Two years ago the revelation that Merck's experimental AIDS vaccine actually increased the risk of infection among the people who volunteered for a clinical trial proved a serious blow to the whole research field, which it is still recovering from. But now researchers at Imperial College of London believe they have figured out what went wrong.
The scientific team concludes that the adenovirus--a deactivated common cold virus used to deliver the vaccine--triggered an immune response in the volunteers. Their bodies were flooded with CD4 immune cells, which fight the cold. But the same cells are also a favorite target of HIV and play a key role in infecting patients.
"We expected that pre-existing immunity would only render the vaccine less efficacious, and instead it increased the susceptibility of people to HIV," Abel Benlahrech tells Bloomberg. A large scale trial of a new AIDS vaccine in Thailand used a bird virus to deliver the vaccine, avoiding the problems associated with the adenovirus.
- check out the story from Bloomberg