PIP: HIV attacks by first attaching itself to a target cell, then injecting genetic material which forces the cell to make copies of the virus. US researchers have reported finding a genetic mutation which makes approximately 1% of Whites studied resistant to HIV infection. The mutation has not been found in the African population or among the Japanese, and it is possible that Black Americans with the mutation inherited it through an ancestor of European descent. Kenyan and Canadian researchers, however, have documented a group of prostitutes in Nairobi who appear to be resistant to HIV, yet without the genetic mutation found in some Whites who are resistant to infection. All of the women were free of HIV infection at the beginning of the study. Over 10 years, 239 seroconverted or began to produce HIV antibodies, while most of the rest were infected to some degree, yet 43 never became infected despite an estimated 500 exposures to the virus. Polymerase chain reaction testing confirmed that these latter women were clear of HIV infection. British doctors have reported a similar group of resistant Gambian prostitutes.