The researchers at Chelsea and Westminster Hospital are studying people who have had repeated exposure to the human immuno-deficiency virus (HIV) but have remained resistant to infection. They hope to report their findings within the year.
Yesterday the Independent revealed that scientists in the US have discovered that Steve Crohn, from New York, has the first known substance in the world that will defeat HIV. Scientists at the Aaron Diamond Aids Research Center, in New York, took his white blood cells known as CD4 cells, which are the particular target of HIV, cultured them in the laboratory and tried unsuccessfully to infect them with HIV.
The 40 people being studied in Britain were recruited about a year ago through advertising in HIV clinics and newspapers.
"There were three components we looked for," said Dr Philippa Easterbrook, senior lecturer in infectious diseases and epidemiology. "First that they should have been exposed fairly recently - within the last year. Secondly, they should have had a very significant level of exposure over a two-year period and third that they should have had an HIV test recently."
Dr Easterbrook said in the past there had been various explanations put forward as to why people did not become infected with HIV, including the fact that they could have been infected by someone who had low-level infection, or a weak form of the virus or that although they were infected it had not shown up in the antibodies.
She said the most recent data made it likely that immune response was an "important explanation", but she added: "We're a long way from picking up information for a specific vaccine but this data clearly has long-term application." She called for more studies to be undertaken looking at the offspring of infected mothers who did not go on to develop the virus, partners of haemophiliacs who had been given infected blood, and exposed health care workers.
Professor Frances Gotch, head of immunology at the Chelsea and Westminster, said the US findings were "extremely interesting" and showed "for the first time certain people are non-susceptible to the virus - that gives us hope for a vaccine".
Research in Gambia, the result of a collaboration between the Medical Research Council and the Institute of Molecular Medicine in Oxford, showed that some prostitutes also had not succumbed to the virus.
"From our research we believed that individual cases who were non-susceptible but had had high exposure were transiently infected," Professor Gotch said. "This gave the body time before CD4 cells were infected which gave other cells the chance to kick in an immune response. This would be the same effect as having a vaccine."
A spokesman for the Terrence Higgins Trust said: "We are cautiously optimistic. Hopefully it will be a small step on the long road to finding a vaccine."Reuse content