Hematopoietic stem and progenitor cell (HSPC)-based ex vivo gene therapy has demonstrated clinical success for X-linked severe combined immunodeficiency (SCID-X1) patients who lack a suitable donor for HSPC transplantation. Nevertheless, this form of treatment is associated with an increased risk of infectious disease complications and genotoxicity mainly due to the conditioning regimen. In addition, ex vivo gene therapy approaches require sophisticated facilities to manufacture gene-modified cells and to care for the patients after chemotherapy. Considering these impediments, we have developed an in vivo gene therapy approach to treat canine SCID-X1 after HSPC mobilization and systemic delivery of the therapeutic vector. Here, we investigated the use of the cocal envelope to pseudotype a lentiviral (LV) vector expressing a functional gammaC gene. The cocal envelope is resistant to serum inactivation compared with the commonly used vesicular stomatitis virus envelope glycoprotein (VSV-G) envelope and thus well suited for systemic delivery. Two SCID-X1 neonatal canines treated with this approach achieved long-term therapeutic immune reconstitution with no prior conditioning. Therapeutic levels of gene-corrected CD3⁺ T cells were demonstrated for at least 16 months, and all other correlates of T cell functionality were within normal range. Retroviral integration-site analysis demonstrated polyclonal T cell reconstitution. Comparative analysis of integration profiles of foamy viral (FV) vector and cocal LV vector after in vivo gene therapy found distinct integration-site patterns. These data demonstrate that clinically relevant and durable correction of canine SCID-X1 can be achieved with in vivo delivery of cocal LV. Since manufacturing of cocal LV is similar to VSV-G LV, this approach is easily translatable to a clinical setting, thus providing for a highly portable and accessible gene therapy platform for SCID-X1.

中文翻译：

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使用 Cocal-Pseudotyped 慢病毒载体对犬 SCID-X1 进行体内基因治疗。

基于造血干细胞和祖细胞 (HSPC) 的离体基因治疗已证明对于缺乏合适的 HSPC 移植供体的 X 连锁严重联合免疫缺陷 (SCID-X1) 患者的临床成功。然而，这种形式的治疗与传染病并发症和遗传毒性的风险增加有关，主要是由于预处理方案。此外，离体基因治疗方法需要复杂的设施来制造基因修饰细胞并在化疗后照顾患者。考虑到这些障碍，我们开发了一种体内在 HSPC 动员和治疗载体的全身递送后治疗犬 SCID-X1 的基因治疗方法。在这里，我们调查了使用 cocal 信封来假型表达功能性 gammaC 基因的慢病毒 (LV) 载体。与常用的水疱性口炎病毒包膜糖蛋白 (VSV-G) 包膜相比，可卡包膜对血清失活具有抗性，因此非常适合全身给药。用这种方法治疗的两只 SCID-X1 新生犬在没有事先调理的情况下实现了长期治疗性免疫重建。^{基因校正 CD3 +}的治疗水平T 细胞被证明至少 16 个月，并且 T 细胞功能的所有其他相关性都在正常范围内。逆转录病毒整合位点分析表明多克隆 T 细胞重建。体内基因治疗后泡沫病毒 (FV) 载体和 cocal LV 载体的整合曲线的比较分析发现了不同的整合位点模式。这些数据表明，犬 SCID-X1 的临床相关和持久的校正可以通过体内递送 cocal LV 来实现。由于 cocal LV 的制造类似于 VSV-G LV，因此这种方法很容易转化为临床环境，从而为 SCID-X1 提供高度便携和可访问的基因治疗平台。