Sequence comparisons of A/AA/6/60 influenza viruses: Mutations which may contribute to attenuation
Sequence comparisons of A/AA/6/60 influenza viruses: Mutations which may contribute to attenuation
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DOI：
10.1016/0168-1702(96)01292-0
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发表时间：
1996-06-01
期刊：
影响因子：
5
通讯作者：
Maassab, HF
中科院分区：
文献类型：
--
作者：
Herlocher, ML;Clavo, AC;Maassab, HF
流感病毒感染是世界性的公共卫生威胁。冷适应用于研制疫苗株(ca A/AA/6/60H_2N_2)，有望降低与流感相关的发病率和死亡率，并可作为其他活病毒疫苗的模型。本研究证实存在两株不同的wtA/AA/6/60病毒株，具有不同的表型和基因特征。这两个病毒株具有相同的亲本，但传代历史不同。第一个品系对温度敏感(Ts)，在雪貂中减弱，第二个品系(在鸡肾细胞、鸡蛋和小鼠中多次传代后)在雪貂中不具有温度敏感度和毒性。通过序列分析进一步区分了这两株病毒。我们已经确定了所有强毒病毒共有的点突变，但在减毒病毒中没有。这是通过比较A/AA/6/60三个不同减毒代的六个内部基因的核苷酸序列与同一病毒的五个不同毒力代的核苷酸序列来实现的。因此，减毒病毒的相应核苷酸。代表候选减少性病变：碱性聚合酶基因6个(PB1中5个，PB2中1个)，酸性聚合酶基因(PA)中2个，基质(M)基因中1个，非结构(NS)基因中2个，核蛋白(NP)基因中没有。PB1的5个减少性病变中有2个是静止性的，PA的1/2是静止性的，NS的1/2是静止性的。通过将A/AA/6/60病毒的核苷酸和氨基酸序列与其他流感病毒的核苷酸和氨基酸序列进行比较可以确定的进一步变化也可能有助于CA病毒的减弱。我们的研究确定了更准确地定义这种病毒毒力的核苷酸，并表明病毒在低温下的生长可能保存了一个无毒的病毒种群，而不是减弱了一个强毒的种群。
Influenza virus infection is a worldwide public health threat. Cold-adaptation was used to develop a vaccine line (ca A/AA/6/60 H2N2) which promised to I educe the morbidity and mortality associated with influenza and to serve as a model for other live virus vaccines. This study establishes that two distinct lines of wt A/AA/6/60 viruses exist with different phenotypic and genotypic characteristics. The two virus lines have the same parent but different passage histories. The first line is both temperature sensitive (ts) and attenuated in ferrets and the second line (after multiple passages in chick kidney cells, eggs and mice) is non-ts and virulent in ferrets. Both lines of viruses have been further differentiated by sequence analysis. We have identified point mutations common to all virulent viruses but absent from the attenuated viruses. This was accomplished by comparing the nucleotide sequences of the six internal genes in three different attenuated passages of A/AA/6/60 with those of five different virulent passages of the same virus. The corresponding nucleotides of the attenuated viruses, therefore. represent candidate attenuating lesions: 6 in the basic polymerase genes (5 in PB1, 1 in PB2), 2 in the acidic polymerase gene (PA), 1 in the matrix (M) gene, 2 in the non-structural (NS) gene, and none in the nucleoprotein (NP) gene. Two of the 5 attenuating lesions in PB1 are silent; 1/2 in PA is silent; and 1/2 in NS is silent. Further changes which might be identified by comparing nucleotide and amino acid sequences of the A/AA/6/60 viruses with those of other influenza viruses may also contribute to the attenuation of the ca virus. Our study identifies nucleotides which more precisely define virulence for this virus and suggests that growth of the virus at low temperature may have preserved a non-virulent virus population rather than attenuating a virulent one.