Study explains why HIV so tough to beat

Scientists have solved one of the great mysteries of the HIV/AIDS virus: why it is so successful at breaking down the body's resistance.

A paper in the journal Nature, published today, lays out the reasons why humans do not produce antibodies against the virus.

This lack of a natural defence allows the virus to enter cells without being attacked.

The findings offer new hope for vaccines which could target HIV/AIDS more effectively.

The key is a potential weak link, a protein on the surface of HIV called gp41, which helps the virus invade cells.

Professor Stephen Kent, an immunologist at the University of Melbourne, says gp41 has been of great interest to HIV vaccinologists.

"The GP41 component is the component that essentially punches a hole in the membrane or the surface of the cell and allows the virus to get in," he said.

"It's a very critical component of the entry mechanism of the virus.

"If we can prevent the HIV from getting into cells, then we'd have a great vaccine."

It has been known for many years that about one in 1,000 people can naturally control the HIV virus, by making an antibody against gp41.

The work published in Nature shows that while most people do develop an antibody against gp41, they do this after the virus has already entered their cells.

"They're making a response against this gp41 after the horse has already bolted," Professor Kent said.

"And so the virus gets in, it infects, it destroys these CD4 cells, and only then is the antibody made.

"It's disappointing, but at the same time it's also a clue. As we understand this better we can now try and direct our efforts against the specific parts of gp41 that we can attack before the virus can get into the cell.

"It's perhaps a couple of steps back and one step forward for HIV vaccine research."