Neurological problems
Neurological problems are another common complication of HIV infection, because infected cells can easily enter the brain and the peripheral nervous system. In fact, at least 25% of people with HIV infections develop neurological complications. At one time AIDS-related dementia was an almost inevitable consequence of HIV infection. Although antiretroviral therapy has cut the rate of serious dementia, other problems are emerging, notes AHFMR Senior Scholar Dr. Chris Power, an Edmonton neurologist and AIDS researcher at the University of Alberta.
"We've gone from a situation where patients were all dying to a situation where patients have a chronic disease that is horrible, but are living longer and with a better quality of life," he says. "But as they live longer, we're now treating different neurological problems."
One of these problems is nerve damage known as peripheral neuropathy. The condition can manifest itself as a feeling of pins and needles, unexplained pain, burning, stiffness, or numbness in the feet and toes. Dr. Power says that severe cases of neuropathy are "exquisitely painful and disruptive to quality of life." Another condition that has emerged with the advent of antiretroviral therapy is neurological immune reconstitution inflammatory syndrome (IRIS). This is an autoimmune disease that causes people to get sicker even though the antiretroviral therapy has improved their immune function. It is the subject of a great deal of current research.
In Dr. Power's lab, the focus is on understanding how HIV gets into the brain and damages brain cells. His team has found that HIV activates an enzyme known as MMP-2, which in turn alters a usually beneficial molecule in such a way that it starts killing brain cells. Dr. Power first identified the process in 2003, and has since done a series of studies on MMP-2. "To prevent neural injury, we need to find some way of suppressing the enzyme or blocking the receptor. That's the goal of the research," he says.
"As a physician, I can see the benefits of being able to do this. Right now, we can prevent some of the neurological complications of HIV infection as long as patients begin antiretroviral therapy at an early stage. But for patients who are late presenters to medical care, antiretroviral therapy isn't as effective. And this is a major, growing group of people, especially in sub-Saharan Africa. The bottom line is that we need better medicines and an effective vaccine for HIV."