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

点击翻译按钮获取中文摘要

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