Attenuation of Chikungunya Virus Vaccine Strain 181/Clone 25 Is Determined by Two Amino Acid Substitutions in the E2 Envelope Glycoprotein
Attenuation of Chikungunya Virus Vaccine Strain 181/Clone 25 Is Determined by Two Amino Acid Substitutions in the E2 Envelope Glycoprotein
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DOI：
10.1128/jvi.06449-11
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发表时间：
2012-06-01
影响因子：
5.4
通讯作者：
Weaver, Scott C.
中科院分区：
文献类型：
--
作者：
Gorchakov, Rodion;Wang, Eryu;Weaver, Scott C.
基孔肯雅病毒（CHIKV）是蚊媒甲病毒，是最近影响非洲和亚洲数百万人的关节炎性发热疾病大规模爆发的病原体。已在人体中测试的唯一CHIKV疫苗，毒株181/克隆25，是东南亚人分离株AF 15561的减毒活衍生物。该疫苗在I期和II期临床试验中具有免疫原性;然而，它在8%的接种者中诱导了短暂的关节痛。该疫苗与其亲本之间存在五个氨基酸差异，以及五个同义突变，其中没有一个涉及已知负责复制或包装的顺式作用基因组区域。为了鉴定减毒的决定因素，我们因此通过将它们单独或以不同组合克隆到来自两种野生型（WT）CHIICV毒株La Reunion和AF 15561的感染性克隆中来测试五种非同义突变。在两种不同的小鼠模型（婴儿CD 1和成年A129小鼠）中比较了WT毒株和疫苗毒株的毒力水平。通过同时表达两个E2糖蛋白取代，获得了与181/克隆25疫苗株无区别的减毒表型，单一E2突变获得了中等水平的减毒。nsPl、6 K和El中的其他三个氨基酸突变对CHIKV毒力没有可检测的影响。这些结果表明，菌株181/克隆25的减毒是由两个点突变介导的，这解释了在人疫苗接种者和我们的研究中观察到的表型不稳定性。
Chikungunya virus (CHIKV) is the mosquito-borne alphavirus that is the etiologic agent of massive outbreaks of arthralgic febrile illness that recently affected millions of people in Africa and Asia. The only CHIKV vaccine that has been tested in humans, strain 181/clone 25, is a live-attenuated derivative of Southeast Asian human isolate strain AF15561. The vaccine was immunogenic in phase I and II clinical trials; however, it induced transient arthralgia in 8% of the vaccinees. There are five amino acid differences between the vaccine and its parent, as well as five synonymous mutations, none of which involves cis-acting genome regions known to be responsible for replication or packaging. To identify the determinants of attenuation, we therefore tested the five nonsynonymous mutations by cloning them individually or in different combinations into infectious clones derived from two wild-type (WT) CHIICV strains, La Reunion and AF15561. Levels of virulence were compared with those of the WT strains and the vaccine strain in two different murine models: infant CD1 and adult A129 mice. An attenuated phenotype indistinguishable from that of the 181/clone 25 vaccine strain was obtained by the simultaneous expression of two E2 glycoprotein substitutions, with intermediate levels of attenuation obtained with the single E2 mutations. The other three amino acid mutations, in nsPl, 6K, and El, did not have a detectable effect on CHIKV virulence. These results indicate that the attenuation of strain 181/clone 25 is mediated by two point mutations, explaining the phenotypic instability observed in human vaccinees and also in our studies.