2.DNA疫苗的安全性.
FDA guideline:
Plasmid biodistribution, persistence and integration studies were initially recommended to examine whether subjects in DNA vaccine trials were at heightened risk from the long-term expression of the encoded antigen, either at the site of injection or an ectopic site, and/or plasmid integration. Theoretical concerns regarding DNA integration include the risk of tumorigenisis if insertion reduces the activity of a tumor suppressor or increases the activity of an oncogene. In addition, DNA integration may result in chromosomal instability through the induction of chromosomal breaks or rearrangements.
质粒的生物分布,持久性和集成研究,初步建议研究在DNA疫苗试验的受试者是否从高风险的编码抗原长期表达,无论是在注射或异位网站的网站,和/或质粒整合。关于DNA整合的理论问题,包括风险的致病机,如果插入减少的一种肿瘤抑制基因的活性,或增加了一个基因的活性。此外,DNA整合,可能会导致染色体不稳定,通过诱导的染色体断裂或重排。
Conventional intramuscular, subcutaneous, intradermal, and particle-mediated delivery of DNA plasmids rarely results in the long-term persistence of vector DNA at ectopic sites. However, tissue at or near the site of administration frequently contains thousands of copies of plasmid per microgram of host DNA for periods exceeding 60 days. Studies assessing the nature of this DNA indicates that the vast majority is not integrated.
传统的肌肉注射,皮下注射,皮内,颗粒介导的DNA质粒交付很少异位网站长期持久的载体DNA的结果。然而,组织管理网站或附近经常包含数千份宿主DNA质粒期超过60天,每微克。评估这种DNA性质的研究表明,绝大多数是没有集成。
Based on published studies analyzing the frequency with which DNA plasmids persist and integrate, FDA believes that integration studies are warranted only when plasmid persists in any tissue of any animal at levels exceeding 30,000 copies per ug of host DNA by study termination. If the persistence of DNA plasmid exceeds this threshold, sponsors should evaluate whether the DNA has integrated into the genome of the vaccinated animals. A typical integration study will assess all tissue(s) containing persisting DNA plasmid. We recommend that at least four independent DNA samples be analyzed. Each sample may include DNA pooled from several different donors. Q-PCR is generally used to detect and quantify the amount of plasmid DNA present in each genomic DNA preparation. Unintegrated plasmid DNA may be separated from high molecular weight genomic DNA by gel purification. Concatamer may be eliminated by restriction endonuclease digestion targeting a rare motif present in the DNA plasmid. Specifically designed PCR primers may be used to confirm integration and identify genomic integration sites.