美国杜克大学医学院Kevin O. Saunders、Barton F. Haynes与哈佛医学院Frederick W. Alt等研究人员通过工程化B细胞成熟，实现针对性地选择HIV特异性抗体突变。相关论文2019年12月6日发表在《科学》上。

研究人员在人bnAb前体敲入小鼠和接种了旨在选择不可能突变免疫原的野生型猕猴中引发了血清中和HIV-1抗体。研究人员设计了两个HIV-1包膜免疫原，它们结合CD4结合位点或V3-聚糖bnAb谱系的前体B细胞。在体外，一旦前体获得所需的不可能突变，这些免疫原就与bnAb前体更牢固地结合。用针对CD4结合位点的免疫原诱导的猕猴接种CD4结合位点的血清中和抗体。在人bnAb前体敲入小鼠中引发的抗体序列编码了对bnAb发育至关重要的功能性不可能突变。在bnAb前体敲入小鼠中，研究人员分离出了一种疫苗引发的单克隆抗体，其带有功能不大可能的突变，并能够中和多个HIV-1全局隔离株。bnAb前体、bnAb和疫苗引发的抗体的结构揭示了获得不可识别的突变在识别HIV-1包膜中发挥的确切作用。因此，这一免疫原在猕猴和敲入小鼠中引起抗体反应，表现出新生的广泛中和抗体的突变模式、结构特征或中和谱。

附：英文原文

Title: Targeted selection of HIV-specific antibody mutations by engineering B cell maturation

Author: Kevin O. Saunders, Kevin Wiehe, Ming Tian, Priyamvada Acharya, Todd Bradley, S. Munir Alam, Eden P. Go, Richard Scearce, Laura Sutherland, Rory Henderson, Allen L. Hsu, Mario J. Borgnia, Haiyan Chen, Xiaozhi Lu, Nelson R. Wu, Brian Watts, Chuancang Jiang, David Easterhoff, Hwei-Ling Cheng, Kelly McGovern, Peyton Waddicor, Aimee Chapdelaine-Williams, Amanda Eaton, Jinsong Zhang, Wes Rountree, Laurent Verkoczy, Mark Tomai, Mark G. Lewis, Heather R. Desaire, Robert J. Edwards, Derek W. Cain, Mattia Bonsignori, David Montefiori, Frederick W. Alt, Barton F. Haynes

Issue&Volume: 2019/12/06

Abstract:

INTRODUCTION

A major goal of HIV-1 vaccine development is the design of immunogens that induce broadly neutralizing antibodies (bnAbs). However, vaccination of humans has not resulted in the induction of affinity-matured and potent HIV-1 bnAbs. To devise effective vaccine strategies, we previously determined the maturation pathway of select HIV-1 bnAbs from acute infection through neutralizing antibody development. During their evolution, bnAbs acquire an abundance of improbable amino acid substitutions as a result of nucleotide mutations at variable region sequences rarely targeted by activation-induced cytidine deaminase, the enzyme responsible for antibody mutation. A subset of improbable mutations is essential for broad neutralization activity, and their acquisition represents a key roadblock to bnAb development.

RATIONALE

Current bnAb lineage–based vaccine strategies can initiate bnAb lineage development in animal models but have not specifically elicited the improbable mutations required for neutralization breadth. Induction of bnAbs requires vaccine strategies that specifically engage bnAb precursors and subsequently select for improbable mutations required for broadly neutralizing activity. We hypothesized that vaccination with immunogens that bind with moderate to high affinity to bnAb B cell precursors, and with higher affinity to precursors that have acquired improbable mutations, could initiate bnAb B cell lineages and select for key improbable mutations required for bnAb development.

RESULTS

We elicited serum neutralizing HIV-1 antibodies in human bnAb precursor knock-in mice and wild-type macaques vaccinated with immunogens designed to select for improbable mutations. We designed two HIV-1 envelope immunogens that bound precursor B cells of either a CD4 binding site or V3-glycan bnAb lineage. In vitro, these immunogens bound more strongly to bnAb precursors once the precursor acquired the desired improbable mutations. Vaccination of macaques with the CD4 binding site–targeting immunogen induced CD4 binding site serum neutralizing antibodies. Antibody sequences elicited in human bnAb precursor knock-in mice encoded functional improbable mutations critical for bnAb development. In bnAb precursor knock-in mice, we isolated a vaccine-elicited monoclonal antibody bearing functional improbable mutations that was capable of neutralizing multiple HIV-1 global isolates. Structures of a bnAb precursor, a bnAb, and the vaccine-elicited antibody revealed the precise roles that acquired improbable mutations played in recognizing the HIV-1 envelope. Thus, our immunogens elicited antibody responses in macaques and knock-in mice that exhibited the mutational patterns, structural characteristics, or neutralization profiles of nascent broadly neutralizing antibodies.

CONCLUSION

Our study represents a proof of concept for targeted selection of improbable mutations to guide antibody affinity maturation. Moreover, this study demonstrates a rational strategy for sequential immunogen design to circumvent the difficult roadblocks in HIV-1 bnAb induction by vaccination. We show that immunogens should exhibit differences in affinity across antibody maturation stages where improbable mutations are necessary for the desired antibody function. This strategy of selection of specific antibody nucleotides by immunogen design can be applied to B cell lineages targeting other pathogens where guided affinity maturation is needed for a protective antibody response.

DOI: 10.1126/science.aay7199

Source:https://science.sciencemag.org/content/366/6470/eaay7199