VOA慢速英语2021--智利皂皮树给新疫苗带来希望

A Chilean Tree Gives Hope for New Vaccines²

Quillay trees are rare evergreens³ found mainly in the South American country of Chile. And they are increasingly important to producing new vaccines.

The native Mapuche people have long used them to make soap and medicine. In recent years, quillay trees, also known as quillaja saponaria, have been used in the processing of food and drinks. They have also been used to make a highly successful vaccine¹ against shingles⁴, a painful viral disease, and the world's first malaria⁵ vaccine.

Now, molecules⁶ extracted from the bark, or outer covering, of older quillay trees are being used for a COVID-19 vaccine. It is being developed by American drug-maker Novavax. Over the next two years, Novavax plans to produce billions of treatments of the vaccine for use in developing countries.

Making the substance adjuvant

Novavax uses two molecules to make adjuvant, a substance that improves the human immune system. One of those, called QS-21, is more difficult to find. The substance is found mainly in quillay trees that are at least 10 years old.

British drug-maker GlaxoSmithKline uses QS-21 in its highly successful vaccine against shingles called Shingrix. It is also used in several other promising⁷ experimental vaccines. The quillay-based adjuvant used in Shingrix is also part of the world's first malaria vaccine, Mosquirix.

Less than one milligram of quillay extract is required to make a vaccine treatment. But the supply of quillay is stretched by the demand from other industries. Quillay products are used as a natural additive⁸ in animal feed. They also are used to kill harmful insects and as an agent to reduce pollution in mining.

Some drug-makers are developing a manufactured version of QS-21. But it could take years to get approval. Exchanging the substance for another in any existing vaccine would require new drug tests to prove the product is safe and effective.

Jason Paragas, a vice⁹ president at drug company Agenus, said, "The shortage of QS-21 has been an issue for a while." He added, "We saw it before COVID, and we made the hard decision that we had to change."

The American company in Massachusetts stopped selling the natural version of QS-21 several years ago. It now centers on trying to grow it from quillay plant cells in a laboratory. Paragas said it is too soon to know when it will be ready.

Botanical Solution, a California-based company, says it can already produce QS-21 from quillay seeds in the laboratory. The company adds that it aims to produce the substance in large quantities for drug companies.

How many quillay trees are left?

No one knows how many healthy quillay trees are left in Chile to meet the demand. Experts and industry officials believe that they will at some point need to switch to grow the evergreens on farms or in laboratories.

Ricardo San Martin developed the pruning¹⁰ and extraction process that created the modern quillay industry. He said producers must immediately work toward making quillay products from younger, farm-grown trees.

"My estimate four years ago was that we were heading towards the sustainability limit," he said.

Quillay producers say the harvest can continue for now without destroying the supply of older trees. Novavax told Reuters that the company is working with suppliers to make sure "life-saving vaccines will be prioritized."

Andres Gonzalez runs Desert King International which operates a quillay farm in Chile. It is Novavax's only supplier and the largest quillay exporter in the country. He said it produces enough quillay extract from older trees to make up to 4.4 billion vaccine treatments in 2022.

With new supplies from privately¹¹ owned forests, he said, the operation can meet demand for the rest of this year and part of the next. He admitted, however, that "at some point, these native forests will come to an end."

Gustavo Cruz is a researcher at the University of Chile who worked with San Martin to industrialize the production of quillay. He said he generally trusts quillay producers to deal with supply and demand. He is more worried about other threats – especially a lack of water and fire.

"The trees do eventually regrow," he said, "but there comes a time when they don't anymore."

Words in This Story

extract –v. to remove something by pulling it out are using a process to get it out

immune system –n. the system that protects the body from disease and infections

prune¹² –v. to cut off some of the branches of a tree so that it will grow better

sustainability –n. able to be used without being completely used up or destroyed

prioritized –adj. to be organized so that the most important thing is done or dealt with first

eventually –adv. at some time later

1 vaccine   

n.牛痘苗，疫苗；adj.牛痘的，疫苗的

参考例句：

• The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
• She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。

2 vaccines   

疫苗，痘苗( vaccine的名词复数 )

参考例句：

• His team are at the forefront of scientific research into vaccines. 他的小组处于疫苗科研的最前沿。
• The vaccines were kept cool in refrigerators. 疫苗放在冰箱中冷藏。

3 evergreens   

n.常青树，常绿植物，万年青( evergreen的名词复数 )

参考例句：

• The leaves of evergreens are often shaped like needles. 常绿植物的叶常是针形的。 来自《简明英汉词典》
• The pine, cedar and spruce are evergreens. 松树、雪松、云杉都是常绿的树。 来自辞典例句

4 shingles   

n.带状疱疹；（布满海边的）小圆石( shingle的名词复数 )；屋顶板；木瓦（板）；墙面板

参考例句：

• Shingles are often dipped in creosote. 屋顶板常浸涂木焦油。 来自《现代英汉综合大词典》
• The roofs had shingles missing. 一些屋顶板不见了。 来自辞典例句

5 malaria   

n.疟疾

参考例句：

• He had frequent attacks of malaria.他常患疟疾。
• Malaria is a kind of serious malady.疟疾是一种严重的疾病。

6 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

7 promising   

adj.有希望的，有前途的

参考例句：

• The results of the experiments are very promising.实验的结果充满了希望。
• We're trying to bring along one or two promising young swimmers.我们正设法培养出一两名有前途的年轻游泳选手。

8 additive   

adj.附加的；n.添加剂

参考例句：

• Colour is often an additive in foods.颜料经常是各种食物中的添加物。
• Strict safety tests are carried out on food additives.对食品添加剂进行了严格的安全检测。

9 vice   

n.坏事；恶习；[pl.]台钳，老虎钳；adj.副的

参考例句：

• He guarded himself against vice.他避免染上坏习惯。
• They are sunk in the depth of vice.他们堕入了罪恶的深渊。

10 pruning   

n.修枝，剪枝，修剪v.修剪（树木等）( prune的现在分词 )；精简某事物，除去某事物多余的部分

参考例句：

• In writing an essay one must do a lot of pruning. 写文章要下一番剪裁的工夫。 来自《现代汉英综合大词典》
• A sapling needs pruning, a child discipline. 小树要砍，小孩要管。 来自《现代汉英综合大词典》

11 privately   

adv.以私人的身份，悄悄地，私下地

参考例句：

• Some ministers admit privately that unemployment could continue to rise.一些部长私下承认失业率可能继续升高。
• The man privately admits that his motive is profits.那人私下承认他的动机是为了牟利。

12 prune   

n.酶干；vt.修剪，砍掉，削减；vi.删除

参考例句：

• Will you prune away the unnecessary adjectives in the passage?把这段文字中不必要的形容词删去好吗？
• It is our job to prune the side branches of these trees.我们的工作就是修剪这些树的侧枝。