Aids Vaccine Trials Flop

Clinical trials of the two Aids vaccines developed by the Kenya Aids Vaccine Initiative (Kavi) have failed to elicit the expected immune response.

Clinical trials of the two Aids vaccines developed by the Kenya Aids Vaccine Initiative (Kavi) have failed to elicit the expected immune response.Researchers from the International Aids Vaccine Initiative (Lavi) said interim data from the trials of the vaccines – DNA and MVA – show that the candidates’ ability to elicit anti-HIV cell-mediated immune response was poor.Dr Chrispin Kambili, Lavi’s regional medical director, Kenya office, says that preliminary data – from 205 volunteers in clinical trials conducted in Kenya, Uganda and the United Kingdom – show that the candidates elicited responses in only a quarter of volunteers who received them, and the responses were not long-lasting.According to set standards, the trials would have been considered successful had they elicited positive response in at least 60 per cent of the volunteers.Since 1998, Kavi has partnered with Iavi and researchers from Oxford University in the UK to develop the vaccine candidates, designed to prevent HIV infection and Aids by eliciting a cell-mediated immune response.Before the human clinical trials, tests in animals demonstrated that the candidates could boost the immune system.The candidates were designed based on HIV sub-type A, which affects 65 per cent of people living with Aids in Kenya.”Initial trials had shown that the vaccine is safe as there were no significant side effects,” Dr Kambili says.The DNA candidate consists of genetic material – the same material that is inserted in the MVA, which is the Smallpox virus, explains Dr Kambili.The two candidates are taken in combination.The combination is a preventive candidate intended to protect people from getting infected and contracting HIV/Aids.The candidates were initially developed after research conducted among prostitutes in Majengo, Nairobi, by researchers from the University of Nairobi revealed that some were resistant to HIV infection. It suggested that this was partly due to cell-mediated immunity.The current clinical trials (stage II) involved 400 volunteer from Kenya, Uganda and the United Kingdom, with 100 of them being Kenyans.Following the dismal results, Kambili says that over the next six to nine months, Lavi will complete a small number of clinical trials that have already started in order to learn as much as possible from the candidates.The remaining part of the trial involves slightly higher dosages. He, however, says that unless the results are drastically different, Lavi will not develop the candidates further and will focus on its other research and development projects.Dr Bonnie Bender, Lavi’s regional project co-ordinator, says her organisation will continue working with Lavi on other vaccine projects.”The government, research and the Kenyan community has been supportive throughout this process and we will continue working with them,” said Bender.The announcement of the preliminary results was first released on Tuesday at the Aids Vaccine 2004 in Lausanne, Switzerland that brings together more than 1,200 vaccine researchers from all over the world.So far, only two forms of the same vaccine have reached the final trial stage and they failed. “Even when trials are not successful there are many lessons to be learnt from the trials,” Bender told the East African Standard yesterday.(Source: All Africa Health News, September 2004)