Woodward C G, Marshall I D, Smith H
Br J Exp Pathol. 1977 Dec;58(6):616-24.
A strain of Semliki Forest virus (A7) which is avirulent in adult mice killed baby mice in a similar manner to strain V13 which was also virulent for adult mice. In the muscle and brains of baby mice A7 and V13 replicated and produced haemagglutinating activity similarly. Our previous suggestion that defective interfering particles were present in the brains of A7-infected adult mice appears not to be so. The interference formerly detected was due to an inhibitor present in brain tissue of adult and baby mice both normal and infected. Homogenates of A7-infected adult brain produced normal RNA species in BHK cells and not those characteristic of defective interfering particles. Organ culture experiments indicated that avirulence of A7 was not due to lack of release of virus from infected adult brain cells. Also, A7 as well as V13 was detected and was probably replicating in all parts of the brain and spinal cord that were sectioned and examined. Evidence is presented that suggests that the reason for the avirulence of A7 for adult mice compared with its virulence for baby mice may relate to a lower ability to replicate in brain tissue per se rather than to interaction with host defence mechanisms.
一种对成年小鼠无毒力的塞姆利基森林病毒毒株（A7），以与对成年小鼠也有毒力的V13毒株相似的方式杀死幼鼠。在幼鼠的肌肉和大脑中，A7和V13的复制情况以及产生血凝活性的情况相似。我们之前提出的关于A7感染的成年小鼠大脑中存在缺陷干扰颗粒的观点似乎并不成立。之前检测到的干扰是由于正常和感染的成年及幼鼠脑组织中存在的一种抑制剂。A7感染的成年大脑匀浆在BHK细胞中产生正常的RNA种类，而非缺陷干扰颗粒特有的RNA种类。器官培养实验表明，A7的无毒力并非由于病毒从感染的成年脑细胞中释放不足。此外，在切片检查的大脑和脊髓的所有部位都检测到了A7以及V13，它们可能正在复制。有证据表明，与A7对幼鼠的毒力相比，其对成年小鼠无毒力的原因可能与在脑组织本身中较低的复制能力有关，而非与宿主防御机制的相互作用有关。
