., IgA, IgM, and IgG) associated with an immune response to SARS-CoV-2 infection or vaccination. Assays were accomplished using a flow-based, multiplex fluorescent reader with dual-channel capability. Optimizations focused on analyte capture time, detection antibody concentration, and detection antibody incubation time. Analytical assay performance characteristics (e.g., assay range (including lower and upper limits of quantitation); and intra- and inter-assay precision) were established for either IgG/IgM or IgA/IgM serotype combination in tandem using the 'dual channel' mode. Analyte capture times of 30 min for IgG, 60 min for IgM, and 120 min for IgA were suitable for most applications, providing a balance of assay performance and throughput. Optimal detection antibody incubations at 4 &#181;g/mL for 30 min was observed and are recommended for general applications, given the overall excellent precision (percent coefficient of variance (%CV) &#8804; 20%) and sensitivity values observed. The dynamic range for the IgG isotype spanned several orders of magnitude for each assay (Spike S1, Nucleocapsid, and Membrane glycoproteins), which supports robust titer evaluations at a 1:500 dilution factor for clinical applications. Finally, the optimized protocol was applied to monitoring Spike S1 seroconversion for subjects (n = 4) that completed a SARS-CoV-2 vaccine regimen. Within this cohort, Spike S1 IgG levels were observed to reach maximum titers at 14 days following second dose administration, at a much higher (~40-fold) signal intensity than either IgM or IgA isotypes. Interestingly, we observed highly variable Spike S1 IgG titer decay rates that were largely subject-dependent were observed, which will be the topic of future studies.

This article describes a convenient method for monitoring dynamic changes in antibody titers for two immunoglobulin isotypes concurrently (either IgA, IgM, or IgG) resulting from an immune response to SARS-CoV-2 infection or vaccination. This 'Multianalyte Covid-19 Immune Response Panel' employs three indirect immunoassays built on coded microspheres that are read using a flow-based multiplex reader with 'dual-channel' capability.

使用多分析物免疫珠测定法对Covid-19进行血清转换的动态监测

Multiplex technologies for interrogating multiple biomarkers in concert have existed for several decades; however, methods to evaluate multiple epitopes ...

