STUDY OF A MURINE RETROVIRUS FROM A PACKAGING CELL LINE USED IN GENE THERAPY

基于鼠逆转录病毒的包装细胞系统已被证明 自发和零星产生感染性鼠逆转录病毒 （RCR）。 这种病毒具有广泛的宿主范围，可以感染广泛的 包括人类在内的各种灵长类动物细胞。 因此，严格和敏感 FDA目前要求制造商进行测试， 鼠逆转录病毒基因治疗产品的潜在污染。 我们启动了研究，以评估灵长类动物中RCR的潜在风险。 用RCR制剂和血液接种恒河猴， 定期采集组织样本以监测逆转录病毒 感染 我们的研究结果表明，正常的幼年猴子可能 感染了RCR。 虽然传染性病毒只能从 接种后早期，逆转录病毒序列持续了1年以上。 我们目前正在研究宿主和病毒因素， 潜在序列及其对宿主猴子的影响 基于逆转录病毒的基因治疗是一种有效的递送系统， 治疗基因 然而，有复制能力的逆转录病毒（RCR）具有 已经显示出自发地和零星地从这种包装中产生 细胞系统 由于RCR在灵长类细胞中的感染性，包括 人类细胞，有一个增加的安全问题， 基于逆转录病毒的基因治疗产品。 因此，FDA要求 对这些产品进行严格和高度敏感的测试。 支持 这些广泛和相当昂贵的要求，我们承诺， 使用猴模型系统评价灵长类动物中RCR的潜在风险。 到目前为止，我们的研究结果表明，即使是正常的猴子， 感染了相对少量的RCR，从而证实了FDA 对测试要求的定位。 目前的工作是针对 灵长类细胞中RCR潜在感染的长期影响。 这些 研究还导致了用于RCR测试的灵敏测定的发展 和病人监护的指导方针。

Murine retrovirus-based packaging cell systems have been shown to spontaneously and sporadically generate infectious murine retroviruses (RCRs). Such viruses possess a broad host range and can infect a wide variety of primate cells including human. Thus, rigorous and sensitive testing is currently required by the FDA for manufacturers to evaluate potential contamination of gene therapy products for murine retroviruses. We initiated studies to evaluate the potential risk of RCRs in primates. Rhesus monkeys were inoculated with an RCR preparation and blood and tissue samples were taken regularly to monitor for retroviral infection. Our results indicated that normal, juvenile monkeys could be infected with RCR. Although infectious virus could only be isolated early post-inoculation, retroviral sequences have persisted over 1 year . We are currently investigating host and viral factors which may activate the latent sequences and its consequences on the host monkey. Retroviral-based gene therapy is an effective delivery system for a therapeutic gene. However, replication-competent retroviruses (RCRs) have been shown to arise spontaneously and sporadically from such packaging cell systems. Due to the infectivity of RCRs in primate cells, including human cells, there is an increased safety concern regarding retroviral-based gene therapy products. Thus the FDA has required rigorous and highly sensitive testing of these products. To support these extensive and fairly expensive requirements, we undertook to evaluate potential risk of RCRs in primates using a monkey model system. Our results have thus far indicated that even normal monkeys can be infected with a relatively low amount of RCR thus confirming the FDA position on the testing requirements. Current work is directed towards long-term effects of potential infection of RCR in primate cells. These studies have also led to development of sensitive assays for RCR testing and guidelines for patient monitoring.