Thacore H, Youngner J S
J Virol. 1970 Jul;6(1):42-8. doi: 10.1128/JVI.6.1.42-48.1970.
A comparison of the replication patterns in L cells and in chick embryo (CE) cell cultures was carried out with the Herts strain of Newcastle disease virus (NDV(o)) and with a mutant (NDV(pi)) isolated from persistently infected L cells. A significant amount of virus progeny, 11 plaque-forming units (PFU)/cell, was synthesized in L cells infected with NDV(o), but the infectivity remained cell-associated and disappeared without being detectable in the medium. In contrast, in L cells infected with NDV(pi), progeny virus (30 PFU/cell) was released efficiently upon maturation. It is suggested that the term "covert" rather than "abortive" be used to describe the infection of L cells with NDV(o). In both L and CE cells, the latent period of NDV(pi) was 2 to 4 hr longer than for NDV(o). The delay in synthesis of viral ribonucleic acid (RNA) in the case of NDV(pi) coincided with the delay in the inhibition of host RNA and protein synthesis. Although both NDV(o) and NDV(pi) produced more progeny and more severe cell damage in CE cells than in L cells, the shut-off of host functions was significantly less efficient in CE cells than in L cells. Paradoxically, no detectable interferon was produced in CE cells by either of the viruses, whereas in L cells most of the interferon appeared in the medium after more than 90% of host protein synthesis was inhibited. These results suggest that the absence of induction of interferon synthesis in CE cells infected with NDV is not related to the general shut-off of host cell synthetic mechanisms but rather to the failure of some more specific event to occur. In spite of the fact that NDV(pi) RNA synthesis commenced 2 to 4 hr later than that of NDV(o), interferon was first detected in the medium 8 hr after infection with both viruses. This finding suggests that there is no relation between viral RNA synthesis and the induction of interferon synthesis.
用新城疫病毒（NDV(o)）的赫茨毒株和从持续感染的L细胞中分离出的一种突变株（NDV(pi)），对L细胞和鸡胚（CE）细胞培养物中的复制模式进行了比较。在感染NDV(o)的L细胞中合成了大量病毒子代，每细胞11个空斑形成单位（PFU），但感染性仍与细胞相关，在培养基中未检测到其消失。相比之下，在感染NDV(pi)的L细胞中，子代病毒（每细胞30 PFU）在成熟时有效释放。有人建议用“隐性”而非“流产性”来描述NDV(o)对L细胞的感染。在L细胞和CE细胞中，NDV(pi)的潜伏期都比NDV(o)长2至4小时。NDV(pi)情况下病毒核糖核酸（RNA）合成的延迟与宿主RNA和蛋白质合成抑制的延迟相一致。尽管NDV(o)和NDV(pi)在CE细胞中产生的子代比在L细胞中更多，对细胞的损伤也更严重，但CE细胞中宿主功能的关闭效率明显低于L细胞。矛盾的是，两种病毒在CE细胞中都未产生可检测到的干扰素，而在L细胞中，在超过90%的宿主蛋白质合成被抑制后，大部分干扰素出现在培养基中。这些结果表明，感染NDV的CE细胞中未诱导干扰素合成与宿主细胞合成机制的普遍关闭无关，而是与某些更特定事件未能发生有关。尽管NDV(pi)的RNA合成比NDV(o)晚2至4小时开始，但两种病毒感染后8小时均可在培养基中首次检测到干扰素。这一发现表明病毒RNA合成与干扰素合成的诱导之间没有关系。
