艾滋病疫苗研究（在线收听）

HIV Vaccine Research

艾滋病疫苗研究

Two years ago, Jason Brenchley took part in an HIV vaccine trial sponsored by the U.S. National Institutes of Health. An NIH researcher himself, Mr. Brenchley says he volunteered to show others that the vaccine which contained no actual viruses, only bits of the organism's genetic code was safe.

Mr. Brenchley: It is called a DNA vaccine. They gave me DNA, which can code for proteins for HIV. Never in any circumstance is there a possibility to become infected with HIV from the vaccine.

Safe, yes but effective?

Anthony Fauci: There was no protection among those who received the vaccine versus those that received a placebo.

Anthony Fauci directs infectious disease research at the National Institutes of Health, which is spearheading U.S. efforts to develop an HIV vaccine that works.

Dr. Fauci: Thus far there have been two [vaccine] candidates that have gone all the way through an efficacy trial, but unfortunately shown not to be effective in preventing HIV infection.

Dr. Fauci says the problems of combating HIV are myriad. For one thing, the virus has the ability to insert itself into the nucleus of a human cell in effect "hiding" from an immune response. In addition the virus replicates rapidly, often with mutations that make it difficult to target. But the obstacles do not end there.

Dr. Fauci: [With] Other viruses, such as smallpox and measles, and polioneuromere the majority of people mount an immune response even if they never been vaccinated that clears the natural infection. With HIV, there are virtually no incidents of a person who has completely cleared the virus from their body, which means that although some people can control the virus better than others, the body is having trouble making a protective immune response.

In other words, HIV vaccines trigger an immune response. But that response has proven inadequate, just as the body's natural immune response to HIV infection does not eradicate the virus. Dr. Fauci says the challenge is to create a vaccine that brings about an immune response far stronger than the virus would generate on its own.

Dr. Fauci: That is a formidable scientific obstacle and task.

Despite setbacks, vaccine trial volunteer Jason Brenchley says the initiatives are worthwhile.

Mr. Brenchley: You do experiments in science because you do not know what the answer is. And if the answer is not "yes it works," then you can learn something, you can learn how to improve on that product.

The inability to develop a vaccine with any measurable efficacy has some researchers looking in other directions. At Britain's National Institute for Medical Research, virology director Jonathan Stoye thinks it may be possible to combat HIV through gene therapy.

Dr. Stoye: To take cells and try to convert them to being resistant to infection by HIV. One would then put those cells back into the individual and hope that the cells would provide a barrier [to the virus].

Dr. Stoye says a gene has been discovered that helps both humans and Rhesus monkeys fight viruses. But the monkey gene has one molecule that differs from its human counterpart. That difference, according to Dr. Stoye, appears to account for Rhesus monkeys' natural resistance to HIV. Altering the molecule in human cells might block further progression of the virus in those already infected, or could potentially provide a degree of immunity for those who are HIV-negative.

Dr. Stoye acknowledges such a treatment would take years to develop and be prohibitively expensive for most people.

Dr. Stoye: If there were a vaccine that worked, I would not be suggesting this kind of approach. But we do not have a vaccine that works, and it is not clear when or if we will get such a vaccine.

Yet the quest for a vaccine continues, with several new formulations in various stages of testing. The relative low-cost of producing vaccines and the ease of administering them make them an ideal means of combating infectious disease with one important caveat, according to the NIH's Anthony Fauci.

Dr. Fauci: When a vaccine works, it is one of the greatest public health measures you can have. When it works.

Michael Bowman, VOA news, Washington.

注释：

vaccine [5vAksi:n] n. 疫苗

circumstance [5sE:kEmstEns] n. 环境

spearhead [5spiEhed] v. 充当先锋

infection [in5fekFEn] n. 感染

replicate [5replikit] v. 复制

inadequate [in5Adikwit] adj. 不充分的