Laboratory of Biology of Avian Viruses, INRAE-Université de Tours, Nouzilly, France.
J Virol. 2023 May 31;97(5):e0024223. doi: 10.1128/jvi.00242-23. Epub 2023 May 8.
pUL51 is a minor tegument protein important for viral assembly and cell-to-cell spread (CCS) but dispensable for replication in cell culture of all Herpesviruses for which its role has been investigated. Here, we show that pUL51 is essential for the growth of Marek's disease virus, an oncogenic alphaherpesvirus of chickens that is strictly cell-associated in cell culture. MDV pUL51 localized to the Golgi apparatus of infected primary skin fibroblasts, as described for other Herpesviruses. However, the protein was also observed at the surface of lipid droplets in infected chicken keratinocytes, hinting at a possible role of this compartment for viral assembly in the unique cell type involved in MDV shedding Deletion of the C-terminal half of pUL51 or fusion of GFP to either the N- or C-terminus were sufficient to disable the protein's essential function(s). However, a virus with a TAP domain fused at the C-terminus of pUL51 was capable of replication in cell culture, albeit with viral spread reduced by 35% and no localization to lipid droplets. , we observed that although the replication of this virus was moderately impacted, its pathogenesis was strongly impaired. This study describes for the first time the essential role of pUL51 in the biology of a herpesvirus, its association to lipid droplets in a relevant cell type, and its unsuspected role in the pathogenesis of a herpesvirus in its natural host. Viruses usually spread from cell to cell through two mechanisms: cell-released virus and/or cell-to-cell spread (CCS). The molecular determinants of CCS and their importance in the biology of viruses during infection of their natural host are unclear. Marek's disease virus (MDV) is a deadly and highly contagious herpesvirus of chickens that produces no cell-free particles , and therefore, spreads only through CCS in cell culture. Here, we show that viral protein pUL51, an important factor for CCS of Herpesviruses, is essential for MDV growth . We demonstrate that the fusion of a large tag at the C-terminus of the protein is sufficient to moderately impair viral replication and almost completely abolish pathogenesis while only slightly reducing viral growth . This study thus uncovers a role for pUL51 associated with virulence, linked to its C-terminal half, and possibly independent of its essential functions in CCS.
pUL51 是一种次要的衣壳蛋白，对病毒组装和细胞间传播（CCS）很重要，但在所有已研究过的疱疹病毒的细胞培养中，它对复制是可有可无的。在这里，我们表明 pUL51 对马立克氏病病毒（MDV）的生长是必不可少的，MDV 是一种致瘤的α疱疹病毒，在细胞培养中严格与细胞相关。MDV pUL51 定位于受感染的原代皮肤成纤维细胞的高尔基器，如其他疱疹病毒所述。然而，在受感染的鸡角质形成细胞中，该蛋白也被观察到在脂滴的表面，这暗示了该隔室可能在 MDV 脱落所涉及的独特细胞类型的病毒组装中发挥作用。pUL51 的 C 端缺失或 GFP 与 N 或 C 端融合足以使该蛋白的必需功能失活。然而，一种在 pUL51 的 C 端融合 TAP 结构域的病毒能够在细胞培养中复制，尽管病毒传播减少了 35%，且不能定位到脂滴。有趣的是，尽管该病毒的复制受到适度影响，但它的发病机制受到强烈损害。本研究首次描述了 pUL51 在疱疹病毒生物学中的关键作用，它在相关细胞类型中与脂滴的关联，以及它在其天然宿主中的疱疹病毒发病机制中的意外作用。病毒通常通过两种机制从一个细胞传播到另一个细胞：细胞释放的病毒和/或细胞间传播（CCS）。CCS 的分子决定因素及其在病毒感染其自然宿主时的生物学中的重要性尚不清楚。马立克氏病病毒（MDV）是一种致命且高度传染性的鸡疱疹病毒，不产生游离的细胞颗粒，因此，在细胞培养中仅通过 CCS 传播。在这里，我们表明疱疹病毒 CCS 的重要因素 pUL51 对 MDV 的生长是必不可少的。我们证明，在该蛋白的 C 端融合一个大标签足以适度损害病毒复制，并几乎完全消除发病机制，同时仅略微降低病毒生长。因此，本研究揭示了 pUL51 与毒力相关的作用，与它的 C 端部分相关联，可能与其在 CCS 中的必需功能无关。
