A vaccine-like molecule that protects against HIV better than antiretroviral drugs has been discovered by scientists.
The drug candidate is also so potent and universally effective, it could be used as part of an unconventional vaccine, scientists said.
In their study published in the journal Nature, a team from the Scripps Research Institute working with a dozen other research institutions found the new drug candidate can block every strain of HIV-1, HIV-2 and SIV (simian immunodeficiency virus) isolated from humans or rhesus macaques.
It also protected against far higher doses of the virus that take place in most human transmission, and continues to do so for eight months after being administered. Scientists say with further research, it could be used to subdue HIV in humans – both as a preventative drug and a treatment.
When HIV infects a cell, it targets the body's immune system. The virus fuses with the cell and inserts its own genetic material, transforming the host into an HIV manufacturing site.
The molecule they found is called eCD4-lg. It works by binding two unchanging sites on the surface of HIV that the virus uses to attach to the receptors CD4 and CCR5.
Normally when HIV attaches to these receptors, the virus can get inside. However, when eCD4-lg binds to HIV, it takes away the virus's ability to penetrate the cell, locking it out and preventing it from multiplying.
Effectively, the scientists altered the DNA of the monkeys to give their cells properties to fight the infection.
To test the molecule, scientists placed it inside a harmless carrier virus that would cause the cell to make eCD4-lg indefinitely. This was then injected into four monkeys.
They then exposed both the treated monkeys and four untreated monkeys to SIV six times at increasingly higher doses over 34 weeks. None of the treated monkeys became infected, whereas all of the untreated ones did.
Research leader Michael Farzan said: "Our molecule appears to be the most potent and broadest inhibitor of HIV entry so far described in a preclinical study. If one could inject either eCD4-Ig or our gene therapy tool into people with HIV infection, it might control HIV for extended periods in the absence of antiretroviral drugs. Further research will help illuminate the promise of these approaches."
Anthony S Fauci, director of the National Institute of Allergy and Infectious Diseases, said: "This innovative research holds promise for moving us toward two important goals: achieving long-term protection from HIV infection, and putting HIV into sustained remission in chronically infected people."
Some concerns have been raised over the safety of such a therapy. Normally, vaccines cause the immune system to respond when a threat is present, but the latest molecule would constantly produce the HIV-killing cells – the long-term effects of which are unknown.
Scientists hope to start clinical trials on patients who have HIV but cannot take antiretroviral drug therapies as early as next year, the BBC reports.