Osman Maria Kaukab, Robert Jonathan, Broich Lukas, Frank Dennis, Grosse Robert, Schwemmle Martin, Wrobel Antoni G, Ciminski Kevin, Sieben Christian, Reuther Peter
Institute of Virology, Medical Center-University of Freiburg, Freiburg, Germany.
Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Nat Commun. 2025 Apr 25;16(1):3847. doi: 10.1038/s41467-025-58834-y.
Prior to the discovery of bat influenza A virus (IAV) subtypes H17N10 and H18N11, all IAVs were thought to bind sialic acid residues via hemagglutinin (HA) to mediate attachment and subsequent viral entry. However, H17 and H18 engage a proteinaceous receptor: the major histocompatibility complex class II (MHCII). The mechanistic details of this hitherto unknown protein-mediated entry are not understood. Given that conventional IAVs rely on multivalent binding to sialylated glycans, we hypothesized that bat HA similarly interacts with multiple MHCII molecules. Using photoactivated localization microscopy (PALM) on fixed and live cells, we demonstrate that bat IAV particles attach to pre-existing MHCII clusters and induce a further increase in cluster size upon binding. To measure the impact of viral attachment on the dynamics of MHCII, we employ an "inverse attachment" approach, immobilizing viral particles on coverslips before seeding live MHCII-expressing cells on top. Single-molecule tracking reveals that the mobility of MHCII is indeed slowed down in viral proximity leading to a local enrichment of MHCII molecules beneath the viral particle. These findings suggest that viral attachment induces MHCII clustering, a process similar to the MHCII dynamics observed during the formation of an immunological synapse.
在发现蝙蝠甲型流感病毒（IAV）亚型H17N10和H18N11之前，所有IAV都被认为是通过血凝素（HA）结合唾液酸残基来介导附着及随后的病毒进入。然而，H17和H18利用一种蛋白质受体：主要组织相容性复合体II类（MHCII）。这种迄今未知的蛋白质介导的进入机制细节尚不清楚。鉴于传统IAV依赖于与唾液酸化聚糖的多价结合，我们推测蝙蝠HA同样与多个MHCII分子相互作用。通过对固定细胞和活细胞使用光激活定位显微镜（PALM），我们证明蝙蝠IAV颗粒附着于预先存在的MHCII簇，并在结合后导致簇大小进一步增加。为了测量病毒附着对MHCII动态变化的影响，我们采用一种“反向附着”方法，先将病毒颗粒固定在盖玻片上，然后在上面接种表达活MHCII的细胞。单分子追踪显示，在病毒附近MHCII的移动性确实减慢，导致病毒颗粒下方MHCII分子局部富集。这些发现表明病毒附着诱导MHCII聚集，这一过程类似于在免疫突触形成过程中观察到的MHCII动态变化。
