How the HIV virus attacks the immune system

Bern (ots) - The molecular shield of the AIDS virus
The envelope of the AIDS virus is fraught with "spikes" called spicules, which help to penetrate the host cell. But our immune system, these spicules are also points of attack against the virus. Researchers supported by the Swiss National Science Foundation (NSF) have now discovered how HIV manages to thwart the host defense.

The AIDS virus, HIV, like a ball bristling with dozens of tiny "spikes" called spicules. These are formed by the envelope proteins of the virus, and they are both his weapon and his weak point. On the one hand, the virus needs to enter host cells and reproduce. The other, they are all points of attack: the antibodies produced immune system to neutralize the AIDS virus are in fact directed against all parts of spicules.

Game of cat and mouse once in the body of the patient, the virus is constantly changing to evade antibodies. Forcing the immune system to constantly create new antibodies suitable. "This is the game of cat and mouse," says Alexandra Trkola, Institute of Medical Virology, University of Zurich. With colleagues at the University Hospital of Zurich and ETH, the team has shown it takes as part of a recently published study (*) that the spicules of the virus with molecular shields. Their function: antibodies protect against certain structures of particular importance to the virus.

These shields are composed of two neighboring domains and a flexible envelope protein, such as loops that wrap around the loose spicules. In trials conducted on genetically modified viruses, Alexandra Trkola team found that when these loops are missing, the human immune system can inhibit the virus without any problems.

A completely different approach Another thing: it was not known until the exact position of these loops - despite intensive efforts worldwide to obtain information from viral proteins crystallized. Researchers Alexandra Trkola group opted for a completely different approach. They rebuilt a spike, which is normally composed of three identical proteins, from two genetically modified variants of this protein: one fitted and one private loop protection. This allowed them to conclude that the protective loops extend to the neighboring protein.

"It gives us a better idea of the position of the loop," says Alexandra Trkola. But know this exact position is important in view of developing a preventive vaccine against AIDS. "But the path to get there is still long," warns the researcher.

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