Attenuation of the Langat tick-borne flavivirus by chimerization with mosquito-borne flavivirus dengue type 4
Attenuation of the Langat tick-borne flavivirus by chimerization with mosquito-borne flavivirus dengue type 4
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DOI：
10.1073/pnas.95.4.1746
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发表时间：
1998-02-17
影响因子：
11.1
通讯作者：
Men, R
中科院分区：
文献类型：
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作者：
Pletnev, AG;Men, R
Langat病毒（LGT）毒株TP21是对人类最弱的蜱传黄病毒，尽管LGT对人类具有低水平的神经毒力，但它及其更弱的蛋传衍生物E5毒株在正常小鼠中表现出显著的神经毒力和神经侵袭性，尽管低于与蜱传黄病毒中毒性最强的蜱传脑炎病毒（TBEV）相关的神经毒力。我们试图通过一种策略来减少或消除TP21和E5的这些病毒表型，这种策略在过去已经成功地用于降低神经毒性和消除TBEV的神经侵袭性，即将蜱传黄病毒的结构蛋白基因替换为登革热4型病毒（DEN4）的相应基因。为了实现这些目标，将不同的LGT基因组合替换到DEN4基因组中，但只有含有LGT结构蛋白前膜（preM）和包膜糖蛋白(E)的嵌合体是可行的。传染性LGT(preM-E)/DEN4嵌合体在猿类细胞培养中复制受限，但在蚊子细胞培养中生长到中等高滴度，而且嵌合体在哺乳小鼠中的神经毒性至少比亲本LGT病毒低5000倍。值得注意的是，在瑞士小鼠或更允许的SCID小鼠分别接种10(5)或10(7)个斑块形成单位（PFU）后，嵌合体缺乏可检测的神经侵袭性证据。在瑞士小鼠腹腔接种10或10(3)个PFU的嵌合病毒诱导LGT中和抗体和抵抗由LGT TP21腹腔攻击引起的致命脑炎，这些观察结果对开发TBEV减毒活疫苗的意义进行了讨论。
Langat virus (LGT) strain TP21 is the most attenuated of the tick-borne flaviviruses for humans, Even though LGT has low level neurovirulence for humans, it, and its more attenuated egg-passage derivative, strain E5, exhibit significant neurovirulence and neuroinvasiveness in normal mice, albeit less than that associated with tick-borne encephalitis virus (TBEV), the most virulent of the tick-borne flaviviruses. We sought to reduce or ablate these viral phenotypes of TP21 and E5 by using a strategy that had been used successfully in the past to reduce neurovirulence and abolish neuroinvasiveness of TBEV, namely substitution of structural protein genes of the tick-borne flavivirus for the corresponding genes of dengue type 4 virus (DEN4). In pursuit of these objectives different combinations of LGT genes were substituted into the DEN4 genome but only chimeras containing LGT structural proteins premembrane (preM) and envelope glycoprotein (E) were viable. The infectious LGT(preM-E)/DEN4 chimeras were restricted in replication in simian cell cultures but grew to moderately high titer in mosquito cell culture, Also, the chimeras were at least 5,000 times less neurovirulent than their parental LGT virus in suckling mice, Significantly, the chimeras lacked detectable evidence of neuroinvasiveness after i.p. inoculation of Swiss mice or the more permissive SCID mice with 10(5) or 10(7) plaque-forming units (PFU), respectively, Nonetheless, i.p. inoculation of Swiss mice with 10 or 10(3) PFU of either chimeric virus induced LGT neutralizing antibodies and resistance to fatal encephalitis caused by i.p. challenge with LGT TP21, The implications of these observations for development of a live attenuated TBEV vaccine are discussed.