VOA慢速英语:The Long Search for a Malaria Vaccine

Malaria control efforts currently depend on things like chemically treated bed nets and spraying against mosquitoes. But scientists keep trying to find other ways to prevent the disease.
目前，疟疾控制主要依靠消毒蚊帐和喷洒灭蚊药物等措施。但是，科学家们一直尝试寻找其它途径来预防该疾病。

A number of vaccines remain under development. Most contain genetically engineered versions of a few proteins from the Plasmodium parasite. Plasmodium is the organism that causes malaria. Those modified proteins are designed to get the body's defenses to launch an immune response against the Plasmodium. But the parasite contains thousands of proteins.
许多疫苗仍在研发之中，其中大多数包含疟原虫部分蛋白质的转基因版本。疟原虫是导致疟疾的生物体。这些改良过的蛋白质旨在让人体免疫系统对疟原虫免疫。但是，这种寄生虫包含数千种蛋白质。

Another experimental vaccine includes a deactivated version of the entire parasite. Robert Seder is a researcher at the National Institute of Allergy and Infectious Diseases, near Washington.
另一种实验性疫苗包含整个寄生虫的停用版本。Robert Seder是华盛顿附近的美国国家过敏与传染病研究所的一名研究员。

ROBERT SEDER: "So instead of picking out one or two or three genes, you have the potential for what we call breadth -- generating an immune response that would be broad rather than narrower. And so that would be a good thing."
ROBERT SEDER：“因此，不是挑选出一两种基因，而是拥有我们所谓的广度潜能，能够产生广泛免疫反应，而不是狭隘的。因此，将是一件好事。”

Radiation is used to weaken the parasite so it cannot make people sick or get spread by a mosquito. To make the vaccine, scientists use the parasite at a time in its growth when the organism is called a sporozoite
辐射是用来削弱寄生虫的，因此，它不能让人致病或通过蚊虫传播。为了生产这种疫苗，科学家利用其生长过程中被称为孢子虫阶段的寄生虫。

This idea has been known since the nineteen sixties. But Mr. Seder says a discovery by a researcher at a vaccine company cleared the way for progress.
这个想法自从1960年代以来就才为人熟知。但Seder先生说，一名疫苗公司研究人员的发现为这一进程扫清了障碍。

ROBERT SEDER: "The major breakthrough here was that my collaborator, Stephen Hoffman at Sanaria, developed a method where he could isolate the sporozoites and purify them so that they could administer it as a vaccine to humans. And no one thought that that was possible."
ROBERT SEDER：“这里的重大突破是我的合作者，在Sanaria公司的Stephen Hoffman发明的一种新方法。使用这种新方法，他可以隔离孢子并使其净化，这样他们使其成为用于人类的疫苗。此前没人认为这是可行的。”

But no one knew either if the weakened sporozoites would activate the immune system to protect against malaria. So researchers tested it on volunteers and found that it was safe -- there were only minor side effects. But it was not very effective. Only two out of forty-four volunteers were protected when bitten by malaria-infected mosquitoes.
但也没有人知道，这种被削弱的孢子虫是否能激活免疫系统，以预防疟疾。因此，研究人员在志愿者身上进行了测试，并发现它是安全的，但是有轻微的副作用。但它并不是很有效，44名志愿者中，只有两人在被疟疾感染蚊虫叮咬时得到了保护。

To find out why, the researchers tested the vaccine on laboratory animals. They decided that the problem was the way the vaccine had been given to the volunteers. It was injected into the skin, to simulate the bite of a mosquito. Mr. Seder says it would have been more effective if it had been given directly into the blood.
为了找出原因，研究人员在实验室用动物进行了测试。他们认为问题出在给志愿者注射疫苗的方式上，疫苗是模拟蚊虫叮咬被注入皮肤。Seder先生称，如果疫苗直接进入血液将会更有效。

However, vaccines are generally given by mouth or injected into the skin or muscle. Having to inject it into the blood could make vaccination programs more difficult if the vaccine is approved for general use. Mr. Seder says it is also too soon to know how much the vaccine would cost.
然而，疫苗一般是通过口服，注射到皮肤或肌肉。如果疫苗被批准广泛使用，注入血液会使疫苗接种程序更为困难。Seder先生称，现在也无法确认该疫苗会耗资多少。

For now, more testing is needed. A report on the study appeared in the journal Science.
现在而言，需要进行更多测试。一份研究报告发表在《科学》杂志上。