1 Hepatology Program, Centre for Applied Medical Research, University of Navarra, Pamplona, Spain .
2 Neurophysiology Laboratory, Neuroscience Area, Centre for Applied Medical Research and University Clinic of Navarra, Pamplona, Spain .
Hum Gene Ther. 2018 Apr;29(4):480-491. doi: 10.1089/hum.2017.056. Epub 2018 Jan 2.
Porphobilinogen deaminase (PBGD) gene therapy represents a promising therapeutic option for acute intermittent porphyria (AIP) patients suffering recurrent acute attacks. A first-in-human Phase I clinical trial confirmed the safety and tolerability of adeno-associated virus (AAV)-AAT-PBGD gene therapy, but higher doses and/or more efficient vectors are needed to achieve therapeutic expression of the transgene. This study assayed the insertion into the promoter of a short enhancer element able to induce transgene expression during exposure to endogenous and exogenous stimuli related to the pathology of the disease. The inclusion in tandem of two elements of the minimal functional sequence of human δ-aminolevulinic acid synthase drug-responsive enhancing sequence (ADRES) positioned upstream of the promoter strongly induced transgene expression in the presence of estrogens, starvation, and certain drugs known to trigger attacks in porphyria patients. The inclusion of two ADRES motives in an AAV vector improved therapeutic efficacy, reducing 10-fold the effective dose in AIP mice. In conclusion, the inclusion of specific enhancer elements in the promoter of gene therapy vectors for AIP was able to overexpress the therapeutic transgene when it is most needed, at the time when porphyrinogenic factors increase the demand for hepatic heme and precipitate acute porphyria attacks.
卟啉原脱氨酶（PBGD）基因治疗为急性间歇性卟啉症（AIP）患者反复发作的急性发作提供了一种很有前途的治疗选择。一项首次人体 I 期临床试验证实了腺相关病毒（AAV）-AAT-PBGD 基因治疗的安全性和耐受性，但需要更高的剂量和/或更有效的载体来实现转基因的治疗表达。本研究检测了在与疾病病理相关的内源性和外源性刺激下，短增强子元件插入启动子的情况，该元件能够诱导转基因表达。在雌激素、饥饿和某些已知会引发卟啉症患者发作的药物存在的情况下，将人类 δ-氨基酮戊酸合酶药物反应性增强子序列（ADRES）的最小功能序列的两个元件串联排列，可强烈诱导转基因表达。在 AAV 载体中包含两个 ADRES 基序可提高治疗效果，使 AIP 小鼠的有效剂量降低 10 倍。总之，在 AIP 基因治疗载体的启动子中包含特定的增强子元件，可在最需要的时候过度表达治疗性转基因，即在增加肝血红素需求并引发急性卟啉症发作的时期。
