Latest on AIDS vaccine
A latest vaccine against HIV/AIDS has shown to be effective in monkeys and has protected macaques the most widespread primate genus, against the monkey equivalent of HIV, Simian immunodeficiency virus (SIV). This 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. In 12 of the monkeys, the vaccine was still effective 12 months later.
The study was published in the journal Nature and could, “significantly contribute” to the development of an effective HIV/AIDS vaccine. For the study the team 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 SIV. 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. “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 explained. 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.
However experts are still worried about the safety of the vaccine. “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.” He added that 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,” he said.
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.”
Professor Picker added in his reply that 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…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,” he explained.
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. 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.
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.
Early institution of Anti-AIDS drugs protect partners
In yet another study the researchers have made a breakthrough which could slow the AIDS epidemic after finding that giving antiretroviral drugs to people with HIV prevents them infecting their partners.
The study was carried out in 13 countries. Theoretically, if every person infected with HIV was given the drug treatment early and stayed on it consistently, the epidemic could be stopped in its tracks. In 94% of cases, the partners of people with HIV in the global study were protected from the virus.
“This breakthrough is a serious game changer and will drive the prevention revolution forward,” said Michel Sidibé, executive director of the Joint United Nations Programme on HIV/AIDS (UNAIDS). “It makes HIV treatment a new priority prevention option.”
The results will give a massive boost to organisations such as UNAIDS which are arguing, in a time of financial constraint, that there is an urgent need to get Aids drugs to more people who need them. The protection is offered by the same drugs that are used to keep people with HIV well. Some 5 million people around the world are now on the antiretroviral drug combinations, but at least 10 million more need them.
“People living with HIV can now, with dignity and confidence, take additional steps to protect their loved ones from HIV,” said Sidibé. The trial's early results were so conclusive that it was stopped with at least three years still to run. Funded by the US National Institute of Allergy and Infectious Diseases (NIAID), it was carried out in several countries in Africa, as well as the US, India, Thailand and Brazil. It enrolled more than 1,700 couples in which one partner had HIV but the other did not.
“Previous data about the potential value of antiretrovirals in making HIV-infected individuals less infectious to their sexual partners came largely from observational and epidemiological studies,” said Dr Anthony S Fauci, director of the NIAID. “This new finding convincingly demonstrates that treating the infected individual – and doing so sooner rather than later – can have a major impact on reducing HIV transmission.”
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