Cow ultralong CDR3 antibodies targeting HIV gp120

 描述(由申请人提供)：几种抗HIV中和抗体的一个关键特征是它们的CDR H3s异常长。奶牛抗体是独一无二的，因为它有超长的CDR3区域，长度可以超过60个氨基酸，并且富含半胱氨酸。两个不同抗体Fab片段的晶体结构表明，这些CDR3形成了一种非常不寻常的结构，由一个长的β链“柄”组成，它支撑着一个远离免疫球蛋白表面的富含二硫键的“旋钮”。有趣的是，不同的抗体含有不同的二硫键模式，这导致了不同的旋钮结构。深度测序揭示了超长CDR3的广泛多样性，其中许多不同的二硫键可能在旋钮内形成。对克隆衍生序列的分析表明，这种多样性是由于超长生殖系D区的体细胞超突变造成的，该D区对半胱氨酸具有严重的密码子偏向突变。因此，牛抗体系统可能会产生前所未有的巨型CDR3，这些CDR3折叠成令人印象深刻的多样性的迷你小管，其中包含身体产生的二硫化物的组合。我们使用BG505 gp140三聚体免疫奶牛，发现它们能够产生强大的和广泛的中和血清抗体反应。在这个探索性的提议中，我们将利用不同寻常的超长牛抗体库来产生新的抗HIV gp120的单抗，目的是识别HIV上新的中和表位。

 DESCRIPTION (provided by applicant): A key feature of several anti-HIV neutralizing antibodies is the unusually long length of their CDR H3s. Cow antibodies are unique in having ultralong CDR3 regions that can be over 60 amino acids in length and are cysteine-rich. Crystal structures of two different antibody Fab fragments reveal that these CDR3s form a very unusual architecture composed of a long β-strand "stalk" which supports a disulfide rich "knob" that protrudes far from the immunoglobulin surface. Interestingly, different antibodies contain different patterns of disulfides, which result in different knob structures. Deep sequencing reveals extensive diversity in the ultralong CDR3s where a multitude of different disulfides could potentially form within the knob. Analysis of clonally derived sequences suggests that this diversity results from somatic hypermutation of an ultralong germline D region that has a severe codon bias towards mutation to cysteine. Thus, the bovine antibody system may produce an unprecedented repertoire of mega CDR3s that fold into an impressive diversity of minifolds containing combinations of somatically generated disulfides. We have immunized cows using the BG505 gp140 trimer and found that they are capable of making a robust and broadly neutralizing serum antibody response. In this exploratory proposal, we will take advantage of the unusual ultralong cow antibody repertoire to generate new monoclonal antibodies against HIV gp120 with the goal of identifying new neutralizing epitopes on HIV.