The scientist who discovered the Aids virus more than 20 years ago said he has developed a potential vaccine against the disease that has killed 25 million people around the globe.
Professor Robert Gallo, in 1984, along with the French scientist, Luc Montagnier, the first to identify that HIV caused Aids, said the latest discovery had made him more optimistic that the disease could be beaten than he had felt for a decade.
Almost 40 million people are living with HIV, most in sub-Saharan Africa, and four million more are infected each year. A vaccine that would halt its spread is the holy grail for researchers, but despite 20 years of effort and the expenditure of millions of dollars, all attempts to do so have so far failed.
Professor Gallo, director of the Institute for Human Virology at the University of Maryland, said his team had created antibodies that worked against different HIV strains, essential if a vaccine is to provide effective protection but which has defied previous attempts. The candidate vaccine had been tested successfully in four monkeys, selected because of their similarity to man, and tests are now being done on a further 12 monkeys. If those are successful, the next stage would be to test the vaccine in humans, he said.
"Yes, we are at a preliminary stage, but if 10 years ago I had known I could make antibodies that would neutralise a wide range of variants of HIV, I would have been celebratory. People thought this was pretty much impossible. It's a serious clinical advance; we have been quietly doing it. I do not know what the outcome of the latest trial [on the 12 monkeys] will be but my guess is we will move to phase 1 clinical trials [in humans] in a year's time."
He added: "Before there was no pathway. Now there is some light."
Developing a vaccine against Aids is regarded as one the most difficult challenges facing medicine and some scientists believe it is impossible. The virus mutates rapidly, it integrates itself into the patient's genetic material and it infects the very cells used by the immune system to defend the body against attack.
Professor Gallo said the approach taken by his team was to modify the protective envelope that surrounds the virus, opening a site and making antibodies to it that prevented entry of the virus into the body's cells. But the first challenge the researchers face is that the antibodies do not last longer than three months, meaning a booster dose of vaccine would be needed three to four times a year. "If we can [overcome this] we will be happy bordering on excited," he said.
There are 15 major strains of HIV, but mixing and re-combining has produced a total of about 20. The strain that dominates in Africa is A and in the US and Europe it is B. But among five people infected with the B strain of the virus only one would be protected by a B vaccine, because of variants in the strains.
Professor Gallo said: "I feel personally more optimistic but I don't want to look Pollyanna-ish. HIV has always dealt surprises. I see an avenue. But I don't know if there is a bend ahead and a truck round the corner blocking the way."
Thomas Hanke, a specialist on HIV vaccines at the human immunology unit of Oxford University, said: "There have been lots of claims for vaccines that can neutralise different strains but a vaccine that would be useful hasn't been constructed yet. Professor Gallo's success is a good reason to be positive, but it is also a good reason not to be over-excited."Reuse content