Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA, United States.
Department of Biology, Swarthmore College, Swarthmore, PA, United States.
Front Immunol. 2020 Jul 17;11:1529. doi: 10.3389/fimmu.2020.01529. eCollection 2020.
Understanding affinity maturation of antibodies that can target many variants of HIV-1 is important for vaccine development. While the antigen-binding site of antibodies is known to mutate throughout the co-evolution of antibodies and viruses in infected individuals, the roles of the mutations in the antibody framework region are not well understood. Throughout affinity maturation, the CH103 broadly neutralizing antibody lineage, from an individual designated CH505, altered the orientation of one of its antibody variable domains. The change in orientation was a response to insertions in the variable loop 5 (V5) of the HIV envelope. In this study, we generated CH103 lineage antibody variants in which residues in the variable domain interface were mutated, and measured the binding to both autologous and heterologous HIV-1 envelopes. Our data show that very few mutations in an early intermediate antibody of the lineage can improve binding toward both autologous and heterologous HIV-1 envelopes. We also crystallized an antibody mutant to show that framework mutations alone can result in a shift in relative orientations of the variable domains. Taken together, our results demonstrate the functional importance of residues located outside the antigen-binding site in affinity maturation.
了解能够针对 HIV-1 多种变体的抗体的亲和力成熟对于疫苗开发非常重要。尽管已知抗体的抗原结合位点在感染个体中抗体和病毒的共同进化过程中会发生突变，但抗体框架区域突变的作用尚不清楚。在亲和力成熟过程中，来自个体 CH505 的广谱中和抗体谱系 CH103 改变了其一个抗体可变结构域的取向。这种取向的变化是对 HIV 包膜可变环 5（V5）插入的反应。在这项研究中，我们生成了 CH103 谱系抗体变体，其中可变结构域界面中的残基发生了突变，并测量了它们与同源和异源 HIV-1 包膜的结合。我们的数据表明，谱系中早期中间抗体的少数突变就可以提高对同源和异源 HIV-1 包膜的结合能力。我们还结晶了一个抗体突变体，以显示仅框架突变就可以导致可变结构域相对取向的变化。总之，我们的结果表明位于抗原结合位点之外的残基在亲和力成熟过程中具有重要的功能。
