Fine-Specificity Epitope Analysis Identifies Contact Points on Ricin Toxin Recognized by Protective Monoclonal Antibodies.
Fine-Specificity Epitope Analysis Identifies Contact Points on Ricin Toxin Recognized by Protective Monoclonal Antibodies.
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DOI：
10.4049/immunohorizons.1800042
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发表时间：
2018-09-01
期刊：
影响因子：
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通讯作者：
Mantis, Nicholas J
中科院分区：
文献类型：
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作者：
Van Slyke, Greta;Angalakurthi, Siva Krishna;Mantis, Nicholas J
蓖麻毒素是一种快速作用的蛋白质毒素，被疾病控制和预防中心归类为生物治疗剂。在这份报告中，我们描述了五个新的针对蓖麻毒素核糖体失活酶A亚单位(RTA)表面的免疫优势区域，即所谓的表位簇II的鼠单抗。这五个单抗与之前描述的四个簇II特异性单抗一起进行了测试，以确定它们通过注射被动保护小鼠免受10*LD50蓖麻毒素攻击的能力。在7天的研究期间，只有三种单抗(LE4、PH12和TB12)提供了保护。无论是结合亲和力还是体外中和毒素活性都不能完全解释LE4、PH12和Tb12‘S相对于其他六种单抗的体内活性。然而，氢交换质谱仪的表位作图研究表明，LE4、PH12和TB12在RTA上共享共同的接触点，对应于RTA的α-螺旋D和E，以及位于RTA背面的β-链d和e。其他6个单抗识别RTA上的重叠表位，但没有一个单抗与LE4、PH12和TB12具有相同的氢交换-质谱图。高密度竞争ELISA与一组蓖麻毒素特异的单结构域骆驼抗体组表明，尽管LE4、PH12和TB12与类似的二级基序接触，但它们可能从不同的角度接近RTA。这些结果强调了抗原表位特异性的细微差异如何显著影响体内抗体的功能。《免疫地平线》，2018，2：262-273。
Ricin is a fast-acting protein toxin classified by the Centers for Disease Control and Prevention as a biothreat agent. In this report, we describe five new mouse mAbs directed against an immunodominant region, so-called epitope cluster II, on the surface of ricin's ribosome-inactivating enzymatic subunit A (RTA). The five mAbs were tested alongside four previously described cluster II-specific mAbs for their capacity to passively protect mice against 10* LD50 ricin challenge by injection. Only three of the mAbs (LE4, PH12, and TB12) afforded protection over the 7-d study period. Neither binding affinity nor in vitro toxin-neutralizing activity could fully account for LE4, PH12, and TB12's potent in vivo activity relative to the other six mAbs. However, epitope mapping studies by hydrogen exchange-mass spectrometry revealed that LE4, PH12, and TB12 shared common contact points on RTA corresponding to RTA alpha-helices D and E and beta-strands d and e located on the back side of RTA relative to the active site. The other six mAbs recognized overlapping epitopes on RTA, but none shared the same hydrogen exchange-mass spectrometry profile as LE4, PH12, and TB12. A high-density competition ELISA with a panel of ricin-specific, single-domain camelid Abs indicated that even though LE4, PH12, and TB12 make contact with similar secondary motifs, they likely approach RTA from different angles. These results underscore how subtle differences in epitope specificity can significantly impact Ab functionality in vivo. ImmunoHorizons, 2018, 2: 262-273.