Faculté de Médecine, Université de Paris, Paris 75006, France.
INSERM U1151, CNRS UMR 8253, Institut Necker Enfants-Malades, Paris 75015, France.
Proc Natl Acad Sci U S A. 2021 Nov 9;118(45). doi: 10.1073/pnas.2109364118.
utilizes type IV pili (T4P) to adhere to and colonize host endothelial cells, a process at the heart of meningococcal invasive diseases leading to meningitis and sepsis. T4P are polymers of an antigenically variable major pilin building block, PilE, plus several core minor pilins that initiate pilus assembly and are thought to be located at the pilus tip. Adhesion of to human endothelial cells requires both PilE and a conserved noncore minor pilin PilV, but the localization of PilV and its precise role in this process remains to be clarified. Here, we show that both PilE and PilV promote adhesion to endothelial vessels in vivo. The substantial adhesion defect observed for mutants suggests it is the main adhesin. Consistent with this observation, superresolution microscopy showed the abundant distribution of PilV throughout the pilus. We determined the crystal structure of PilV and modeled it within the pilus filament. The small size of PilV causes it to be recessed relative to adjacent PilE subunits, which are dominated by a prominent hypervariable loop. Nonetheless, we identified a conserved surface-exposed adhesive loop on PilV by alanine scanning mutagenesis. Critically, antibodies directed against PilV inhibit colonization of human skin grafts. These findings explain how T4P undergo antigenic variation to evade the humoral immune response while maintaining their adhesive function and establish the potential of this highly conserved minor pilin as a vaccine and therapeutic target for the prevention and treatment of infections.
利用 IV 型菌毛（T4P）黏附并定殖宿主内皮细胞，这一过程是脑膜炎奈瑟菌侵袭性疾病导致脑膜炎和败血症的核心。T4P 是抗原可变的主要菌毛构建块 PilE 的聚合物，加上几个起始菌毛组装的核心次要菌毛，被认为位于菌毛顶端。与人类内皮细胞的黏附既需要 PilE，也需要保守的非核心次要菌毛 PilV，但 PilV 的定位及其在该过程中的精确作用仍有待阐明。在这里，我们表明 PilE 和 PilV 都促进了在体内与内皮血管的黏附。观察到 突变体的大量黏附缺陷表明它是主要的黏附素。与这一观察结果一致，超分辨率显微镜显示 PilV 在整个菌毛中广泛分布。我们确定了 PilV 的晶体结构，并在菌毛细丝内对其进行了建模。PilV 的小尺寸导致其相对于相邻的 PilE 亚基凹陷，而 PilE 亚基主要由一个突出的高变环主导。尽管如此，我们通过丙氨酸扫描诱变识别到 PilV 上一个保守的表面暴露的黏附环。至关重要的是，针对 PilV 的抗体抑制了 对人体皮肤移植物的定植。这些发现解释了为什么 T4P 会发生抗原变异，以逃避体液免疫反应，同时保持其黏附功能，并确立了这种高度保守的次要菌毛作为预防和治疗 感染的疫苗和治疗靶点的潜力。
