Paez E, Dallo S, Esteban M
J Virol. 1987 Aug;61(8):2642-7. doi: 10.1128/JVI.61.8.2642-2647.1987.
To investigate the genetic stability of vaccinia virus DNA, we have tested whether alterations occurred in the polypeptide composition of this complex virus during persistent infections. We found that variants isolated at various passages in Friend erythroleukemia cells persistently infected with vaccinia virus contained, in addition to an 8-megadalton (MDa) deletion on the left terminus of the viral genome, major alterations in the sizes of three structural proteins with molecular masses of about 39, 21, and 14 kDa. Alterations in isoelectric points were also observed in proteins of 48, 27, and 14 kDa. The 14-kDa protein is part of the virus envelope, and the variants increased the size of this protein from 0.5 to 3 kDa with increasing passage number. Alteration in size of the 14-kDa protein is a dominant trait since it appeared in the whole virus population by passage 48. With more passages, some variants were found to increase or decrease the size of a 39-kDa core protein by about 2 kDa and to decrease the size of an envelope protein of 21 kDa by about 2 kDa. These three proteins were immunogenic in mice and elicited a strong host immune response. Major alterations in the sizes of these proteins were prevented by continuous treatment of the persistently infected cultures with interferon. However, after interferon was removed, protein modifications appeared with increasing passage number. Generation of the 8-MDa deletion and alterations in the size of the 14-kDa protein correlated with a marked decrease in virulence of these variants. Our findings suggest that during virus persistence, specific mutations are introduced in the vaccinia virus genome that lead to protein alterations and to highly attenuated viruses.
为了研究痘苗病毒DNA的遗传稳定性，我们测试了这种复合病毒在持续感染期间其多肽组成是否发生改变。我们发现，从持续感染痘苗病毒的弗氏红白血病细胞的不同传代中分离出的变体，除了病毒基因组左末端有一个8兆道尔顿（MDa）的缺失外，三种分子量约为39、21和14 kDa的结构蛋白的大小也有重大改变。在48、27和14 kDa的蛋白质中也观察到了等电点的改变。14 kDa的蛋白质是病毒包膜的一部分，随着传代次数的增加，这些变体使该蛋白质的大小从0.5 kDa增加到3 kDa。14 kDa蛋白质大小的改变是一个显性特征，因为在第48代时它出现在整个病毒群体中。随着传代次数的增加，一些变体被发现使一种39 kDa的核心蛋白的大小增加或减少约2 kDa，并使一种21 kDa的包膜蛋白的大小减少约2 kDa。这三种蛋白质在小鼠中具有免疫原性，并引发强烈的宿主免疫反应。用干扰素持续处理持续感染的培养物可防止这些蛋白质大小的重大改变。然而，去除干扰素后，随着传代次数的增加，蛋白质修饰出现了。8-MDa缺失的产生和14 kDa蛋白质大小的改变与这些变体的毒力显著降低相关。我们的研究结果表明，在病毒持续存在期间，痘苗病毒基因组中引入了特定的突变，导致蛋白质改变并产生高度减毒的病毒。
