Isomura H, Yoshida M, Namba H, Fujiwara N, Ohuchi R, Uno F, Oda M, Seino Y, Yamada M
Departments of Virology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
J Gen Virol. 2000 Mar;81(Pt 3):663-73. doi: 10.1099/0022-1317-81-3-663.
Two clinical observations, the association of human herpesvirus-6 (HHV-6) with delayed engraftment after stem cell transplantation and thrombocytopenia concomitant with exanthema subitum, prompted us to evaluate the suppressive effects of HHV-6 on thrombopoiesis in vitro. Different culture conditions for thrombopoietin (TPO)-inducible colonies in semi-solid matrices were examined. Using cord blood mononuclear cells as the source of haematopoietic progenitors, two types of colonies, megakaryocyte colony-forming units (CFU-Meg) and non-CFU-Meg colonies, were established. The former colonies were identified by the presence of cells with translucent cytoplasm and highly refractile cell membrane, most of which were positive for the CD41 antigen. Although the plating efficiency of both types was much higher under serum-containing conditions than under serum-free conditions, the proportion of CFU-Meg to non-CFU-Meg colonies was consistently higher under serum-free conditions. The plating efficiency of CFU-Meg colonies was doubled by adding stem cell factor to the serum-free matrix. The effects of two variants of HHV-6 (HHV-6A and 6B) and human herpesvirus-7 (HHV-7) on TPO-inducible colonies were then compared. HHV-6B inhibited both CFU-Meg and non-CFU-Meg colony formation under serum-free and serum-containing conditions. HHV-6A had similar inhibitory effects. In contrast, HHV-7 had no effect on TPO-inducible colony formation. Heat-inactivation and ultra-filtration of the virus sample completely abolished the suppressive effect. After infection of CD34(+) cells with HHV-6, the viral genome was consistently detected by in situ hybridization. These data suggest that the direct effect of HHV-6 on haematopoietic progenitors is one of the major causes of the suppression of thrombopoiesis.
两项临床观察结果，即人类疱疹病毒6型（HHV-6）与干细胞移植后植入延迟的关联以及与幼儿急疹伴随的血小板减少症，促使我们评估HHV-6在体外对血小板生成的抑制作用。我们研究了半固体基质中血小板生成素（TPO）诱导集落的不同培养条件。以脐血单个核细胞作为造血祖细胞来源，建立了两种类型的集落，巨核细胞集落形成单位（CFU-Meg）和非CFU-Meg集落。前者集落通过具有半透明细胞质和高折光性细胞膜的细胞来鉴定，其中大多数CD41抗原呈阳性。尽管两种类型在含血清条件下的接种效率均远高于无血清条件下，但在无血清条件下CFU-Meg集落与非CFU-Meg集落的比例始终更高。通过向无血清基质中添加干细胞因子，CFU-Meg集落的接种效率提高了一倍。然后比较了HHV-6的两种变体（HHV-6A和6B）以及人类疱疹病毒7型（HHV-7）对TPO诱导集落的影响。HHV-6B在无血清和含血清条件下均抑制CFU-Meg和非CFU-Meg集落形成。HHV-6A具有类似的抑制作用。相比之下，HHV-7对TPO诱导的集落形成没有影响。病毒样本的热灭活和超滤完全消除了抑制作用。用HHV-6感染CD34(+)细胞后，通过原位杂交始终能检测到病毒基因组。这些数据表明，HHV-6对造血祖细胞的直接作用是血小板生成受抑制的主要原因之一。
