March 12, 2012
HIV Cure Not Imminent But Progress Continues
The human immunodeficiency virus (HIV) is a complex creature that researchers have been working on getting the upper hand on for 30 years. It appears, however, that scientists are finally making real progress on several fronts in the search for a cure for HIV infections.
Early human trials of vaccines designed to prevent or treat infection with the difficult to target virus have proved disappointing. HIV is a “provirus” that is integrated into the DNA of a host cell, where it can remain latent or eventually reactivate.
“It has proven to be an incredibly formidable challenge to develop a vaccine,” said John Coffin, professor of molecular biology at Tufts University in Boston. “In recent years the pendulum is swinging back.”
Researchers are flushing hidden HIV from cells and changing out a person´s own immune system cells, making them resistant to HIV and then putting them back into the patient´s body, writes Deena Beasley for Reuters.
HIV, unfortunately, is especially resistant treatments and procedures. It lies low in pools or reservoirs of latent infection that even powerful drugs cannot reach, scientists told the Conference on Retroviruses and Opportunistic Infections, one of the world´s largest scientific meetings on HIV/AIDS.
Dr. Kevin De Cock, director of the Center for Global Health at the US Centers for Disease Control and Prevention, says, “We need to get the virus to come out of the latent state, then rely on the immune system or some other treatment to kill the virus.”
The virus infects more than 33 million people worldwide and thanks to prevention measures and tests that detect HIV early, infection with the virus that causes AIDS is no longer the death sentence it used to be.
Antiviral drugs and treatments are expensive and questions of side effects, drug resistance and ultimate lifespan, make lifelong use of antiviral drugs a less-than-ideal solution. Scientific advances in molecular engineering, however, are allowing researchers to reconstruct the basic building blocks of HIV.
“Vaccines work by recognizing the surface of the virus and eliminating it,” said Dr. Dennis Burton, professor of immunology and microbial science at the Scripps Research Institute in La Jolla, California. “HIV is a highly evolved virus that has developed a surface incorporating features to avoid antibody responses,” including instability.
He presented research showing that “broadly neutralizing antibodies” can be designed to recognize and penetrate HIV, giving researchers new vaccine targets.
Phillip Gregory, chief scientific officer at Sangamo BioSciences explained that because HIV is a “reverse transcriptase” virus it is constantly mutating, making it very difficult for the body´s immune system to keep up.
Vaccines induce the production of antibodies that recognize and bind to very specific viral surface molecules, but the HIV molecules end up with a variety of subtle molecular differences on their surface.
“Eradication is a very tough theoretical sell,” Gregory continued. “What´s going to work is getting to the point that we could reasonably expect the immune system to get it totally under control.”
Sangamo is conducting two gene therapy trials in which infection-fighting white blood cells known as CD4 cells are removed, manipulated to knock out the CCR5 gene used by HIV to infect cells and then replaced.
“The change is permanent. Those cells and their progeny will go on to carry that genetic change,” said Geoffrey Nichol, head of research and development at Sangamo.
An earlier study of a single infusion of the gene therapy in six HIV-infected patients showed mixed results, eliminating the virus in one patient with a naturally occurring gene mutation.
On the Net:
- Conference on Retroviruses and Opportunistic Infections
- Centers for Disease Control
- Scripps Research Institute