双语时事系列14：失明者的福音

2009-10-13 00:00:00来源：网络

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双语时事：失明者的福音：基因疗法

Three subjects with a rare form of visual impairment found their sight still better a year after gene therapy, and their immune systems seemed happy with the treatment, too.

有三位罕见形式的视力受损患者经过一年基因治疗以后，他们的视力变得更好了，而且他们的免疫系统似乎也不受任何影响。

Gene Therapy Treatment for Blindness Proves Safe--and Effective

Gene therapy has been rhapsodized and vilified in its nearly two decades of human testing, helping some and making others sicker. But a new 12-month clinical trial has shown that, at least in one ocular disease, it appears safe and—perhaps even more impressive—effective.

The research, part of a phase I clinical trial to test the safety of the treatment, was published as a letter to the editor in The New England Journal of Medicine earlier this week and will be in the September issue of Human Gene Therapy. (The paper was co-authored by about a dozen researchers, two of whom own equity in a company that could profit from a commercialized version of this procedure.)

The researchers report that three young adults with severe vision impairment from a hereditary disease maintained improved eyesight a year after gene therapy was administered—and didn't suffer any health side effects in the meantime. Gene therapy, which often employs viruses to deliver the good genes to a body's target cells, has been known to trigger severe immune responses and was blamed for the death of an 18-year-old in 1999, who was receiving gene therapy for a hereditary metabolic disorder.

The test subjects suffer from Leber congenital amaurosis (LCA), a form of hereditary retinal degeneration that occurs in infants and young children and is relatively rare. Most people who have lost vision due to hereditary retinal degeneration have either no photoreceptors with which to perceive light or photoreceptors that don't work. "This disease has a little bit of both," explains lead study author Artur Cideciyan, an associate research professor at the Scheie Eye Institute at the University of Pennsylvania. "It's a complex disease."

The participants, ages 22 to 25, all had a mutation on the RPE65 gene, the signature of LCA. Doctors administered normal RPE65 (delivered via an rAAV2 vector) into a site on one of the retinas that had the most photoreceptors left. And, Cideciyan says, "Within weeks of the procedure there was a substantial, very significant improvement in sensitivity to see dim lights."

Those in the study weren't entirely blind before the therapy. In fact, Cideciyan notes, "some of them can read," but by that he means they can see the 'E' at the top of a standard vision chart. "That does not represent the visual inability that they have because they also have a large loss of sensitivity of light… So they may be able to read on a high-contrast chart, but they are further disabled in less light environments."

What has been more surprising to the researchers is not that the improvements have held for the year—that much had already been documented in animal studies—but that, at least in one of the patients, the therapy helped train the eye to see better. "It can completely bypass the dysfunction so it can give as much vision as there are retained receptors." One patient reported that she was newly able, about a year after the treatment, to see the digital clock in the family car. Cideciyan attributes that not to continued improvement of the photoreceptors themselves but to the retraining of the visual system to take advantage of the treated areas of the retina.

Despite having a checkered past, gene therapy seemed like a promising option for many patients with this disease. There were more volunteers than could be accommodated in this trial, Cideciyan noted.

But the treatment isn't out of the woods yet. The research team will continue the study for a full three years, as is required by the U.S. Food and Drug Administration (FDA) for a phase I clinical trial. And the participants will be monitored for 15 years for health impacts, as is required by the FDA for any gene-therapy trials. Following the end of the first trial, there will be two more—to test the treatment's efficacy—before it can be approved for commercial use on the market.

Cideciyan admits that the encouraging results are only for a rare condition, but he hopes that with continued research, it will "have huge potential for much more common diseases."

