Perng G C, Thompson R L, Sawtell N M, Taylor W E, Slanina S M, Ghiasi H, Kaiwar R, Nesburn A B, Wechsler S L
Ophthalmology Research Laboratories, Cedars-Sinai Medical Center Research Institute, Los Angeles 90048, USA.
J Virol. 1995 May;69(5):3033-41. doi: 10.1128/JVI.69.5.3033-3041.1995.
The herpes simplex virus type 1 (HSV-1) ICP34.5 gene is a neurovirulence gene in mice. In addition, some ICP34.5 mutants have been reported to have a reduced efficiency of induced reactivation as measured by in vitro explantation of latently infected mouse ganglia. However, since spontaneous reactivation is almost nonexistent in mice, nothing has been reported on the effect of ICP34.5 mutants on spontaneous reactivation in vivo. To examine this, we have deleted both copies of the ICP34.5 neurovirulence gene from a strain of HSV-1 (McKrae) that has a high spontaneous reactivation rate in rabbits and used this mutant to infect rabbit eyes. All rabbits infected with the ICP34.5 mutant virus (d34.5) survived, even at challenge doses greater than 4 x 10(7) PFU per eye. In contrast, a 200-fold-lower challenge dose of 2 x 10(5) PFU per eye was lethal for approximately 50% of rabbits infected with either the wild-type McKrae parental virus or a rescued ICP34.5 mutant in which both copies of the ICP34.5 gene were restored. In mice, the 50% lethal dose of the ICP34.5 mutant was over 10(6) PFU, compared with a value of less than 10 PFU for the rescued virus. The ICP34.5 mutant was restricted for replication in rabbit and mouse eyes and mouse trigeminal ganglia in vivo. The spontaneous reactivation rate in rabbits for the mutant was 1.4% as determined by culturing tear films for the presence of reactivated virus. This was more than 10-fold lower than the spontaneous reactivation rate determined for the rescued virus (19.6%) and was highly significant (P < 0.0001, Fisher exact test). Southern analysis confirmed that the reactivated virus retained both copies of the ICP34.5 deletion. Thus, this report demonstrates that (i) the ICP34.5 gene, known to be a neurovirulence gene in mice, is also important for virulence in rabbits and (ii) in vivo spontaneous reactivation of HSV-1 in the rabbit ocular model, although reduced, can occur in the absence of the ICP34.5 gene.
单纯疱疹病毒1型（HSV-1）的ICP34.5基因是小鼠中的神经毒力基因。此外，据报道一些ICP34.5突变体通过对潜伏感染的小鼠神经节进行体外植块培养来测量，其诱导再激活的效率有所降低。然而，由于小鼠中几乎不存在自发再激活，因此尚未有关于ICP34.5突变体对体内自发再激活影响的报道。为了对此进行研究，我们从一株在兔子中具有高自发再激活率的HSV-1（McKrae）中删除了ICP34.5神经毒力基因的两个拷贝，并使用该突变体感染兔子眼睛。所有感染ICP34.5突变病毒（d34.5）的兔子都存活了下来，即使每只眼睛的攻击剂量大于4×10⁷ PFU。相比之下，每只眼睛2×10⁵ PFU的攻击剂量比野生型McKrae亲本病毒或拯救的ICP34.5突变体（其中ICP34.5基因的两个拷贝都已恢复）低200倍，却能使约50%感染的兔子致死。在小鼠中，ICP34.5突变体的半数致死剂量超过10⁶ PFU，而拯救病毒的半数致死剂量小于10 PFU。ICP34.5突变体在兔子和小鼠眼睛以及小鼠三叉神经节的体内复制受到限制。通过培养泪膜检测再激活病毒的存在，确定该突变体在兔子中的自发再激活率为1.4%。这比拯救病毒的自发再激活率（19.6%）低10倍以上，且差异极显著（P < 0.0001，Fisher精确检验）。Southern分析证实再激活的病毒保留了ICP34.5缺失的两个拷贝。因此，本报告表明：（i）已知在小鼠中是神经毒力基因的ICP34.5基因，对兔子的毒力也很重要；（ii）在兔子眼部模型中，HSV-1的体内自发再激活虽然减少，但在没有ICP34.5基因的情况下也会发生。
