Poole Emma, Schmitt Janika, Graham Stephen C, Kelly Bernard T, Sinclair John
Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK.
Department of Pathology, Division of Virology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK.
Pathogens. 2024 Sep 24;13(10):821. doi: 10.3390/pathogens13100821.
After primary infection, human cytomegalovirus (HCMV) establishes lifelong persistence, underpinned by latent carriage of the virus with spontaneous reactivation events. In the immune-competent, primary infection or reactivation from latency rarely causes disease. However, HCMV can cause significant disease in immune-compromised individuals such as immune-suppressed transplant patients. Latency, where the viral genome is carried in the absence of the production of infectious virions, can be established in undifferentiated cells of the myeloid lineage. A number of stimuli can cause virus reactivation from latency to occur, beginning with the induction of viral immediate-early (IE) lytic gene expression. The suppression of viral IE gene expression to establish and maintain latent infection is known to result from a balance of viral and cellular factors. One key viral factor involved in this is the G protein-coupled receptor US28. Recently, we have shown that US28 is targeted for degradation by a modified nanobody (PCTD-Vun100bv) based on the novel PACTAC (PCSK9-antibody clearance-targeting chimeras) approach for targeted protein degradation. Furthermore, we have shown that this PCTD-Vun100bv-induced degradation of US28 results in IE gene expression in experimentally latently infected CD14+ monocytes. However, HCMV also establishes latency in CD34+ bone marrow cells, the progenitors of CD14+ cells. Here, we show that PCTD-Vun100bv also causes US28 degradation in these CD34+ primary cells, again resulting in the induction of viral IE gene expression. Additionally, we show that PCTD-Vun100bv can target US28 in naturally latently infected CD14+ monocytes from an HCMV-seropositive donor, allowing these latently infected cells to be killed by HCMV-specific cytotoxic T cells from that same donor. These observations support the view that targeting US28 for degradation during natural latency could be a tractable 'shock-and-kill' strategy to target the latent HCMV reservoir in myeloid cells.
初次感染后，人类巨细胞病毒（HCMV）会建立终身持续性感染，其基础是病毒的潜伏携带以及自发再激活事件。在免疫功能正常的个体中，初次感染或潜伏状态的再激活很少引发疾病。然而，HCMV可在免疫功能受损的个体中导致严重疾病，如免疫抑制的移植患者。潜伏期是指病毒基因组在不产生传染性病毒粒子的情况下被携带，可在髓系谱系的未分化细胞中建立。许多刺激因素可导致病毒从潜伏状态重新激活，首先是诱导病毒即刻早期（IE）裂解基因的表达。已知病毒IE基因表达的抑制以建立和维持潜伏感染是病毒和细胞因子平衡的结果。其中一个关键的病毒因子是G蛋白偶联受体US28。最近，我们已经表明，基于新型PACTAC（PCSK9抗体清除靶向嵌合体）方法进行靶向蛋白降解，US28可被一种修饰的纳米抗体（PCTD-Vun100bv）靶向降解。此外，我们已经表明，PCTD-Vun100bv诱导的US28降解会导致实验性潜伏感染的CD14+单核细胞中IE基因的表达。然而，HCMV也会在CD34+骨髓细胞（CD14+细胞的祖细胞）中建立潜伏感染。在这里，我们表明PCTD-Vun100bv也会导致这些CD34+原代细胞中US28的降解，同样导致病毒IE基因表达的诱导。此外，我们表明PCTD-Vun100bv可以靶向来自HCMV血清阳性供体的自然潜伏感染的CD14+单核细胞中的US28，使这些潜伏感染的细胞被来自同一供体的HCMV特异性细胞毒性T细胞杀死。这些观察结果支持这样一种观点，即在自然潜伏期将US28靶向降解可能是一种针对髓系细胞中潜伏HCMV储存库的可行的“休克并杀伤”策略。
