HIV vaccine trial set to begin in South Africa

Friday, February 9, 2007

The first large-scale trial of a vaccine for HIV has been launched in South Africa. About 3,000 HIV-negative people will be administered the test vaccine MRKAd5 HIV-1 created by the pharmaceutical company Merck. The study will examine if the vaccine prevents infection or lowers HIV levels in those who do get infected.

A parallel study will also be conducted in the United States and South America, to compare the vaccine's effectiveness on various strains of HIV. The vaccine's functioning in a heterosexual population and its effectiveness among women will also be studied. Preliminary trials for the vaccine have been conducted in the Americas and Australia as well as in Africa.

Adult HIV prevalence around the world (based on UNAIDS Data).

AIDS is estimated to have killed 25 million people worldwide since 1981, and between 33 and 46 million more are estimated to be infected with HIV, more than half of them in Sub-Saharan Africa. Between three and six million people are thought to have been infected in 2005.

The trial, named the Phambili ("Going forward") Trial, is being conducted by the International HIV Trials Network and the South African AIDS Vaccine Initiative (SAAVI).

The vaccine has been developed from an adenovirus, a type of virus that causes the common cold. The virus has been genetically engineered to prevent it from causing the flu or from passing on from person to person. Instead, three genes of the HIV virus have been introduced into the adenovirus. When the vaccine containing these genes is injected into the body, it is hoped that the body's immune system will learn to recognise and kill cells that contain the vaccine, thereby also developing an immune response against the HIV virus, which also contains these three genes.

Schematic diagram of a HIV viron. The genetic material of the virus, the RNA is surrounded by a protein shell called the capsid.

The three genes, called gag, pol and env contain information needed to make the structural proteins for the capsid, the "shell" of the HIV viron. The vaccine does not contain the remaining six HIV genes that cause HIV to infect cells, replicate and cause disease.

The vaccine does not contain any live HIV and therefore cannot cause any infection, SAAVI said in a press release, adding that the vaccine was found to be safe and produced an immune response against HIV in earlier trials.

SAAVI has expressed its commitment to the "highest level of preventive care" for those who take part in the trial, promising "extensive, state-of-the-art" counselling as well as some forms of medical care and for those taking part, through the duration of the trial.

The trial starts a week after a different trial, involving a microbicide gel called Ushercell was stopped after more women who used the gel were found to be infected compared to those who were given a dummy gel as placebo. Eleven previous trials of the gel had not shown any problems, the chief scientist for the trial in South Africa told Business Day.

The trial is expected to cost $35 million and SAAVI will be supported by Eskom and the South African government.


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