Gene therapy to treat HIV patients

One of the more interesting developments I learned about at the recent Till-McCulloch conference is a novel gene therapy with great promise for HIV patients.

Calimmune, based in Tucson, Arizona, is currently in a Phase I clinical trial to test safety of the procedure, and while the company is holding comment until more data become available, their approach to blocking the HIV virus looks fascinating.

HIV affects over 30 million people worldwide (over 1.2 million in the U.S.), and while there is no cure yet, there are various drug treatments to contain the virus, which attacks the immune system.

Antiretroviral treatments consist of so-called cocktails of chemicals that mainly attack the virus’s ability to replicate in the bloodstream. They have to be taken daily and can have short term and long term side effects.

But what if there were a means of rendering the virus harmless by altering the accessibility of the patient’s own white blood cells? That’s the goal of Calimmune’s treatment, called Cal-1.

HIV attacks the immune system by destroying CD4+ T-lymphocytes, subsets of white blood cells that are crucial to the health of the immune system. A key landing point for the virus is the CCR5 receptor on the outer surface of these white blood cells.

Cal-1 is designed to block the virus by preventing it from binding to CCR5. It achieves this by replacing the CCR5 receptor with a natural variant of the protein found only in the very small percentage of people that are born resistant to HIV.

How it works in broad strokes: The patient’s own blood is drawn and the Cal-1 is introduced into the hematopoietic progenitor/stem cells and the mature CD4+ T lymphocyte populations of white blood cells. The T cells with altered CCR5 will naturally proliferate and outnumber the T cells infected with HIV once they are returned to the patient’s circulation.

By John Farrell