Cow ultralong CDR3 antibodies targeting HIV gp120

 描述（由申请方提供）：几种抗HIV中和抗体的关键特征是其CDR H3的长度异常长。牛抗体的独特之处在于具有超长的CDR 3区，其长度可以超过60个氨基酸并且富含半胱氨酸。两种不同抗体Fab片段的晶体结构揭示，这些CDR 3形成由长β链“茎”组成的非常不寻常的结构，所述长β链“茎”支持远离免疫球蛋白表面突出的富含二硫化物的“节”。有趣的是，不同的抗体含有不同的二硫化物模式，这导致不同的结结构。深度测序揭示了超长CDR 3的广泛多样性，其中多种不同的二硫化物可能在旋钮内形成。克隆衍生序列的分析表明，这种多样性的结果从体细胞超突变的超长种系D区，有一个严重的密码子偏向突变为半胱氨酸。因此，牛抗体系统可以产生前所未有的mega CDR 3库，其折叠成包含体细胞产生的二硫化物的组合的令人印象深刻的微折叠多样性。我们使用BG 505 gp140三聚体免疫奶牛，发现它们能够产生稳健和广泛中和的血清抗体应答。在这个探索性的提议中，我们将利用不寻常的超长牛抗体库来产生新的抗HIV gp120的单克隆抗体，目的是鉴定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.