首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
Could HIV, the virus that causes AIDS, be weakening? The results of a study conducted in Belgium, at the Institute of Tropical M
Could HIV, the virus that causes AIDS, be weakening? The results of a study conducted in Belgium, at the Institute of Tropical M
admin
2010-06-17
82
问题
Could HIV, the virus that causes AIDS, be weakening? The results of a study conducted in Belgium, at the Institute of Tropical Medicine in Antwerp, seem to suggest that in one corner of the world it might be. The report, published in the latest issue of AIDS, a specialist journal, concludes that HIV’s ability to replicate (known technically as its virulence) may have decreased since the start of the pandemic. Kevin Aden, the lead author of the paper, stresses that the study is based on a small set of samples and does not prove that HIV’s virulence is attenuating around the world. However, it does offer new insights into the evolution of the disease.
Dr. Arien looked at 24 blood samples collected from untreated patients attending an HIV/ AIDS clinic in Antwerp. A dozen of these samples were taken between 1986 and 1989; the other 12 were collected between 2002 and 2003. First, he analyzed the samples to find their viral load (the number of virus particles per cubic centimeter) and the subtype of virus involved. In Europe and North America, the predominant subtype is B; in sub-Saharan Africa, where the epidemic is at its worst, the predominant subtype is C. Most of Dr. Arien’s samples were of subtype B. Having done this analysis, he paired the samples off for a series of replicative "duels". Each sample from the earlier series was matched with the most similar one from the later series, and they were placed in identical cell cultures to see which would multiply the most. The result was that 75% of the viruses from 2002-03 were less virulent than apparently similar counterparts from 1986-89—a statistically significant observation.
Dr. Arien’s caution is sensible, at least until someone replicates the work elsewhere. But his conclusion is not necessarily surprising. Such viral attenuation, as it is known, is one way that vaccines are produced.
What causes attenuation in wild viruses, though, is a matter of speculation. Dr Arien believes that in this case the attenuation could be the result of what he calls "serial genetic bottlenecks" during transmission from host to host. These act to reduce the genetic diversity (and thus the replicative fitness) of the virus. Genetic diversity is known to be an important component of HIV’s virulence. But what might cause the bottlenecks is still unclear.
A second reason for caution besides the small size of the study is, as Geoffrey Garnett, a professor of microparasite epidemiology at Imperial College, London, points out, that the ability of a virus to infect cells in a test-tube is not the same as its ability to cause disease and death in a human host. Nevertheless, Dr Aden’s result is intriguing, and surely worth following up in a larger piece of research.
选项
A、weakening.
B、accentuating.
C、accelerating.
D、increasing.
答案
A
解析
语义理解题。第一段首句提出问题"艾滋病毒可能弱化吗?",然后围绕这一问题引出一个研究,根据主题词weakening, decreased等可以推导出attenuating的意思,所以选A。B只是词形相近,C和D与此相反。
转载请注明原文地址:https://kaotiyun.com/show/9q44777K
0
考研英语一
相关试题推荐
WhentheislandofSingaporebecameanindependentcountryin1965,ithadfewfriendsandevenfewernaturalresources.Howdid
WhentheislandofSingaporebecameanindependentcountryin1965,ithadfewfriendsandevenfewernaturalresources.Howdid
Priortothe20thcentury,manylanguageswithsmallnumbersofspeakerssurvivedforcenturies.Theincreasinglyinterconnected
Iamoneofthemanycitypeoplewhoarealwayssayingthatgiventhechoicewewouldprefertoliveinthecountryawayfromth
Tosaythatthechildlearnsbyimitationandthatthewaytoteachistosetagoodexampleoversimplifies.Nochildimitatese
TheNobelsaretheoriginals,ofcourse.However,notallrewardsareasnobleastheNobels.Therearenowhundredsofawardsa
Musicproducesprofoundandlastingchangesinthebrain.Schoolsshouldaddmusicclasses,notcutthem.Nearly20yearsago,a
Discernedfromtheperplexingpictureofpopulationgrowththe1980censusprovided,Americain1970s______.Thecensusdistin
Tooffshoreservicesthatwereoncenon-tradableresultsfrom______.Whichofthefollowingstatementsisthetypicalreplyco
随机试题
下列语系中,不属于中国五大语系的是【】
罗先生,高血压病,护士为其测量血压时发现测得血压值较平日偏低,分析其原因可能是
按心理测验的目的和功能分为按测验形式分为
A.非限制使用级抗菌药物B.限制使用级抗菌药物C.特殊使用级抗菌药物D.特殊限制使用级抗菌药物经长期临床应用证明安全、有效,对细菌耐药性影响较小,价格相对较低的抗菌药物()。
下列属于公安机关必须依法履行的职责的是()
简述固定桥的类型。
法院指定甲担任乙的监护人之后,甲由于需要外出打工,于是与丙协商变更监护人。由丙担任乙的监护人。此后,在丙监护期间,乙与他人发生冲突,致人左眼失明,需要赔偿10万元。基于本案事实,下列说法正确的是()。
胜利村有一块等腰梯形农田,如图所示分割成4块种植不同的蔬菜,已知△AB0的面积为50亩,AO长度是0C长度的一半,那么整个梯形农田的面积是()亩.
有如下程序:#inelilde<lostream>usingnamespacestd;classMyClass{public:MyClass(inti=0){cout<<1;}MyCla
[A]Gladtomeetyou.[B]Seeyouagain.[C]Howareyou?[D]Bye-bye![E]I’mverywell.Howaboutyou?[F]Verywell,thankyo
最新回复
(
0
)