Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, USA.
Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, USA.
Vet Microbiol. 2020 Dec;251:108911. doi: 10.1016/j.vetmic.2020.108911. Epub 2020 Nov 1.
Marek's disease virus (MDV) genome contains a number of uncharacterized long open reading frames (LORF) and their role in viral pathogenesis has not been fully investigated. Among them, LORF9 (MDV069) and LORF10 (MDV071) are locate at the right terminus of the MDV genome unique long region (U). To investigate their role in MDV pathogenesis, we generated LORF9 or LORF10 deletion and revertant viruses. In vitro growth kinetics results show that both LORF9 and LORF10 are not essential for virus growth in cell culture. However, LORF9, but not LORF10, is involved in MDV early cytolytic replication in vivo, as evidenced by limited viral antigen expression in lymphoid organs of LORF9 deletion virus inoculated chickens. MDV genome copy number data further confirmed that LORF9 is important for MDV replication in spleen during early cytolytic phase. Deletion of LORF9 also partially impairs the replication of MDV in feather follicle epithelium (FFE); however, it can still establish latency and transformation. In addition, pathogenesis studies show that deletion of LORF9, but not LORF10, result in significant reduction of MDV induced mortality and slightly reduce MDV associated tumors of inoculated chickens. Importantly, we confirmed these results with the generation of LORF9 and LORF10 revertant viruses that fully restore the phenotypes of parental MDV. In conclusion, our results show that deletion of LORF9, but not LORF10, significantly impair viral replication in lymphoid organs during early cytolytic phase and attenuate Marek's disease virus pathogenesis.
马立克氏病病毒（MDV）基因组包含许多未被描述的长开放阅读框（LORF），其在病毒发病机制中的作用尚未得到充分研究。其中，LORF9（MDV069）和 LORF10（MDV071）位于 MDV 基因组独特长区（U）的右端。为了研究它们在 MDV 发病机制中的作用，我们生成了 LORF9 或 LORF10 缺失和回复病毒。体外生长动力学结果表明，LORF9 和 LORF10 对于病毒在细胞培养中的生长都不是必需的。然而，LORF9 而不是 LORF10 参与了 MDV 在体内的早期细胞溶解性复制，这一点可以从 LORF9 缺失病毒接种鸡的淋巴器官中有限的病毒抗原表达中得到证明。MDV 基因组拷贝数数据进一步证实，LORF9 对于 MDV 在早期细胞溶解阶段脾脏中的复制很重要。LORF9 的缺失也部分损害了 MDV 在羽毛滤泡上皮（FFE）中的复制；然而，它仍然可以建立潜伏和转化。此外，发病机制研究表明，LORF9 的缺失而不是 LORF10 的缺失导致 MDV 诱导的死亡率显著降低，接种鸡的 MDV 相关肿瘤略有减少。重要的是，我们通过生成 LORF9 和 LORF10 回复病毒来证实了这些结果，这些病毒完全恢复了亲本 MDV 的表型。总之，我们的结果表明，LORF9 的缺失而不是 LORF10 的缺失，显著损害了早期细胞溶解阶段淋巴器官中的病毒复制，并减弱了马立克氏病病毒的发病机制。
