- LONDON (Reuters) - The AIDS
virus HIV demonstrated its resilience when a man whose immune system was
controlling one strain of the deadly virus was infected with another, underscoring
the enormous challenge facing vaccine developers.
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- The unidentified patient had received drug therapy after
the initial infection, and his immune system had been boosted enough to
allow him to interrupt treatment and still fight the virus.
-
- But it wasn't strong enough to prevent infection with
a second strain of HIV.
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- "We have always anticipated that the development
of a vaccine is going to be difficult because there are so many closely
related strains of virus out there," Bruce Walker, the director of
the AIDS Division at Harvard Medical School in Massachusetts, said in an
interview Wednesday.
-
- "What we are seeing here is further evidence of
just how difficult that may be," he added.
-
- But the AIDS expert, who reported the case in the science
journal Nature, said he is still optimistic about vaccine approaches against
the virus.
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- "We are making progress, it's just that we are up
against a tough foe," he explained.
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- An effective vaccine is seen as the best hope to end
the AIDS epidemic that has infected 42 million people worldwide. Scientists
are looking into several vaccine approaches including boosting an antibody
response and mobilizing the so-called infantry of the immune system --
T killer cells -- to attack and destroy virus-infected cells.
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- The patient had been on supervised treatment interruption,
in which patients take breaks from drugs that help the immune system launch
a response to the virus in the same way scientists hope a vaccine will.
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- He was battling the virus on his own for several months
when doctors noticed a rise in his viral level and a decline in his T cell
response.
-
- Walker and his team ran detailed tests, which picked
up the second strain of the virus his immune system couldn't handle. The
man admitted he had earlier had unprotected sex.
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- "Consenting partners who are both HIV infected should
practice safe sex," said Walker.
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- "With the growing number of drug resistant viruses
circulating in the population the last thing you would want to do is to
be taking drugs or completely controlling your own virus and then be exposed
to a virus that has already learned to escape from the effect of the drugs."
-
- In a commentary on the research Andrew McMichael and
Sarah Rowland-Jones of the John Radcliffe Hospital in Oxford, England,
said the superinfection with a second viral strain raises questions about
both supervised treatment interruption and vaccine development.
-
- "Certainly, this single-patient analysis raises
many questions, but whether the news is bad, neutral or even good remains
to be seen."
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- But they added that nothing should slow or divert efforts
to develop an HIV vaccine.
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