HIV病毒和其引起的疾病AIDS的生物学特点。影响这一疾病的传播和预后的社会、经济和政治因素。科学研究和治疗手段的发展情况。关于艾滋病的恐惧和希望的来源。(想预览课程论坛上已有的材料，请前往@AIDSFAH或#AIDSFAH)
06.05 - Vaccine
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來自 University of Michigan 的課程
AIDS：恐惧与希望
216 個評分
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Richard Meisler, Ph.D.Lecturer
Department of American Culture, University of Michigan
In 1984, Margaret Heckler, the US Secretary of Health and
Human Services announced that HIV, the cause of AIDS, had been identified.
She added that we could expect a vaccine protecting
against HIV infection to be developed within two years.
30 years later we are still waiting for a vaccine.
A good vaccine against AIDS would be a crucial development
in the attempt to end the epidemic.
In the best of circumstances, it would protect an individual from
infection without him or her having to change any behaviors.
Although Secretary Heckler's prediction turned out to be wrong,
it was not unreasonable.
In this session, we'll give a little history of vaccines, we'll talk about
why it has been so difficult to develop a vaccine against HIV,
and we'll link to a video of Dr.
Fauci talking about resent developments in the search for a vaccine.
For centuries, in many parts of the world, in many cultures, people have used
materials from sick people to try to cure or present, prevent diseases in others.
Before the detailed bio,
biology was understood, some of these experiments met with some success.
Then in 1796, Edward Jenner found that material from
cow pox could create immunity to small pox in humans.
In 1884, Louis Pasteur created a vaccine against rabies.
In the 20th century, as the detailed scientific understanding of the human
immune system developed, an array of successful vaccines was developed.
Vaccines stimulate the human immune system to fight off an infection.
In the cases of diseases caused by a virus, the vaccine will contain
a dead virus or a virus that has been changed so that it will not cause disease.
The dead or attenuated virus will cause the immune system to pro,
produce antibodies to attack the related, invading, disease-causing virus.
Thus, when the real disease virus enters the body,
the antibodies produced in response to the vaccine will be waiting to fight it off.
In the case of most successful vaccines,
the antibodies will clear the body of the invading viruses.
We must remember of course,
that the development of a successful vaccine requires extensive
clinical trials to determine both it's safety and effectiveness.
Why haven't we been able to create a vaccine
that produces antibodies that will fight off HIV?
It turned out to be a much more difficult problem than we expected it to be.
We are already familiar with some of the reasons.
One reason is the high rate of mutation of HIV, so
some of it's properties change as the genes mutate.
We're familiar with this as the reason that HIV develops resistance to drugs.
A second factor is also familiar.
Some HIV lies dormant in the reservoir sites.
It is inactive so the antibodies will have trouble finding it.
A final reason is that HIV has a coating that makes it
difficult to find sites on the surface for the antibodies to attack.
This coating, and the way that HIV configures itself in space,
is another reason that reduces the vulnerability of HIV to antibodies.
But these decades of research and
disappointing clinical trials have not been completely unproductive.
Let's conclude this session by watching a short video in which Dr.
Fauci tells us about hopeful trends in vaccine research.
A lot of good science and observing the responses of individuals who are infected,
as well as the responses of individuals who have been in
vaccine trials that have not been overwhelmingly successful but
that have given us clues, tell us some very important things.
That even though the overwhelming majority of infected individuals
do not make an adequate immune response, the fact is if you carefully probe.
And we do this with new molecular techniques, cloning techniques
that give us a real insight into the individual B cells that make antibody.
We find that, in fact,
individuals are capable of making what we call broadly neutralizing antibodies.
They don't make them right away, only about 20% of the people make them, and
they usually take up to two years or longer to make them.
By the time you make them, even though they're broadly protective,
it's too late for the individual who made them.
So what we need to figure out is how do you harness the immune system to stimulate
the B cell repertoire that will make the broadly neutralizing antibodies.
And do it in a timely manner,
within the framework of you'd expect a regimen for a vaccine to be.
So that it doesn't take two or three or four years to do it, and instead of
doing it in 20% of the individuals, you do it in 95% of the individuals.
We're starting to get some clues by probing individual immune systems.
That we feel now that we can get a hand on how to turn
that part of the virus which we call an epitope into an immunogen, which will
induce a response that will ultimately result in broadly neutralizing antibodies.
That's what we feel the important role and the road to an HIV vaccine would be.
