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Experimental Analysis of Pathogenicity of Cytomegalovirus with The Attenuated Mutants.

巨细胞病毒减毒突变体致病性的实验分析。

基本信息

批准号：
02807051
负责人：
MINAMISHIMA Yoichi
金额：
$ 1.22万
依托单位：
Miyazaki Medical College
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Human cytomegalovirus (HCMV) causes congenital infections and serious diseases in immunocompromised hosts including organ transplant recipients and patients with acquired immunodeficiency syndrome (AIDS). Because of species-specificity, mechanisms of infection and pathogenesis of HCMV has been studied with animal models. We employed murine cytomegalovirus (MCMV) as a model for HCMV.Temperature-sensitive mutants of MCMV were isolated from the Smith strain (wild type; wt) for the purpose of obtaining mutant strains with reduced pathogenicity. One of them, ts21, lacks the ability to synthesize DNA at 39ﾟC and showed the reduced ability to cause lethal infection in newborn mice. Back cross of ts21 with wt resulted in production of a recombinant (rec21w) which were temperature-insensitive but still attenuated for mice. These results suggest that ts21 harbors two independent mutations: a mutation(s) responsible for temperature sensitivity (ts), and a mutation(s) responsible for attenuation ( … More att). Genotypes of these mutants were proposed as follows: ts21 (ts, att), and rec21w (ts^+, att).The effect of each mutation on in vivo virus replication and pathogenicity was investigated. A genetical difference between wt and rec21w exists in the att gene. Virus titer in the target organs of rec21w-infected mice was almost as same as that of wt-infected mice, but rec21w produced less organ damage and less intraperitoneal hemorrhage than wt. Thus att reduces the capacity of MCMV to induce clinicopathological changes without affecting the capacity to replicate in the target organs. Therefore, lethal infection of MCMV requires a factor(s) responsible for clinicopathological changes. A genetical difference between rec21w and ts21 exists in the ts gene. Replication of ts21 was almost completely restricted in the organs of infected mice and little clinicopathological change was observed in the organs of ts21-infected rniee. The in vivo and in vitro result suggest that ts is a temperature-sensitive mutation(s) which occurred in a gene(s) essential for virus replication in cells, and the reduced pathogenicity of ts21 is directly attributable to lack of virus multiplication in the target organs whose temperature is nonpermissive for virus growth. Less

人类巨细胞病毒（HCMV）在免疫功能低下的宿主中引起先天性感染和严重疾病，包括器官移植受者和获得性免疫缺陷综合征（艾滋病）患者。由于HCMV的种特异性，人们已经用动物模型研究了HCMV的感染机制和发病机制。我们采用小鼠巨细胞病毒（MCMV）作为HCMV的模型。从Smith菌株（野生型；wt）中分离出MCMV的温度敏感突变体，以获得致病性降低的突变株。其中一种，ts21，缺乏在39ºC时合成DNA的能力，在新生小鼠中引起致命感染的能力降低。将ts21与wt回交，产生了对温度不敏感的重组蛋白rec21w，但在小鼠中仍有减毒作用。这些结果表明，ts21含有两个独立的突变：一个负责温度敏感性的突变(s)和一个负责衰减的突变(s)。这些突变体的基因型分别为ts21 （ts, att）和rec21w （ts^+, att）。研究了每种突变对病毒在体内复制和致病性的影响。wt和rec21w在att基因上存在遗传差异。rec21w感染小鼠靶器官中的病毒滴度与wt感染小鼠几乎相同，但与wt相比，rec21w造成的器官损伤和腹腔出血更少。因此，rec21w降低了MCMV诱导临床病理改变的能力，而不影响MCMV在靶器官中的复制能力。因此，MCMV致死性感染需要一个（或多个）导致临床病理变化的因素。rec21w和ts21之间的遗传差异存在于ts基因中。ts21在感染小鼠脏器中的复制几乎完全受限，感染小鼠脏器的临床病理变化很小。体内和体外实验结果表明，ts21是一种温度敏感突变，发生在病毒在细胞中复制所必需的基因上，ts21致病性降低的直接原因是病毒在温度不允许病毒生长的靶器官中缺乏繁殖。少