Pathogenic Neisseria Hitchhike on the Uropod of Human Neutrophils

Polymorphonuclear neutrophils (PMNs) are important components of the human innate immune system and are rapidly recruited at the site of bacterial infection. Despite the effective phagocytic activity of PMNs, Neisseria gonorrhoeae infections are characterized by high survival within PMNs. We reveal a novel type IV pilus-mediated adherence of pathogenic Neisseria to the uropod (the rear) of polarized PMNs. The direct pilus-uropod interaction was visualized by scanning electron microscopy and total internal reflection fluorescence (TIRF) microscopy. We showed that N. meningitidis adhesion to the PMN uropod depended on both pilus-associated proteins PilC1 and PilC2, while N. gonorrhoeae adhesion did not. Bacterial adhesion elicited accumulation of the complement regulator CD46, but not I-domain-containing integrins, beneath the adherent bacterial microcolony. Electrographs and live-cell imaging of PMNs suggested that bacterial adherence to the uropod is followed by internalization into PMNs via the uropod. We also present data showing that pathogenic Neisseria can hitchhike on PMNs to hide from their phagocytic activity as well as to facilitate the spread of the pathogen through the epithelial cell layer.多形核中性粒细胞（Polymorphonuclear neutrophils, PMNs）是人类固有免疫系统的重要组成成分，可快速募集至细菌感染部位。尽管PMNs具备高效的吞噬活性，淋病奈瑟菌（Neisseria gonorrhoeae）感染的典型特征之一便是可在PMNs内保持高存活率。本研究揭示了致病性奈瑟菌通过新型IV型菌毛（type IV pilus）介导黏附于极化PMNs的细胞尾足（uropod）的分子机制。研究人员借助扫描电子显微镜与全内反射荧光显微镜（total internal reflection fluorescence microscopy, TIRF microscopy），直接观察到了菌毛与细胞尾足之间的直接相互作用。实验结果显示，脑膜炎奈瑟菌（Neisseria meningitidis）对PMN细胞尾足的黏附依赖于菌毛相关蛋白PilC1与PilC2，而淋病奈瑟菌的黏附过程则无此依赖特性。细菌黏附可诱导补体调节蛋白CD46在黏附细菌形成的微菌落下方聚集，但含I结构域的整合素并未出现此类聚集现象。对PMNs的电子显微图像与活细胞成像结果表明，细菌黏附至细胞尾足后，可通过该结构内化进入PMNs。本研究还提供相关数据证实，致病性奈瑟菌可搭乘PMNs作为载体，一方面躲避PMNs的吞噬活性，另一方面促进病原体在上皮细胞层的扩散。