Caption: A decoy protein that mimics the CD4 receptor (red), the CCR5 receptor (green), and a natural antibody (grey), binds to the HIV envelope protein (three white blobs) and blocks it from infecting immune cells.
Credit: Michael Farzan
Over more than a century, researchers have succeeded in developing vaccines to prevent polio, smallpox, cervical cancer, and many other viral diseases. For three decades now, they have tried to design an effective vaccine for the human immunodeficiency virus (HIV) that causes AIDS. Despite plenty of hard work, lots of great science, and some promising advances along the way, an effective traditional vaccine still remains elusive. That has encouraged consideration of alternative approaches to block HIV infection.
Now in the journal Nature , an NIH-funded team reports promising early results with one of these interesting alternatives. The team hypothesized that producing a protein that binds to HIV and prevents it from entering cells might provide protection. So they designed such a protein, and, using an animal model, introduced multiple copies of a gene that makes this protein. In a small study of non-human primates, this gene-therapy approach blocked HIV infection, even when the animals were exposed repeatedly to large doses of the virus.
Traditional vaccines work by acquainting the immune system with a non-infectious piece of a virus or a deactivated version of the entire thing. This forced introduction primes our immune systems to recognize live virus later, should an infection ever occur, and to knock out the invaders with proteins called antibodies.
But HIV has turned out to be a diabolical moving target that mutates constantly and subtly changes the shape of its coat proteins.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.