Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany.
Institute for Transfusion Medicine, Ulm University Medical Center, 89081 Ulm, Germany.
Viruses. 2018 Sep 14;10(9):500. doi: 10.3390/v10090500.
Immunoglobulins are only moderately effective for the treatment of human cytomegalovirus (HCMV) infections, possibly due to ineffectiveness against cell-associated virus spread. To overcome this limitation, we aimed to identify individuals with exceptional antibodies in their plasma that can efficiently block the cell-associated spread of HCMV. A Gaussia luciferase-secreting mutant of the cell-associated HCMV strain Merlin was generated, and luciferase activity evaluated as a readout for the extent of cell-associated focal spread. This reporter virus-based assay was then applied to screen plasma samples from 8400 HCMV-seropositive individuals for their inhibitory effect, including direct-acting antiviral drugs as positive controls. None of the plasmas reduced virus spread to the level of these controls. Even the top-scoring samples that partially reduced luciferase activity in the screening assay failed to inhibit focal growth when reevaluated with a more accurate, immunofluorescence-based assay. Selected sera with high neutralizing capacity against free viruses were analyzed separately, and none of them prevented the focal spread of three recent clinical HCMV isolates nor reduced the number of particles transmitted, as demonstrated with a fluorescent Merlin mutant. We concluded that donors with cell-to-cell-spread-inhibiting plasma are nonexistent or extremely rare, emphasizing cell-associated spread as a highly efficient immune escape mechanism of HCMV.
免疫球蛋白对人巨细胞病毒（HCMV）感染的治疗效果仅为中等，这可能是由于其对细胞相关病毒传播的无效。为了克服这一限制，我们旨在鉴定出其血浆中具有特殊抗体的个体，这些抗体能够有效地阻断 HCMV 的细胞相关传播。生成了一种细胞相关 HCMV 株 Merlin 的 Gaussia 荧光素酶分泌突变体，并将荧光素酶活性评估为细胞相关局灶性传播程度的读出值。然后，应用该基于报告病毒的测定法从 8400 名 HCMV 血清阳性个体的血浆样本中筛选出具有抑制作用的个体，包括直接作用的抗病毒药物作为阳性对照。没有一种血浆能将病毒传播降低到这些对照的水平。即使在筛选试验中部分降低荧光素酶活性的得分最高的样本，当用更准确的免疫荧光测定法重新评估时，也未能抑制焦点生长。分别分析了具有高中和能力的游离病毒的选定血清，并且没有一种能够阻止三种最近的临床 HCMV 分离株的局灶性传播，也没有减少如用荧光 Merlin 突变体所证明的那样传播的颗粒数量。我们得出结论，不存在或极为罕见具有细胞间传播抑制作用的血浆供体，这强调了细胞相关传播是 HCMV 非常有效的免疫逃逸机制。
