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New research uncovers failure of HIV vaccine

Posted on 18/11/2009

Professor George Dickson

A team of researchers from Royal Holloway, University of London, Imperial College London and King’s College, have discovered that a trial of an experimental HIV vaccine failed because it might have made patients’ immune cells more vulnerable to infection.

The trial, called ‘STEP’, was halted in September 2007 because preliminary results suggested people who had been given the vaccine were more likely to be infected with HIV than people who had been given a placebo.

The HIV vaccine trial relied on the adenovirus, which is similar to a virus that causes the common cold, to enable the vaccine to travel around the body. Harmless HIV genes were then inserted into the virus. It was thought that this would help the immune system to learn to recognise and fight off HIV.

But the in vitro study, published in the ′Proceedings of the National Academy of Sciences′ (PNAS) this week, suggests because the vaccine used a vector engineered from adenovirus serotype 5 (Ad5) it caused a heightened immune response in people who had previously been exposed to the cold virus. This would make those people more vulnerable to infection because HIV attacks active immune cells, particularly if those immune cells migrate to mucosal tissues like the gut.

The researchers say their findings means scientists need to use other methods for developing vaccines for malaria and tuberculosis which also rely on the adenovirus to distribute vaccines throughout the body.

Professor George Dickson, from the School of Biological Sciences at Royal Holloway, said: “More than 60 million humans have been infected by HIV across the world, but the expected natural emergence of protective immunity in the population is very rare. Our work contributes to the search for an effective and safe HIV vaccine which will be crucial if the HIV pandemic is ever to be controlled globally. This latest study helps to explain how the HIV virus has evolved cleverly to actually profit from the human immune system, and why one particular HIV vaccine test may have had the awful consequence of increasing HIV risk as opposed to the desired effect of preventing infection.”

Royal Holloway’s School of Biological Sciences is ranked joint 3rd in the UK in the 2008 Research Assessment Exercise (RAE). To find out more, please visit:


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