Phagocytic cells are critical to host defense against Pseudomonas aeruginosa, a Gram-negative bacterium that is an opportunistic pathogen. Accordingly, susceptible individuals frequently have impaired innate immune responses, including those with cystic fibrosis or neutropenia. Previous studies identified that the downregulation, or loss, of bacterial flagellar motility enables bacteria to evade interactions with phagocytic cells that result in phagocytic uptake of the bacteria. However, the mechanistic bases for motility-dependent interactions between P. aeruginosa and host cell surfaces that lead to phagocytic uptake of the bacteria are poorly understood. A recent insight is that exogenous addition of a negatively charged phospholipid, phosphatidylinositol-(3,4,5)-triphosphate (PIP₃), promotes the engagement of non-motile strains of P. aeruginosa with phagocytes leading to uptake of the bacteria. Thus, we hypothesized that the engagement of P. aeruginosa by phagocytic cells is mediated by motility-dependent interactions with cell-surface polyanions. Here we report that endogenous polyanionic N-linked glycans and heparan sulfate mediate bacterial binding of P. aeruginosa by human monocytic cells. These specific interactions resulted in P. aeruginosa phagocytosis, bacterial type 3 secretion system (T3SS)-mediated cellular intoxication and the IL-1β response of host innate immune cells. Importantly, the bacterial interactions with the glycans were motility-dependent and could be recapitulated with purified, immobilized glycans. Therefore, this work describes novel interactions of P. aeruginosa with specific phagocyte cell-surface glycans that modulate relevant host innate immune responses to the bacteria, including phagocytosis, inflammation and cytotoxicity.

吞噬细胞对于宿主防御铜绿假单胞菌（一种机会性病原体的革兰氏阴性细菌）至关重要。因此，易感个体通常具有受损的先天免疫反应，包括患有囊性纤维化或中性粒细胞减少症的个体。先前的研究发现，细菌鞭毛运动的下调或丧失使细菌能够逃避与吞噬细胞的相互作用，从而导致细菌被吞噬。然而，对于导致细菌吞噬吸收的铜绿假单胞菌和宿主细胞表面之间的运动依赖性相互作用的机制基础知之甚少。最近的一个发现是外源性添加带负电荷的磷脂，即磷脂酰肌醇-(3,4,5)-三磷酸 (PIP)_{3 )，促进}绿脓杆菌的非运动菌株与吞噬细胞的结合，从而导致细菌的摄取。因此，我们假设吞噬细胞对铜绿假单胞菌的参与是由与细胞表面聚阴离子的运动依赖性相互作用介导的。在这里，我们报告内源性聚阴离子 N 连接聚糖和硫酸乙酰肝素介导人单核细胞对铜绿假单胞菌的细菌结合。这些特定的相互作用导致了铜绿假单胞菌吞噬作用、细菌 3 型分泌系统 (T3SS) 介导的细胞中毒和宿主先天免疫细胞的 IL-1β 反应。重要的是，细菌与聚糖的相互作用是运动依赖性的，并且可以用纯化的固定聚糖来概括。因此，这项工作描述了铜绿假单胞菌与特定吞噬细胞表面聚糖的新型相互作用，这些聚糖可调节宿主对细菌的相关先天免疫反应，包括吞噬作用、炎症和细胞毒性。