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9/15/99- Updated 12:30 PM ET

Weakened AIDS virus show damage

By the Associated Press

Several people in Australia who caught a weakened form of HIV in the
early 1980s are beginning to show AIDS-like damage to their immune
systems, a development that has disappointing implications for the
development of a vaccine.

Between 1980 and 1984, 13 people in Australia received blood donated
by an HIV-infected man, and eight of them caught the virus. When none
got sick, researchers analyzed the virus and found that it was missing a
working copy of a gene called nef, which boosts HIV reproduction.

Over the years, three of the infected people died of other causes, and
none has gotten AIDS.

Some researchers had hoped that a vaccine modeled on this weak virus
could be an effective AIDS vaccine, protecting people for life without
making them sick.

The idea would be to create a vaccine using a weakened version of HIV
that is missing nef and probably other genes, as well. Studies in monkeys
suggest that this may protect animals from getting the simian version of
AIDS.

However, some of the Australians now appear to show weakening
immune defenses.

Of the donor and five surviving transfusion recipients, three have falling
levels of helper T cells, a hallmark of AIDS damage. In January, the donor
whose blood infected the others began taking AIDS drugs because of his
low blood count.

The Australians are known as the Sydney Blood Bank Cohort. A report
on them was published in Thursday's New England Journal of Medicine by
Jennifer C. Learmont and others from the Australian Red Cross Blood
Service.

In an accompanying editorial, Drs. Kathleen L. Collins of the University of
Michigan and Gary J. Nabel of the National Institutes of Health said the
experience provides ''another cautionary note'' about the use of a live but
weakened HIV strain as a vaccine.

''If large populations of uninfected persons were given this virus, there
would almost certainly be unacceptable risks,'' they wrote.

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