Engineered protein is a potential successful vaccine alternative for HIV

20 February 2015
An HIV ribbon

An engineered protein has been developed which has successfully blocked all known strains of HIV-1 and HIV-2 in a lab environment, and SIV (simian immunodeficiency virus) in monkeys. The protein, named eCD4-Ig, has been described as “the broadest and most potent entry inhibitor described so far”, and could form the basis of a vaccine alternative for HIV – either as a long-term preventative drug, or treatment that works to subdue HIV in the body.

The research was published in the journal Nature, and was conducted by researchers from the Scripps Research Institute in the USA. The researchers created the eCD4-Ig protein, which stops HIV from entering and infecting a cell. It does this by binding itself to two sites on the virus, which blocks the ability of HIV to attach to the CD4 receptor and CCR5 co-receptors – the gateway for HIV to infect white blood cells with its RNA.

In order to test the efficacy of eCD4-IG, the protein was placed inside a harmless carrier virus, called an adeno-associated virus (AAV). The AAV infiltrated the white blood cells, making copies of the eCD4-Ig protein indefinitely, and thus giving the cell a continuous defence against HIV. The researchers injected AAV into four monkeys, whilst another four monkeys made up the control group. They then exposed the monkeys to SIV, a monkey variant of HIV, six times over a 34-week period, and at increasingly higher doses. All the monkeys who had been exposed to AAV did not become infected, whilst all those who had not been exposed became infected with SIV.

The eCD4-Ig protein works better than the best known defence against HIV – broadly neutralising antibodies, which can ‘neutralise’ a wide range of HIV strains. The engineered protein binds itself more potently to the cell, thus being more efficient in stopping HIV. The findings are still many years away from human clinical testing. However, if the research does come to the point where it may be safe for humans, the protein could help keep the levels of HIV in the body down, as well as provide a preventative drug for at-risk populations. The researchers stated: “Although there remain challenges, these observations suggest that AAV-expressed eCD4-Ig could provide effective, long-term and near universal protection from HIV-1.”

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