基因療法有望被用於改善視力大綱

Scientists have improved the vision of a small number of patients suffering from a rare and incurable eye disease by replacing a defective gene with a healthy one-a boost for a technique known as gene therapy.

通過將有缺陷的基因替換成健康的基因，科學家已經使少數患有一種罕見、難愈眼病的病人改善了視力。這對一項被稱爲基因療法的技術是個推動。

The patients have choroideremia, a degenerative disease caused by defects in a single gene that leads to blindness and affects 1 in 50,000 people. In an early-stage trial published Wednesday in the Lancet, the researchers used a deactivated virus to safely ferry billions of healthy, lab-made versions of the gene into the retina. That appeared to restore the function of light-sensitive cells, which the disease impairs.

上述病人患有脈絡膜缺失症。這是一種由單一基因缺陷造成的退化性疾病，會導致失明，每50,000人就有1例。醫學期刊《柳葉刀》(Lancet)週三刊登了初步試驗的結果。在試驗中，研究人員使用了一種失去活性的病毒來攜帶實驗室製作的健康基因，將數以十億計的這類基因安全地注入視網膜。這在表觀上恢復了疾病損害的感光細胞的功能。

'We were surprised by the magnitude of vision improvement' in the patients, said Robert MacLaren, a professor of ophthalmology at the University of Oxford in England and leader of the clinical trial.

英國牛津大學(University of Oxford)眼科學教授、上述臨牀試驗的負責人麥克拉倫(Robert MacLaren)稱，病人視力的改善程度出乎意料。

The experiment marks one of the first times that gene therapy has targeted the main light-sensing cells in the retina. It thus offers a possible route for treating far more common causes of blindness that affect the same cells, such as retinitis pigmentosa and age-related macular degeneration.

這是以視網膜主要感光細胞爲目標開展基因療法的首批試驗之一，由此可能給治療影響主要感光細胞的更常見失明症（比如色素性視網膜炎和老年黃斑退化）提供一條途徑。

Gene therapy involves the use of DNA, rather than a protein or drug, to treat an ailment. The idea is that if the DNA gets properly embedded in the target cells, it can potentially remain there indefinitely and deliver benefits for a long time.

基因療法使用DNA治療疾病，而不是使用蛋白質或藥物。這種療法的思路是，在被妥善嵌入目標細胞的情況下，DNA可能會永遠留在細胞中，從而給病人帶來長期的益處。

Gene therapy fell out of favor after a handful of early studies led to cancer and death. That's a big reason why it hasn't yet led to a single authorized treatment in the U.S.

基因療法一度失去關注，因爲一些早期研究曾經導致癌症和死亡。這就是美國還沒有批准任何一項基因療法的重要原因。

Now, the technique is making a comeback. For example, in three early-stage clinical trials done a few years ago, the technique was used against a retinal disease called Leber congenital amaurosis. And in November 2012, European regulators approved a gene therapy treatment for a rare condition that leaves patients unable to properly digest fats-the first such approval in the Western world.

現在這種技術正在重獲關注。例如，在幾年前完成的三項早期臨牀試驗中，基因療法技術被用於治療一種名叫萊伯氏先天性黑蒙症的視網膜疾病。另一個例子是在2012年11月，歐洲監管機構批准用一項基因療法治療一種導致病人不能有效消化脂肪的罕見症狀，開啓了西方世界批准基因療法的先例。

The ailment treated in the Lancet study, choroideremia, is caused by defects in a single gene on the X chromosome and mainly affects boys. Many start losing night vision by age 10 and become legally blind in their 40s.

《柳葉刀》上發表的研究治療的脈絡膜缺失症是由X染色體的單一基因缺陷引起的，主要患者爲男孩。許多患者在10歲時開始失去夜視力，在40歲-50歲時變得徹底失明。

Because of the defective gene, light-sensitive cells in the retina slowly stop working and then die. Prof. MacLaren's team decided to make healthy versions of the gene in the lab, load each onto a small virus (one that doesn't cause disease in people) and inject the mix under the retina.

受基因缺陷影響，視網膜中的感光細胞會慢慢地停止工作並死亡。麥克拉倫教授的團隊決定在實驗室製作健康的基因，並將每個基因都裝進一個微小病毒（這種病毒並不會導致人類患病）中，然後將這種混合體注入到視網膜下面。

The therapy is given in one eye so it's easy to compare the progression of the disease with the untreated eye. 'Every injection has 10 billion viral particles, each carrying one copy of the gene,' said Prof. MacLaren. 'We have to target millions of cells.'

每個患者只有一隻眼睛接受了這種療法，因此通過未經治療的那隻眼睛，研究人員很容易就能對比病症的變化。麥克拉倫教授說，研究人員每次注入100億個病毒顆粒，每個顆粒都攜帶一份基因。他說，我們需要將數以百萬計的細胞作爲目標。

The trial began with six patients. Two still had excellent visual acuity-clearness of vision-which is measured by reading lines of letters on a sight chart. Two other patients had good acuity and two had reduced acuity.

試驗是從六位病人開始的。其中兩位病人仍擁有非常高的視敏度，兩位病人擁有較高的視敏度，另外兩位病人有着較低的視敏度。視敏度也被稱爲視覺清晰度，通過讓病人閱讀視力測驗表上的字母來衡量。

Six months after the operation, the two patients with reduced acuity showed improved vision, being able to read two and four more lines on the sight chart. The others could see better in dim light. The gains were sustained over several months of follow-up.

術後六個月，兩位視敏度較低的病人出現了視覺改善的現象，能夠在視力測驗表上多看清兩到四行字母。其他病人在弱光環境下的視力也得到了增強。這種症狀改善在隨後的幾個月內得以維持。

A 65-year-old in the trial said that when he now watches a soccer game on TV the 'green of the pitch is brighter and the numbers on the shirt much clearer.' Another who went through the procedure says he can now see stars in the night sky, which he hadn't seen for a long time.

接受臨牀試驗的一位65歲患者稱，現在當他在電視上觀看足球比賽時，綠色的場地更亮眼了，球衣上的號碼也更清楚了。另一位接受手術的患者稱，他很久都無法看到夜空中的星星，現在他能看到了。

Altering a patient's DNA is risky because it can trigger dangerous side-effects. In this case, there was no sign of an immune reaction in the first six months of the follow-up, according to the Lancet study.

改變患者的DNA是有風險的，因爲這可能引來危險的副作用。《柳葉刀》上的研究顯示，之後的六個月，患者並未出現有免疫反應的跡象。

The scientists hope to treat patients before their sight falters. 'We want to preserve the vision they've got,' said Prof. MacLaren. He now plans to test the technique on a larger group of about 30 patients.

這些科學家希望在患者徹底失去視力前進行治療。麥克拉倫教授說，我們希望使患者現有的視力得到維持。他現在計劃對約30位患者構成的更大羣體測試這項技術。