Humans have a similar protein, but it is not as effective at stopping HIV, according to the researchers, whose work is published in the journal Nature.

Nevertheless the identification "of this HIV-blocking factor opens new avenues for intervening in the early stge of HIV invection, before the virus can gain a toehold," said National Institute of Allergy and Infectious Disease Director Anthony Fauci.

"Basic discoveries like this provide the scientific springboard to fugure improvements in therapies for HIV disease," he added.

The research was carried out at the Dana-Farber Cancer Institute by a team headed by Joseph Sodroski and supported by the National Institute of Health's

Researchers have learned over the years "quite a bit about how HIV enters cells," Sodroski said. "More recently, we've developed a picture of the late stges of the viral lifecycle as it leaves the cell. However the steps between virus entry and conversion of the viral RNA into DNA have been a black box."

A key stage in the process is the loss of the coating that protects genes from the virus.

This coating must be shed so that the HIV virus can insert its genes in the DNA of the host cell and begin his replication.

The discovery of this protein helps researchers understand how the coating is lost.

The protein, called TRIM5-alpha, in the monkey stops the HIV virus's attempt to remove the coating, thus preventing the virus from replicating.

TERRA.WIRE