A new test is being
developed that could help narrow the field of promising AIDS vaccine
candidates. If successful, time and money could be concentrated on vaccines
with the greatest potential to block HIV.
The test is called
a viral inhibition assay and is being developed by scientists at the
International AIDS Vaccine Initiative, IAVI, and Imperial College London. Dr.
Jill Gilmour, IAVI's senior director of clinical research, explains why the
test is needed.
"So far, I think a
number of the tests that have been used sort of take indirect measurements. And
we felt that we wanted a test that measured something much more akin to what
the human body would actually have to do and measure the total function of the
immune response. So, ultimately, we want the immune response to be able to stop
HIV from replicating. And that's exactly the test that we set up," she says.
The test would
determine whether immune cells could fend off HIV after getting a boost from a
She says, "You
know, we take CD-4 T-Cells and infect them with HIV, which is exactly what
would happen in your body, and then look to see whether the immune cells from a
vaccinated individual could stop the virus replicating. And that's exactly what
we would need a vaccine to be able to do, possibly more relevant than a lot of
the other tests out there."
based at the Human Immunology Lab in London, says the new test would examine
several aspects of a vaccine.
"This is measuring
total function. A lot of the other tests to assess current vaccines look at
whether the vaccine induces an immune response. It doesn't necessarily tell us
about the quality of the response or whether the response could stop the virus
from replicating or indeed how many viruses the response could inhibit. So,
it's taking a broader sweep at the function," she says.
The test results
will be compared to data collected during a vaccine clinical trial now underway
will not be able to say whether this test can predict whether a vaccine works
until we get a vaccine into a clinical trial that demonstrates efficacy, that actually
shows the vaccine works. But what we do believe is that it will give us a much better
handle on how to select those vaccine candidates to go forward," she says.
Dr. Gilmour says
clinical trials cost millions of dollars and often involve thousands of
volunteers. So, selecting only the most promising candidates could save a great
deal of time and money.
collaborating with the US National Institutes of Health and Merck to acquire a
good sample of vaccine candidates. If eventually proven effective, the test
could determine within three weeks whether a vaccine candidate is worthy of
often asked how long it will take to find an effective AIDS vaccine. Gilmour
says the answer remains elusive.
"I'm probably going
to give you the answer you've heard on many occasions. We don't know. This
endeavor is certainly not for the fainthearted. But I do believe that Mother
Nature tells us that it's possible. For example, there are people who are
multiply exposed and don't become infected. Or there are individuals who control
their HIV for many, many years without treatment. The vaccine effort really
only has had a concerted effort since the mid-90s. And the polio vaccine took,
for example, 40 years to develop. So, I think we're still quite early in," she
AIDS Vaccine Initiative hopes to have definitive word on its vaccine test by
early next year.