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Abstract：
Human cytomegalovirus (HCMV) displays a broad cell tropism, and the infection of biologically relevant cells such as epithelial, endothelial, and hematopoietic cells supports viral transmission, systemic spread, and pathogenesis in the human host. HCMV strains differ in their ability to infect and replicate in these cell types, but the genetic basis of these differences has remained incompletely understood. In this study, we investigated HCMV strain VR1814, which is highly infectious for epithelial cells and macrophages and induces cell-cell fusion in both cell types. A VR1814-derived bacterial artificial chromosome (BAC) clone, FIX-BAC, was generated many years ago but has fallen out of favor because of its modest infectivity. By sequence comparison and genetic engineering of FIX, we demonstrate that the high infectivity of VR1814 and its ability to induce syncytium formation in epithelial cells and macrophages depends on VR1814-specific variants of the envelope glycoproteins gB, UL128, and UL130. We also show that UL130-neutralizing antibodies inhibit syncytium formation, and a FIX-specific mutation in UL130 is responsible for its low infectivity by reducing the amount of the pentameric glycoprotein complex in viral particles. Moreover, we found that a VR1814-specific mutation in US28 further increases viral infectivity in macrophages, possibly by promoting lytic rather than latent infection of these cells. Our findings show that variants of gB and the pentameric complex are major determinants of infectivity and syncytium formation in epithelial cells and macrophages. Furthermore, the VR1814-adjusted FIX strains can serve as valuable tools to study HCMV infection of myeloid cells.IMPORTANCEHuman cytomegalovirus (HCMV) is a major cause of morbidity and mortality in transplant patients and the leading cause of congenital infections. HCMV infects various cell types, including epithelial cells and macrophages, and some strains induce the fusion of neighboring cells, leading to the formation of large multinucleated cells called syncytia. This process may limit the exposure of the virus to host immune factors and affect pathogenicity. However, the reason why some HCMV strains exhibit a broader cell tropism and why some induce cell fusion more than others is not well understood. We compared two closely related HCMV strains and provided evidence that small differences in viral envelope glycoproteins can massively increase or decrease the virus infectivity and its ability to induce syncytium formation. The results of the study suggest that natural strain variations may influence HCMV infection and pathogenesis in humans.
摘要：
人巨细胞病毒（HCMV）表现出广泛的细胞嗜性，和生物相关细胞如上皮细胞的感染，内皮，造血细胞支持病毒传播，系统传播，以及在人类宿主中的发病机制。HCMV菌株在这些细胞类型中感染和复制的能力不同，但是这些差异的遗传基础还没有完全理解。在这项研究中,我们研究了HCMV株VR1814，它对上皮细胞和巨噬细胞具有高度传染性，并在两种细胞类型中诱导细胞-细胞融合。VR1814来源的细菌人工染色体（BAC）克隆，FIX-BAC,是多年前产生的，但由于其适度的传染性而失宠。通过序列比较和基因工程的FIX，我们证明VR1814的高感染性及其在上皮细胞和巨噬细胞中诱导合胞体形成的能力取决于包膜糖蛋白gB的VR1814特异性变体，UL128和UL130。我们还显示UL130中和抗体抑制合胞体形成，UL130中的FIX特异性突变通过减少病毒颗粒中五聚体糖蛋白复合物的量而导致其低感染性。此外，我们发现US28中的VR1814特异性突变进一步增加了巨噬细胞中的病毒感染性，可能是通过促进这些细胞的裂解而不是潜伏感染。我们的发现表明，gB和五聚体复合物的变体是上皮细胞和巨噬细胞中感染性和合胞体形成的主要决定因素。此外，VR1814调整的FIX菌株可以作为研究HCMV感染骨髓细胞的有价值的工具。人类巨细胞病毒（HCMV）是移植患者发病和死亡的主要原因，也是先天性感染的主要原因。HCMV感染各种细胞类型，包括上皮细胞和巨噬细胞,一些菌株诱导邻近细胞的融合，导致形成称为合胞体的大型多核细胞。此过程可能会限制病毒对宿主免疫因子的暴露并影响致病性。然而,一些HCMV毒株表现出更广泛的细胞嗜性的原因以及为什么一些毒株比其他毒株更多地诱导细胞融合的原因尚不清楚。我们比较了两种密切相关的HCMV毒株，并提供了证据表明病毒包膜糖蛋白的微小差异可以大量增加或减少病毒的感染性及其诱导合胞体形成的能力。研究结果表明，自然菌株变异可能会影响人类HCMV感染和发病机理。
