NEW YORK--Scientists at the Aaron Diamond AIDS Research Center
appear to have solved one of the long-standing enigmas of HIV
infection--why some people remain uninfected even after repeated
exposures to the virus. The answer lies in the genes, and in basic
research published only a few months earlier.
Studies of two homosexual men who have avoided infection since
the start of the AIDS epidemic, despite having HIV-positive partners,
uncovered a genetic mutation that appears to protect against infection
with the virus. Both men were found to have two mutant copies
of the CCR5 gene (also known as CKR-5, or chemokine receptor-5),
whose discovery was reported by five different groups in June
in a flurry of papers in Nature, Science, and Cell.
The CCR5 gene produces a protein receptor that allows HIV entry
into human immune cells. The two men with the mutant gene did
not have the receptor, Dr. Nathan R. Landau and his colleagues
reported in the journal Cell (August 9, 1996).
Other work suggests that as many as 1% of whites of Western European
descent may have the gene mutation, and up to 20% of whites may
have one copy of the defective gene. Even one copy may have a
protective role, either in lowering the risk of infection or in
delaying progression of HIV after infection.