Rare mutations have been proposed to restrict the development of broadly neutralizing antibodies against HIV-1, but this has not been explicitly demonstrated. We hypothesized that such rare mutations might be identified by comparing broadly neutralizing and non-broadly neutralizing branches of an antibody-developmental tree. Because sequences of antibodies isolated from the fusion peptide (FP)-targeting VRC34-antibody lineage suggested it might be suitable for such rare mutation analysis, we carried out next-generation sequencing (NGS) on B cell transcripts from donor N123, the source of the VRC34 lineage, and functionally and structurally characterized inferred intermediates along broadly neutralizing and poorly neutralizing developmental branches. The broadly neutralizing VRC34.01 branch required the rare heavy-chain mutation Y33P to bind FP, whereas the early bifurcated VRC34.05 branch did not require this rare mutation and evolved less breadth. Our results demonstrate how a required rare mutation can restrict development and shape the maturation of a broad HIV-1-neutralizing antibody lineage.

已提出罕见突变来限制针对 HIV-1 的广泛中和抗体的发展，但这尚未得到明确证明。我们假设可以通过比较抗体发育树的广泛中和和非广泛中和分支来识别这种罕见突变。由于从靶向融合肽 (FP) 的 VRC34 抗体谱系中分离出的抗体序列表明它可能适用于此类罕见突变分析，因此我们对来自供体 N123 的 B 细胞转录本进行了下一代测序 (NGS)，N123 的来源VRC34 谱系，以及功能和结构特征的推断中间体沿着广泛中和和弱中和发育分支。广泛中和的 VRC34.01 分支需要罕见的重链突变 Y33P 才能结合 FP，而早期分叉的 VRC34.05 分支不需要这种罕见的突变，并且进化的广度较小。我们的结果证明了所需的罕见突变如何限制广泛的 HIV-1 中和抗体谱系的发育和形成成熟。