基因疗法治疗失明证明安全有效

基因疗法在过去近20年的人类试验中毁誉参半，该疗法既帮助了有些患者，同时也让有些患者的病情变得更糟糕。但是一项新的为期12个月的临床试验表明，至少对于有一种眼科疾病，基因疗法看起来是安全的，而且有效，后一点可能甚至更加引人关注。

这项研究是为了测试基因疗法的安全性的一期临床试验中的一部分，该研究的结果本周以快报的形式发表在《新英格兰医学杂志》（The New England Journal of Medicine）上，全文将在9月份的《人类基因疗法》（Human Gene Therapy）杂志上发表。（这篇文章由大约12名研究者共同撰写，其中两名作者在一家公司中拥有股本，这家公司可能会从这项研究的商业化过程中获利。）

研究者们报道说，三名年轻的成年人因为一种遗传疾病而患有严重的视力损伤，他们在接受基因疗法一年后，视力得到了提高，而且视力仍然得到了保持。同时他们没有表现出任何的健康副反应。基因疗法经常使用病毒来把好的基因输送到身体的目的细胞，人们知道这种疗法能引起严重的免疫反应，在1999一名18岁的患者为了治疗一种遗传新陈代谢疾病在接受了基因疗法之后而死亡。

接受试验的患者患有Leber先天性黑朦（LCA），这是一种遗传性视网膜病变，该病相对少见，发生在婴儿和少儿身上。大多数由于遗传性视网膜病变而失明的人要么没有感光体（人们靠感光体感知光线），要么就是虽然有感光体，但是这些感光体不起作用。该研究的第一作者Artur Cideciyan解释说：“LCA这种疾病兼有上述两种情况，这是一种复杂的疾病。”Artur Cideciyan是来自宾夕法尼亚大学Scheie眼科研究所的一名副教授。

试验参与者的年龄在22到25岁之间，他们的RPE65基因上都有突变，而这就是患有LCA的标志。医生们把正常的RPE65基因利用rAAV2 媒介移入到其中一名患者的视网膜的某个感光体最少的位置上。Cideciyan说：“在治疗后的几周内，患者对弱光的感受性有了巨大的、非常显著的提高。”

在接受基因疗法之前，研究中的患者并没有完全失明。Cideciyan说：“实际上，有些患者能读书，但是他所说的能读书的意思是患者们能看见标准视力表上最上面的“E”。“这并不代表他们的视力不好，因为他们也大量损失了对光的感受性…因此他们可能在具有高对比度的图上看到东西，但是在光线不充足的环境里，他们的视力会进一步下降。”

让研究者们感到更惊奇的不是患者在接受治疗后视力的提高保持了一年---在动物试验研究中，已经有大量的类似记录---而是至少在一名患者身上，基因疗法让该患者的视力更佳。“他的眼睛完全超越了视力障碍，所以他眼睛中已有的感光体都能感光。”一名患者报告说，在接受治疗约一年后，她最近能看清她家车上的数字钟了。Cideciyan认为这不是由于感光体本身持续不断的提高，而是由于利用经过治疗的视网膜区域，视力系统得到了新的训练。

尽管基因疗法的过去充满着成功和失败。不过对于许多LCA患者来说，基因疗法似乎是个很有希望的治疗选择。Cideciyan特别提到，在这个临床试验中，志愿者们多的让他们不能完全接纳。

但是基因疗法仍然还有很多的工作需要继续。该研究小组将要继续这个为期3年整的研究，因为美国食品和药品管理局（U.S. Food and Drug Administration，FDA）要求一期临床试验为3年。根据FDA对任何基因疗法试验的要求，试验参与者将要接受为期15年的监测，以明确该疗法的健康影响。在获准上市之前，第一期临床试验结束后，还会有两期临床试验用于测试疗法的功效。

Cideciyan承认，尽管这些令人鼓舞的研究结果仅仅只针对一种罕见的疾病，但是他希望随着研究工作的继续，基因疗法将来对“更多普通的疾病有巨大的治疗作用”。

Vocabulary:

Visual：视力的

Impairment：损伤

Gene therapy：基因疗法

Immune：免疫

Rhapsodize：热情地谈论（或写）

Vilify: 污蔑；中伤

Trial: 试验

Ocular: 眼科的

Impressive: 给人影响深刻的

Equity: （公司的）股本