Passage 1

American researchers have developed a technique that may become an important tool in fighting AIDS. The technique stops the AIDS virus from attacking its target-cells in the body’s defense system. When AIDS virus enters the blood, it searches for blood cells called T4 lymphocytes (淋巴细胞). The virus connects to the outside of T4 lymphocytes, then forces its way inside. There it directs the cells’ genetic (基因的) material to produce copies of the AIDS virus. This is how AIDS spreads. Researchers think they may be able to stop AIDS from spreading by preventing virus from connecting to T4 cells. When AIDS virus finds a T4 cell, it actually connects to a part of the cell called CD4 protein.

Researchers want to fool the virus by putting copies or clones of the CD4 protein into the blood. This way the AIDS virus will connect to the cloned protein instead of the real ones. Scientists use the genetic engineering methods to make the clones. Normally a CD4 protein remains on the T4 cell at all times. The AIDS virus must go to it. In a new technique, however, the cloned CD4 protein is not connected to a cell. It floats freely, so many more can be put into the blood to keep the AIDS virus away from real CD4 proteins on T4 cells. One report says the AIDS virus connects to the cloned proteins just as effectively as to real protein. That report was based on tests with blood cells grown in labs. The technique is just now beginning to be tested in animals. If successful, it may be tested in humans within a year.

1. The new technique can ______.

A. cure AIDS B. kill the AIDS virus

C. prevent the AIDS virus from spreading D. produce new medicines for AIDS

2. When the AIDS virus enters the blood, it is reproduced by ______.

A. the inside of the virus itself B. any blood cells in the body

C. the CD4 protein D. the genetic material of T4 cells

3. The AIDS virus connects to cloned proteins instead of to the real ones because ______.

A. the cloned proteins stay on the T4 cells

B. the cloned protein can float freely, keeping AIDS virus away from T4 cells

C. it connects to cloned proteins more effectively than to the real ones

D. the cloned proteins are made by genetic engineering methods

4. Which of the following statements is NOT true?

A. The new technique has been tested in labs.

B. The new technique is being tested in animals.

C. The new technique may be tested in humans.

D. The new technique is now under clinical test.

5. Which of the following could be the best title of this passage?

A. AIDS — a Fatal Disease.

B. A New Technique in Fighting AIDS.

C. A Report on the Spread of AIDS Virus.

D. The Technique of Cloned CD4 Protein.

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