Clinical trials of a new vaccine against HIV, which has infected more than 40 million people worldwide, start in Switzerland and the United Kingdom in June.
Dr Jean-Pierre Kraehenbuhl, vice president of EuroVacc, the foundation organising the trials, said two vaccines would be tested: DNA-C, developed by Professor Hans Wolf of the University of Regensburg, Germany, and its booster, NYVAC, developed by the French pharmaceutical company Aventis.
Dr Kraehenbuhl said that about 160 healthy volunteers—half in London and half in the Swiss city of Lausanne, where EuroVacc is based—will test the vaccine for safety in June and early next year.
Half of the group at London's St Mary's Hospital and half of the group at Lausanne University Hospital's clinical immunology department will test DNA-C, and the others will test NYVAC, he said.
In a second trial planned to take place in 2004, healthy volunteers will receive DNA-C as a primer followed by NYVAC booster. Preclinical trials have showed that NYVAC could prevent viral infection in macaque monkeys.
In 2005 the combined vaccine consisting of DNA vaccine and NYVAC booster will be tested in Switzerland, the Netherlands, the United Kingdom, Spain, Italy, Germany, and Sweden in hundreds of people seen as being at high risk of HIV infection, including gay men, drug users, and sex workers.
Volunteers' rate of infection will then be monitored and compared with the rate of infection in similar groups of people who have not been given the vaccine.
The vaccines are designed to trigger a cellular response, in which lymphocytes kill infected host cells, and an antibody response, in which antibodies prevent the infection of host cells, said Dr Kraehenbuhl, a researcher at the Institute of Biochemistry at Lausanne University.
"We are going to inject genetic information from the AIDS virus to trigger antibodies in the host's cells," Dr Kraehenbuhl said.
If the vaccine is effective EuroVacc will then vaccinate large sections of the population in Tanzania, Rwanda, South Africa, China, and Russia.
The United States is also conducting a series of vaccine trials, called the HIV vaccine trial network, that is similar to the series being conducted by EuroVacc. The United States and the European Union are due to sign a collaboration agreement in May to ensure that effective vaccines developed by projects such as EuroVacc can be used in the United States and in Europe. More than 30 research teams in eight European countries have been involved in the EuroVacc project.
Scientists believe that an effective vaccine against HIV is possible, because some children born to HIV positive mothers seem to be protected.
Another reason is that people who develop the disease slowly and people who develop it only after many years also seem to be partly protected by their immune systems.