Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
J Virol Methods. 2013 Oct;193(1):215-25. doi: 10.1016/j.jviromet.2013.06.003. Epub 2013 Jun 10.
The lack of a permissive cell culture system hampers the study of human parvovirus B19 (B19V). UT7/Epo is one of the few established cell lines that can be infected with B19V but generates none or few infectious progeny. Recently, hypoxic conditions or the use of primary CD36+ erythroid progenitor cells (CD36+ EPCs) have been shown to improve the infection. These novel approaches were evaluated in infection and transfection experiments. Hypoxic conditions or the use of CD36+ EPCs resulted in a significant acceleration of the infection/transfection and a modest increase in the yield of capsid progeny. However, under all tested conditions, genome encapsidation was impaired seriously. Further analysis of the cell culture virus progeny revealed that differently to the wild-type virus, the VP1 unique region (VP1u) was exposed partially and was unable to become further externalized upon heat treatment. The fivefold axes pore, which is used for VP1u externalization and genome encapsidation, might be constricted by the atypical VP1u conformation explaining the packaging failure. Although CD36+ EPCs and hypoxia facilitate B19V infection, large quantities of infectious progeny cannot be generated due to a failure in genome encapsidation, which arises as a major limiting factor for the in vitro propagation of B19V.
缺乏许可的细胞培养系统阻碍了人类细小病毒 B19（B19V）的研究。UT7/Epo 是少数几种可以被 B19V 感染但产生很少或几乎没有感染性后代的已建立细胞系之一。最近，缺氧条件或使用原代 CD36+红系祖细胞（CD36+EPC）已被证明可以改善感染。这些新方法在感染和转染实验中进行了评估。缺氧条件或使用 CD36+EPC 可显著加速感染/转染，并适度增加衣壳后代的产量。然而，在所有测试的条件下，基因组包装都受到严重损害。对细胞培养病毒后代的进一步分析表明，与野生型病毒不同，VP1 独特区（VP1u）部分暴露，并且在热处理后无法进一步外化。用于 VP1u 外化和基因组包装的五倍轴孔可能因非典型的 VP1u 构象而收缩，这解释了包装失败的原因。尽管 CD36+EPC 和缺氧促进了 B19V 的感染，但由于基因组包装失败，无法产生大量的感染性后代，这成为 B19V 体外繁殖的主要限制因素。
