SCIENTISTS have found a man whose blood may hold the key to developing the first vaccine against AIDS. Mr Steve Crohn, of New York, cannot catch the HIV virus and has the first known substance in the world that will defeat it.
Scientists already knew of individuals who remain healthy for a very long time between infection with HIV and developing full blown AIDS. The difference in the case of Mr Crohn is that he appears to be resistant to infection with HIV in the first place.
Mr Crohn (49), a freelance editor for Fodor's Travel Guides, and another New Yorker who also appears to be immune, were discovered by a Glaswegian scientist, Dr Bill Paxton, of the Aaron Diamond Aids Research Center, in New York. Dr Paxton and his colleagues have found a further " people who, although not completely immune, show some degree of resistance to HIV infection. Many, of these individuals have remained tree of HIV despite a history of unsafe sex with multiple partners who subsequently died of AIDS.
From these individuals, Dr Paxton and his colleagues have taken the white blood cells known as CD4 cells which are the particular target of HIV, cultured the cells in a laboratory and tried unsuccessfully to infect them with HIV. In the case of Mr Crohn's cells, the researchers could only get the infection to "take" by flooding the cultured cells with huge amounts of virus far more than would be present in the course of a naturally occurring form of infection.
There have been indications that some people might be resistant to HIV infection, because of the chance shuffling of the genes they inherited from their parents. Some prostitutes in Africa have remained HIV free despite frequent unsafe heterosexual encounters in countries where the rate of HIV infection is very high.
However, this evidence is only statistical. The new research has identified specific individuals and their biochemistry to work out the precise mechanism of resistance.
Dr Paxton said: "If we can determine what is protecting these people then you can envisage therapy or vaccine design."
He and his colleagues have already identified one set of biochemical compounds, known as chemokines, which appear to be acting in these people to defeat HIV. These substances were first recognised only five years ago and appear to play a role in the immune system.
Dr Paxton's team report their findings in the April issue of the scientific journal Nature Medicine.
Conventional vaccines consist of antibodies to the infecting agent produced by the immune system but, partly because HIV subverts the cells of the immune system itself and partly because it is highly variable, no one has succeeded in producing a vaccine against it. The chemokines Dr Paxton and his colleagues have found are not antibodies. They are involved in the "inflammatory" response when a wound or site of infection become inflamed.
"I do not believe that next week everybody will be injecting chemokines and curing AIDS, but definitely we're on a line," Dr Paxton said.