Department of Clinical Microbiology, Division of Virology, Umeå University, SE-90185 Umeå, Sweden.
Laboratory for Molecular Infection Medicine Sweden, Umeå University, SE-90185 Umeå, Sweden.
Proc Natl Acad Sci U S A. 2021 Jan 19;118(3). doi: 10.1073/pnas.2020732118.
Human adenovirus species D (HAdV-D) types are currently being explored as vaccine vectors for coronavirus disease 2019 (COVID-19) and other severe infectious diseases. The efficacy of such vector-based vaccines depends on functional interactions with receptors on host cells. Adenoviruses of different species are assumed to enter host cells mainly by interactions between the knob domain of the protruding fiber capsid protein and cellular receptors. Using a cell-based receptor-screening assay, we identified CD46 as a receptor for HAdV-D56. The function of CD46 was validated in infection experiments using cells lacking and overexpressing CD46, and by competition infection experiments using soluble CD46. Remarkably, unlike HAdV-B types that engage CD46 through interactions with the knob domain of the fiber protein, HAdV-D types infect host cells through a direct interaction between CD46 and the hexon protein. Soluble hexon proteins (but not fiber knob) inhibited HAdV-D56 infection, and surface plasmon analyses demonstrated that CD46 binds to HAdV-D hexon (but not fiber knob) proteins. Cryoelectron microscopy analysis of the HAdV-D56 virion-CD46 complex confirmed the interaction and showed that CD46 binds to the central cavity of hexon trimers. Finally, soluble CD46 inhibited infection by 16 out of 17 investigated HAdV-D types, suggesting that CD46 is an important receptor for a large group of adenoviruses. In conclusion, this study identifies a noncanonical entry mechanism used by human adenoviruses, which adds to the knowledge of adenovirus biology and can also be useful for development of adenovirus-based vaccine vectors.
人腺病毒 D 型（HAdV-D）目前正在被探索作为 2019 年冠状病毒病（COVID-19）和其他严重传染病的疫苗载体。这种基于载体的疫苗的功效取决于与宿主细胞上受体的功能相互作用。不同种属的腺病毒被认为主要通过突出纤维衣壳蛋白的球状结构域与细胞受体之间的相互作用进入宿主细胞。我们使用基于细胞的受体筛选测定法，鉴定出 CD46 是 HAdV-D56 的受体。在使用缺乏和过表达 CD46 的细胞进行感染实验以及使用可溶性 CD46 进行竞争感染实验中，验证了 CD46 的功能。值得注意的是，与通过与纤维蛋白的球状结构域相互作用结合 CD46 的 HAdV-B 型不同，HAdV-D 型通过 CD46 与六邻体蛋白之间的直接相互作用感染宿主细胞。可溶性六邻体蛋白（而非纤维蛋白球状结构域）抑制了 HAdV-D56 的感染，表面等离子体共振分析表明 CD46 结合 HAdV-D 的六邻体（而非纤维蛋白球状结构域）蛋白。HAdV-D56 病毒粒子-CD46 复合物的低温电子显微镜分析证实了这种相互作用，并表明 CD46 结合六邻体三聚体的中央腔。最后，可溶性 CD46 抑制了 17 种研究的 HAdV-D 型中的 16 种的感染，表明 CD46 是一大组腺病毒的重要受体。总之，本研究确定了人腺病毒使用的非典型进入机制，这增加了对腺病毒生物学的认识，也可用于基于腺病毒的疫苗载体的开发。
