Department of Veterinary Biosciences, The Ohio State University College of Veterinary Medicine, Columbus, Ohio, United States of America.
Biomedical Research Center Battelle Memorial Institute, Columbus, Ohio, United States of America.
PLoS One. 2021 Feb 18;16(2):e0246770. doi: 10.1371/journal.pone.0246770. eCollection 2021.
Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection in infants and young children worldwide. The attachment (G) protein of RSV is synthesized by infected cells in both a membrane bound (mG) and secreted form (sG) and uses a CX3C motif for binding to its cellular receptor. Cell culture and mouse studies suggest that the G protein mimics the cytokine CX3CL1 by binding to CX3CR1 on immune cells, which is thought to cause increased pulmonary inflammation in vivo. However, because these studies have used RSV lacking its G protein gene or blockade of the G protein with a G protein specific monoclonal antibody, the observed reduction in inflammation may be due to reduced virus replication and spread, and not to a direct role for G protein as a viral chemokine. In order to more directly determine the influence of the soluble and the membrane-bound forms of G protein on the immune system independent of its attachment function for the virion, we expressed the G protein in cotton rat lungs using adeno-associated virus (AAV), a vector system which does not itself induce inflammation. We found no increase in pulmonary inflammation as determined by histology and bronchoalveolar lavage after inoculation of AAVs expressing the membrane bound G protein, the secreted G protein or the complete G protein gene which expresses both forms. The long-term low-level expression of AAV-G did, however, result in the induction of non-neutralizing antibodies, CD8 T cells and partial protection from challenge with RSV. Complete protection was accomplished through co-immunization with AAV-G and an AAV expressing cotton rat interferon α.
人类呼吸道合胞病毒（RSV）是全球婴幼儿下呼吸道感染的主要原因。RSV 的附着（G）蛋白由受感染的细胞以膜结合（mG）和分泌形式（sG）合成，并使用 CX3C 基序与其细胞受体结合。细胞培养和小鼠研究表明，G 蛋白通过与免疫细胞上的 CX3CR1 结合模拟细胞因子 CX3CL1，这被认为导致体内肺部炎症增加。然而，由于这些研究使用了缺乏 G 蛋白基因的 RSV 或用 G 蛋白特异性单克隆抗体阻断 G 蛋白，观察到的炎症减少可能是由于病毒复制和传播减少，而不是 G 蛋白作为病毒趋化因子的直接作用。为了更直接地确定可溶性和膜结合形式的 G 蛋白对免疫系统的影响，而不考虑其对病毒粒子的附着功能，我们使用腺相关病毒（AAV）在棉鼠肺部表达 G 蛋白，这是一种不会引起自身炎症的载体系统。我们发现，在接种表达膜结合 G 蛋白、分泌 G 蛋白或表达两种形式的完整 G 蛋白基因的 AAV 后，通过组织学和支气管肺泡灌洗确定的肺部炎症没有增加。然而，AAV-G 的长期低水平表达确实导致了非中和抗体、CD8 T 细胞的诱导，并对 RSV 挑战有部分保护作用。完全保护是通过与 AAV-G 和表达棉鼠干扰素 α 的 AAV 共同免疫来实现的。
