Antibodies from B-cell clonal lineages share sequence and structural properties as well as epitope specificity. Clonally unrelated antibodies can similarly share sequence and specificity properties and are said to be convergent. Convergent antibody responses against several antigens have been described in humans and mice and include different classes of shared sequence features. In particular, some antigens and epitopes can induce convergent responses of clonally unrelated antibodies with restricted heavy (VH) and light (VL) chain variable region germline segment usage without similarity in the heavy chain third complementarity-determining region (CDR H3), a critical specificity determinant. Whether these V germline segment-restricted responses reflect a general epitope specificity restriction of antibodies with shared VH/VL pairing is not known. Here, we investigated this question by determining patterns of antigen binding competition between clonally unrelated antigen-specific rat antibodies from paired-chain deep sequencing datasets selected based solely on VH/VL pairing. We found that antibodies with shared VH/VL germline segment pairings but divergent CDR H3 sequences almost invariably have restricted epitope specificity indicated by shared binding competition patterns. This epitope restriction included 82 of 85 clonally unrelated antibodies with 13 different VH/VL pairings binding in 8 epitope groups in 2 antigens. The corollary that antibodies with shared VH/VL pairing and epitope-restricted binding can accommodate widely divergent CDR H3 sequences was confirmed by in vitro selection of variants of anti-human epidermal growth factor receptor 2 antibodies known to mediate critical antigen interactions through CDR H3. Our results show that restricted epitope specificity determined by VH/VL germline segment pairing is a general property of rodent antigen-specific antibodies.

中文翻译：

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啮齿动物抗体库中可变区种系区段配对确定的限制性抗原决定簇特异性。

来自B细胞克隆谱系的抗体具有相同的序列和结构特性以及表位特异性。克隆无关抗体可以类似地共享序列和特异性，因此可以说是收敛的。在人类和小鼠中已经描述了针对几种抗原的趋同抗体反应，并且包括不同类别的共享序列特征。特别是，某些抗原和抗原决定簇可诱导克隆无关抗体的重链（VH）和轻链（VL）可变区种系片段使用受限，但在重链第三互补决定区（CDR H3）中没有相似性，这是至关重要的。特异性决定因素。这些V种系片段限制性反应是否反映了具有共享VH / VL配对的抗体的一般表位特异性限制。在这里，我们通过从仅基于VH / VL配对选择的成对链深度测序数据集中确定克隆无关的抗原特异性大鼠抗体之间的抗原结合竞争模式来研究此问题。我们发现具有共享的VH / VL种系片段配对但不同的CDR H3序列的抗体几乎总是具有受限的表位特异性，这是由共享的结合竞争模式指示的。该表位限制包括85种克隆无关抗体中的82种，这些抗体在13种不同的VH / VL配对中结合了2种抗原的8种表位。通过体外选择已知可通过CDR H3介导关键抗原相互作用的抗人表皮生长因子受体2抗体变异体，证实了具有共享的VH / VL配对和表位受限的结合的抗体可以适应差异很大的CDR H3序列的推论。我们的结果表明，由VH / VL种系片段配对确定的受限制的抗原决定簇特异性是啮齿动物抗原特异性抗体的一般特性。