ELISA Assays: Indirect, Sandwich, and Competitive

Source: Whitney Swanson1,2, Frances V. Sjaastad2,3, and Thomas S. Griffith1,2,3,4 
1 Department of Urology, University of Minnesota, Minneapolis, MN 55455 
2 Center for Immunology, University of Minnesota, Minneapolis, MN 55455 
3 Microbiology, Immunology, and Cancer Biology Graduate Program, University of Minnesota, Minneapolis, MN 55455 
4 Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
Enzyme-linked immunosorbent assay (ELISA) is frequently used to measure the presence and/or concentration of an antigen, antibody, peptide, protein, hormone, or other biomolecule in a biological sample. It is extremely sensitive, capable of detecting low antigen concentrations. The sensitivity of ELISA is attributed to its ability to detect the interactions between a single antigen-antibody complex (1). Moreover, the inclusion of an enzyme-conjugated antigen-specific antibody permits the conversion of a colorless substrate into a chromogenic or fluorescent product that can be detected and easily quantitated by a plate reader. When compared to the values generated by titrated amounts of a known antigen of interest, the concentration of the same antigen in the experimental samples can be determined. Different ELISA protocols have been adapted to measure antigen concentrations in a variety of experimental samples, but they all have the same basic concept (2). Choosing the type of ELISA to perform, indirect, sandwich, or competitive, depends on a number of factors, including the complexity of the samples to be tested and the antigen-specific antibodies available to use. The indirect ELISA is frequently used to determine the outcome of an immunological response, such as measuring the concentration of an antibody in a sample. The sandwich ELISA is best suited for analyzing complex samples, such as tissue culture supernatants or tissue lysates, where the analyte, or antigen of interest, is part of a mixed sample. Finally, the competitive ELISA is most often used when there is only one antibody available to detect the antigen of interest. Competitive ELISAs are also useful for detecting a small antigen with only a single antibody epitope that cannot accommodate two different antibodies due to steric hinderance. The protocol will describe the basic procedures for the indirect, sandwich, and competitive ELISA assays.
The indirect ELISA assay is commonly used to measure the amount of antibodies in serum or in the supernatant of a hybridoma culture. The general procedure for the indirect ELISA assay is:
<ol>
	<li>Coat wells with antigens</li>
	<li>Add serum or hybridoma culture supernatant containing antibody (primary or 1&#176; antibody)</li>
	<li>Incubate and wash</li>
	<li>Add secondary (or 2&#176;) enzyme-conjugated antibody</li>
	<li>Incubate and wash</li>
	<li>Add substrate</li>
</ol>
The sandwich ELISA assay differs from the indirect ELISA assay in that the method does not involve coating the plates with a purified antigen. Instead, a &#34;capture&#34; antibody is used to coat the wells of the plate. The antigen is &#34;sandwiched&#34; between the capture antibody and a second &#34;detection&#34; enzyme-conjugated antibody - where both antibodies are specific for the same antigen, but at different epitopes (3). By binding to the capture antibody/antigen complex, the detection antibody remains in the plate. Either monoclonal antibodies or polyclonal antisera can be used as the capture and detection antibodies. The main advantage of the sandwich ELISA is that the sample does not have to be purified before analysis. Moreover, the assay can be quite sensitive (4). Many commercially available ELISA kits are of the sandwich variety and use tested, matched pairs of antibodies. The general procedure for the sandwich ELISA assay is:
<ol>
	<li>Coat wells with capture antibody</li>
	<li>Add test samples containing antigen</li>
	<li>Incubate and wash</li>
	<li>Add enzyme-conjugated detection antibody.</li>
	<li>Incubate and wash</li>
	<li>Add substrate</li>
</ol>
Most commercially available sandwich ELISA kits come with enzyme-conjugated detection antibodies. In cases where an enzyme-conjugated detection antibody is not available, a secondary enzyme-conjugated antibody specific for the detection antibody can be used. The enzyme on the secondary antibody performs the same role, which is to convert the colorless substrate to a chromogenic or fluorescent product. The above-mentioned secondary enzyme-conjugated antibody would more like to be used in a &#34;homemade&#34; sandwich ELISA developed by an investigator who has generated their own monoclonal antibodies, for example. One drawback to using a secondary enzyme-conjugated antibody is to be sure it only binds to the detection antibody, and not the capture antibody bound to the plate. This would result in a measurable product in all wells, regardless of the presence or absence of antigen or detection antibody.
Finally, the competitive ELISA assay is used to detect soluble antigens. It is simple to perform, but it is only suitable when the purified antigen is available in a relatively large amount. The general procedure for the competitive ELISA assay is:
<ol>
	<li>Coat wells with antigen</li>
	<li>Incubate and wash</li>
	<li>Preincubate test sample with enzyme-conjugated primary antibodies</li>
	<li>Add mixture to well</li>
	<li>Incubate and wash away any unbound enzyme-conjugated primary antibody</li>
	<li>Add substrate</li>
</ol>
The &#34;competition&#34; in this assay comes from the fact that more antigen in the test sample used in step 3 will result in less antibody available to bind to the antigen coating the well. Thus, the intensity of the chromogenic/fluorogenic product in the well at the end of the assay is inversely related to the amount of antigen present in the test sample.
A key component in any type of ELISA is the titrated standards of known concentrations that will allow the user to determine the antigen concentration present in the test samples. Typically, a series of wells are designated for creating a standard curve, where known amounts of a purified recombinant protein are added to the wells in decreasing amounts. When these wells are processed at the same time as the test samples, the user can then have a reference set of absorbance values obtained from a microplate reader for known protein concentrations to go along with the absorbance values for the test samples. The user can then calculate a standard curve to which the test samples can be compared for determining the amount of protein of interest present. The standard curve can also determine the degree of precision of the user&#39;s dilution making.
Finally, the last step in each of the ELISA types listed above calls for the addition of a substrate. The degree of conversion of the substrate to product is directly related to the amount of enzyme present in the well. Horseradish peroxidase (HRP) and alkaline phosphatase (AP) are the most common enzymes found conjugated to antibodies. As expected, there are a number of substrates available specific for either enzyme that produce a chromogenic or fluorescent product. Moreover, substrates are available in a range of sensitivities that can increase the overall sensitivity of the assay. The user must also take into consideration the type of instrumentation available for reading the plate at the end of the experiment when picking the type of substrate to use, along with its corresponding enzyme-conjugated antibody.
Commonly used chromogenic substrates for HRP include 2,2&#39;-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS) and 3,3&#39;,5,5&#39;-tetramethylbenzidine (TMB), whereas p-Nitrophenyl Phosphate (PNPP) is used for AP. ABTS and TMB produce water-soluble green and blue colored reaction products, respectively. The green ABTS product has two major absorbance peaks, 410 and 650 nm, while the blue TMB product is best detected at 370 and 652 nm. The colors of ABTS and TMB change to yellow upon the addition of an acidic stop solution, which is best read at 450 nm. Color development for ABTS is slow, while it is fast for TMB. TMB is more sensitive than ABTS, and may produce a higher background signal if the enzymatic reaction proceeds too long. PNPP produces a yellow water-soluble product after AP conversion that absorbs light at 405 nm.

ELISA Asas :间接、三明治和竞争

Source: Whitney Swanson1,2, Frances V. Sjaastad2,3, and Thomas S. Griffith1,2,3,4
1 Department of Urology, University of Minnesota, Minneapolis, MN 55455
...

教育

JoVE Science Education

高级生物学

免疫学

Quantification of Bioactive Type-I Interferons using a Secreted Embryonic Alkaline Phosphatase Reporter Assay

Source: Bego, M. G. et al., <a href="https://app.jove.com/v/51207">Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.</a> J. Vis. Exp. (2015)
This video demonstrates secreted embryonic alkaline phosphatase assay using HEK-Blue interferon-&#945;/&#946; reporter cells to quantify the type-I interferons (IFNs) released following stimulation of plasmacytoid dendritic cells by HIV-1 Infected CD4+ T cells.

使用分泌型胚胎碱性磷酸酶报告基因测定法定量生物活性 I 型干扰素

Source: Bego, M. G. et al., Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture ...