HIV/AIDS: don’t put the cART before the horse
Dr. Chris Power’s research could help prevent neurological disorders in people with HIV/AIDS.
Story by Tara Narwani/Illustration by Genevieve Simms
“We could easily be lulled into a false sense of security that we’re dealing with this disease adequately when indeed we’re not. The disease continues to march on. People continue to die,” says Dr. Chris Power, a neurologist at the University of Alberta.
Dr. Power is referring to acquired immune deficiency syndrome (AIDS), a disease that is caused by the human immunodeficiency virus (HIV) and that afflicts about 65,000 people in Canada. In the past, a diagnosis of AIDS was a death sentence. But the introduction of combination antiretroviral therapy (cART) in 1996 was literally a lifesaver.
The cART treatment approach uses three or more drugs to keep the level of the HIV in the body low. “cART made HIV/AIDS go from a disease that was uniformly fatal to one that was chronic,” explains Dr. Power, “albeit a disease with a lot of associated problems.”
Some of these associated problems have been a focus of Dr. Power’s research for more than a decade. He is particularly interested in the effect of HIV on neurologic disorders, which are often overlooked when people with HIV/AIDS seek treatment for acute medical problems.
The fact that HIV can cause neurologic disorders isn’t a surprise. HIV is a member of a group of viruses called lentiviruses that are known to infect the nervous system and cause damage to the brain. “This damage has a number of neurologic manifestations like difficulty walking or difficulty with memory,” says Dr. Power.
In 1998, Dr. Power joined the Southern Alberta Clinic (SAC) in Calgary, which gave him a unique opportunity to look at how widespread and frequent the occurrence of neurologic disorders is in people with HIV/AIDS being treated with cART.
The SAC provided the ideal conditions to run this kind of study. It would have been significantly more difficult to implement the same study in the United States or in other jurisdictions in Canada. As a centralized medical clinic, SAC sees all HIV-positive individuals seeking medical attention in southern Alberta, a region of 1.5 million people. As a result, medical statistics collected at the clinic reflect a wide population of patients and allow researchers to draw broader conclusions about their results.
Another important factor is that, according to Dr. Power, people want to come to the clinic because it is located in downtown Calgary and isn’t in a hospital setting. Dr. John Gill, the medical director of the SAC and Dr. Power’s collaborator on the study, has ensured that the clinic is a patient-focused operation with a variety of medical professionals, such as psychiatrists and dietitians, working on site. Given the positive environment, individuals establish a long-term relationship with the clinic, allowing the physicians to monitor the health of their patients over many years.
This past fall, Dr. Power and his colleagues published their results in the journal Neurology after 10 years of research on the neurologic disorders in HIV-infected people who were receiving active care in the period after the introduction of cART. At the beginning of the work, Dr. Power expected that, with the advent of antiretroviral therapy, “neurologic disease—if driven by the virus—would diminish and perhaps be nonexistent over time.”
The results were surprising. What they saw instead was a significant amount of neurologic disease in their HIV-infected patients. Twenty percent of HIV-positive patients exhibited symptoms of at least one neurologic disorder. The numbers rose to 40% of AIDS patients—those individuals whose disease has progressed further. The range of neurologic disorders included dementia, seizures, infections of the central nervous system, nerve pain, and movement problems.
“It’s a substantial burden of disease. A lot of these people can’t return to work,” explains Dr. Power.
Another discouraging result was that people with HIV/AIDS and a neurologic disorder were twice as likely to die compared with those who didn’t exhibit neurologic disease and were more than 10 times likely to die than a member of the general Canadian population.
The study’s conclusions certainly have implications for the future of cART. According to Dr. Power, research is required on a number of fronts. To prevent HIV from reproducing in the central nervous system and causing these disorders, researchers need to identify which of the available antiretroviral drugs can enter the nervous system most efficiently. Next, drugs designed to cross the blood–brain barrier and directly access the brain are likely necessary. Finally, new approaches to treatment that go beyond conventional drug development should be considered.
Dr. Power is optimistic. In his lab, they’re “looking at ways to actively redirect the immune system, to improve the body’s immune response, and protect the brain.”