Studies on the mechanisms of persistent infection and reactivation of animal viruses.

在持续感染时，尽管存在免疫力，病毒仍能隐藏在体内，逃避免疫压力。然而，病毒有时会被重新激活，在宿主中产生疾病。主要研究结果如下：1.建立了猫免疫缺陷病毒（FIV）持续感染的体外模型。在感染的MOLT-4细胞中未检测到FIV特异性RNA的表达，表明病毒复制在病毒生命周期的早期阶段被阻断。2.用FIV A亚型（Petaluma株）和FIV B亚型（TM 1株和TM 2株）分别感染3只猫，经8年以上的实验观察，均无特异性病原。感染FIV A亚型的猫在感染后8年8个月死于腹腔积血（p.i.），而FIV亚型B的患者， ...更多信息 临床上健康状况不佳超过9年p.i.。在FIV持续感染中，亚型之间致病性的差异和动物饲养环境是导致艾滋病的重要因素。3.马立克氏病病毒（Marek's diseasevirus，MDV）从血清学和遗传学上可分为3个血清型，均引起鸡的持续感染。MDV-1是致癌的，而MDV-2是非致癌的。为了从基因水平上了解MDV-2持续感染和致瘤的机制，我们对MDV-2的90%以上的基因组进行了测序。4.疱疹病毒的立即早期（immediate-early，IE）基因产物被认为在调节潜伏感染中起重要作用。我们证明，猫疱疹病毒1型（FHV-1）产生一个单一的立即早期（IE）转录编码FHV-1 ICP 4和FHV-1 ICP 4基因的两个启动子交替调节。在两个启动子之间存在一个负调控元件，该元件由一个20 bp的直接重复单元组成。5.建立了CDV Yanaka株持续感染B 95 a细胞株。从该载体培养物中回收的病毒对新鲜B 95 a细胞具有感染性，并且引起持续感染而不显示CPE，该病毒被命名为Yanaka-BP株。免疫沉淀显示相同的分子量的H或F蛋白的Yanaka和Yanaka-BP菌株。F基因的序列分析表明，在Yanaka-BP株中缺少被认为是Onderstepoort F基因体外翻译选择性所需的第三个符合读框的ATG三联体。少

In persistent infection, virus can hidden in body and escape from immunological pressure, in spite of the presence of immunity. However, the virus is sometimes reactivated to produce diseases in host. Following results were obtained.1.We established an in vitro model for a persistent infection of feline immunodeficiency virus (FIV) using a human T-lymphoid cell line (MOLT-4). FIV-specific RNA expression could not be detected in the infected MOLT-4 cells, suggesting that the viral replication was blocked in the early stage of virus life-cycle. Furthemore, it was demonstrated that infectious virus was rescued by treatment of the infected MOLT-4 cells with a phorbol ester (TPA).2.Three specific pathogen-free cats experimentally infected with FIV subtypes A (Petaluma strain) and B (TM1 and TM2 strains) respectively were observed for over 8 years. The cat infected with FIV subtype A died with hemoperitoneum at 8 years and 8 months post-infection (p.i.), while those with FIV subtype B are st … More ill clinically healthy over 9 years p.i.. In persistent infection of FIV,the difference of pathogenicity among subtypes and the environment where animals kept were suggested to be important factors to develop AIDS.3.Marek's disease virus (MDV) can be serologically and genetically devided into 3 serotypes and all cause persistent infection in chickens. MDV-1 is oncogenic whereas MDV-2 is non-oncogenic. To understand the mechanisms of persistent infection and oncogenicity at genetic levels, we sequenced over 90% of MDV-2 genome.4.The immediate-early (IE) gene products of herpesviruses are thought to play an important role in regulating latent infection. We demonstrated that feline herpesvirus type 1 (FHV-1) produced a single immediate-early (IE) transcript encoding FHV-1 ICP4 and that FHV-1 ICP4 gene was alternatively regulated by the two promoters. Furthermore, it was shown that a negative regulatory element, which was composed of a 20 bp direct repeat unit, was located between the two promoters.5.A persistently infected B95a cell line with the Yanaka strain of CDV was established. The virus recovered from this carrier culture has infectivity to fresh B95a cells, and causes persistent infection without showing CPE.This virus was designated as the Yanaka-BP strain. Immunoprecipitation revealed identical molecular mass of the H or F proteins of the Yanaka and Yanaka-BP strains. Sequence analysis of the F gene showed that the third in-frame ATG triplet which considered to be selectively required for in vitro translation of the Onderstepoort F gene was lacked in the Yanaka-BP strain. Less