Snapshot Issue 4 October 2004

PSC-RANTES protein

Are condoms moving into the back seat? Well they have been for the past few decades some of you may answer…Yes, but this is not about birth control. It is about HIV infection. There are chances that a protein could replace the familiar film of latex to protect us against AIDS.

A protein? Yes. And a synthetic one. Indeed PSC-RANTES was created from scratch in a laboratory at the University of Geneva. Well, not quite from scratch. There was a template: RANTES, a human protein which is produced in small quantities in our body. In the event of infection, RANTES stimulates white cells by binding to a receptor – CCR5 – on the cell membrane. In 1996, it was discovered that HIV also uses the CCR5 receptor to infect the cells involved in our immune system. In effect, CCR5 and RANTES race for the same receptor. When RANTES gets there first, HIV cannot infect the cell.

However, despite this natural barrier, RANTES isn’t quite tough enough to fight off HIV infection altogether. So, in 1997, Prof. Robin Offord, Dr Oliver Hartley and their team from the Department of Structural Biology and Bioinformatics in Geneva decided to tinker with the protein’s structure in an attempt to make it more effective against infection. Seven years later, they achieved their goal. How? By introducing chemical modifications to only three amino acids in the original protein sequence.

PSC-RANTES can block HIV infection. To date, however, tests have only been performed on macaques. And macaques are not men. Or women, should we say. The idea is to use PSC-RANTES as a microbicide, in the form of a kind of cream, which could be directly applied to the woman’s vagina. Commercializing such a product, as well as making it freely available to all, would shift women into a position where they would have some control at least over their health, when their partners shun the use of condoms during sexual intercourse. What is more, condoms do tend to be effective against making babies and this kind of cream could protect against infection whilst permitting procreation.

It is not difficult to imagine how precious such a microbicide could be in the Third World, where HIV infection is in dire need of being checked and where women don’t always have their say. What is more, PSC-RANTES is proving to be incredibly powerful. If only a few drops were added to a volume of water the size of an Olympic pool, the solution could stop HIV infection of cells placed in a test tube! As a consequence, if the same microbicidal power can be achieved in humans the cost of such a product would be piffling.

So are condoms doomed? No, naturally. Nothing yet can replace latex in the fight against sexually transmitted diseases or undesired offspring.

T-cell specific RANTES protein, Homo sapiens (Human): P13501

L'édition française de cette chronique est disponible dans l'Instantanés du mois de Prolune.

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