Santagati M G, Määttä J A, Röyttä M, Salmi A A, Hinkkanen A E
Turku Immunology Centre, University of Turku, Finland.
Virology. 1998 Mar 30;243(1):66-77. doi: 10.1006/viro.1998.9031.
We have recently shown that the 3'-nontranslated region (3'-NTR) of the avirulent Semliki Forest virus A7(74) [SFVA7(74)] contains a unique sequence of 101 nucleotides and five repetitive nucleotide units whereas the 3'-NTR of the neurovirulent SFV4 has only two repeats. A chimeric virus was constructed by replacing the entire 3'-NTR of the SFV4 clone with the A7(74) 3'-NTR. The hybrid replicated efficiently in the central nervous system (CNS) of adult Balb/c mice and, similarly to SFV4, led to high mortality after intraperitoneal inoculation. In contrast, another chimeric virus, CME2, containing the E2 gene of the avirulent SFVA7(74) virus in the SFV4 clone was recently shown to be avirulent for mice. Several derivatives with single-site or a constellation of amino acid mutations were constructed. Two single-site E2 mutants, Val37lle and Asn212Ser, displayed an attenuated phenotype in mice with mortality reduced from 90 to 48 and 43%, respectively. None of the multiple site mutants were significantly attenuated. Adult female mice showed a greater resistance to SFV infection than male mice. The SFV hybrid viruses, CM3NTR and CME2, reached the CNS similarly to the parental viruses, but the single-site E2 mutants were only sporadically found in the CNS. We conclude that in mice the 3'-NTR does not play a significant role in the pathogenesis of Semliki Forest virus and that specific E2 amino acid mutations reduce the virulence, especially in female mice. The results additionally suggest that individual amino acid mutations in the E2 glycoprotein affect the efficiency of migration into the CNS.
我们最近发现，无毒力的Semliki森林病毒A7(74)[SFVA7(74)]的3'-非翻译区(3'-NTR)包含一段101个核苷酸的独特序列和五个重复核苷酸单元，而神经毒力的SFV4的3'-NTR只有两个重复序列。通过用A7(74)的3'-NTR替换SFV4克隆的整个3'-NTR构建了一种嵌合病毒。该杂种病毒在成年Balb/c小鼠的中枢神经系统(CNS)中高效复制，并且与SFV4相似，腹腔接种后导致高死亡率。相比之下，最近发现另一种嵌合病毒CME2，其在SFV4克隆中含有无毒力的SFVA7(74)病毒的E2基因，对小鼠无毒力。构建了几种具有单点或一系列氨基酸突变的衍生物。两个单点E2突变体Val37lle和Asn212Ser在小鼠中表现出减毒表型，死亡率分别从90%降至48%和43%。多个位点突变体均未显著减毒。成年雌性小鼠对SFV感染的抵抗力比雄性小鼠更强。SFV杂种病毒CM3NTR和CME2与亲本病毒相似地到达中枢神经系统，但单点E2突变体仅偶尔在中枢神经系统中发现。我们得出结论，在小鼠中，3'-NTR在Semliki森林病毒的发病机制中不发挥重要作用，特定的E2氨基酸突变会降低毒力，尤其是在雌性小鼠中。结果还表明，E2糖蛋白中的单个氨基酸突变会影响迁移到中枢神经系统的效率。
