Shots - Health Blog
10:30 am
Thu July 19, 2012

How HIV Hijacks The Immune System

Originally published on Tue July 24, 2012 3:23 pm

The road to a cure for AIDS is in sight, even if every step on the journey isn't clear yet.

One of the most promising avenues is a kind of gene therapy that would block HIV's entry into cells of the immune system. A genetic tweak could make these key cells resistant to the virus's attack.

"HIV is like a jack-in-the-box," says Sriram Subramaniam, a biophysicist at the National Cancer Institute who peers at HIV with electron microscopes.

The virus's genetic material sits inside a shell that is studded with spikes. To infect a cell, the shell has to pop open and release the virus's genes into the cell.

That's what happens when HIV bumps into T cells, the white blood cells that are the virus's prime targets.

T cells are studded with finger-like projections, including one called CCR5 that fits on HIV's spikes.

A gene therapy now being tested in people takes the CCR5 receptor out of their T cells. Without CCR5, the cells don't trigger the virus's jack-in-the-box invasion. If the virus can't get inside the cells, it can't reproduce.

A few people, mainly Caucasians, lack CCR5 because of genetic mutations. And one man who received bone marrow transplants for leukemia from a donor without CCR5 receptors has been cured of HIV/AIDS, his doctors say.

Separately, Subramaniam has found evidence that HIV hide in other places in the immune system even before it enters cells.

Using a microscopy technique to create 3-D models of cell surfaces, he and his team saw some immune cells took on flower-like shapes. HIV can hide in crevices between the large petal-like sheets.

These pools of HIV may help the virus's move around the immune system, Subramaniam tells Shots.

The virus gets a free ride as these cells move through the blood. "T cells can reach deep into these channels to pick up the HIV itself," says Subramaniam.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.