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解析：{{B}}Text 1{{/B}} Could HIV,

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【单选题】
{{B}}Text 1{{/B}}

Could HIV, the virus that causesAIDS, be weakening The results of a study conducted inBelgium, at the Institute of Tropical Medicine inAntwerp, seem to suggest that in one corner of the world it might be. The report, published in the latest issue ofAIDS, a specialist journal, concludes that HIV’s ability to replicate (known technically as its virulence) may have decreased since the start of the pandemiC、KevinAden, 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 inAntwerp.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、InEurope and NorthAmerica, the predominant subtype isB; in sub-SaharanAfrica, where the epidemic is at its worst, the predominant subtype isC、Most ofDr.Arien’s samples were of subtypeB、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.DrArien 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 ImperialCollege, 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,DrAden’s result is intriguing, and surely worth following up in a larger piece of research.
Which is the best title for the textA．New Method ofAIDS Treatment.
B．A、Small Hope in HIV Research.
C．AIDS’Damage MayDecrease Soon.
D．The SpecialBottlenecks to HIV Study.

网考网参考答案：B
网考网解析：
主旨大意题。全文主要介绍了关于艾滋病毒弱化的研究，但同时也指出弱化的范围很小，而且原因尚未明确，所以四个选项中只有[B]符合，选项[A]与主题无关：选项[C]过于绝对；选项[D]曲解了文义。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>

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