Washington: Scientists in the US claim to have unravelled how HIV hijacks the body's own defences to promote infection, a finding which may pave the way for curbing the spread of AIDS.

A team at University of California, led by Nevan Krogan, has described how HIV commandeers restriction factors -- a class of human proteins that evolved to block viruses -- to weaken the body's defences and enhance the virulence of HIV infection, the 'Nature' journal reported.

"One of the keys to HIV's success is how quickly it can evolve new attack strategies -- and the way in which it uses our own proteins against us is a prime example of that," said Dr Krogan.

He added, "However, now that we've shed light on this complex process, we are one step closer to developing new drugs that will help us pull ahead in this evolutionary arms race."

AIDS has killed more than 25 million people around the world since first being identified some 30 years ago. In the US alone, more than one million people live with HIV/AIDS at an annual cost of US dollars 34 billion.

Dr Krogan's experiments show promise for the development of more effective antiretroviral therapies for people with HIV. Further, the scientists have laid the foundation for future research.

In their experiments, the scientists performed a two-part investigation of protein interactions. First, they conducted a systematic, global analysis of all potential interactions that occur between proteins made by the body (human proteins) and proteins made by the virus (HIV proteins).

Second, they whittled down these 500 interactions to the one that appeared most likely to fuel HIV infection – the interaction between human protein CBF? and HIV protein Vif.

Normally during HIV infection, a restriction factor called APOBEC3G acts as a molecular roadblock, preventing the virus from reaching its target -- the CD4 T white blood cells that are a major component of the immune system.

But Dr Krogan found that when the HIV protein Vif binds to the human protein CBF? Vif is strengthened and APOBEC3G degrades. This degradation weakens ABOBEC3G's ability to stop HIV and the virus is free to infect the CD4 T cells.

"This is the first comprehensive look at how HIV interacts globally with components of the cell," said Judith H Greenberg of National Institutes of Health's National Institute of General Medical Sciences.