Blancou Philippe, Chenciner Nicole, Ho Tsong Fang Raphaël, Monceaux Valérie, Cumont Marie-Christine, Guétard Denise, Hurtrel Bruno, Wain-Hobson Simon
Unité de Rétrovirologie Moléculaire. Unité de Physiopathologie des Infections Lentivirales, Institut Pasteur, 75724 Paris Cedex 15, France.
J Virol. 2004 Feb;78(3):1080-92. doi: 10.1128/jvi.78.3.1080-1092.2004.
Among the many simian immunodeficiency virus (SIV) immunogens, only live attenuated viral vaccines have afforded strong protection to a natural pathogenic isolate. Since the promoter is crucial to the tempo of viral replication in general, it was reasoned that promoter exchange might confer a novel means of attenuating SIV. The core enhancer and promoter sequences of the SIV macaque 239nefstop strain (NF-kappaB/Sp1 region from -114 bp to mRNA start) have been exchanged for those of the human cytomegalovirus immediate-early promoter (CMV-IE; from -525 bp to mRNA start). During culture of the resulting virus, referred to as SIVmegalo, on CEMx174 or rhesus macaque peripheral blood mononuclear cells, deletions arose in distal regions of the CMV-IE sequences that stabilized after 1 or 2 months of culture. However, when the undeleted form of SIVmegalo was inoculated into rhesus macaques, animals showed highly controlled viremia during primary and persistent infection. Compared to parental virus infection in macaques, primary viremia was reduced by >1,000-fold to undetectable levels, with little sign of an increase of cycling cells in lymph nodes, CD4(+) depletion, or altered T-cell activation markers in peripheral blood. Moreover, in contrast to wild-type infection in most infected animals, the nef stop mutation did not revert to the wild-type codon, indicating yet again that replication was dramatically curtailed. Despite such drastic attenuation, antibody titers and enzyme-linked immunospot reactivity to SIV peptides, although slower to appear, were comparable to those seen in a parental virus infection. When animals were challenged intravenously at 4 or 6 months with the uncloned pathogenic SIVmac251 strain, viremia was curtailed by approximately 1,000-fold at peak height without any sign of hyperactivation in CD4(+)- or CD8(+)-T-cell compartment or increase in lymph node cell cycling. To date, there has been a general inverse correlation between attenuation and protection; however, these findings show that promoter exchange constitutes a novel means to highly attenuate SIV while retaining the capacity to protect against challenge virus.
在众多猿猴免疫缺陷病毒（SIV）免疫原中，只有减毒活病毒疫苗能对天然致病分离株提供强有力的保护。由于启动子通常对病毒复制的节奏至关重要，因此有人推测启动子交换可能会带来一种减毒SIV的新方法。已将SIV猕猴239nefstop株的核心增强子和启动子序列（从-114 bp到mRNA起始位点的NF-κB/Sp1区域）替换为人巨细胞病毒立即早期启动子（CMV-IE；从-525 bp到mRNA起始位点）的相应序列。在CEMx174或恒河猴外周血单个核细胞上培养产生的病毒（称为SIVmegalo）时，CMV-IE序列的远端区域出现了缺失，这些缺失在培养1或2个月后稳定下来。然而，当将未缺失形式的SIVmegalo接种到恒河猴体内时，动物在原发性和持续性感染期间显示出病毒血症得到高度控制。与猕猴感染亲本病毒相比，原发性病毒血症降低了1000倍以上，降至检测不到的水平，淋巴结中循环细胞增加、CD4(+)细胞耗竭或外周血中T细胞活化标志物改变的迹象很少。此外，与大多数感染动物中的野生型感染不同，nef终止突变没有恢复为野生型密码子，这再次表明复制受到了显著抑制。尽管出现了如此剧烈的减毒，但针对SIV肽的抗体滴度和酶联免疫斑点反应性虽然出现得较慢，但与亲本病毒感染中的情况相当。当动物在4或6个月时静脉内接种未克隆的致病性SIVmac251株时，病毒血症在峰值高度时降低了约1000倍，CD4(+)或CD8(+) T细胞区室没有任何过度活化的迹象，淋巴结细胞循环也没有增加。迄今为止，减毒与保护之间通常呈负相关；然而，这些发现表明启动子交换构成了一种高度减毒SIV同时保留抵御攻击病毒能力的新方法。
