时间:2019-01-13 作者:英语课 分类:VOA标准英语2012年(九月)


英语课

 



Scientists Seek HIV Vaccine 1 Using Monkey Model


Traditional vaccine methods have been unsuccessful in preventing infection by HIV, the virus that causes AIDS. New techniques are being studied to boost antibodies or other parts of the immune system. But researchers are also working on a method to keep the immune system constantly on guard against HIV.


There are two traditional methods for creating a vaccine. One uses a weakened or attenuated 2 version of a live virus to generate an immune response. The other uses a dead virus. Both methods are proven safe and effective, except when it comes to HIV. Vaccine candidates using these methods simply have not been successful in people when it comes to the AIDS virus.


“HIV has been a very difficult target for a vaccine for a variety of reasons. It’s designed to evade 3 the immune response by evolution,” said Dr. Louis Picker, associate director of Oregon Health and Science University.


While attempts to make an HIV vaccine from a dead virus have failed, Picker said, using a weakened virus holds clues and possibilities when used in primates 5.


“The live attenuated approach actually was shown to work 20 years ago. But the problem with it was the live attenuated vaccines 6 that actually worked were actually still pathogenic. So they weren’t safe and they could not be moved into humans. This was demonstrated in the non-human primate 4 models – monkey model of AIDS using the virus SIV,” he said.


SIV stands for simian 7 immunodeficiency virus.


“These SIVs that were attenuated, that prevented subsequent infection with the full pathogenic virus, still could cause disease. And people found that if you attenuated them anymore, they didn’t work anymore,” he said.


Picker and his colleagues wanted to understand why the weakened virus offered protection from infection. But at the same time, they needed to prevent it from itself causing disease. They found the answer has to do with T cells, which attack viruses. The weakened, but persistent 8 virus vaccines somehow caused T cells to be ever vigilant 9. But if the virus was weakened too much, the T cells were not triggered to attack. They concluded that an “effective HIV vaccine might have to persist in the body.”


Picker said, “The unique aspect of the live attenuated vaccines that seem to work was that they were persistent. They weren’t cleared by the host immune system, but they were able to stick around. Of course in the case of HIV/SIV that’s a bad thing, because eventually those live attenuated vaccines would gain strength and cause disease. But probably the fundamental reason, at least what I hypothesized, that they would be able to elicit 10 protection was because of that persistence 11.”


So, they looked for another persistent virus that was not pathogenic, which might generate T cell immune response.


“The virus that we selected was a virus called cytomegalovirus (CMV), which is actually a virus from a different family of viruses altogether, but it’s one that most people in the world are infected with. But it’s unique in that you can re-infect these people with a virus that now has within its genes 12 HIV genes and then the body would make immune responses to those HIV genes,” he said.


The HIV genes that would be placed in the harmless virus, he said, would not cause disease.


“When they’re introduced into the vaccinee, the immune response recognizes these HIV bits as if they’re part of CMV and raises immune response to it,” he said.


That’s the plan, anyway. The difficult part is making a version of the vaccine that’s safe and effective for humans. That requires an approved vaccine candidate and years of clinical trials.


Meanwhile, in Thailand, a follow-up study is getting underway of the RV 144 vaccine candidate. Several years ago, a study showed that it did indeed provide some measure of protection against HIV, but not enough, being only 31 percent effective. A clinical study called RV 305 will use the same vaccine components 13 as RV 144, but will attempt to boost and extend the immune response through antibodies.




n.牛痘苗,疫苗;adj.牛痘的,疫苗的
  • 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。
v.(使)变细( attenuate的过去式和过去分词 );(使)变薄;(使)变小;减弱
  • an attenuated form of the virus 毒性已衰减的病毒
  • You're a seraphic suggestion of attenuated thought . 你的思想是轻灵得如同天使一般的。 来自辞典例句
vt.逃避,回避;避开,躲避
  • He tried to evade the embarrassing question.他企图回避这令人难堪的问题。
  • You are in charge of the job.How could you evade the issue?你是负责人,你怎么能对这个问题不置可否?
n.灵长类(目)动物,首席主教;adj.首要的
  • 14 percent of primate species are highly endangered.14%的灵长类物种处于高度濒危状态。
  • The woolly spider monkey is the largest primate in the Americas.绒毛蛛猴是美洲最大的灵长类动物。
primate的复数
  • Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
  • Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。
疫苗,痘苗( vaccine的名词复数 )
  • 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。
adj.似猿猴的;n.类人猿,猴
  • Ada had a wrinkled,simian face.埃达有一张布满皱纹、长得像猿猴的脸。
  • Curiosity is the taproot of an intellectual life,the most valuable of our simian traits.好奇是高智生命的根源,也是我们类人猿特征中最有价值的部分。
adj.坚持不懈的,执意的;持续的
  • Albert had a persistent headache that lasted for three days.艾伯特连续头痛了三天。
  • She felt embarrassed by his persistent attentions.他不时地向她大献殷勤,使她很难为情。
adj.警觉的,警戒的,警惕的
  • He has to learn how to remain vigilant through these long nights.他得学会如何在这漫长的黑夜里保持警觉。
  • The dog kept a vigilant guard over the house.这只狗警醒地守护着这所房屋。
v.引出,抽出,引起
  • It was designed to elicit the best thinking within the government. 机构的设置是为了在政府内部集思广益。
  • Don't try to elicit business secrets from me. I won't tell you anything. 你休想从我这里套问出我们的商业机密, 我什么都不会告诉你的。
n.坚持,持续,存留
  • The persistence of a cough in his daughter puzzled him.他女儿持续的咳嗽把他难住了。
  • He achieved success through dogged persistence.他靠着坚持不懈取得了成功。
n.基因( gene的名词复数 )
  • You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
(机器、设备等的)构成要素,零件,成分; 成分( component的名词复数 ); [物理化学]组分; [数学]分量; (混合物的)组成部分
  • the components of a machine 机器部件
  • Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。