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.