Li Jiali, Lad Sonya, Yang Guang, Luo Yunping, Iacobelli-Martinez Milena, Primus F James, Reisfeld Ralph A, Li Erguang
Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
J Virol. 2006 Dec;80(24):12324-31. doi: 10.1128/JVI.01331-06. Epub 2006 Oct 4.
Adenoviral (Ad) vectors have been widely used in human gene therapy clinical trials. However, their application has frequently been restricted by the unfavorable expression of cell surface receptors critical for Ad infection. Infections by Ad2 and Ad5 are largely regulated by the elongated fiber protein that mediates its attachment to a cell surface receptor, coxsackie and adenovirus receptor (CAR). The fiber protein is a homotrimer consisting of an N-terminal tail, a long shaft, and a C-terminal knob region that is responsible for high-affinity receptor binding and Ad tropism. Consequently, the modification of the knob region, including peptide insertion and C-terminal fusion of ligands for cell surface receptors, has become a major research focus for targeting gene delivery. Such manipulation tends to disrupt fiber assembly since the knob region contains a stabilization element for fiber trimerization. We report here the identification of a novel trimerization element in the Ad fiber shaft. We demonstrate that fiber fragments containing the N-terminal tail and shaft repeats formed stable trimers that assembled onto Ad virions independently of the knob region. This fiber shaft trimerization element (FSTE) exhibited a capacity to support peptide fusion. We showed that Ad, modified with a chimeric protein by direct fusion of the FSTE with a growth factor ligand or a single-chain antibody, delivered a reporter gene selectively. Together, these results indicate that the shaft region of Ad fiber protein contains a trimerization element that allows ligand fusion, which potentially broadens the basis for Ad vector development.
腺病毒（Ad）载体已广泛应用于人类基因治疗临床试验。然而，其应用常常受到对Ad感染至关重要的细胞表面受体表达不佳的限制。Ad2和Ad5的感染在很大程度上受细长的纤维蛋白调控，该纤维蛋白介导其与细胞表面受体柯萨奇病毒和腺病毒受体（CAR）的附着。纤维蛋白是一种同三聚体，由N端尾部、长杆部和C端球状结构域组成，C端球状结构域负责高亲和力受体结合和Ad嗜性。因此，球状结构域的修饰，包括肽插入和细胞表面受体配体的C端融合，已成为靶向基因递送的主要研究重点。由于球状结构域包含纤维三聚化的稳定元件，这种操作往往会破坏纤维组装。我们在此报告在Ad纤维杆中鉴定出一种新型三聚化元件。我们证明，包含N端尾部和杆重复序列的纤维片段形成了稳定的三聚体，这些三聚体独立于球状结构域组装到Ad病毒粒子上。这种纤维杆三聚化元件（FSTE）表现出支持肽融合的能力。我们表明，通过将FSTE与生长因子配体或单链抗体直接融合用嵌合蛋白修饰的Ad能选择性地递送报告基因。总之，这些结果表明Ad纤维蛋白的杆区域包含一个允许配体融合的三聚化元件，这可能拓宽了Ad载体开发的基础。
