Discovering potent human monoclonal antibodies (mAbs) targeting the Plasmodium falciparum circumsporozoite protein (PfCSP) on sporozoites (SPZ) and elucidating their mechanisms of neutralization will facilitate translation for passive prophylaxis and aid next-generation vaccine development. Here, we isolated a neutralizing human mAb, L9 that preferentially bound NVDP minor repeats of PfCSP with high affinity while cross-reacting with NANP major repeats. L9 was more potent than six published neutralizing human PfCSP mAbs at mediating protection against mosquito bite challenge in mice. Isothermal titration calorimetry and multiphoton microscopy showed that L9 and the other most protective mAbs bound PfCSP with two binding events and mediated protection by killing SPZ in the liver and by preventing their egress from sinusoids and traversal of hepatocytes. This study defines the subdominant PfCSP minor repeats as neutralizing epitopes, identifies an in vitro biophysical correlate of SPZ neutralization, and demonstrates that the liver is an important site for antibodies to prevent malaria.

发现针对子孢子 (SPZ) 上恶性疟原虫环子孢子蛋白 (PfCSP) 的有效人单克隆抗体 (mAb) 并阐明其中和机制，将有助于被动预防的转化并有助于下一代疫苗的开发。在这里，我们分离出了一种中和性人单克隆抗体 L9，它优先以高亲和力结合 PfCSP 的 NVDP 小重复序列，同时与 NANP 主要重复序列发生交叉反应。 L9 在介导小鼠免受蚊虫叮咬攻击方面比六种已发表的中和人 PfCSP mAb 更有效。等温滴定量热法和多光子显微镜显示，L9 和其他最具保护性的 mAb 通过两个结合事件与 PfCSP 结合，并通过杀死肝脏中的 SPZ 并阻止其从肝窦中流出和穿过肝细胞来介导保护。这项研究将次显性 PfCSP 小重复序列定义为中和表位，确定了 SPZ中和的体外生物物理相关性，并证明肝脏是抗体预防疟疾的重要部位。