Simpson D A, Davis N L, Lin S C, Russell D, Johnston R E
Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599-7290, USA.
Virology. 1996 Aug 15;222(2):464-9. doi: 10.1006/viro.1996.0445.
S.A.AR86 and Girdwood S.A., two South African Sindbis-like arboviruses, are closely related antigenically to the Swedish isolate, Ockelbo82 [Lundström, J. O., Vene, S., Saluzzo, J. F., and Niklasson, B. (1993) Am. J. Trop. Med. Hyg. 49(5), 531-537]. Each of these viruses is associated with human disease, and Girdwood S.A. was isolated from a human case. In addition, S.A.AR86 is unique among Sindbis-like viruses in that adult mice remain sensitive to lethal infection with S.A.AR86. The complete genomic sequences of S.A.AR86 and Girdwood S.A. were determined. The S.A.AR86 RNA genome contained 11,663 nucleotides, excluding the 5' CAP structure and 3' poly(A) tail. In comparison to the consensus sequence of the prototype Egyptian Sindbis strain AR339, S.A.AR86 differed at 5.57% of the nucleotides, including a 54-nucleotide deletion, two insertions of 6 nucleotides each, and a 3-nucleotide insertion in the 3' terminal one-third of the S.A.AR86 nsP3 gene. S.A.AR86 is one of only three alphaviruses sequenced to date that does not have an opal termination codon between the nsP3 and the nsP4 genes. These genes are separated by a cysteine codon in the S.A.AR86 genome. The genome of Girdwood S.A. was 11,717 nucleotides in length, excluding the 5' CAP and 3' poly(A) tail. Girdwood S.A. contained an opal termination codon between nsP3 and nsP4 and did not have the large 54-nucleotide deletion in nsP3, although Girdwood S.A. did contain the remaining insertions and deletions characteristic of S.A.AR86. S.A.AR86 was more closely related to Girdwood S.A. than to the Egyptian isolate, and the South African isolates as a group were more closely related to the Swedish isolate. Comparison of the S.A.AR86 sequence to that of Ockelbo82, Girdwood S.A., and Sindbis virus AR339 revealed several codons where S.A.AR86 differed from the conserved amino acid encoded by the other three viruses. These changes may be related to the ability of S.A.AR86 to initiate a lethal central nervous system infection in adult mice. To fulfill a prerequisite for testing this hypothesis, a full-length cDNA clone of S.A.AR86 was constructed from which infectious genomic RNA replicas could be derived. The sequence of this clone differed from the S.A.AR86 genomic RNA sequence at four translationally silent positions, and virus derived from the clone reproduced the adult mouse neurovirulence phenotype of its biological progenitor.
南非的两种辛德毕斯样虫媒病毒S.A.AR86和吉尔伍德S.A.在抗原性上与瑞典分离株奥克尔博82密切相关[伦德斯特伦，J.O.，韦内，S.，萨卢佐，J.F.，和尼克拉斯森，B.（1993年）《美国热带医学与卫生杂志》49(5)，531 - 537]。这些病毒中的每一种都与人类疾病有关，并且吉尔伍德S.A.是从一例人类病例中分离出来的。此外，S.A.AR86在辛德毕斯样病毒中是独特的，因为成年小鼠对S.A.AR86的致死性感染仍然敏感。测定了S.A.AR86和吉尔伍德S.A.的完整基因组序列。S.A.AR86 RNA基因组包含11,663个核苷酸，不包括5'帽结构和3'聚腺苷酸尾。与原型埃及辛德毕斯毒株AR339的共有序列相比，S.A.AR86在5.57%的核苷酸处存在差异，包括一个54个核苷酸的缺失、两个各6个核苷酸的插入以及在S.A.AR86 nsP3基因3'末端三分之一处的一个3个核苷酸的插入。S.A.AR86是迄今为止测序的仅有的三种甲病毒之一，在nsP3和nsP4基因之间没有乳白终止密码子。在S.A.AR86基因组中，这些基因被一个半胱氨酸密码子隔开。吉尔伍德S.A.的基因组长度为11,717个核苷酸，不包括5'帽和3'聚腺苷酸尾。吉尔伍德S.A.在nsP3和nsP4之间含有一个乳白终止密码子，并且在nsP3中没有54个核苷酸的大缺失，尽管吉尔伍德S.A.确实含有S.A.AR86特有的其余插入和缺失。S.A.AR86与吉尔伍德S.A.的关系比与埃及分离株的关系更密切，并且作为一个群体的南非分离株与瑞典分离株的关系更密切。将S.A.AR86序列与奥克尔博82、吉尔伍德S.A.和辛德毕斯病毒AR339的序列进行比较，发现了几个密码子，其中S.A.AR86与其他三种病毒编码的保守氨基酸不同。这些变化可能与S.A.AR86在成年小鼠中引发致死性中枢神经系统感染的能力有关。为了满足检验这一假设的前提条件，构建了一个S.A.AR86的全长cDNA克隆，从中可以获得感染性基因组RNA复制体。该克隆的序列在四个翻译沉默位置与S.A.AR86基因组RNA序列不同，并且从该克隆衍生的病毒再现了其生物学亲本的成年小鼠神经毒力表型。
