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Monkey HIV vaccine 'effective', say researchers | Monkey HIV vaccine 'effective', say researchers |
(about 14 hours later) | |
By Neil Bowdler Science reporter, BBC News | By Neil Bowdler Science reporter, BBC News |
A new vaccine can protect macaques against the monkey equivalent of HIV and could provide a fresh approach to an HIV vaccine, a study suggests. | A new vaccine can protect macaques against the monkey equivalent of HIV and could provide a fresh approach to an HIV vaccine, a study suggests. |
US researchers say the vaccine offered protection to 13 of 24 rhesus macaques treated in the experiment. | US researchers say the vaccine offered protection to 13 of 24 rhesus macaques treated in the experiment. |
In 12 of the monkeys, the vaccine was still effective 12 months later. | In 12 of the monkeys, the vaccine was still effective 12 months later. |
They claim the work, published in the journal Nature, could "significantly contribute" to the development of an effective HIV/Aids vaccine. | They claim the work, published in the journal Nature, could "significantly contribute" to the development of an effective HIV/Aids vaccine. |
The researchers gave 24 healthy rhesus macaques a vaccine containing a genetically modified form of the virus, rhesus cytomegalovirus (CMV). | The researchers gave 24 healthy rhesus macaques a vaccine containing a genetically modified form of the virus, rhesus cytomegalovirus (CMV). |
In 13 of the monkeys, the vaccine appeared to offer protection against simian immunodeficiency virus (SIV), the monkey equivalent of HIV. Of these 13, 12 monkeys were still protected one year on. | |
The researchers say the vaccine works by stimulating the production of a particular type of blood cell, called "effector memory T-cells", which can remain vigilant in the body long after an infection has abated. | |
Lead author Professor Louis J Picker, of the Vaccine and Gene Therapy Institute in Oregon, compares these cells to armed soldiers at the ready. | Lead author Professor Louis J Picker, of the Vaccine and Gene Therapy Institute in Oregon, compares these cells to armed soldiers at the ready. |
"There are soldiers that are back at the base with their rifles in the shed, and then you have the guys out in the field," he told the BBC. | "There are soldiers that are back at the base with their rifles in the shed, and then you have the guys out in the field," he told the BBC. |
There was also evidence, he said, that the vaccine all but eradicated traces of SIV in the monkeys, something which he said was "unprecedented" in HIV vaccine research. | There was also evidence, he said, that the vaccine all but eradicated traces of SIV in the monkeys, something which he said was "unprecedented" in HIV vaccine research. |
Safety concerns | Safety concerns |
Researchers in the field welcomed the study, but said safety issues would need to be addressed before similar approaches could be tried in humans. | |
"I'm excited by the science because it really does demonstrate that it may be possible to eradicate the HIV virus by a strong immune response," said Professor Sir Andrew McMichael of Oxford University. | "I'm excited by the science because it really does demonstrate that it may be possible to eradicate the HIV virus by a strong immune response," said Professor Sir Andrew McMichael of Oxford University. |
"But at the same time I'm scratching my head how to take this approach into humans." | "But at the same time I'm scratching my head how to take this approach into humans." |
Professor McMichael said HIV arose from a type of SIV found in chimpanzees, so the animal model used in the study was a good one. The problem, he said, was the potential safety and regulatory issues with introducing CMV into humans, even though many of us already carry the virus. | Professor McMichael said HIV arose from a type of SIV found in chimpanzees, so the animal model used in the study was a good one. The problem, he said, was the potential safety and regulatory issues with introducing CMV into humans, even though many of us already carry the virus. |
"CMV is not totally benign, it does cause a number of diseases. If you're giving people something you're not going to be able to get rid of should it cause problems, then that's quite a difficult risk to manage." | "CMV is not totally benign, it does cause a number of diseases. If you're giving people something you're not going to be able to get rid of should it cause problems, then that's quite a difficult risk to manage." |
Professor Robin Shattock of Imperial College, London, agreed safety would be key. | Professor Robin Shattock of Imperial College, London, agreed safety would be key. |
"The breakthrough here is in using a viral-delivered vaccine that persists - essentially using an engineered virus to thwart a pathogenic virus. The tricky part will be showing it is safe and effective in humans." | "The breakthrough here is in using a viral-delivered vaccine that persists - essentially using an engineered virus to thwart a pathogenic virus. The tricky part will be showing it is safe and effective in humans." |
Professor Picker responded by saying such issues would be addressed in forthcoming work, pointing out that early forms of the smallpox vaccine also carried health risks to humans. | Professor Picker responded by saying such issues would be addressed in forthcoming work, pointing out that early forms of the smallpox vaccine also carried health risks to humans. |
"On one level 99% of people in sub-Saharan Africa are CMV-positive and half the people in the developed world are, so we know at lot about it and it's mostly non-pathogenic, except in vulnerable populations like pregnant women," he said. | "On one level 99% of people in sub-Saharan Africa are CMV-positive and half the people in the developed world are, so we know at lot about it and it's mostly non-pathogenic, except in vulnerable populations like pregnant women," he said. |
"We're fully aware to make it available to humans, then the next step is to make a virus which retains or has an enhanced ability to make effector memory cells, but no longer has the capacity to infect vulnerable parts of the population." | "We're fully aware to make it available to humans, then the next step is to make a virus which retains or has an enhanced ability to make effector memory cells, but no longer has the capacity to infect vulnerable parts of the population." |
Vaccine failure | Vaccine failure |
Developing an HIV vaccine has so far proved a deeply challenging task, but there have been some promising results. | Developing an HIV vaccine has so far proved a deeply challenging task, but there have been some promising results. |
In 2009, researchers in Thailand published in the Lancet the results of an experimental HIV vaccine, which they said reduced by nearly a third the risk of contracting HIV. | In 2009, researchers in Thailand published in the Lancet the results of an experimental HIV vaccine, which they said reduced by nearly a third the risk of contracting HIV. |
Then last year, a study in the New England Journal of Medicine suggested a drug used to treat HIV-positive patients may offer gay and bisexual men some protection against contracting the virus. | Then last year, a study in the New England Journal of Medicine suggested a drug used to treat HIV-positive patients may offer gay and bisexual men some protection against contracting the virus. |
Trials of the combination drug Truvada among nearly 2,500 men suggested it could reduce the chances of male-to-male HIV infection by 44%. | Trials of the combination drug Truvada among nearly 2,500 men suggested it could reduce the chances of male-to-male HIV infection by 44%. |
But major breakthroughs remain hard to come by. Indeed, the new Nature study comes as a separate paper in The Lancet Infectious Diseases reports on the failure of an HIV vaccine trial in South Africa. | But major breakthroughs remain hard to come by. Indeed, the new Nature study comes as a separate paper in The Lancet Infectious Diseases reports on the failure of an HIV vaccine trial in South Africa. |
The MRKAd5 HIV-1 vaccine was trialled in a study involving 801 patients, and no evidence was found that the vaccine was effective. | The MRKAd5 HIV-1 vaccine was trialled in a study involving 801 patients, and no evidence was found that the vaccine was effective. |
However, the report authors concede that the study's conclusions may have been compromised by a premature end to the trial. | However, the report authors concede that the study's conclusions may have been compromised by a premature end to the trial. |