Brown E G
Laboratory Centre for Disease Control, Health and Welfare Canada, Ottawa, Ontario.
J Virol. 1990 Sep;64(9):4523-33. doi: 10.1128/JVI.64.9.4523-4533.1990.
To cause disease, influenza virus must possess several genetically determined abilities that mediate stages in pathogenesis. The virulent mouse-adapted variant A/FM/1/47-MA (FM-MA), derived from the avirulent A/FM/1/47 (FM) strain, had acquired mutations in genes that control virulence. The purpose of this study was to identify those genes that had mutated to result in increased virulence and to obtain viruses that differed in virulence because of differences in individual genome segments. The genes that had mutated to increase virulence were initially identified by genetic analysis of reassortants obtained by crossing FM-MA with the avirulent strain A/HK/1/68 (HK). FM-MA genome segments 4, 5, 7, and 8 were significantly associated with virulence, as determined by using the Wilcoxon ranked sum analysis. The role of FM-MA segments 4, 7, and 8 was confirmed by reintroduction of these genes into the parental strain, which also provided virus strains that differed in virulence because of mutations in individual genome segments. Segments 4, 7, and 8 were responsible for a 10(3.6)-fold increase in virulence that was proportioned 10(2.2)-, 10(0.7)-, and 10(0.8)-fold, respectively. The role of segment 5 could not be confirmed on transfer back into the parental strain because of reversion during preparation of such reassortants. The incidence of reversion was shown to be significantly associated with culturing of FM-MA in chicken embryo cells but was not associated with growth in MDCK cells. The genetic analysis of FM-MA suggests that adaptation to increased virulence is an incremental process that involves the acquisition of mutations in multiple genes, each of which plays an individual role in pathogenesis. The structural and functional properties of segments 4, 7, and 8 that control the virulence of FM-MA can now be determined by using viruses that differ in virulence because of mutations in these individual genome segments.
为引发疾病，流感病毒必须具备几种由基因决定的能力，这些能力介导发病机制中的各个阶段。源自无毒力的A/FM/1/47（FM）毒株的具有毒力的适应小鼠的变异株A/FM/1/47-MA（FM-MA），在控制毒力的基因中发生了突变。本研究的目的是确定那些发生突变导致毒力增加的基因，并获得因单个基因组片段差异而毒力不同的病毒。通过将FM-MA与无毒力毒株A/HK/1/68（HK）杂交获得的重配株的遗传分析，最初确定了那些发生突变以增加毒力的基因。通过使用Wilcoxon秩和分析确定，FM-MA基因组片段4、5、7和8与毒力显著相关。通过将这些基因重新导入亲代毒株，证实了FM-MA片段4、7和8的作用，这也提供了因单个基因组片段中的突变而毒力不同的病毒株。片段4、7和8分别导致毒力增加10(3.6)倍，其贡献率分别为10(2.2)倍、10(0.7)倍和10(0.8)倍。由于在制备此类重配株的过程中发生了回复突变，片段5在回交到亲代毒株时其作用无法得到证实。结果表明，回复突变的发生率与在鸡胚细胞中培养FM-MA显著相关，但与在MDCK细胞中的生长无关。FM-MA的遗传分析表明，适应增加的毒力是一个渐进过程，涉及多个基因中突变的获得，每个基因在发病机制中都发挥着各自的作用。现在可以通过使用因这些单个基因组片段中的突变而毒力不同的病毒，来确定控制FM-MA毒力的片段4、7和8的结构和功能特性。
