Department of Biochemistry and Molecular Biology, Center for Structural Biology, College of Medicine, University of Florida, Gainesville, FL 32610, USA.
Biological Science Imaging Resource, Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, USA.
Viruses. 2021 Feb 20;13(2):330. doi: 10.3390/v13020330.
Human bocavirus 1 (HBoV1) has gained attention as a gene delivery vector with its ability to infect polarized human airway epithelia and 5.5 kb genome packaging capacity. Gorilla bocavirus 1 (GBoV1) VP3 shares 86% amino acid sequence identity with HBoV1 but has better transduction efficiency in several human cell types. Here, we report the capsid structure of GBoV1 determined to 2.76 Å resolution using cryo-electron microscopy (cryo-EM) and its interaction with mouse monoclonal antibodies (mAbs) and human sera. GBoV1 shares capsid surface morphologies with other parvoviruses, with a channel at the 5-fold symmetry axis, protrusions surrounding the 3-fold axis and a depression at the 2-fold axis. A 2/5-fold wall separates the 2-fold and 5-fold axes. Compared to HBoV1, differences are localized to the 3-fold protrusions. Consistently, native dot immunoblots and cryo-EM showed cross-reactivity and binding, respectively, by a 5-fold targeted HBoV1 mAb, 15C6. Surprisingly, recognition was observed for one out of three 3-fold targeted mAbs, 12C1, indicating some structural similarity at this region. In addition, GBoV1, tested against 40 human sera, showed the similar rates of seropositivity as HBoV1. Immunogenic reactivity against parvoviral vectors is a significant barrier to efficient gene delivery. This study is a step towards optimizing bocaparvovirus vectors with antibody escape properties.
人博卡病毒 1（HBoV1）因其能够感染极化的人呼吸道上皮细胞和 5.5 kb 基因组包装能力而引起关注，成为一种基因传递载体。大猩猩博卡病毒 1（GBoV1）VP3 与 HBoV1 的氨基酸序列同一性为 86%，但在几种人类细胞类型中具有更好的转导效率。在这里，我们报告了使用冷冻电镜（cryo-EM）测定的 GBoV1 衣壳结构，分辨率为 2.76 Å，及其与小鼠单克隆抗体（mAbs）和人血清的相互作用。GBoV1 与其他细小病毒在衣壳表面形态上具有相似性，在 5 倍对称轴上有一个通道，在 3 倍对称轴周围有突起，在 2 倍对称轴上有一个凹陷。2/5 倍壁将 2 倍和 5 倍对称轴隔开。与 HBoV1 相比，差异局限于 3 倍突起。同样，天然点免疫印迹和 cryo-EM 分别显示了 5 倍靶向 HBoV1 mAb 15C6 的交叉反应性和结合，令人惊讶的是，三种 3 倍靶向 mAb 之一 12C1 观察到识别，表明该区域存在一些结构相似性。此外，在 40 个人血清中测试 GBoV1 时，与 HBoV1 相比，其血清阳性率相似。针对细小病毒载体的免疫反应性是有效基因传递的一个重大障碍。本研究是朝着优化具有抗体逃逸特性的 bocaparvovirus 载体迈出的一步。
