Danos O
Institut Pasteur, Paris, France.
Methods Mol Biol. 1992;8:17-27. doi: 10.1385/0-89603-191-8:17.
Most of the time, retrovirus vectors retain only cis-acting sequences from the original viral genome. These sequences allow the recombinant structure to be transcribed (LTR promoter/enhancer) and the RNA to be processed (splicing and polyadenylation signals), packaged into a virion particle (packaging sequences), and replicated by the reverse transcriptase (tRNA binding site, R region, and polypurine track). The other viral functions have to be provided in trans for the assembly of recombinant viral particles to take place. This can be simply achieved by using a replication-competent helper virus, leading to the production of a mixed population. Nevertheless, helper-free stocks are desirable for most applications, since 1. The high frequency of recombination in a mixed virus stock is likely to lead to the appearance of recombinants with unknown structure and activity. These new chimeras, either spread by the helper virus or replication-competent themselves, create a potential safety problem. 2. Cell lineage analysis using retroviral marking can only be performed and interpreted in a helper-free context 3. In vivo gene transfer experiments can be jeopardized by disease (s) associated with helper-virus infection (1).
大多数情况下，逆转录病毒载体仅保留来自原始病毒基因组的顺式作用序列。这些序列使重组结构得以转录（长末端重复序列启动子/增强子），使RNA得以加工（剪接和聚腺苷酸化信号），包装进病毒粒子（包装序列），并由逆转录酶进行复制（tRNA结合位点、R区和多嘌呤序列）。重组病毒粒子的组装需要通过反式提供其他病毒功能。这可以通过使用具有复制能力的辅助病毒简单实现，从而产生混合群体。然而，对于大多数应用而言，无辅助病毒的病毒储备是理想的，因为：1. 混合病毒储备中的高重组频率很可能导致出现结构和活性未知的重组体。这些新的嵌合体，要么由辅助病毒传播，要么自身具有复制能力，会带来潜在的安全问题。2. 使用逆转录病毒标记进行细胞谱系分析只能在无辅助病毒的情况下进行和解读。3. 体内基因转移实验可能会因与辅助病毒感染相关的疾病而受到影响（1）。
